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Nanomaterials
Volume 8
Issue 5
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Nanomaterials, Volume 8, Issue 5 (May 2018) – 86 articles

Cover Story (view full-size image): Inorganic nanoparticle systems with an optimized coating and multifunctional character boost personalized nanomedical treatments. The directed assembly of iron-oxide-interacting nanocrystals into cluster-like entities seems to improve their features in magnetically-driven diagnosis and possible therapy. The optimization of their effectiveness in practical healthcare includes the study of nanocluster interactions with cells and their correlation to external stimuli. The unexplored bioactivity of these nanoprobes may become a useful tool for immune system theranostics (diagnosis and therapy). View this paper.
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19 pages, 6824 KiB  
Article
Properties of Ferrite Garnet (Bi, Lu, Y)3(Fe, Ga)5O12 Thin Film Materials Prepared by RF Magnetron Sputtering
by Mohammad Nur-E-Alam, Mikhail Vasiliev, Vladimir Belotelov and Kamal Alameh
Nanomaterials 2018, 8(5), 355; https://doi.org/10.3390/nano8050355 - 22 May 2018
Cited by 23 | Viewed by 7123
Abstract
This work is devoted to physical vapor deposition synthesis, and characterisation of bismuth and lutetium-substituted ferrite-garnet thin-film materials for magneto-optic (MO) applications. The properties of garnet thin films sputtered using a target of nominal composition type Bi0.9Lu1.85Y0.25Fe [...] Read more.
This work is devoted to physical vapor deposition synthesis, and characterisation of bismuth and lutetium-substituted ferrite-garnet thin-film materials for magneto-optic (MO) applications. The properties of garnet thin films sputtered using a target of nominal composition type Bi0.9Lu1.85Y0.25Fe4.0Ga1O12 are studied. By measuring the optical transmission spectra at room temperature, the optical constants and the accurate film thicknesses can be evaluated using Swanepoel’s envelope method. The refractive index data are found to be matching very closely to these derived from Cauchy’s dispersion formula for the entire spectral range between 300 and 2500 nm. The optical absorption coefficient and the extinction coefficient data are studied for both the as-deposited and annealed garnet thin-film samples. A new approach is applied to accurately derive the optical constants data simultaneously with the physical layer thickness, using a combination approach employing custom-built spectrum-fitting software in conjunction with Swanepoel’s envelope method. MO properties, such as specific Faraday rotation, MO figure of merit and MO swing factor are also investigated for several annealed garnet-phase films. Full article
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Figure 1

Figure 1
<p>Schematic diagram of annealing process optimization experiments conducted to find the most suitable annealing regimes (in terms of both the maximum process temperature and crystallization process duration) for this type of garnet layers.</p> Full article ">Figure 2
<p>X-ray diffractograms of as-deposited and annealed garnet layers.</p> Full article ">Figure 3
<p>A typical energy dispersive X-ray (EDS) spectrum of a garnet (as-deposited) sample with the characteristics peaks for each possible element present in the film. The inset shows the obtained constituent elements (atomic %) in the sample. To avoid any type of contamination such as by carbon or other substances/gases, the measurement time was limited (at 5 min maximum) according to the manufacturer recommendations provided in the system manual. Cps: counts per second.</p> Full article ">Figure 4
<p>Measured transmission spectra of as-deposited and annealed garnet samples of about 701 nm (<b>a</b>), and (<b>b</b>) 1272 nm thickness. The insets of the figures showed the shift in the absorption edge to lower wavelengths due to the annealing crystallization process. The shift of the band gap due to the annealing process attributed to remove the residual stresses of the garnet layers and improved the structural and crystalline quality of the annealed garnet films.</p> Full article ">Figure 5
<p>Typical transmission spectrum for the as-deposited garnet sample; where T<sub>exp</sub> is the measured transmission of the sample, T<sub>M</sub> and T<sub>m</sub> are the maxima and minima of the envelopes. Transmission spectrum of 1 mm thick glass substrate is also included in the figure.</p> Full article ">Figure 6
<p>Plots of (l/2) versus (n/λ) to determine the physical film thickness and the first-order value m<sub>1</sub> for as-deposited and annealed garnet thin films, according to the modified Equation (8). Film thickness (<b>a</b>) 701 nm, and (<b>b</b>) 1272 nm.</p> Full article ">Figure 7
<p>Least square fit of calculated refractive index (n<sub>2</sub>) values for garnet samples (batch-1); (<b>a</b>) as-deposited and (<b>b</b>) annealed. (<b>c</b>) Calculated refractive index spectra using Cauchy’s model and measured transmission spectra, for as-deposited and annealed samples.</p> Full article ">Figure 8
<p>Least square fit of calculated refractive index (n<sub>2</sub>) values for garnet samples (batch-2); (<b>a</b>) as-deposited and (<b>b</b>) annealed. (<b>c</b>) Calculated refractive index spectra using Cauchy’s model and measured transmission spectra, for as-deposited and annealed samples.</p> Full article ">Figure 9
<p>Iterative software-assisted fitting of modelled and measured transmission spectra (<b>a</b>), and (<b>b</b>) the derived absorption coefficient (α) of an as-deposited garnet sample grown on glass substrate from batch-1.</p> Full article ">Figure 10
<p>Magneto-photonic crystal (MPC) software fitted transmission spectra of different thin film garnet layers; (<b>a</b>) annealed garnet sample from batch-1, (<b>b</b>,<b>c</b>) as-deposited and annealed garnet samples form batch-2, (<b>d</b>) derived absorption coefficient datasets obtained for the as-deposited and annealed garnet samples.</p> Full article ">Figure 10 Cont.
<p>Magneto-photonic crystal (MPC) software fitted transmission spectra of different thin film garnet layers; (<b>a</b>) annealed garnet sample from batch-1, (<b>b</b>,<b>c</b>) as-deposited and annealed garnet samples form batch-2, (<b>d</b>) derived absorption coefficient datasets obtained for the as-deposited and annealed garnet samples.</p> Full article ">Figure 11
<p>Spectral dependence of the extinction coefficient for as-deposited and annealed garnet samples (batch 1 and 2).</p> Full article ">Figure 12
<p>Measured specific Faraday rotation data and magneto-optic (MO) figures of merit at 473 nm, 532 and 635 nm.</p> Full article ">Figure 13
<p>Measured swing factor of photo-response (Q<sub>S</sub>) data points at 473 nm, 532 and 635 nm are presented against the Q<sub>S</sub> values of a 530 nm BIG/GGG film. The Q<sub>S</sub> values for the Bismuth iron garnet film (Bi<sub>3</sub>Fe<sub>5</sub>O<sub>12</sub>) on Gadolinium Gallium garnet substrate ((Gd<sub>3</sub>Gd<sub>5</sub>O<sub>12</sub>) (BIG/GGG) film are reproduced digitally from the published result in Ref. [<a href="#B44-nanomaterials-08-00355" class="html-bibr">44</a>].</p> Full article ">Figure 14
<p>Measured hysteresis loop of Faraday rotation at 532 nm of a 1.272 µm thick annealed garnet sample.</p> Full article ">
11 pages, 3622 KiB  
Article
The Influence of Shape on the Output Potential of ZnO Nanostructures: Sensitivity to Parallel versus Perpendicular Forces
by José Cardoso, Filipe F. Oliveira, Mariana P. Proenca and João Ventura
Nanomaterials 2018, 8(5), 354; https://doi.org/10.3390/nano8050354 - 22 May 2018
Cited by 8 | Viewed by 4110
Abstract
With the consistent shrinking of devices, micro-systems are, nowadays, widely used in areas such as biomedics, electronics, automobiles, and measurement devices. As devices shrunk, so too did their energy consumptions, opening the way for the use of nanogenerators (NGs) as power sources. In [...] Read more.
With the consistent shrinking of devices, micro-systems are, nowadays, widely used in areas such as biomedics, electronics, automobiles, and measurement devices. As devices shrunk, so too did their energy consumptions, opening the way for the use of nanogenerators (NGs) as power sources. In particular, to harvest energy from an object’s motion (mechanical vibrations, torsional forces, or pressure), present NGs are mainly composed of piezoelectric materials in which, upon an applied compressive or strain force, an electrical field is produced that can be used to power a device. The focus of this work is to simulate the piezoelectric effect in different ZnO nanostructures to optimize the output potential generated by a nanodevice. In these simulations, cylindrical nanowires, nanomushrooms, and nanotrees were created, and the influence of the nanostructures’ shape on the output potential was studied as a function of applied parallel and perpendicular forces. The obtained results demonstrated that the output potential is linearly proportional to the applied force and that perpendicular forces are more efficient in all structures. However, nanotrees were found to have an increased sensitivity to parallel applied forces, which resulted in a large enhancement of the output efficiency. These results could then open a new path to increase the efficiency of piezoelectric nanogenerators. Full article
(This article belongs to the Special Issue 1D Nanostructure-Based Piezo-Generators)
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Figure 1

Figure 1
<p>Nanowire structural deflection and corresponding piezoelectric potential when applying (<b>a</b>) <span class="html-italic">F</span><sub>x</sub>, and (<b>b</b>) <span class="html-italic">F</span><sub>z</sub>, on the top surface. The <span class="html-italic">c</span>-axis is directed along the long nanowire direction. (<b>c</b>) Resulting piezoelectric output potentials as a function of the total applied force along the <span class="html-italic">x</span>-, <span class="html-italic">y</span>-, and <span class="html-italic">z</span>-directions. A color scale in Volts shows the potential distribution on the nanowire. (<b>d</b>) Calculated stress for a force applied along the <span class="html-italic">x</span>-direction.</p> Full article ">Figure 2
<p>Nanomushroom structural deflection and corresponding piezoelectric potential when applying (<b>a</b>) <span class="html-italic">F</span><sub>x</sub>, and (<b>b</b>) <span class="html-italic">F</span><sub>z</sub>, on the top surface. The <span class="html-italic">c</span>-axis is directed along the long nanowire direction. Inset of (<b>b</b>) shows the calculated stress for a force applied along the <span class="html-italic">x</span>-direction. (<b>c</b>,<b>d</b>) Resulting piezoelectric output potentials as a function of the total applied force along the <span class="html-italic">x</span>-, <span class="html-italic">y</span>-, and <span class="html-italic">z</span>-directions for (<b>c</b>) probe 1 and (<b>d</b>) probe 2. The location of the measurement probes 1 and 2 are represented in (<b>a</b>). A color scale in Volts shows the piezoelectric potential distribution on the structure.</p> Full article ">Figure 3
<p>Nanotree structural deflection and corresponding piezoelectric potential when applying (<b>a</b>) <span class="html-italic">F</span><sub>x</sub>, and (<b>b</b>) <span class="html-italic">F</span><sub>z</sub>, on the top surface. Inset shows the calculated stress for a force applied along the <span class="html-italic">x</span>-direction. The <span class="html-italic">c</span>-axis is directed along the long nanowire direction of each tree branch. Resulting piezoelectric output potentials as a function of the total applied force along the <span class="html-italic">x</span>-, <span class="html-italic">y</span>- and <span class="html-italic">z</span>-directions for (<b>c</b>) probe 1, (<b>d</b>) probe 2, and (<b>e</b>) probe 3, respectively. The location of the measurement probes 1, 2, and 3 are represented in (<b>a</b>). A color scale in Volts shows the piezoelectric potential distribution on the structure.</p> Full article ">Figure 4
<p>Piezoelectric potential maximum values for nanowire, nanomushroom and nanotree structures applied along the <span class="html-italic">x</span>-, <span class="html-italic">y</span>-, and <span class="html-italic">z</span>-axis.</p> Full article ">
18 pages, 5572 KiB  
Article
Enhanced Catalytic Reduction of 4-Nitrophenol Driven by Fe3O4-Au Magnetic Nanocomposite Interface Engineering: From Facile Preparation to Recyclable Application
by Yue Chen, Yuanyuan Zhang, Qiangwei Kou, Yang Liu, Donglai Han, Dandan Wang, Yantao Sun, Yongjun Zhang, Yaxin Wang, Ziyang Lu, Lei Chen, Jinghai Yang and Scott Guozhong Xing
Nanomaterials 2018, 8(5), 353; https://doi.org/10.3390/nano8050353 - 22 May 2018
Cited by 63 | Viewed by 7298
Abstract
In this work, we report the enhanced catalytic reduction of 4-nitrophenol driven by Fe3O4-Au magnetic nanocomposite interface engineering. A facile solvothermal method is employed for Fe3O4 hollow microspheres and Fe3O4-Au magnetic nanocomposite [...] Read more.
In this work, we report the enhanced catalytic reduction of 4-nitrophenol driven by Fe3O4-Au magnetic nanocomposite interface engineering. A facile solvothermal method is employed for Fe3O4 hollow microspheres and Fe3O4-Au magnetic nanocomposite synthesis via a seed deposition process. Complementary structural, chemical composition and valence state studies validate that the as-obtained samples are formed in a pure magnetite phase. A series of characterizations including conventional scanning/transmission electron microscopy (SEM/TEM), Mössbauer spectroscopy, magnetic testing and elemental mapping is conducted to unveil the structural and physical characteristics of the developed Fe3O4-Au magnetic nanocomposites. By adjusting the quantity of Au seeds coating on the polyethyleneimine-dithiocarbamates (PEI-DTC)-modified surfaces of Fe3O4 hollow microspheres, the correlation between the amount of Au seeds and the catalytic ability of Fe3O4-Au magnetic nanocomposites for 4-nitrophenol (4-NP) is investigated systematically. Importantly, bearing remarkable recyclable features, our developed Fe3O4-Au magnetic nanocomposites can be readily separated with a magnet. Such Fe3O4-Au magnetic nanocomposites shine the light on highly efficient catalysts for 4-NP reduction at the mass production level. Full article
(This article belongs to the Special Issue Alleviating Climate Change and Pollution with Nanomaterials)
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Figure 1

Figure 1
<p>Schematic illustration of the fabrication process and catalytic application to 4-nitrophenol (4-NP) of Fe<sub>3</sub>O<sub>4</sub>-Au magnetic nanocomposites. PEI-DTC, polyethyleneimine-dithiocarbamate.</p> Full article ">Figure 2
<p>XRD patterns of the as-prepared pure Fe<sub>3</sub>O<sub>4</sub> hollow microspheres and Fe<sub>3</sub>O<sub>4</sub>-Au magnetic nanocomposites with the different addition quantities of the gold seed colloids (Fe<sub>3</sub>O<sub>4</sub>-Au 5 mL, Fe<sub>3</sub>O<sub>4</sub>-Au 20 mL, Fe<sub>3</sub>O<sub>4</sub>-Au 40 mL and Fe<sub>3</sub>O<sub>4</sub>-Au 60 mL) (<b>a</b>); Mössbauer spectra of pure Fe<sub>3</sub>O<sub>4</sub> hollow microsphere (<b>b</b>).</p> Full article ">Figure 3
<p>SEM images (<b>a</b>) and TEM images (<b>b</b>) of pure Fe<sub>3</sub>O<sub>4</sub> hollow microspheres.</p> Full article ">Figure 4
<p>TEM images of Fe<sub>3</sub>O<sub>4</sub>-Au 5 mL (<b>a</b>) and Fe<sub>3</sub>O<sub>4</sub>-Au 20 mL with the HRTEM image (inset) (<b>b</b>); Fe<sub>3</sub>O<sub>4</sub>-Au 40 mL with the SAED pattern (inset) (<b>c</b>) and Fe<sub>3</sub>O<sub>4</sub>-Au 60 mL (<b>d</b>); TEM images of single Fe<sub>3</sub>O<sub>4</sub>-Au 5 mL (<b>e</b>) and Fe<sub>3</sub>O<sub>4</sub>-Au 60 mL (<b>f</b>) microspheres and corresponding EDS elemental mapping images (Au, Fe and O).</p> Full article ">Figure 5
<p>UV-Vis absorption spectra of pure Fe<sub>3</sub>O<sub>4</sub> hollow microspheres, Au seed colloids, Fe<sub>3</sub>O<sub>4</sub>-Au 5 mL, Fe<sub>3</sub>O<sub>4</sub>-Au 20 mL, Fe<sub>3</sub>O<sub>4</sub>-Au 40 mL and Fe<sub>3</sub>O<sub>4</sub>-Au 60 mL magnetic nanocomposites.</p> Full article ">Figure 6
<p>XPS spectra of the as-obtained Fe<sub>3</sub>O<sub>4</sub>, Fe<sub>3</sub>O<sub>4</sub>-Au 5 mL, Fe<sub>3</sub>O<sub>4</sub>-Au 20 mL, Fe<sub>3</sub>O<sub>4</sub>-Au 40 mL and Fe<sub>3</sub>O<sub>4</sub>-Au 60 mL: the Fe 2p binding energies (<b>a</b>); the Au 4f binding energies (<b>b</b>); the O1s binding energies (<b>c</b>) and XPS survey spectra (<b>d</b>).</p> Full article ">Figure 7
<p>Magnetic hysteresis (M-H) loops of Fe<sub>3</sub>O<sub>4</sub>, Fe<sub>3</sub>O<sub>4</sub>-Au 5 mL, Fe<sub>3</sub>O<sub>4</sub>-Au 20 mL, Fe<sub>3</sub>O<sub>4</sub>-Au 40 mL and Fe<sub>3</sub>O<sub>4</sub>-Au 60 mL. The inset is the photograph of pure Fe<sub>3</sub>O<sub>4</sub> hollow microspheres and Fe<sub>3</sub>O<sub>4</sub>-Au 60 mL magnetic nanocomposites in deionized water after using a magnet.</p> Full article ">Figure 8
<p>UV-Vis absorption spectra of 4-NP after reduction catalyzed by Fe<sub>3</sub>O<sub>4</sub>-Au 5 mL (<b>a</b>); Fe<sub>3</sub>O<sub>4</sub>-Au 20 mL (<b>b</b>); Fe<sub>3</sub>O<sub>4</sub>-Au 40 mL (<b>c</b>) and Fe<sub>3</sub>O<sub>4</sub>-Au 60 mL (<b>d</b>).</p> Full article ">Figure 9
<p>Plots of ln(C/C<sub>0</sub>) against reaction time: Fe<sub>3</sub>O<sub>4</sub>-Au 5 mL (<b>a</b>); Fe<sub>3</sub>O<sub>4</sub>-Au 20 mL (<b>b</b>); Fe<sub>3</sub>O<sub>4</sub>-Au 40 mL (<b>c</b>) and Fe<sub>3</sub>O<sub>4</sub>-Au 60 mL (<b>d</b>).</p> Full article ">Figure 10
<p>Reusability of Fe<sub>3</sub>O<sub>4</sub>-Au 5 mL (<b>a</b>); Fe<sub>3</sub>O<sub>4</sub>-Au 20 mL (<b>b</b>); Fe<sub>3</sub>O<sub>4</sub>-Au 40 mL (<b>c</b>) and Fe<sub>3</sub>O<sub>4</sub>-Au 60 mL (<b>d</b>) for catalytic reduction of 4-NP.</p> Full article ">
14 pages, 32769 KiB  
Article
Fabrication Flexible and Luminescent Nanofibrillated Cellulose Films with Modified SrAl2O4: Eu, Dy Phosphors via Nanoscale Silica and Aminosilane
by Longfei Zhang, Shaoyi Lyu, Zhilin Chen and Siqun Wang
Nanomaterials 2018, 8(5), 352; https://doi.org/10.3390/nano8050352 - 22 May 2018
Cited by 30 | Viewed by 5737
Abstract
Flexible 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized nanofibrillated cellulose (ONFC) films with long afterglow luminescence containing modified SrAl2O4: Eu2+, Dy3+ (SAOED) phosphors were fabricated by a template method. Tetraethyl orthosilicate (TEOS) and (3-aminopropyl) trimethoxy-silane (APTMS) were employed cooperatively to [...] Read more.
Flexible 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized nanofibrillated cellulose (ONFC) films with long afterglow luminescence containing modified SrAl2O4: Eu2+, Dy3+ (SAOED) phosphors were fabricated by a template method. Tetraethyl orthosilicate (TEOS) and (3-aminopropyl) trimethoxy-silane (APTMS) were employed cooperatively to improve the water resistance and compatibility of the SAOED particles in the ONFC suspension. The structure and morphology after modification evidenced the formation of a superior SiO2 layer and coarse amino-compounds on the surface of the phosphors. Homogeneous dispersions containing ONFC and the modified phosphors were prepared and the interface of composite films containing the amino-modified particles showed a more closely packed structure and had less voids at the interface between the cellulose and luminescent particles than that of silica-modified phosphors. The emission spectra for luminescent films showed a slight blue shift (3.2 nm) at around 512 nm. Such flexible films with good luminescence, thermal resistance, and mechanical properties can find applications in fields like luminous flexible equipment, night indication, and portable logo or labels. Full article
(This article belongs to the Special Issue Cellulose Nanomaterials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Scanning electron microscopy (SEM) micrographs, transmission electron microscopy (TEM) images and the distribution of average particle size of SAOED particles before and after modification: (<b>a</b>) uncoated SAOED phosphor; (<b>b</b>) SiO<sub>2</sub> coated SAOED (SiO<sub>2</sub>@SAOED); (<b>c</b>) (3-aminopropyl) trimethoxy-silane (APTMS) coated SiO<sub>2</sub>@SAOED phosphors (NH<sub>2</sub>@SiO<sub>2</sub>@SAOED).</p> Full article ">Figure 2
<p>Chemical characteristics of SAOED phosphors before and after surface modification: (<b>a</b>) Fourier transform infrared (FTIR) spectra of SAOED, SiO<sub>2</sub>@SAOED, and NH<sub>2</sub>@SiO<sub>2</sub>@SAOED; (<b>b</b>) FTIR spectra of SAOED and pure APTMS-modified phosphors (NH<sub>2</sub>@SAOED) after immersion in water for different time; (<b>c</b>) pH values of different phosphor particle aqueous suspensions with different immersion time; (<b>d</b>) X-ray photoelectron spectroscopy (XPS) wide scan spectra of SAOED, SiO<sub>2</sub>@SAOED and NH<sub>2</sub>@SiO<sub>2</sub>@SAOED; (<b>e</b>) X-ray diffraction patterns for SAOED, SiO<sub>2</sub>@SAOED, NH<sub>2</sub>@SiO<sub>2</sub>@SAOED and control SiO<sub>2</sub> particles; (<b>f</b>) Zeta potentials of modified particles comparing with ONFC in aqueous suspensions.</p> Full article ">Figure 3
<p>Quantitative analysis of silica and amino-silane on the surface of luminescent particles: energy dispersive analysis (EDS) of (<b>a</b>) SiO<sub>2</sub>@SAOED, and (<b>b</b>) NH<sub>2</sub>@SiO<sub>2</sub>@SAOED particles; (<b>c</b>) Thermogravimetry (TG) and (<b>d</b>) Differential thermal gravimetric (DTG) analysis curves of SAOED, SiO<sub>2</sub>@SAOED, and NH<sub>2</sub>@SiO<sub>2</sub>@SAOED.</p> Full article ">Figure 4
<p>Photoluminescent (PL) spectra of SAOED phosphors and different suspensions in water and ONFC: (<b>a</b>) excitation and (<b>b</b>) emission spectra of phosphors before and after surface coated modification. Excitation wavelength λ<sub>ex</sub> = 363 nm was considered for emission spectra measurements; Digital photographs of the phosphors dispersed into distilled water (first row) and ONFC suspension (second row) for 24 h (<b>c</b>) in daylight and (<b>d</b>) in darkness.</p> Full article ">Figure 5
<p>Photoluminescent (PL) performance for the SAOED phosphors and ONFC luminescent films: (<b>a</b>) emission and (<b>b</b>) excitation spectra of ONFC luminescent films with modified phosphors (ONFC/phosphor = 1/1); (<b>c</b>) CIE chromaticity diagram of SAOED phosphors before and after modification; and ONFC luminescent films with NH<sub>2</sub>@SiO<sub>2</sub>@SAOED phosphors in 1/1 mass ratio; (<b>d</b>) X-ray diffraction patterns for ONFC film, ONFC luminescent film with SiO<sub>2</sub>@SAOED and NH<sub>2</sub>@SiO<sub>2</sub>@SAOED phosphors (mass ratio = 1/1); (<b>e</b>) Decay curve of films with NH<sub>2</sub>@SiO<sub>2</sub>@SAOED in different mass ratios (inset: digital pictures of films in 2 min under dark); (<b>f</b>) Some potential examples of luminescent logo or flexible labels in darkness (first row) and daylight (second row).</p> Full article ">Figure 6
<p>Typical micromorphology and particle dispersion of ONFC luminescent films: SEM morphologies of the surface and the cross-section of (<b>a</b>,<b>d</b>) ONFC film (inset: high magnification image of composite film); (<b>b</b>,<b>e</b>) ONFC luminescent film with SiO<sub>2</sub>@SAOED (mass ratio = 1/1); and (<b>c</b>,<b>f</b>) ONFC luminescent film with NH<sub>2</sub>@SiO<sub>2</sub>@SAOED phosphors (mass ratio = 1/1); EDS-mapping patterns of luminescent film with NH<sub>2</sub>@SiO<sub>2</sub>@SAOED phosphors after scanning the characteristic elements of (<b>g</b>) carbon; (<b>h</b>) silicon; and (<b>i</b>) strontium.</p> Full article ">Figure 7
<p>Thermal analysis and tensile strength of the ONFC luminescent films: (<b>a</b>) TG and (<b>b</b>) DTG curves of luminescent composite films with different modified SAOED phosphors (mass ratio = 1/1) compared with control ONFC film; (<b>c</b>) Stress-strain curves of tensile test results of control ONFC film, composite films with different modified SAOED phosphors (mass ratio = 1/1); (<b>d</b>) Tensile strength of ONFC/NH<sub>2</sub>@SiO<sub>2</sub>@SAOED luminescent films with different mass ratios.</p> Full article ">Scheme 1
<p>Schematic diagrams of preparing modified SrAl<sub>2</sub>O<sub>4</sub>: Eu<sup>2+</sup>, Dy<sup>3+</sup> (SAOED) phosphor particles and synthesis procedure to obtain luminescent TEMPO-oxidized nanofibrillated cellulose (ONFC) composite films.</p> Full article ">
18 pages, 4391 KiB  
Article
Electrically Guided DNA Immobilization and Multiplexed DNA Detection with Nanoporous Gold Electrodes
by Jovana Veselinovic, Zidong Li, Pallavi Daggumati and Erkin Seker
Nanomaterials 2018, 8(5), 351; https://doi.org/10.3390/nano8050351 - 21 May 2018
Cited by 21 | Viewed by 6139
Abstract
Molecular diagnostics have significantly advanced the early detection of diseases, where the electrochemical sensing of biomarkers (e.g., DNA, RNA, proteins) using multiple electrode arrays (MEAs) has shown considerable promise. Nanostructuring the electrode surface results in higher surface coverage of capture probes and more [...] Read more.
Molecular diagnostics have significantly advanced the early detection of diseases, where the electrochemical sensing of biomarkers (e.g., DNA, RNA, proteins) using multiple electrode arrays (MEAs) has shown considerable promise. Nanostructuring the electrode surface results in higher surface coverage of capture probes and more favorable orientation, as well as transport phenomena unique to nanoscale, ultimately leading to enhanced sensor performance. The central goal of this study is to investigate the influence of electrode nanostructure on electrically-guided immobilization of DNA probes for nucleic acid detection in a multiplexed format. To that end, we used nanoporous gold (np-Au) electrodes that reduced the limit of detection (LOD) for DNA targets by two orders of magnitude compared to their planar counterparts, where the LOD was further improved by an additional order of magnitude after reducing the electrode diameter. The reduced electrode diameter also made it possible to create a np-Au MEA encapsulated in a microfluidic channel. The electro-grafting reduced the necessary incubation time to immobilize DNA probes into the porous electrodes down to 10 min (25-fold reduction compared to passive immobilization) and allowed for grafting a different DNA probe sequence onto each electrode in the array. The resulting platform was successfully used for the multiplexed detection of three different biomarker genes relevant to breast cancer diagnosis. Full article
(This article belongs to the Special Issue Nanoporous Gold and Other Related Materials)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Scheme illustrating the concept of electrically-guided DNA grafting (note that the electrograms do not present actual data). (<b>A</b>) The microfluidic channel is filled with ssDNA probe 1 and a positive potential (0.8 V) is applied to electrode 1 to accelerate DNA transport and facilitate functionalization; (<b>B</b>) The channel is then filled with ssDNA probe 2 and probe 2 is grafted on electrode 2 in a similar fashion; (<b>C</b>) The device is then challenged with target DNA. Significant signal suppression is observed for the electrode with corresponding complementary probe; (<b>D</b>) No change in signal is seen on electrodes with mismatched probe-target pairs. All electrodes are functionalized and tested with both complementary and non-complementary target sequences.</p> Full article ">Figure 2
<p>Scanning electron micrographs (SEM) of np-Au electrodes that were used for testing the influence of the electrode nanostructuring on the electro-grafting probe DNA density. Top and cross-sectional images are displayed in first and second row respectively.</p> Full article ">Figure 3
<p>Effect of electrode morphology (unnanealed, annealed np-Au and pl-Au) and electro-grafting duration (1, 2, 5, 8, 10 min) on the peak current (surrogate for immobilized probe amount deducted from square wave voltammetry (SWV) measurements). SWV were taken at 18 Hz for unannealed np-Au, 30 Hz for annealed np-Au and 60 Hz for pl-Au after probe DNA immobilization (optimal frequency was determined previously [<a href="#B16-nanomaterials-08-00351" class="html-bibr">16</a>]) at 10 mV/s scan rate. In contrast to the pl-Au electrodes, the np-Au electrodes require a longer electro-grafting duration to saturate the surface, as probe DNA needs to permeate the porous structure. The curve-fits are for visual guidance only.</p> Full article ">Figure 4
<p>Comparison of DNA hybridization efficiency between macro-scale and micro-scale electrode configurations for np-Au and pl-Au electrodes. Signal suppression (%) is defined as ((<span class="html-italic">I</span><sub>probe</sub> − <span class="html-italic">I</span><sub>target</sub>)/<span class="html-italic">I</span><sub>probe</sub>) × 100, where <span class="html-italic">I</span><sub>probe</sub> and <span class="html-italic">I</span><sub>target</sub> are SWV current signals measured for probe DNA alone and upon target capture, respectively. Raw data are included in <a href="#nanomaterials-08-00351-f0A5" class="html-fig">Figure A5</a> and <a href="#nanomaterials-08-00351-f0A6" class="html-fig">Figure A6</a>.</p> Full article ">Figure 5
<p>Multiplexed detection of breast cancer-related biomarkers. Three different DNA capture probes (BRCA1, BRCA2 and p53) were grafted on three adjacent electrodes encapsulated in a microfluidic channel. SWV of the interaction of grafted probe DNA with redox marker methylene blue (MB) is measured, as well as the SWV response of each of the electrodes to the different target sequences introduced (BRCA1, BRCA2 and p53) to each microfluidic device. Significant signal suppression was observed when the sample contained the target sequence corresponding to the electrode being interrogated via SWV, while the other two electrodes showed minimal change in signal. The signal suppression observed for all electrodes in response to the targets is summarized as a bar graph.</p> Full article ">Figure A1
<p>Optical image of a np-Au multielectrode array integrated with polydimethylsiloxane (PDMS) microfluidic channels that house the micro-scale electrodes.</p> Full article ">Figure A2
<p>Schematic of (<b>A</b>) macro-scale electrochemical cell with np-Au electrode diameter of 4 mm and (<b>B</b>) microfluidic electrochemical cell with np-Au electrode diameter of 0.3 mm.</p> Full article ">Figure A3
<p>Process flow for the fabrication nanoporous gold (np-Au) multiple electrode arrays (MEAs) encapsulated with microfluidic channels. The MEAs were patterned by laser ablation of a blanket sputter-coated alloy films on glass slides. The molds for PDMS soft lithography were also fabricated by laser ablation. The np-Au MEAs were bonded to the PDMS device via oxygen plasma activation of the surfaces.</p> Full article ">Figure A4
<p>Example SWV raw data for two extreme electro-grafting times (2 and 10 min) used to generate <a href="#nanomaterials-08-00351-f003" class="html-fig">Figure 3</a>—Effect of electrode morphology (unannealed, annealed np-Au and pl-Au) and electro-grafting duration (1, 2, 5, 8, 10 min) on the peak current (surrogate for immobilized probe amount deducted from SWV measurements).</p> Full article ">Figure A5
<p>Example SWV raw data for DNA probe and DNA:DNA hybrid current signal in the microfluidic channel for unnanealed np-Au and pl-Au electrodes used to generate <a href="#nanomaterials-08-00351-f004" class="html-fig">Figure 4</a>—Comparison of DNA hybridization efficiency between macro-scale and micro-scale cell sensor configurations for np-Au and pl-Au electrodes.</p> Full article ">Figure A6
<p>Square-wave voltammograms of probe DNA (26-mer) and probe/target DNA hybrid to show the detection limit of the probe functionalized np-Au MEA sensor upon exposure to different target concentrations. Decrease in the SWV peak indicates successful hybridization.</p> Full article ">Figure A7
<p>Example SWV raw data for BRCA2 probe and (<b>A</b>) BRCA2:BRCA2 hybrid perfect-match, (<b>B</b>) BRCA2:BRCA1 mismatch hybrid current signal in the microfluidic channel used to generate <a href="#nanomaterials-08-00351-f005" class="html-fig">Figure 5</a>—Multiplexed detection of breast cancer-related biomarkers.</p> Full article ">Figure A8
<p>Influence of mercaptohexanol (MCH) incubation duration on the probe current for (<b>A</b>) pl-Au and (<b>B</b>) np-Au electrodes. For both morphologies optimal MCH incubation duration ranges between 10 to 60 min.</p> Full article ">Figure A9
<p>Influence of MCH incubation duration on the peak probe DNA current for different morphologies, where the incubation duration preceding the reduction in peak current indicates the optimal duration for comparing the amount of immobilized probe DNA on different electrode morphologies. (<b>A</b>) 10 min was identified as the optimal MCH incubation duration for comparing pl-Au and unannealed np-Au. (<b>B</b>) 20 min was the optimal MCH incubation duration for comparing unannealed np-Au and annealed np-Au.</p> Full article ">
15 pages, 6268 KiB  
Article
Performance Assessment of Ordered Porous Electrospun Honeycomb Fibers for the Removal of Atmospheric Polar Volatile Organic Compounds
by Yixin Wang, Hong Tao, Dengguang Yu and Changtang Chang
Nanomaterials 2018, 8(5), 350; https://doi.org/10.3390/nano8050350 - 21 May 2018
Cited by 18 | Viewed by 4619
Abstract
This study explored a new facile method of preparing ordered porous electrospun honeycomb fibers to obtain the most promising composites for maximal adsorption of volatile organic compounds (VOCs). The self-assembly ordered porous material (OPM) and polyacrylonitrile (PAN) were formulated into a blend solution [...] Read more.
This study explored a new facile method of preparing ordered porous electrospun honeycomb fibers to obtain the most promising composites for maximal adsorption of volatile organic compounds (VOCs). The self-assembly ordered porous material (OPM) and polyacrylonitrile (PAN) were formulated into a blend solution to prepare honeycomb fibers. SEM and TEM images showed that OPM was effectively bonded in PAN fibers because of the composite’s structure. Acetone was used as a model to assess the VOC adsorption performances of electrospun honeycomb fibers with different OPM contents. Experimental results revealed that the adsorption capacity of honeycomb fibers increased with the increase of loaded OPM within the PAN fibers. The highest adsorption capacity was 58.2 μg g−1 by the fibers containing with 60% OPM in weight. After several recycling times, the adsorption capacities of the reused honeycomb fibers were almost the same with the fresh fibers. This finding indicated that the electrospun honeycomb fibers have potential application in removing VOCs in the workplace, and promote the performance of masks for odor removal. Full article
(This article belongs to the Special Issue Functional Nanomaterials by Electrospinning)
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<p>Diagram of performance assessment system.</p> Full article ">Figure 2
<p>(<b>a</b>) A diagram of the electrospinning system; (<b>b</b>) Two typical digital images about the working processes during electrospinning.</p> Full article ">Figure 3
<p>Morphological images of single honeycomb fibers: (<b>a</b>) 20% M-P; (<b>b</b>) 20% M-P-EDS; (<b>c</b>) 40% M-P; (<b>d</b>) 40% M-P-EDS; (<b>e</b>) 60% M-P; (<b>f</b>) 60% M-P-EDS; (<b>g</b>) 80% M-P; (<b>h</b>) 80% M-P-EDS.</p> Full article ">Figure 3 Cont.
<p>Morphological images of single honeycomb fibers: (<b>a</b>) 20% M-P; (<b>b</b>) 20% M-P-EDS; (<b>c</b>) 40% M-P; (<b>d</b>) 40% M-P-EDS; (<b>e</b>) 60% M-P; (<b>f</b>) 60% M-P-EDS; (<b>g</b>) 80% M-P; (<b>h</b>) 80% M-P-EDS.</p> Full article ">Figure 4
<p>TEM images of 60% M-P: (<b>a</b>) fiber and (<b>b</b>) node.</p> Full article ">Figure 5
<p>XRD patterns of (<b>a</b>) honeycomb composite fibers and (<b>b</b>) OPM.</p> Full article ">Figure 6
<p>FT-IR spectra of the honeycomb fibers.</p> Full article ">Figure 7
<p>Contact angles of honeycomb fibers with different OPM contents.</p> Full article ">Figure 8
<p>Adsorption capacity of honeycomb fibers with different OPM contents (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 9
<p>Adsorption capacity estimation for acetone adsorption (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 10
<p>The influences of recycling times on the acetone adsorption by honeycomb fibers (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 11
<p>The influence of temperature on equilibrium acetone adsorption capacity of honeycomb fibers (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 12
<p>Desorption time of 60% M-P at different temperatures (<span class="html-italic">n</span> = 3).</p> Full article ">Figure 13
<p>A diagram about the honeycomb fiber adsorption process of acetone.</p> Full article ">
31 pages, 3734 KiB  
Review
Graphene-Based Nanomaterials for Tissue Engineering in the Dental Field
by Riccardo Guazzo, Chiara Gardin, Gloria Bellin, Luca Sbricoli, Letizia Ferroni, Francesco Saverio Ludovichetti, Adriano Piattelli, Iulian Antoniac, Eriberto Bressan and Barbara Zavan
Nanomaterials 2018, 8(5), 349; https://doi.org/10.3390/nano8050349 - 20 May 2018
Cited by 116 | Viewed by 9236
Abstract
The world of dentistry is approaching graphene-based nanomaterials as substitutes for tissue engineering. Apart from its exceptional mechanical strength, electrical conductivity and thermal stability, graphene and its derivatives can be functionalized with several bioactive molecules. They can also be incorporated into different scaffolds [...] Read more.
The world of dentistry is approaching graphene-based nanomaterials as substitutes for tissue engineering. Apart from its exceptional mechanical strength, electrical conductivity and thermal stability, graphene and its derivatives can be functionalized with several bioactive molecules. They can also be incorporated into different scaffolds used in regenerative dentistry, generating nanocomposites with improved characteristics. This review presents the state of the art of graphene-based nanomaterial applications in the dental field. We first discuss the interactions between cells and graphene, summarizing the available in vitro and in vivo studies concerning graphene biocompatibility and cytotoxicity. We then highlight the role of graphene-based nanomaterials in stem cell control, in terms of adhesion, proliferation and differentiation. Particular attention will be given to stem cells of dental origin, such as those isolated from dental pulp, periodontal ligament or dental follicle. The review then discusses the interactions between graphene-based nanomaterials with cells of the immune system; we also focus on the antibacterial activity of graphene nanomaterials. In the last section, we offer our perspectives on the various opportunities facing the use of graphene and its derivatives in associations with titanium dental implants, membranes for bone regeneration, resins, cements and adhesives as well as for tooth-whitening procedures. Full article
(This article belongs to the Special Issue Tissue Engineering and Regenerative Nanomedicine)
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<p>Schematic representation of different graphene-based nanomaterials. (<b>a</b>) Few-Layered Graphene (FLG), (<b>b</b>) Graphene Oxide (GO), (<b>c</b>) graphene nanosheets and (<b>d</b>) reduced Graphene Oxide (rGO) belong to the graphene derivatives group; (<b>e</b>) GO nanoparticle composite and (<b>f</b>) GO polymer composite are composites of graphene. Reproduced with permissions from [<a href="#B25-nanomaterials-08-00349" class="html-bibr">25</a>,<a href="#B26-nanomaterials-08-00349" class="html-bibr">26</a>].</p> Full article ">Figure 2
<p>Morphological observations of cells after interactions with graphene-based nanomaterials. (<b>a</b>) Transmission Electron Microscopy (TEM) images of Mouse Embryo Fibroblasts (MEFs) treated with GO-high (GO-h), GO-medium (GO-m) and GO-low (GO-l) at 50 µg/mL for 24 h. On bottom, high-magnification images of the boxed-in photos on top are represented. The white and black arrows indicate GO aggregates inside and outside cells, respectively. (<b>b</b>) Scanning Electron Microscopy (SEM) images of cell membrane damage incurred by A549 cells as a result of GO nanosheets exposure observed during different phases of incubation. On bottom, high-magnification images of the boxed-in photos on top are represented. Reproduced with permissions from [<a href="#B40-nanomaterials-08-00349" class="html-bibr">40</a>,<a href="#B42-nanomaterials-08-00349" class="html-bibr">42</a>].</p> Full article ">Figure 3
<p>Effect of graphene-based nanomaterials on the osteogenic differentiation of Mesenchymal Stem Cells (MSCs). (<b>a</b>) Evaluation of matrix mineralization by means of Alizarin Red S (ARS) staining (top panel) and quantification (bottom panel). MSCs were grown for 21 days in osteogenic differentiation medium on GO nanosheets. The level of mineralization in the 0.1 μg/mL GO group was significantly higher than the other two conditions. (<b>b</b>) Human BM-MSCs cultured on 3D graphene foams for 4 days show protrusions up to 100 μm in length (yellow arrowheads) that extended from the cell bodies (black arrows), as evidenced by SEM images (top panel). These 3D substrates were also found to promote the expression of the osteogenic markers Osteocalcin (OCN) and Osteopontin (OPN), as displayed by immunofluorescence images (bottom panel). (<b>c</b>) SEM images of the rGO-coated Hap nanocomposites showing that Hydroxyapatite (HAp) particles were partly covered and interconnected by an network of rGO nanosheets (top panel). ARS staining performed at 21 days reveals that rGO-coated HAp nanocomposites significantly increase calcium deposits in MC3T3-E1 cells compared to the non-treated control and rGO or HAp alone (bottom panel). (<b>d</b>) Schematic representation of the study: human BM-MSCs were seeded onto rGO substrates, then exposed to Pulsed Electromagnetic Fields (PEMFs) (top panel). The rGO+PEMFs group exhibited the strongest staining as evidenced by ARS staining performed after 2 weeks from cells seeding. Reproduced with permissions from [<a href="#B50-nanomaterials-08-00349" class="html-bibr">50</a>,<a href="#B51-nanomaterials-08-00349" class="html-bibr">51</a>,<a href="#B53-nanomaterials-08-00349" class="html-bibr">53</a>,<a href="#B62-nanomaterials-08-00349" class="html-bibr">62</a>].</p> Full article ">Figure 4
<p>Interactions of graphene-based nanomaterials with Dental Stem Cells (DSCs). (<b>a</b>) SEM images showing that Dental Pulp Stem Cells (DPSCs) can efficiently adhere and proliferate on GO substrates for 3 and 5 days (top panel). DPSCs on GO present higher expression compared to glass (control) for all genes tested both at 7 and 14 days (bottom panel). (<b>b</b>) SEM images of films composed of Silk Fibroin (SF), GO and GO-SF mixture (3:1) at different magnifications (top panel). Immunofluorescence staining of the actin cytoskeleton showing a higher adhesion of Periodontal Ligament Stem Cells (PDLSCs) on GO and on the GO-SF composite film rather than on SF alone at 7 days. (<b>c</b>) TEM images of GO, Thermally Reduced Graphene Oxide (TRGO) and Nitrogen-doped graphene (N-Gr) (top panel). Confocal microscopy images of human Dental Follicle Progenitor Cells (DFPCs) seeded on GO, TRGO and N-Gr at 40 µg/mL showing staining of cytoskeleton actin filaments (green) and nuclei (red) (bottom panel). Reproduced with permissions from [<a href="#B67-nanomaterials-08-00349" class="html-bibr">67</a>,<a href="#B79-nanomaterials-08-00349" class="html-bibr">79</a>,<a href="#B89-nanomaterials-08-00349" class="html-bibr">89</a>].</p> Full article ">Figure 5
<p>Interactions of graphene with macrophages. (<b>a</b>) Optical micrographs of macrophages treated with 25 µg/mL GO and PVP-GO for 48 h. Macrophages showed to be inclined to GO internalization (red arrows), while the functionalization with PVP prevents the phenomenon. (<b>b</b>) Signaling pathway of macrophage activation stimulated by graphene. Graphene may stimulate Toll-Like Receptors (TLRs), thus activating kinase cascade Myeloid Differentiation primary response gene 88 (MyD88)-dependent mechanism. IKK activation initiates the phosphorylation and degradation of IκB and consequently, the release of NF-κB subunits and their translocation into the nucleus. NF-κB binds to the promoter regions of its effector genes and initiates the transcription of multiple pro-inflammatory genes and the secretion of Interleukin 1α (IL-1α), IL-6, IL-10, Tumor Necrosis Factor alpha (TNF-α). Reproduced with permissions from [<a href="#B92-nanomaterials-08-00349" class="html-bibr">92</a>,<a href="#B99-nanomaterials-08-00349" class="html-bibr">99</a>].</p> Full article ">Figure 6
<p>Effect of GO nanosheets on bacteria. (<b>a</b>) Atomic Force Microscopy (AFM) amplitude (top) and 3D (bottom) images of <span class="html-italic">Escherichia coli</span> cells 2 h of after incubation with/without GO sheets. <span class="html-italic">E. coli</span> cells incubated with deionized water without GO sheets show a preserved integrity of the membrane (control). The incubation with the 40 μg/mL large GO sheets suspension results in a completely cover of bacterium surface by GO sheets, whereas small GO sheets adhere to cell surface without fully covering it. Scale bars are 1 μm. (<b>b</b>) TEM images of <span class="html-italic">Streptococcus mutans, Fusobacterium nucleatum</span> and <span class="html-italic">Porphyromonas gingivalis</span> cells after incubation with GO nanosheets dispersion (right side) for 2 h and after incubation with saline solution for 2 h as control (left side). All treated cases had the same GO dose of 80 μg/mL. Scale bars are 500 nm. Reproduced with permissions from [<a href="#B113-nanomaterials-08-00349" class="html-bibr">113</a>,<a href="#B114-nanomaterials-08-00349" class="html-bibr">114</a>].</p> Full article ">Figure 7
<p>Bone regeneration of Ti implants with or without GO coating and BMP-2/SP loading in mouse calvarial defects 8 weeks after treatment. The red arrowheads indicate the newly formed bone, the black arrowheads indicate the implant at (<b>a</b>) 12.5× magnification and (<b>b</b>) 100× magnification. Reproduced with permissions from [<a href="#B136-nanomaterials-08-00349" class="html-bibr">136</a>].</p> Full article ">Figure 8
<p>Different GO coating concentration on collagen membrane from porcine dermis. (<b>a</b>) SEM images of uncoated, 2 μg/mL and 10 μg/mL GO-coated membranes. 4.05 k magnification. (<b>b</b>) Hematoxylin-Eosin staining of uncoated, 2 μg/mL and 10 μg/mL GO-coated membranes with DPSCs after 28 days of culture. 40× magnification. Reproduced with permissions from [<a href="#B144-nanomaterials-08-00349" class="html-bibr">144</a>,<a href="#B145-nanomaterials-08-00349" class="html-bibr">145</a>].</p> Full article ">Figure 9
<p>Strategies based on graphene for improving teeth-whitening. (<b>a</b>) A schematic diagram illustrating the enhanced peroxidase-like catalytic activity of the rGO-Co. Reactions of Cobalt Tetraphenylporphyrin (CoTPP) with Hydrogen Peroxide (H<sub>2</sub>O<sub>2</sub>): Co<sub>III</sub> TPP–e<sub>2</sub>1(1/2) H<sub>2</sub>O<sub>2</sub> → (Co<sub>IV</sub>) TPP-OH<sub>2</sub> (Co<sub>IV</sub>) TPP-OH → 2 Co<sub>III</sub> TPP1O<sub>2</sub>12H<sub>1</sub>. (<b>b</b>) Photographs of teeth stained with dye D&amp;C Red 34 and bleached using H<sub>2</sub>O<sub>2</sub> alone or H<sub>2</sub>O<sub>2</sub> plus CoTPP/RGO for 0.5 (left) or 70 h (right). Reproduced with permissions of [<a href="#B150-nanomaterials-08-00349" class="html-bibr">150</a>].</p> Full article ">
19 pages, 13457 KiB  
Article
Finite Element Analysis of Electrospun Nanofibrous Mats under Biaxial Tension
by Yunlei Yin and Jie Xiong
Nanomaterials 2018, 8(5), 348; https://doi.org/10.3390/nano8050348 - 19 May 2018
Cited by 20 | Viewed by 5617
Abstract
Due to the non-uniform material properties of electrospun nanofibrous mats and the non-linear characteristics of single fibers, establishing a numerical model that can fully explain these features and correctly describe their properties is difficult. Based on the microstructure of electrospun nanofibrous mats, two [...] Read more.
Due to the non-uniform material properties of electrospun nanofibrous mats and the non-linear characteristics of single fibers, establishing a numerical model that can fully explain these features and correctly describe their properties is difficult. Based on the microstructure of electrospun nanofibrous mats, two macroscopic continuum finite element (FE) models with a uniform or oriented nanofiber distribution were established to describe the mechanical behavior of nanofibrous mats under biaxial tension. The FE models were verified by biaxial tension experiments on silk fibroin/polycaprolactone nanofibrous mats. The developed FE models expressed the mechanical behaviors of the mats under biaxial tension well. These models can help clarify the structure–property relationship of electrospun nanofibrous mats and guide the design of materials for engineering applications. Full article
(This article belongs to the Special Issue Functional Nanomaterials by Electrospinning)
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<p>FE-SEM images of electrospun silk fibroin (SF)/polycaprolactone (PCL) nanofibrous mats. Here, (<b>a</b>) and (<b>b</b>) are nanofibrous mats produced under a roller speed of 0 m·s<sup>−1</sup>; (<b>c</b>) and (<b>d</b>) are nanofibrous mats produced under a roller speed of 11.88 m·s<sup>−1</sup>; (<b>a</b>) and (<b>c</b>), 2000× magnification (scale bar = 5 microns); (<b>b</b>) and (<b>d</b>), 5000× magnification (scale bar = 2 microns).</p> Full article ">Figure 2
<p>Fiber orientation distribution in the SF/PCL nanofibrous mats produced at (<b>a</b>) rotation speed=0 m∙s<sup>−1</sup> and (<b>b</b>) rotation speed=11.88 m∙s<sup>−1</sup>.</p> Full article ">Figure 3
<p>Biaxial stress-strain curves of the SF/PCL nanofibrous mats. (<b>a</b>) Uniform fiber distribution (rotation speed 0 m·s<sup>−1</sup>); (<b>b</b>) oriented fiber distribution (rotation speed 11.88 m·s<sup>−1</sup>).</p> Full article ">Figure 4
<p>Configuration of the nanofibrous mats.</p> Full article ">Figure 5
<p>Boundary condition setting of biaxial tension. (<b>a</b>) schematic diagram; (<b>b</b>) loading mode.</p> Full article ">Figure 6
<p>Biaxial tension of the SF/PCL nanofibrous mats (Uniaxial test data reproduced from reference [<a href="#B31-nanomaterials-08-00348" class="html-bibr">31</a>], with permission from MDPI, 2018).</p> Full article ">Figure 7
<p>Biaxial tension cloud charts of uniform nanofibrous mats (aspect ratio 1:1, porosity 0.75). 1. strain = 2%, (<b>a</b>) stress (<b>b</b>) strain; 2. strain = 5%, (<b>c</b>) stress (<b>d</b>) strain; 3. strain = 10%, (<b>e</b>) stress (<b>f</b>) strain.</p> Full article ">Figure 8
<p>Biaxial tension stress-strain curves of three random models.</p> Full article ">Figure 9
<p>Biaxial tension stress cloud charts (aspect ratio 2:1, porosity 0.75). (<b>a</b>) strain = 2%; (<b>b</b>) strain = 5%; (<b>c</b>) strain = 10%.</p> Full article ">Figure 10
<p>Biaxial tension stress cloud charts (aspect ratio 4:1, porosity 0.75). (<b>a</b>) strain = 2%; (<b>b</b>) strain = 5%; (<b>c</b>) strain = 10%.</p> Full article ">Figure 11
<p>Biaxial tension stress cloud charts (aspect ratio 8:1, porosity 0.75). (<b>a</b>) strain = 2%; (<b>b</b>) strain = 5%; (<b>c</b>) strain = 10%.</p> Full article ">Figure 12
<p>Biaxial tension simulation stress-strain curves of models with four different aspect ratios in the (<b>a</b>) X direction and (<b>b</b>) Y direction.</p> Full article ">Figure 13
<p>Biaxial tension simulation stress-strain curves of models with four different porosity ratios in the (<b>a</b>) X direction and (<b>b</b>) Y direction.</p> Full article ">Figure 14
<p>Oriented SF/PCL nanofibrous mats. (<b>a</b>) FE model; (<b>b</b>) biaxial loading mode.</p> Full article ">Figure 15
<p>Biaxial stress-strain curves of the oriented nanofibrous mats.</p> Full article ">Figure 16
<p>Biaxial tension cloud charts of the oriented nanofibrous mats (aspect ratio 1:1, porosity 0.75). 1. strain = 2%, (<b>a</b>) stress (<b>b</b>) strain; 2. strain = 5%, (<b>c</b>) stress (<b>d</b>) strain; 3. strain = 10%, (<b>e</b>) stress (<b>f</b>) strain.</p> Full article ">
16 pages, 4772 KiB  
Article
Loading of Indocyanine Green within Polydopamine-Coated Laponite Nanodisks for Targeted Cancer Photothermal and Photodynamic Therapy
by Fanli Xu, Mengxue Liu, Xin Li, Zhijuan Xiong, Xueyan Cao, Xiangyang Shi and Rui Guo
Nanomaterials 2018, 8(5), 347; https://doi.org/10.3390/nano8050347 - 19 May 2018
Cited by 52 | Viewed by 6658
Abstract
The combination of photothermal therapy (PTT) and photodynamic therapy (PDT) in cancer treatment has attracted much attention in recent years. However, developing highly efficient and targeted therapeutic nanoagents for amplifying PTT and PDT treatments remains challenging. In this work, we developed a novel [...] Read more.
The combination of photothermal therapy (PTT) and photodynamic therapy (PDT) in cancer treatment has attracted much attention in recent years. However, developing highly efficient and targeted therapeutic nanoagents for amplifying PTT and PDT treatments remains challenging. In this work, we developed a novel photothermal and photodynamic therapeutic nanoplatform for treatment of cancer cells overexpressing integrin αvβ3 through the coating of polydopamine (PDA) on indocyanine green (ICG)-loaded laponite (LAP) and then further conjugating polyethylene glycol-arginine-glycine-aspartic acid (PEG-RGD) as targeted agents on the surface. The ICG/LAP–PDA–PEG–RGD (ILPR) nanoparticles (NPs) formed could load ICG with a high encapsulation efficiency of 94.1%, improve the photostability of loaded ICG dramatically via the protection of PDA and LAP, and display excellent colloidal stability and biocompatibility due to the PEGylation. Under near-infrared (NIR) laser irradiation, the ILPR NPs could exert enhanced photothermal conversion reproducibly and generate reactive oxygen species (ROS) efficiently. More importantly, in vitro experiments proved that ILPR NPs could specifically target cancer cells overexpressing integrin αvβ3, enhance cellular uptake due to RGD-mediated targeting, and exert improved photothermal and photodynamic killing efficiency against targeted cells under NIR laser irradiation. Therefore, ILPR may be used as effective therapeutic nanoagents with enhanced photothermal conversion performance and ROS generating ability for targeted PTT and PDT treatment of cancer cells with integrin αvβ3 overexpressed. Full article
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<p>(<b>a</b>) Ultraviolet/visible (UV-vis) spectra of LAP, ICG and ICG/LAP; (<b>b</b>) X-ray diffraction (XRD) patterns of LAP, ICG and ICG/LAP; (<b>c</b>) temperature rising curve of water, LAP, ICG, and ICG/LAP solutions; and (<b>d</b>) temperature changes of ICG and ICG/LAP solutions at the same ICG concentration (<span class="html-italic">C</span><sub>ICG</sub> = 120 μg/mL) under an 808 nm laser irradiation (1.2 W/cm<sup>2</sup>) for 3 cycles (3 min of irradiation for each cycle).</p> Full article ">Figure 2
<p>(<b>a</b>) <sup>1</sup>H nuclear magnetic resonance (NMR) spectra in D<sub>2</sub>O and (<b>b</b>) Fourier transform-infrared (FT-IR) spectra of LAP, PDA and LAP–PDA; (<b>c</b>) TGA curves of LAP and LAP-PDA; (<b>d</b>) temperature rising curves of LAP and LAP–PDA solutions (<span class="html-italic">C</span><sub>PDA</sub> = 300 μg/mL) under an 808 nm laser irradiation (1.2 W/cm<sup>2</sup>, 3 min), respectively.</p> Full article ">Figure 3
<p>(<b>a</b>) UV-vis spectra of ICG, LAP, ICG/LAP, LAP–PDA and ICG/LAP–PDA at the same ICG concentration; (<b>b</b>) temperature rising curveof water, LAP, ICG, ICG/LAP, LAP–PDA and ICG/LAP–PDA solutions at the same ICG concentration (<span class="html-italic">C</span><sub>ICG</sub> = 100 μg/mL) under an 808 nm laser irradiation (1.2 W/cm<sup>2</sup>, 3 min);(<b>c</b>) temperature changes of free ICG, ICG/LAP, LAP–PDA and ICG/LAP–PDA solutions at the same ICG concentration (<span class="html-italic">C</span><sub>ICG</sub> = 100 μg/mL) under irradiation of the 808 nm laser for 5 cycles (1.2 W/cm<sup>2</sup>, 3 min of irradiation for each cycle); (<b>d</b>) ICG release from ICG/LAP and ICG/LAP–PDA at 37 °C in the acetate buffers (pH = 5.0).</p> Full article ">Figure 4
<p>(<b>a</b>) The transmission electron microscope (TEM) image and (<b>b</b>) corresponding size distribution of ICG/LAP–PDA–<span class="html-italic">m</span>PEG; (<b>c</b>)the TGA curves of LAP, ICG/LAP, ICG/LAP–PDA, ICG/LAP–PDA–<span class="html-italic">m</span>PEG and ILPR, respectively; (<b>d</b>) temperature rising curve of ICG/LAP–PDA, ICG/LAP–PDA–<span class="html-italic">m</span>PEG and ILPR solutions (<span class="html-italic">C</span><sub>ICG</sub> = 100 μg/mL) under an 808 nm laser irradiation (1.2 W/cm<sup>2</sup>, 3 min).</p> Full article ">Figure 5
<p>(<b>a</b>) CCK-8 viability assay of MDA-MB-231 cells after treatment with LAP–PDA–PEG–RGD, ICG/LAP–PDA–<span class="html-italic">m</span>PEG and ILPR NPs at the same ICG concentration (<span class="html-italic">C</span><sub>ICG</sub> = 5, 10, 20, 30, 40 μg/mL) for 24 h, respectively; (<b>b</b>) Cellular uptake of Si of MDA-MB-231 cells after treatment with ICG/LAP–PDA–<span class="html-italic">m</span>PEG and ILPR NPs at the same ICG concentration (<span class="html-italic">C</span><sub>ICG</sub>=5, 10, 20, 30, 40 μg/mL) for 6 h, respectively. Phosphate-buffered saline(PBS) buffer was used as control. One-way ANOVA statistical analysis was performed to evaluate the experimental data. A <span class="html-italic">p</span> value of 0.05 was selected as the significance level, and the data were indicated with (*) for <span class="html-italic">p</span> &lt; 0.05, (**) for <span class="html-italic">p</span> &lt; 0.01, and (***) for <span class="html-italic">p</span> &lt; 0.001, respectively.</p> Full article ">Figure 6
<p>(<b>a</b>) Consumption of DPBF (1,3-diphenylisobenzofuran)over time due to <sup>1</sup>O<sub>2</sub> generation for water, LAP, ICG, LAP–PDA–PEG–RGD and ILPR aqueous solution with an 808 nm laser irradiation (1.2 W/cm<sup>2</sup>); (<b>b</b>) mean fluorescence of DCF in MDA-MB-231cells stained by DCF-H after incubated with LAP–PDA–PEG–RGD and ILPR NPs at the same ICG concentration (<span class="html-italic">C</span><sub>ICG</sub> = 10, 40 μg/mL) with/without laser irradiation (1.2 W/cm<sup>2</sup>, 5 min), a <span class="html-italic">p</span> value of 0.05 was selected as the significance level, and the data were indicated with (*) for <span class="html-italic">p</span> &lt; 0.05, (**) for <span class="html-italic">p</span> &lt; 0.01, and (***) for <span class="html-italic">p</span> &lt; 0.001, respectively; (<b>c</b>) fluorescence microscopic images of MDA-MB-231cells stained by DCF-H after the cells incubated with LAP–PDA–PEG–RGD and ILPR NPs (<span class="html-italic">C</span><sub>ICG</sub> = 40 μg/mL) with/without laser irradiation (+L/-L) (1.2 W/cm<sup>2</sup>, 5 min).PBS buffer was used as control.</p> Full article ">Figure 7
<p>Cell viabilities of MDA-MB-231 cells after incubated with LAP–PDA–PEG–RGD, ICG/LAP–PDA–<span class="html-italic">m</span>PEG and ILPR NPs (<b>a</b>) at different ICG concentrations (<span class="html-italic">C</span><sub>ICG</sub> = 10, 20, 40 μg/mL) with/without irradiation of an 808 nm laser (2.5 cm<sup>2</sup>, 1.2 W/cm<sup>2</sup>, 5 min); and (<b>b</b>) at the same ICG concentration (<span class="html-italic">C</span><sub>ICG</sub> = 40 μg/mL) with an 808 nm laser irradiation (2.5 cm<sup>2</sup>, 5 min) at different power densities (0.8, 1.0, 1.2 W/cm<sup>2</sup>), a<span class="html-italic">p</span> value of 0.05 was selected as the significance level, and the data were indicated with (*) for <span class="html-italic">p</span> &lt; 0.05, (**) for <span class="html-italic">p</span> &lt; 0.01, and (***) for <span class="html-italic">p</span> &lt; 0.001, respectively.; (<b>c</b>) fluorescence microscopic images of Calcein AM and PI co-staining MDA-MB-231 cells after treatment with PBS, LAP–PDA–PEG–RGD, ICG/LAP–PDA–<span class="html-italic">m</span>PEG and ILPR at the same ICG concentration (<span class="html-italic">C</span><sub>ICG</sub> = 40 μg/mL) with/without (−L/+L) irradiation of an 808 nm laser (0.25 cm<sup>2</sup>, 1.2 W/cm<sup>2</sup>, 5 min). PBS buffer was used as control.</p> Full article ">Scheme 1
<p>Schematic illustration of the synthesis of ICG/LAP-PDA-<span class="html-italic">m</span>PEG and ICG/LAP-PDA-PEG-RGD (ILPR) nanoparticles (NPs).</p> Full article ">
21 pages, 4302 KiB  
Review
Synthesis of Alkanethiolate-Capped Metal Nanoparticles Using Alkyl Thiosulfate Ligand Precursors: A Method to Generate Promising Reagents for Selective Catalysis
by Khin Aye San and Young-Seok Shon
Nanomaterials 2018, 8(5), 346; https://doi.org/10.3390/nano8050346 - 18 May 2018
Cited by 32 | Viewed by 6917
Abstract
Evaluation of metal nanoparticle catalysts functionalized with well-defined thiolate ligands can be potentially important because such systems can provide a spatial control in the reactivity and selectivity of catalysts. A synthetic method utilizing Bunte salts (sodium S-alkylthiosulfates) allows the formation of metal [...] Read more.
Evaluation of metal nanoparticle catalysts functionalized with well-defined thiolate ligands can be potentially important because such systems can provide a spatial control in the reactivity and selectivity of catalysts. A synthetic method utilizing Bunte salts (sodium S-alkylthiosulfates) allows the formation of metal nanoparticles (Au, Ag, Pd, Pt, and Ir) capped with alkanethiolate ligands. The catalysis studies on Pd nanoparticles show a strong correlation between the surface ligand structure/composition and the catalytic activity and selectivity for the hydrogenation/isomerization of alkenes, dienes, trienes, and allylic alcohols. The high selectivity of Pd nanoparticles is driven by the controlled electronic properties of the Pd surface limiting the formation of Pd–alkene adducts (or intermediates) necessary for (additional) hydrogenation. The synthesis of water soluble Pd nanoparticles using ω-carboxylate-S-alkanethiosulfate salts is successfully achieved and these Pd nanoparticles are examined for the hydrogenation of various unsaturated compounds in both homogeneous and heterogeneous environments. Alkanethiolate-capped Pt nanoparticles are also successfully synthesized and further investigated for the hydrogenation of various alkynes to understand their geometric and electronic surface properties. The high catalytic activity of activated terminal alkynes, but the significantly low activity of internal alkynes and unactivated terminal alkynes, are observed for Pt nanoparticles. Full article
(This article belongs to the Special Issue Synthesis of Ligand-Capped Nanoparticles for Catalysis)
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<p>(<b>a</b>) TEM image and (<b>b</b>) size distribution histogram of PtNP generated from sodium S-octylthiosulfate. Reproduced from Ref. [<a href="#B64-nanomaterials-08-00346" class="html-bibr">64</a>] with permission from the American Chemical Society, 2017.</p> Full article ">Figure 2
<p>Isomerization and hydrogenation of allyl alcohol in nonpolar (<b>a</b>) and polar (<b>b</b>) solvents. Reproduced from Ref. [<a href="#B71-nanomaterials-08-00346" class="html-bibr">71</a>] with permission from the American Chemical Society, 2012.</p> Full article ">Figure 3
<p>Biphasic catalytic reaction of hydrophobic allylic alcohols in water (5–10 mol % Pd/substrate, 50 μL substrate in 3 mL water or PBS buffer pH 7.4 solution, 1 atm H<sub>2</sub>). Reproduced from Ref. [<a href="#B72-nanomaterials-08-00346" class="html-bibr">72</a>] with permission from the ELSEVIER, 2017.</p> Full article ">Figure 4
<p>Proposed mechanism for the catalytic conversion of penta-1,4-diene by alkanethiolate-capped PdNP (5 mol % Pd/substrate, 0.5 mmol substrate in 2.5 mL CDCl<sub>3</sub>, 1 atm H<sub>2</sub>). Reproduced from Ref. [<a href="#B74-nanomaterials-08-00346" class="html-bibr">74</a>] with permission from the Royal Society of Chemistry, 2015.</p> Full article ">Scheme 1
<p>The synthesis of gold nanoparticles by using Brust–Schiffrin method. Reproduced from Ref. [<a href="#B14-nanomaterials-08-00346" class="html-bibr">14</a>] with permission from the American Chemical Society, 2009.</p> Full article ">Scheme 2
<p>(<b>a</b>) Synthesis of AuNP using the S-dodecylthiosulfate ligand and (<b>b</b>) synthesis of SO<sub>3</sub>–AuNP using the acid-functionalized thiosulfate ligand. Reproduced from Ref [<a href="#B54-nanomaterials-08-00346" class="html-bibr">54</a>] and [<a href="#B55-nanomaterials-08-00346" class="html-bibr">55</a>] with permission from the American Chemical Society, 2000 and 2001, respectively.</p> Full article ">Scheme 3
<p>The mechanism of self-assembled monolayer formation on gold surface. Reproduced from Ref [<a href="#B58-nanomaterials-08-00346" class="html-bibr">58</a>] with permission from the American Chemical Society, 2011.</p> Full article ">Scheme 4
<p>Synthesis of AgNPs using S-dodecylthiosulfate in H<sub>2</sub>O. Reproduced from Ref. [<a href="#B56-nanomaterials-08-00346" class="html-bibr">56</a>] with permission from the American Chemical Society, 2004.</p> Full article ">Scheme 5
<p>Synthesis of alkanethiolate-capped PdNP generated from S-dodecylthiosulfate. Reproduced from Ref. [<a href="#B59-nanomaterials-08-00346" class="html-bibr">59</a>] with permission from the American Chemical Society, 2012.</p> Full article ">Scheme 6
<p>Proposed mechanism for iridium nanoparticles from dodecanethiol and S-dodecylthiosulfate. Reproduced from Ref. [<a href="#B67-nanomaterials-08-00346" class="html-bibr">67</a>] with permission from the American Chemical Society, 2014.</p> Full article ">Scheme 7
<p>The isomerization of allylic alcohols using synthesized PdNP (5 mol % Pd/substrate, 2.9 mmol substrate in 5 mL CDCl<sub>3</sub>, 1 atm H<sub>2</sub>). R<sub>1-4</sub> = H, CH<sub>3</sub>, or alkyl. Adapted from Ref. [<a href="#B70-nanomaterials-08-00346" class="html-bibr">70</a>] with permission from the Elsevier, 2011.</p> Full article ">Scheme 8
<p>Semihydrogenation and isomerization of propargyl alcohols (5 mol % Pd/substrate, 50 μL substrate in 2 mL solvent, 1 atm H<sub>2</sub>). R<sub>1-2</sub> = H or alkyl. Reproduced from Ref. [<a href="#B73-nanomaterials-08-00346" class="html-bibr">73</a>] with permission from the Royal Society of Chemistry, 2013.</p> Full article ">Scheme 9
<p>Proposed mechanism for the catalytic reaction of 2,3-dimethylbuta-1,3-diene with octanethiolate-capped Pd nanoparticles. Reproduced from Ref. [<a href="#B75-nanomaterials-08-00346" class="html-bibr">75</a>] with permission from the Royal Society of Chemistry, 2017.</p> Full article ">Scheme 10
<p>Catalysis reaction of methyl propiolate by PtNP (5 mol % Pt/substrate, 0.25 mmol substrate in 2 mL CDCl<sub>3</sub>, 1 atm H<sub>2</sub>). Reproduced from Ref. [<a href="#B64-nanomaterials-08-00346" class="html-bibr">64</a>] with permission from the American Chemical Society, 2017.</p> Full article ">
11 pages, 3975 KiB  
Article
Three-Dimensional Bi2Te3 Networks of Interconnected Nanowires: Synthesis and Optimization
by Alejandra Ruiz-Clavijo, Olga Caballero-Calero and Marisol Martín-González
Nanomaterials 2018, 8(5), 345; https://doi.org/10.3390/nano8050345 - 18 May 2018
Cited by 22 | Viewed by 4258
Abstract
Self-standing Bi2Te3 networks of interconnected nanowires were fabricated in three-dimensional porous anodic alumina templates (3D–AAO) with a porous structure spreading in all three spatial dimensions. Pulsed electrodeposition parameters were optimized to grow highly oriented Bi2Te3 interconnected nanowires [...] Read more.
Self-standing Bi2Te3 networks of interconnected nanowires were fabricated in three-dimensional porous anodic alumina templates (3D–AAO) with a porous structure spreading in all three spatial dimensions. Pulsed electrodeposition parameters were optimized to grow highly oriented Bi2Te3 interconnected nanowires with stoichiometric composition inside those 3D–AAO templates. The nanowire networks were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and Raman spectroscopy. The results are compared to those obtained in films and 1D nanowires grown under similar conditions. The crystalline structure and composition of the 3D Bi–Te nanowire network are finely tuned by controlling the applied voltage and the relaxation time off at zero current density during the deposition. With this fabrication method, and controlling the electrodeposition parameters, stoichiometric Bi2Te3 networks of interconnected nanowires have been obtained, with a preferential orientation along [1 1 0], which makes them optimal candidates for out-of-plane thermoelectric applications. Moreover, the templates in which they are grown can be dissolved and the network of interconnected nanowires is self-standing without affecting its composition and orientation properties. Full article
(This article belongs to the Special Issue Synthesis and Characterization of Nanowires)
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<p>Cyclic voltammetry performed at a scan rate of 10 mV/s, when three different working electrodes are used, namely gold over a silicon substrate (black line), 1D–AAO template (dashed green) and 3D–AAO template (dotted blue).</p> Full article ">Figure 2
<p>Cyclic voltammetry performed at a scan rate 10 mV/s, showing the different applied voltages at which the nanowire networks (named as 3DNW–#) and films (named as TF–#) were fabricated in pulsed mode.</p> Full article ">Figure 3
<p>XRD diffraction patterns of films (<b>a</b>) TF–1 (non-stoichiometric Bi<sub>2</sub>.<sub>31</sub>Te<sub>2.69</sub>) and (<b>b</b>) stoichiometric TF–4, and 3D nanowire networks (<b>c</b>) non-stoichiometric 3DNW–5 (non-stoichiometric Bi<sub>1</sub>.<sub>86</sub>Te<sub>3.14</sub>) and (<b>d</b>) stoichiometric 3DNW–4. The blue line has been chosen for non-stoichiometric samples and red for the stoichiometric ones.</p> Full article ">Figure 4
<p>Raman spectra of stoichiometric Bi<sub>2</sub>Te<sub>3</sub>: (<b>a</b>) thin film (TF–4), (<b>b</b>) conventional 1D nanowire arrays (1DNW–1), and (<b>c</b>) 3D nanowires networks (3DNW–4).</p> Full article ">Figure 5
<p>(<b>a</b>,<b>b</b>) Cross-sectional SEM micrograph images of 3DNW–4 with (<b>a</b>) secondary electrons and (<b>b</b>) backscattered electrons; (<b>c</b>) Top-view SEM image of the 3DNW–4, showing a nanowire diameter of 45–50 nm; (<b>d</b>) 3D Bi<sub>2</sub>Te<sub>3</sub> nanowire network (3DNW–4) SEM micrograph after removing the 3D–AAO template; (<b>e</b>) Photograph of a 3D–AAO partially filled with Bi<sub>2</sub>Te<sub>3</sub> and (<b>f</b>) the same sample after chemical etching of the 3D–AAO template, that is, a macroscopic free-standing 3D Bi<sub>2</sub>Te<sub>3</sub> nanowire network. This sample is free-standing and can be manipulated easily with the help of tweezers.</p> Full article ">
18 pages, 23737 KiB  
Review
Recent Progress in Upconversion Photodynamic Therapy
by Hailong Qiu, Meiling Tan, Tymish Y. Ohulchanskyy, Jonathan F. Lovell and Guanying Chen
Nanomaterials 2018, 8(5), 344; https://doi.org/10.3390/nano8050344 - 18 May 2018
Cited by 113 | Viewed by 9084
Abstract
Photodynamic therapy (PDT) is a minimally invasive cancer modality that combines a photosensitizer (PS), light, and oxygen. Introduction of new nanotechnologies holds potential to improve PDT performance. Upconversion nanoparticles (UCNPs) offer potentially advantageous benefits for PDT, attributed to their distinct photon upconverting feature. [...] Read more.
Photodynamic therapy (PDT) is a minimally invasive cancer modality that combines a photosensitizer (PS), light, and oxygen. Introduction of new nanotechnologies holds potential to improve PDT performance. Upconversion nanoparticles (UCNPs) offer potentially advantageous benefits for PDT, attributed to their distinct photon upconverting feature. The ability to convert near-infrared (NIR) light into visible or even ultraviolet light via UCNPs allows for the activation of nearby PS agents to produce singlet oxygen, as most PS agents absorb visible and ultraviolet light. The use of a longer NIR wavelength permits light to penetrate deeper into tissue, and thus PDT of a deeper tissue can be effectively achieved with the incorporation of UCNPs. Recent progress in UCNP development has generated the possibility to employ a wide variety of NIR excitation sources in PDT. Use of UCNPs enables concurrent strategies for loading, targeting, and controlling the release of additional drugs. In this review article, recent progress in the development of UCNPs for PDT applications is summarized. Full article
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<p>(<b>a</b>) Schematic illustration of the penetration depth of different wavelengths in a tissue model; (<b>b</b>) Upconverison nanoparticle as a frequency conversion nanotransducer to convert the NIR excitation to visible emission for activation of the photosensitizer, producing reactive singlet molecular oxygen that destroys diseased sites.</p> Full article ">Figure 2
<p>(<b>a</b>) Time-resolved temperature in the irradiated nude mouse skins during 10 min irradiation of a 980- and 800-nm laser as a function of different power densities. Reproduced with permission from [<a href="#B58-nanomaterials-08-00344" class="html-bibr">58</a>]. Copyright Nature Publishing Group, 2012; (<b>b</b>) Heating effects of 808 nm and 980 nm lasers evaluated by the viability of HeLa cancer cells. Reproduced with permission from [<a href="#B59-nanomaterials-08-00344" class="html-bibr">59</a>]. Copyright The Royal Society of Chemistry, 2015.</p> Full article ">Figure 3
<p>Available and potential excitation wavelengths for UCNPs-based PDT system.</p> Full article ">Figure 4
<p>(<b>A</b>) A UCNP-based theranostic micelle for simultaneous NIR-controlled combination chemotherapy and PDT, as well as fluorescence imaging; (<b>B</b>) An illustration of NIR-triggered hydrophobic-to-hydrophilic transition; (<b>C</b>) An illustration of NIR-controlled combination of chemotherapy and PDT, as well as fluorescence imaging. Reproduced with permission from [<a href="#B69-nanomaterials-08-00344" class="html-bibr">69</a>]. Copyright Wiley-VCH, 2017.</p> Full article ">Figure 5
<p>TEM images of (<b>A</b>) NaYF<sub>4</sub>:Yb,Er; (<b>B</b>) NaYF<sub>4</sub>:Yb,Er@NaYF<sub>4</sub> (UCNP); (<b>C</b>) UCNP@mSiO2/Ce6; (<b>D</b>) Powder X-ray diffraction (XRD) pattern for the UCNP and the calculated line pattern for the hexagonal NaYF4 phase. Inset: HRTEM image of NaYF<sub>4</sub>:Yb,Er shows distinct lattice fringes with an interplanar spacing of 0.51 nm ascribed to the (100) plane of hexagonal NaYF<sub>4</sub>. (<b>E</b>) Schematic illustration of the synthesis and the controlled release process. Reproduced with permission from [<a href="#B73-nanomaterials-08-00344" class="html-bibr">73</a>]. Copyright Wiley-VCH, 2016.</p> Full article ">Figure 5 Cont.
<p>TEM images of (<b>A</b>) NaYF<sub>4</sub>:Yb,Er; (<b>B</b>) NaYF<sub>4</sub>:Yb,Er@NaYF<sub>4</sub> (UCNP); (<b>C</b>) UCNP@mSiO2/Ce6; (<b>D</b>) Powder X-ray diffraction (XRD) pattern for the UCNP and the calculated line pattern for the hexagonal NaYF4 phase. Inset: HRTEM image of NaYF<sub>4</sub>:Yb,Er shows distinct lattice fringes with an interplanar spacing of 0.51 nm ascribed to the (100) plane of hexagonal NaYF<sub>4</sub>. (<b>E</b>) Schematic illustration of the synthesis and the controlled release process. Reproduced with permission from [<a href="#B73-nanomaterials-08-00344" class="html-bibr">73</a>]. Copyright Wiley-VCH, 2016.</p> Full article ">Figure 6
<p>Schematic drawing of the optical fiber placement and illuminated beam sizes in the cell culture experiments (<a href="#nanomaterials-08-00344-f006" class="html-fig">Figure 6</a>A). Cell killing images before and after NIR laser exposure (<a href="#nanomaterials-08-00344-f006" class="html-fig">Figure 6</a>B–D). The black guiding circle represents the region of NIR exposure, which has a diameter of 835 μm as obtained from the calculation above. <a href="#nanomaterials-08-00344-f006" class="html-fig">Figure 6</a>B, C represent the cell killing of the HeLa cancer cells incubated with composite nanoparticles (250 ng L<sup>−1</sup>) containing both UCNP and TPP. At <span class="html-italic">t</span> = 0 there is no killing of cells, but after 45 min of 978 nm illumination at 134 W cm<sup>−2</sup>, 75% of the cells in the illuminated region have red fluorescence indication cell death. <a href="#nanomaterials-08-00344-f006" class="html-fig">Figure 6</a>D and E show the control, in which incubation with the PEG-coated UCNP particles without the TPP photosensitizer showed almost no death after 45 min exposure. The images are superimposed fluorescence and phase contrast images of the cells. Reproduced with permission from [<a href="#B38-nanomaterials-08-00344" class="html-bibr">38</a>]. Copyright Wiley-VCH, 2011.</p> Full article ">Figure 7
<p>(<b>a</b>) Specificity of the UCNPs-C60MA nanoconjugates. Hela cells cultured in folate-free medium (left, positive) and in folate-supplemented medium (middle, negative). The negative control is also performed with A549 cells (right). Scale bar, 50 μm. (<b>b</b>) Cell viability of Hela cells 20 treated with UCNPs-C60MA of different concentration with or without 980 nm exposure. (<b>c</b>,<b>d</b>) The photo of purple formazan dissolved in DMSO, indicating the viability of cells treated with nanoconjugates without 980 nm exposure (<b>c</b>) and with 980 nm exposure (<b>d</b>). (<b>e</b>) The construction and operating principle of the nanoplatform. Reproduced with permission from [<a href="#B68-nanomaterials-08-00344" class="html-bibr">68</a>]. Copyright The Royal Society of Chemistry, 2013.</p> Full article ">Figure 8
<p>(<b>a</b>–<b>d</b>) cells were added with anti-DENV2 envelope protein antibody-conjugated ZnPc-UCNPs. Blue fluorescence in (<b>a</b>) showed DAPI-stained cell nuclei. Green fluorescence in (<b>b</b>) showed FITC-staining of DENV2-infected cells. Red fluorescence in (<b>c</b>) showed the location of antibody-conjugated ZnPc-UCNs. (<b>d</b>) Kaplan-Meier survival curve of day 1-2 BALB/c suckling mice that were inoculated with photodynamic-inactivated DENV2. The results showed that the UCN-based PDT system can eradicate Dengue virus pathogenesis in BALB/c mice. Reproduced with permission from [<a href="#B50-nanomaterials-08-00344" class="html-bibr">50</a>]. Copyright Elsevier, 2012.</p> Full article ">Figure 9
<p>In vivo PDT of injected tumor cells prelabeled with mesoporous-silica–coated UCNPs co-loaded with ZnPc and MC540 photosensitizers. (Excitation by a single wavelength light at 980 nm) (<b>a</b>) Representative photos of a mouse showing tumors (highlighted by dashed white circles) at 14 d after treatment with the conditions described for groups 1–4. Scale bars, 10 mm; (<b>b</b>) Tumor volumes in the four treatment groups at 6, 8, 10, 12, and 14 d after treatment to determine the effectiveness of the treatment in terms of tumor cell growth inhibition; (<b>c</b>) TUNEL staining of tissue sections from the treatment groups at 24 h after treatment to determine the effectiveness of the treatment in terms of tumor cell death by apoptosis. DAPI counterstaining indicates the nuclear region, and upconversion fluorescence imaging indicates the position of the injected UCN-labeled cell (×400 magnification). Scale bar, 20 μm; (<b>d</b>) The apoptotic index charted as the percentage of TUNEL-positive apoptotic nuclei divided by the total number of nuclei visualized by counterstaining with DAPI obtained from counts of randomly chosen microscopic fields. Reproduced with permission from [<a href="#B45-nanomaterials-08-00344" class="html-bibr">45</a>]. Copyright Nature Publishing Group, 2012.</p> Full article ">
17 pages, 5325 KiB  
Article
Effect of Microwave Radiation Power on the Size of Aggregates of ZnO NPs Prepared Using Microwave Solvothermal Synthesis
by Jacek Wojnarowicz, Tadeusz Chudoba, Stanisław Gierlotka and Witold Lojkowski
Nanomaterials 2018, 8(5), 343; https://doi.org/10.3390/nano8050343 - 18 May 2018
Cited by 65 | Viewed by 5319
Abstract
This paper reports the possibility of changing the size of zinc oxide nanoparticles (ZnO NPs) aggregates through a change of synthesis parameters. The effect of the changed power of microwave heating on the properties of ZnO NPs obtained by the microwave solvothermal synthesis [...] Read more.
This paper reports the possibility of changing the size of zinc oxide nanoparticles (ZnO NPs) aggregates through a change of synthesis parameters. The effect of the changed power of microwave heating on the properties of ZnO NPs obtained by the microwave solvothermal synthesis from zinc acetate dissolved in ethylene glycol was tested for the first time. It was found that the size of ZnO aggregates ranged from 60 to 120 nm depending on the power of microwave radiation used in the synthesis of ZnO NPs. The increase in the microwave radiation power resulted in the reduction of the total synthesis time with simultaneous preservation of the constant size and shape of single ZnO NPs, which were synthesized at a pressure of 4 bar. All the obtained ZnO NPs samples were composed of homogeneous spherical particles that were single crystals with an average size of 27 ± 3 nm with a developed specific surface area of 40 m2/g and the skeleton density of 5.18 ± 0.03 g/cm3. A model of a mechanism explaining the correlation between the size of aggregates and the power of microwaves was proposed. This method of controlling the average size of ZnO NPs aggregates is presented for the first time and similar investigations are not found in the literature. Full article
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<p>SEM images of products of synthesis of ZnO NPs obtained with the microwave radiation power: (<b>a</b>,<b>d</b>) ZnO-3 kW; (<b>b</b>,<b>e</b>) ZnO-2 kW; (<b>c</b>,<b>f</b>) ZnO-1 kW.</p> Full article ">Figure 2
<p>X-ray diffraction patterns of ZnO NPs.</p> Full article ">Figure 3
<p>Crystallite size distributions of ZnO NPs obtained using Nanopowder XRD Processor Demo, pre α ver.0.0.8, © Pielaszek Research [<a href="#B66-nanomaterials-08-00343" class="html-bibr">66</a>].</p> Full article ">Figure 4
<p>Size distributions of ZnO particles/aggregates obtained by DLS method.</p> Full article ">Figure 5
<p>SEM images of ZnO NPs layers obtained on polyurethane film using the ultrasonic method from NPs: (<b>a</b>) ZnO-3 kW; (<b>b</b>) ZnO-1 kW.</p> Full article ">Figure 6
<p>Chart presenting the relation between pressure and temperature for: EG with 0.08 wt. % of H<sub>2</sub>O, EG with 1.49 wt. % of H<sub>2</sub>O and precursor (Ac)<sub>2</sub>Zn·2H<sub>2</sub>O dissolved in EG with 1.49 wt. % of H<sub>2</sub>O. Experimental data obtained in the MSS2 microwave reactor.</p> Full article ">Figure 7
<p>Charts of synthesis parameters for different microwave radiation powers: (<b>a</b>) 1 kW; (<b>b</b>) 2 kW; (<b>c</b>) 3 kW. Source: experimental data from the MSS2 reactor.</p> Full article ">Figure 8
<p>Summary of temperature growth profiles for ZnO NPs synthesis in the MSS2 reactor. Source: own data calculated based on the T = f(P) correlation, where: T—temperature, P—pressure in the reactor, f(P)—sixth-order polynomial function.</p> Full article ">Figure 9
<p>Indicative illustration of formation of ZnO NPs aggregates during the MSS.</p> Full article ">
10 pages, 2183 KiB  
Review
Doped Carbon Dots for Sensing and Bioimaging Applications: A Minireview
by Timur Sh. Atabaev
Nanomaterials 2018, 8(5), 342; https://doi.org/10.3390/nano8050342 - 18 May 2018
Cited by 171 | Viewed by 10289
Abstract
In the last decade, carbon dots (C-dots, CDs) or carbon quantum dots (CQDs) have attracted a considerable amount of attention from the scientific community as a low cost and biocompatible alternative to semiconductor quantum dots. In particular, doped C-dots have excellent fluorescent properties [...] Read more.
In the last decade, carbon dots (C-dots, CDs) or carbon quantum dots (CQDs) have attracted a considerable amount of attention from the scientific community as a low cost and biocompatible alternative to semiconductor quantum dots. In particular, doped C-dots have excellent fluorescent properties that have been successfully utilized for numerous applications. In this minireview, we overview the recent advances on the synthesis of doped C-dots derived from carbon-rich sources and their potential applications for biomedical and sensing applications. In addition, we will also discuss some challenges and outline some future perspectives of this exciting material. Full article
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<p>Number of published works according to the Scopus search (keyword “carbon dots”).</p> Full article ">Figure 2
<p>UV–vis absorption (UV), PL excitation (PLE), and PL emission (PL) spectra of doped C-dots. Reprinted with permission from reference [<a href="#B15-nanomaterials-08-00342" class="html-bibr">15</a>].</p> Full article ">Figure 3
<p>(<b>a</b>) The emission spectra of sulfur-doped C-dots in the presence of Fe(III) at different concentrations; (<b>b</b>) the fluorescence quenching (selectivity) of sulfur-doped C-dots in the presence of different metal ions. Reprinted with permission from reference [<a href="#B26-nanomaterials-08-00342" class="html-bibr">26</a>].</p> Full article ">Figure 4
<p>(<b>A</b>) The emission spectra of boron-doped C-dots in the presence of H<sub>2</sub>O<sub>2</sub> at different concentrations; (<b>B</b>) the fluorescence response of boron-doped C-dots to the H<sub>2</sub>O<sub>2</sub> at different concentrations. Reprinted with permission from reference [<a href="#B47-nanomaterials-08-00342" class="html-bibr">47</a>].</p> Full article ">Figure 5
<p>Confocal microscopy images of L929 cells incubated with C-dots under different excitation wavelengths. Reprinted with permission from reference [<a href="#B58-nanomaterials-08-00342" class="html-bibr">58</a>].</p> Full article ">Figure 6
<p>In vivo fluorescence images of C-dots injected into nude mouse. Reprinted with permission from reference [<a href="#B60-nanomaterials-08-00342" class="html-bibr">60</a>].</p> Full article ">Figure 7
<p>(<b>A</b>) T<sub>1</sub>-weighted relaxivity rates of Gd-doped C-dots and Gd-DTPA as a function of Gd<sup>3+</sup> concentration; (<b>B</b>) MRI images of (a) Gd-doped C-dots; and (b) C-Gd-DTPA taken at different concentrations. Reprinted with permission from reference [<a href="#B65-nanomaterials-08-00342" class="html-bibr">65</a>].</p> Full article ">
9 pages, 2009 KiB  
Article
The Effect of Light Intensity, Temperature, and Oxygen Pressure on the Photo-Oxidation Rate of Bare PbS Quantum Dots
by Huiyan Liu, Qian Dong and Rene Lopez
Nanomaterials 2018, 8(5), 341; https://doi.org/10.3390/nano8050341 - 18 May 2018
Cited by 11 | Viewed by 5166
Abstract
The oxidation speed of PbS quantum dots has been a subject of controversy for some time. In this study, we reveal the precise functional form of the oxidation rate constant for bare quantum dots through analysis of their photoluminescence as a function of [...] Read more.
The oxidation speed of PbS quantum dots has been a subject of controversy for some time. In this study, we reveal the precise functional form of the oxidation rate constant for bare quantum dots through analysis of their photoluminescence as a function of temperature, oxygen pressure, and excitation-laser intensity. The combined effect of these factors results in a reduced energy barrier that allows the oxidation to proceed at a high rate. Each absorbed photon is found to have a 10−8 probability of oxidizing a PbS atomic pair. This highlights the importance of photo-excitation on the speed of the oxidation process, even at low illumination conditions. The procedure used here may set up a quantitative standard useful for characterizing the stability of quantum dots coated with ligands/linkers, and to compare different protection schemes in a fair quantitative way. Full article
(This article belongs to the Special Issue Nanomaterials for Renewable and Sustainable Energy)
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<p>(<b>a</b>) Initial photoluminescence (PL) spectra of PLD-deposited PbS QDs with different number of laser shots (N<sub>LP</sub>). PL of the PbS QDs shows clearly red shift from 680 to 820 nm. This obvious shift is a consequence of the quantum size effects of the PbS QDs [<a href="#B16-nanomaterials-08-00341" class="html-bibr">16</a>]; (<b>b</b>) XRD pattern of PbS QDs deposited with N<sub>LP</sub> = 500; (<b>c</b>) TEM image of PbS QDs deposited directly onto carbon-filmed-grids; the inset in (<b>c</b>) is their TEM diffraction pattern.</p> Full article ">Figure 2
<p>(<b>a</b>) Typical of the photoluminescence spectrum for the PbS QDs, all the experiments presented similar behavior but with marked time differences depending on the exact environmental conditions. (<b>b</b>–<b>d</b>) XPS Pb 4f<sub>7/2</sub> spectrum of the freshly deposited, after laser-irradiation until reached maximum PL intensity, and after PL intensity decayed, respectively. The XPS measurement was conducted using a ThermoFisher ESCALAB 250XI Analyzer with base pressure below 10<sup>−10</sup> mbar. Al Kα (1486.6 eV) radiation was used as an X-ray source (15 kV, 159.3 W).</p> Full article ">Figure 3
<p>Time evolution of the photoluminescence integrated intensity for the PbS QDs, under three distinct experimental conditions: (<b>a</b>) Variation over laser power with 1 atmosphere of oxygen pressure and constant temperature (294 K), (<b>b</b>) variation under different oxygen pressures at room temperature and 1.54 × 10<sup>4</sup> W/cm<sup>2</sup> light intensity, and (<b>c</b>) temperature effect at constant pressure (1 atmosphere) and same constant laser power. Solid lines are fit to the physical model described in the text.</p> Full article ">Figure 4
<p>(<b>a</b>,<b>b</b>) parameters A and B under different light intensities at 294 K and 1 atmosphere of oxygen, respectively; (<b>c</b>) Parameter B as function of pressure at 294 K and 1.54 × 10<sup>4</sup> W/cm<sup>2</sup> light intensity; (<b>d</b>) Parameter B as function of temperature at 1 atmosphere and same light intensity. Dots are the specific parameters that produce the fitted curves in <a href="#nanomaterials-08-00341-f003" class="html-fig">Figure 3</a>. Solid lines are best fits to funcional forms of those parameters vs. the controlled enviromental variables as explained in detail in the Discussion section.</p> Full article ">
12 pages, 7299 KiB  
Article
Wetting Behaviors of a Nano-Droplet on a Rough Solid Substrate under Perpendicular Electric Field
by Fenhong Song, Long Ma, Jing Fan, Qicheng Chen, Lihui Zhang and Ben Q. Li
Nanomaterials 2018, 8(5), 340; https://doi.org/10.3390/nano8050340 - 17 May 2018
Cited by 31 | Viewed by 6275
Abstract
Molecular dynamic simulations were adopted to study the wetting properties of nanoscale droplets on rough silicon solid substrate subject to perpendicular electric fields. The effect of roughness factor and electric field strength on the static and dynamic wetting behaviors of a nano-droplet on [...] Read more.
Molecular dynamic simulations were adopted to study the wetting properties of nanoscale droplets on rough silicon solid substrate subject to perpendicular electric fields. The effect of roughness factor and electric field strength on the static and dynamic wetting behaviors of a nano-droplet on a solid surface was investigated at the molecular level. Results show that the static contact angle tends to decrease slightly and show small difference with the increase of roughness factor, while it shows an obvious increase for the ramp-shaped surface because the appearing bottom space reduces the wettability of solid surface. Additionally, under the electric field, a nano-droplet was elongated in the field direction and the equilibrium contact angle increases with the increase of electric field strength. The nano-droplet was completely stretched to be column-shaped at a threshold value of the field. Besides, accompanied by the shape variation of water droplets, the molecular dipole orientations of water molecules experience a remarkable change from a random disordered distribution to an ordered profile because of the realignment of water molecules induced by electric fields. Full article
(This article belongs to the Special Issue Wetting of Nanostructured Materials)
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<p>The initial structure of water droplet and substrate with molecularly rough surface.</p> Full article ">Figure 2
<p>The snapshots in equilibrium state and time-averaged density profiles of nano-droplet on substrate with (<b>a</b>) flat-shaped, (<b>b</b>) staircase-shaped, (<b>c</b>) fence-shaped, (<b>d</b>) jagged-shaped, (<b>e</b>) ramp-shaped and (<b>f</b>) sine-shaped rough surface</p> Full article ">Figure 3
<p>Distribution of the static contact angle of nano-droplet on rough substrate.</p> Full article ">Figure 4
<p>Snapshots and time-averaged density distributions of water nano-droplet in equilibrium state on silicon substrate with (<b>a</b>) flat-shaped, (<b>b</b>) staircase-shaped, (<b>c</b>) fence-shaped, (<b>d</b>) jagged-shaped, (<b>e</b>) sine-shaped and (<b>f</b>) ramp-shaped rough surface (<span class="html-italic">E<sub>y</sub></span> = 0.9 V/nm)</p> Full article ">Figure 5
<p>Equilibrium snapshot of water nano-droplet on silicon substrate (ramp-shaped surface) under electric field (<span class="html-italic">E<sub>y</sub></span> = 0.1, 0.2, 0.5, 0.75, 0.8, 0.9 V/nm).</p> Full article ">Figure 6
<p>(<b>a</b>) Equilibrium contact angle and (<b>b</b>) the height of water nano-droplet on silicon substrate (ramp-shaped surface) under different electric fields.</p> Full article ">Figure 7
<p>Snapshot of dynamic wetting of the water nano-droplet on silicon substrate (fence-shaped surface) under electric field <span class="html-italic">E<sub>y</sub></span> = 0.9 V/nm.</p> Full article ">Figure 8
<p>Snapshot of dynamic wetting of the water nano-droplet on silicon substrate (sine-shaped surface) under electric field <span class="html-italic">E<sub>y</sub></span> = 1.0 V/nm.</p> Full article ">Figure 9
<p>Dynamic contact angles of water nanodroplet on rough silicon substrate under electric field; (<b>a</b>) For fence-shaped surface <span class="html-italic">E<sub>y</sub></span> = 0.9 V/nm; (<b>b</b>) For sine-shaped surface <span class="html-italic">E<sub>y</sub></span> = 1.0 V/nm.</p> Full article ">Figure 10
<p>Average number of hydrogen bonds per water molecule under different electric fields.</p> Full article ">Figure 11
<p>Distribution of average polarizations of water molecules under different electric field.</p> Full article ">
12 pages, 1423 KiB  
Article
pH-Responsive Mercaptoundecanoic Acid Functionalized Gold Nanoparticles and Applications in Catalysis
by Siyam M. Ansar, Saptarshi Chakraborty and Christopher L. Kitchens
Nanomaterials 2018, 8(5), 339; https://doi.org/10.3390/nano8050339 - 17 May 2018
Cited by 42 | Viewed by 8649
Abstract
Mercaptoundecanoic acid (MUA) functionalized gold nanoparticles (AuNP-MUA) were synthesized and demonstrated to possess pH-triggered aggregation and re-dispersion, as well as the capability of phase transfer between aqueous and organic phases in response to changes in pH. The pH of aggregation for AuNP-MUA is [...] Read more.
Mercaptoundecanoic acid (MUA) functionalized gold nanoparticles (AuNP-MUA) were synthesized and demonstrated to possess pH-triggered aggregation and re-dispersion, as well as the capability of phase transfer between aqueous and organic phases in response to changes in pH. The pH of aggregation for AuNP-MUA is consistent with the pKa of MUA (pH ~4) in solution, while AuNP-MUA phase transition between aqueous and organic phases occurs at pH ~9. The ion pair formation between the amine group in octadecylamine (ODA), the carboxylate group in MUA, and the hydrophobic alkyl chain of ODA facilitates the phase transfer of AuNP-MUA into an organic medium. The AuNP-MUA were investigated as a reusable catalyst in the catalytic reduction of 4-nitrophenol by borohydride—a model reaction for AuNPs. It was determined that 100% MUA surface coverage completely inhibits the catalytic activity of AuNPs. Decreasing the surface coverage was shown to increase catalytic activity, but this decrease also leads to decreased colloidal stability, recoverability, and reusability in subsequent reactions. At 60% MUA surface coverage, colloidal stability and catalytic activity were achieved, but the surface coverage was insufficient to enable redispersion following pH-induced recovery. A balance between AuNP colloidal stability, recoverability, and catalytic activity with reusability was achieved at 90% MUA surface coverage. The AuNP-MUA catalyst can also be recovered at different pH ranges depending on the recovery method employed. At pH ~4, protonation of the MUA results in reduced surface charge and aggregation. At pH ~9, ODA will form an ion-pair with the MUA and induce phase transfer into an immiscible organic phase. Both the pH-triggered aggregation/re-dispersion and aqueous/organic phase transfer methods were employed for catalyst recovery and reuse in subsequent reactions. The ability to recover and reuse the AuNP-MUA catalyst by two different methods and different pH regimes is significant, based on the fact that nanoparticle-catalyzed reactions may occur under different pH conditions. Full article
(This article belongs to the Special Issue Synthesis of Ligand-Capped Nanoparticles for Catalysis)
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<p>(<b>A</b>) Photographs showing the reversibility of 13-nm mercaptoundecanoic acid functionalized gold nanoparticles (AuNP-MUA) clustering/re-dispersion by changing the pH of the medium. The left vial (a) contains well-dispersed AuNP-MUA at a basic pH, and the right vial (b) contains aggregated and settled AuNP-MUA at an acidic pH; (<b>B</b>) Plot showing the pH-triggered reversibility of aggregation and re-dispersion monitored by the localized surface plasmon resonance (LSPR) peak intensity at 525 nm for 13-nm AuNP-MUA; and (<b>C</b>) normalized UV-VIS absorbance peak ratio of aggregated and unaggregated AuNP-MUA as a function of aqueous phase pH. The absorbance for un-aggregated 5, 13, and 45 nm diameter AuNPs were measured at wavelengths of 522, 525, and 551 nm, respectively, and the absorbance for aggregated 5, 13, and 45 AuNPs were measured at wavelengths of 562, 595, and 725 nm, respectively.</p> Full article ">Figure 2
<p>(<b>A</b>) Hydrodynamic diameter of the AuNP-MUA as a function of pH; and (<b>B</b>) ζ-potential of the AuNP-MUA as a function of pH. The red line indicates the onset of AuNP-MUA aggregation based on the hydrodynamic diameter data from figure A.</p> Full article ">Figure 3
<p>(<b>A</b>) Photographs of the pH-triggered reversible phase transfer of 13-nm AuNP-MUA between water and CHCl<sub>3</sub> layers, by switching the pH. The left side vial contains well-dispersed AuNP-MUA in the aqueous phase (top layer) at basic pH, and the right side vial contains AuNP-MUA transferred into the CHCl<sub>3</sub> phase (bottom) layer after adding HCl and vigorous shaking; (<b>B</b>) Plot showing pH-triggered reversible phase transfer of 13 nm AuNP-MUA between the water and organic phase, by monitoring the AuNP-MUA LSPR peak intensity at 525 nm wavelength in aqueous phase; and (<b>C</b>) absorbance of AuNP-MUA in aqueous phase at 525 nm (left scale) versus the pH and percentage transfer of AuNP-MUA from an aqueous to a CHCl<sub>3</sub> layer as a function of pH. The percentage of transfer was calculated by taking the absorbance of the AuNP-MUA (in aqueous medium) at pH 11.0 as 0%. The red color solid curve represents sigmoidal fitting of the experimental data.</p> Full article ">Figure 4
<p>Catalytic activity of AuNP-MUA as function of MUA packing density on AuNPs. (<b>A</b>) Time-resolved UV-VIS spectra of 4-nitrophenol (4-NP) reduction reaction catalyzed by AuNPs functionalized with 0 µM MUA; (<b>B</b>) Time-resolved UV-VIS spectra of 4-nitrophenol reduction reaction catalyzed by AuNPs and functionalized with 10 µM MUA; and (<b>C</b>) The progress of the reaction tracked by the change in 4-NP absorbance peak at 400 nm over the time.</p> Full article ">Figure 5
<p>Recovery and reuse of AuNP-MUA with 90% surface coverage in catalysis by using (<b>A</b>) pH-triggered aggregation/redispersion method and (<b>B</b>) pH-triggered phase transformation method.</p> Full article ">
13 pages, 6298 KiB  
Article
Effective NiMn Nanoparticles-Functionalized Carbon Felt as an Effective Anode for Direct Urea Fuel Cells
by Nasser A. M. Barakat, Mohannad Alajami, Zafar Khan Ghouri and Saeed Al-Meer
Nanomaterials 2018, 8(5), 338; https://doi.org/10.3390/nano8050338 - 16 May 2018
Cited by 19 | Viewed by 4388
Abstract
The internal resistances of fuel cells strongly affect the generated power. Basically, in the fuel cell, the anode can be prepared by deposition of a film from the functional electrocatalyst on a proper gas diffusion layer. Accordingly, an interfacial resistance for the electron [...] Read more.
The internal resistances of fuel cells strongly affect the generated power. Basically, in the fuel cell, the anode can be prepared by deposition of a film from the functional electrocatalyst on a proper gas diffusion layer. Accordingly, an interfacial resistance for the electron transport is created between the two layers. Electrocatalyst-functionalized gas diffusion layer (GDL) can distinctly reduce the interfacial resistance between the catalyst layer and the GDL. In this study, NiMn nanoparticles-decorated carbon felt is introduced as functionalized GDL to be exploited as a ready-made anode in a direct urea fuel cell. The proposed treated GDL was prepared by calcination of nickel acetate/manganese acetate-loaded carbon felt under an argon atmosphere at 850 °C. The physiochemical characterizations confirmed complete reduction for the utilized precursors and deposition of pristine NiMn nanoparticles on the carbon felt fiber. In passive direct urea fuel cells, investigation the performance of the functionalized GDLs indicated that the composition of the metal nanoparticles has to be optimized as the GDL obtained from 40 wt % manganese acetate reveals the maximum generated power density; 36 mW/m2 at room temperature and 0.5 M urea solution. Moreover, the electrochemical measurements proved that low urea solution concentration is preferred as utilizing 0.5 M solution resulted into generating higher power compared to 1.0 and 2.0 M solution. Overall, this study opens a new avenue toward functionalization of the GDL as a novel strategy to overcome the interfacial resistance between the electrocatalyst and the GDL. Full article
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<p>XRD patterns for two treated carbon felt sheets.</p> Full article ">Figure 2
<p>Two magnifications SEM images for the treated carbon felt sheet after the calcination process; sample 40 wt % MnAc.</p> Full article ">Figure 3
<p>EDX result for the treated carbon felt using 40 wt % MnAc as an initial precursor.</p> Full article ">Figure 4
<p>Activation of the NiMn-based electrocatalyst in 1.0 M KOH solution at scan rate of 0.05 V/s.</p> Full article ">Figure 5
<p>Polarization; (<b>A</b>) and power density; (<b>B</b>) curves of DUFC at room temperature with 0.5 M urea as fuel using functionalized carbon felt at different metal nanoparticles composition as anode.</p> Full article ">Figure 5 Cont.
<p>Polarization; (<b>A</b>) and power density; (<b>B</b>) curves of DUFC at room temperature with 0.5 M urea as fuel using functionalized carbon felt at different metal nanoparticles composition as anode.</p> Full article ">Figure 6
<p>Polarization; (<b>A</b>) and power density; (<b>B</b>) curves of DUFC at room temperature with 1.0 M urea as fuel using functionalized carbon felt at different metal nanoparticles composition as anode.</p> Full article ">Figure 7
<p>Polarization; (<b>A</b>) and power density; (<b>B</b>) curves of DUFC at room temperature with 2.0 M urea as fuel using functionalized carbon felt at different metal nanoparticles composition as anode.</p> Full article ">Figure 8
<p>Influence of the metal nanoparticles composition on the obtained cell potential; (<b>A</b>) and generated power; (<b>B</b>) from direct urea fuel cells using 0.5, 1.0 and 2.0 M urea solutions at room temperature.</p> Full article ">Figure 8 Cont.
<p>Influence of the metal nanoparticles composition on the obtained cell potential; (<b>A</b>) and generated power; (<b>B</b>) from direct urea fuel cells using 0.5, 1.0 and 2.0 M urea solutions at room temperature.</p> Full article ">
16 pages, 8858 KiB  
Review
Periodontal Tissues, Maxillary Jaw Bone, and Tooth Regeneration Approaches: From Animal Models Analyses to Clinical Applications
by Fareeha Batool, Marion Strub, Catherine Petit, Isaac Maximiliano Bugueno, Fabien Bornert, François Clauss, Olivier Huck, Sabine Kuchler-Bopp and Nadia Benkirane-Jessel
Nanomaterials 2018, 8(5), 337; https://doi.org/10.3390/nano8050337 - 16 May 2018
Cited by 41 | Viewed by 5970
Abstract
This review encompasses different pre-clinical bioengineering approaches for periodontal tissues, maxillary jaw bone, and the entire tooth. Moreover, it sheds light on their potential clinical therapeutic applications in the field of regenerative medicine. Herein, the electrospinning method for the synthesis of polycaprolactone (PCL) [...] Read more.
This review encompasses different pre-clinical bioengineering approaches for periodontal tissues, maxillary jaw bone, and the entire tooth. Moreover, it sheds light on their potential clinical therapeutic applications in the field of regenerative medicine. Herein, the electrospinning method for the synthesis of polycaprolactone (PCL) membranes, that are capable of mimicking the extracellular matrix (ECM), has been described. Furthermore, their functionalization with cyclosporine A (CsA), bone morphogenetic protein-2 (BMP-2), or anti-inflammatory drugs’ nanoreservoirs has been demonstrated to induce a localized and targeted action of these molecules after implantation in the maxillary jaw bone. Firstly, periodontal wound healing has been studied in an induced periodontal lesion in mice using an ibuprofen-functionalized PCL membrane. Thereafter, the kinetics of maxillary bone regeneration in a pre-clinical mouse model of surgical bone lesion treated with BMP-2 or BMP-2/Ibuprofen functionalized PCL membranes have been analyzed by histology, immunology, and micro-computed tomography (micro-CT). Furthermore, the achievement of innervation in bioengineered teeth has also been demonstrated after the co-implantation of cultured dental cell reassociations with a trigeminal ganglia (TG) and the cyclosporine A (CsA)-loaded poly(lactic-co-glycolic acid) (PLGA) scaffold in the jaw bone. The prospective clinical applications of these different tissue engineering approaches could be instrumental in the treatment of various periodontal diseases, congenital dental or cranio-facial bone anomalies, and post-surgical complications. Full article
(This article belongs to the Special Issue Preparation and Application of Hybrid Nanomaterials)
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<p>Scanning electron microscopy (SEM) observations of non-functionalized PCL scaffolds consisting of non-woven electrospun nanofibers (<b>A</b>), PCL scaffolds grafted with CsA-loaded PLGA nanoparticles (chitosan/PLGA/CsA)<sub>5</sub> (<b>B</b>), with BMP-2/Ibuprofen (PCL/(BMP-2)<sub>3</sub>/(Ibu)<sub>3</sub>) nanoreservoirs (<b>C</b>) or with Ibuprofen (<b>D</b>). For the morphological study by SEM, the different scaffolds were fixed with 4% paraformaldehyde, dehydrated in successive baths of ethanol (25, 50, 75, 90, 100%) and treated with hexamethyldisilazane (HDMS). They were mounted on a supporting sample holder using carbon conductive adhesive, then, silver-coated and observed with a Philips XL-30 ESEM scanning electron microscope in conventional mode (high vacuum) with a Everhart-Thornley secondary electron detector.</p> Full article ">Figure 2
<p>Periodontitis induced with <span class="html-italic">Porphyromonas gingivalis</span>-infected ligatures and treatment with PCL/Ibu membrane (<b>A</b>–<b>D</b>). (<b>B</b>) sulcular incision along the first and second maxillary molars, (<b>C</b>) raising the flaps for exposure and access, (<b>D</b>) surgical placement of PCL/Ibu membrane on the periodontal lesion, (<b>E</b>–<b>N</b>) histological view at 7 and 15 days. (<b>E</b>–<b>K</b>) histology of periodontal wound healing at 7 days and (<b>L</b>–<b>N</b>) at 15 days. Red line = cementoenamel junction, blue line = fibrous connective tissue attachment, green line = epithelial attachment, yellow line = bone level. After anesthesia, a slight incision to the bone crest contact was made to facilitate the first ligature placement at the junction between the gum and the tooth along the first and second molars (M1-M2) as previously described [<a href="#B16-nanomaterials-08-00337" class="html-bibr">16</a>]. The thread was then blocked with a drop of glass ionomer (Fuji IIGC, GC, France, Bonneuil sur Marne, France). Sterilized black braided 6.0 silk threads (Ethicon, Auneau, France) were incubated in culture medium containing <span class="html-italic">P.gingivalis</span> in an anaerobic chamber for one day. <span class="html-italic">P.gingivalis</span>-soaked ligatures were placed around maxillary first and second molars. The ligatures were inspected and replaced (with freshly infected ones) thrice a week for a period of 40 days. An incision was performed along the sulcular margins of the first and second molars and extended anteriorly on the mesial aspect of the first molar to efficiently raise the flap to gain access. Ibuprofen-functionalized PCL membrane was punched with a 3 mm diameter cutter. The circular pieces of membrane were further divided into half to achieve a size appropriate enough to cover the lesion. The cut membrane was then placed into the periodontal pocket after raising the flap such that the membrane stays flat beneath the flap covering the lesion fully and the necks of the crowns (molars) partially, entering the inter-dental area as well. The flap was nicely repositioned to perform a suture on the flap while maintaining the membrane underneath [<a href="#B16-nanomaterials-08-00337" class="html-bibr">16</a>]. AB: alveolar bone, CT: connective tissue, EPI: epithelium, PL: periodontal ligament, R: root. Stars showing PCL/Ibu membrane.</p> Full article ">Figure 3
<p>Surgical bone defect model and treatment with PCL/Ibu membrane (<b>A</b>–<b>I</b>). (<b>A</b>–<b>E</b>) demonstrate the surgical procedure for creating the mesial bone defect. After anesthesia, sulcular incision (<b>A</b>) was given along maxillary first molar and extended anteriorly on the mesial aspect of the first molar for efficient raising of palatal and vestibular flaps so that they do not hinder the bone drilling procedure. The exposed bone was drilled to create the intrabony defect (<b>B</b>). The bone over and around the mesial root of the first molar was removed. Constant irrigation with physiological saline was maintained to avoid overheating of the bur and the bone area concerned. The drilled bone was, later, nicely irrigated, cleaned, and dried to remove all the bone chips and debris. PCL/Ibu functionalized membrane was placed on the created bone lesion (<b>C</b>) in such a manner that its ends could be blocked beneath the vestibular and palatal flaps. Palatal and vestibular flaps were approximated covering the PCL/Ibu membrane underneath and sutured (9-0 ETHILON* Polyamide 6/6) or glued to retain the membrane underneath (<b>D</b>,<b>E</b>). (<b>F</b>) micro-CT view before the bony defect and (<b>G</b>) after bony defect. (<b>H</b>,<b>I</b>) Histology of periodontal wound healing at 15 days. Red line = cementoenamel junction, yellow line = bone level. (<b>I</b>) Arrow showing short epithelial attachment in test. M1: first upper molar, R: root.</p> Full article ">Figure 4
<p>Trichrome of Gomori staining (<b>A</b>–<b>C</b>,<b>G</b>–<b>I</b>) and immunofluorescence for osteocalcin (<b>D</b>–<b>F</b>,<b>J</b>–<b>L</b>) after 30 (<b>A</b>–<b>F</b>) and 90 days (<b>G</b>–<b>L</b>) implantation of PCL (<b>A</b>,<b>D</b>,<b>G</b>,<b>J</b>), PCL/(BMP-2)<sub>10</sub> (<b>B</b>,<b>E</b>,<b>H</b>,<b>K</b>) and PCL/(BMP-2)<sub>10</sub>/(Ibu)<sub>3</sub> (<b>C</b>,<b>F</b>,<b>I</b>,<b>L</b>). Arrows indicated neoformed bone positive for osteocalcin. White dots indicate the limit of the maxillary bone. For the immunofluorescence, samples were embedded in Tissue-Tek, frozen at −20 °C and sectioned (10 μm) using a cryostat (Leica, CM3000). Serial sections were rinsed with PBS, fixed for 10 min with 4% paraformaldehyde at 4 °C and treated as previously described [<a href="#B27-nanomaterials-08-00337" class="html-bibr">27</a>] using the rabbit anti-osteocalcin antibodies (Santa Cruz Biotechnology, dilution 1/200). Sections were observed with a fluorescence microscope (Leica DM4000B). G: gingiva, LBR: lesion with bone regeneration, PCL: scaffold.</p> Full article ">Figure 5
<p>Micro-CT sections (<b>A</b>,<b>C</b>,<b>E</b>,<b>G</b>,<b>C’</b>,<b>E’</b>,<b>G’</b>) and 3D reconstructions (<b>B</b>,<b>D</b>,<b>F</b>,<b>H</b>) at T0 (<b>A</b>,<b>B</b>) and after 90 days of implantation of PCL (<b>C</b>,<b>D</b>,<b>C’</b>), PCL/BMP-2 (<b>E</b>,<b>F</b>,<b>E’</b>), and PCL/BMP-2/Ibu (<b>G</b>,<b>H</b>,<b>G’</b>). To study the evolution of bone response, we conducted an ex vivo longitudinal post-operative follow-up using micro-CT. The X-ray microtomography acquisitions were performed after 0 and 90 days. The size of the reconstructed isotropic voxel was 8 μm. M1: first upper molar, NC: nasal cavity.</p> Full article ">Figure 6
<p>(<b>A</b>) Different stages of the microsurgery: incision of the gingiva (<b>Aa</b>), maxillary bone lesion obtained with a dental bur (500 μm) (<b>Ab</b>), implantation of the membrane with the bioengineered tooth and TG (<b>Ac</b>), closing of the gingiva with biological glue (<b>Ad</b>), and wound healing of the mucosa two weeks after implantation (<b>Ae</b>). (<b>B</b>,<b>C</b>) Histology, vascularization and innervation of bioengineered tooth implanted on PCL scaffolds functionalized with CsA-loaded PLGA nanoparticles (chitosan/PLGA/CsA)<sub>5</sub> after two (<b>B</b>) or four (<b>C</b>) weeks of implantation. Samples were embedded in Tissue-Tek, frozen at −20 °C and sectioned (10μm) using a cryostat (Leica, CM3000). Serial sections were rinsed with PBS, fixed for 10 min with 4% paraformaldehyde at 4 °C. Some were stained with hematoxylin/eosin ((<b>Cf</b>),(<b>Ci</b>),(<b>Cj</b>)) or for the immunofluorescence as previously described using rabbit anti-peripherin (Abcam, dilution 1/600) and rat anti-CD31 (BD Pharmingen, dilution 1/100) antibodies [<a href="#B22-nanomaterials-08-00337" class="html-bibr">22</a>] ((<b>Bg</b>),(<b>Bh</b>),(<b>Ck</b>),(<b>Ci</b>)). Cell nuclei were stained with 200 nM DAPI (Sigma-Aldrich Co, Darmstadt, Germany). D: dentin, DP: dental pulp, E: enamel, M1: first upper molar, Od: odontoblasts, TG: trigeminal ganglion.</p> Full article ">
10 pages, 2180 KiB  
Article
Fabrication and Characterization of Nanoenergetic Hollow Spherical Hexanitrostibene (HNS) Derivatives
by Xiong Cao, Peng Deng, Shuangqi Hu, Lijun Ren, Xiaoxia Li, Peng Xiao and Yu Liu
Nanomaterials 2018, 8(5), 336; https://doi.org/10.3390/nano8050336 - 16 May 2018
Cited by 23 | Viewed by 4443
Abstract
The spherization of nanoenergetic materials is the best way to improve the sensitivity and increase loading densities and detonation properties for weapons and ammunition, but the preparation of spherical nanoenergetic materials with high regularization, uniform size and monodispersity is still a challenge. In [...] Read more.
The spherization of nanoenergetic materials is the best way to improve the sensitivity and increase loading densities and detonation properties for weapons and ammunition, but the preparation of spherical nanoenergetic materials with high regularization, uniform size and monodispersity is still a challenge. In this paper, nanoenergetic hollow spherical hexanitrostibene (HNS) derivatives were fabricated via a one-pot copolymerization strategy, which is based on the reaction of HNS and piperazine in acetonitrile solution. Characterization results indicated the as-prepared reaction nanoenergetic products were HNS-derived oligomers, where a free radical copolymerization reaction process was inferred. The hollow sphere structure of the HNS derivatives was characterized by scanning electron microscopy (SEM), transmission electron microscope (TEM), and synchrotron radiation X-ray imaging technology. The properties of the nanoenergetic hollow spherical derivatives, including thermal decomposition and sensitivity are discussed in detail. Sensitivity studies showed that the nanoenergetic derivatives exhibited lower impact, friction and spark sensitivity than raw HNS. Thermogravimetric-differential scanning calorimeter (TG-DSC) results showed that continuous exothermic decomposition occurred in the whole temperature range, which indicated that nanoenergetic derivatives have a unique role in thermal applications. Therefore, nanoenergetic hollow spherical HNS derivatives could provide a new way to modify the properties of certain energetic compounds and fabricate spherical nanomaterials to improve the charge configuration. Full article
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<p>The chemical structure of the hollow spherical hexanitrostibene (HNS).</p> Full article ">Figure 2
<p>The SEM images of (<b>a</b>) raw HNS and (<b>b</b>,<b>c</b>) as-prepared samples, (<b>d</b>) the particle size distribution of spherical nanoparticles from statistical data by SEM.</p> Full article ">Figure 3
<p>(<b>a</b>–<b>d</b>) the SEM images and (<b>e</b>) the TEM image of the spherical nanoenergetic derivatives.</p> Full article ">Figure 4
<p>(<b>a</b>–<b>e</b>) A group of synchrotron radiation X-ray imaging technology images of spherical nanoenergetic derivatives.</p> Full article ">Figure 5
<p>The <sup>13</sup>C NMR of raw HNS (black), piperazine (blue) and the sample: nanoenergetic derivatives (red), using acetonitrile-d<sub>2</sub> as a deuterium reagent.</p> Full article ">Figure 6
<p>The XRD patterns of raw HNS (red), piperazine (blue) and the sample: nanoenergetic derivatives (black).</p> Full article ">Figure 7
<p>(<b>a</b>) The FT-IR patterns of raw HNS (red), piperazine (blue) and the sample: nanoenergetic derivatives (black), (<b>b</b>) Magnified FT-IR patterns from (<b>a</b>).</p> Full article ">Figure 8
<p>TG-DSC curves of the samples: (<b>a</b>) raw HNS and (<b>b</b>) nanoenergetic HNS derivatives in N<sub>2</sub> air flow and a heat rate of 10 °C min<sup>−1</sup>.</p> Full article ">
13 pages, 4060 KiB  
Article
High Performance of Supercapacitor from PEDOT:PSS Electrode and Redox Iodide Ion Electrolyte
by Xing Gao, Lei Zu, Xiaomin Cai, Ce Li, Huiqin Lian, Yang Liu, Xiaodong Wang and Xiuguo Cui
Nanomaterials 2018, 8(5), 335; https://doi.org/10.3390/nano8050335 - 16 May 2018
Cited by 33 | Viewed by 6509
Abstract
Insufficient energy density and poor cyclic stability is still challenge for conductive polymer-based supercapacitor. Herein, high performance electrochemical system has been assembled by combining poly (3,4-ethylenedioxythiophene) (PEDOT):poly (styrene sulfonate) (PSS) redox electrode and potassium iodide redox electrolyte, which provide the maximum specific capacity [...] Read more.
Insufficient energy density and poor cyclic stability is still challenge for conductive polymer-based supercapacitor. Herein, high performance electrochemical system has been assembled by combining poly (3,4-ethylenedioxythiophene) (PEDOT):poly (styrene sulfonate) (PSS) redox electrode and potassium iodide redox electrolyte, which provide the maximum specific capacity of 51.3 mAh/g and the retention of specific capacity of 87.6% after 3000 cycles due to the synergic effect through a simultaneous redox reaction both in electrode and electrolyte, as well as the catalytic activity for reduction of triiodide of the PEDOT:PSS. Full article
(This article belongs to the Special Issue Three-dimensional Nanomaterials for Energy Storage and Conversions)
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<p>(<b>a</b>) SEM of multi-walled carbon nanotubes (MWCNTs); (<b>b</b>) Composite of poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS)/MWCNTs.</p> Full article ">Figure 2
<p>XRD patterns of MWCNTs (<b>a</b>), PEDOT:PSS (<b>b</b>) and PEDOT:PSS/MWCNTs (<b>c</b>).</p> Full article ">Figure 3
<p>Electrochemical experiments data of PEDOT:PSS/MWCNTs electrodes in 1 M H<sub>2</sub>SO<sub>4</sub> and 1 M H<sub>2</sub>SO<sub>4</sub>-0.1 M KI electrolytes. (<b>a</b>) Cyclic voltammetry (CV) curves of the PEDOT:PSS/MWCNTs electrode at scan rates of 5–100 mv/s in the 1 M H<sub>2</sub>SO<sub>4</sub> electrolytes. (<b>b</b>) CV curves of the PEDOT:PSS/MWCNTs at san rates of 10 mv/s. (<b>c</b>) Nyquist plot for the PEDOT:PSS/MWCNTs electrode in different electrolytes (The inset, low-frequency region in the top right). (<b>d</b>) Nyquist plots of charge-transfer resistance (RCT) with a variety of materials. (<b>e</b>) CV curves at a scan rate of 10 mv/s. (<b>f</b>) GCD of MWCNTs, PEDOT:PSS and PEDOT:PSS/MWCNTs.</p> Full article ">Figure 4
<p>Schematics of the chemistry of the supercapacitor. The inset in the upper left corner shows the mechanism of triiodide reduction.</p> Full article ">Figure 5
<p>(<b>a</b>) CV curves recorded at 20 mV/s. (<b>b</b>) Galvanostatic charge–discharge (GCD) profiles at 1 A/g. (<b>c</b>) Calculated specific capacitance for 1 A/g at different concentration of KI. (<b>d</b>) Nyquist plot of PEDOT:PSS/MWCNTs electrodes (The inset showed high-frequency region in the top right).</p> Full article ">Figure 6
<p>The equivalent circuit for PEDOT:PSS/MWCNTs at different concentrations of KI with 1 M H<sub>2</sub>SO<sub>4</sub> electrolytes.</p> Full article ">Figure 7
<p>Electrochemical analysis and comparison investigated at 1 M H<sub>2</sub>SO<sub>4</sub>-0.1 M KI. (<b>a</b>) CV curves of the PEDOT:PSS/MWCNTs at different scan rates. (<b>b</b>) GCD profiles of the PEDOT:PSS/MWCNTs electrode at different current densities. (<b>c</b>) Comparison of specific capacitance of PEDOT:PSS/MWCNTs with reported values. (<b>d</b>) Nyquist plot of PEDOT:PSS/MWCNTs electrodes (The inset showed high-frequency region in the top right).</p> Full article ">Figure 8
<p>(<b>a</b>) Cycle life performance of the PEDOT:PSS/MWCNTs electrodes at a current density of 1 A/g with two-electrode asymmetric electrochemical system. (<b>b</b>) Nyquist plot of PEDOT:PSS/MWCNTs electrodes before and after long-term stability test.</p> Full article ">Figure 8 Cont.
<p>(<b>a</b>) Cycle life performance of the PEDOT:PSS/MWCNTs electrodes at a current density of 1 A/g with two-electrode asymmetric electrochemical system. (<b>b</b>) Nyquist plot of PEDOT:PSS/MWCNTs electrodes before and after long-term stability test.</p> Full article ">
18 pages, 3951 KiB  
Article
An Innovative Porous Nanocomposite Material for the Removal of Phenolic Compounds from Aqueous Solutions
by Antonio Turco, Anna Grazia Monteduro, Elisabetta Mazzotta, Giuseppe Maruccio and Cosimino Malitesta
Nanomaterials 2018, 8(5), 334; https://doi.org/10.3390/nano8050334 - 16 May 2018
Cited by 25 | Viewed by 4739
Abstract
Energy efficient, low-cost, user-friendly, and green methods for the removal of toxic phenolic compounds from aqueous solution are necessary for waste treatment in industrial applications. Herein we present an interesting approach for the utilization of oxidized carbon nanotubes (CNTs) in the removal of [...] Read more.
Energy efficient, low-cost, user-friendly, and green methods for the removal of toxic phenolic compounds from aqueous solution are necessary for waste treatment in industrial applications. Herein we present an interesting approach for the utilization of oxidized carbon nanotubes (CNTs) in the removal of phenolic compounds from aqueous solution. Dried pristine CNTs were stably incorporated in a solid porous support of polydimethylsiloxane (PDMS) facilitating the handling during both oxidation process of the nanomaterial and uptake of phenolic compounds, and enabling their safe disposal, avoiding expensive post-treatment processes. The adsorption studies indicated that the materials can efficiently remove phenolic compounds from water with different affinities towards different phenolic compounds. Furthermore, the adsorption kinetics and isotherms were studied in detail. The experimental data of adsorption fitted well with Langmuir and Freundlich isotherms, and pseudo-second-order kinetics, and the results indicated that the adsorption process was controlled by a two-step intraparticle diffusion model. The incorporation of CNTs in polymeric matrices did not affect their functionality in phenol uptake. The material was also successfully used for the removal of phenolic compounds from agricultural waste, suggesting its possible application in the treatment of wastewater. Moreover, the surface of the material could be regenerated, decreasing treatment costs. Full article
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<p>XPS survey spectra of PDMS/MWNT sponge before (blue curve) and after (grey curve) mild oxidation treatment.</p> Full article ">Figure 2
<p>SEM images of porous PDMS/MWNTox sponge at different magnification (<b>a</b>–<b>c</b>). In (<b>d</b>) pore size distribution is reported.</p> Full article ">Figure 3
<p>Removal efficiency (Q%) of different phenols for PDMS/MWNT<sub>ox</sub> sponge.</p> Full article ">Figure 4
<p>Time dependent removal efficiency (%) of 4-nitrophenol by the PDMS/MWNT<sub>ox</sub> sponge (gray square), PDMS sponge (green square), and PDMS/MWNT sponge (blue triangle). The time dependent removal efficiency (%) of the phenol by the PDMS/MWNT<sub>ox</sub> sponge is also reported (red circle).</p> Full article ">Figure 5
<p>Effect of the initial 4-NP (<b>a</b>) and Ph (<b>b</b>) concentration on the removal efficiency (%).</p> Full article ">Figure 6
<p>Fitting of experimental data with Langmuir isotherm model for 4-NP (black squares) and Ph (blue circles). The table reports calculated values from Equations (3)–(5).</p> Full article ">Figure 7
<p>Fitting of experimental data with Freundlich isotherm model for 4-NP (black squares) and Ph (blue circles). The table reports calculated values from Equations (6) and (7).</p> Full article ">Figure 8
<p>Application of pseudo-first order adsorption model for the adsorption of 4-NP (black square) and phenol (blue circles) onto PDMS/MWNT<sub>ox</sub> sponges. The table reports the calculated values from Equation (8).</p> Full article ">Figure 9
<p>Application of pseudo-second order adsorption model for the adsorption of 4-NP (black square) and phenol (blue circles) onto PDMS/MWNT<sub>ox</sub> sponges. The table reports the calculated values from Equation (9).</p> Full article ">Figure 10
<p>Application of intraparticle diffusion model for the adsorption of 4-NP (black square) and phenol (blue circles) onto PDMS/MWNT<sub>ox</sub> sponges. The table reports the calculated values from Equation (10).</p> Full article ">Scheme 1
<p>Schematic representation of the preparation of the polydimethylsiloxane (PDMS)-multiwalled carbon nanotube (MWNT) sponge, and photograph of the as-obtained material.</p> Full article ">
10 pages, 14171 KiB  
Article
High-Efficiency Visible Transmitting Polarizations Devices Based on the GaN Metasurface
by Zhongyi Guo, Haisheng Xu, Kai Guo, Fei Shen, Hongping Zhou, Qingfeng Zhou, Jun Gao and Zhiping Yin
Nanomaterials 2018, 8(5), 333; https://doi.org/10.3390/nano8050333 - 15 May 2018
Cited by 42 | Viewed by 5600
Abstract
Metasurfaces are capable of tailoring the amplitude, phase, and polarization of incident light to design various polarization devices. Here, we propose a metasurface based on the novel dielectric material gallium nitride (GaN) to realize high-efficiency modulation for both of the orthogonal linear polarizations [...] Read more.
Metasurfaces are capable of tailoring the amplitude, phase, and polarization of incident light to design various polarization devices. Here, we propose a metasurface based on the novel dielectric material gallium nitride (GaN) to realize high-efficiency modulation for both of the orthogonal linear polarizations simultaneously in the visible range. Both modulated transmitted phases of the orthogonal linear polarizations can almost span the whole 2π range by tailoring geometric sizes of the GaN nanobricks, while maintaining high values of transmission (almost all over 90%). At the wavelength of 530 nm, we designed and realized the beam splitter and the focusing lenses successfully. To further prove that our proposed method is suitable for arbitrary orthogonal linear polarization, we also designed a three-dimensional (3D) metalens that can simultaneously focus the X-, Y-, 45°, and 135° linear polarizations on spatially symmetric positions, which can be applied to the linear polarization measurement. Our work provides a possible method to achieve high-efficiency multifunctional optical devices in visible light by extending the modulating dimensions. Full article
(This article belongs to the Special Issue Optoelectronic Nanodevices)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic of the designed unit cell: <span class="html-italic">p</span> = 260 nm, <span class="html-italic">d</span> = 300 nm, and <span class="html-italic">h</span> = 800 nm.</p> Full article ">Figure 2
<p>Transmitted light normalization: (<b>a</b>) Transmittance variation for gallium nitride (GaN) nanobricks on Al<sub>2</sub>O<sub>3</sub> substrate, and (<b>b</b>) phase as a function of <span class="html-italic">l</span> and <span class="html-italic">w</span> for normal incidence of the <span class="html-italic">X</span>-polarized light. (<b>c</b>,<b>d</b>) The normalized transmittance and phase as a function of <span class="html-italic">l</span> and <span class="html-italic">w</span> for normal incidence of the <span class="html-italic">Y</span>-polarized light, respectively.</p> Full article ">Figure 3
<p>(<b>a</b>) The normalized transmittance and the phase of transmitted light through the eight unit cells for the <span class="html-italic">X</span>- and <span class="html-italic">Y</span>-polarized light incidences at wavelength of 530 nm. The inset in (<b>a</b>) is a supercell composed of eight unit cells. (<b>b</b>,<b>c</b>) The electric field distributions for <span class="html-italic">X</span>- and <span class="html-italic">Y</span>-polarized light, respectively; it can be clearly seen that <span class="html-italic">X</span>- and <span class="html-italic">Y</span>-polarized light is refracted into two different directions.</p> Full article ">Figure 4
<p>The transmittance of <span class="html-italic">X</span>- and <span class="html-italic">Y</span>-polarized light as a function of deflection angle (θ) under 45° polarized light incident on the bottom.</p> Full article ">Figure 5
<p>The distribution of transmitted intensities (|<span class="html-italic">E</span>|<sup>2</sup>) under the linear polarization states of incident light are (<b>a</b>) 0°, (<b>b</b>) 30°, (<b>c</b>) 42°, (<b>d</b>) 45°, (<b>e</b>) 60°, and (<b>f</b>) 90°. The white solid and dashed lines are the intensity distribution curve and the position of focal plane.</p> Full article ">Figure 6
<p>Schematic of the structure array of the designed 3D metalens.</p> Full article ">Figure 7
<p>The distributions of transmitted intensities (|<span class="html-italic">E</span>|<sup>2</sup>) in the focusing plane (<span class="html-italic">X–Y</span>) under (<b>a</b>) <span class="html-italic">X</span>-, (<b>b</b>) <span class="html-italic">Y</span>-, (<b>c</b>) 45°, (<b>d</b>) 135°, (<b>e</b>) 30°and (<b>f</b>) 60° linear-polarized incidences.</p> Full article ">Figure 8
<p>The transmitted intensity (|<span class="html-italic">E</span>|<sup>2</sup>) profiles in focal plane at (<b>a</b>) <span class="html-italic">y</span> = −1560 nm and (<b>b</b>) <span class="html-italic">x</span> = −2080 nm under the incidence of 45° linear-polarized light.</p> Full article ">
11 pages, 3398 KiB  
Article
Self-Assembled Ag-Cu2O Nanocomposite Films at Air-Liquid Interfaces for Surface-Enhanced Raman Scattering and Electrochemical Detection of H2O2
by Li Wang, Huan Qi, Lei Chen, Yantao Sun and Zhuang Li
Nanomaterials 2018, 8(5), 332; https://doi.org/10.3390/nano8050332 - 15 May 2018
Cited by 9 | Viewed by 4393
Abstract
We employ a facile and novel route to synthesize multifunctional Ag-Cu2O nanocomposite films through the self-assembly of nanoparticles at an air-liquid interface. In the ethanol-water phase, AgNO3 and Cu(NO3)2 were reduced to Ag-Cu2O nanoparticles by [...] Read more.
We employ a facile and novel route to synthesize multifunctional Ag-Cu2O nanocomposite films through the self-assembly of nanoparticles at an air-liquid interface. In the ethanol-water phase, AgNO3 and Cu(NO3)2 were reduced to Ag-Cu2O nanoparticles by NaBH4 in the presence of cinnamic acid. The Ag-Cu2O nanoparticles were immediately trapped at the air-liquid interface to form two-dimensional nanocomposite films after the reduction reaction was finished. The morphology of the nanocomposite films could be controlled by the systematic regulation of experimental parameters. It was found that the prepared nanocomposite films serving as the substrates exhibited strong surface-enhanced Raman scattering (SERS) activity. 4-aminothiophenol (4-ATP) molecules were used as the test probes to examine the SERS sensitivity of the nanocomposite films. Moreover, the nanocomposite films synthesized by our method showed enhanced electrocatalytic activity towards hydrogen peroxide (H2O2) and therefore could be utilized to fabricate a non-enzymatic electrochemical H2O2 sensor. Full article
(This article belongs to the Special Issue Synthesis, Structure and Applications of 2D Nanomaterials)
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<p>Photograph of the 2D Ag-Cu<sub>2</sub>O nanocomposite film formed at the air-liquid interface (Marked with white rectangle).</p> Full article ">Figure 2
<p>SEM images of the Ag-Cu<sub>2</sub>O nanocomposite films prepared by adjusting the concentration of CA as (<b>a</b>) 1 mM; (<b>b</b>) 3 mM; (<b>c</b>) 9.6 mM; (<b>d</b>) EDS analysis of (<b>b</b>).</p> Full article ">Figure 3
<p>XPS spectra of (<b>a</b>) Ag 3d and (<b>b</b>) Cu 2p of the as-prepared Ag-Cu<sub>2</sub>O nanocomposite film, and (<b>c</b>) Cu 2p of the Cu<sub>2</sub>O nanoparticle film.</p> Full article ">Figure 4
<p>(<b>A</b>) SERS spectra of 4-ATP on different Ag-Cu<sub>2</sub>O nanocomposite films obtained by tuning the concentration of CA as (a) 1 mM, (b) 3 mM, and (c) 9.6 mM; (<b>B</b>) The normal Raman spectra of solid 4-ATP.</p> Full article ">Figure 5
<p>SERS spectra of 4-ATP on the Ag-Cu<sub>2</sub>O nanocomposite films prepared by adjusting the molar ratio of AgNO<sub>3</sub> to Cu(NO<sub>3</sub>)<sub>2</sub>; (a) 3:1, (b) 1:1, and (c) 1:3.</p> Full article ">Figure 6
<p>SEM images of the Ag-Cu<sub>2</sub>O nanocomposite films prepared by tuning the molar ratio of AgNO<sub>3</sub> to Cu(NO<sub>3</sub>)<sub>2</sub>; (<b>a</b>) 1:1 and (<b>b</b>) 1:3.</p> Full article ">Figure 7
<p>(<b>a</b>) Typical <span class="html-italic">i</span>-<span class="html-italic">t</span> response curve of nanocomposite-film/GCE upon successive additions of different amounts of H<sub>2</sub>O<sub>2</sub> into 0.1 M PBS at −0.25 V. The inset is the early <span class="html-italic">i</span>-<span class="html-italic">t</span> response from 200 s to 900 s; (<b>b</b>) calibration curve; (<b>c</b>) selectivity of the sensor.</p> Full article ">
10 pages, 1633 KiB  
Article
Simple, Low-Cost Fabrication of Highly Uniform and Reproducible SERS Substrates Composed of Ag–Pt Nanoparticles
by Tao Wang, Juhong Zhou and Yan Wang
Nanomaterials 2018, 8(5), 331; https://doi.org/10.3390/nano8050331 - 15 May 2018
Cited by 15 | Viewed by 4337
Abstract
Ag–Pt nanoparticles, grafted on Ge wafer, were synthesized by the galvanic replacement reaction based on their different potentials. Detailed characterization through scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS) and X-ray photo-elelctron spectroscopy (XPS) proved that Ag–Pt nanoparticles are composed of large Ag [...] Read more.
Ag–Pt nanoparticles, grafted on Ge wafer, were synthesized by the galvanic replacement reaction based on their different potentials. Detailed characterization through scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS) and X-ray photo-elelctron spectroscopy (XPS) proved that Ag–Pt nanoparticles are composed of large Ag nanoparticles and many small Pt nanoparticles instead of an Ag–Pt alloy. When applied as surface-enhanced Raman scattering (SERS) substrates to detect Rhodamine 6G (1 × 10−8 M) or Crystal violet (1 × 10−7 M) aqueous solution in the line mapping mode, all of the obtained relative standard deviation (RSD) values of the major characteristic peak intensities, calculated from the SERS spectra of 100 serial spots, were less than 10%. The fabrication process of the SERS substrate has excellent uniformity and reproducibility and is simple, low-cost and time-saving, which will benefit studies on the platinum-catalyzed reaction mechanisms in situ and widen the practical application of SERS. Full article
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<p>(<b>a</b>) Low magnification and (<b>b</b>) high magnification SEM images of Ag nanoparticles grafted on the Ge wafer; (<b>c</b>) Low magnification and (<b>d</b>) high magnification SEM images of Ag–Pt nanoparticles grafted on the Ge wafer.</p> Full article ">Figure 2
<p>(<b>a</b>) XPS survey spectrum of Ag–Pt NPs/Ge; (<b>b</b>,<b>c</b>) the high solution XPS spectra of Ag 3d and Pt 4f.</p> Full article ">Figure 3
<p>Schematic illustration of the growth process of Ag–Pt NPs on the Ge wafer. (<b>a</b>) the formation of Ag nuclei; (<b>b</b>) the growth of Ag nanoparticle and (<b>c</b>) the formation of Pt nanoparticle on the surface of Ag nanoparticle.</p> Full article ">Figure 4
<p>(<b>Upper</b>): surface-enhanced Raman scattering (SERS) spectrum of 1 × 10<sup>−8</sup> M Rhodamine 6G (R6G) solution on the Ge wafer grafted with Ag–Pt nanoparticles. (<b>Lower</b>): SERS contour from line mapping of 100 spots.</p> Full article ">Figure 5
<p>Upper: the SERS spectrum of 1 × 10<sup>−7</sup> M Crystal violet (CV) solution on the Ge wafer grafted with Ag–Pt nanoparticles. Lower: the SERS contour from line mapping of 100 spots.</p> Full article ">
18 pages, 5518 KiB  
Article
Enhanced Photocatalytic Activity toward Organic Pollutants Degradation and Mechanism Insight of Novel CQDs/Bi2O2CO3 Composite
by Zisheng Zhang, Shuanglong Lin, Xingang Li, Hong Li, Tong Zhang and Wenquan Cui
Nanomaterials 2018, 8(5), 330; https://doi.org/10.3390/nano8050330 - 15 May 2018
Cited by 26 | Viewed by 5250
Abstract
Novel carbon quantum dots (CQDs) modified with Bi2O2CO3 (CQDs/Bi2O2CO3) were prepared using a simple dynamic-adsorption precipitation method. X-ray diffractometry (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and scanning electron [...] Read more.
Novel carbon quantum dots (CQDs) modified with Bi2O2CO3 (CQDs/Bi2O2CO3) were prepared using a simple dynamic-adsorption precipitation method. X-ray diffractometry (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) were used to test the material composition, structure, and band structures of the as-prepared samples. Methylene blue (MB) and colorless phenol, as target organic pollutants, were used to evaluate the photocatalytic performance of the CQDs/Bi2O2CO3 hybrid materials under visible light irradiation. Experimental investigation shows that 2–5 nm CQDs were uniformly decorated on the surface of Bi2O2CO3; CQDs/Bi2O2CO3 possess an efficient photocatalytic performance, and the organic matter removal rate of methylene blue and phenol can reach up to 94.45% and 61.46% respectively, within 2 h. In addition, the degradation analysis of phenol by high performance liquid chromatography (HPLC) proved that there are no other impurities in the degradation process. Photoelectrochemical testing proved that the introduction of CQDs (electron acceptor) effectively suppresses the recombination of e−-h+, and promotes charge transfer. Quenching experiments and electron spin resonance (ESR) suggested that ·OH, h+, and ·O2− were involved in the photocatalytic degradation process. These results suggested that the up-conversion function of CQDs could improve the electron transfer and light absorption ability of photocatalysts and ·O2− formation. Furthermore, the up-conversion function of CQDs would help maintain photocatalytic stability. Finally, the photocatalytic degradation mechanism was proposed according to the above experimental result. Full article
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<p>XRD patterns of the synthesized photocatalysts.</p> Full article ">Figure 2
<p>TEM images of as-prepared samples: (<b>a</b>) Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub>; (<b>b</b>,<b>c</b>) CQDs/Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub>; (<b>d</b>–<b>f</b>) HRTEM, SAED, EDX images of CQDs/Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub>.</p> Full article ">Figure 3
<p>(<b>a</b>) Photoluminescence (PL) spectra of Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub> and CQDs/Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub>; (<b>b</b>) PL curve of CQDs excited by different wavelengths of light.</p> Full article ">Figure 4
<p>XPS characteristic peak of the CQDs/Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub> sample. (<b>a</b>) Survey of the sample; (<b>b</b>) Bi 4f; (<b>c</b>) C 1s; (<b>d</b>) O 1s.</p> Full article ">Figure 5
<p>(<b>a</b>) Comparison of the photocatalytic degradation efficiency of MB by different photocatalysts (<b>b</b>) UV-vis spectral absorption changes of MB solution degraded by the 50-CQDs/Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub> composite; (<b>c</b>) TOC removal of MB.</p> Full article ">Figure 5 Cont.
<p>(<b>a</b>) Comparison of the photocatalytic degradation efficiency of MB by different photocatalysts (<b>b</b>) UV-vis spectral absorption changes of MB solution degraded by the 50-CQDs/Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub> composite; (<b>c</b>) TOC removal of MB.</p> Full article ">Figure 6
<p>Different photocatalytic degradation performances after adding different quenching agents ((<b>a</b>) IPA, (<b>b</b>)EDTA-2Na, (<b>c</b>) N<sub>2</sub>); (<b>d</b>) The corresponding degradation kinetic constant.</p> Full article ">Figure 7
<p>ESR spectra of radical adducts trapped by DMPO: (<b>a</b>) superoxide radical (·O<sub>2</sub><sup>−</sup>); (<b>b</b>) hydroxyl radical (·OH).</p> Full article ">Figure 8
<p>Cycling runs for the photocatalytic degradation of MB by CQDs/Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub> hybrid materials under visible light irradiation. (MB: 50 mL, 10 mg/L; CQDs/Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub>: 1 g/L).</p> Full article ">Figure 9
<p>the photocurrent of Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub> and CQDs/Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub> under visible light.</p> Full article ">Figure 10
<p>(<b>a</b>) Electrochemical impedance spectra (EIS) of Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub> and CQDs/Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub> under visible light; (<b>b</b>) The local amplification of (<b>a</b>).</p> Full article ">Figure 11
<p>(<b>a</b>) The photocatalytic activity comparison of phenol degradation; (<b>b</b>) HPLC chromatograms of phenol solutions with CQDs/Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub> photocatalyst; (<b>c</b>,<b>d</b>) 3D HPLC spectra of phenol degradation at 0 min and at 120 min.</p> Full article ">Figure 12
<p>Schematic of the possible reaction mechanism for organic pollutants degradation by CQDs/Bi<sub>2</sub>O<sub>2</sub>CO<sub>3</sub> under the simulated sunlight irradiation.</p> Full article ">
16 pages, 23419 KiB  
Article
Highly Efficient, Low-Cost, and Magnetically Recoverable FePt–Ag Nanocatalysts: Towards Green Reduction of Organic Dyes
by Yang Liu, Yuanyuan Zhang, Qiangwei Kou, Yue Chen, Yantao Sun, Donglai Han, Dandan Wang, Ziyang Lu, Lei Chen, Jinghai Yang and Scott Guozhong Xing
Nanomaterials 2018, 8(5), 329; https://doi.org/10.3390/nano8050329 - 14 May 2018
Cited by 26 | Viewed by 4183
Abstract
Nowadays, synthetic organic dyes and pigments discharged from numerous industries are causing unprecedentedly severe water environmental pollution, and conventional water treatment processes are hindered due to the corresponding sophisticated aromatic structures, hydrophilic nature, and high stability against light, temperature, etc. Herein, we report [...] Read more.
Nowadays, synthetic organic dyes and pigments discharged from numerous industries are causing unprecedentedly severe water environmental pollution, and conventional water treatment processes are hindered due to the corresponding sophisticated aromatic structures, hydrophilic nature, and high stability against light, temperature, etc. Herein, we report an efficient fabrication strategy to develop a new type of highly efficient, low-cost, and magnetically recoverable nanocatalyst, i.e., FePt–Ag nanocomposites, for the reduction of methyl orange (MO) and rhodamine B (RhB), by a facile seed deposition process. X-ray diffraction results elaborate that the as-synthesized FePt–Ag nanocomposites are pure disordered face-centered cubic phase. Transmission electron microscopy studies demonstrate that the amount of Ag seeds deposited onto the surfaces of FePt nanocrystals increases when increasing the additive amount of silver colloids. The linear correlation of the MO and RhB concentration versus reaction time catalyzed by FePt–Ag nanocatalysts is in line with pseudo-first-order kinetics. The reduction rate constants of MO and RhB increase with the increase of the amount of Ag seeds. FePt–Ag nanocomposites show good separation ability and reusability, and could be repeatedly applied for nearly complete reduction of MO and RhB for at least six successive cycles. Such cost-effective and recyclable nanocatalysts provide a new material family for use in environmental protection applications. Full article
(This article belongs to the Special Issue Alleviating Climate Change and Pollution with Nanomaterials)
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<p>Schematic illustration of the synthesis and application of FePt–Ag nanocomposites.</p> Full article ">Figure 2
<p>XRD patterns of the pure FePt nanocrystals and the FePt–Ag nanocomposites with different additive quantities of FePt nanocrystals (FePt–Ag 5 mg–60 mL and FePt–Ag 10 mg–60 mL) (<b>a</b>), and of the FePt–Ag nanocomposites with different additive amounts of silver colloids (FePt–Ag 10 mg–60 mL, FePt–Ag 10 mg–90 mL, and FePt–Ag 10 mg–120 mL) (<b>b</b>).</p> Full article ">Figure 3
<p>UV–vis absorbance spectra of silver colloids (black curve line), pure FePt nanocrystals (red dotted line), and FePt–Ag 10 mg–120 mL nanocomposites (blue dotted line).</p> Full article ">Figure 4
<p>TEM images of the pure FePt nanocrystals with high-resolution TEM (HRTEM) image (inset) (<b>a</b>), pure silver colloids (<b>b</b>), and FePt–Ag 5 mg–60 mL (<b>c</b>) and FePt–Ag 10 mg–60 mL nanocomposites (<b>d</b>).</p> Full article ">Figure 5
<p>TEM images of FePt–Ag 10 mg–60 mL (<b>a</b>), FePt–Ag 10 mg–90 mL (<b>b</b>), and FePt–Ag 10 mg–120 mL (<b>c</b>); (<b>d</b>) shows the corresponding selected area electron diffraction (SAED) pattern (inset) and HRTEM image of (<b>c</b>).</p> Full article ">Figure 6
<p>High-resolution XPS scans of Fe <span class="html-italic">2p</span> (<b>a</b>), Pt <span class="html-italic">4f</span> (<b>b</b>). and Ag <span class="html-italic">3d</span> (<b>c</b>) for pure FePt nanocrystals and for FePt–Ag 10 mg–60 mL, FePt–Ag 10 mg–90 mL, and FePt–Ag 10 mg–120 mL nanocomposites.</p> Full article ">Figure 7
<p>Magnetic hysteresis (<span class="html-italic">M-H</span>) loops of the pure FePt nanocrystals and the FePt–Ag nanocomposites with different additive quantities of FePt nanocrystals (FePt–Ag 5 mg–60 mL and FePt–Ag 10 mg–60 mL) (<b>a</b>), and the FePt–Ag nanocomposites with different additive amounts of silver colloids (FePt–Ag 10 mg–60 mL, FePt–Ag 10 mg–90 mL, and FePt–Ag 10 mg–120 mL) (<b>b</b>).</p> Full article ">Figure 8
<p>UV–vis absorption spectra of MO aqueous solution after reduction catalyzed by FePt–Ag 10 mg–60 mL (<b>a</b>), FePt–Ag 10 mg–90 mL (<b>c</b>), and FePt–Ag 10 mg–120 mL (<b>e</b>). (<b>b</b>,<b>d</b>,<b>f</b>) show the corresponding ln(<span class="html-italic">C</span>/<span class="html-italic">C</span><sub>0</sub>) versus reaction time plots.</p> Full article ">Figure 9
<p>UV–vis absorption spectra of RhB aqueous solution after reduction catalyzed by FePt–Ag 10 mg–60 mL (<b>a</b>), FePt–Ag 10 mg–90 mL (<b>c</b>), and FePt–Ag 10 mg–120 mL (<b>e</b>). (<b>b</b>,<b>d</b>,<b>f</b>) show the corresponding ln(<span class="html-italic">C</span>/<span class="html-italic">C</span><sub>0</sub>) versus reaction time plots.</p> Full article ">Figure 10
<p>Six cycles of the removal of MO (<b>a</b>) and RhB (<b>b</b>) with FePt–Ag 10 mg–120 mL.</p> Full article ">
23 pages, 6395 KiB  
Review
Nanostructured Graphene: An Active Component in Optoelectronic Devices
by Chang-Hyun Kim
Nanomaterials 2018, 8(5), 328; https://doi.org/10.3390/nano8050328 - 14 May 2018
Cited by 9 | Viewed by 6230
Abstract
Nanostructured and chemically modified graphene-based nanomaterials possess intriguing properties for their incorporation as an active component in a wide spectrum of optoelectronic architectures. From a technological point of view, this aspect brings many new opportunities to the now well-known atomically thin carbon sheet, [...] Read more.
Nanostructured and chemically modified graphene-based nanomaterials possess intriguing properties for their incorporation as an active component in a wide spectrum of optoelectronic architectures. From a technological point of view, this aspect brings many new opportunities to the now well-known atomically thin carbon sheet, multiplying its application areas beyond transparent electrodes. This article gives an overview of fundamental concepts, theoretical backgrounds, design principles, technological implications, and recent advances in semiconductor devices that integrate nanostructured graphene materials into their active region. Starting from the unique electronic nature of graphene, a physical understanding of finite-size effects, non-idealities, and functionalizing mechanisms is established. This is followed by the conceptualization of hybridized films, addressing how the insertion of graphene can modulate or improve material properties. Importantly, it provides general guidelines for designing new materials and devices with specific characteristics. Next, a number of notable devices found in the literature are highlighted. It provides practical information on material preparation, device fabrication, and optimization for high-performance optoelectronics with a graphene hybrid channel. Finally, concluding remarks are made with the summary of the current status, scientific issues, and meaningful approaches to realizing next-generation technologies. Full article
(This article belongs to the Special Issue Synthesis, Structure and Applications of 2D Nanomaterials)
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<p>(<b>a</b>) Shape of a monolayer graphene sheet; (<b>b</b>) electronic band structure of pristine graphene.</p> Full article ">Figure 2
<p>Characteristic field-effect behavior in single-layer graphene with its resistivity <span class="html-italic">ρ</span> decreasing by adding either holes (at negative <span class="html-italic">V<sub>G</sub></span>) or electrons (at positive <span class="html-italic">V<sub>G</sub></span>). <span class="html-italic">E<sub>F</sub></span> is the Fermi level. Reproduced with permission from [<a href="#B17-nanomaterials-08-00328" class="html-bibr">17</a>]. Nature Publishing Group, 2007.</p> Full article ">Figure 3
<p>(<b>a</b>) Illustration of the two characteristic graphene nanoribbon (GNR) motifs, namely zigzag and armchair, as determined by the repeating edge pattern; (<b>b</b>) Experimentally measured energy gap as a function of GNR width. These data were extracted from several devices with different sizes and orientations. Reproduced with permission from [<a href="#B23-nanomaterials-08-00328" class="html-bibr">23</a>]. Wiley-VCH, 2007.</p> Full article ">Figure 4
<p>(<b>a</b>) Chemical structure of tetrafluoro-tetracyanoquinodimethane (F4-TCNQ) used as an electron acceptor for graphene; (<b>b</b>) Concept of charge transfer between graphene and the contacting F4-TCNQ layer; (<b>c</b>) Photoemission spectra recorded during the deposition of F4-TCNQ (low kinetic energy part). Reproduced with permission from [<a href="#B34-nanomaterials-08-00328" class="html-bibr">34</a>]. American Chemical Society, 2007.</p> Full article ">Figure 5
<p>(<b>a</b>) Schematic illustration of MoO<sub>3</sub> deposited on graphene surface; (<b>b</b>) Energy level alignment at graphene/MoO<sub>3</sub> interface; (<b>c</b>) The evolution of sheet resistance in monolayer graphene. The overlapped final data points mean that the doped graphene is thermally stable (annealed at 140 °C). Reproduced with permission from [<a href="#B35-nanomaterials-08-00328" class="html-bibr">35</a>]. Nature Publishing Group, 2014.</p> Full article ">Figure 6
<p>Three representative hybrid film structures that can be employed for a graphene-based active layer in optoelectronic devices. (<b>a</b>) Chemically decorated graphene; (<b>b</b>) graphene/nanostructure hybrid; (<b>c</b>) multicomponent blend.</p> Full article ">Figure 7
<p>(<b>a</b>) Illustration for the preferred electronic transport pathways formed by inter-domain graphene bridges; (<b>b</b>) Energy diagram showing the trapping and detrapping of electrons that can be utilized for charge memory devices (CB: conduction band, VB: valence band).</p> Full article ">Figure 8
<p>(<b>a</b>) Energy diagram showing the separation of photogenerated carriers aided by graphene (CB: conduction band, VB: valence band); (<b>b</b>) Illustration for the light scattering effect in a semiconductor-graphene hybrid film.</p> Full article ">Figure 9
<p>(<b>a</b>) AFM images of pristine, aluminum (III) tetraphenyl-porphyrin (Al(III)TPP), and zinc tetraphenyl-porphyrin (ZnTPP) functionalized graphene; (<b>b</b>) Optical image of a ZnTPP-graphene photodetector (S: source, D: drain); (<b>c</b>) Energy diagram for the device operation; (<b>d</b>) Change of relative photoconductivity upon exposure to light with different wavelengths at a <span class="html-italic">V<sub>DS</sub></span> of 50 mV; (<b>e</b>) Responsivity as a function of light power density. Reproduced with permission from [<a href="#B62-nanomaterials-08-00328" class="html-bibr">62</a>]. Institute of Physics, 2016.</p> Full article ">Figure 10
<p>(<b>a</b>) Synthesis of 3,5-dinitrobenzoyl (EDNB)-functionalized graphene nanoflakes (GNF); (<b>b</b>) Energy diagram of a ternary PV illustrating the cascade effect; (<b>c</b>) Current density-voltage curves measured from devices with different GNF-EDNB concentrations under AM 1.5 condition. Reproduced with permission from [<a href="#B65-nanomaterials-08-00328" class="html-bibr">65</a>]. Wiley-VCH, 2015.</p> Full article ">Figure 11
<p>(<b>a</b>) Chemical structure of poly(3,3-didodecylquaterthiophene) (PQT-12) and the device structure of a hybrid FET; (<b>b</b>) Output characteristics of an optimized PQT-12/graphene transistor; (<b>c</b>) Mobility and on-off ratio for the samples with different fabrication conditions. Reproduced with permission from [<a href="#B66-nanomaterials-08-00328" class="html-bibr">66</a>]. Elsevier, 2011.</p> Full article ">Figure 12
<p>(<b>a</b>) Chemical structure of semiconducting polymers; (<b>b</b>) FET structure; (<b>c</b>) Charge-carrier mobility as a function of volume of the graphene solution and corresponding surface coverage; (<b>d</b>) Transfer curves for a P(NDI2OD-T2) device measured before and after a programming/erasing cycle (<span class="html-italic">V<sub>D</sub></span> = 40 V); (<b>e</b>) Durable memory operation of a P(NDI2OD-T2) device shown as reproducible <span class="html-italic">V</span><sub>th</sub> shifts. Reproduced with permission from [<a href="#B67-nanomaterials-08-00328" class="html-bibr">67</a>]. American Chemical Society, 2015.</p> Full article ">Figure 13
<p>(<b>a</b>) Transmission-electron microscope (TEM) image of hybrid graphene-ZnO NPs; (<b>b</b>) Structure of a lateral diode photodetector and the set up for spatially resolved excitation and electrical measurement; (<b>c</b>) Current-voltage characteristics measured in the dark and under illumination; (<b>d</b>) Photocurrent responses measured at different wavelengths. Reproduced with permission from [<a href="#B71-nanomaterials-08-00328" class="html-bibr">71</a>]. Royal Society of Chemistry, 2012.</p> Full article ">Figure 14
<p>(<b>a</b>) Illustration of the working mechanism of a PbSe-TiO<sub>2</sub>-graphene photodetector; (<b>b</b>) TEM image showing the inorganic crystals on graphene; (<b>c</b>) Large-area printed photodetector arrays on plastic; (<b>d</b>) Photoconductive gain as a function of excitation wavelength in different compositions. Reproduced with permission from [<a href="#B72-nanomaterials-08-00328" class="html-bibr">72</a>]. Wiley-VCH, 2012.</p> Full article ">Figure 15
<p>(<b>a</b>) Fabrication process for the FETs with a soluble graphene–In-Ga-Zn-O (IGZO) hybrid; (<b>b</b>) Electrical conductivity of the blend film as a function of volume percentage of graphene content. Symbols are experimental data and the solid line is a fit to the percolation theory; (<b>c</b>) Mechanical stability against bending for the pristine IGZO and graphene-hybridized FETs. Reproduced with permission from [<a href="#B76-nanomaterials-08-00328" class="html-bibr">76</a>]. Royal Society of Chemistry, 2013.</p> Full article ">Figure 16
<p>(<b>a</b>) Structure of a graphene-ZnO nanorod (NR) hybrid FET; (<b>b</b>) Transfer curves of a graphene-ZnO NR device under different UV irradiation powers (<span class="html-italic">V<sub>D</sub></span> = 1 V); (<b>c</b>) Energy diagram illustrating the sensing mechanism; (<b>d</b>) Response of graphene (Gr), ZnO NPs/Gr, and ZnO NRs/Gr FETs at the UV intensity of 2 mW/cm<sup>2</sup>; (<b>e</b>) Wavelength-dependent response of a ZnO NRs/Gr device. <span class="html-italic">V<sub>G</sub></span> = 0 V and <span class="html-italic">V<sub>D</sub></span> = 1 V for (<b>d</b>,<b>e</b>). Reproduced with permission from [<a href="#B77-nanomaterials-08-00328" class="html-bibr">77</a>]. Wiley-VCH, 2015.</p> Full article ">
13 pages, 2490 KiB  
Article
An Antimicrobial Peptide-Loaded Gelatin/Chitosan Nanofibrous Membrane Fabricated by Sequential Layer-by-Layer Electrospinning and Electrospraying Techniques
by Yuzhu He, Yahui Jin, Xiumei Wang, Shenglian Yao, Yuanyuan Li, Qiong Wu, Guowu Ma, Fuzhai Cui and Huiying Liu
Nanomaterials 2018, 8(5), 327; https://doi.org/10.3390/nano8050327 - 14 May 2018
Cited by 80 | Viewed by 7261
Abstract
Guided bone regeneration (GBR) technique is widely used in the treatment of bone defects caused by peri-implantitis, periodontal disease, etc. However, the GBR membranes commonly used in clinical treatments currently have no antibacterial activity. Therefore, in this study, sequential layer-by-layer electrospinning and electrospraying [...] Read more.
Guided bone regeneration (GBR) technique is widely used in the treatment of bone defects caused by peri-implantitis, periodontal disease, etc. However, the GBR membranes commonly used in clinical treatments currently have no antibacterial activity. Therefore, in this study, sequential layer-by-layer electrospinning and electrospraying techniques were utilized to prepare a gelatin (Gln) and chitosan (CS) composite GBR membrane containing hydroxyapatite nanoparticles (nHAp) and antimicrobial peptide (Pac-525)-loaded PLGA microspheres (AMP@PLGA-MS), which was supposed to have osteogenic and antibacterial activities. The scanning electron microscope (SEM) observation showed that the morphology of the nanofibers and microspheres could be successfully produced. The diameters of the electrospun fibers with and without nHAp were 359 ± 174 nm and 409 ± 197 nm, respectively, and the mechanical properties of the membrane were measured according to the tensile stress-strain curve. Both the involvement of nHAp and the chemical crosslinking were able to enhance their tensile strength. In vitro cell culture of rat bone marrow mesenchymal stem cells (rBMSCs) indicated that the Gln/CS composite membrane had an ideal biocompatibility with good cell adhesion, spreading, and proliferation. In addition, the Gln/CS membrane containing nHAp could promote osteogenic differentiation of rBMSCs. Furthermore, according to the in vitro drug release assay and antibacterial experiments, the composite GBR membrane containing AMP@PLGA-MS exhibited a long-term sustained release of Pac-525, which had bactericidal activity within one week and antibacterial activity for up to one month against two kinds of bacteria, S. aureus and E. coli. Our results suggest that the antimicrobial peptide-loaded Gln/CS composite membrane (AMP@PLGA-MS@Gln/CS/nHAp) has a great promise in bone generation-related applications for the unique functions of guiding bone regeneration and inhibiting bacterial infection as well. Full article
(This article belongs to the Special Issue The Fabrication and Application of Nanofibers)
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<p>Schematic diagram of the fabrication process and structure of the AMP@PLGA-MS@Gln/CS/nHAp composite membrane by sequential layer-by-layer electrospinning and electrospraying. This biodegradable membrane consists of two layers: the barrier layer (Gln/CS nanofibers) and osteogenic layer (Gln/CS/nHAp nanofibers). The AMP-loaded PLGA microspheres were electrosprayed alternately during the electrospinning, and were therefore embedded within the membrane.</p> Full article ">Figure 2
<p>The gross and SEM morphologies of the Gln/CS composite membrane. (<b>A</b>) The barrier layer of Gln/CS nanofibers before crosslinking; (<b>B</b>) The barrier layer of Gln/CS nanofibers after crosslinking; (<b>C</b>) Electrosprayed AMP@PLGA microspheres; (<b>D</b>,<b>E</b>) The osteogenic layer of Gln/CS/nHAp by magnetic stirring (<b>D</b>) and ultrasonic dispersion (<b>E</b>); (<b>F</b>) The typical cross-sectional morphology of the membrane; (<b>G</b>,<b>H</b>) The typical morphologies of the AMP@PLGA MSs embedded within the membrane; (<b>I</b>) Gross image of the Gln/CS composite membrane.</p> Full article ">Figure 3
<p>SEM micrographs of rBMSCs seeded on the barrier layer (<b>A</b>–<b>C</b>) and osteogenic layer (<b>D</b>–<b>F</b>) of the Gln/CS composite membrane after 1 d, 4 d, and 7 d of cell culture.</p> Full article ">Figure 4
<p>CLSM micrographs of rBMSCs seeded on the barrier layer (<b>A</b>–<b>C</b>) and osteogenic layer (<b>D</b>–<b>F</b>) of the Gln/CS composite membrane after 1 d, 4 d, and 7 d of cell culture.</p> Full article ">Figure 5
<p>Cell behaviors of rBMSCs cultured on the Gln/CS composite membrane. (<b>A</b>) Cell proliferation on the barrier layer, osteogenic layer and coverslip control by CCK-8 assay; (<b>B</b>) Osteogenic differentiation of rBMSCs on the barrier layer, osteogenic layer and coverslip control by ALPase activity assay. * <span class="html-italic">p</span> &lt; 0.05.</p> Full article ">Figure 6
<p>In vitro release profile of Pac-525 from the Gln/CS composite membrane. (<b>A</b>) The concentration of released Pac-525; (<b>B</b>) Cumulative release percentage of Pac-525.</p> Full article ">Figure 7
<p>The typical morphologies of the inhibition zone induced by the elution solutions of AMP@PLGA-MS@Gln/CS/nHAp composite membrane at the first week (<b>A</b>,<b>B</b>) and the fourth week (<b>C</b>,<b>D</b>) against <span class="html-italic">E. coli</span> (<b>A</b>,<b>C</b>) and <span class="html-italic">S. aureus</span> (<b>C</b>,<b>D</b>) after 3 days of incubation on agar plate.</p> Full article ">
10 pages, 1319 KiB  
Article
Borylation of α,β-Unsaturated Acceptors by Chitosan Composite Film Supported Copper Nanoparticles
by Wu Wen, Biao Han, Feng Yan, Liang Ding, Bojie Li, Liansheng Wang and Lei Zhu
Nanomaterials 2018, 8(5), 326; https://doi.org/10.3390/nano8050326 - 14 May 2018
Cited by 11 | Viewed by 4370
Abstract
We describe here the preparation of copper nanoparticles stabilized on a chitosan/poly (vinyl alcohol) composite film. This material could catalyze the borylation of α,β-unsaturated acceptors in aqueous media under mild conditions. The corresponding organoboron compounds as well as their converted β-hydroxyl products were [...] Read more.
We describe here the preparation of copper nanoparticles stabilized on a chitosan/poly (vinyl alcohol) composite film. This material could catalyze the borylation of α,β-unsaturated acceptors in aqueous media under mild conditions. The corresponding organoboron compounds as well as their converted β-hydroxyl products were all obtained in good to excellent yields. It is noteworthy that this catalyst of copper nanoparticles can be easily recycled eight times and remained catalytically reactive. This newly developed methodology provides an efficient and sustainable pathway for the synthesis of organoboron compounds and application of copper nanoparticles. Full article
(This article belongs to the Special Issue Sustainable Nanoparticles - Their Synthesis and Catalytic Applications)
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Full article ">Figure 1
<p>Organoboron compounds with biological activities.</p> Full article ">Figure 2
<p>Substrate scope of α,β-unsaturated acceptors <sup>a,b</sup>. <sup>a</sup> Reaction conditions: substrate <b>2</b> (0.2 mmol), B<sub>2</sub>(pin)<sub>2</sub> <b>1</b> (1.2 equiv.), CP@Cu NPs (1 mol % Cu loading), acetone (1.6 mL), H<sub>2</sub>O (0.4 mL), room temperature, air, 12 h; <sup>b</sup> Isolated yields were listed; <sup>c</sup> Gram scale synthesis.</p> Full article ">Figure 2 Cont.
<p>Substrate scope of α,β-unsaturated acceptors <sup>a,b</sup>. <sup>a</sup> Reaction conditions: substrate <b>2</b> (0.2 mmol), B<sub>2</sub>(pin)<sub>2</sub> <b>1</b> (1.2 equiv.), CP@Cu NPs (1 mol % Cu loading), acetone (1.6 mL), H<sub>2</sub>O (0.4 mL), room temperature, air, 12 h; <sup>b</sup> Isolated yields were listed; <sup>c</sup> Gram scale synthesis.</p> Full article ">Figure 3
<p>Recycling for the chitosan/poly (vinyl alcohol) composite film supported copper nanoparticles.</p> Full article ">
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