Nanomaterials

18 pages, 15617 KiB

Open AccessArticle

A Chromate-Free and Convenient Route to Fabricate Thin and Compact Conversion Coating for Corrosion Protection on LZ91 Magnesium Alloy

by Chun-Wei Chen, Salim Levent Aktug, Chin-Jou Chang, Yueh-Lien Lee, Ming-Der Ger and Shun-Yi Jian

Nanomaterials 2022, 12(9), 1614; https://doi.org/10.3390/nano12091614 - 9 May 2022

Cited by 5 | Viewed by 1803

Abstract

This study characterizes and determines the corrosion resistance of Mn-Ce conversion coated LZ91 magnesium alloy that undergoes pretreatments. It is challenging to process large and curved workpieces in the industry because the geometric shapes are complex if they are mechanically ground. This study [...] Read more.

This study characterizes and determines the corrosion resistance of Mn-Ce conversion coated LZ91 magnesium alloy that undergoes pretreatments. It is challenging to process large and curved workpieces in the industry because the geometric shapes are complex if they are mechanically ground. This study uses acid pickling instead of mechanical grinding, and a nitric acid solution is used for pickling. After pretreatments, the samples are immersed for 30 s in a conversion coating solution containing 0.1 M KMnO₄ and 0.025 M Ce(NO₃)₃ with a pH of 1.5, as demonstrated in previous studies by the authors. The microstructure of the coating layer and electrochemical behavior of conversion coated samples exposed to 3.5 wt.% NaCl solution are studied. The corrosion behavior of Mn-Ce conversion coating specimens is determined using a salt spray test (SST). Scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS) are used to analyze the interface between the coating layer and the underlying magnesium substrate and to investigate the microstructure of the specimens. The roughness of the coatings is measured using 3D white light interferometry. The results show that the deteriorated area ratio for conversion coated LZ91 decreases to less than 5% after 72 h of SST exposure, and the corrosion resistance is improved 2.25 times with the Mn-Ce conversion coating on LZ91 magnesium alloy. Full article

(This article belongs to the Section Synthesis, Interfaces and Nanostructures)

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13 pages, 578 KiB

Open AccessArticle

Cyanine-Doped Nanofiber Mats for Laser Tissue Bonding

by Fulvio Ratto, Giada Magni, Annalisa Aluigi, Marta Giannelli, Sonia Centi, Paolo Matteini, Werner Oberhauser, Roberto Pini and Francesca Rossi

Nanomaterials 2022, 12(9), 1613; https://doi.org/10.3390/nano12091613 - 9 May 2022

Cited by 1 | Viewed by 1847

Abstract

In spite of an extensive body of academic initiatives and innovative products, the toolkit of wound dressing has always revolved around a few common concepts such as adhesive patches and stitches and their variants. Our work aims at an alternative solution for an [...] Read more.

In spite of an extensive body of academic initiatives and innovative products, the toolkit of wound dressing has always revolved around a few common concepts such as adhesive patches and stitches and their variants. Our work aims at an alternative solution for an immediate restitutio ad integrum of the mechanical functionality in cutaneous repairs. We describe the fabrication and the application of electrospun mats of bioactive nanofibers all made of biocompatible components such as a natural polysaccharide and a cyanine dye for use as laser-activatable plasters, resembling the ultrastructure of human dermis. In particular, we investigate their morphological features and mechanical moduli under conditions of physiological relevance, and we test their use to bind a frequent benchmark of connective tissue as rabbit tendon and a significant case of clinical relevance as human dermis. Altogether, our results point to the feasibility of a new material for wound dressing combining translational potential, strength close to human dermis, extensibility exceeding 15% and state-of-art adhesive properties. Full article

(This article belongs to the Section Biology and Medicines)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
Visual appearance and ultrastructure of the films: Photographs of specimens of the films of a size around 1 cm<math display="inline"><semantics> <msup> <mrow/> <mn>2</mn> </msup> </semantics></math> (a) before (left) and after (right) hydration in a physiological buffer and (b) upon hydration before (left) and after (right) cross-linking. The green spots in the dry sample are usual defects originating from occasional instabilities and dripping in the process of electrospinning. Note that the sample before cross-linking undergoes partial dissolution upon soaking in physiological buffer for 30 min, and so it is only partially recovered after hydration. (c) Spectrum of optical extinction of a cross-linked sample after a slight hydration taken with a V-770 device from Jasco (Tokyo, Japan). The pink line represents the optical emission of the diode laser used for welding. (d) Representative SEM micrograph of a sample before hydration. The scale bar corresponds to 5 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m. Full article ">Figure 2
Tensile testing of the films and its microscopic interpretation: (a) representative stress–strain curves for the samples before (blue) and after (green) hydration in physiological buffer both before (dotted) and after (continuous) cross-linking. All curves were drawn from the nominal thickness of the films in air, i.e., 11 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m. The 10 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m × 6 <math display="inline"><semantics> <mi mathvariant="sans-serif">μ</mi> </semantics></math>m SEM micrographs of cross-linked (b,c) and as-spun (d,e) samples both before (b,d) and after (c,e) hydration. (f) Relevant distributions of fiber diameters computed both before (blue) and after (green) hydration, and before (light) and after (dark) cross-linking. Note that it was impossible to assess the fiber diameters in the case of the as-spun samples after hydration due to their largely compromised morphology. Full article ">Figure 3
Laser bonding to biological tissue and its mechanical strength: Photographs of films welded to a segment of rabbit tendon (a) and a simulated wound in human skin (b). The irradiated spots look clearer than their neighborhood probably due to the photobleaching of ICG and an ultrastructural modification of the mats. (c) Snapshots taken during a measuring run in the case of shear testing of the adhesion between a sample and a piece of rabbit tendon. (d) Relevant stress–strain curve calculated by normalizing by the total nominal surface area of the 20 spots. The arrows roughly correspond to the snapshots reported in panel (c) and illustrate that the breakdown of the seam occurs by the progressive failure of individual spots one by one or in small subgroups. Full article ">

15 pages, 2528 KiB

Open AccessEditor’s ChoiceArticle

Micro- and Nanofibrillated Cellulose from Annual Plant-Sourced Fibers: Comparison between Enzymatic Hydrolysis and Mechanical Refining

by Roberto Aguado, Quim Tarrés, Maria Àngels Pèlach, Pere Mutjé, Elena de la Fuente, José L. Sanchez-Salvador, Carlos Negro and Marc Delgado-Aguilar

Nanomaterials 2022, 12(9), 1612; https://doi.org/10.3390/nano12091612 - 9 May 2022

Cited by 12 | Viewed by 2233

Abstract

The current trends in micro-/nanofibers offer a new and unmissable chance for the recovery of cellulose from non-woody crops. This work assesses a technically feasible approach for the production of micro- and nanofibrillated cellulose (MNFC) from jute, sisal and hemp, involving refining and [...] Read more.

The current trends in micro-/nanofibers offer a new and unmissable chance for the recovery of cellulose from non-woody crops. This work assesses a technically feasible approach for the production of micro- and nanofibrillated cellulose (MNFC) from jute, sisal and hemp, involving refining and enzymatic hydrolysis as pretreatments. Regarding the latter, only slight enhancements of nanofibrillation, transparency and specific surface area were recorded when increasing the dose of endoglucanases from 80 to 240 mg/kg. This supports the idea that highly ordered cellulose structures near the fiber wall are resistant to hydrolysis and hinder the diffusion of glucanases. Mechanical MNFC displayed the highest aspect ratio, up to 228 for hemp. Increasing the number of homogenization cycles increased the apparent viscosity in most cases, up to 0.14 Pa·s at 100 s⁻¹ (1 wt.% consistency). A shear-thinning behavior, more marked for MNFC from jute and sisal, was evidenced in all cases. We conclude that, since both the raw material and the pretreatment play a major role, the unique characteristics of non-woody MNFC, either mechanical or enzymatically pretreated (low dose), make it worth considering for large-scale processes. Full article

(This article belongs to the Special Issue Preparation, Characterization and Industrial Application of Nanocellulose)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
General experimental layout. Full article ">Figure 2
Chemical composition of the pulps from jute (a), sisal (b), and hemp (c). Full article ">Figure 3
Effect of mechanical and enzymatic pretreatments on fiber length, expressed as the length-weighted mean. Full article ">Figure 4
Yield of nanofibrillation and transmittance at 600 nm for jute, sisal and hemp MNCF after extensive PFI refining and different numbers of HPH cycles. Full article ">Figure 5
Yield of nanofibrillation (a) and transmittance at 600 nm (b) for jute, sisal and hemp MNCF whose pretreatment consistent of an endoglucanase-mediated hydrolysis at different dosages. The horizontal axis indicates the HPH sequence: cycles at 300 bar, at 600 bar and at 900 bar. Full article ">Figure 6
Evolution of the apparent viscosity at 100 s−1 of suspensions of MNFC from jute (a), sisal (b) and hemp (c). Numbers in italics represent the slope of a trend line. Full article ">

12 pages, 4653 KiB

Open AccessArticle

High-Resolution Patterning of Organic Emitting-Layer by Using Inkjet Printing and Sublimation Transfer Process

by Jun Yeub Lee, Byeong-Kwon Ju and Kwan Hyun Cho

Nanomaterials 2022, 12(9), 1611; https://doi.org/10.3390/nano12091611 - 9 May 2022

Cited by 2 | Viewed by 2477

Abstract

We implemented ultra-high resolution patterns of 2822 pixels-per-inch (PPI) via an inkjet printing and vacuum drying process grafted onto a sublimation transfer process. Co-solvented ink with a 1:1 ratio of N,N-dimethylformamide (DMF) to ortho-dichlrorobenzene (oDCB) was used, and the inkjet driving waveform was [...] Read more.

We implemented ultra-high resolution patterns of 2822 pixels-per-inch (PPI) via an inkjet printing and vacuum drying process grafted onto a sublimation transfer process. Co-solvented ink with a 1:1 ratio of N,N-dimethylformamide (DMF) to ortho-dichlrorobenzene (oDCB) was used, and the inkjet driving waveform was optimized via analysis of Ohnesorge (Oh)—Reynolds (Re) numbers. Inkjet printing conditions on the donor substrate with 2822 PPI microchannels were investigated in detail according to the drop space and line space. Most sublimation transferred patterns have porous surfaces under drying conditions in an air atmosphere. Unlike the spin-coating process, the drying process of inkjet-printed films on the microchannel has a great effect on the sublimation of transferred thin film. Therefore, to control the morphology, we carefully investigated the drying process of the inkjet-printed inks in the microchannel. Using a vacuum drying process to control the morphology of inkjet-printed films, line patterns of 2822 PPI resolution having a root-mean-square (RMS) roughness of 1.331 nm without voids were successfully fabricated. Full article

(This article belongs to the Topic Optoelectronic Materials)

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(a) Sequential schematic diagram of the patterning process by using inkjet printing grafted onto the sublimation transfer process. (b) SEM images of the LTHC substrate’s top and side views and (c) a picture of the LTHC donor substrate. Full article ">Figure 2
(a) Ohnesorge map of the area of the printable fluid and dimensionless numbers of produced co-solvented inks (b) schematic diagram of inkjet-printed drop positions onto microchannel. Ink drop images with co-solvented (c) with DMF and oDCB ink, and (d) with CB and oDCB ink. Full article ">Figure 3
OM images of inkjet-printed onto the microchannel on the donor substrate with UV exposure according to the drop and line space. Inkjet-printed with (a–c) 9 μm, (d–f) 18 μm, and (g–i) 27 μm for line space, and (a,d,g) 20 μm, (b,e,h) 25 μm, (c,f,i) and 33 μm for drop space. Full article ">Figure 4
AFM images of sublimation transferred patterns according to the drop and line space. Inkjet-printed with (a–c) 9 μm, (d–f) 18 μm, and (g–i) 27 μm for line space, and (a,d,g) 20 μm, (b,e,h) 25 μm, (c,f,i) and 33 μm for drop space. Insets are cross-sectional data, respectively. Full article ">Figure 5
UV exposed OM images of inkjet-printed onto the microchannel of the donor substrate after drying (a) at room temperature, (b) 30 °C, (c) 50 °C, and (d) 80 °C in a vacuum chamber. Full article ">Figure 6
Schematic diagram of the residual solvent behavior and ink solidifying state (a) at room temperature and (b) at high temperature in the vacuum drying process. The AFM images of the solidified ink in the microchannel at (c) room temperature and (d) high temperature according to the vacuum drying process. Full article ">Figure 7
AFM images of sublimation transferred patterns after the drying process (a) at room temperature, (b) 30 °C, (c) 50 °C, and (d) 80 °C in a vacuum chamber. Insets are cross-sectional data, respectively. Full article ">Figure 8
(a) OM image with UV exposure of sublimation transferred pattern. (b) Normalized PL spectra at an excitation wavelength of 365 nm, according to the patterning methods; sublimation transfer, evaporation, and spin-coating. Insets are the chemical structure of the emitting materials; CBP and Ir(MDQ)2acac. Full article ">

13 pages, 3028 KiB

Open AccessArticle

Computational NEXAFS Characterization of Molecular Model Systems for 2D Boroxine Frameworks

by Daniele Toffoli, Elisa Bernes, Albano Cossaro, Gabriele Balducci, Mauro Stener, Silvia Mauri and Giovanna Fronzoni

Nanomaterials 2022, 12(9), 1610; https://doi.org/10.3390/nano12091610 - 9 May 2022

Cited by 1 | Viewed by 1547

Abstract

The electronic properties of 2D boroxine networks are computationally investigated by simulating the NEXAFS spectra of a series of molecular models, with or without morphologic defects, with respect to the ideal honeycomb structure. The models represent portions of an irregular 2D boroxine framework [...] Read more.

The electronic properties of 2D boroxine networks are computationally investigated by simulating the NEXAFS spectra of a series of molecular models, with or without morphologic defects, with respect to the ideal honeycomb structure. The models represent portions of an irregular 2D boroxine framework obtained experimentally, as supported by the Au(111) surface. The B K-edge NEXAFS spectra are calculated within the transition potential (TP) approximation (DFT-TP). The role of the Au(111) supporting surface on the spectral features has also been investigated by comparing the calculated spectra of a defect-rich model in its free-standing and supported form. The calculated NEXAFS spectra differ from the experimental ones, as the position of the main resonance does not match in the two cases. This finding could suggest the presence of a strong interaction of the 2D boroxine network with the Au substrate, which is not captured in the model calculations. However, good agreement between measured and calculated B K-edge NEXAFS spectra is obtained for a model system, namely, trihydroxy boroxine, in which the B atoms are less screened by the valence electrons compared to the B–B linked boroxine network models considered here. These results suggest catalytic activity in the gold substrate in promoting a weakening or even the breaking of the B–B bond, which is not revealed by calculations. Full article

(This article belongs to the Special Issue Density Functional Theory Simulations of Nanostructures)

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Ball-and-stick representation of the building blocks models of the THDB network: (A) model M1, portion of an ideal honeycomb boroxine network, (B) model M2, (C) model M3. B atoms in yellow, O atoms in red, H atoms in white. Full article ">Figure 2
Calculated B K-edge NEXAFS spectrum of THDB (reported on the right side). (Upper panel): DFT-TP results; (lower panel): ΔSCF results. The stick spectra are broadened by using a Gaussian line shape with FWHM = 0.5 eV. ΔSCF B1s IP (197.28 eV) is reported as a vertical dashed line. Full article ">Figure 3
Calculated B1s NEXAFS spectra of M1 (upper panel), M2 (middle panel) and M3 (lower panel) molecular models depicted on the right side. Labels denote the non-equivalent Bi sites (see text for explanation). Transitions from the non-equivalent Bi atoms are reported as vertical colored lines in the spectra. The ΔSCF B1s ionization energies are shown as vertical dashed lines (the IP values are reported in <a href="#app1-nanomaterials-12-01610" class="html-app">Supplementary Table S1</a>). The stick spectra are broadened by using a Gaussian line shape with FWHM = 0.3 eV. Full article ">Figure 4
Comparison between the calculated B1s NEXAFS spectra of free M3 (upper panel) and M3@Au(111) (lower panel). The contributions of the three groups of non-equivalent Bi sites are also shown (colored solid lines). The ΔSCF B1s ionization energies are shown as vertical dashed lines (the IP values are reported in <a href="#app1-nanomaterials-12-01610" class="html-app">Supplementary Table S1</a>). The stick spectra are broadened by using a Gaussian line shape with FWHM = 0.3 eV. The M3 and M3@Au(111) models employed are reported on the right side. Full article ">Figure 5
B1s NEXAFS spectra of boroxinated monolayer ((upper panel), experimental data with permission from ref. [<a href="#B7-nanomaterials-12-01610" class="html-bibr">7</a>]), M3@Au(111) (middle panel) and THBoroxine (lower panel) at the two different polarization angles. For the THBoroxine molecule (displayed along the corresponding spectrum), the B1s total spectrum is also reported. The ΔSCF B1s ionization energies are shown as vertical dashed lines (IP mean value for M3@Au, 198.92 eV for THBoroxine). The calculated stick spectra are broadened by using a Gaussian line shape with FWHM = 0.3 eV. Full article ">

21 pages, 3047 KiB

Open AccessReview

Overview of the Influence of Silver, Gold, and Titanium Nanoparticles on the Physical Properties of PEDOT:PSS-Coated Cotton Fabrics

by Fahad Alhashmi Alamer and Rawan F. Beyari

Nanomaterials 2022, 12(9), 1609; https://doi.org/10.3390/nano12091609 - 9 May 2022

Cited by 21 | Viewed by 3162

Abstract

Metallic nanoparticles have been of interest to scientists, and they are now widely used in biomedical and engineering applications. The importance, categorization, and characterization of silver nanoparticles, gold nanoparticles, and titanium nanoparticles have been discussed. Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) is the most practical and [...] Read more.

Metallic nanoparticles have been of interest to scientists, and they are now widely used in biomedical and engineering applications. The importance, categorization, and characterization of silver nanoparticles, gold nanoparticles, and titanium nanoparticles have been discussed. Poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) is the most practical and reliable conductive polymer used in the manufacturing of conductive textiles. The effects of metallic nanoparticles on the performance of PEDOT:PSS thin films are discussed. The results indicated that the properties of PEDOT:PSS significantly depended on the synthesis technique, doping, post-treatment, and composite material. Further, electronic textiles known as smart textiles have recently gained popularity, and they offer a wide range of applications. This review provides an overview of the effects of nanoparticles on the physical properties of PEDOT:PSS-coated cotton fabrics. Full article

(This article belongs to the Collection Metallic and Metal Oxide Nanohybrids and Their Applications)

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15 pages, 4447 KiB

Open AccessArticle

Plasmonic Ag Nanoparticle-Loaded n-p Bi₂O₂CO₃/α-Bi₂O₃ Heterojunction Microtubes with Enhanced Visible-Light-Driven Photocatalytic Activity

by Haibin Li, Xiang Luo, Ziwen Long, Guoyou Huang and Ligang Zhu

Nanomaterials 2022, 12(9), 1608; https://doi.org/10.3390/nano12091608 - 9 May 2022

Cited by 11 | Viewed by 2373

Abstract

In this study, n-p Bi₂O₂CO₃/α-Bi₂O₃ heterojunction microtubes were prepared via a one-step solvothermal route in an H₂O-ethylenediamine mixed solvent for the first time. Then, Ag nanoparticles were loaded onto the microtubes using [...] Read more.

In this study, n-p Bi₂O₂CO₃/α-Bi₂O₃ heterojunction microtubes were prepared via a one-step solvothermal route in an H₂O-ethylenediamine mixed solvent for the first time. Then, Ag nanoparticles were loaded onto the microtubes using a photo-deposition process. It was found that a Bi₂O₂CO₃/α-Bi₂O₃ heterostructure was formed as a result of the in situ carbonatization of α-Bi₂O₃microtubes on the surface. The photocatalytic activities of α-Bi₂O₃ microtubes, Bi₂O₂CO₃/α-Bi₂O₃ microtubes, and Ag nanoparticle-loaded Bi₂O₂CO₃/α-Bi₂O₃ microtubes were evaluated based on their degradation of methyl orange under visible-light irradiation (λ > 420 nm). The results indicated that Bi₂O₂CO₃/α-Bi₂O₃ with a Bi₂O₂CO₃ mass fraction of 6.1% exhibited higher photocatalytic activity than α-Bi₂O₃. Loading the microtubes with Ag nanoparticles significantly improved the photocatalytic activity of Bi₂O₂CO₃/α-Bi₂O₃. This should be ascribed to the internal static electric field built at the heterojunction interface of Bi₂O₂CO₃ and α-Bi₂O₃ resulting in superior electron conductivity due to the Ag nanoparticles; additionally, the heterojunction at the interfaces between two semiconductors and Ag nanoparticles and the local electromagnetic field induced by the surface plasmon resonance effect of Ag nanoparticles effectively facilitate the photoinduced charge carrier transfer and separation of α-Bi₂O₃. Furthermore, loading of Ag nanoparticles leads to the formation of new reactive sites, and a new reactive species ·O²⁻ for photocatalysis, compared with Bi₂O₂CO₃/α-Bi₂O₃. Full article

(This article belongs to the Special Issue Luminescence Nanomaterials and Applications)

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11 pages, 3641 KiB

Open AccessEditor’s ChoiceArticle

Unexpected Phonon Behaviour in BiFe_xCr_1−xO₃, a Material System Different from Its BiFeO₃ and BiCrO₃ Parents

by Cameliu Himcinschi, Felix Drechsler, David Sebastian Walch, Akash Bhatnagar, Alexei A. Belik and Jens Kortus

Nanomaterials 2022, 12(9), 1607; https://doi.org/10.3390/nano12091607 - 9 May 2022

Cited by 3 | Viewed by 2088

Abstract

The dielectric function and the bandgap of BiFe_0.5Cr_0.5O₃ thin films were determined from spectroscopic ellipsometry and compared with that of the parent compounds BiFeO₃ and BiCrO₃. The bandgap value of BiFe_0.5Cr_0.5O [...] Read more.

The dielectric function and the bandgap of BiFe_0.5Cr_0.5O₃ thin films were determined from spectroscopic ellipsometry and compared with that of the parent compounds BiFeO₃ and BiCrO₃. The bandgap value of BiFe_0.5Cr_0.5O₃ is lower than that of BiFeO₃ and BiCrO₃, due to an optical transition at ~2.27 eV attributed to a charge transfer excitation between the Cr and Fe ions. This optical transition enables new phonon modes which have been investigated using Raman spectroscopy by employing multi-wavelengths excitation. The appearance of a new Raman mode at ~670 cm⁻¹ with a strong intensity dependence on the excitation line and its higher order scattering activation was found for both BiFe_0.5Cr_0.5O₃ thin films and BiFe_xCr_1−xO₃ polycrystalline bulk samples. Furthermore, Raman spectroscopy was also used to investigate temperature induced structural phase transitions in BiFe_0.3Cr_0.7O₃. Full article

(This article belongs to the Special Issue New Achievements in Nanostructured and Low Dimensional Materials and Systems)

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Real (ε1) and imaginary (ε2) part of BiFe0.5Cr0.5O3 dielectric function. The dotted vertical lines indicate the energy position of the laser lines used for Raman spectroscopy, while the vertical grey arrows show the energy position of the absorption peaks. The inset show the linear extrapolation of (αE)2 to zero absorption which give the value of the optical band gap. Full article ">Figure 2
Absorption coefficient of BiFe0.5Cr0.5O3 in comparison with the absorption coefficients of BiFeO3 and BiCrO3. The inset show a zoom of the absorption onset region with the vertical arrow indicating the first absorption peak at ~2.27 eV. Full article ">Figure 3
Raman spectra of a 200 nm BiFe0.5Cr0.5O3 thin film on SrTiO3 substrate and of the substrate normalised at the same intensity in the 200–400 cm−1 region, measured with an excitation of 633 nm. The corresponding film signal was calculated as a difference spectrum of the two (upper panel). The difference spectra of the thin film obtained with different excitations lines (633 nm, 532 nm, and 442 nm) and the as measured spectrum with the 325 nm excitation (lower panel). Full article ">Figure 4
The difference spectrum of the BiFe0.5Cr0.5O3 thin film compared to the spectra of bulk BiFexCr1−xO3, and of the parent compounds BiCrO3 and BiFeO3 measured with 633 nm excitation. Note the strong peak at 660–670 cm−1 which is detected only for the samples with a Fe/Cr mixture. Full article ">Figure 5
Comparison of the Raman spectra of bulk BiFe0.3Cr0.7O3 recorded with different excitation lines in the range of the first, second, and third order of the mode at ~667 cm−1. Full article ">Figure 6
Temperature dependence (90–700 K) of the Raman spectra for bulk BiFe0.3Cr0.7O3 showing a reversible phase transition above 475 K. Full article ">

14 pages, 6535 KiB

Open AccessArticle

Microorganism-Templated Nanoarchitectonics of Hollow TiO₂-SiO₂ Microspheres with Enhanced Photocatalytic Activity for Degradation of Methyl Orange

by Shenglan Liao, Liqin Lin, Jiale Huang, Xiaolian Jing, Shiping Chen and Qingbiao Li

Nanomaterials 2022, 12(9), 1606; https://doi.org/10.3390/nano12091606 - 9 May 2022

Cited by 5 | Viewed by 2154

Abstract

In this study, hollow SiO₂ microspheres were synthesized by the hydrolysis of tetraethyl orthosilicate (TEOS) according to the Stober process, in which Pichia pastoris GS 115 cells were served as biological templates. The influence of the preprocessing method, the TEOS concentration, the [...] Read more.

In this study, hollow SiO₂ microspheres were synthesized by the hydrolysis of tetraethyl orthosilicate (TEOS) according to the Stober process, in which Pichia pastoris GS 115 cells were served as biological templates. The influence of the preprocessing method, the TEOS concentration, the ratio of water to ethanol, and the aging time on the morphology of microspheres was investigated and the optimal conditions were identified. Based on this, TiO₂-SiO₂ microspheres were prepared by the hydrothermal process. The structures and physicochemical properties of TiO₂-SiO₂ photocatalysts were systematically characterized and discussed. The photocatalytic activity for the degradation of methyl orange (MO) at room temperature under Xe arc lamp acting as simulated sunlight was explored. The result showed that the as-prepared TiO₂-SiO₂ microspheres exhibited a good photocatalytic performance. Full article

(This article belongs to the Topic Nanoarchitectonics with Molecular and Materials Science: Functional Materials for Energy, Environment, Bio and Others)

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20 pages, 11292 KiB

Open AccessArticle

Discharge Enhancement in a Triple-Pipe Heat Exchanger Filled with Phase Change Material

by Yongfeng Ju, Roohollah Babaei-Mahani, Raed Khalid Ibrahem, Shoira Khakberdieva, Yasir Salam Karim, Ahmed N. Abdalla, Abdullah Mohamed, Mustafa Z. Mahmoud and Hafiz Muhammad Ali

Nanomaterials 2022, 12(9), 1605; https://doi.org/10.3390/nano12091605 - 9 May 2022

Cited by 8 | Viewed by 2510

Abstract

This study aims to study the discharging process to verify the influence of geometry modifications and heat transfer flow (HTF) patterns on the performance of a vertical triplex-tube latent heat container. The phase change material (PCM) is included in the middle tube, where [...] Read more.

This study aims to study the discharging process to verify the influence of geometry modifications and heat transfer flow (HTF) patterns on the performance of a vertical triplex-tube latent heat container. The phase change material (PCM) is included in the middle tube, where the geometry is modified using single or multi-internal frustum tubes instead of straight tubes to enhance the discharging rate. The effects of the HTF flow direction, which is considered by the gravity and opposite-gravity directions, are also examined in four different cases. For the optimal geometry, three scenarios are proposed, i.e., employing a frustum tube for the middle tube, for the inner tube, and at last for both the inner and middle tubes. The effects of various gap widths in the modified geometries are investigated. The results show the advantages of using frustum tubes in increasing the discharging rate and reducing the solidification time compared with that of the straight tube unit due to the higher natural convection effect by proper utilization of frustum tubes. The study of the HTF pattern shows that where the HTF direction in both the inner and outer tubes are in the gravity direction, the maximum discharging rate can be achieved. For the best configuration, the discharge time is reduced negligibly compared with that for the system with straight tubes which depends on the dimensions of the PCM domain. Full article

(This article belongs to the Special Issue Nanomaterials-Based Solutions for Thermal Systems)

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20 pages, 2978 KiB

Open AccessArticle

Self-Healing Thiolated Pillar[5]arene Films Containing Moxifloxacin Suppress the Development of Bacterial Biofilms

by Dmitriy N. Shurpik, Yulia I. Aleksandrova, Olga A. Mostovaya, Viktoriya A. Nazmutdinova, Regina E. Tazieva, Fadis F. Murzakhanov, Marat R. Gafurov, Pavel V. Zelenikhin, Evgenia V. Subakaeva, Evgenia A. Sokolova, Alexander V. Gerasimov, Vadim V. Gorodov, Daut R. Islamov, Peter J. Cragg and Ivan I. Stoikov

Nanomaterials 2022, 12(9), 1604; https://doi.org/10.3390/nano12091604 - 9 May 2022

Cited by 11 | Viewed by 2344

Abstract

Polymer self-healing films containing fragments of pillar[5]arene were obtained for the first time using thiol/disulfide redox cross-linking. These films were characterized by thermogravimetric analysis and differential scanning calorimetry, FTIR spectroscopy, and electron microscopy. The films demonstrated the ability to self-heal through the action [...] Read more.

Polymer self-healing films containing fragments of pillar[5]arene were obtained for the first time using thiol/disulfide redox cross-linking. These films were characterized by thermogravimetric analysis and differential scanning calorimetry, FTIR spectroscopy, and electron microscopy. The films demonstrated the ability to self-heal through the action of atmospheric oxygen. Using UV–vis, 2D 1H-1H NOESY, and DOSY NMR spectroscopy, the pillar[5]arene was shown to form complexes with the antimicrobial drug moxifloxacin in a 2:1 composition (logK11 = 2.14 and logK12 = 6.20). Films containing moxifloxacin effectively reduced Staphylococcus aureus and Klebsiella pneumoniae biofilms formation on adhesive surfaces. Full article

(This article belongs to the Special Issue Functional Nanomaterials Based on Self-Assembly)

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11 pages, 7077 KiB

Open AccessArticle

A General Way to Fabricate Chain-like Ferrite with Ultralow Conductive Percolation Threshold and Wideband Absorbing Ability

by Cong Chen, Haitao Dong, Jiayuan Wang, Wen Chen, Denghui Li, Meng Cai and Kun Zhou

Nanomaterials 2022, 12(9), 1603; https://doi.org/10.3390/nano12091603 - 9 May 2022

Cited by 3 | Viewed by 1662

Abstract

The magnetic nanochain-like material has been regards as one of the most promising electromagnetic (EM) absorbing material but remains a challenging. Herein, magnetic chain-like ferrite (included Fe₃O_4, CoFe₂O₄ and NiFe₂O₄) are successfully produced [...] Read more.

The magnetic nanochain-like material has been regards as one of the most promising electromagnetic (EM) absorbing material but remains a challenging. Herein, magnetic chain-like ferrite (included Fe₃O_4, CoFe₂O₄ and NiFe₂O₄) are successfully produced through a general solvothermal method, using PVP as the structural-liking agent. Experimental results confirm the ultimate sample possess a 3-dimensional chain-like structure which are constructed by numerous ferrite’s nanoparticles with ~60 nm in diameter. Their electromagnetic parameters can be also manipulated by such a chain structure, especially the dielectric loss, where a sharply increases can be observed on within a lower filling ratio. It greatly benefits to the EM absorbing property. In this article, the electromagnetic absorption layer made with a lower content of ferrite possess the excellent electromagnetic absorption ability, where the optimized effective absorption band was nearly 6.4 GHz under a thickness of 1.8 mm. Moreover, the filling ratio is only 30 wt%. Our method for designing of chain-like magnetic material can be helpful for producing wideband electromagnetic absorption in a low filling ratio. Full article

(This article belongs to the Topic Synthesis and Applications of Nanostructured Metals and Metal Oxides)

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26 pages, 27272 KiB

Open AccessReview

Nanoparticles for Coronavirus Control

by Maryam Kianpour, Mohsen Akbarian and Vladimir N. Uversky

Nanomaterials 2022, 12(9), 1602; https://doi.org/10.3390/nano12091602 - 9 May 2022

Cited by 10 | Viewed by 2507

Abstract

More than 2 years have passed since the SARS-CoV-2 outbreak began, and many challenges that existed at the beginning of this pandemic have been solved. Some countries have been able to overcome this global challenge by relying on vaccines against the virus, and [...] Read more.

More than 2 years have passed since the SARS-CoV-2 outbreak began, and many challenges that existed at the beginning of this pandemic have been solved. Some countries have been able to overcome this global challenge by relying on vaccines against the virus, and vaccination has begun in many countries. Many of the proposed vaccines have nanoparticles as carriers, and there are different nano-based diagnostic approaches for rapid detection of the virus. In this review article, we briefly examine the biology of SARS-CoV-2, including the structure of the virus and what makes it pathogenic, as well as describe biotechnological methods of vaccine production, and types of the available and published nano-based ideas for overcoming the virus pandemic. Among these issues, various physical and chemical properties of nanoparticles are discussed to evaluate the optimal conditions for the production of the nano-mediated vaccines. At the end, challenges facing the international community and biotechnological answers for future viral attacks are reviewed. Full article

(This article belongs to the Special Issue Advanced Nanomaterials in Biomedical Application)

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The overall structure of CoV and the spike protein. The left side illustrates a single particle of CoV. Three membrane proteins and RNA viral genome in a complex with nucleocapsid proteins were shown in the scheme. The right side shows the detailed structure of a spike protein. This protein, which is the most important functional protein during the attachment of the viral particle to the host cell, has two subunits named S1 and S2. The receptor-binding domain is located at the top of S1. For more information see the text. The structure of the spike protein was extracted from PDB 6ZGI [<a href="#B29-nanomaterials-12-01602" class="html-bibr">29</a>]. RBD is receptor-binding domain. Full article ">Figure 2
Immune responses and overall intracellular events triggered in the face of CoV-2. In normal conditions, immune cells enter the alveoli of the lungs through the blood. When CoV arrives in the alveolar compartment, these immune cells oppose them and eventually produce cytokines. Positively regulating, cytokines trigger more immune cells, eventually producing more cytokines. During these events, the fibrin of the alveoli increases, resulting in partial destruction and increased permeability of the alveoli. Consequently, fluid goes on the battlefield (alveoli) through the capillaries, causing destruction and edema of the infected lung. However, when a virus can compete with these challenges, it will be able to enter the host cell. In the host cell, the viral genome is generally released and the host equipment is used to replicate the viral particles. The following sections of the article provide more details in this regard. Full article ">Figure 3
Various chemical and physical properties that can determine how nanoparticles will act as vaccine carriers. The size, hydrophobicity, charge, shape, and ligand density of the nanoparticles that carry the therapeutic factor will have a significant effect on their cellular uptake, distribution in the body, accumulation in the cell (especially phagocytic cells) and the rate of tissue penetration. Full article ">Figure 4
Different classes of nanoparticles are used as virus vaccines. (A) Self-assembling capsid protein nanoparticle. This type of nanoparticle is made up entirely of proteins that are able to self-aggregate. Sometimes two or three types of proteins are used to make this nanoparticle. (B) Virus-like particle. Particle engineering has created the ability to design and synthesize a virus-like particle that is an assembly of a phospholipid and a set of viral proteins. (C) Liposome. Liposomes are free of any viral proteins on their surface. Sometimes they may have receptors for the correct targeting of the particle, but it should be noted that viral proteins are trapped inside the liposome structure and enter the immunological pathways into the host cell after the endocytosis of the particle. (D) Exosome particle. Once the host cell is infected with the virus, an exosome will emerge from the damaged cell that contain the newly synthesized viruses. These particles, after extraction and purification, can be suitable treatment options. (E) Corresponds many available nano-based polymeric materials that functionalized with different therapeutic agents such as DNA, RNA, antigens, peptides, and antibodies. Full article ">Figure 5
The role of different nanoparticles containing therapeutic agents. Different nanoparticles have been used to carry different components of viral particles such as genetic material and/or its antigens. The viral genetic materials are usually encapsulated or trapped inside the nanoparticles while the viral antigens are functionalized on the surface of the nanoparticles. Depending on which type of T-cell or antigen-presenting cells these engineered nanoparticles attach to, different immunological pathways are created in the body, which ultimately lead to the activation of B cells that produce monoclonal antibodies against the virus particle. Full article ">Figure 6
Different stages of a CoV-2 life cycle along with target points for fighting the virus. The CoVs can be fought almost from the beginning of the virus to the function of the RNA-dependent RNA polymerase. However, after the function of the enzyme, no specific strategy has been proposed to deal with the virus. As soon as the virus enters the body, a range of events will occur, though up to stage, 5 the virus can still be defeated. Nanoparticles that have monoclonal antibodies or antigens on their surface usually act before the virus enters the cell. The ACE2 receptor, which is among the most important cell surface receptors for the SARS-CoV-2, was a target of many studies for blocking virus cell entry. As soon as the virus binds to this receptor, the process of virus penetration into the host cell begins. Consequently, masking this agent on the surface of host cells can prevent the virus from entering the cell. Nanoparticles that encapsulated therapeutic agents will be able to fight the virus as it enters the host cell. See the text for more details. Full article ">Figure 7
Different strategies used for the detection of SARS-CoV-2 by nanoparticles (A,B) and/or fluorescently labeled nanoparticles (C). Full article ">

16 pages, 3441 KiB

Open AccessArticle

Facile Morphology and Porosity Regulation of Zeolite ZSM-5 Mesocrystals with Synergistically Enhanced Catalytic Activity and Shape Selectivity

by Feng Lin, Zhaoqi Ye, Lingtao Kong, Peng Liu, Yahong Zhang, Hongbin Zhang and Yi Tang

Nanomaterials 2022, 12(9), 1601; https://doi.org/10.3390/nano12091601 - 9 May 2022

Cited by 6 | Viewed by 2361

Abstract

The morphology and mesoporosity of zeolite are two vital properties to determine its performance in diverse applications involving adsorption and catalysis; while it remains a big challenge for the synthesis and regulation of zeolites with exceptional morphology/porosity only through inorganic-ions-based modification. Herein, by [...] Read more.

The morphology and mesoporosity of zeolite are two vital properties to determine its performance in diverse applications involving adsorption and catalysis; while it remains a big challenge for the synthesis and regulation of zeolites with exceptional morphology/porosity only through inorganic-ions-based modification. Herein, by simply optimizing the alkali metal type (K⁺ or Na⁺), as well as alkali/water ratio and crystallization temperature, the zeolite ZSM-5 mesocrystals with diverse mesostructures are simply and controllably prepared via fine-tuning the crystallization mechanism in an organotemplate-free, ions-mediated seed-assisted system. Moreover, the impacts of these key parameters on the evolution of seed crystals, the development and assembly behavior of aluminosilicate species and the solution-phase process during zeolite crystallization are investigated by means of directional etching in NH₄F or NaOH solutions. Except for the morphology/mesoporosity modulation, their physical and chemical properties, such as particle size, microporosity, Si/Al ratio and acidity, can be well maintained at a similar level. As such, the p/o-xylene adsorption and catalytic performance of o-xylene isomerization are used to exhaustively evaluate the synergistically enhanced catalytic activity and shape selectivity of the obtained products. This work demonstrates the possibility of effectively constructing novel zeolite mesostructures by simply altering parameters on simple ions-controlled crystallization and provides good models to inspect the impacts of mesoporosity or morphology on their catalytic performances. Full article

(This article belongs to the Special Issue Nanoporous Materials for Catalysis, Molecule Separation and Nanodevices)

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18 pages, 3459 KiB

Open AccessEditor’s ChoiceArticle

In-Situ Imaging of a Light-Induced Modification Process in Organo-Silica Films via Time-Domain Brillouin Scattering

by Sathyan Sandeep, Alexey S. Vishnevskiy, Samuel Raetz, Sergej Naumov, Dmitry S. Seregin, Artem Husiev, Konstantin A. Vorotilov, Vitalyi E. Gusev and Mikhail R. Baklanov

Nanomaterials 2022, 12(9), 1600; https://doi.org/10.3390/nano12091600 - 9 May 2022

Cited by 4 | Viewed by 2198

Abstract

We applied time-domain Brillouin scattering (TDBS) for the characterization of porogen-based organosilicate glass (OGS) films deposited by spin-on-glass technology and cured under different conditions. Although the chemical composition and porosity measured by Fourier-transform infrared (FTIR) spectroscopy and ellipsometric porosimetry (EP) did not show [...] Read more.

We applied time-domain Brillouin scattering (TDBS) for the characterization of porogen-based organosilicate glass (OGS) films deposited by spin-on-glass technology and cured under different conditions. Although the chemical composition and porosity measured by Fourier-transform infrared (FTIR) spectroscopy and ellipsometric porosimetry (EP) did not show significant differences between the films, remarkable differences between them were revealed by the temporal evolution of the Brillouin frequency (BF) shift of the probe light in the TDBS. The observed modification of the BF was a signature of the light-induced modification of the films in the process of the TDBS experiments. It correlated to the different amount of carbon residue in the samples, the use of ultraviolet (UV) femtosecond probe laser pulses in our optical setup, and their intensity. In fact, probe radiation with an optical wavelength of 356 nm appeared to be effective in removing carbon residue through single-photon absorption processes, while its two-photon absorption might have led to the breaking of Si-CH₃ bonds in the OSG matrix. The quantum chemical calculations confirmed the latter possibility. This discovery demonstrates the possibility of local modifications of OSG films with a nanometric resolution via nonlinear optical processes, which could be important, among other applications, for the creation of active surface sites in the area-selective deposition of atomic layers. Full article

(This article belongs to the Special Issue Advances in Laser-Based Techniques: From Fundamental Aspects to Applications)

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Changes in the low-k thickness and refractive index during the curing of a porogen-based low-k film. The curing curve is partially redrawn from [<a href="#B9-nanomaterials-12-01600" class="html-bibr">9</a>]. The curing time is represented in arbitrary units because it depends on conditions. The region between the dashed curves corresponds to 1–2 h in pure thermal curing but can be reduced to 5–12 min if the curing is assisted by UV light as in [<a href="#B5-nanomaterials-12-01600" class="html-bibr">5</a>]. The sketches in the subfigures (a–d) qualitatively visualize the state of the low-k film in the positions (a–d) indicated by the arrows in the main part of the figure. (a) The film before curing (soft baked film). (a,b) The removal of porogen causes the reduction in RI and thickness of the film. (b,c) The porogen is removed, but some residues can remain. (c,d) The matrix densification related to the dissociation of some Si-CH3 bonds and the collapse of a part of the nanopores causes increase in the RI. Full article ">Figure 2
(a) Scheme of the experimental setup based on asynchronous optical sampling, where accumulating time delay between pump and probe femtosecond laser pulses is due to the difference in the repetition rate of two lasers. (b) Scheme of our TDBS experiment, where the absorption of the pump laser pulse in the Al film launches a coherent acoustic pulse (CAP) with a length of less than 25 nm in a low-k film and an Al layer. Scattering time-delayed probe light pulses by a CAP provides information on film properties in the current position of the CAP inside the film [<a href="#B2-nanomaterials-12-01600" class="html-bibr">2</a>,<a href="#B3-nanomaterials-12-01600" class="html-bibr">3</a>]. Particularly, the period of oscillating component in the presented time-domain transient optical reflectivity signals dR/R, as an inset in the screen of (a), is proportional to the product of local optical refractive index and sound velocity. (c) Illustration of the unwanted situation where the CAP propagating (a) in Al after partial reflection at Si/Al interface reaches the Al/low-k film interface and transmits a second CAP in the low-k film, which would scatter probe light simultaneously with the first CAP. Full article ">Figure 3
FTIR spectra of low-k films deposited and studied in this work: after hard-baking at 400 °C for 1 and 2 h in nitrogen (1 hN and 2 hN) and air (1 hA and 2 hA). Full article ">Figure 4
Vertically shifted normalized transient optical reflectivity signals ∆R/R recorded in the films (a) 1 hN and (b) 1 hA with a 26 mW pump power and a 1 mW probe power at different time points (right vertical axis) from the beginning of the TDBS experiment. Experimental time increases from the bottom to the top of each figure. The time interval along the horizontal axis between the two orange lines, passing the neighbor maxima of the Brillouin oscillations, provides an estimate of their period, i.e., the inverse of the Brillouin frequency (BF) in Equation (2). The revealed variation of the BF with experimental time in (a) is a signature of an additional curing of low-k films by laser light. Full article ">Figure 5
Changes in Brillouin frequency with the duration of the TDBS measurements at different powers of probe laser pulses (marked on the top of the figure) with a 26 mW pump power in the 1 hN (first row, (a–d)), 2 hN (second row, (e–h)), 1 hA (third row, (i–l)), and 2 hA (last row, (m–p)) samples. Full article ">Figure 6
Changes in Brillouin frequency with the duration of the TDBS measurements at different powers of pump laser pulses (marked at the top of the figure) with a 3 mW probe power in the 1 hN (first row, (a–c)), 2 hN (second row, (d–f)), 1 hA (third row, (g–i)), and 2 hA (last row, (j–l)) samples. Full article ">Figure 7
Irreversibility of the curing process demonstrated by the measurements of the acoustically induced transient optical reflectivity ∆R/R accompanied by the interruption of the experiments for 1 h after the first 5 min of the measurements. The green and red lines, passing through the maxima and minima of the first Brillouin oscillation, indicate a continuous diminishing of the Brillouin frequency with increasing experimental time. No increase in the Brillouin frequency was observed during the time when the experiment was stopped. Full article ">Figure 8
(a) Jablonski energy scheme of the population of the reactive triplet by two-photon excitation of the studied model molecule. (b) Calculated UV-Vis spectra; f-oscillator strength. (c) Electron distribution of σ-electrons from HOMO involved in the formation of the first S1 excited state. Full article ">

13 pages, 8224 KiB

Open AccessArticle

Three-Phase Mixed Titania Powder Modified by Silver and Silver Chloride with Enhanced Photocatalytic Activity under UV–Visible Light

by Xiaodong Zhu, Fengqiu Qin, Yangwen Xia, Daixiong Yang, Wei Feng and Yu Jiao

Nanomaterials 2022, 12(9), 1599; https://doi.org/10.3390/nano12091599 - 9 May 2022

Cited by 13 | Viewed by 4692

Abstract

Pure and Ag/AgCl-modified titania powders with anatase/rutile/brookite three-phase mixed structure were prepared by one-step hydrothermal method. The effects of Ag/Ti atomic percentages on the structure and photocatalytic performance of TiO₂ were investigated. The results showed that pure TiO₂ consisted of three [...] Read more.

Pure and Ag/AgCl-modified titania powders with anatase/rutile/brookite three-phase mixed structure were prepared by one-step hydrothermal method. The effects of Ag/Ti atomic percentages on the structure and photocatalytic performance of TiO₂ were investigated. The results showed that pure TiO₂ consisted of three phases, anatase, rutile, and brookite, and that Ag addition promoted the transformation from anatase to rutile. When the molar ratio of Ag/Ti reached 4%, the AgCl phase appeared. The addition of Ag had little effect on the optical absorption of TiO₂; however, it did favor the separation of photogenerated electrons and holes. The results of photocatalytic experiments showed that after Ag addition, the degradation degree of rhodamine B (RhB) was enhanced. When the molar ratio of Ag/Ti was 4%, Ag/AgCl-modified TiO₂ exhibited the highest activity, and the first-order reaction rate constant was 1.67 times higher than that of pure TiO₂. Full article

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11 pages, 4071 KiB

Open AccessArticle

The Effect of Agglomeration on Arsenic Adsorption Using Iron Oxide Nanoparticles

by William R. Diephuis, Anna L. Molloy, Lindsey L. Boltz, Tristan B. Porter, Anthony Aragon Orozco, Reina Duron, Destiny Crespo, Luke J. George, Andrew D. Reiffer, Gabriela Escalera, Arash Bohloul, Carolina Avendano, Vicki L. Colvin and Natalia I. Gonzalez-Pech

Nanomaterials 2022, 12(9), 1598; https://doi.org/10.3390/nano12091598 - 9 May 2022

Cited by 11 | Viewed by 2527

Abstract

The presence of arsenic in groundwater and other drinking water sources presents a notable public health concern. Although the utilization of iron oxide nanomaterials as arsenic adsorbents has shown promising results in batch experiments, few have succeeded in using nanomaterials in filter setups. [...] Read more.

The presence of arsenic in groundwater and other drinking water sources presents a notable public health concern. Although the utilization of iron oxide nanomaterials as arsenic adsorbents has shown promising results in batch experiments, few have succeeded in using nanomaterials in filter setups. In this study, the performance of nanomaterials, supported on sand, was first compared for arsenic adsorption by conducting continuous flow experiments. Iron oxide nanoparticles (IONPs) were prepared with different synthetic methodologies to control the degree of agglomeration. IONPs were prepared by thermal decomposition or coprecipitation and compared with commercially available IONPs. Electron microscopy was used to characterize the degree of agglomeration of the pristine materials after deposition onto the sand. The column experiments showed that IONPs that presented less agglomeration and were well dispersed over the sand had a tendency to be released during water treatment. To overcome this implementation challenge, we proposed the use of clusters of iron oxide nanoparticles (cIONPs), synthesized by a solvothermal methodology, which was explored. An isotherm experiment was also conducted to determine the arsenic adsorption capacities of the iron oxide nanomaterials. cIONPs showed higher adsorption capacities (121.4 mg/g) than the other IONPs (11.1, 6.6, and 0.6 mg/g for thermal decomposition, coprecipitation, and commercially available IONPs, respectively), without the implementation issues presented by IONPs. Our results show that the use of clusters of nanoparticles of other compositions opens up the possibilities for multiple water remediation applications. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Adsorption Purposes)

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IONPs prepared by different methods of synthesis: TEM images of magnetite nanoparticles prepared by thermal decomposition (a), coprecipitation (b), and commercially (c) are shown. Full article ">Figure 2
SEM images of sand covered with IONPs of different agglomeration degrees: SEM images of sand covered without and with IONPs at lower (a–d) and higher (e–h) resolution are shown. The sand surface (a,e) was covered with IONPs prepared via thermal decomposition (b,f), coprecipitation (c,g), or commercially (d,h). Full article ">Figure 3
Column experiments of sand covered with IONPs: Small scale columns were performed with IONPs loaded in sand. The active beds were prepared by adding 1 wt% IONPs prepared via thermal decomposition (a), and 20 wt% IONPs prepared via coprecipitation (b) and commercially (c). A 100 ppb As solution (pH 7) was used as the feeding solution. The experimental data is shown with black squares while the red line represents the fitting model. Full article ">Figure 4
Clusters of IONPs prepared via solvothermal synthesis: SEM images of clusters of iron oxide nanoparticles at two different magnifications (a,b) are shown. Full article ">Figure 5
Column experiment for sand covered with lusters of iron oxide nanoparticles: image of the column with a 20%wt loading of clusters of iron oxide nanoparticles onto sand (a) used in a small scale column experiment (b). The experimental data is shown with black squares while the red line represents the fitting model. Full article ">Figure 6
Adsorption isotherms of IONPs prepared via different methods of synthesis: adsorption isotherms are shown for IONPs prepared via thermal decomposition (purple circles), coprecipitation (cyan triangles), commercial (black squares), and solvothermal (orange stars). Full article ">

4 pages, 210 KiB

Open AccessEditorial

Carbon Nanomaterials for Therapy, Diagnosis and Biosensing

by Antonino Mazzaglia and Anna Piperno

Nanomaterials 2022, 12(9), 1597; https://doi.org/10.3390/nano12091597 - 9 May 2022

Cited by 5 | Viewed by 1477

Abstract

In carbon nanomaterial design, the fine-tuning of their functionalities and physicochemical properties has increased their potential for therapeutic, diagnostic and biosensing applications [...] Full article

(This article belongs to the Special Issue Carbon Nanomaterials for Therapy, Diagnosis, and Biosensing)

13 pages, 2076 KiB

Open AccessArticle

Fungus-Based MnO/Porous Carbon Nanohybrid as Efficient Laccase Mimic for Oxygen Reduction Catalysis and Hydroquinone Detection

by Haoran Ge and Hailong Zhang

Nanomaterials 2022, 12(9), 1596; https://doi.org/10.3390/nano12091596 - 8 May 2022

Cited by 8 | Viewed by 2187

Abstract

Developing efficient laccase-mimicking nanozymes via a facile and sustainable strategy is intriguing in environmental sensing and fuel cells. In our work, a MnO/porous carbon (MnO/PC) nanohybrid based on fungus was synthesized via a facile carbonization route. The nanohybrid was found to possess excellent [...] Read more.

Developing efficient laccase-mimicking nanozymes via a facile and sustainable strategy is intriguing in environmental sensing and fuel cells. In our work, a MnO/porous carbon (MnO/PC) nanohybrid based on fungus was synthesized via a facile carbonization route. The nanohybrid was found to possess excellent laccase-mimicking activity using 2,2′-azinobis (3-ethylbenzthiazoline-6-sulfonic acid) diammonium salt (ABTS) as the substrate. Compared with the natural laccase and reported nanozymes, the MnO/PC nanozyme had much lower K_m value. Furthermore, the electrochemical results show that the MnO/PC nanozyme had high electrocatalytic activity toward the oxygen reduction reaction (ORR) when it was modified on the electrode. The hybrid nanozyme could catalyze the four-electron ORR, similar to natural laccase. Moreover, hydroquinone (HQ) induced the reduction of oxABTS and caused the green color to fade, which provided colorimetric detection of HQ. A desirable linear relationship (0–50 μM) and detection limit (0.5 μM) were obtained. Our work opens a simple and sustainable avenue to develop a carbon–metal hybrid nanozyme in environment and energy applications. Full article

(This article belongs to the Special Issue Nanomaterials for Sensing Application)

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(A,B) SEM images of MnO/PC nanohybrid with different magnifications. EDX spectroscopy (C), XRD patterns (D), XPS survey scan (E), and high-resolution Mn 2p XPS spectrum (F) of MnO/PC nanohybrid. Full article ">Figure 2
(A) Typical UV-vis spectra of different systems: (a) ABTS + buffer, (b) ABTS + Mn(Ac)2 + buffer, (c) ABTS + PC + buffer, and (d) ABTS + MnO/PC nanohybrid + buffer. (B) Steady-state kinetic assay and kinetic analysis by double reciprocal plots (inset) of the MnO/PC nanohybrid with ABTS as the substrate. Full article ">Figure 3
(A) CV curves of MnO/PC nanohybrid at 20 mV s−1 in N2 and O2-saturated 0.1 M KOH. (B) LSV curves of MnO/PC nanohybrid at different electrode rotation rates in O2-saturated 0.1 M KOH. Inset shows K–L plots of ORR. (C) RRDE voltammograms of the MnO/PC nanohybrid, MnO/PC-700 nanohybrid, and 20% Pt/C in O2-saturated 0.1 M KOH at 1600 rpm. (D) The transferred electron number (n) and HO2− H2O2 yield derived from the RRDE measurements in (C). Full article ">Figure 4
(A) The absorbance spectra of the MnO/PC-ABTS system in the presence of different concentrations of HQ (0−60 μM). (B) The linearity of the detection against the concentration of HQ, ranging from 0 to 50 μM. Full article ">Scheme 1
Fungus-based MnO/PC nanohybrid as laccase mimic for ORR and HQ detection. Full article ">Scheme 2
Schematic illustration of the synthesis of MnO/PC nanohybrid based on the tremella. Full article ">Scheme 3
The schematic mechanism of colorimetric detection of HQ based on the MnO/PC nanohybrid. (a) ABTS changed into green-colored oxABTS due to the superior laccase-like activity of the MnO/PC nanohybrid, (b) Green-colored oxABTS changed back into colorless ABTS due to the redox reaction. Full article ">

20 pages, 3758 KiB

Open AccessFeature PaperArticle

Band Gap Engineering of Newly Discovered ZnO/ZnS Polytypic Nanomaterials

by Dejan Zagorac, Jelena Zagorac, Milan Pejić, Branko Matović and Johann Christian Schön

Nanomaterials 2022, 12(9), 1595; https://doi.org/10.3390/nano12091595 - 8 May 2022

Cited by 15 | Viewed by 2694

Abstract

We report on a new class of ZnO/ZnS nanomaterials based on the wurtzite/sphalerite architecture with improved electronic properties. Semiconducting properties of pristine ZnO and ZnS compounds and mixed ZnO_1−xS_x nanomaterials have been investigated using ab initio methods. In particular, we [...] Read more.

We report on a new class of ZnO/ZnS nanomaterials based on the wurtzite/sphalerite architecture with improved electronic properties. Semiconducting properties of pristine ZnO and ZnS compounds and mixed ZnO_1−xS_x nanomaterials have been investigated using ab initio methods. In particular, we present the results of our theoretical investigation on the electronic structure of the ZnO_1−xS_x (x = 0.20, 0.25, 0.33, 0.50, 0.60, 0.66, and 0.75) nanocrystalline polytypes (2H, 3C, 4H, 5H, 6H, 8H, 9R, 12R, and 15R) calculated using hybrid PBE0 and HSE06 functionals. The main observations are the possibility of alternative polytypic nanomaterials, the effects of structural features of such polytypic nanostructures on semiconducting properties of ZnO/ZnS nanomaterials, the ability to tune the band gap as a function of sulfur content, as well as the influence of the location of sulfur layers in the structure that can dramatically affect electronic properties. Our study opens new fields of ZnO/ZnS band gap engineering on a multi-scale level with possible applications in photovoltaics, light-emitting diodes, laser diodes, heterojunction solar cells, infrared detectors, thermoelectrics, or/and nanostructured ceramics. Full article

(This article belongs to the Special Issue Nanostructured Ceramics in Modern Materials Science)

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13 pages, 2997 KiB

Open AccessEditor’s ChoiceArticle

Graphene-Based Temperature Sensors–Comparison of the Temperature and Humidity Dependences

by Jiří Štulík, Ondřej Musil, František Josefík and Petr Kadlec

Nanomaterials 2022, 12(9), 1594; https://doi.org/10.3390/nano12091594 - 7 May 2022

Cited by 15 | Viewed by 3559

Abstract

Four different graphene-based temperature sensors were prepared, and their temperature and humidity dependences were tested. Sensor active layers prepared from reduced graphene oxide (rGO) and graphene nanoplatelets (Gnp) were deposited on the substrate from a dispersion by air brush spray coating. Another sensor [...] Read more.

Four different graphene-based temperature sensors were prepared, and their temperature and humidity dependences were tested. Sensor active layers prepared from reduced graphene oxide (rGO) and graphene nanoplatelets (Gnp) were deposited on the substrate from a dispersion by air brush spray coating. Another sensor layer was made by graphene growth from a plasma discharge (Gpl). The last graphene layer was prepared by chemical vapor deposition (Gcvd) and then transferred onto the substrate. The structures of rGO, Gnp, and Gpl were studied by scanning electron microscopy. The obtained results confirmed the different structures of these materials. Energy-dispersive X-ray diffraction was used to determine the elemental composition of the materials. Gcvd was characterized by X-ray photoelectron spectroscopy. Elemental analysis showed different oxygen contents in the structures of the materials. Sensors with a small flake structure, i.e., rGO and Gnp, showed the highest change in resistance as a function of temperature. The temperature coefficient of resistance was 5.16⁻³·K⁻¹ for Gnp and 4.86⁻³·K⁻¹ for rGO. These values exceed that for a standard platinum thermistor. The Gpl and Gcvd sensors showed the least dependence on relative humidity, which is attributable to the number of oxygen groups in their structures. Full article

(This article belongs to the Special Issue Graphene Sensors)

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Full article ">Figure 1
Images of alumina substrate with interdigital electrodes: (a) whole substrate; (b) detail of the interdigital electrodes. Full article ">Figure 2
SEM images of prepared graphene layers of the tested sensors and results of chemical element content analysis by EDS for (a) rGO, (b) Gnp, and (c) Gpl and (d) XPS spectrum of prepared graphene on copper foil (Gcvd). Full article ">Figure 3
Response of the Gcvd sensor to temperature changes at different DC bias voltage levels. Full article ">Figure 4
Summary of the time dependences of relative changes in resistance and temperature during climatic testing for (a) rGO, (b) Gnp, (c) Gpl, and (d) Gcvd and the temperature dependences of steady-state resistance at each step of testing for (e) rGO, (f) Gnp, (g) Gpl, and (h) Gcvd. Full article ">Figure 5
Logarithm of resistivity versus reciprocal temperature and confirmation of linearity, including the coefficient of determination, for (a) rGO, (b) Gnp, (c) Gpl, and (d) Gcvd. Full article ">Figure 6
Sensors’ response time to temperature step change from 20 °C to 30 °C with the marked value t90 for each sensor (and also temperature rise). Full article ">Figure 7
Humidity dependences of graphene-based materials (a) at 20 °C during the RH test and (b) at 50 °C during the RH test. Full article ">

14 pages, 2915 KiB

Open AccessArticle

Iron Single Atoms Anchored on Nitrogen-Doped Carbon Matrix/Nanotube Hybrid Supports for Excellent Oxygen Reduction Properties

by Yining Jia, Chunjing Shi, Wei Zhang, Wei Xia, Ming Hu, Rong Huang and Ruijuan Qi

Nanomaterials 2022, 12(9), 1593; https://doi.org/10.3390/nano12091593 - 7 May 2022

Cited by 2 | Viewed by 2275

Abstract

Single-atom non-precious metal oxygen reduction reaction (ORR) catalysts have attracted much attention due to their low cost, high selectivity, and high activity. Herein, we successfully prepared iron single atoms anchored on nitrogen-doped carbon matrix/nanotube hybrid supports (FeSA-NC/CNTs) by the pyrolysis of Fe-doped zeolitic [...] Read more.

Single-atom non-precious metal oxygen reduction reaction (ORR) catalysts have attracted much attention due to their low cost, high selectivity, and high activity. Herein, we successfully prepared iron single atoms anchored on nitrogen-doped carbon matrix/nanotube hybrid supports (FeSA-NC/CNTs) by the pyrolysis of Fe-doped zeolitic imidazolate frameworks. The nitrogen-doped carbon matrix/carbon nanotube hybrid supports exhibit a specific surface area of 1626.814 m² g⁻¹, which may facilitate electron transfer and oxygen mass transport within the catalyst and be beneficial to ORR performance. Further electrochemical results revealed that our FeSA-NC/CNTs catalyst exhibited excellent ORR activity (half-wave potential: 0.86 V; kinetic current density: 39.3 mA cm⁻² at 0.8 V), superior to that of commercial Pt/C catalyst (half-wave potential: 0.846 V; kinetic current density: 14.4 mA cm⁻² at 0.8 V). It also has a great stability, which makes it possible to be a valuable non-noble metal electrode material that may replace the latest commercial Pt/C catalyst in the future. Full article

(This article belongs to the Special Issue Low-Dimensional Nanomaterials and Their Applications)

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The schematic illustration of FeSA-NC/CNTs. Full article ">Figure 2
SEM images of (a) Fe(acac)3-0.1@ZIF-8 and (b) FeSA-NC/CNTs. (c) TEM and (d) HRTEM images of FeSA-NC/CNTs. (e–h) STEM-EDS elemental maps of C, Fe, and N of the FeSA-NC/CNTs sample shown in (e). AC-HAADF-STEM images of (i) N-doped carbon matrix and (j) carbon nanotubes, corresponding to the blue and yellow areas in (c), respectively. (k) Electron energy-loss spectroscopy showing the C K-edge, N K-edge, and Fe L-edge acquired from the marked region in (c). Full article ">Figure 3
(a) XRD patterns of ZIF precursors and as-pyrolyzed samples. (b) Raman spectra. (c) XPS survey scan spectrum of FeSA-NC/CNTs. (d) High resolution XPS N 1s spectra of FeSA-NC/CNTs. Full article ">Figure 4
(a) Fe K-edge XANES spectra of FeSA-NC/CNTs (the orange area highlights the near-edge absorption energy). (b) Fourier transform (FT) of the Fe K-edge EXAFS spectra. (c) The corresponding EXAFS r space fitting curves of FeSA-NC/CNTs. Wavelet transform (WT) of Fe K-edge for (d) Fe foil, (e) FePc, and (f) FeSA-NC/CNTs. Full article ">Figure 5
(a) ORR polarization plots of FeSA-NC/CNTs and Pt/C in O2-saturated 0.1 M KOH with a sweep rate of 5 mV s−1 and 1600 rpm. (b) E1/2 and JK at 0.8 V for different catalysts. (c) LSV curves of FeSA-NC/CNTs with various rotation rates (inset: K–L plots). (d) Electron transfer number and H2O2 yield in ORR on FeSA-NC/CNTs from the RRDE results. (e) Tafel plots of Pt/C and FeSA-NC/CNTs. (f) LSV curves of FeSA-NC/CNTs before and after 5000 potential cycles. Full article ">

19 pages, 7123 KiB

Open AccessArticle

Effect of Tube Diameters and Functional Groups on Adsorption and Suspension Behaviors of Carbon Nanotubes in Presence of Humic Acid

by Mengyuan Fang, Tianhui Zhao, Xiaoli Zhao, Zhi Tang, Shasha Liu, Junyu Wang, Lin Niu and Fengchang Wu

Nanomaterials 2022, 12(9), 1592; https://doi.org/10.3390/nano12091592 - 7 May 2022

Cited by 3 | Viewed by 1930

Abstract

The adsorption and suspension behaviors of carbon nanotubes (CNTs) in the water environment determine the geochemical cycle and ecological risk of CNTs and the compounds attached to them. In this study, CNTs were selected as the research object, and the effect of tube [...] Read more.

The adsorption and suspension behaviors of carbon nanotubes (CNTs) in the water environment determine the geochemical cycle and ecological risk of CNTs and the compounds attached to them. In this study, CNTs were selected as the research object, and the effect of tube diameters and functional groups (multiwall CNTs (MWNTs) and hydroxylated MWNTs (HMWNTs)) on the adsorption and suspension behaviors of the CNTs in the presence of humic acid (HA) was systematically analyzed. The results indicate that HA adsorption decreased with the increase in the solution pH, and the adsorption amount and rate were negatively correlated with the tube diameter of the CNTs. The surface hydroxylation of the CNTs prevented the adsorption of HA, and the maximum adsorption amounts on the MWNTs and HMWNTs were 195.95 and 74.74 mg g⁻¹, respectively. HA had an important effect on the suspension of the CNTs, especially for the surface hydroxylation, and the suspension of the CNTs increased with the increase in the tube diameter. The characteristics of the CNTs prior to and after adsorbing HA were characterized by transmission electron microscopy, fluorescence spectroscopy, Fourier-transform infrared spectroscopy and Raman spectroscopy. The results indicate that surface hydroxylation of the CNTs increased the adsorption of aromatic compounds, and that the CNTs with a smaller diameter and a larger specific surface area had a disordered carbon accumulation microstructure and many defects, where the adsorption of part of the HA would cover the defects on the CNTs’ surface. Density functional theory (DFT) calculations demonstrated that HA was more easily adsorbed on the CNTs without surface hydroxylation. This investigation is helpful in providing a theoretical basis for the scientific management of the production and application of CNTs, and the scientific assessment of their geochemical cycle and ecological risk. Full article

(This article belongs to the Special Issue Nanomaterials Ecotoxicity Evaluation)

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17 pages, 3236 KiB

Open AccessArticle

Mechanism-Enhanced Active Attapulgite-Supported Nanoscale Zero-Valent Iron for Efficient Removal of Pb²⁺ from Aqueous Solution

by Liang Dai, Kai Meng, Weifan Zhao, Tao Han, Zhenle Lei, Gui Ma, Xia Tian and Jun Ren

Nanomaterials 2022, 12(9), 1591; https://doi.org/10.3390/nano12091591 - 7 May 2022

Cited by 6 | Viewed by 1675

Abstract

In this study, attapulgite-supported nano zero-valent iron (nZVI@ATP) was synthesized by a liquid-phase reduction method using active attapulgite (ATP) as raw material, and used for Pb²⁺ remediation in aqueous solution. To understand the mechanism of Pb²⁺ removal, various techniques were used [...] Read more.

In this study, attapulgite-supported nano zero-valent iron (nZVI@ATP) was synthesized by a liquid-phase reduction method using active attapulgite (ATP) as raw material, and used for Pb²⁺ remediation in aqueous solution. To understand the mechanism of Pb²⁺ removal, various techniques were used to characterize nZVI@ATP. The results showed that spherical nZVI particles were uniformly dispersed on the surface of ATP, and the agglomeration of nZVI particles was significantly weakened. The adsorption performance of nZVI@ATP for Pb²⁺ was greatly improved compared with that of ATP ore, in which the Fe/ATP mass ratio of 1:2 was the best loading ratio. Under the conditions of a temperature of 25 °C and a pH of 5.00, the initial concentration of Pb²⁺ was 700 mg/L, and the Pb²⁺ removal rate of nZVI@ATP was 84.47%. The adsorption of nZVI@ATP to Pb²⁺ was mainly a spontaneous endothermic reaction of heterogeneous surfaces, and the adsorption rate of nZVI@ATP to Pb²⁺ was proportional to pH in the range of 2–5.5. The presence of Na⁺, Mg²⁺, and Ca²⁺ can inhibit the removal of Pb²⁺, and Ca²⁺ has the strongest inhibition effect on the removal of Pb²⁺. The removal mechanism of Pb²⁺ by nZVI@ATP obtained from SEM-EDS, BET, XRD, FTIR and XPS included reduction, precipitation, and the formation of complexes. Full article

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12 pages, 5341 KiB

Open AccessArticle

Ab Initio Study of Octane Moiety Adsorption on H- and Cl-Functionalized Silicon Nanowires

by Barbara Ferrucci, Francesco Buonocore, Simone Giusepponi, Awad Shalabny, Muhammad Y. Bashouti and Massimo Celino

Nanomaterials 2022, 12(9), 1590; https://doi.org/10.3390/nano12091590 - 7 May 2022

Cited by 3 | Viewed by 1719

Abstract

Using first-principles calculations based on density functional theory, we investigated the effects of surface functionalization on the energetic and electronic properties of hydrogenated and chlorinated silicon nanowires oriented along the <112> direction. We show that the band structure is strongly influenced by the [...] Read more.

Using first-principles calculations based on density functional theory, we investigated the effects of surface functionalization on the energetic and electronic properties of hydrogenated and chlorinated silicon nanowires oriented along the <112> direction. We show that the band structure is strongly influenced by the diameter of the nanowire, while substantial variations in the formation energy are observed by changing the passivation species. We modeled an octane moiety absorption on the (111) and (110) surface of the silicon nanowire to address the effects on the electronic structure of the chlorinated and hydrogenated systems. We found that the moiety does not substantially affect the electronic properties of the investigated systems. Indeed, the states localized on the molecules are embedded into the valence and conduction bands, with no generation of intragap energy levels and moderated change in the band gap. Therefore, Si-C bonds can enhance protection of the hydrogenated and chlorinated nanowire surfaces against oxidation without substantial modification of the electronic properties. However, we calculated a significant charge transfer from the silicon nanowires to the octane moiety. Full article

(This article belongs to the Special Issue Molecular Interfaces Based Nanotechnology)

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13 pages, 2992 KiB

Open AccessArticle

High-Efficiency Crystalline Silicon-Based Solar Cells Using Textured TiO₂ Layer and Plasmonic Nanoparticles

by Ali Elrashidi and Khaled Elleithy

Nanomaterials 2022, 12(9), 1589; https://doi.org/10.3390/nano12091589 - 7 May 2022

Cited by 6 | Viewed by 2354

Abstract

A high-efficiency crystalline silicon-based solar cell in the visible and near-infrared regions is introduced in this paper. A textured TiO₂ layer grown on top of the active silicon layer and a back reflector with gratings are used to enhance the solar cell [...] Read more.

A high-efficiency crystalline silicon-based solar cell in the visible and near-infrared regions is introduced in this paper. A textured TiO₂ layer grown on top of the active silicon layer and a back reflector with gratings are used to enhance the solar cell performance. The given structure is simulated using the finite difference time domain (FDTD) method to determine the solar cell’s performance. The simulation toolbox calculates the short circuit current density by solving Maxwell’s equation, and the open-circuit voltage will be calculated numerically according to the material parameters. Hence, each simulation process calculates the fill factor and power conversion efficiency numerically. The optimization of the crystalline silicon active layer thickness and the dimensions of the back reflector grating are given in this work. The grating period structure of the Al back reflector is covered with a graphene layer to improve the absorption of the solar cell, where the periodicity, height, and width of the gratings are optimized. Furthermore, the optimum height of the textured TiO₂ layer is simulated to produce the maximum efficiency using light absorption and short circuit current density. In addition, plasmonic nanoparticles are distributed on the textured surface to enhance the light absorption, with different radii, with radius 50, 75, 100, and 125 nm. The absorbed light energy for different nanoparticle materials, Au, Ag, Al, and Cu, are simulated and compared to determine the best performance. The obtained short circuit current density is 61.9 ma/cm², open-circuit voltage is 0.6 V, fill factor is 0.83, and the power conversion efficiency is 30.6%. The proposed crystalline silicon solar cell improves the short circuit current density by almost 89% and the power conversion efficiency by almost 34%. Full article

(This article belongs to the Special Issue Nanomaterials for Energy Harvesting)

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Schematic diagram of the proposed structure. Full article ">Figure 2
Light absorption for different Si thicknesses as a function of the wavelength. Full article ">Figure 3
3D illustration of (a) short circuit current density and (b) PCE as a function of grating width, X, grating height, h, and grating period, G. Full article ">Figure 4
Absorbance when for gratings structure and with/without graphene layer as a function of wavelength. Full article ">Figure 5
Jsc and PCE for TiO2 textured layer (0.5–2.5 µm). Full article ">Figure 6
Absorbance for different Al NPs radii as a function of wavelength. Full article ">Figure 7
Absorbed, transmitted, and reflected power for the proposed structure. Full article ">Figure 8
Absorbance for different plasmonic NPS, Cu, Au, Ag, and Al. Full article ">

15 pages, 3835 KiB

Open AccessArticle

Polyethylenimine-Coated Ultrasmall Holmium Oxide Nanoparticles: Synthesis, Characterization, Cytotoxicities, and Water Proton Spin Relaxivities

by Shuwen Liu, Huan Yue, Son Long Ho, Soyeon Kim, Ji Ae Park, Tirusew Tegafaw, Mohammad Yaseen Ahmad, Seungho Kim, Abdullah Khamis Ali Al Saidi, Dejun Zhao, Ying Liu, Sung-Wook Nam, Kwon Seok Chae, Yongmin Chang and Gang Ho Lee

Nanomaterials 2022, 12(9), 1588; https://doi.org/10.3390/nano12091588 - 7 May 2022

Cited by 4 | Viewed by 2518

Abstract

Water proton spin relaxivities, colloidal stability, and biocompatibility of nanoparticle magnetic resonance imaging (MRI) contrast agents depend on surface-coating ligands. In this study, hydrophilic and biocompatible polyethylenimines (PEIs) of different sizes (M_n = 1200 and 60,000 amu) were used as surface-coating ligands [...] Read more.

Water proton spin relaxivities, colloidal stability, and biocompatibility of nanoparticle magnetic resonance imaging (MRI) contrast agents depend on surface-coating ligands. In this study, hydrophilic and biocompatible polyethylenimines (PEIs) of different sizes (M_n = 1200 and 60,000 amu) were used as surface-coating ligands for ultrasmall holmium oxide (Ho₂O₃) nanoparticles. The synthesized PEI1200- and PEI60000-coated ultrasmall Ho₂O₃ nanoparticles, with an average particle diameter of 2.05 and 1.90 nm, respectively, demonstrated low cellular cytotoxicities, good colloidal stability, and appreciable transverse water proton spin relaxivities (r₂) of 13.1 and 9.9 s⁻¹mM⁻¹, respectively, in a 3.0 T MR field with negligible longitudinal water proton spin relaxivities (r₁) (i.e., 0.1 s⁻¹mM⁻¹) for both samples. Consequently, for both samples, the dose-dependent contrast changes in the longitudinal (R₁) and transverse (R₂) relaxation rate map images were negligible and appreciable, respectively, indicating their potential as efficient transverse T₂ MRI contrast agents in vitro. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Bioimaging)

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18 pages, 3925 KiB

Open AccessArticle

Sorption Profile of Low Specific Activity ⁹⁹Mo on Nanoceria-Based Sorbents for the Development of ^99mTc Generators: Kinetics, Equilibrium, and Thermodynamic Studies

by Mohamed F. Nawar, Alaa F. El-Daoushy, Metwally Madkour and Andreas Türler

Nanomaterials 2022, 12(9), 1587; https://doi.org/10.3390/nano12091587 - 7 May 2022

Cited by 4 | Viewed by 1713

Abstract

⁹⁹Mo/^99mTc generators play a significant role in supplying ^99mTc for diagnostic interventions in nuclear medicine. However, the applicability of using low specific activity (LSA) ⁹⁹Mo asks for sorbents with high sorption capacity. Herein, this study aims to evaluate [...] Read more.

⁹⁹Mo/^99mTc generators play a significant role in supplying ^99mTc for diagnostic interventions in nuclear medicine. However, the applicability of using low specific activity (LSA) ⁹⁹Mo asks for sorbents with high sorption capacity. Herein, this study aims to evaluate the sorption behavior of LSA ⁹⁹Mo towards several CeO₂ nano-sorbents developed in our laboratory. These nanomaterials were prepared by wet chemical precipitation (CP) and hydrothermal (HT) approaches. Then, they were characterized using XRD, BET, FE-SEM, and zeta potential measurements. Additionally, we evaluated the sorption profile of carrier-added (CA) ⁹⁹Mo onto each material under different experimental parameters. These parameters include pH, initial concentration of molybdate solution, contact time, and temperature. Furthermore, the maximum sorption capacities were evaluated. The results reveal that out of the synthesized CeO₂ nanoparticles (NPs) materials, the sorption capacity of HT-1 and CP-2 reach 192 ± 10 and 184 ± 12 mg Mo·g^–1, respectively. For both materials, the sorption kinetics and isotherm data agree with the Elovich and Freundlich models, respectively. Moreover, the diffusion study demonstrates that the sorption processes can be described by pore diffusion (for HT-synthesis route 1) and film diffusion (for CP-synthesis route 2). Furthermore, the thermodynamic parameters indicate that the Mo sorption onto both materials is a spontaneous and endothermic process. Consequently, it appears that HT-1 and CP-2 have favorable sorption profiles and high sorption capacities for CA-⁹⁹Mo. Therefore, they are potential candidates for producing a ⁹⁹Mo/^99mTc radionuclide generator by using LSA ⁹⁹Mo. Full article

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10 pages, 4504 KiB

Open AccessArticle

Structure and Magnetic Properties of ErFe_xMn_12−x (7.0 ≤ x ≤ 9.0, Δx = 0.2)

by Penglin Gao, Yuanhua Xia, Jian Gong and Xin Ju

Nanomaterials 2022, 12(9), 1586; https://doi.org/10.3390/nano12091586 - 7 May 2022

Cited by 4 | Viewed by 1506

Abstract

The magnetic interactions of iron-rich manganese-based ThMn₁₂ type rare earth metal intermetallic compounds are extremely complex. The antiferromagnetic structure sublattice and the ferromagnetic structure sublattice had coexisted and competed with each other. Previous works are focus on studying magnetic properties of RFe [...] Read more.

The magnetic interactions of iron-rich manganese-based ThMn₁₂ type rare earth metal intermetallic compounds are extremely complex. The antiferromagnetic structure sublattice and the ferromagnetic structure sublattice had coexisted and competed with each other. Previous works are focus on studying magnetic properties of RFe_xMn_12−x (x = 0–9.0, Δx = 0.2). In this work, we obtained a detailed magnetic phase diagram for iron-rich ErFe_xMn_12−x series alloy samples with a fine composition increment (Δx = 0.2), and studied the exchange bias effect and magneto-caloric effect of samples. ErFe_xMn_12−x series (x = 7.0–9.0, Δx = 0.2) alloy samples were synthesized by arc melting, and the pure ThMn₁₂-type phase structure was confirmed by X-ray diffraction (XRD). The neutron diffraction test was used to confirm the Mn atom preferentially occupying the 8i position and to quantify the Mn. The magnetic properties of the materials were characterized by a comprehensive physical property measurement system (PPMS). Accurate magnetic phase diagrams of the samples in the composition range 7.0–9.0 were obtained. Along with temperature decrease, the samples experienced paramagnetic, ferromagnetic changes for samples with x < 7.4 and x > 8.4, and paramagnetic, antiferromagnetic and ferromagnetic or paramagnetic, ferromagnetic and antiferromagnetic changes for samples with 7.4 ≤ x ≤ 8.2. The tunable exchange bias effect was observed for sample with 7.4 ≤ x ≤ 8.2, which resulting from competing magnetic interacting among ferromagnetic and antiferromagnetic sublattices. The maximum magnetic entropy change in an ErFe_9.0Mn_3.0 specimen reached 1.92 J/kg/K around room temperature when the magnetic field change was 5 T. This study increases our understanding of exchange bias effects and allows us to better control them. Full article

(This article belongs to the Special Issue Advanced Nanomaterials for Electrochemical Energy Conversion and Storage)

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15 pages, 1759 KiB

Open AccessFeature PaperArticle

First Report of the Biosynthesis and Characterization of Silver Nanoparticles Using Scabiosa atropurpurea subsp. maritima Fruit Extracts and Their Antioxidant, Antimicrobial and Cytotoxic Properties

by Badiaa Essghaier, Nourchéne Toukabri, Rihab Dridi, Hédia Hannachi, Inès Limam, Filomena Mottola, Mourad Mokni, Mohamed Faouzi Zid, Lucia Rocco and Mohamed Abdelkarim

Nanomaterials 2022, 12(9), 1585; https://doi.org/10.3390/nano12091585 - 7 May 2022

Cited by 16 | Viewed by 2309

Abstract

Candida and dermatophyte infections are difficult to treat due to increasing antifungal drugs resistance such as fluconazole, as well as the emergence of multi-resistance in clinical bacteria. Here, we first synthesized silver nanoparticles using aqueous fruit extracts from Scabiosa atropurpurea subsp. maritima (L.). [...] Read more.

Candida and dermatophyte infections are difficult to treat due to increasing antifungal drugs resistance such as fluconazole, as well as the emergence of multi-resistance in clinical bacteria. Here, we first synthesized silver nanoparticles using aqueous fruit extracts from Scabiosa atropurpurea subsp. maritima (L.). The characterization of the AgNPs by means of UV, XRD, FTIR, and TEM showed that the AgNPs had a uniform spherical shape with average sizes of 40–50 nm. The biosynthesized AgNPs showed high antioxidant activity when investigated using 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. The AgNPs displayed strong antibacterial potential expressed by the maximum zone inhibition and the lowest MIC and MBC values. The AgNPs revealed a significant antifungal effect against the growth and biofilm of Candida species. In fact, the AgNPs were efficient against Trichophyton rubrum, Trichophyton interdigitale, and Microsporum canis. The antifungal mechanisms of action of the AgNPs seem to be due to the disruption of membrane integrity and a reduction in virulence factors (biofilm and hyphae formation and a reduction in germination). Finally, the silver nanoparticles also showed important cytotoxic activity against the human multiple myeloma U266 cell line and the human breast cancer cell line MDA-MB-231. Therefore, we describe new silver nanoparticles with promising biomedical application in the development of novel antimicrobial and anticancer agents. Full article

(This article belongs to the Special Issue Engineered Nanomaterials for Environmental and Health Applications)

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(A). Change in the color of the silver solution after adding plant extract, from light brown (right) to dark brown (left) and (B). UV–Vis spectrum of synthesized AgNPs (black) and the AgNO3 solution (before adding the plant extract (red)). Full article ">Figure 2
(a) XRD pattern of AgNPs; (b)TEM image of silver nanoparticles. Full article ">Figure 3
AgNPs’ effect on Candida growth after incubation for 48 h at 37 °C, as compared to untreated Candida cells. Error bars represent SE of the mean (n = 3). Means followed by the same letter are not significantly different according to the SNK test. Full article ">Figure 4
(A) Visual observation of dermatophyte growth after 14 days at 28 °C in the absence of AgNPs (AgNPs) and in the presence of AgNPs (+AgNPs). (B) Comparative effect of silver nanoparticles on the dermatophyte morphology of Trichophyton interdigitale (d), Microsporum canis (e), and Trichophyton rubrum (f), as compared to their control cultures (a–c), respectively. Red arrows indicate the morphological change by AgNPs. Full article ">Figure 5
Evaluation of silver nanoparticle-induced cytotoxic effects on U266 and MDA-MB-231 cell lines. The reported values are the means ± SD from three independent experiments. No statistically significant differences between the control (no treatment) and the vehicle were noticed. Full article ">

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Nanomaterials, Volume 12, Issue 9 (May-1 2022) – 229 articles

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