Nanomaterials

4903 KiB

Open AccessArticle

Unidirectional Wave Propagation in Low-Symmetric Colloidal Photonic-Crystal Heterostructures

by Vassilios Yannopapas

Nanomaterials 2015, 5(1), 376-385; https://doi.org/10.3390/nano5010376 - 19 Mar 2015

Cited by 9 | Viewed by 5572

We show theoretically that photonic crystals consisting of colloidal spheres exhibit unidirectional wave propagation and one-way frequency band gaps without breaking time-reversal symmetry via, e.g., the application of an external magnetic field or the use of nonlinear materials. Namely, photonic crystals with low [...] Read more.

We show theoretically that photonic crystals consisting of colloidal spheres exhibit unidirectional wave propagation and one-way frequency band gaps without breaking time-reversal symmetry via, e.g., the application of an external magnetic field or the use of nonlinear materials. Namely, photonic crystals with low symmetry such as the monoclinic crystal type considered here as well as with unit cells formed by the heterostructure of different photonic crystals show significant unidirectional electromagnetic response. In particular, we show that the use of scatterers with low refractive-index contrast favors the formation of unidirectional frequency gaps which is the optimal route for achieving unidirectional wave propagation. Full article

(This article belongs to the Special Issue Nanophotonic Materials)

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Unit cell of 3D PC with one-way photonic band gaps: monoclinic crystal consisting of four non-primitive planes of spheres parallel to the (001) surface at positions (0, 0, 0), (0, 0, a/2), (0, 0, a), and (−0.3a, 0, 3a/2). Full article ">Figure 2
Finite slab of the photonic crystal of <a href="#nanomaterials-05-00376-f002" class="html-fig">Figure 2</a> consisting of eight unit layers. Full article ">Figure 3
Transmittance for s- (a) and p- (c) polarized light incident with k|| = (0.25, 0)π/a on a finite slab of the PC (see <a href="#nanomaterials-05-00376-f002" class="html-fig">Figure 2</a>) consisting of eight unit layers whereas type-A spheres we have considered silica SiO2 (ϵ = 2.1) spheres, as type-B polystyrene (ϵ = 2.6) spheres and as type-C silicon (ϵ = 11.9) (Si) spheres. T+ (T−) is the transmittance for light incident from the left (right) (001) faces of the slab. (b) Frequency band structure of the infinitely periodic PC of <a href="#nanomaterials-05-00376-f001" class="html-fig">Figure 1</a> for k||= (0.25, 0)π/a. Full article ">Figure 4
Transmittance for s- (a) and p- (c) polarized light incident with k|| = (0.25, 0)π/a on a finite slab of the photonic crystal (PC) (see <a href="#nanomaterials-05-00376-f002" class="html-fig">Figure 2</a>) consisting of eight unit layers whereas type-A spheres we have considered silica SiO2 (ϵ = 2.1) spheres, as type-B germanium (ϵ = 16.2) spheres and as type-C silicon (ϵ = 11.9) (Si) spheres. T+ (T−) is the transmittance for light incident from the left (right) (001) faces of the slab; (b) Frequency band structure of the infinitely periodic PC of <a href="#nanomaterials-05-00376-f001" class="html-fig">Figure 1</a> for k|| = (0.25, 0)π/a. Full article ">Figure 5
Transmittance for s- (a) and p- (c) polarized light incident with k|| = (0.25, 0)π/a on a finite slab of the PC of <a href="#nanomaterials-05-00376-f001" class="html-fig">Figure 1</a> consisting of eight unit layers whereas type-A spheres we have considered silica SiO2 (ϵ = 2.1) spheres, as type-B polystyrene (ϵ = 2.6) spheres and as type-C sapphire (ϵ = 3.13) (Si) spheres. T+ (T−) is the transmittance for light incident from the left (right) (001) faces of the slab; (b) Frequency band structure of the infinitely periodic PC of <a href="#nanomaterials-05-00376-f001" class="html-fig">Figure 1</a> for k|| = (0.25, 0)π/a. Full article ">

2640 KiB

Open AccessArticle

On the Mass Fractal Character of Si-Based Structural Networks in Amorphous Polymer Derived Ceramics

by Sabyasachi Sen and Scarlett Widgeon

Nanomaterials 2015, 5(1), 366-375; https://doi.org/10.3390/nano5010366 - 17 Mar 2015

Cited by 12 | Viewed by 5403

Abstract

The intermediate-range packing of SiN_xC_4−x (0 ≤ x ≤ 4) tetrahedra in polysilycarbodiimide and polysilazane-derived amorphous SiCN ceramics is investigated using ²⁹Si spin-lattice relaxation nuclear magnetic resonance (SLR NMR) spectroscopy. The SiCN network in the polysilylcarbodiimide-derived ceramic consists [...] Read more.

The intermediate-range packing of SiN_xC_4−x (0 ≤ x ≤ 4) tetrahedra in polysilycarbodiimide and polysilazane-derived amorphous SiCN ceramics is investigated using ²⁹Si spin-lattice relaxation nuclear magnetic resonance (SLR NMR) spectroscopy. The SiCN network in the polysilylcarbodiimide-derived ceramic consists predominantly of SiN₄ tetrahedra that are characterized by a 3-dimensional spatial distribution signifying compact packing of such units to form amorphous Si₃N₄ clusters. On the other hand, the SiCN network of the polysilazane-derived ceramic is characterized by mixed bonded SiN_xC_4−x tetrahedra that are inefficiently packed with a mass fractal dimension of D_f ~2.5 that is significantly lower than the embedding Euclidean dimension (D = 3). This result unequivocally confirms the hypothesis that the presence of dissimilar atoms, namely, 4-coordinated C and 3-coordinated N, in the nearest neighbor environment of Si along with some exclusion in connectivity between SiC_xN_4−x tetrahedra with widely different N:C ratios and the absence of bonding between C and N result in steric hindrance to an efficient packing of these structural units. It is noted that similar inefficiencies in packing are observed in polymer-derived amorphous SiOC ceramics as well as in proteins and binary hard sphere systems. Full article

(This article belongs to the Special Issue Ceramic Nanocomposites: Design Concepts towards Tailor-Made (Multi)Functionality and Prospective Energy-Related Applications)

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29Si MAS nuclear magnetic resonance (NMR) spectra of GM35 (bottom) and PMVS (top) samples. Spinning sidebands are denoted by asterisks. Structural assignments of the peaks to different Si coordination environments are indicated with arrows. Full article ">Figure 2
Double logarithmic plots of the recovery of 29Si magnetization after saturation, plotted as a function of the delay time for GM35 and PMVS samples. Lines are the linear least-squares fits to the data and represent a power law recovery of magnetization (see text for details) over a time span covering more than three orders of magnitude. The slopes of these lines are reported on the plot. Full article ">Figure 3
Schematic of the structural transformation of a 4-membered ring of SiO4 tetrahedra (right) to a smaller ring of 4 Si atoms (yellow) connected to a central C atom (dark blue) by replacing 2 O atoms (red) in the former with a C atoms, i.e., replacement of a SiO2 units with SiC. The dashed lines denote spheres (circles in two-dimension) circumscribing the 4 Si atoms in each case. The diameter of the 4-membered ring is obtained from zeolite crystal structures containing such rings [<a href="#B28-nanomaterials-05-00366" class="html-bibr">28</a>]. On the other hand, the diameter of the sphere to the left is twice the typical length of Si–C bonds (1.9 Å) in silicon carbide crystal structure. Full article ">Figure 4
A view of SiOC network obtained in a previous reverse-monte-carlo (RMC) simulation study [<a href="#B19-nanomaterials-05-00366" class="html-bibr">19</a>]. Si, O and C atoms are shown in red, green and blue, respectively. Note the inhomogeneous distribution of C atoms implying partial spatial segregation of C containing SiOxC4−x tetrahedra along continuous channel-like regions. Full article ">

2502 KiB

Open AccessArticle

In Situ Self Assembly of Nanocomposites: Competition of Chaotic Advection and Interfacial Effects as Observed by X-Ray Diffreaction

by Dilru R. Ratnaweera, Chaitra Mahesha, David A. Zumbrunnen and Dvora Perahia

Nanomaterials 2015, 5(1), 351-365; https://doi.org/10.3390/nano5010351 - 17 Mar 2015

Cited by 2 | Viewed by 5163

Abstract

The effects of chaotic advection on the in situ assembly of a hierarchal nanocomposite of Poly Amide 6, (nylon 6 or PA6) and platelet shape nanoparticles (NPs) were studied. The assemblies were formed by chaotic advection, where melts of pristine PA6 and a [...] Read more.

The effects of chaotic advection on the in situ assembly of a hierarchal nanocomposite of Poly Amide 6, (nylon 6 or PA6) and platelet shape nanoparticles (NPs) were studied. The assemblies were formed by chaotic advection, where melts of pristine PA6 and a mixture of PA6 with NPs were segregated into discrete layers and extruded into film in a continuous process. The process assembles the nanocomposite into alternating pristine-polymer and oriented NP/polymer layers. The structure of these hierarchal assemblies was probed by X-rays as a processing parameter, N, was varied. This parameter provides a measure of the extent of in situ structuring by chaotic advection. We found that all assemblies are semi-crystalline at room temperature. Increasing N impacts the ratio of α to γ crystalline forms. The effects of the chaotic advection vary with the concentration of the NPs. For nanocomposites with lower NP concentrations the amount of the γ crystalline form increased with N. However, at higher NP concentrations, interfacial effects of the NP play a significant role in determining the structure, where the NPs oriented along the melt flow direction and the polymer chains oriented perpendicular to the NP surfaces. Full article

(This article belongs to the Special Issue Self-Assembled Nanomaterials)

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1794 KiB

Open AccessReview

Hybrids of Nucleic Acids and Carbon Nanotubes for Nanobiotechnology

by Kazuo Umemura

Nanomaterials 2015, 5(1), 321-350; https://doi.org/10.3390/nano5010321 - 12 Mar 2015

Cited by 53 | Viewed by 7829

Abstract

Recent progress in the combination of nucleic acids and carbon nanotubes (CNTs) has been briefly reviewed here. Since discovering the hybridization phenomenon of DNA molecules and CNTs in 2003, a large amount of fundamental and applied research has been carried out. Among thousands [...] Read more.

Recent progress in the combination of nucleic acids and carbon nanotubes (CNTs) has been briefly reviewed here. Since discovering the hybridization phenomenon of DNA molecules and CNTs in 2003, a large amount of fundamental and applied research has been carried out. Among thousands of papers published since 2003, approximately 240 papers focused on biological applications were selected and categorized based on the types of nucleic acids used, but not the types of CNTs. This survey revealed that the hybridization phenomenon is strongly affected by various factors, such as DNA sequences, and for this reason, fundamental studies on the hybridization phenomenon are important. Additionally, many research groups have proposed numerous practical applications, such as nanobiosensors. The goal of this review is to provide perspective on biological applications using hybrids of nucleic acids and CNTs. Full article

(This article belongs to the Special Issue Frontiers in Nucleic Acid Nanotechnology)

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Figure 1
A theoretical model of structure of single-stranded DNA (ssDNA) and single-walled carbon nanotubes (SWNTs) hybrids, proposed by Zheng et al. (10,0) SWNT and poly(T) were assumed for the calculation (Reprinted from reference [<a href="#B1-nanomaterials-05-00321" class="html-bibr">1</a>] with permission). Full article ">Figure 2
Optical absorption spectra of separated SWNTs by selective adsorption of ssDNA, reported by Tu et al. (Reprinted from reference [<a href="#B91-nanomaterials-05-00321" class="html-bibr">91</a>] with permission). Full article ">Figure 3
Differences in photoluminescence (PL) maps due to the pH values of solvents indicated by Kim et al. (Reprinted from reference [<a href="#B89-nanomaterials-05-00321" class="html-bibr">89</a>] with permission). Full article ">Figure 4
A typical force curve during the peeling of a T100 ssDNA molecule away from a SWNT surface, demonstrated by Iliafar et al. (Reprinted from reference [<a href="#B83-nanomaterials-05-00321" class="html-bibr">83</a>] with permission). Full article ">Figure 5
An example of agarose gel electrophoresis of DNA-SWNT hybrids with and without ssDNA-binding (SSB) proteins as performed by Nii et al. (Reprinted from reference [<a href="#B123-nanomaterials-05-00321" class="html-bibr">123</a>] with permission). Full article ">Figure 6
Recent theoretical models of several combinations of ssDNA and SWNTs, proposed by Roxbury et al. (Reprinted from reference [<a href="#B169-nanomaterials-05-00321" class="html-bibr">169</a>] with permission). Full article ">Figure 7
Schematic representations and AFM images of structures fabricated with ssDNA-SWNT hybrids using the DNA origami technique, generated by Mangalum et al. (Reprinted from reference [<a href="#B193-nanomaterials-05-00321" class="html-bibr">193</a>] with permission). Full article ">

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Open AccessArticle

Chemokine-Releasing Nanoparticles for Manipulation of the Lymph Node Microenvironment

by Taissia G. Popova, Allison Teunis, Ruben Magni, Alessandra Luchini, Virginia Espina, Lance A. Liotta and Serguei G. Popov

Nanomaterials 2015, 5(1), 298-320; https://doi.org/10.3390/nano5010298 - 5 Mar 2015

Cited by 12 | Viewed by 7206

Abstract

Chemokines (CKs) secreted by the host cells into surrounding tissue establish concentration gradients directing the migration of leukocytes. We propose an in vivo CK gradient remodeling approach based on sustained release of CKs by the crosslinked poly(N-isopropylacrylamide) hydrogel open meshwork nano-particles (NPs) containing [...] Read more.

Chemokines (CKs) secreted by the host cells into surrounding tissue establish concentration gradients directing the migration of leukocytes. We propose an in vivo CK gradient remodeling approach based on sustained release of CKs by the crosslinked poly(N-isopropylacrylamide) hydrogel open meshwork nano-particles (NPs) containing internal crosslinked dye affinity baits for a reversible CK binding and release. The sustained release is based on a new principle of affinity off-rate tuning. The NPs with Cibacron Blue F3G-A and Reactive Blue-4 baits demonstrated a low-micromolar affinity binding to IL-8, MIP-2, and MCP-1 with a half-life of several hours at 37 °C. The capacity of NPs loaded with IL-8 and MIP-1α to increase neutrophil recruitment to lymph nodes (LNs) was tested in mice after footpad injection. Fluorescently-labeled NPs used as tracers indicated the delivery into the sub-capsular compartment of draining LNs. The animals administered the CK-loaded NPs demonstrated a widening of the sub-capsular space and a strong LN influx of leukocytes, while mice injected with control NPs without CKs or bolus doses of soluble CKs alone showed only a marginal neutrophil response. This technology provides a new means to therapeutically direct or restore immune cell traffic, and can also be employed for simultaneous therapy delivery. Full article

(This article belongs to the Special Issue Nanoparticles in Theranostics)

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1349 KiB

Open AccessArticle

DNA/Ag Nanoparticles as Antibacterial Agents against Gram-Negative Bacteria

by Tomomi Takeshima, Yuya Tada, Norihito Sakaguchi, Fumio Watari and Bunshi Fugetsu

Nanomaterials 2015, 5(1), 284-297; https://doi.org/10.3390/nano5010284 - 3 Mar 2015

Cited by 34 | Viewed by 9488

Abstract

Silver (Ag) nanoparticles were produced using DNA extracted from salmon milt as templates. Particles spherical in shape with an average diameter smaller than 10 nm were obtained. The nanoparticles consisted of Ag as the core with an outermost thin layer of DNA. The [...] Read more.

Silver (Ag) nanoparticles were produced using DNA extracted from salmon milt as templates. Particles spherical in shape with an average diameter smaller than 10 nm were obtained. The nanoparticles consisted of Ag as the core with an outermost thin layer of DNA. The DNA/Ag hybrid nanoparticles were immobilized over the surface of cotton based fabrics and their antibacterial efficiency was evaluated using E. coli as the typical Gram-negative bacteria. The antibacterial experiments were performed according to the Antibacterial Standard of Japanese Association for the Functional Evaluation of Textiles. The fabrics modified with DNA/Ag nanoparticles showed a high enough inhibitory and killing efficiency against E. coli at a concentration of Ag ≥ 10 ppm. Full article

(This article belongs to the Special Issue Frontiers in Nucleic Acid Nanotechnology)

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1192 KiB

Open AccessArticle

DNA-Assisted Solubilization of Carbon Nanotubes and Construction of DNA-MWCNT Cross-Linked Hybrid Hydrogels

by Anatoly Zinchenko, Yosuke Taki, Vladimir G. Sergeyev and Shizuaki Murata

Nanomaterials 2015, 5(1), 270-283; https://doi.org/10.3390/nano5010270 - 3 Mar 2015

Cited by 24 | Viewed by 7319

Abstract

A simple method for preparation of DNA-carbon nanotubes hybrid hydrogel based on a two-step procedure including: (i) solubilization of multi-walled carbon nanotubes (MWCNT) in aqueous solution of DNA, and (ii) chemical cross-linking between solubilized MWCNT via adsorbed DNA and free DNA by ethylene [...] Read more.

A simple method for preparation of DNA-carbon nanotubes hybrid hydrogel based on a two-step procedure including: (i) solubilization of multi-walled carbon nanotubes (MWCNT) in aqueous solution of DNA, and (ii) chemical cross-linking between solubilized MWCNT via adsorbed DNA and free DNA by ethylene glycol diglycidyl ether is reported. We show that there exists a critical concentration of MWCNT below which a homogeneous dispersion of MWCNT in hybrid hydrogel can be achieved, while at higher concentrations of MWCNT the aggregation of MWCNT inside hydrogel occurs. The strengthening effect of carbon nanotube in the process of hydrogel shrinking in solutions with high salt concentration was demonstrated and significant passivation of MWCNT adsorption properties towards low-molecular-weight aromatic binders due to DNA adsorption on MWCNT surface was revealed. Full article

(This article belongs to the Special Issue Frontiers in Nucleic Acid Nanotechnology)

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(A) Photographic images of MWCNT (1 mg) after dispersion in pure water (control) and in solution of 0.33% (w/w) DNA (300 bp) by sonication at 10 W for 2.5 h; (B) UV-Vis absorbance spectra of MWCNT aqueous solutions after dispersion by sonication in water (line 1) and in 0.33% DNA solution (line 2). Full article ">Figure 2
(A,B) Typical transmission electron microscopy images of MWCNT dispersed in solution of DNA. (C) Dynamic light scattering analysis data of MWCNT size dispersed in solution of DNA. (D) Zeta potential analysis data of a charge on MWCNT dispersed in solution of DNA. Full article ">Figure 3
Photographic images of DNA and DNA–MWCNT hybrid hydrogel films prepared at different concentrations of MWCNT in solution (A: 0 mg/L (DNA hydrogel without nanotubes); B: 14 mg/L; C: 28 mg/L; D: 55 mg/L; E: 110 mg/L) after swelling in 1 mM NaCl solution. White arrows on image E indicate the flocks of aggregated nanotubes. Full article ">Figure 4
Relative decrease of DNA and DNA–MWCNT hybrid hydrogel film size in solutions of varied NaCl concentrations. Full article ">Figure 5
Time-dependent uptake of 1-naphtylamine from 7 mL of 20 μM solution by bare MWCNT (A); dispersion of carbon nanotubes in DNA solutions (B); DNA–MWCNT hydrogel (C); and DNA hydrogel (D). The amount of MWCNT in every sample was 1 mg. Full article ">Figure 6
Schematic illustration of DNA–multi-walled carbon nanotubes (MWCNT) hybrid hydrogel preparation procedure. (A) Bundles of carbon nanotubes; (B) Individual nanotubes dispersed in solution due to solubilization by DNA under sonication; and (C) DNA-modified nanotubes cross-linked with an additionally added free DNA (red) using EGDE cross-linking agent at alkaline pH and elevated temperatures. Full article ">

0 pages, 231 KiB

Open AccessRetraction

RETRACTED: Begum et al. Potential Impact of Multi-Walled Carbon Nanotubes Exposure to the Seedling Stage of Selected Plant Species. Nanomaterials 2014, 4, 203–221

by Nanomaterials Editorial Office

Nanomaterials 2015, 5(1), 268-269; https://doi.org/10.3390/nano5010268 - 2 Mar 2015

Viewed by 5618

Abstract

We have become aware that a substantial part of the main text of [1] is copied from multiple other publications. In total, 46% of the main text was taken from publications by the same authors [2,3] and 10% from other papers [4,5]. Because [...] Read more.

We have become aware that a substantial part of the main text of [1] is copied from multiple other publications. In total, 46% of the main text was taken from publications by the same authors [2,3] and 10% from other papers [4,5]. Because of the extent of text taken verbatim from previously published articles, we have made the decision to retract the article. All the authors of [1] have agreed to this decision. This paper is thus declared retracted and shall be marked accordingly for the scientific record.[...] Full article

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Open AccessReview

DNA under Force: Mechanics, Electrostatics, and Hydration

by Jingqiang Li, Sithara S. Wijeratne, Xiangyun Qiu and Ching-Hwa Kiang

Nanomaterials 2015, 5(1), 246-267; https://doi.org/10.3390/nano5010246 - 25 Feb 2015

Cited by 22 | Viewed by 8098

Abstract

Quantifying the basic intra- and inter-molecular forces of DNA has helped us to better understand and further predict the behavior of DNA. Single molecule technique elucidates the mechanics of DNA under applied external forces, sometimes under extreme forces. On the other hand, ensemble [...] Read more.

Quantifying the basic intra- and inter-molecular forces of DNA has helped us to better understand and further predict the behavior of DNA. Single molecule technique elucidates the mechanics of DNA under applied external forces, sometimes under extreme forces. On the other hand, ensemble studies of DNA molecular force allow us to extend our understanding of DNA molecules under other forces such as electrostatic and hydration forces. Using a variety of techniques, we can have a comprehensive understanding of DNA molecular forces, which is crucial in unraveling the complex DNA functions in living cells as well as in designing a system that utilizes the unique properties of DNA in nanotechnology. Full article

(This article belongs to the Special Issue Frontiers in Nucleic Acid Nanotechnology)

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726 KiB

Open AccessReview

New Insights into Understanding Irreversible and Reversible Lithium Storage within SiOC and SiCN Ceramics

by Magdalena Graczyk-Zajac, Lukas Mirko Reinold, Jan Kaspar, Pradeep Vallachira Warriam Sasikumar, Gian-Domenico Soraru and Ralf Riedel

Nanomaterials 2015, 5(1), 233-245; https://doi.org/10.3390/nano5010233 - 24 Feb 2015

Cited by 53 | Viewed by 8174

Abstract

Within this work we define structural properties of the silicon carbonitride (SiCN) and silicon oxycarbide (SiOC) ceramics which determine the reversible and irreversible lithium storage capacities, long cycling stability and define the major differences in the lithium storage in SiCN and SiOC. For [...] Read more.

Within this work we define structural properties of the silicon carbonitride (SiCN) and silicon oxycarbide (SiOC) ceramics which determine the reversible and irreversible lithium storage capacities, long cycling stability and define the major differences in the lithium storage in SiCN and SiOC. For both ceramics, we correlate the first cycle lithiation or delithiation capacity and cycling stability with the amount of SiCN/SiOC matrix or free carbon phase, respectively. The first cycle lithiation and delithiation capacities of SiOC materials do not depend on the amount of free carbon, while for SiCN the capacity increases with the amount of carbon to reach a threshold value at ~50% of carbon phase. Replacing oxygen with nitrogen renders the mixed bond Si-tetrahedra unable to sequester lithium. Lithium is more attracted by oxygen in the SiOC network due to the more ionic character of Si-O bonds. This brings about very high initial lithiation capacities, even at low carbon content. If oxygen is replaced by nitrogen, the ceramic network becomes less attractive for lithium ions due to the more covalent character of Si-N bonds and lower electron density on the nitrogen atom. This explains the significant difference in electrochemical behavior which is observed for carbon-poor SiCN and SiOC materials. Full article

(This article belongs to the Special Issue Ceramic Nanocomposites: Design Concepts towards Tailor-Made (Multi)Functionality and Prospective Energy-Related Applications)

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1056 KiB

Open AccessArticle

Synthesis of Upconversion β-NaYF₄:Nd³⁺/Yb³⁺/Er³⁺ Particles with Enhanced Luminescent Intensity through Control of Morphology and Phase

by Yunfei Shang, Shuwei Hao, Jing Liu, Meiling Tan, Ning Wang, Chunhui Yang and Guanying Chen

Nanomaterials 2015, 5(1), 218-232; https://doi.org/10.3390/nano5010218 - 24 Feb 2015

Cited by 42 | Viewed by 10243

Abstract

Hexagonal NaYF₄:Nd³⁺/Yb³⁺/Er³⁺ microcrystals and nanocrystals with well-defined morphologies and sizes have been synthesized via a hydrothermal route. The rational control of initial reaction conditions can not only result in upconversion (UC) micro and nanocrystals with varying [...] Read more.

Hexagonal NaYF₄:Nd³⁺/Yb³⁺/Er³⁺ microcrystals and nanocrystals with well-defined morphologies and sizes have been synthesized via a hydrothermal route. The rational control of initial reaction conditions can not only result in upconversion (UC) micro and nanocrystals with varying morphologies, but also can produce enhanced and tailored upconversion emissions from the Yb³⁺/Er³⁺ ion pairs sensitized by the Nd³⁺ ions. The increase of reaction time converts the phase of NaYF₄:Nd³⁺/Yb³⁺/Er³⁺ particles from the cubic to the hexagonal structure. The added amount of oleic acid plays a critical role in the shape evolution of the final products due to their preferential attachment to some crystal planes. The adjustment of the molar ratio of F⁻/Ln³⁺ can range the morphologies of the β-NaYF₄:Nd³⁺/Yb³⁺/Er³⁺ microcrystals from spheres to nanorods. When excited by 808 nm infrared laser, β-NaYF₄:Nd³⁺/Yb³⁺/Er³⁺ microplates exhibit a much stronger UC emission intensity than particles with other morphologies. This phase- and morphology-dependent UC emission holds promise for applications in photonic devices and biological studies. Full article

(This article belongs to the Special Issue Current Trends in Up-Converting Nanoparticles)

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2596 KiB

Open AccessArticle

Polymorphic Ring-Shaped Molecular Clusters Made of Shape-Variable Building Blocks

by Keitel Cervantes-Salguero, Shogo Hamada, Shin-ichiro M. Nomura and Satoshi Murata

Nanomaterials 2015, 5(1), 208-217; https://doi.org/10.3390/nano5010208 - 16 Feb 2015

Cited by 7 | Viewed by 7148

Abstract

Self-assembling molecular building blocks able to dynamically change their shapes, is a concept that would offer a route to reconfigurable systems. Although simulation studies predict novel properties useful for applications in diverse fields, such kinds of building blocks, have not been implemented thus [...] Read more.

Self-assembling molecular building blocks able to dynamically change their shapes, is a concept that would offer a route to reconfigurable systems. Although simulation studies predict novel properties useful for applications in diverse fields, such kinds of building blocks, have not been implemented thus far with molecules. Here, we report shape-variable building blocks fabricated by DNA self-assembly. Blocks are movable enough to undergo shape transitions along geometrical ranges. Blocks connect to each other and assemble into polymorphic ring-shaped clusters via the stacking of DNA blunt-ends. Reconfiguration of the polymorphic clusters is achieved by the surface diffusion on mica substrate in response to a monovalent salt concentration. This work could inspire novel reconfigurable self-assembling systems for applications in molecular robotics. Full article

(This article belongs to the Special Issue Frontiers in Nucleic Acid Nanotechnology)

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Shape-variable building block and design with DNA origami. (a) Abstract representation of the block with two bonding arms; (b) 2-mers in cis configuration and assembled polymorphic clusters (from 3-mers up to 6-mers); (c) (left): Origami scaffold (black), flexible area (mustard), contacting edges (red) and blunt-ends with binary codes (sky-blue); (right): Detail of the flexible area showing staples in colour (yellow stars indicate scaffold loops for tuning springs); (d) Origami profile and its correspondent abstract representation for the 60° and 120° configurations. Full article ">Figure 2
Polymorphic clusters made of shape-variable monomers before “reconfiguration protocol” (a–d) and during the “reconfiguration protocol” (e). (a–b) Clusters of M (11,11). First row: cluster representations. Second row: AFM images. 3-mers, 4-mers and 5-mers (a) and open 6-mers (b) at 2 nM concentration. (c–d) Distribution of monomers contributing to the formation of x-mers in open and closed states (c) and ratio open:closed x-mers (d) for M (11,9), M (11,11) and M (11,18). U indicates unclear monomers. (e) Inset of the frames in movie in <a href="#app1-nanomaterials-05-00208" class="html-app">Supplementary Information</a> (0.02 fps). A 3-mers closes and two 2-mers self-assemble into an open 4-mer. AFM images in (a) are 310 nm × 300 nm in size. Error bars in (c) and SE in (d) indicate the standard error. n indicates the number of analysed AFM images of 2040 nm × 1680 nm, and the number of counted monomers per each AFM image is shown in <a href="#app1-nanomaterials-05-00208" class="html-app">Figure S12</a>. Full article ">Figure 3
Self-assemble and reconfiguration of fixed monomers. (a.1) and (b.1): Fixed monomers. (a.2–3) 3-mers and cluster distribution before and after reconfiguration of M (11,0). (b.2–3) Representative AFM images of M (0,11) before and after reconfiguration. (b.4–12) Clusters after reconfiguration for different spring B. White arrows in (b.5) show extra M13. (c): Distribution of monomers contributing to the formation of x-mers including open and closed states (c.1) and ratio open:closed x-mers (c.2) for M (0,11). U indicates unclear monomers. AFM images are 310 nm × 300 nm. Width of (b.9) is 500 nm. Scale bars are 200 nm. Error bars in (a.3, c.1) and SE in (c.2) indicate the standard error. n indicates the number of analysed AFM images of 2040 nm × 1680 nm, and the number of counted monomers per each AFM image is shown in <a href="#app1-nanomaterials-05-00208" class="html-app">Figure S12</a>. Full article ">Figure 4
Distributions of the clusters after reconfiguration for M (0,b) (b = 8−18). (a) Distribution of monomers contributing to the formation of x-mers including open and closed states. Colours indicate each type of cluster. Yellow indicates open 7-mer. Analysed AFM areas are 2240 nm × 1680 nm; (b) Ratio open:closed clusters for 4-mers, 5-mers and 6-mers. Error bars in (a) and SE in (b) indicate the standard error. n indicates the number of analysed AFM images of 2040 nm × 1680 nm, and the number of counted monomers per each AFM image is shown in <a href="#app1-nanomaterials-05-00208" class="html-app">Figure S12</a>. Full article ">

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Open AccessReview

DNA-Protected Silver Clusters for Nanophotonics

by Elisabeth Gwinn, Danielle Schultz, Stacy M. Copp and Steven Swasey

Nanomaterials 2015, 5(1), 180-207; https://doi.org/10.3390/nano5010180 - 12 Feb 2015

Cited by 104 | Viewed by 11782

Abstract

DNA-protected silver clusters (Ag_N-DNA) possess unique fluorescence properties that depend on the specific DNA template that stabilizes the cluster. They exhibit peak emission wavelengths that range across the visible and near-IR spectrum. This wide color palette, combined with low toxicity, high [...] Read more.

DNA-protected silver clusters (Ag_N-DNA) possess unique fluorescence properties that depend on the specific DNA template that stabilizes the cluster. They exhibit peak emission wavelengths that range across the visible and near-IR spectrum. This wide color palette, combined with low toxicity, high fluorescence quantum yields of some clusters, low synthesis costs, small cluster sizes and compatibility with DNA are enabling many applications that employ Ag_N-DNA. Here we review what is known about the underlying composition and structure of Ag_N-DNA, and how these relate to the optical properties of these fascinating, hybrid biomolecule-metal cluster nanomaterials. We place Ag_N-DNA in the general context of ligand-stabilized metal clusters and compare their properties to those of other noble metal clusters stabilized by small molecule ligands. The methods used to isolate pure Ag_N-DNA for analysis of composition and for studies of solution and single-emitter optical properties are discussed. We give a brief overview of structurally sensitive chiroptical studies, both theoretical and experimental, and review experiments on bringing silver clusters of distinct size and color into nanoscale DNA assemblies. Progress towards using DNA scaffolds to assemble multi-cluster arrays is also reviewed. Full article

(This article belongs to the Special Issue Frontiers in Nucleic Acid Nanotechnology)

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1725 KiB

Open AccessArticle

Cysteine-Functionalized Chitosan Magnetic Nano-Based Particles for the Recovery of Light and Heavy Rare Earth Metals: Uptake Kinetics and Sorption Isotherms

by Ahmed A. Galhoum, Mohammad G. Mafhouz, Sayed T. Abdel-Rehem, Nabawia A. Gomaa, Asem A. Atia, Thierry Vincent and Eric Guibal

Nanomaterials 2015, 5(1), 154-179; https://doi.org/10.3390/nano5010154 - 4 Feb 2015

Cited by 108 | Viewed by 8312

Abstract

Cysteine-functionalized chitosan magnetic nano-based particles were synthesized for the sorption of light and heavy rare earth (RE) metal ions (La(III), Nd(III) and Yb(III)). The structural, surface, and magnetic properties of nano-sized sorbent were investigated by elemental analysis, FTIR, XRD, TEM and VSM (vibrating [...] Read more.

Cysteine-functionalized chitosan magnetic nano-based particles were synthesized for the sorption of light and heavy rare earth (RE) metal ions (La(III), Nd(III) and Yb(III)). The structural, surface, and magnetic properties of nano-sized sorbent were investigated by elemental analysis, FTIR, XRD, TEM and VSM (vibrating sample magnetometry). Experimental data show that the pseudo second-order rate equation fits the kinetic profiles well, while sorption isotherms are described by the Langmuir model. Thermodynamic constants (ΔG°, ΔH°) demonstrate the spontaneous and endothermic nature of sorption. Yb(III) (heavy RE) was selectively sorbed while light RE metal ions La(III) and Nd(III) were concentrated/enriched in the solution. Cationic species RE(III) in aqueous solution can be adsorbed by the combination of chelating and anion-exchange mechanisms. The sorbent can be efficiently regenerated using acidified thiourea. Full article

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3293 KiB

Open AccessCommunication

The Nucleotide Capture Region of Alpha Hemolysin: Insights into Nanopore Design for DNA Sequencing from Molecular Dynamics Simulations

by Richard M. A. Manara, Susana Tomasio and Syma Khalid

Nanomaterials 2015, 5(1), 144-153; https://doi.org/10.3390/nano5010144 - 27 Jan 2015

Cited by 8 | Viewed by 8418

Abstract

Nanopore technology for DNA sequencing is constantly being refined and improved. In strand sequencing a single strand of DNA is fed through a nanopore and subsequent fluctuations in the current are measured. A major hurdle is that the DNA is translocated through the [...] Read more.

Nanopore technology for DNA sequencing is constantly being refined and improved. In strand sequencing a single strand of DNA is fed through a nanopore and subsequent fluctuations in the current are measured. A major hurdle is that the DNA is translocated through the pore at a rate that is too fast for the current measurement systems. An alternative approach is “exonuclease sequencing”, in which an exonuclease is attached to the nanopore that is able to process the strand, cleaving off one base at a time. The bases then flow through the nanopore and the current is measured. This method has the advantage of potentially solving the translocation rate problem, as the speed is controlled by the exonuclease. Here we consider the practical details of exonuclease attachment to the protein alpha hemolysin. We employ molecular dynamics simulations to determine the ideal (a) distance from alpha-hemolysin, and (b) the orientation of the monophosphate nucleotides upon release from the exonuclease such that they will enter the protein. Our results indicate an almost linear decrease in the probability of entry into the protein with increasing distance of nucleotide release. The nucleotide orientation is less significant for entry into the protein. Full article

(This article belongs to the Special Issue Frontiers in Nucleic Acid Nanotechnology)

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The alpha-hemolysin (αHL) protein in a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayer, with the mononucleotide positioned above the vestibule entrance, where each mononucleotide represents an individual simulation. The protein is represented by yellow ribbons and for other atoms: Carbon is shown in cyan, oxygen in red, nitrogen in blue, phosphorus in brown and hydrogen in white. The waters and ions are excluded for clarity. (Inset) The phosphate orientations used, termed the “up” and “down” orientations, shown top and bottom respectively. Full article ">Figure 2
Plots showing the relaionship between release loction and probability of capture. The highest possible probability of entry for (a) the distance study and (b) the displacement study, e.g., these are the simulations where either capture or possible capture is observed. The lowest possible probability of entry for (c) the distance study and (d) the displacement study, e.g., these are the simulations where capture is observed. The black lines are for the phosphate up orientation and the red lines are the phosphate down orientation. Error bars were calculated by using the standard error, treating the data as a binomial distribution. Full article ">Figure 3
The residues with the highest propensity to interact with the nucleotide for: failed capture (a) and possible capture (b). The blue highlighted residues corresponding to failed capture are on the edge of the vestibule entrance and on the surface of the vestibule. The red highlighted residues associated with possible capture are predominantly on the edge of the entrance to the vestibule. (Inset) The most frequently observed binding mode between cytosine monophosphate (CMP) and the amino acid triplet, D45, K46 and N47. Hydrogen bonds (dashed lines) are observed between the hydroxyl group of the sugar and the side-chain of D45, as well as the nucleobase and the side-chain of N47. These hydrogen bonds are stable and are present for extended periods of time (greater than 1 ns). Residues are coloured for clarity; D45 in red K46 in blue, and N47 in yellow. Full article ">Figure 4
The probabilities of entry for given release points relative to the ring of K8 residues for (a) the phosphate down orientation and (b) the phosphate up orientation. Simulations performed with the phosphate in the down orientation are closer than the corresponding phosphate up simulations for the same capture probability. Full article ">

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Open AccessReview

Alumina Matrix Composites with Non-Oxide Nanoparticle Addition and Enhanced Functionalities

by Dušan Galusek and Dagmar Galusková

Nanomaterials 2015, 5(1), 115-143; https://doi.org/10.3390/nano5010115 - 27 Jan 2015

Cited by 31 | Viewed by 7720

Abstract

The addition of SiC or TiC nanoparticles to polycrystalline alumina matrix has long been known as an efficient way of improving the mechanical properties of alumina-based ceramics, especially strength, creep, and wear resistance. Recently, new types of nano-additives, such as carbon nanotubes (CNT), [...] Read more.

The addition of SiC or TiC nanoparticles to polycrystalline alumina matrix has long been known as an efficient way of improving the mechanical properties of alumina-based ceramics, especially strength, creep, and wear resistance. Recently, new types of nano-additives, such as carbon nanotubes (CNT), carbon nanofibers (CNF), and graphene sheets have been studied in order not only to improve the mechanical properties, but also to prepare materials with added functionalities, such as thermal and electrical conductivity. This paper provides a concise review of several types of alumina-based nanocomposites, evaluating the efficiency of various preparation methods and additives in terms of their influence on the properties of composites. Full article

(This article belongs to the Special Issue Ceramic Nanocomposites: Design Concepts towards Tailor-Made (Multi)Functionality and Prospective Energy-Related Applications)

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Microstructure refinement observed in Al2O3-SiC nanocomposites with increasing volume fraction of SiC nanoparticles: (a) 3 vol% SiC; (b) 8 vol% SiC. The nanocomposites were sintered without pressure at 1750 °C from a green body prepared by warm pressing of poly(allyl)carbosilane-coated alumina powder [<a href="#B34-nanomaterials-05-00115" class="html-bibr">34</a>]. Full article ">Figure 2
Creep deformation of Al2O3-SiC (AS) nanocomposites measured at 1350 °C and mechanical load of 75, 150, and 200 MPa. The increase of load is reflected as a break at the stress-strain curve. The number in the sample denomination represents the volume fraction of SiC in the material, i.e., AS5c represents the Al2O3-SiC nanocomposite with 5 vol% of SiC [<a href="#B88-nanomaterials-05-00115" class="html-bibr">88</a>]. Full article ">Figure 3
Composition dependence of (a) hardness; (b) fracture toughness; and (c) fracture strength of Al2O3-MWCNT (denoted AC) and Al2O3-ZrO2-MWCNT (denoted AZC) nanocomposites. Comparison to monolithic alumina reference [<a href="#B95-nanomaterials-05-00115" class="html-bibr">95</a>]. Red circles represent the respective properties of nanocomposite with various volume fractions of MWCNT. Black squares represent the same property of the monolithic alumina reference. Full article ">Figure 4
Indication of toughening mechanisms observed in Al2O3-ZrO2-MWCNT nanocomposites [<a href="#B95-nanomaterials-05-00115" class="html-bibr">95</a>]. Full article ">Figure 5
Temperature dependence of thermal conductivity of Al2O3-SiC (AS) nanocomposites with various volume fractions of SiC. Comparison to monolithic alumina reference [<a href="#B126-nanomaterials-05-00115" class="html-bibr">126</a>]. The number in the sample denomination represents the volume fraction of SiC in the material (i.e., AS3c represents the Al2O3-SiC nanocomposite containing 3 vol% SiC). Full article ">Figure 6
Composition dependence of DC electric conductivity of Al2O3-SiC nanocomposites with various volume fractions of SiC. Comparison to monolithic alumina reference [<a href="#B126-nanomaterials-05-00115" class="html-bibr">126</a>]. Full article ">Figure 7
Composition dependence of DC electric conductivity of Al2O3-MWCNT (material AC) and Al2O3-ZrO2-MWCNT (material AZC) nanocomposites [<a href="#B95-nanomaterials-05-00115" class="html-bibr">95</a>]. Full article ">Figure 8
Composition dependence of thermal conductivity of Al2O3-MWCNT (material AC) and Al2O3-ZrO2-MWCNT (material AZC) nanocomposites [<a href="#B95-nanomaterials-05-00115" class="html-bibr">95</a>]. Full article ">

3248 KiB

Open AccessReview

Recent Advances on Carbon Nanotubes and Graphene Reinforced Ceramics Nanocomposites

by Iftikhar Ahmad, Bahareh Yazdani and Yanqiu Zhu

Nanomaterials 2015, 5(1), 90-114; https://doi.org/10.3390/nano5010090 - 20 Jan 2015

Cited by 140 | Viewed by 11653

Abstract

Ceramics suffer the curse of extreme brittleness and demand new design philosophies and novel concepts of manufacturing to overcome such intrinsic drawbacks, in order to take advantage of most of their excellent properties. This has been one of the foremost challenges for ceramic [...] Read more.

Ceramics suffer the curse of extreme brittleness and demand new design philosophies and novel concepts of manufacturing to overcome such intrinsic drawbacks, in order to take advantage of most of their excellent properties. This has been one of the foremost challenges for ceramic material experts. Tailoring the ceramics structures at nanometre level has been a leading research frontier; whilst upgrading via reinforcing ceramic matrices with nanomaterials including the latest carbon nanotubes (CNTs) and graphene has now become an eminent practice for advanced applications. Most recently, several new strategies have indeed improved the properties of the ceramics/CNT nanocomposites, such as by tuning with dopants, new dispersions routes and modified sintering methods. The utilisation of graphene in ceramic nanocomposites, either as a solo reinforcement or as a hybrid with CNTs, is the newest development. This article will summarise the recent advances, key difficulties and potential applications of the ceramics nanocomposites reinforced with CNTs and graphene. Full article

(This article belongs to the Special Issue Ceramic Nanocomposites: Design Concepts towards Tailor-Made (Multi)Functionality and Prospective Energy-Related Applications)

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Statistical analysis of the carbon nanotubes (CNTs)-reinforced ceramic nanocomposites. Full article ">Figure 2
Structural features of (a) Monolithic Al2O3 showing large grains with inter-granular fracture; (b) CNTs/Al2O3 nanocomposites with fine grains; (c) Trans-granular fracture mode in CNTs/Al2O3 nanocomposites; and (d) Single-walled (SW)CNTs at grain boundary of Al2O3 matrix. TEM images exhibiting the CNT–ceramic interactions (e) Multi-walled (MW)CNTs (black arrow) showing their morphology in nanocomposite; (f) A single MWCNT existing at grain boundary; (g) in porosity and (h) Embedded within a single ceramic grain. Adapted from References [<a href="#B32-nanomaterials-05-00090" class="html-bibr">32</a>] and [<a href="#B66-nanomaterials-05-00090" class="html-bibr">66</a>] with permissions. Copyright 2010, Elsevier Ltd. Full article ">Figure 3
(a) TEM image of the pristine MWCNTs; (b) High-magnification TEM image of the acid-treated MWCNT surface, arrow indicates nano-pit; (c) Nano-pit on the acid-treated MWCNTs is filled up with Al2O3 crystal; and (d) Rough surface of MWCNT produced by chemical vapour deposition (CVD) method. Adapted from References [<a href="#B12-nanomaterials-05-00090" class="html-bibr">12</a>] and [<a href="#B32-nanomaterials-05-00090" class="html-bibr">32</a>] with permissions. Copyright 2009, Elsevier Ltd. and 2008 IOP Publishing Ltd. Full article ">Figure 4
(a,b) High-resolution TEM images showing CNT/ceramic interfaces. Adapted from References [<a href="#B15-nanomaterials-05-00090" class="html-bibr">15</a>] and [<a href="#B32-nanomaterials-05-00090" class="html-bibr">32</a>] with permissions. Copyright 2005 Advanced Study Center Co. Ltd. and 2010 Elsevier Ltd. Full article ">Figure 5
SEM images from fractured surface of GNT-Al2O3 nanocomposites with various GNP/CNT ratio, (a and b); Al2O3-(0.5 wt% GNP + 1 wt% CNT), (c–e); Al2O3-(0.5 wt% GNP + 0.5 wt% CNT), (f); Al2O3-0.5 wt% GNP. Adapted from Reference [<a href="#B26-nanomaterials-05-00090" class="html-bibr">26</a>] with permission. Copyright 2014 Elsevier Ltd. Full article ">

309 KiB

Open AccessReview

Magnetic Properties of Magnetic Nanoparticles for Efficient Hyperthermia

by Ihab M. Obaidat, Bashar Issa and Yousef Haik

Nanomaterials 2015, 5(1), 63-89; https://doi.org/10.3390/nano5010063 - 9 Jan 2015

Cited by 382 | Viewed by 16847

Abstract

Localized magnetic hyperthermia using magnetic nanoparticles (MNPs) under the application of small magnetic fields is a promising tool for treating small or deep-seated tumors. For this method to be applicable, the amount of MNPs used should be minimized. Hence, it is essential to [...] Read more.

Localized magnetic hyperthermia using magnetic nanoparticles (MNPs) under the application of small magnetic fields is a promising tool for treating small or deep-seated tumors. For this method to be applicable, the amount of MNPs used should be minimized. Hence, it is essential to enhance the power dissipation or heating efficiency of MNPs. Several factors influence the heating efficiency of MNPs, such as the amplitude and frequency of the applied magnetic field and the structural and magnetic properties of MNPs. We discuss some of the physics principles for effective heating of MNPs focusing on the role of surface anisotropy, interface exchange anisotropy and dipolar interactions. Basic magnetic properties of MNPs such as their superparamagnetic behavior, are briefly reviewed. The influence of temperature on anisotropy and magnetization of MNPs is discussed. Recent development in self-regulated hyperthermia is briefly discussed. Some physical and practical limitations of using MNPs in magnetic hyperthermia are also briefly discussed. Full article

124 KiB

Open AccessEditorial

Acknowledgement to Reviewers of Nanomaterials in 2014

by Nanomaterials Editorial Office

Nanomaterials 2015, 5(1), 61-62; https://doi.org/10.3390/nano5010061 - 7 Jan 2015

Viewed by 3712

Abstract

The editors of Nanomaterials would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2014:[...] Full article

1604 KiB

Open AccessArticle

Cellular Uptake of Tile-Assembled DNA Nanotubes

by Samet Kocabey, Hanna Meinl, Iain S. MacPherson, Valentina Cassinelli, Antonio Manetto, Simon Rothenfusser, Tim Liedl and Felix S. Lichtenegger

Nanomaterials 2015, 5(1), 47-60; https://doi.org/10.3390/nano5010047 - 30 Dec 2014

Cited by 52 | Viewed by 10085

Abstract

DNA-based nanostructures have received great attention as molecular vehicles for cellular delivery of biomolecules and cancer drugs. Here, we report on the cellular uptake of tubule-like DNA tile-assembled nanostructures 27 nm in length and 8 nm in diameter that carry siRNA molecules, folic [...] Read more.

DNA-based nanostructures have received great attention as molecular vehicles for cellular delivery of biomolecules and cancer drugs. Here, we report on the cellular uptake of tubule-like DNA tile-assembled nanostructures 27 nm in length and 8 nm in diameter that carry siRNA molecules, folic acid and fluorescent dyes. In our observations, the DNA structures are delivered to the endosome and do not reach the cytosol of the GFP-expressing HeLa cells that were used in the experiments. Consistent with this observation, no elevated silencing of the GFP gene could be detected. Furthermore, the presence of up to six molecules of folic acid on the carrier surface did not alter the uptake behavior and gene silencing. We further observed several challenges that have to be considered when performing in vitro and in vivo experiments with DNA structures: (i) DNA tile tubes consisting of 42 nt-long oligonucleotides and carrying single- or double-stranded extensions degrade within one hour in cell medium at 37 °C, while the same tubes without extensions are stable for up to eight hours. The degradation is caused mainly by the low concentration of divalent ions in the media. The lifetime in cell medium can be increased drastically by employing DNA tiles that are 84 nt long. (ii) Dyes may get cleaved from the oligonucleotides and then accumulate inside the cell close to the mitochondria, which can lead to misinterpretation of data generated by flow cytometry and fluorescence microscopy. (iii) Single-stranded DNA carrying fluorescent dyes are internalized at similar levels as the DNA tile-assembled tubes used here. Full article

(This article belongs to the Special Issue Frontiers in Nucleic Acid Nanotechnology)

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Characterization of nanotubes. (a) Gel electrophoresis analysis of assembled nanotubes: (1) 1-kb ladder, (2) nanotube, (3) nanotube + folate, (4) nanotube + folate + siRNA, and (5) individual oligonucleotide. Electron micrographs of (b) Nanotubes; (c) Nanotubes with folate; and (d) Nanotubes with folate and siRNA (scale bars: 50 nm; insets: 20 nm). Full article ">Figure 2
Endosomal uptake of nanotubes in HeLa cells. Endosomal staining of nanotubes with dextran. (a) Nanotubes; (b) Dextran; (c) Merged image from (a), (b) and a third channel (DAPI, blue). (d) Flow cytometry analysis of folate-dependent uptake of Atto488-labeled nanotubes over 24 h. Untreated cells act as the control, and the specific fluorescence intensity (SFI) of the dye is depicted. (e) Fluorescence intensity of stably GFP-expressing Hela cells upon the addition of nanotubes carrying GFP-targeting siRNAs or upon transfection of a GFP-targeting siRNA and a non-targeting siRNA, respectively, as controls using lipofection (LF). The median fluorescence intensity (MFI) of GFP is depicted. Full article ">Figure 3
Stability of nanotubes. (a) Stability of nanotubes in PBS with different Mg2+ concentrations; (b) Stability of nanotubes carrying siRNA in PBS with different Mg2+ concentrations; (c) Stability of nanotubes in DMEM medium in the absence or presence of FCS; (d) Stability of nanotubes carrying siRNA in DMEM medium in the absence or presence of FCS (L: 1 kb ladder; C: control. All samples were incubated at 37 °C). Full article ">Figure 4
Stability of nanotubes assembled from 84 nt-long oligonucleotides. (a) Schematic depiction of a section of the 6HT demonstrating the hybridization of 84mers; (b) Schematic depiction of a section of the 6HT demonstrating the hybridization of 42mers; (c) Stability of nanotubes (84mers) in PBS with different Mg2+ concentrations; (d) Stability of nanotubes (84mers and 42mers) in DMEM + 10% FCS, DMEM and PBS. Nanotubes were incubated at 45 °C for 2 h (L: 1 kb ladder; C: control). Full article ">Figure 5
Effect of dye cleavage on cellular uptake. (a) Endosomal staining using Alexa Fluor 488-coupled dextran (shown in green) of HeLa cells treated with oligodeoxynucleotide (ODN)-Atto647 (shown in red); (b) Mitochondrial colocalization of Atto647 (shown in red) in HeLa cells stained with the mitochondrial dye MitoTracker Green (shown in green). Nuclei are stained with Hoechst 33342; (c) Flow cytometry analysis of fluorescence intensity of cells treated with ODN-Atto647 in the absence or presence of FCS; (d) Flow cytometry analysis of fluorescence intensity of cells treated with Atto488-dUTP, ODN-Atto488 and nanotube labeled with Atto488. Untreated cells act as the control, and the specific fluorescence intensity (SFI) of the dye is depicted. Full article ">Figure 6
DNA nanotube assembly. (Left) Click reaction of alkyne-modified oligonucleotides with azide-modified PEGylated folate. (Right) Self-assembly of 24 oligonucleotides into a six-helix tube after a 17-h annealing process. Full article ">

1088 KiB

Open AccessArticle

A Novel Arch-Shape Nanogenerator Based on Piezoelectric and Triboelectric Mechanism for Mechanical Energy Harvesting

by Chenyang Xue, Junyang Li, Qiang Zhang, Zhibo Zhang, Zhenyin Hai, Libo Gao, Ruiting Feng, Jun Tang, Jun Liu, Wendong Zhang and Dong Sun

Nanomaterials 2015, 5(1), 36-46; https://doi.org/10.3390/nano5010036 - 26 Dec 2014

Cited by 49 | Viewed by 10726

Abstract

A simple and cost-effective approach was developed to fabricate piezoelectric and triboelectric nanogenerator (P-TENG) with high electrical output. Additionally, pyramid micro structures fabricated atop a polydimethylsiloxane (PDMS) surface were employed to enhance the device performance. Furthermore, piezoelectric barium titanate (BT) nanoparticles and multiwalled [...] Read more.

A simple and cost-effective approach was developed to fabricate piezoelectric and triboelectric nanogenerator (P-TENG) with high electrical output. Additionally, pyramid micro structures fabricated atop a polydimethylsiloxane (PDMS) surface were employed to enhance the device performance. Furthermore, piezoelectric barium titanate (BT) nanoparticles and multiwalled carbon nanotube (MWCNT) were mixed in the PDMS film during the forming process. Meanwhile, the composition of the film was optimized to achieve output performance, and favorable toughness was achieved after thermal curing. An arch-shape ITO/PET electrode was attached to the upper side of the polarized composite film and an aluminum film was placed under it as the bottom electrode. With periodic external force at 20 Hz, electrical output of this P-TENG, reached a peak voltage of 22 V and current of 9 μA with a peak current density of 1.13 μA/cm², which was six times that of the triboelectric generator without BT and MWCNT nanoparticles. The nanogenerator can be directly used to lighten 28 commercial light-emitting diodes (LEDs) without any energy storage unit or rectification circuit under human footfalls. Full article

(This article belongs to the Special Issue Nanomaterials for Energy and Sustainability Applications)

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Figure 1
Output performance of the arch-shape piezoelectric and triboelectric nanogenerator (P-TENG) with nanostructured polydimethylsiloxane (PDMS) film under external forces at different frequencies. Full article ">Figure 2
(a) Open-circuit voltage of the arch-shaped P-TENG with different N at 20 Hz. (b) Open-circuit voltage of the P-TENG with different compositions based on N = 2:3, including: A. generator based on piezoelectric effect; B. generator based on triboelectric effect; C. Generator based on both the piezoelectric and triboelectric effect; (c) Open-circuit voltage and short-circuit current of the arch-shape nanogenerator with different compositions, when the doping radio was fixed (N = 2:3, V = 9%), including: sample A: flat PDMS film; sample B: PDMS film with only micro pyramid arrays; sample C: PDMS film with micro pyramid arrays, unpolarized barium titanate (BT) nanoparticles and carbon nanotube (CNT); sample D: PDMS with only polarized BT nanoparticles and CNT; sample E: PDMS film with micro pyramid arrays, polarized BT nanoparticles and CNT (P-TENG). Full article ">Figure 3
Working principle of this arch-shape nanogenerator. (a–e) Schematic diagram shows the working principle of the arch-shape P-TENG. Full article ">Figure 4
Applications of the arch-shape P-TENG. (a) Diagram of the P-TENG between two plexiglasses with springs; (b) The output open circuit voltage is about 30 V under footstep. (c,d) When footstep falls on the P-TENG, 28 paralleled commercial LEDs were lightened without using any energy storage device or rectification circuit. Notes: All LEDs are connected in serial. Full article ">Figure 5
(a–d) Schematic view of the structural design and fabrication process flowchart of the P-TENG device (the total size of the P-BM composite films is 2 cm × 4 cm × 0.3 mm). Full article ">Figure 6
Structure characterization of the P-BM composite films. (a) SEM image of the BaTiO3 NPs; (b) TEM image of multiwalled carbon nanotube (MWCNTs) with a diameter of 20 nm and a length of 20 μm; (c) SEM image of the pyramid PDMS thin film with BaTiO3 NPs and MWCNTs; (d) Enlarge photograph of the PDMS thin film tore locally by tweezers; (e) High-magnification SEM image of the patterned PDMS surfaces with pyramids features; (f) The high-magnification SEM image of mixing effect about BaTiO3 NPs and MWCNTs. Full article ">

688 KiB

Open AccessArticle

Synthesis, Characterization, and Mechanism of Formation of Janus-Like Nanoparticles of Tantalum Silicide-Silicon (TaSi₂/Si)

by Andrey V. Nomoev, Sergey P. Bardakhanov, Makoto Schreiber, Dashima Zh. Bazarova, Boris B. Baldanov and Nikolai A. Romanov

Nanomaterials 2015, 5(1), 26-35; https://doi.org/10.3390/nano5010026 - 25 Dec 2014

Cited by 15 | Viewed by 7679

Abstract

Metal-semiconductor Janus-like nanoparticles with the composition tantalum silicide-silicon (TaSi₂/Si) were synthesized for the first time by means of an evaporation method utilizing a high-power electron beam. The composition of the synthesized particles were characterized using high-resolution transmission electron microscopy (HRTEM), X-ray [...] Read more.

Metal-semiconductor Janus-like nanoparticles with the composition tantalum silicide-silicon (TaSi₂/Si) were synthesized for the first time by means of an evaporation method utilizing a high-power electron beam. The composition of the synthesized particles were characterized using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), selective area electron diffraction (SAED), and energy dispersive X-ray fluorescence (EDX) analysis. The system is compared to previously synthesized core-shell type particles in order to show possible differences responsible for the Janus-like structure forming instead of a core-shell architecture. It is proposed that the production of Janus-like as opposed to core-shell or monophase particles occurs due to the ability of Ta and Si to form compounds and the relative content of Ta and Si atoms in the produced vapour. Based on the results, a potential mechanism of formation for the TaSi₂/Si nanoparticles is discussed. Full article

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1361 KiB

Open AccessFeature PaperReview

Rare Earth Ion-Doped Upconversion Nanocrystals: Synthesis and Surface Modification

by Hongjin Chang, Juan Xie, Baozhou Zhao, Botong Liu, Shuilin Xu, Na Ren, Xiaoji Xie, Ling Huang and Wei Huang

Nanomaterials 2015, 5(1), 1-25; https://doi.org/10.3390/nano5010001 - 25 Dec 2014

Cited by 66 | Viewed by 13999

Abstract

The unique luminescent properties exhibited by rare earth ion-doped upconversion nanocrystals (UCNPs), such as long lifetime, narrow emission line, high color purity, and high resistance to photobleaching, have made them widely used in many areas, including but not limited to high-resolution displays, new-generation [...] Read more.

The unique luminescent properties exhibited by rare earth ion-doped upconversion nanocrystals (UCNPs), such as long lifetime, narrow emission line, high color purity, and high resistance to photobleaching, have made them widely used in many areas, including but not limited to high-resolution displays, new-generation information technology, optical communication, bioimaging, and therapy. However, the inherent upconversion luminescent properties of UCNPs are influenced by various parameters, including the size, shape, crystal structure, and chemical composition of the UCNPs, and even the chosen synthesis process and the surfactant molecules used. This review will provide a complete summary on the synthesis methods and the surface modification strategies of UCNPs reported so far. Firstly, we summarize the synthesis methodologies developed in the past decades, such as thermal decomposition, thermal coprecipitation, hydro/solvothermal, sol-gel, combustion, and microwave synthesis. In the second part, five main streams of surface modification strategies for converting hydrophobic UCNPs into hydrophilic ones are elaborated. Finally, we consider the likely directions of the future development and challenges of the synthesis and surface modification, such as the large-scale production and actual applications, stability, and so on, of the UCNPs. Full article

(This article belongs to the Special Issue Current Trends in Up-Converting Nanoparticles)

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