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PubMed Journal Database | Nano letters RSS

16:06 EDT 24th April 2014 | BioPortfolio

The US National Library of Medicine and National Institutes of Health manage PubMed.gov which comprises of more than 21 million records, papers, reports for biomedical literature, including MEDLINE, life science and medical journals, articles, reviews, reports and  books.  BioPortfolio aims to publish relevant information on published papers, clinical trials and news associated with users selected topics.

For example view all recent relevant publications on Epigenetics and associated publications and clincial trials.

Showing PubMed Articles 1–25 of 1,800+ from Nano letters

928743

Self-Assembly of Colloidal Hexagonal Bipyramid- and Bifrustum-shaped ZnS Nanocrystals into Two-Dimensional Superstructures.

We present a combined experimental, theoretical, and simulation study on the self-assembly of colloidal hexagonal bipyramid- and hexagonal bifrustum-shaped ZnS nanocrystals (NCs) into two-dimensional superlattices. The simulated NC superstructures are in good agreement with the experimental ones. This shows that the self-assembly process is primarily driven by minimization of the interfacial free energies and maximization of the packing density. Our study shows that a small truncation of the hexagonal bipyr...

924610

Strain Engineering of Kapitza Resistance in Few-layer Graphene.

We demonstrate through molecular dynamics simulations that the Kapitza resistance in few-layer graphene (FLG) can be controlled by applying mechanical strain. For unstrained FLG, the Kapitza resistance decreases with the increase of thickness, and reaches an asymptotic value of 6×10^-10 m^2K/W at a thickness about 16 nm. Uniaxial cross-plane strain is found to increase the Kapitza resistance in FLG monotonically, when the applied strain varies from compressive to tensile. Moreover, uniaxial strain couples...

924583

Toward a rational design of surface textures promoting endothelialization.

The safe integration of cardiovascular devices requires the sustainable coverage of their luminal surface by endothelial cells (ECs). The engineering of active surface textures has the potential to coordinate cellular adhesion and migration under the action of hemodynamic forces. We define a paradigm to rationally design textures maximizing EC activities as a function of the applied stresses. This is based on harnessing the adhesions established by ECs through fine-tuning of the vertical extend of the under...

915362

Tuning of Spectral and Angular Distribution of Scattering from Single Gold Nanoparticles by Subwavelength Interference Layers.

Localized surface plasmon resonance (LSPR) as the resonant oscillation of conduction electrons in metal nanostructures upon light irradiation is widely used for sensing as well as nanoscale manipulation. The spectral resonance band position can be controlled mainly by nanoparticle composition, size, and geometry and is slightly influenced by the local refractive index of the near-field environment. Here we introduce another approach for tuning, based on interference modulation of the light scattered by the...

915279

Room-Temperature Epitaxial Electrodeposition of Single-Crystalline Germanium Nanowires at the Wafer Scale from an Aqueous Solution.

Direct epitaxial growth of single-crystalline germanium (Ge) nanowires at room temperature has been performed through an electrodeposition process on conductive wafers immersed in an aqueous bath. The crystal growth is based on an electrochemical liquid-liquid-solid (ec-LLS) process involving the electroreduction of dissolved GeO2(aq) in water at isolated liquid gallium (Ga) nanodroplet electrodes resting on single-crystalline Ge or Si supports. Ge nanowires were electrodeposited on the wafer scale (>10 cm(...

915268

Hyperbranched β-Cyclodextrin Polymer as an Effective Multidimensional Binder for Silicon Anodes in Lithium Rechargeable Batteries.

Polymeric binders play an important role in electrochemical performance of high capacity silicon (Si) anodes that usually suffer from severe capacity fading due to unparalleled volume change of Si during cycling. In an effort to find efficient polymeric binders that could mitigate such capacity fading, herein, we introduce polymerized β-cyclodextrin (β-CDp) binder for Si nanoparticle anodes. Unlike one-dimensional binders, hyperbranched network structure of β-CDp presents multidimensional hydrogen bondin...

915238

High Performance Germanium Nanowire based Lithium-ion Battery Anodes Extending over 1000 Cycles Through In-situ Formation of a Continuous Porous Network.

Here we report the formation of high-performance and high-capacity lithium-ion battery anodes from high density germanium nanowire arrays grown directly from the current collector. The anodes retain capacities of ∼ 900 mAh/g after 1100 cycles with excellent rate performance characteristics, even at very high discharge rates of 20-100C. We show by an ex-situ HRTEM and HRSEM study that this performance can be attributed to the complete restructuring of the nanowires that occurs within the first 100 cycles t...

915219

Nano-scale stabilization of sodium oxides: Implications for Na-O2 batteries.

The thermodynamic stability of materials can depend on particle size due to the competition between surface and bulk energy. In this letter, we show that while sodium peroxide (Na2O2) is the stable bulk phase of Na in an oxygen environment at standard conditions, sodium superoxide (NaO2) is considerably more stable at the nanoscale. As a consequence, the superoxide requires a much lower nucleation energy than the peroxide, explaining why it can be observed as the discharge product in some Na-O2 batteries. A...

910579

Quantification of High-Efficiency Trapping of Nanoparticles in a Double Nanohole Optical Tweezer.

We measure the dynamics of 20 nm polystyrene particles in a double nanohole trap to determine the trap stiffness for various laser powers. Both the autocorrelation analysis of Brownian fluctuations and the trapping transient analysis provide a consistent value of ∼0.2 fN/nm stiffness for 2 mW of laser power, which is similar to theoretical calculations for aperture trapping. As expected, the stiffness increases linearly with laser power. This is comparable to the stiffness obtained for conventional optica...

905552

Anatase Ttitania Nanorods as an Intercalation Anode Material for Rechargeable Sodium Batteries.

For the first time, we report the electrochemical activity of anatase TiO2 nanorods in a Na cell. The anatase TiO2 nanorods were synthesized by a hydrothermal method, and their surfaces were coated by carbon to improve the electric conductivity through carbonization of pitch at 700oC for 2 h in Ar flow. The resulting structure does not change before and after the carbon coating, as confirmed by X-ray diffraction (XRD). Transmission electron microscopic images confirm the presence of a carbon coating on the...

901469

Ion-Driven Photoluminescence Modulation of Quasi-Two-Dimensional MoS2 Nanoflakes for Applications in Biological Systems.

Quasi-two-dimensional (quasi-2D) molybdenum disulfide (MoS2) is a photoluminescence (PL) material with unique properties. The recent demonstration of its PL, controlled by the intercalation of positive ions, can lead to many opportunities for employing this quasi-2D material in ion-related biological applications. Here, we present two representative models of biological systems that incorporate the ion-controlled PL of quasi-2D MoS2 nanoflakes. The ion exchange behaviors of these two models are investigated...

901440

Enhanced Magnetotransport in Nanopatterned Manganite Nanowires.

We have combined optical and focused ion beam lithographies to produce large aspect-ratio (length-to-width >300) single-crystal nanowires of La2/3Ca1/3MnO3 that preserve their functional properties. Remarkably, an enhanced magnetoresistance value of 34% in an applied magnetic field of 0.1 T in the narrowest 150 nm nanowire is obtained. The strain release at the edges together with a destabilization of the insulating regions is proposed to account for this behavior. This opens new strategies to implement the...

901406

Effect of the Core/Shell Interface on Auger Recombination Evaluated by Single-Quantum-Dot Spectroscopy.

Previous single-particle spectroscopic studies of colloidal quantum dots have indicated a significant spread in biexciton lifetimes across an ensemble of nominally identical nanocrystals. It has been speculated that in addition to dot-to-dot variation in physical dimensions, this spread is contributed to by variations in the structure of the quantum dot interface, which controls the shape of the confinement potential. Here we directly evaluate the effect of the composition of the core-shell interface on sin...

901371

Hole selective MoOx contact for silicon solar cells.

Using an ultrathin (~15 nm in thickness) molybdenum oxide (MoOx, x

901339

General Working Principles of CH3NH3PbX3 Perovskite Solar Cells.

Organometal halide perovskite-based solar cells have recently realized large conversion efficiency over 15% showing great promise for a new large scale cost-competitive photovoltaic technology. Using impedance spectroscopy measurements we are able to separate the physical parameters of carrier transport and recombination in working devices of the two principal morphologies and compositions of perovskite solar cells, viz. compact thin film of CH3NH3PbI3-xClx and CH3NH3PbI3 infiltrated on nanostructured TiO2....

901304

Layer-dependent Electrocatalysis of MoS2 for Hydrogen Evolution.

The quantitative correlation of the catalytic activity with microscopic structure of heterogeneous catalysts is a major challenge for the field of catalysis science. It requests synergistic capabilities to tailor the structure with atomic scale precision and to control the catalytic reaction to proceed through well-defined pathways. Here we leverage on the controlled growth of MoS2 atomically thin films to demonstrate that the catalytic activity of MoS2 for the hydrogen evolution reaction decreases by a fac...

901275

Theoretical description of the role of halides, silver, and surfactants on the structure of gold nanorods.

Understanding synthesis-structure relationships constitutes a major challenge in the study of Materials Science and Catalysis. In the present paper, we have analyzed the role of different ingredients in the formation of gold nanorods from seeds by means of Density Functional Theory (DFT) calculations, including dispersion contributions. We have focussed on two main parameters: the origin of anisotropy and the appearance of high-index lateral facets. Simulations show that anisotropy arises from the formation...

901236

Ultrafast all-optical graphene modulator.

Graphene is an optical material of unusual characteristics because of its linearly dispersive conduction and valence bands and the strong interband transitions. It allows broadband light-matter interactions with ultrafast responses, and can be readily pasted to surfaces of functional structures for photonic and optoelectronic applications. Recently, graphene-based optical modulators have been demonstrated with electrical tuning of the Fermi level of graphene. Their operation bandwidth, however, was limited...

901169

Single-Nanocrystal Reaction Trajectories Reveal Sharp Co-operative Transitions.

Whereas pathways of chemical reactions involving small molecules are well understood, dynamics of reactions in extended solids remain difficult to elucidate. Frequently, kinetic studies on bulk materials provide a picture averaged over multiple domains or grains, smearing out interesting dynamics such as critical nucleation phenomena or sharp phase transitions occurring within individual, often nanoscale grains or domains. By optically monitoring a solid-state reaction with single nanocrystal resolution, we...

901144

Single-Particle Fluorescence Intensity Fluctuations of Carbon Nanodots.

Fluorescent carbon nanodots (CNDs) were synthesized in oxidized and reduced forms and were analyzed at the single-particle level. Images of single CNDs at different excitation energies revealed significant heterogeneity in the lower energy trap sites between particles. We observed that a high percentage of reduced CND particles transitioned between multiple fluorescence intensity levels indicative of multichromophoric systems. Despite this behavior, individual CNDs exhibit single-step photobleaching and tra...

901115

Correlation of Microphotoluminescence Spectroscopy, Scanning Transmission Electron Microscopy, and Atom Probe Tomography on a Single Nano-object Containing an InGaN/GaN Multiquantum Well System.

A single nanoscale object containing a set of InGaN/GaN nonpolar multiple-quantum wells has been analyzed by microphotoluminescence spectroscopy (μPL), high-resolution scanning transmission electron microscopy (HR-STEM) and atom probe tomography (APT). The correlated measurements constitute a rich and coherent set of data supporting the interpretation that the observed μPL narrow emission lines, polarized perpendicularly to the crystal c-axis and with energies in the interval 2.9-3.3 eV, are related to ex...

898211

Selective Trapping or Rotation of Isotropic Dielectric Micro-Particles by Optical Near Field in a Plasmonic Archimedes Spiral.

We demonstrate selective trapping or rotation of optically isotropic dielectric micro-particles by plasmonic near field in a single gold plasmonic Archimedes spiral. Depending on the handedness of circularly polarized excitation, plasmonic near fields can be selectively engineered into either a super-focusing spot for particle trapping or a plasmonic vortex for particle rotation. Our design provides a simple solution for sub-wavelength optical manipulation and may find applications in micromechanical and mi...

898179

Liquid and back gate coupling effect: towards biosensing with lowest detection limit.

We employ noise spectroscopy and transconductance measurements to establish the optimal regimes of operation for our fabricated silicon nanowire field-effect transistors (Si NW FETs) sensors. A strong coupling between the liquid gate and back gate (the substrate) has been revealed and used for optimisation of signal-to-noise ratio in sub-threshold as well as above-threshold regimes. Increasing the sensitivity of Si NW FET sensors above the detection limit has been predicted and proven by direct experimental...

898160

4D Imaging and Diffraction Dynamics of Single-Particle Phase Transition in Heterogeneous Ensembles.

In this Letter, we introduce conical-scanning dark-field imaging in fourdimensional (4D) ultrafast electron microscopy to visualize single-particle dynamics of a polycrystalline ensemble undergoing phase transitions. Specifically, the ultrafast metalinsulator phase transition of vanadium dioxide is induced using laser excitation and followed by taking electron-pulsed, time-resolved images and diffraction patterns. The single-particle selectivity is achieved by identifying the origin of all constituent Bragg...

898133

Photoresponse of an Electrically Tunable Ambipolar Graphene Infrared Thermocouple.

We explore the photoresponse of an ambipolar graphene infrared thermocouple at photon energies close to or below monolayer graphene's optical phonon energy and electrostatically accessible Fermi energy levels. The ambipolar graphene infrared thermocouple consists of monolayer graphene supported by an infrared absorbing material, controlled by two independent electrostatic gates embedded below the absorber. Using a scanning infrared laser microscope, we characterize these devices as a function of carrier typ...


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