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PubMed Journal Database | Nano letters RSS

09:44 EDT 24th May 2016 | 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 2,900+ from Nano letters

Threshold for Terahertz Resonance of Nanoparticles in Water.

Nanoparticle vibrations are coupled to light through electrostriction, which gives nonlinear optical scattering. We investigated the acoustic response of 2 nm gold nanoparticles using nearly-degenerate four-wave mixing experimental configuration and show that the nonlinear response suddenly turns on at low powers (

A Chemical Approach to Break the Planar Configuration Of Ag Nanocubes into Tunable Two-dimensional Metasurfaces.

Current plasmonic metasurfaces of nanocubes are limited to planar configurations, restricting the ability to create tailored local electromagnetic fields. Here, we report a new chemical strategy to achieve tunable metasurfaces with non-planar nanocube orientations, creating novel lattice-dependent field localization patterns. We manipulate the interfacial behaviors of Ag nanocubes by controlling the ratio of hydrophilic/hydrophobic molecules added in a binary thiol mixture during the surface functionalizati...

Unraveling the Mechanism of Nanoscale Mechanical Reinforcement in Glassy Polymer Nanocomposites.

The mechanical reinforcement of polymer nanocomposites (PNCs) above the glass transition temperature, Tg, has been extensively studied. However, not much is known about the origin of this effect below Tg. In this Letter, we unravel the mechanism of PNC reinforcement within the glassy state by directly probing nanoscale mechanical properties with atomic force microscopy and macroscopic properties with Brillouin light scattering. Our results unambiguously show that the 'glassy' Young's modulus in the interfac...

Thermodynamic Self-limiting Growth of Heteroepitaxial Islands induced by Nonlinear Elastic Effect.

We investigate nonlinear elastic effect (NLEF) on the growth of heteroepitaxial islands, a topic of both scientific and technological significance for their applications as quantum dots. We show that the NLEF induces a thermodynamic self-limiting growth mechanism that hinders the strain relaxation of coherent island beyond a maximum size, in contrast to indefinite strain relaxation with increasing island size in the linear elastic regime. This self-limiting growth effect shows a strong dependence on the isl...

High Light Absorption and Charge Separation Efficiency at Low Applied Voltage from Sb-doped SnO2/BiVO4 Core/Shell Nanorod-Array Photoanodes.

BiVO4 has become the top-performing semiconductor among photoanodes for photoelectrochemical water oxidation. However, BiVO4 photoanodes are still limited to a fraction of the theoretically-possible photocurrent at low applied voltages because of modest charge transport properties and a trade-off between light absorption and charge separation efficiencies. Here, we investigate photoanodes composed of thin layers of BiVO4 coated onto Sb-doped SnO2 (Sb:SnO2) nanorod-arrays (Sb:SnO2/BiVO4 NRAs) and demonstrate...

Ratiometric tension probes for mapping receptor forces and clustering at intermembrane junctions.

Short-range communication between cells is required for the survival of multicellular organisms. One mechanism of chemical signaling between adjacent cells employs surface displayed ligands and receptors that only bind when two cells make physical contact. Ligand-receptor complexes that form at the cell-cell junction and physically bridge two cells likely experience mechanical forces. A fundamental challenge in this area pertains to mapping the mechanical forces experienced by ligand-receptor complexes with...

Porous Au-Ag Nanospheres with High-Density and Highly Accessible Hotspots for SERS Analysis.

Colloidal plasmonic metal nanoparticles have enabled surface-enhanced Raman scattering (SERS) for a variety of analytical applications. While great efforts have been made to create hotspots for amplifying Raman signals, it remains a great challenge to ensure their high density and accessibility for improved sensitivity of the analysis. Here we report a dealloying process for the fabrication of porous Au-Ag alloy nanoparticles containing abundant inherent hotspots, which were encased in ultrathin hollow sili...

Direct Mapping of Charge Distribution during Lithiation of Ge Nanowires Using Off-axis Electron Holography.

The successful operation of rechargeable batteries relies on reliable insertion/extraction of ions into/from the electrodes. The battery performance and the response of the electrodes to such ion insertion and extraction are directly related to the spatial distribution of the charge and its dynamic evolution. However, it remains unclear how charge is distributed in the electrodes during normal battery operation. In this work, we have used off-axis electron holography to measure charge distribution during li...

Magnetic properties of restacked 2D spin 1/2 honeycomb RuCl3 nanosheets.

Spin 1/2 honeycomb materials have gained substantial interest due to their exotic magnetism and possible application in quantum computing. However, in all current materials out-of-plane interactions are interfering with the in-plane order, hence a true 2D magnetic honeycomb system is still of demand. Here, we report the exfoliation of the magnetic semiconductor α-RuCl3 into the first halide monolayers and the magnetic characterization of the spin 1/2 honeycomb arrangement of turbostratically stacked RuCl3 ...

Co-existing honeycomb and Kagome characteristics in the electronic band structure of molecular graphene.

We uncover the electronic structure of molecular graphene produced by adsorbed CO molecules on a copper (111) surface by means of first-principles calculations. Our results show that the band structure is fundamentally different from that of conventional graphene, and the unique features of the electronic states arise from co-existing honeycomb and Kagome symmetries. Furthermore, the Dirac cone does not appear at the K-point but at the Gamma-point in the reciprocal space and is accompanied by a third, almos...

Nucleation, growth and bundling of GaN nanowires in molecular beam epitaxy: Disentangling the origin of nanowire coalescence.

We investigate the nucleation, growth and coalescence of spontaneously formed GaN nanowires in molecular beam epitaxy combining the statistical analysis of scanning electron micrographs with Monte Carlo growth models. We find that (i) the nanowire density is limited by the shadowing of the substrate from the impinging fluxes by already existing nanowires, (ii) shortly after the nucleation stage, nanowire radial growth becomes negligible, and (iii) coalescence is caused by bundling of nanowires. The latter p...

Rhombohedral multilayer graphene: a magneto-Raman scattering study.

Graphene layers are known to stack in two stable configurations, namely ABA or ABC stacking, with drastically distinct electronic properties. Unlike the ABA stacking, little has been done to experimentally investigate the electronic properties of ABC graphene multilayers. Here, we report on the first magneto optical study of a large ABC domain in a graphene multilayer flake, with ABC sequences exceeding 17 graphene sheets. ABC-stacked multilayers can be fingerprinted with a characteristic electronic Raman s...

The Plasmonic Pixel: large area, wide gamut color reproduction using aluminum nanostructures.

We demonstrate a new plasmonic pixel (PP) design that produces a full-color optical response over macroscopic dimensions. The pixel design employs arrays of aluminum nanorods 'floating' above their Babinet complementary screen, Concepts from conventional CMYK printing techniques and RGB digital displays are integrated with nanophotonic design principles and adapted to the production of PP elements. The fundamental PP color blocks of CMYK are implemented via a composite plasmonic nano-antenna/slot design, an...

Imaging of anomalous internal reflections of hyperbolic phonon-polaritons in hexagonal boron nitride.

We use scanning near-field optical microscopy to study the response of hexagonal boron nitride nanocones at infrared frequencies, where this material behaves as a hyperbolic medium. The obtained images are dominated by a series of "hot" rings that occur on the sloped sidewalls of the nanocones. The ring positions depend on the incident laser frequency and the nanocone shape. Both dependences are consistent with directional propagation of hyperbolic phonon-polariton rays that are launched at the edges and zi...

Room-temperature Chemical Welding and Sintering of Metallic Nanostructures by Capillary Condensation.

Room-temperature welding and sintering of metal nanostructures, nanoparticles and nanowires, by capillary condensation of chemical vapors have successfully been demonstrated. Nanoscale gaps or capillaries that are abundant in layers of metal nanostructures have been found to be the preferred sites for the condensation of chemically oxidizing vapor, H2O2 in this work. The partial dissolution and re-solidification at such nano-gaps completes the welding/sintering of metal nanostructures within ~10min. at room...

Ultrahigh Tensile Strength Nanowires with a Ni/Ni-Au Multilayer Nanocrystalline Structure.

Superior mechanical properties of nanolayered structures have attracted great interest recently. However, previously fabricated multilayer metallic nanostructures have high strength under compressive load but never reached such high strength under tensile loads. Here, we report that our microalloying-based electrodeposition method creates a strong and stable Ni/Ni-Au multilayer nanocrystalline structure by incorporating Au atoms that makes nickel nanowires (NWs) strongest ever under tensile loads even with ...

Magnetic Hysteresis in Er trimers on Cu(111).

We report magnetic hysteresis in Er clusters on Cu(111) starting from the size of three atoms. Combining x-ray magnetic circular dichroism, scanning tunneling microscopy, and mean-field nucleation theory, we determine the size-dependent magnetic properties of the Er clusters. Er atoms and dimers are paramagnetic and their easy magnetization axes are oriented in-plane. In contrast, trimers and bigger clusters exhibit magnetic hysteresis at 2.5 K with a relaxation time of 2 minutes at 0.1 T and out-of-plane e...

Hydrogenation of Penta-Graphene Leads to Unexpected Large Improvement in Thermal Conductivity.

Penta-graphene (PG) has been identified as a novel 2D material with an intrinsic bandgap, which makes it especially promising for electronics applications. In this work, we use first-principles lattice dynamics and iterative solution of the phonon Boltzmann transport equation (BTE) to determine the thermal conductivity of PG and its more stable derivative - hydrogenated penta-graphene (HPG). As a comparison, we also studied the effect of hydrogenation on graphene thermal conductivity. In contrast to hydroge...

Oxidation Induced Doping of Nanoparticles Revealed by In Situ X-Ray Adsorption Studies.

Doping is a well-known approach to modulate the electronic and optical properties of nanoparticles (NPs). However, doping at nanoscale is still very challenging and the reasons for that are not well understood. We studied the formation and doping process of iron and iron oxide NPs in real time by in situ synchrotron X-ray absorption spectroscopy. Our study revealed that the mass flow of the iron triggered by oxidation is responsible for the internalization of the dopant (molybdenum) adsorbed at the surface ...

Bacteria-mediated hypoxia-specific delivery of nanoparticles for tumors imaging and therapy.

Hypoxia region in solid tumor has been recognized as a complex microenvironment revealing very low oxygen concentration and deficient nutrients. The hypoxic environment reduces the susceptibility of the cancer cells to anticancer drugs, low response of free radicals, and less proliferation of cancer cells in the center of the solid tumors. However, the reduced oxygen surroundings provide an appreciable habitat for anaerobic bacteria to colonize. Here, we present the bacteria-mediated targeting hypoxia to of...

Reduced Graphene Oxide Films with Ultra-High Conductivity as Li-ion Battery Current Collectors.

Solution processed, highly conductive films are extremely attractive for a range of electronic devices, especially for printed macroelectronics. For example, replacing heavy, metal-based current collectors with thin, light, flexible, and highly conductive films will further improve the energy density of such devices. Films with two-dimensional building blocks, such as graphene or reduced graphene oxide (RGO) nanosheets, are particularly promising due to their low percolation threshold with a high aspect rat...

Superabsorbing, artificial metal films constructed from Semiconductor Nanoantennas.

In 1934 Wilhem Woltersdorff demonstrated that the absorption of light in an ultrathin, freestanding film is fundamentally limited to 50%. He concluded that reaching this limit would require a film with a real-valued sheet resistance that is exactly equal to 188.5 Ohm/sq, where is the impedance of free space. This condition can be closely approximated over a wide frequency range in metals that feature a large imaginary relative permittivity, i.e. a real-valued conductivity. A thin, continuous sheet of semico...

Stretchable Superhydrophobicity from Monolithic, Three-Dimensional Hierarchical Wrinkles.

We report the design of three-dimensional (3D) hierarchical wrinkle substrates that can maintain their superhydrophobicity even after being repeatedly stretched. Monolithic poly(dimethysiloxane) with multiscale features showed wetting properties characteristic of static superhydrophobicity with water contact angles (>160°) and very low contact angle hysteresis (

Nanoscale control of Morphology in Fullerene-Based Electron Conducting Buffers via Organic Vapor Phase Deposition.

Small molecular weight organic thin film mixtures of the electron-conducting C60 in a wide energy gap insulating matrix, 3,5,3',5'-tetra(m-pyrid-3-yl)phenyl[1,1']biphenyl (BP4mPy) forms a high efficiency electron filtering buffer in organic photovoltaics (OPV). Electrons are conducted via percolating paths in C60 whereas excitons are blocked by BP4mPy. We find that the conductivity and exciton blocking efficiency of the blends is strongly dependent on film morphology that can be precisely controlled by the ...

Gap States at Low-Angle Grain Boundaries in Monolayer Tungsten Diselenide.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have revealed many novel properties of interest to future device applications. In particular, the presence of grain boundaries (GBs) can significantly influence the material properties of 2D TMDs. However, direct characterization of the electronic properties of the GB defects at the atomic scale remains extremely challenging. In this study, we employ scanning tunnelling microscopy and spectroscopy to investigate the atomic and electronic structure...


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