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04:01 EDT 1st April 2015 | BioPortfolio

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Showing PubMed Articles 1–25 of 2,300+ from Nano letters


Long-range versus short-range scattering in doped epitaxial graphene.

Tuning the electronic properties of graphene by adatom deposition unavoidably introduces disorder into the system, which directly affects the single-particle excitations and electrodynamics. Using angle-resolved photoemission spectroscopy (ARPES) we trace the evolution of disorder in graphene by thallium adatom deposition, and probe its effect on the electronic structure. We show that the signatures of quasiparticle scattering in the photoemission spectral function can be used to identify thallium adatoms -...


Room Temperature Quantum Spin Hall Insulators with a Buckled Square Lattice.

Two-dimensional (2D) topological insulators (TIs), also known as quantum spin Hall (QSH) insulators, are excellent candidates for coherent spin transport related applications because the edge states of 2D TIs are robust against nonmagnetic impurities since the only available backscattering channel is forbidden. Currently, most known 2D TIs are based on a hexagonal (specifically, honeycomb) lattice. Here, we propose that there exists the quantum spin Hall effect (QSHE) in a buckled square lattice. Through pe...


Polymer Nanofiber-Guided Uniform Lithium Deposition for Battery Electrodes.

Lithium metal is one of the most promising candidates as an anode material for next-generation energy storage systems, due to its highest specific capacity (3860 mAh/g) and lowest redox potential of all. The uncontrolled lithium dendrite growth which causes a poor cycling performance and serious safety hazards, however, presents a significant challenge for the realization of lithium metal-based batteries. Here, we demonstrate a novel electrode design by placing a 3-dimensional (3D) oxidized polyacrylonitril...


Polarity-Driven Quasi-3-Fold Composition Symmetry of Self-Catalyzed III-V-V Ternary Core-Shell Nanowires.

A quasi-3-fold composition symmetry has for the first time been observed in self-catalyzed III-V-V core-shell nanowires. In GaAsP nanowires, phosphorus-rich sheets on radial {110} planes, originating at the corners of the hexagonal core were observed. In a cross section, they appear as six radial P-rich bands that originate at the six outer corners of the hexagonal core, with three of them higher in P content along A direction and others along B, forming a quasi-3-fold composition symmetry. We propose that ...

Monday 17th September 1201

An Atomically Layered InSe Avalanche Photodetector.

Atomically thin photodetectors based on 2D materials have attracted great interest due to their potential as highly energy-efficient integrated devices. However, photoinduced carrier generation in these media is relatively poor due to low optical absorption, limiting device performance. Current methods for overcoming this problem, such as reducing contact resistances or back gating, tend to increase dark current and suffer slow response times. Here we realize the avalanche effect in a 2D material-based phot...

Wednesday 20th June 1201

Probing the interactions of intrinsically disordered proteins using nanoparticle tags.

The structural plasticity of intrinsically disordered proteins serves as a rich area for scientific inquiry. Such proteins lack a fix 3D structure but can interact with multiple partners through numerous weak bonds. Nevertheless, this intrinsic plasticity possesses a challenging hurdle in their characterization. We underpin the intermolecular interactions between intrinsically disordered neurofilaments, in various hydrated conditions, using grafted gold nanoparticle (NP) tags. Beyond its biological signific...


Mesoscale Nanoparticles Selectively Target the Renal Proximal Tubule Epithelium.

We synthesized "mesoscale" nanoparticles, approximately 400 nm in diameter, which unexpectedly localized selectively in renal proximal tubules and up to 7 times more efficiently in the kidney than other organs. Although nanoparticles typically localize in the liver and spleen, modulating their size and opsonization potential allowed for stable targeting of the kidneys through a new proposed uptake mechanism. Applying this kidney targeting strategy, we anticipate use in the treatment of renal disease and the...


Multifunctional Graphene Optoelectronic Devices Capable of Detecting and Storing Photonic Signals.

The advantages of graphene photodetectors were utilized to design a new multifunctional graphene optoelectronic device. Organic semiconductors, gold nanoparticles (AuNPs), and graphene were combined to fabricate a photodetecting device with a nonvolatile memory function for storing photonic signals. A pentacene organic semiconductor acted as a light absorption layer in the device and provided a high hole photocurrent to the graphene channel. The AuNPs, positioned between the tunneling and blocking dielectri...

Tuesday 3rd October 1200

High Efficiency Solar-to-Hydrogen Conversion on a Monolithically Integrated InGaN/GaN/Si Adaptive Tunnel Junction Photocathode.

H2 generation under sunlight offers great potential for a sustainable fuel production system. To achieve high efficiency solar-to-hydrogen (STH) conversion, multi-junction photoelectrodes have been commonly employed to absorb a large portion of the solar spectrum and to provide energetic charge carriers for water splitting However, the design and performance of such tandem devices has been fundamentally limited by the current matching between various absorbing layers. Here, by exploiting the lateral carrier...

Saturday 10th June 1200

Improving the capacity of sodium ion battery using virus-templated nano-structured composite cathode.

In this work we investigated an energy-efficient bio-templated route to synthesize nano-structured FePO4 for sodium-based batteries. Self-assembled M13 viruses and single wall carbon nanotubes (SWCNTs) have been used as a template to grow amorphous FePO4 nanoparticles at room temperature (the active composite is denoted as Bio-FePO4-CNT) to enhance the electronic conductivity of the active material. Preliminary tests demonstrate a discharge capacity as high as 166 mAh/g at C/10 rate, corresponding to compos...


Continuous germanene layer on Al(111).

Germanene, a 2D honeycomb structure similar to silicene, has been fabricated on Al(111). The 2D germanene layer covers uniformly the substrate with a large coherence over the Al(111) surface atomic plane. It is characterized by a (3x3) superstructure with respect to the substrate lattice, shown by low energy electron diffraction and scanning tunnelling microscopy. First principles calculations indicate that the Ge atoms accommodate in a very regular atomic configuration with a buckled conformation.


Highly Efficient Electron Transport Obtained by Doping PCBM with Graphdiyne in Planar-Heterojunction Perovskite Solar Cells.

Organic-inorganic perovskite solar cells have recently emerged at the forefront of photovoltaics research. Here, for the first time, graphdiyne (GD), a novel two dimension carbon material, is doped into PCBM layer of perovskite solar cell with an inverted structure (ITO/PEDOT:PSS/CH3NH3PbI3-xClx/PCBM:GD/C60/Al) to improve the electron transport. The optimized PCE of 14.8% was achieved. And an average PCE of PCBM:GD based devices was observed with 28.7% enhancement (13.9% vs 10.8%) compared to that of pure P...


Indirect-to-direct band-gap crossover in few-layer MoTe2.

We study the evolution of the band-gap structure in few-layer MoTe2 crystals, by means of low-temperature micro-reflectance (MR) and temperature-dependent photoluminescence (PL) measurements. The analysis of the measurements indicate that -in complete analogy with other semiconducting transition metal dichalchogenides (TMDs)- the dominant PL emission peaks originate from direct transitions associated to recombination of excitons and trions. When we follow the evolution of the PL intensity as a function of l...


Enhanced Ferroelectric-Nanocrystal Based Hybrid Photocatalysis by Ultrasonic Wave Generated Piezo-phototronic Effect.

Electric field built inside a crystal was proposed to enhance photo-induced carrier separation for improving photocatalytic property of semiconductor photocatalysts. However, a static built-in electric field can easily be saturated by the free carriers due to electrostatic screening, and the enhancement of photocatalysis is thus halt. To overcome this problem, here we propose sono-photocatalysis based on a new hybrid photocatalyst, which combines ferroelectric nanocrystals (BaTiO3) and semiconductor nanopar...


Atomically Thin Epitaxial Template for Organic Crystal Growth Using Graphene with Controlled Surface Wettability.

A two-dimensional epitaxial growth template for organic semiconductors was developed using a new method for transferring clean graphene sheets onto a substrate with controlled surface wettability. The introduction of a sacrificial graphene layer between a patterned polymeric supporting layer and a monolayer graphene sheet enabled the crack-free and residue-free transfer of free-standing monolayer graphene onto arbitrary substrates. The clean graphene template clearly induced the quasi-epitaxial growth of cr...


Exciton Radiative Lifetimes in Layered Transition Metal Dichalcogenides.

Light emission in two-dimensional (2D) transition metal dichalcogenides (TMDs) changes significantly with number of layers and stacking sequence. While the electronic structure and optical absorption are well understood in 2D-TMDs, much less is known about exciton dynamics and radiative recombination. Here, we show first principles calculations of intrinsic exciton radiative lifetimes at low temperature (4 K) and room temperature (300 K) in TMD monolayers with chemical formula MX2 (M=Mo,W and X=S,Se), in bi...


Creating Optical Near-Field Orbital Angular Momentum in a Gold Metasurface.

Nanocavities inscribed in a gold thin film is optimized and designed to form a metasurface. We demonstrate both numerically and experimentally the creation of surface plasmon (SP) vortex carrying orbital angular momentum in the metasurface under linearly polarized optical excitation that carries no optical angular momentum. Moreover, depending on the orientation of the exciting linearly polarized light, we show that the metasurface is capable of providing dynamic switching between SP vortex formation or SP ...


Coupling localized plasmonic and photonic modes tailors and boosts ultrafast light modulation by gold nanoparticles.

Plasmonic nanoparticles offer a broad range of functionalities, owing to their ability to amplify light in the near-field or convert it into heat. However, their ultrafast nonlinear optical response remains too low to envisage all-optical high-rate photonic processing applications. Here, we tackle this challenge by coupling the localized plasmon mode in gold nanoparticles with a localized photonic mode in a 1D resonant cavity. Despite the non-radiative losses, we demonstrate that a strong, reversible and ul...

Sunday 14th November 1198

Single-molecule super-resolution microscopy reveals how light couples to a plasmonic nano-antenna on the nanometer scale.

The greatly enhanced fields near metal nanoparticles have demonstrated remarkable optical properties and are promising for applications from solar energy to bio-sensing. However, direct experimental study of these light-matter interactions at the nanoscale has remained difficult due to the limitations of optical microscopy. Here, we use single-molecule fluorescence imaging to probe how a plasmonic nano-antenna modifies the fluorescence emission from a dipole. We show that the apparent fluorophore emission p...


Temperature and Magnetic-Field Dependence of Radiative Decay in Colloidal Germanium Quantum Dots.

We conduct spectroscopic and theoretical studies of photoluminescence (PL) from Ge quantum dots (QDs) fabricated via colloidal synthesis. The dynamics of late-time PL exhibit a pronounced dependence on temperature and applied magnetic field, which can be explained by radiative decay involving two closely spaced, slowly emitting exciton states. In 3.5 nm QDs, these states are separated by ~1 meV and are characterized by ~82 μs and ~18 μs lifetimes. Using a four-band formalism, we calculate the fine structu...

Friday 29th August 1196

Pathway to the PiezoElectronic Transduction Logic Device.

The PiezoElectronic transistor (PET), has been proposed as a transduction device not subject to the voltage limits of field-effect transistors. The PET transduces voltage to stress, activating a facile insulator-metal transition, thereby achieving multi-gigahertz switching speeds, as predicted by modeling - at lower power than the comparable generation field effect transistor (FET). Here, the fabrication and measurement of the first physical PET devices are reported, showing both On/Off switching and cyclin...


The Strong Influence of Internal Stresses on the Nucleation of a Nanosized, Deeply Undercooled Melt at a Solid-Solid Phase Interface.

The effect of elastic energy on nucleation and disappearance of a nanometer size intermediate melt (IM) region at a solid-solid (S1S2) phase interface at temperatures 120 K below the melting temperature is studied using a phase-field approach. Results are obtained for broad range of the ratios of S1S2 to solid-melt interface energies, kE, and widths, kδ. It is found that internal stresses only slightly promote barrierless IM nucleation but qualitatively alter the system behavior, allowing for the appearanc...


Correction to Shape- and Symmetry-Dependent Mechanical Properties of Metallic Gold and Silver on the Nanoscale.


Defective interfaces in Yttrium-doped Barium Zirconate films and consequences on proton conduction.

Yttrium doped Barium Zirconate (BZY) thin films recently showed surprising electric transport properties. Experimental investigations conducted mainly by electrochemical impedance spectroscopy suggested that a consistent part of this BZY conductivity is of protonic nature. These results have stimulated further investigations by local unconventional techniques. Here we use Electrochemical Strain Microscopy (ESM) to detect electrochemical activity in BZY films with nanoscale resolution. ESM in a novel cross s...

Thursday 13th September 1195

Dendrimer-inspired nanomaterials for the in vivo delivery of siRNA to lung vasculature.

Targeted RNA delivery to lung endothelial cells has potential for treatment for conditions that involve inflammation, such as chronic asthma, and obstructive pulmonary disease. To this end, chemically-modified dendrimer nanomaterials were synthesized and optimized for targeted small interfering RNA (siRNA) delivery to lung vasculature. Using a combinatorial approach, the free amines on multigenerational poly(amido amine) and poly(propylenimine) dendrimers were substituted with alkyl chains of increasing len...

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