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14:07 EDT 30th August 2015 | BioPortfolio

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Showing PubMed Articles 1–25 of 2,600+ from Nano letters


Partial Dislocations in Graphene and Their Atomic Level Migration Dynamics.

We demonstrate the formation of partial dislocations in graphene at elevated temperatures of ≥500 °C with single atom resolution aberration corrected transmission electron microscopy. The partial dislocations spatially redistribute strain in the lattice, providing an energetically more favorable configuration to the perfect dislocation. Low-energy migration paths mediated by partial dislocation formation have been observed, providing insights into the atomistic dynamics of graphene during annealing. Thes...


Engineering Acoustic Phonons and Electron-Phonon Coupling by the Nanoscale Interface.

Precise engineering of phonon-phonon (ph-ph) and electron-phonon (e-ph) interactions by materials design is essential for an in-depth understanding of thermal, electrical, and optical phenomena as well as new technology breakthrough governed by fundamental physical laws. Due to their characteristic length scale, the ph-ph and e-ph interactions can be dramatically modified by nanoscale spatial confinement, thus opening up opportunities to finely maneuver underlying coupling processes through the interplay of...


Strong resistance to bending observed for nanoparticle membranes.

We demonstrate how gold nanoparticle monolayers can be curled up into hollow scrolls that make it possible to extract both bending and stretching moduli from indentation by atomic force microscopy. We find a bending modulus that is two orders of magnitudes larger than predicted by standard continuum elasticity, an enhancement we associate with non-local micro-structural constraints. This finding opens up new opportunities for independent control of resistance to bending and stretching at the nanoscale.


Nanocrystallization in Oxyfluoride Glasses Controlled by Amorphous Phase Separation.

Transparent bulk glass-ceramics containing ZnF2, K2SiF6 and KZnF3 nanocrystals are successfully obtained from xKF-xZnF2-(100-2x)SiO2 oxyfluoride glasses for the first time, to the best of our knowledge. The glass transition temperatures of heat-treated samples increase with time and approach values which resemble the temperatures chosen for thermal treatment. During nucleation and crystal growth, the residual glass around the crystals is depleted in fluoride which as glass component usually leads to a decre...


First-principles theoretical studies and nano-calorimetry experiments on solid-state alloying of Zr-B.

The thermodynamics and kinetics of the solid-state alloying of Zr-B, underlying a variety of synthesis processes of the ultra-high-temperature ceramic ZrB2, are widely unknown. We investigate the energetics, diffusion kinetics, and structural evolution of this system using first-principles computational methods. We identify the diffusion pathways in the interpenetrating network of interstitial sites for a single B atom, and demonstrate a dominant rate-controlling step from the octahedral to the crowdion sit...


Optimized solid-liquid interface enabling ultra-high charging and discharging rate for advanced lithium-ion batteries.

LiFePO4 has long been held as one of the most promising battery cathode for its high energy storage capacity. Meanwhile, although extensive studies have been conducted on the interfacial chemistries in Li-ion batteries1-3, little is known on the atomic level about the solid-liquid interface of LiFePO4/electrolyte. Here we report battery cathode consisted with nanosized LiFePO4 particles in aqueous electrolyte with an high charging and discharging rate of 600 C (3600/600 = 6 second charge time, 1 C=170 mAh g...


Solvothermal synthesis of lateral heterojunction Sb2Te3/Bi2Te3 nanoplates.

A lateral heterojunction of topological insulator Sb2Te3/Bi2Te3 was successfully synthesized, where in-plane epitaxial growth and one-dimensional dislocation were visualized by the high-resolution transmission electron microscopy. The semiconducting temperature-resistance curve and crossjunction rectification were realized. First-principle calculations and transport analysis revealed a staggered-gap lateral heterojunction with a small junction field. Topological surface states were demonstrated to be well m...


Scalable Growth of High Mobility Dirac Semimetal Cd3As2 Microbelts.

Three dimensional (3D) Dirac semimetals are 3D analogue of graphene, which display Dirac points with linear dispersion in k-space, stabilized by crystal symmetry. Cd3As2 was predicted to be 3D Dirac semimetals and were subsequently demonstrated by photoemission experiments. As unveiled by transport measurements, several exotic phases, such as Weyl semimetals, topological insulators, and topological superconductors, can be deduced by breaking time reversal or inversion symmetry. Here, we reported a facile an...


Direct CVD-derived graphene glasses targeting wide ranged applications.

Direct growth of graphene on traditional glasses is of great importance for various daily-life applications. We report herein the catalyst-free atmospheric-pressure chemical vapor deposition approach to directly synthesizing large-area, uniform graphene films on solid glasses. The optical transparency and sheet resistance of such kinds of graphene glasses can be readily adjusted together with the experimentally-tunable layer thickness of graphene. More significantly, these graphene glasses find a broad rang...


Directly observing the lipid-dependent self-assembly and pore-forming mechanism of the cytolytic toxin listeriolysin O.

Listeriolysin O (LLO) is the major virulence factor of Listeria monocytogenes and a member of the cholesterol-dependent cytolysin (CDC) family. Gram-positive pathogenic bacteria produce water-soluble CDC monomers that bind cholesterol-dependent to the lipid membrane of the attacked cell or of the phagosome, oligomerize into prepores and insert into the membrane to form transmembrane pores. However, the mechanisms guiding LLO towards pore formation are poorly understood. Using electron microscopy and time-la...

Monday 5th December 1323

Direct visualization of walking motions of photocontrolled nanomachine on the DNA nanostructure.

A light-driven artificial molecular nanomachine was constructed based on DNA scaffolding. Pyrene-modified walking strands and disulfide bond-connected stator strands, employed as anchorage sites to support walker movement, were assembled into a 2D DNA tile. Pyrene molecules excited by photoirradiation at 350 nm induced cleavage of disulfide bond-connected stator strands, enabling the DNA walker to migrate from one cleaved stator to the next on the DNA tile. Importantly, the light-fuelled movements of the na...

Sunday 28th August 1323

Electrostatic Force Microscopic Characterization of Early Stage Carbon Deposition on Nickel Anodes in Solid Oxide Fuel Cells.

Carbon deposition on nickel anodes degrades the performance of solid oxide fuel cells that utilize hydrocarbon fuels. Nickel anodes with BaO nanoclusters deposited on the surface exhibit improved performance by delaying carbon deposition (i.e. coking). The goal of this research was to visualize early stage deposition of carbon on nickel surface and to identify the role BaO nanoclusters play in coking resistance. Electrostatic force microscopy was employed to spatially map carbon deposition on nickel foils p...


Structural Transition in Layered As1-xPx Compounds: A Computational Study.

As a way to further improve the electronic properties of group V layered semiconductors, we propose to form in-layer 2D heterostructures of black phosphorus and grey arsenic. We use ab initio density functional theory to optimize the geometry, determine the electronic structure, and identify the most stable allotropes as a function of composition. Since pure black phosphorus and pure grey arsenic monolayers differ in their equilibrium structure, we predict a structural transition and a change in frontier st...


Three-dimensional crystalline/amorphous Co/Co3O4 core/shell nanosheets as efficient electrocatalysts for hydrogen evolution reaction.

Earth-abundant, low-cost electrocatalysts with outstanding catalytic activity in electrochemical hydrogen evolution reaction are critical in realizing the hydrogen economy to lift our future welfare and civilization. Here, we report that excellent hydrogen evolution reaction activity has been achieved with three-dimensional core/shell Co/Co3O4 nanosheets composed of a metallic cobalt core and an amorphous cobalt oxide shell. A benchmark HER current density of 10 mA cm-2 is achieved at an overpotential of ~ ...


Emergence of one-dimensional wires of free carriers in transition-metal-dichalcogenide nanostructures.

We highlight the emergence of metallic states in two-dimensional transition-metal-dichalcogenide nanostructures --nanoribbons, islands, and inversion domain boundaries-- as a widespread and universal phenomenon driven by the polar discontinuities occurring at their edges or boundaries. We show that such metallic states form one-dimensional wires of electrons or holes, with a free charge density that increases with the system size, up to complete screening of the polarization charge, and can also be controll...


Defect-Induced Conical Intersections Promote Non-Radiative Recombination.

We apply multireference electronic structure calculations to demonstrate the presence of conical intersections between the ground and first excited electronic states of three silicon nanocrystals containing defects characteristic of the oxidized silicon surface. These intersections are accessible upon excitation at visible wavelengths and are predicted to facilitate non-radiative recombination with a rate that increases with decreasing particle size. This work illustrates a new framework for identifying def...


Probing the Structure, Composition and Spatial Distribution of Ligands on Gold Nanorods.

The structure and size of ligands attached to the surfaces of gold nanorods, such as adsorbed surfactants or grafted polymers, are important considerations that facilitate the use of such nanoparticles in the human body, in advanced materials for energy harvesting, or in devices for single molecule detection. Here, we report small-angle neutron scattering (SANS) measurements from surfactant or poly(ethylene glycol) (PEG) coated gold nanorods in solution, which quantitatively determine the location, structur...


Fast and efficient preparation of exfoliated 2H MoS2 nanosheets by sonication-assisted lithium intercalation and infrared laser-induced 1T to 2H phase reversion.

Exfoliated 2H molybdenum disulfide (MoS2) has unique properties and potential applications in a wide range of fields, but corresponding studies have been hampered by the lack of effective routes to its bulk quantities. This study presents a rapid and efficient route to obtain exfoliated 2H MoS2, which combines fast sonication-assisted lithium intercalation and infrared (IR) laser-induced phase reversion. We found that the complete lithium intercalation of MoS2 with butyllithium could be effected within 1.5 ...


Independent tuning of electronic properties and ferromagnetism in topological insulators with heterostructure approach.

The quantum anomalous Hall effect (QAHE) has been demonstrated in Cr- and V-doped topological insulators (TIs) below 100 mK. In those materials, the spins of unfilled d-electrons in the transition metal dopants are exchange coupled to develop a long-range ferromagnetic order. However, the addition of random dopants unavoidably introduces paramagnetic spins that can adversely affect the chiral edge transport in QAHE. In this work, we show a heterostructure approach to independently tune the electronic and ma...


Sodiation Kinetics of Metal Oxide Conversion Electrodes: a Comparative Study with Lithiation.

The development of sodium ion batteries (NIBs) can provide an alternative to lithium ion batteries (LIBs) for sustainable, low-cost energy storage. However, due to the larger size and higher m/e ratio of the sodium ion compared to lithium, sodiation reactions of candidate electrodes are expected to differ in significant ways from the corresponding lithium ones. In this work, we investigated the sodiation mechanism of a typical transition metal-oxide, NiO, through a set of correlated techniques, including el...


Wedge Waveguides and Resonators for Quantum Plasmonics.

Plasmonic structures can provide deep-subwavelength electromagnetic fields useful for enhancing light-matter interactions. However, because these localized modes are also dissipative, structures that offer the best compromise between field confinement and loss have been sought. Metallic wedge waveguides were initially identified as an ideal candidate, but have been largely abandoned because their experimental performance has so far been limited. We combine state-of-the-art metallic wedges with integrated re...

Saturday 15th October 1317

On the Kapitza Resistance Between Few-Layer Graphene and Water: Liquid Layering Effects.

The Kapitza resistance (R_k) between few-layer graphene (FLG) and water was studied using molecular dynamics simulations. The R_k was found to depend on the number of the layers in the FLG though, surprisingly, {\it not} on the water block thickness. This distinct size dependence is attributed to the large difference in the phonon mean free path between the FLG and water. Remarkably, R_k is strongly dependent on the layering of water adjacent to the FLG, exhibiting an inverse proportionality relationship to...

Friday 27th May 1317

Large Area Directed Self-Assembly of Sub-10 nm Particles with Single Particle Positioning Resolution.

Directed self-assembly of nanoparticles (DSA-n) holds great potential for device miniaturization in providing patterning resolution and throughput that exceed existing lithographic capabilities. While nanoparticles excel at assembling into regular close-packed arrays, actual devices on the other hand are often laid out in sparse and complex configurations. Hence, the deterministic positioning of single or few particles at specific positions with low defect density is imperative. Here, we report an approach ...


Carbon Dots: A Unique Fluorescent Cocktail of Polycyclic Aromatic Hydrocarbons.

Carbon dots (CDs) have attracted rapidly growing interest in recent years due to their unique and tunable optical properties, the low cost of fabrication and their wide-spread uses. However, due to the complex structure of CDs, both the molecular ingredients and the intrinsic mechanisms governing photoluminescence of CDs are poorly understood. Among other features, a large Stokes shift of over 100 nm and a photoluminescence spectrally dependent on the excitation wavelength, have so far not been adequately e...

Saturday 16th October 1316

Second-Harmonic Generation from Sub-5-nm Gaps by Directed Self-Assembly of Nanoparticles onto Template-Stripped Gold Substrates.

Strong field enhancement and confinement in plasmonic nanostructures provide suitable conditions for nonlinear optics in ultra-compact dimensions. Despite these enhancements, second-harmonic generation (SHG) is still inefficient due to the centrosymmetric crystal structure of the bulk metals used, e.g. Au, and Ag. Taking advantage of symmetry breaking at the metal surface, one could greatly enhance SHG by engineering these metal surfaces in regions where the strong electric fields are localized. Here, we co...