PubMed Journal Database | Nano letters RSS

16:50 EST 27th November 2014 | BioPortfolio

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Showing PubMed Articles 1–25 of 2,100+ from Nano letters

Monday 2nd March 1124

Metal Seed Layer Thickness-Induced Transition From Vertical to Horizontal Growth of MoS2 and WS2.

Two-dimensional (2D), layered transition metal dichalcogenides (TMDCs) can grow in two different growth directions, i.e., horizontal and vertical. In the horizontal growth, 2D TMDC layers grow in planar direction with their basal planes parallel to growth substrates. In the vertical growth, 2D TMDC layers grow standing upright on growth substrates exposing their edge sites rather than their basal planes. The two distinct morphologies present unique materials properties suitable for specific applications, su...

Wednesday 3rd July 1123

Measurement of Emission Lifetime Dynamics and Biexciton Emission Quantum Yield of Individual InAs Colloidal Nanocrystals.

Monday 25th February 1123

A Flexible Alkaline Rechargeable Ni/Fe Battery Based on Graphene Foam/Carbon Nanotubes Hybrid Film.

The development of portable and wearable electronics has promoted increasing demand for high-performance power sources with high energy/power density, low cost, lightweight, as well as ultrathin and flexible features. Here, a new type of flexible Ni/Fe cell is designed and fabricated by employing Ni(OH)2 nanosheets and porous Fe2O3 nanorods grown on lightweight and graphene foam (GF)/carbon nanotubes (CNTs) hybrid films as electrodes. The assembled f-Ni/Fe cells are able to deliver high energy/power densiti...

1122998

Interfacial localization and voltage-tunable arrays of charged nanoparticles.

Experiments and computer simulations provide a new perspective that strong correlations of counterions with charged nanoparticles can influence the localization of nanoparticles at liquid-liquid interfaces and support the formation of voltage-tunable nanoparticle arrays. We show that ion condensation onto charged nanoparticles facilitates their transport from the aqueous-side of an interface between two immiscible electrolyte solutions to the organic-side, but contiguous to the interface. Counterion condens...

1122992

Efficient Modulation of 1.55 µm Radiation with Gated Graphene on a Silicon Micro-ring Resonator.

The gate-controllability of the Fermi-edge onset of interband absorption in graphene can be utilized to modulate near-infrared radiation in the telecommunication band. However, a high modulation efficiency has not been demonstrated to date, because of the small amount of light absorption in graphene. Here, we demonstrate a ~40% amplitude modulation of 1.55 µm radiation with gated single-layer graphene that is coupled with a silicon micro-ring resonator. Both the quality factor and resonance wavelength of t...

1120600

Gated Hall Effect of Nanoplate Devices Reveals Surface-State-Induced Surface Inversion in Iron Pyrite Semiconductor.

Understanding semiconductor surface states is critical for their applications, but fully characterizing surface electrical properties is challenging. Such a challenge is especially crippling for semiconducting iron pyrite (FeS2), whose potential for solar energy conversion has been suggested to be held back by rich surface states. Here, by taking advantage of the high surface-to-bulk ratio in nanostructures and effective electrolyte gating, we develop a general method to fully characterize both the surface ...

1119654

Friction of water on graphene and hexagonal Boron Nitride from ab initio methods: very different slippage despite very similar interface structures.

Friction is one of the main sources of dissipation at liquid water/solid interfaces. Despite recent progress, a detailed understanding of water/solid friction in connection with the structure and energetics of the solid surface is lacking. Here we show for the first time that ab initio molecular dynamics can be used to unravel the connection between the structure of nanoscale water and friction for liquid water in contact with graphene and with hexagonal boron nitride. We find that whilst the interface pres...

1119577

The Effect of Nanostructures on the Meniscus Shape and Disjoining Pressure of Ultra-Thin Liquid Film.

The stability of thin liquid films on nanostructured surfaces is important but poorly understood. Here, we develop a general model of the meniscus shape and disjoining pressure for thin liquid films on nanostructured surfaces based on the minimization of the free energy and the Derjaguin approximation. This model is then compared with molecular dynamics simulations for a water-gold system with triangular and square nanostructures of varying depth and film thickness, demonstrating the robustness of the analy...

1118986

Catalyst-Directed Crystallographic Orientation Control of GaN Nanowire Growth.

In this work, we demonstrate that catalyst composition can be used to direct the crystallographic growth axis of GaN nanowires. By adjusting the ratio of gold to nickel in a bimetallic catalyst, we achieved selective growth of dense, uniform nanowire arrays along two non polar directions. A gold rich catalyst resulted in single crystalline nanowire growth along the or m axis, while a nickel rich catalyst resulted in nanowire growth along the or a axis. The same growth control was demonstrated on two diffe...

Tuesday 16th April 1117

Switching individual quantum dot emission through electrically controlling resonant energy transfer to graphene.

Electrically controlling resonant energy transfer of optical emitters provides a novel mechanism to switch nanoscale light sources on and off individually for optoelectronic applications. Graphene's optical transitions are tunable through electrostatic gating over a broad wavelength spectrum, making it possible to modulate energy transfer from a variety of nano-emitters to graphene at room temperature. We demonstrate photoluminescence switching of individual colloidal quantum dots by electrically tuning the...

Tuesday 8th January 1117

Atomically Thin Heterostructures based on Single-Layer Tungsten Diselenide and Graphene.

Heterogeneous engineering of two-dimensional layered materials, including metallic graphene and semiconducting transition metal dichalcogenides, presents an exciting opportunity to produce highly tunable electronic and optoelectronic systems. In order to engineer pristine layers and their interfaces, epitaxial growth of such heterostructures is required. We report the direct growth of crystalline, monolayer tungsten diselenide (WSe2) on epitaxial graphene (EG) grown from silicon carbide. Raman spectroscopy,...

1114909

Highly Specific Plasmonic Biosensors for Ultrasensitive MicroRNA Detection in Plasma from Pancreatic Cancer Patients.

MicroRNAs (miRs) are small noncoding RNAs that regulate mRNA stability and/or translation. Because of their release into the circulation and their remarkable stability, miR levels in plasma and other biological fluids can serve as diagnostic and prognostic disease biomarkers. However, quantifying miRs in the circulation is challenging due to issues with sensitivity and specificity. This Letter describes for the first time the design and characterization of a regenerative, solid-state localized surface plasm...

1114816

Subwavelength lattice optics by evolutionary design.

This paper describes a new class of structured optical materials-lattice opto-materials-that can manipulate the flow of visible light into a wide range of three dimensional profiles using evolutionary design principles. Lattice opto-materials are based on the discretization of a surface into a two-dimensional (2D) subwavelength lattice whose individual lattice sites can be controlled to achieve a programmed optical response. To access a desired optical property, we designed a lattice evolutionary algorithm ...

1114737

Effective Passivation of Exfoliated Black Phosphorus Transistors Against Ambient Degradation.

Unencapsulated, exfoliated black phosphorus (BP) flakes are found to chemically degrade upon exposure to ambient conditions. Atomic force microscopy, electrostatic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy are employed to characterize the structure and chemistry of the degradation process, suggesting that O2 saturated H2O irreversibly reacts with BP to form oxidized phosphorus species. This interpretation is further supp...

Tuesday 9th November 1114

Conserved Atomic Bonding Sequences and Strain Organization of Graphene Grain Boundaries.

The bulk properties of polycrystalline materials are directly influenced by the atomic structure at the grain boundaries that join neighboring crystallites. In this work, we show that graphene grain boundaries are comprised of structural building blocks of conserved atomic bonding sequences using aberration corrected high-resolution transmission electron microscopy. These sequences appear as stretches of identically arranged periodic or aperiodic regions of dislocations. Atomic scale strain and lattice rota...

Wednesday 17th February 1114

Engineering curvature in graphene ribbons using ultra-thin polymer films.

We propose a method to induce curvature in graphene nanoribbons in a controlled manner using an ultra-thin thermoset polymer in a bi-material strip setup and test it via molecular dynamics (MD) simulations. Continuum mechanics shows that curvature develops to release the residual stress caused by the chemical and thermal shrinkage of the polymer during processing and that this curvature increases with decreasing film thickness; however, significant deformation is only achieved for ultra-thin polymer films. ...

1113933

Entropy-Mediated Mechanical Response of the Interfacial Nanoparticle Patterning.

The precise organization of nano-objects into well-defined patterns at interfaces is an outstanding challenge in the field of nanocomposites towards technologically important materials and devices. Herein, by means of computer simulations we show novel mechanical response behaviors emerging from binary mixtures of tethered Janus nanoparticles at the interface of a binary fluid mixture under mechanical pressure. Our simulations demonstrate that the nanoparticle organization in the systems undergo reversible ...

1113677

Atomic Scale Mechanisms of Friction Reduction and Wear Protection by Graphene.

We study nanoindentation and scratching of graphene-covered Pt(111) surfaces in computer simulations and experiments. We find elastic response at low load, plastic deformation of Pt below the graphene at intermediate load, and eventual rupture of the graphene at high load. Friction remains low in the first two regimes, but jumps to values also found for bare Pt(111) surfaces upon graphene rupture. While graphene substantially enhances the load carrying capacity of the Pt substrate, the substrate's intrinsic...

1113544

Two-dimensional metal-chalcogenide films in tunable optical microcavities.

Integration of quasi-two-dimensional (2D) films of metal-chalcogenides in optical microcavities permits new photonic applications of these materials. Here we present tunable microcavities with monolayer MoS2 or few monolayer GaSe films. We observe significant modification of spectral and temporal properties of photoluminescence (PL): PL is emitted in spectrally narrow and wavelength-tunable cavity modes with quality factors up to 7400; a ten-fold PL lifetime shortening is achieved, a consequence of Purcell ...

1113478

IR Near-Field Spectroscopy and Imaging of Single LixFePO4 Microcrystals.

This study demonstrates unique capability of infrared near-field nanoscopy combined with Fourier transform infrared (FTIR) spectroscopy to map phases distribution in microcrystals of LixFePO4, a positive electrode material for Li-ion batteries. Ex situ nano-scale IR imaging provides direct evidence for the coexistence of LiFePO4 and FePO4 phases in partially delithiated single crystal microparticles. A quantitative 3-D tomographic reconstruction of the phase distribution within a single microcrystal provide...

1113395

Observation of the inverse giant piezoresistance effect in silicon nanomembranes probed by ultrafast terahertz spectroscopy.

The anomalous piezoresistance (a-PZR) effects, including giant PZR (GPZR) with large magnitude and inverse PZR of opposite, have exciting technological potentials for their integration into novel nanoelectromechanical systems. However, the nature of a-PZR effect and the associated kinetics have not been clearly determined yet. Even further, there are intense research debates whether the a-PZR effect actually exists or not; although numerous investigations have been conducted, the origin of the effect has no...

Thursday 30th April 1113

Etched Colloidal LiFePO4 Nanoplatelets Towards High-Rate Capable Li-ion Battery Electrodes.

LiFePO4 has been intensively investigated as a cathode material in Li-ion batteries, as it can in principle enable the development of high power electrodes. LiFePO4, on the other hand, is inherently "plagued" by poor electronic and ionic conductivity. While the problems with low electron conductivity are partially alleviated by carbon coating and further by doping or by downsizing the active particles to nanoscale dimensions, poor ionic conductivity is still an issue. In order to develop colloidally synthes...

Tuesday 20th January 1113

Accelerating the design of solar Thermal Fuel Materials through high throughput simulations.

Solar thermal fuels (STF) store the energy of sunlight, which can then be released later in the form of heat, offering an emission-free and renewable solution for both solar energy conversion and storage. However, this approach is currently limited by the lack of low-cost materials with high energy density and high stability. In this letter, we present an ab initio high-throughput computational approach to accelerate the design process and allow for searches over a broad class of materials. The high-through...

1112949

Nanoscale Surface Potential Variation Correlates with Local S/Se Ratio in Solution-Processed CZTSSe Solar Cells.

Thin film solar cells made from Cu, Zn, Sn, S/Se can be processed from solution to yield high-performing kesterite (CZTS or CZTSSe) photovoltaics. We present a microstructural study of solution-deposited CZTSSe films prepared by nanocrystal-based ink approaches using scanning probe microscopy (SPM) and scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS). We correlate scanning Kelvin probe microscopy (SKPM) maps of local surface potential with SEM/EDS images of the exac...

1112850

Scalable Fracture-free SiOC Glass Coating for Robust Silicon Nanoparticle Anodes in Lithium Secondary Batteries.

A variety of silicon (Si) nanostructures and their complex composites have been lately introduced in the lithium ion battery community to address the large volume changes of Si anodes during their repeated charge-discharge cycles. Nevertheless, for large-scale manufacturing, it is more desirable to use commercial Si nanoparticles with simple surface coating. Most conductive coating materials, however, do not accommodate the volume expansion of the inner Si active phases and resultantly fracture during cycli...


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