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11:47 EST 4th March 2015 | BioPortfolio

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Showing PubMed Articles 1–25 of 2,200+ from Nano letters


Systematics of molecular self-assembled networks at topological insulators surfaces.

The success of topological insulators (TI) in creating devices with unique functionalities is directly connected to the ability of coupling their helical spin states to well defined perturbations. However, up to now, TI-based heterostructures always resulted in very disordered interfaces, characterized by strong mesoscopic fluctuations of the chemical potential which make the spin-momentum locking ill-defined over length scales of few nanometers or even completely destroy topological states. These limitatio...


Unveiling Surface Redox Charge Storage of Interacting Two-Dimensional Hetero-Nanosheets in Hierarchical Architectures.

Two-dimensional (2D) hetero-nanosheets are currently the focus of intense study due to the unique properties that emerge from the strong interplay between two low-dimensional nanomaterials with different properties. However, the properties and new phenomena based on the strongly interacting, two 2D hetero-nanosheets in a 3D hierarchical architecture have yet to be explored. Here, we unveil the surface redox charge storage mechanism of surface-exposed WS2 nanosheets assembled in a 3D hierarchical heterostruc...

Friday 10th November 1183

Demonstrating photoluminescence from Au is electronic inelastic light scattering of a plasmonic metal: the origin of SERS backgrounds.

Temperature-dependent surface-enhanced Raman scattering (SERS) is used to investigate the background continuum always present in SERS but whose origin remains controversial. Both the Stokes and anti-Stokes background is found to be dominated by inelastic light scattering (ILS) from the electrons in the noble metal nanostructures supporting the plasmon modes. The anti-Stokes background is highly temperature dependent, and is shown to be related to the thermal occupation of electronic states within the metal ...

Sunday 7th May 1183

Observation of single-spin Dirac fermions at the graphene/ferromagnet interface.

With the discovery and first characterization of graphene, its potential for spintronic applications was recognized immediately. Since then an active field of research has developed trying to overcome the practical hurdles. One of the most severe challenges is to find appropriate interfaces between graphene and ferromagnetic layers, which are granting efficient injection of spin-polarized electrons. Here we show that graphene grown under appropriate conditions on Co(0001) demonstrates perfect structural pro...


Voltage Controlled Ferroelastic Switching in Pb(Zr0.2Ti0.8)O3 thin films.

We report a voltage controlled reversible creation and annihilation of $a$-axis oriented $\sim$10 nm wide ferroelastic nanodomains without a concurrent ferroelectric 180$^\circ$ switching of the surrounding $c$-domain matrix in archetypal ferroelectric Pb(Zr$_{0.2}$Ti$_{0.8}$)O$_3$ thin films by using the piezo-response force microscopy technique. In previous studies, the coupled nature of ferroelectric switching and ferroelastic rotation has made it difficult to differentiate the underlying physics of ferr...


Real-time Visualization of Nanoparticles Interacting with Glioblastoma Stem Cells.

Nanoparticle-based therapy represents a novel and promising approach to treat glioblastoma, the most common and lethal malignant brain cancer. Although similar therapies have achieved significant cytotoxicity in cultured glioblastoma or glioblastoma stem cells (GSCs), the lack of an appropriate approach to monitor interactions between cells and nanoparticle-based therapies impedes their further clinical application in human patients. To address this critical issue, we first obtained NOTCH1 positive GSCs fro...


Enhanced Light Emission from Large-Area Monolayer MoS2 using Plasmonic Nanodisc Arrays.

Single-layer direct band-gap semiconductors such as transition metal dichalcogenides are quite attractive for a wide range of electronics, photonics and optoelectronics applications. Their monolayer thickness provides significant advantages in many applications such as field-effect transistors for high-performance electronics, sensor / detector applications, and flexible electronics. However, for optoelectronics and photonics applications, inherent monolayer thickness poses a significant challenge for the i...


Visualizing the interior architecture of focal adhesions with high-resolution traction maps.

Focal adhesions (FAs) are micron-sized protein assemblies that coordinate cell adhesion, migration, and mechanotransduction. How the many proteins within FAs are organized into force sensing and transmitting structures is poorly understood. We combined fluorescent molecular tension sensors with super-resolution light microscopy to visualize traction forces within FAs with


Luminescence Blinking of a Reacting Quantum Dot.

Luminescence blinking is an inherent feature of optical emission from individual fluorescent molecules and quantum dots. There have been intense efforts, although not with complete resolution, toward the understanding of the mechanistic origin of blinking and also its mitigation in quantum dots. As an advance in our microscopic view of blinking, we show that the luminescence blinking of a quantum dot becomes unusually heavy in the temporal vicinity of a reactive transformation. This stage of heavy blinking ...

Friday 11th November 1182

Space-charge limited transport in large-area monolayer hexagonal boron nitride.

Hexagonal boron nitride (hBN) is a wide-gap material that has attracted significant attention as an ideal dielectric substrate for 2D crystal heterostructures. We report here the first observation of in-plane charge transport in large-area monolayer hBN, grown by chemical vapor deposition. The quadratic scaling of current with voltage at high bias corresponds to a space-charge limited conduction mechanism, with a room temperature mobility reaching up to 0.01 cm2/Vs at electric fields up to 100 kV/cm in the ...

Monday 19th September 1182

A Half Millimeter Thick Co-planar Flexible Battery.

Most of the existing flexible lithium ion batteries (LIBs) adopt the conventional co-facial cell configuration where anode, separator, and cathode are sequentially stacked, and so have difficulty in the integration with emerging thin LIB applications, such as smart cards and medical patches. In order to overcome this shortcoming, herein, we report a co-planar cell structure in which anodes and cathodes are interdigitatedly positioned on the same plane. The co-planar electrode design brings advantages of enh...

Sunday 19th June 1182

Weak antilocalization effect of topological crystalline insulator Pb1-xSnxTe nanowires with tunable composition and distinct {100} facets.

Pb1-xSnxTe is an unique topological crystalline insulator (TCI) which undergoes a topological phase transition from topological trivial insulator to TCI with the change of Sn content and temperature. Meanwhile, the surface states properties of Pb1-xSnxTe are strongly dependent on crystallographic plane orientation. In this work, we first reported controllable synthesis of rectangular prismatic PbxSn1-xTe nanowires by vapor deposition method. Rectangular prismatic PbxSn1-xTe nanowires exhibits distinct {100}...

Wednesday 6th April 1182

A Three State Nanofluidic Field Effect Switch.

We report a 3-state nanofluidic field effect switch in an asymmetrically gated device with a forward (positive), "off" (zero), and a reverse (negative) current state for tunable control of ionic transport by systematically controlling the gate potential. The embedded gate electrode allows for modulation of the ionic current through the 16 nm deep channels as a function of electrolyte concentration and gate electrode location for a fixed streamwise potential.


Plasmonic nanostructured metal-oxide-semiconductor reflection modulators.

We propose a plasmonic surface that produces an electrically-controlled reflectance as a high-speed intensity modulator. The device is conceived as a metal-oxide-semiconductor capacitor on silicon with its metal structured as a thin patch bearing a contiguous nanoscale grating. The metal structure serves multiple functions, as a driving electrode and as a grating coupler for perpendicularly-incident p-polarised light to surface plasmons supported by the patch. Modulation is produced by charging and discharg...


Ultrasensitive room temperature piezoresistive transduction in graphene-based nanoelectromechanical systems.

The low mass and high quality factors that nanomechanical resonators exhibit lead to exceptional sensitivity in the frequency domain. This is especially appealing for the design of ultrasensitive force and mass sensors. The sensitivity of a nanomechanical mass and force sensor depends on its mass and quality factor; a low resonator mass and a higher quality factor reduce both the minimum resolvable mass and force. Graphene, a single atomic layer thick membrane is an ideal candidate for nanoelectromechanical...


Superlinear Composition-Dependent Photocurrent in CVD-Grown Monolayer MoS2(1-x)Se2x Alloy Devices.

Transition metal dichalcogenides (TMDs) have emerged as a new class of two-dimensional materials that are promising for electronics and photonics. To date, optoelectronic measurements in these materials have shown the conventional behavior expected from photoconductors, such as a linear or sublinear dependence of the photocurrent on light intensity. Here we report the observation of a new regime of operation where the photocurrent depends superlinearly on light intensity. We use spatially-resolved photocurr...


Functionalization of Transition Metal Dichalcogenides with Metallic Nanoparticles: Implications for Doping and Gas-Sensing.

Transition Metal Dichalcogenides (TMDs), belonging to the class of two-dimensional (2D) layered materials, have instigated a lot of interest in diverse application fields due to their unique electrical, mechanical, magnetic and optical properties. Tuning the electrical properties of TMDs through charge transfer or doping is necessary for various optoelectronic applications. This paper presents the experimental investigation of the doping effect on TMDs, mainly focusing on molybdenum disulphide (MoS2), by me...

Friday 13th November 1180

Growth of Au on Pt Icosahedral Nanoparticles Revealed by Low-Dose in situ TEM.

A growth mode was revealed by an in situ TEM study of nucleation and growth of Au on Pt icosahedral nanoparticles. Quantitative analysis of growth kinetics was carried out based on real-time TEM data, which show the process involves: 1) deposition of Au on corner sites of Pt icosahedral nanoparticles, 2) diffusion of Au from corners to terraces and edges, and 3) subsequent layer-by-layer growth of Au on Au surfaces to form Pt@Au core-shell nanoparticles. The in situ TEM results indicate diffusion of Au from...

Friday 12th June 1180

Coherent Plasmon-Exciton Coupling in Silver Platelet-J-aggregate Nanocomposites.

Hybrid nanostructures that couple plasmon and exciton resonances generate hybridized energy states, called plexcitons, which may result in unusual light-matter interactions. We report the observation of a transparency dip in the visible spectra of colloidal suspensions containing silver nanoplatelets and a cyanine dye, 1,1'-diethyl-2,2'-cyanine iodide (PIC). PIC was electrostatically adsorbed onto the surface of silver nanoplatelet core particles, forming an outer J-aggregate shell. This core-shell architec...

Monday 6th January 1180

A New Approach to Fully-Ordered fct-FePt Nanoparticles for Much Enhanced Electrocatalysis in Acid.

Fully-ordered face-centered tetragonal (fct) FePt nanoparticles (NPs) are synthesized by thermal annealing of the MgO-coated dumbbell-like FePt-Fe3O4 NPs followed by acid washing to remove MgO. These fct-FePt NPs show strong ferromagnetism with room temperature coercivity reaching 33 kOe. They serve as a robust electrocatalyst for the oxygen reduction reaction (ORR) in 0.1 M HClO4 and hydrogen evolution reaction (HER) in 0.5 M H2SO4 with much enhanced activity (the most active fct-structured alloy NP cataly...

Wednesday 1st January 1180

Wavelength Tunable Microdisk Cavity Light Source with a Chemically Enhanced MoS2 Emitter.

In this work, we report an integrated narrowband light source based on thin MoS2 emissive material coupled to the high quality factor whispering gallery modes of a microdisk cavity with a spatial notch enabling easy out-coupling of emission while yielding high spatial coherence and a Gaussian intensity distribution. The active light emitting material consists of chemically enhanced bilayer MoS2 flakes with a thin atomic layer deposited SiO2 protective coating yielding 20 times brighter chemically enhanced p...


Tuning Complex Transition Metal Hydroxide Nanostructures as Active Catalysts for Water Oxidation by a Laser-Chemical Route.

Diverse transition metal hydroxide nanostructures were synthesized by laser-induced hydrolysis in a liquid precursor solution for alkaline oxygen evolution reaction (OER). Several active OER catalysts with fine control of composition, structure and valence state were obtained, including (Lix)[Ni0.66Mn0.34(OH)2](NO3)·mH2O, Lix[Ni0.67(2+)Co0.33(2+)(OH)2](NO3)0.25(ORO)0.35·mH2O, etc. An operate overpotential less than 0.34 V at current density of 10 mA·cm(-2) was achieved. Such a controllable laser-chemical...


Oxidatively stable nanoporous silicon photocathodes with enhanced onset voltage for photoelectrochemical proton reduction.

Stable and high-performance nanoporous "black silicon" photoelectrodes with electrolessly deposited Pt nanoparticle (NP) catalysts are made with two metal-assisted etching steps. Doubly etched samples exhibit an ~300 mV positive shift in photocurrent onset for photoelectrochemical proton reduction compared to oxide-free planar Si with identical catalysts. We find that the photocurrent onset voltage of black Si photocathodes prepared from single-crystal planar Si wafers by an Ag-assisted etching process incr...

Tuesday 4th June 1179

Diblock copolymer micelles and supported films with non-covalently incorporated chromophores: a modular platform for efficient energy transfer.

We report generation of modular, artificial light-harvesting assemblies where an amphiphilic diblock copolymer, poly(ethylene oxide)-block-poly(butadiene), serves as the framework for non-covalent organization of BODIPY-based energy donor and bacteriochlorin-based energy acceptor chromophores. The assemblies are adaptive, forming well-defined micelles in aqueous solution and high-quality monolayer and bilayer films on solid supports, with the latter showing greater than 90% energy transfer efficiency. This ...

Tuesday 29th January 1179

Helicity resolved Raman scattering of MoS2, MoSe2, WS2 and WSe2 atomic layers.

The two-fold valley degeneracy in two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDCs) (Mo,W)(S,Se)2 is suitable for "valleytronics", the storage and manipulation of information utilizing the valley degree of freedom. The conservation of luminescent photon helicity in these 2D crystal monolayers has been widely regarded as a benchmark indicator for charge carrier valley polarization. Here we perform helicity resolved Raman scattering of the TMDC atomic layers. In drastic contrast to ...

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