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04:18 EDT 1st November 2014 | BioPortfolio

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Showing PubMed Articles 1–25 of 2,000+ from Nano letters

Tuesday 7th November 1110

Deterministic and Robust Generation of Single Photons from a Single Quantum Dot with 99.5% Indistinguishability Using Adiabatic Rapid Passage.

Single photons are attractive candidates of quantum bits (qubits) for quantum computation and are the best messengers in quantum networks. Future scalable, fault-tolerant photonic quantum technologies demand both stringently high levels of photon indistinguishability and generation efficiency. Here, we demonstrate deterministic and robust generation of pulsed resonance fluorescence single photons from a single semiconductor quantum dot using adiabatic rapid passage, a method robust against fluctuation of dr...

Monday 21st August 1110

Mechanical Strength of Nanoporous Graphene as a Desalination Membrane.

Recent advances in the development of nanoporous graphene (NPG) hold promise for the future of water supply by reverse osmosis (RO) desalination. But while previous studies have highlighted the potential of NPG as an RO membrane, there is less understanding as to whether NPG is strong enough to maintain its mechanical integrity under the high hydraulic pressures inherent to the RO desalination process. Here, we show that an NPG membrane can maintain its mechanical integrity in RO but that the choice of subs...


Highly Efficient Visible Light Photocatalytic Reduction of CO2 to Hydrocarbon Fuels by Cu-NPs Decorated Graphene Oxide.

The production of renewable solar fuel through CO2 photoreduction, namely artificial photosynthesis, has gained tremendous attention in recent times due to the limited availability of fossil-fuel resources and global climate change caused by rising anthropogenic CO2 in the atmosphere. In this study, graphene oxide (GO) decorated with copper nanoparticles (Cu-NPs), hereafter referred to as Cu/GO, has been used to enhance photocatalytic CO2 reduction under visible-light. A rapid one-pot microwave process was ...


Chemically Bonded Phosphorus/Graphene Hybrid as a High Performance Anode for Sodium-Ion Batteries.

Room temperature sodium-ion batteries are of great interest for high-energy-density energy storage systems because of low-cost, natural abundance of sodium. Here, we report a novel phosphorus/graphene nanosheet hybrid as a high performance anode for sodium-ion batteries through facile ball milling of red phosphorus and graphene stacks. The graphene stacks are mechanically exfoliated to nanosheets that chemically bond with the surfaces of phosphorus particles. This chemical bonding can facilitate robust and ...


Nanowires of lead-methylamine iodide (CH3NH3PbI3) prepared by low temperature solution-mediated crystallization.

We report the synthesis of lead-methylamine iodide (CH3NH3PbI3) nanowires by a low temperature solution processed crystallization using a simple slip-coating method. The anisotropic particle shape exhibits advantages over nanoparticles in terms of charge transport under illumination. These results provide a basis for solvent-mediated tailoring of structural properties like the crystallite size and orientation in trihalide perovskite thin films, which once implemented into a device, may ultimately result in ...

Tuesday 24th February 1108

Nanoscale Observation of Waveguide Modes Enhancing the Efficiency of Solar Cells.

Nanophotonic light management concepts are on the way to advance photovoltaic technologies and accelerate their economical breakthrough. Most of these concepts make use of light coupling to waveguide modes via nanophotonic structures such as photonic crystals, nanowires or plasmonic gratings. Experimentally, light coupling to these modes was so far exclusively investigated with indirect and macroscopic methods and thus, the nanoscale physics of light coupling and propagation of waveguide modes remain vague....


Semiconductor nanorod-carbon nanotube biomimetic films for wire-free photostimulation of blind retinas.

We report the development of a semiconductor nanorod-carbon nanotube based platform for wire-free, light induced retina stimulation. A plasma polymerized acrylic acid mid layer was used to achieve covalent conjugation of semiconductor nanorods directly onto neuro-adhesive, three-dimensional carbon nanotube surfaces. Photocurrent, photovoltage and fluorescence lifetime measurements validate efficient charge transfer between the nanorods and the carbon nanotube films. Successful stimulation of a light-insensi...

Monday 4th August 1107

High efficiency second harmonic generation from a single hybrid ZnO nanowire /Au plasmonic nano-oligomer.

We introduce a plasmonic-semiconductor hybrid nanosystem, consisting of a ZnO nanowire coupled to a gold pentamer oligomer by crossing the hot-spot. It is demonstrated that the hybrid system exhibits a second harmonic (SH) conversion efficiency of ~3x10-5%, which is among the highest values for a nanoscale object at optical frequencies reported so far. The SH intensity was found to be 1700 times larger than that from the same nanowire excited outside the hot-spot. Placing high nonlinear susceptibility ma...

Tuesday 11th February 1107

Aluminum Plasmonics Based Highly Transmissive Polarization-Independent Subtractive Color Filters Exploiting a Nano-patch Array.

Nanophotonic devices enabled by aluminum plasmonics are saliently advantageous in terms of their low cost, outstanding sustainability, and affordable volume-production. We report, for the first time, aluminum plasmonics based highly transmissive polarization-independent subtractive color filters, which are fabricated just with single step electron-beam lithography. The filters feature selective suppression in the transmission spectra, which is realized by combining the propagating and non-propagating surfac...


Strongly Coupled Plasmonic Modes on Macroscopic Areas via Template-Assisted Colloidal Self-Assembly.

We present ensembles of surface-ordered nanoparticle arrangements, which are formed by template-assisted self-assembly of monodisperse, protein-coated gold nanoparticles in wrinkle-templates. Centimeter square areas of highly regular, linear assemblies with tunable line width are fabricated and their extinction cross-sections can be characterized by conventional UV/Vis/NIR spectroscopy. Modeling based on electrodynamic simulations shows a clear signature of strong plasmonic coupling with an interparticle sp...


DNA Translocations through Solid-State Plasmonic Nanopores.

Nanopores enable label-free detection and analysis of single biomolecules. Here, we investigate DNA translocations through a novel type of plasmonic nanopore based on a gold bowtie nanoantenna with a solid-state nanopore at the plasmonic hot spot. Plasmonic excitation of the nanopore is found to influence both the sensor signal (nanopore ionic conductance blockade during DNA translocation) and the process that captures DNA into the nanopore, without affecting the duration time of the translocations. Most st...


Conformal and atomic characterization of ultrathin CdSe platelets with a helical shape.

Currently, ultrathin colloidal CdSe semiconductor nanoplatelets (NPLs) with a uniform thickness that is controllable up to the atomic scale can be prepared. The optical properties of these 2D semiconductor systems are the subject of extensive research. Here, we reveal their natural morphology and atomic arrangement. Using cryo-TEM we show that the shape of rectangular NPLs in solution resembles a helix. Fast incorporation of these NPLs in silica preserves and immobilizes the helical shape, which allowed us ...


Optical Isomer Separation of Single-Chirality Carbon Nanotubes Using Gel Column Chromatography.

We report a gel column chromatography method for easily separating the optical isomers (i.e., left- and right-handed structures) of single-chirality carbon nanotubes. This method uses the difference in the interactions of the two isomers of a chiral single-wall carbon nanotube (SWCNT) with an allyl dextran-based gel, which result from the selective interaction of the chiral moieties of the gel with the isomers. Using this technique, we sorted optical isomers of nine distinct (n, m) single-chirality species ...


Selective Synthesis of Compound Semiconductor/Oxide Composite Nanowires.

Semiconductor/oxide composite nanowires (NWs) were synthesized by molecular beam epitaxial growth and subsequent wet oxidation. Nonselective and selective oxidation conditions applied to the GaAs/AlGaAs core-shell NWs grown on silicon substrates produced GaOx/AlGaOx and GaAs/AlGaOx NWs, respectively. The oxidized amorphous AlGaOx shell produced cathodoluminescence over a wide spectral range encompassing ultraviolet and visible wavelengths, possibly sourced from molecular species related to oxygen. The wire ...


Black Phosphorus Radio-Frequency Transistors.

Few-layer and thin film forms of layered black phosphorus (BP) have recently emerged as a promising material for applications in high performance nanoelectronics and infrared optoelectronics. Layered BP thin films offer a moderate bandgap of around 0.3 eV and high carrier mobility, leading to transistors with decent on-off ratios and high on-state current densities. Here, we demonstrate the gigahertz frequency operation of black phosphorus field-effect transistors for the first time. The BP transistors demo...


Site-controlled VLS Growth of Planar Nanowires: Yield and Mechanism.

The recently emerged selective lateral epitaxy of semiconductor planar nanowires (NWs) via the vapor-liquid-solid (VLS) mechanism has redefined the long-standing symbolic image of VLS NW growth - vertical NWs extending out of the substrate. The in-plane geometry and self-aligned nature make these planar NWs completely compatible with large scale manufacturing of NW-based integrated nanoelectronics. Here we report on the realization of perfectly site-controlled growth of GaAs planar NW arrays with unity yiel...


Quantum confined emission and fluorescence blinking of individual exciton complexes in CdSe nanowires.

One-dimensional semiconductor nanostructures combine electron mobility in length direction with the possibility of tailoring the physical properties by confinement effects in radial direction. Here we show that thin CdSe quantum nanowires exhibit low-temperature fluorescence spectra with a specific universal structure of several sharp lines. The structure strongly resembles the pattern of bulk spectra but show a diameter-dependent shift due to confinement effects. Also the fluorescence shows a pronounced co...


Phonon-mediated mid-infrared photoresponse of graphene.

The photoresponse of graphene at mid-infrared frequencies is of high technological interest and is governed by fundamentally different underlying physics than the photoresponse at visible frequencies, as the energy of the photons and substrate phonons involved have comparable energies. Here we perform a spectrally resolved study of the graphene photoresponse in the mid-infrared by measuring spatially resolved photocurrent over a broad frequency range (1000-1600 cm(-1)). We unveil the different mechanisms th...


Electronic Bandgap and Edge Reconstruction in Phosphorene Materials.

Single-layer black phosphorous (BP), or phosphorene, is a highly-anisotropic two-dimensional elemental material possessing promising semiconductor properties for flexible electronics. However, the direct bandgap of single-layer black phosphorus predicted theoretically has not been directly measured, and the properties of its edges have not been considered in detail. Here we report atomic scale electronic variation related to strain-induced anisotropic deformation of the puckered honeycomb structure of fresh...


Atomically Engineered Metal-Insulator Transition at the TiO2/LaAlO3 Heterointerface.

We demonstrate that the atomic boundary conditions of simple binary oxides can be used to impart dramatic changes of state. By changing the substrate surface termination of LaAlO3 (001) from AlO2 to LaO, the room temperature sheet conductance of anatase TiO2 films are increased by over 3 orders of magnitude, transforming the intrinsic insulating state to a high mobility metallic state, while maintaining excellent optical transparency.


A Nanoscale Piezoelectric Transformer for Low Voltage Transistors.

A novel piezoelectric voltage transformer for low voltage transistors is proposed. Placing a piezoelectric transformer on the gate of a field effect transistor results in the Piezoelectric Transformer Field Effect Transistor, or PT-FET that can switch at significantly lower voltages than a conventional transistor. The piezoelectric transformer operates by using one piezoelectric to squeeze another piezoelectric to generate a higher output voltage than the input voltage. Multiple piezoelectrics can be used t...


Correction to Nonlinear Optical Response in Single Alkaline Niobate Nanowires.


Quantum noise and asymmetric scattering of electrons and holes in graphene.

We present measurements of quantum interference noise in double-gated single layer graphene devices at low temperatures. The noise characteristics show a non-monotonic dependence on carrier density, which is related to the interplay between charge inhomogeneity and different scattering mechanisms. Linearly increasing 1/f noise at low carrier densities coincides with the observation of weak localization, suggesting the importance of short-range disorder in this regime. Using perpendicular and parallel p-n ju...


Measurement of the position-dependent electrophoretic force on DNA in a glass nanocapillary.

The electrophoretic force on a single DNA molecule inside a glass nanocapillary depends on its opening size and varies with the distance along the symmetrical axis. Using optical tweezers and DNA-coated beads, we measured the stalling forces and mapped the position-dependent force profiles acting on DNA inside nanocapillaries of different sizes. We showed that the stalling force is higher in nanocapillaries of smaller diameters, as previously demonstrated for solid-state nanopores. The position-dependent fo...


The interaction range of P-dopants in Si110 nanowires: determining the non-degenerate limit.

It is well-known that the activation energy of dopants in semiconducting nano-materials is higher than in bulk materials owing to dielectric mismatch and quantum confinement. This quenches the number of free charge carriers in nano-materials. While higher doping concentration can compensate this effect, there is no clear criterion on what the doping concentration should be. Using P-doped Si[110] nanowires as the prototypical system, we address this issue by establishing a doping limit by first-principles el...

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