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PubMed Journal Database | Nano letters RSS

07:18 EDT 26th May 2019 | BioPortfolio

The US National Library of Medicine and National Institutes of Health manage PubMed.gov which comprises of more than 29 million records, papers, reports for biomedical literature, including MEDLINE, life science and medical journals, articles, reviews, reports and  books.

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Showing PubMed Articles 1–25 of 1,700+ from Nano letters

Proximity Induced Superconductivity in CdTe-HgTe Core-Shell Nanowires.

In this letter we report on proximity superconductivity induced in CdTe-HgTe core-shell nanowires, a quasi-one-dimensional heterostructure of the topological insulator HgTe. We demonstrate a Josephson supercurrent in our nanowires contacted with superconducting Al leads. The observation of a sizable IR product, a positive excess current and multiple Andreev reflections up to fourth order further indicate a high interface quality of the junctions.

Probing exfoliated graphene layers and their lithiation with micro-focused X-rays.

X-ray diffraction is measured on individual bilayer and multilayer graphene single-crystals and combined with electrochemically induced lithium intercalation. In-plane Bragg peaks are observed by grazing incidence diffraction. Focusing the incident beam down to an area of about 10 µm x 10 µm, individual fakes are probed by specular X-ray reflectivity. By deploying a recursive Parratt algorithm to model the experimental data, we gain access to characteristic crystallographic parameters of the samples. Nota...

Tailoring of Interfacial Band Offsets by an Atomically Thin Polar Insulating Layer to Enhance the Water-Splitting Performance of Oxide Heterojunction Photoanodes.

An important factor in the performance of photoelectrochemical water splitting is the band edge alignment of the photoelectrodes for efficient transport and transfer of photogenerated carriers. Many studies for improving charge transfer ability between the electrode and the electrolyte have been reported, while research to improve charge transfer at the hetero interface of the photoactive semiconductor and the conducting substrate is relatively lacking. Here, we demonstrate that the water-splitting performa...

Hot-electron mediated ion diffusion in semiconductors for ion-beam nanostructuring.

Ion-beam based techniques are widely utilized to synthesize, modify, and characterize materials at the nano-scale, with applications from semiconductor industry to medicine. Interactions of the beam with the target are fundamentally interesting as they trigger multi-length and time-scale processes that need to be quantitatively understood to achieve nano-scale precision. Here we demonstrate for magnesium oxide, as a testbed semiconductor material, that in a kinetic-energy regime in which electronic effects ...

Nanostructural Surfaces with Different Elastic ModulI Regulate the Immune Response by Stretching Macrophages.

A proper immune response is key for the successful implantation of biomaterials, and designing and fabricating biomaterials to regulate immune responses is the future trend. In this work, three different nanostructures were constructed on the surface of titanium using a hydrothermal method, and through a series of in vitro and in vivo experiments, we found that the aspect ratio of nanostructures can affect the elastic modulus of a material surface and further regulate immune cell behaviors. This work demons...

Electrical Control of Lifetime-Limited Quantum Emitters Using 2D Materials.

Solid-state quantum emitters are a mainstay of quantum nanophotonics as integrated single-photon sources (SPS) and optical nanoprobes. Integrating such emitters with active nanophotonic elements is desirable in order to attain efficient control of their optical properties, but it typically degrades the photostability of the emitter itself. Here, we demonstrate a tunable hybrid device that integrates state of the art lifetime-limited single emitters (line width ∼40 MHz) and 2D materials at subwavelength se...

Crossover between Photochemical and Photothermal Oxidations of Atomically Thin Magnetic Semiconductor CrPS4.

Many two-dimensional (2D) semiconductors represented by transition metal dichalcogenides have tunable optical bandgaps in the visible or near IR-range standing as a promising candidate for optoelectronic devices. Despite this potential, however, their photoreactions are not well understood or controversial in the mechanistic details. In this work, we report a unique thickness-dependent photoreaction sensitivity and a switchover between two competing reaction mechanisms in atomically thin chromium thiophosph...

Advanced One- and Two-Dimensional Mesh Designs for Injectable Electronics.

The unique structure and mechanical properties of syringe-injectable mesh electronics have enabled seamless tissue integration and stable chronic recording of the activities of the same neurons on a year-scale. Here, we report studies of a series of structural and mechanical mesh electronics design variations that allow injection using needles at least four-fold smaller than previously reported to minimize the footprint during injection of the electronics in soft matter and tissue. Characterization of new u...

Heterogeneous Photon Recycling and Charge Diffusion Enhance Charge Transport in Quasi-2D Lead-Halide Perovskite Films.

The addition of large hydrophobic cations to lead halide perovskites has significantly enhanced the environmental stability of photovoltaic cells based on these materials. However, the associated formation of two-dimensional structures inside the material can lead to dielectric confinement, higher exciton binding energies, wider bandgaps and limited charge-carrier mobilities. Here we show that such effects are not detrimental to the charge transport, for carefully processed films comprising a self-assembled...

Near-Field Manipulation in a Scanning Tunneling Microscope Junction with Plasmonic Fabry-Pérot Tips.

Near-field manipulation in metallic nanocavities can provide various applications in nanoscale science and technology. In particular, gap plasmon in scanning tunneling microscope (STM) junctions is of key interest to nanoscale imaging and spectroscopy. Here we report that plasmonic properties of an STM junction can be manipulated by nanofabrication of Au tips using focused ion beam (FIB) milling. An exemplary Fabry-Pérot like resonator of surface plasmons is demonstrated by producing a single groove on a s...

Metal@SiO2 Core-Shells with Self-Arrested Migrating Core.

Developing easy and customizable strategies for the directional structure modulation of multi-component nanosystems to influence and optimize their properties, are paramount but challenging task in nanoscience. Here, we demonstrate highly controlled eccentric off-center positioning of metal-core in metal@silica core-shells by utilizing an in situ generated biphasic silica-based intraparticle solid-solid interface. In the synthetic strategy, by including Ca2+-ions in silica-shell and successive oxidative and...

Spatial and Temporal Nanoscale Plasmonic Heating Quantified by Thermoreflectance.

The field of thermoplasmonics has thrived in the past decades since it uniquely provides remotely-controllable nanometer-scale heat sources that have augmented numerous technologies. Despite the extensive studies on steady-state plasmonic heating, the dynamic behavior of the plasmonic heaters in the nanosecond regime has remained largely unexplored, yet such timescale is indeed essential for a broad range of applications such as photocatalysis, optical modulators and detectors. Here, we use two distinct tec...

Spin States Protected from Intrinsic Electron-Phonon-Coupling Reaching 100 ns Lifetime at Room Temperature in MoSe.

We present time-resolved Kerr rotation measurements, showing spin lifetimes of over 100 ns at room temperature in monolayer MoSe. These long lifetimes are accompanied by an intriguing temperature dependence of the Kerr amplitude, which increases with temperature up to 50 K and then abruptly switches sign. Using ab initio simulations we explain the latter behavior in terms of the intrinsic electron-phonon coupling and the activation of transitions to secondary valleys. The phonon-assisted scattering of the p...

Room Temperature Magnetic Order in Air-Stable Ultra-Thin Iron Oxide.

Manual assembly of atomically thin materials into heterostructures with desirable electronic properties is an approach that holds great promise. Despite the rapid expansion of the family of ultra-thin materials, stackable and stable ferro/ferri magnets that are functional at room temperature are still out of reach. We report the growth of air-stable, transferable ultra-thin iron oxide crystals that exhibit magnetic order at room temperature. These crystals require no passivation and can be prepared by scala...

Ion write micro-thermotics: programing thermal metamaterials at the microscale.

Considerable advances in manipulating heat flow in solids have been made through the innovation of artificial thermal structures such as thermal diodes, camouflages and cloaks. Such thermal devices can be readily constructed only at the macro-, centimeter- scale by mechanically assembling different materials with distinct values of thermal conductivity. Rapidly growing needs in areas such as thermal management of microelectronics require these concepts to be extended to and explored at the microscale. We de...

Field effect transistor and photo transistor of narrow band gap nanocrystal arrays using ionic glasses.

Gating of nanocrystal films is currently driven by two approaches: either the use of a dielectric such as SiO2 or the use of electrolyte. SiO2 allows fast bias sweeping over a broad range of temperatures but requires a large operating bias. Electrolyte, thanks to a large capacitance, leads to significantly reduce operating bias but is limited to slow speed and quasi room temperature operation. None of these operating conditions are optimal for narrow band gap nanocrystal-based phototransistors for which the...

Fluidic Force Microscopy Demonstrates That Homophilic Adhesion by Candida albicans Als Proteins Is Mediated by Amyloid Bonds between Cells.

The fungal pathogen Candida albicans frequently forms drug-resistant biofilms in hospital settings and in chronic disease patients. Cell adhesion and biofilm formation involve a family of cell surface Als (agglutinin-like sequence) proteins. It is now well documented that amyloid-like clusters of laterally arranged Als proteins activate cell-cell adhesion under mechanical stress, but whether amyloid-like bonds form between aggregating cells is not known. To address this issue, we measure the forces driving ...

Ferromagnetic anomalous Hall effect in Cr-doped BiSe thin films via surface-state engineering.

The anomalous Hall effect (AHE) is a non-linear Hall effect appearing in magnetic conductors, boosted by internal magnetism beyond what is expected from the ordinary Hall effect. With the recent discovery of the quantized version of the AHE, the quantum anomalous Hall effect (QAHE), in Cr- or V-doped topological insulator (TI) (Sb,Bi)Te thin films, the AHE in magnetic TIs has been attracting significant interest. However, one of the puzzles in this system has been that while Cr- or V-doped (Sb,Bi)Te and V-d...

Nano-mosaic of Topological Dirac States on the Surface of Pb5Bi24Se41 Observed by Nano-ARPES.

We have performed scanning angle-resolved photoemission spectroscopy with a nanometer-sized beam spot (nano-ARPES) on the cleaved surface of Pb5Bi24Se41, which is a member of the (PbSe)5(Bi2Se3)3m homologous series (PSBS) with m = 4 consisting of alternate stacking of the topologically-trivial insulator PbSe bilayer and four quintuple layers (QLs) of the topological insulator Bi2Se3. This allows us to visualize a mosaic of topological Dirac states at a nanometer scale coming from the variable thickness of t...

Phonon coupling between a nanomechanical resonator and a quantum fluid.

Owing to their extraordinary sensitivity to external forces, nanomechanical systems have become an important tool for studying mesoscopic physics and realizing hybrid quantum systems. While nanomechanics has been widely applied in solid-state systems, its use in liquid receives less attention. There it finds unique applications such as biosensing, rheological sensing, and studying both classical and quantum fluid dynamics in unexplored regimes. In this work, we demonstrate efficient coupling of a nano-optom...

Peptide-Assisted 2-D Assembly toward Free-Floating Ultrathin Platinum Nanoplates as Effective Electrocatalysts.

We demonstrate the 2-D anisotropic formation of ultrathin free-floating Pt nanoplates from the assembly of small nanocrystals using T7 peptide (Ac-TLTTLTN-CONH2). As formed nanoplates are rich in grain boundaries that can promote their catalytic activities. Furthermore, we demonstrate that a minor amount of Pd atoms can selectively deposit on and stabilize the grain boundaries, which leads to enhanced structure stability. The Pd-enhanced Pt polycrystal nanoplates show great oxygen reduction reaction (ORR) a...

The Role of Polarity in Non-Planar Semiconductor Nanostructures.

The lack of mirror symmetry in binary semiconductor compounds turns them into polar materials, where two opposite orientations of the same crystallographic direction are possible. Interestingly, their physical properties (e.g.: electronic or photonic) and morphological features (e.g.: shape, growth direction, etc.) also strongly depend on the polarity. It has been observed that nanoscale materials tend to grow with a specific polarity, which can eventually be reversed for very specific growth conditions. In...

Kinetics of Au-Ga droplet mediated decomposition of GaAs nanowires.

Particle-assisted III-V semiconductor nanowire growth and applications thereof have been studied extensively. However, the stability of nanowire in contact with the particle as well as the particle chemical composition as a function of temperature remain largely unknown. In this work we use in-situ transmission electron microscopy to investigate the interface between a Au-Ga particle and the top facet of an 1 1 1-oriented GaAs nanowire grown via vapor-liquid-solid process. We observed a thermally activated ...

Plasmon Excited Ultrahot Carriers and Negative Differential Photoresponse in a Vertical Graphene van der Waals Heterostructure.

Photogenerated nonequilibrium hot carriers play a key role in graphene's intriguing optoelectronic properties. Compared to conventional photoexcitation, plasmon excitation can be engineered to enhance and control the generation and dynamics of hot carriers. Here, we report an unusual negative differential photoresponse of plasmon-induced "ultrahot" electrons in a graphene-boron nitride-graphene tunneling junction. We demonstrate nanocrescent gold plasmonic nanostructures that substantially enhance the absor...

Real space observation of electronic coupling between self-assembled quantum dots.

The control of quantum coupling between nano-objects is essential to quantum technologies. Confined nanostructures, such as cavities, resonators or quantum dots, are designed to enhance interactions between electrons, photons or phonons, giving rise to new properties on which devices are developed. The nature and strength of these interactions are often measured indirectly on an assembly of dissimilar objects. Here, we adopt an innovative point of view by directly mapping the coupling of single nanostructur...


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