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04:38 EDT 28th July 2017 | BioPortfolio

The US National Library of Medicine and National Institutes of Health manage PubMed.gov which comprises of more than 21 million records, papers, reports for biomedical literature, including MEDLINE, life science and medical journals, articles, reviews, reports and  books.  BioPortfolio aims to publish relevant information on published papers, clinical trials and news associated with users selected topics.

For example view all recent relevant publications on Epigenetics and associated publications and clincial trials.

Showing PubMed Articles 1–25 of 3,500+ from Nano letters

Nanosheet Supported Single-Metal Atom Bifunctional Catalyst for Overall Water Splitting.

Nanosheet supported single-atom catalysts (SACs) can make full use of metal atoms and yet entail high selectivity and activity, while bifunctional catalysts can enable higher performance while lowering the cost than two separated unifunctional catalysts. Supported single-atom bifunctional catalysts are therefore of great economic interest and scientific importance. Here, based on first-principles computations, we report a design of the first single-atom bifunctional eletrocatalyst, namely, isolated nickel a...

Sharpened VO2 phase transition via controlled release of epitaxial strain.

Phase transitions in correlated materials can be manipulated at the nanoscale to yield emergent functional properties, promising new paradigms for nanoelectronics and nanophotonics. Vanadium dioxide (VO2), an archetypal correlated material, exhibits a metal‒insulator transition (MIT) above room temperature. At the thicknesses required for heterostructure applications, such as an optical modulator discussed here, the strain state of VO2 largely determines the MIT dynamics critical to the device performance...

Long-lived direct and indirect interlayer excitons in van der Waals heterostructures.

We report the observation of a doublet structure in the low-temperature photoluminescence of interlayer excitons in heterostructures consisting of monolayer MoSe2 and WSe2. Both peaks exhibit long photoluminescence lifetimes of several ten nanoseconds up to 100 ns verifying the interlayer nature of the excitons. The energy and linewidth of both peaks show unusual temperature and power dependences. While the low-energy peak dominates the spectra at low power and low temperatures, the high-energy peak dominat...

Electron Beam Etching of CaO Crystals Observed Atom by Atom.

With the rapid development of nanoscale structuring technology, the precision in the etching reaches the sub-10 nm scale today. However, with the ongoing development of nanofabrication, the etching mechanisms with atomic precision still have to be understood in detail and improved. Here we observe atom by atom how preferential facets form in CaO crystals that are etched by an electron beam in an in situ high resolution transmission electron microscope (HRTEM). An etching mechanism under electron beam irradi...

Self-Collapse Lithography.

We report a facile, high-throughput soft lithography process that utilizes nanoscale channels formed naturally at the edges of microscale relief features on soft, elastomeric stamps. Upon contact with self-assembled monolayer (SAM) functionalized substrates, the roof of the stamp collapses, resulting in the selective removal of SAM molecules via a chemical lift-off process. With this technique, which we call self-collapse lithography (SCL), sub-30-nm patterns were achieved readily using masters with microsc...

Semi-ordered hierarchical metallic network for fast and large charge-induced strain.

Nanoporous metallic actuators for artificial muscle applications are distinguished by combining the low operating voltage which is otherwise reserved for polymer-based actuators with interesting values of strain amplitude, strength and stiffness that are comparable of those of piezoceramics. We report a nanoporous metal actuator with enhanced strain amplitude and accelerated switching. Our 3D macroscopic metallic muscle has semi-ordered and hierarchical nanoporous structure, in which µm-sized tubes align p...

Revealing the electrochemical charging mechanism of nano-sized Li2S by in-situ and operando X-ray absorption spectroscopy.

Lithium sulfide (Li2S) is a promising cathode material for lithium/sulfur (Li/S) cells due to its high theoretical specific capacity (1166 mAh g(-1)) and capability to pair with non-metallic lithium anodes to avoid potential safety issues. However, when used as the cathode a high charging voltage (~ 4 V vs. Li+/Li) is always necessary to activate Li2S in the first charge process, and the voltage profile becomes similar to that of a common sulfur electrode in the following charge processes. In this report, w...

Dynamically reconfigurable metadevice employing nanostructured phase change materials.

Mastering dynamic free-space spectral control and modulation in the near-infrared and optical regimes remains a challenging task that is hindered by the available functional materials at high frequencies. Here, we realize an efficient metadevice capable of spectral control by minimizing the thermal mass of a vanadium dioxide phase-change material (PCM) and placing the PCM at the feed gap of a bow-tie field antenna. The device has an experimentally measured tuning range up to 360 nm in the NIR and a modulati...

Large-scale statistics for threshold optimization of optically pumped nanowire lasers.

Single nanowire lasers based on bottom-up III-V materials have been shown to exhibit room-temperature near-infrared lasing, making them highly promising for use as nanoscale, silicon-integrable and coherent light sources. While lasing behavior is reproducible, small variations in growth conditions across a substrate arising from the use of bottom-up growth techniques can introduce inter-wire disorder, either through geometric or material inhomogeneity. Nanolasers critically depend on both high material qual...

Remote single-molecule switching: Identification and nano-engineering of hot electron-induced tautomerization.

Molecular electronics where single molecules perform basic functionalities of digital circuits is a fascinating concept that one day may augment or even replace nowadays semiconductor technologies. The tautomerization of molecules, i.e., the bistable functional position of hydrogen protons within an organic frame, has recently been intensively discussed as a potential avenue towards nano-scale switches. It has been shown that tautomerization can be triggered locally or non-locally, i.e. by a scanning tunnel...

Quantum transport and subband structure of modulation-doped GaAs/AlAs core-superlattice nanowires.

Modulation-doped III-V semiconductor nanowire (NW) heterostructures have recently emerged as promising candidates to host high-mobility electron channels for future high-frequency, low-energy transistor technologies. The one-dimensional geometry of NWs also makes them attractive for studying quantum confinement effects. Here, we report correlated investigations into the discrete electronic sub-band structure of confined electrons in the channel of Si delta-doped GaAs/AlAs core-superlattice NW heterostructur...

Evidence for ultra-low-energy vibrations in large organic molecules.

The quantum efficiency or the rate of conversion of incident photon to free electron in photosynthesis is known to be extremely high. It has long been thought that the origin of this efficiency are molecular vibrations leading to a very fast separation of electrons and holes within the involved molecules. However, molecular vibrations are commonly in the range above 100 meV, which is too high for excitations in an ambient environment. Here, we analyze experimental spectra of single organic molecules on meta...

Unraveling the high Voc and high performance of integrated perovskite/organic bulk-heterojunction solar cells.

We have demonstrated high performance integrated perovskite/bulk-heterojunction (BHJ) solar cells due to the low carrier recombination velocity, high open circuit voltage (Voc) and increased light absorption ability in near-infrared (NIR) region of integrated devices. In particular, we find that the Voc of the integrated devices is dominated by (or pinned to) the perovskite cells, not the OPV cells. A Quasi-Fermi Level Pinning Model was proposed to understand the working mechanism and the origin of the Voc ...

Exploring Ultimate Water Capillary Evaporation in Nanoscale Conduits.

Capillary evaporation in nanoscale conduits is an efficient heat/mass transfer strategy that has been widely utilized by both nature and mankind. Despite its broad impact, the ultimate transport limits of capillary evaporation in nanoscale conduits, governed by the evaporation/condensation kinetics at the liquid-vapor interface, have remained poorly understood. Here we report experimental study of the kinetic limits of water capillary evaporation in 2-D nanochannels using a novel hybrid channel design. Our ...

Spin Hall effect and Weak Antilocalization in Graphene/Transition Metal Dichalcogenide Heterostructures.

We report on a theoretical study of the spin Hall Effect (SHE) and weak antilocalization (WAL) in graphene/transition metal dichalcogenide (TMDC) heterostructures, computed through efficient real-space quantum transport methods, and using realistic tight-binding models parametrized from ab initio calculations. The graphene/WS2 system is found to maximize spin proximity effects compared to graphene on MoS2, WSe2, or MoSe2, with a crucial role played by disorder, given the disappearance of SHE signals in the ...

Photoluminescence enhancement through symmetry breaking induced by defects in nanocrystals.

We present a theoretical model for the effect of symmetry breaking introduced by the doping of semiconductor nanocrystals with Coulomb impurities. The presence of a Coulomb center breaks the nanocrystal symmetry and affects its optical properties through mixing of the hole spin and parity sublevels, breaking the selection rules responsible for the exciton dark state in undoped nanocrystals. After reviewing the effects on the exciton fine structure and optical selection rules using symmetry theory, we presen...

Plastic Deformation through Dislocation Saturation in Ultra-Small Pt Nanocrystals and its In Situ Atomistic Mechanisms.

The atomic-scale deformation dynamic behaviors of Pt nanocrystals with size of ~18 nm were in situ investigated using our homemade device in a high resolution transmission electron microscope. It was discovered that the plastic deformation of the nanosized single crystalline Pt commenced with dislocation "appreciation" first, and then followed by a dislocation "saturation" phenomenon. The magnitude of strain plays a key role on dislocation behaviors. At the early to medium stage of deformation, the plastic ...

Balancing Passive and Active Targeting to Different Tumor Compartments Using Riboflavin-functionalized Polymeric Nanocarriers.

Riboflavin Transporters (RFTs) and the Riboflavin Carrier Protein (RCP) are highly upregulated in many tumor cells, tumor stem cells and tumor neovasculature, which makes them attractive targets for nanomedicines. Addressing cells in different tumor compartments requires drug carriers, which are not only able to accumulate via the EPR effect, but also to extravasate, target specific cell populations, and get internalized by cells. Reasoning that antibodies are among the most efficient targeting systems deve...

Mid-infrared plasmonic circular dichroism generated by graphene nanodisk assemblies.

It is very interesting to bring plasmonic circular dichroism spectroscopy to the mid-infrared spectral interval and there are two reasons for this. This spectral interval is very important for thermal bio-imaging and, simultaneously, this spectral range includes vibrational lines of many chiral biomolecules. Here we demonstrate that graphene plasmons indeed offer such opportunity. In particular, we show that chiral graphene assemblies consisting of a few graphene nanodisks can generate strong circular dichr...

Graphene enhanced Brillouin optomechanical microresonator for ultra-sensitive gas detection.

Chemical sensing is one of the most important applications of nanoscience, whose ultimate aim is to seek higher sensitivity. In recent years, graphene with intriguing quantum properties has spurred dramatic advances ranging from materials science to optoelectronics and mechanics, showing its potential to realize individual molecule solid-state sensors. However, for optical sensing, the single atom thickness of graphene greatly limits the light-graphene interaction, bottlenecking their performances. Here we ...

Tuning Li-ion diffusion in α-LiMn1-xFexPO4 nanocrystals by antisite defects and embedded β-phase for advanced Li-ion batteries.

Olivine-structured LiMn1-xFexPO4 has become a promising candidate for cathode materials owing to its higher working voltage of 4.1V, and thus larger energy density than that of LiFePO4, which has been used for electric vehicles batteries with the advantage of high safety but disadvantage of low energy density due to its lower working voltage of 3.4V. One drawback of LiMn1-xFexPO4 electrode is its relatively low electronic and Li-ionic conductivity with Li-ion 1D diffusion. Herein, olivine-structured α-LiMn...

ZnO Nanocrystal Networks Near the Insulator-Metal Transition: Tuning Contact Radius and Electron Density with Intense Pulsed Light.

Networks of ligand-free semiconductor nanocrystals (NCs) offer a valuable combination of high carrier mobility and optoelectronic properties tunable via quantum confinement. In principle, maximizing carrier mobility entails crossing the insulator-metal transition (IMT), where carriers become delocalized. A recent theoretical study predicted that this transition occurs at nρ(3) ≈ 0.3, where n is the carrier density and ρ is the interparticle contact radius. In this work, we satisfy this criterion in netw...

Suppressing nucleation in metalorganic chemical vapor deposition of MoS2 monolayers by alkali metal halides.

Towards large-area deposition of MoS2 layers, we employ metal-organic precursors of Mo and S for a facile and reproducible van der Waals epitaxy on c-plane sapphire. Exposing c-sapphire substrates to alkali metal halide salts such as KI or NaCl together with the Mo precursor prior to the start of the growth process, results in increasing the lateral dimensions of single crystalline domains by more than two orders of magnitude. The MoS2 grown this way exhibits high crystallinity and optoelectronic quality co...

Direct Observation of 'Pac-Man' coarsening.

We report direct observation of a 'Pac-Man' like coarsening mechanism of a self-supporting thin film of nickel oxide. The ultra-thin film has an intrinsic morphological instability due to surface stress leading to the development of local thicker regions at step edges. Density functional theory calculations and continuum modelling of the elastic instability support the model for the process.

Robust molecular anchoring to graphene electrodes.

Recent advances in the engineering of pico-scale gaps between electroburnt graphene electrodes provide new opportunities for studying electron transport through electrostatically-gated single molecules. But first we need to understand and develop strategies for anchoring single molecules to such electrodes. Here, for the first time, we present a systematic theoretical study of transport properties using four different modes of anchoring zinc-porphyrin monomer, dimer and trimer molecular wires to graphene el...


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