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A two-dimensional binary driven disk system embedded by impermeable tilted plates is investigated through nonequilibrium computer simulations. It is well known that a binary disk system in which two particle species are driven in opposite directions exhibits jammed, phase separated, disordered, and laning states. The presence of tilted plates can not only advance the formation of laning phase, but also effectively stabilize laning phase by suppressing massively drifting behavior perpendicular to the driving force. The lane width distribution can be controlled easily by the interplate distance. The collective behavior of driven particles in laning phase is guided by the funnel-shaped confinements constituted by the neighboring tilted plates. Our results provide the important clues for investigating the mechanism of laning formation in driven system. [ABSTRACT FROM AUTHOR]

While classic reforming processes rely on heat and chemical equilibrium, plasma-based reforming processes possess the ability to induce non-equilibrium and reactive chemistry at low temperatures using high energy electrons. To better understand the distinctive roles of both electron-induced chemistry and thermochemistry during plasma-assisted fuel reforming, we previously developed a temperature-controlled dielectric barrier discharge (DBD) reactor, which controlled the gas temperature and the electron temperature independently. Here, we investigate plasma-assisted steam reforming of methane using the temperature-controlled DBD reactor and electron-kinetics calculations. We investigated the individual effects of the determining factors for electron-induced chemistry (i.e. reduced electric field intensity and discharge power) and for thermochemistry (i.e. background gas temperature) by varying the discharge power, gas temperature, and pressure inside the reactor. As a result, we found that both the electron-induced chemistry and thermochemistry governed the reactant conversions. Thermochemistry positively affected the methane conversion in particular, but negatively affected the water conversion as the gas temperature increased. The electron-induced chemistry weakly affected the product distribution, while the background temperature (thermochemistry) strongly influenced the product selectivity and composition by altering the chemical pathways involving the plasma-generated reactive species at the given temperature. [ABSTRACT FROM AUTHOR]

The solubility and bubble formation of hydrogen (H) in tungsten (W) are crucial factors for the application of W as a plasma-facing component under a fusion environment, but the data and mechanism are presently scattered, indicating some important factors might be neglected. High-energy neutron-irradiated W inevitably causes a local strain, which may change the solubility of H in W. Here, we performed first-principles calculations to predict the H solution behaviors under isotropic strain combined with temperature effect in W and found that the H solubility in interstitial lattice can be promoted/impeded by isotropic tensile/compressive strain over the temperature range 300–1800 K. The calculated H solubility presents good agreement with the experiment. Together, our previous results of anisotropic strain, except for isotropic compression, both isotropic tension and anisotropic tension/compression enhance H solution so as to reveal an important physical implication for H accumulation and bubble formation in W: strain can enhance H solubility, resulting in the preliminary nucleation of H bubble that further causes the local strain of W lattice around H bubble, which in turn improves the H solubility at the strained region that promotes continuous growth of the H bubble via a chain-reaction effect in W. This result can also interpret the H bubble formation even if no radiation damage is produced in W exposed to low-energy H plasma. [ABSTRACT FROM AUTHOR]

We present a new method for achieving chemical reactions induced by plasmas with liquids—an in-liquid arc plasma jet system—designed to have a few advantages over the existing methods. High-speed imaging and optical emission spectroscopy were adopted to highlight the physical aspects of the in-liquid arc plasma jet system, and the feasibility of the system was investigated in a wastewater treatment case with phenol as the model contaminant. We found that the specific energy input is a reasonable parameter by which to characterize the overall process. The phenol removal reaction could be modeled as a pseudo-first-order reaction, and the reaction constant became smaller as the phenol concentration increased. However, complete decomposition of the phenol into water and carbon dioxide required very high energy because the final intermediate, oxalic acid, is relatively stable. Detailed chemical and physical analyses, including byproducts, ions, solution acidity, and conductivity, were conducted to evaluate this new method for use in the appropriate applications. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are single stranded endogenous molecules composed of only 18–24 nucleotides which are critical for gene expression regulating the translation of messenger RNAs. Conventional methods based on enzyme-assisted nucleic acid amplification techniques have many problems, such as easy contamination, high cost, susceptibility to false amplification, and tendency to have sequence mismatches. Here we report a rapid, ratiometric, enzyme-free, sensitive, and highly selective single-step miRNA detection using three-way junction assembled (or self-assembled) FRET probes. The developed strategy can be operated within the linear range from subnanomolar to hundred nanomolar concentrations of miRNAs. In comparison with the traditional approaches, our method showed high sensitivity for the miRNA detection and extreme selectivity for the efficient discrimination of single-base mismatches. The results reveal that the strategy paved a new avenue for the design of novel highly specific probes applicable in diagnostics and potentially in microscopic imaging of miRNAs in real biological environments. [ABSTRACT FROM AUTHOR]

We have carried out systematic first-principles total energy and vibration spectrum calculations to investigate the finite-temperature H dissolution behaviors in tungsten and molybdenum, which are considered promising candidates for the first wall in nuclear fusion reactors. The temperature effect is considered by the lattice expansion and phonon vibration. We demonstrate that the H Gibbs energy of formation in both tetrahedral and octahedral interstitial positions depends strongly on the temperature. The H Gibbs energy of formation under one atmosphere of pressure increases significantly with increasing temperature. The phonon vibration contribution plays a decisive role in the H Gibbs energy of formation with the increasing temperature. Using the predicted H Gibbs energy of formation, our calculated H concentrations in both metals are about one or two orders of magnitude lower than the experimental data at temperature range from 900 to 2400 K. Such a discrepancy can be reasonably explained by the defect-capturing effect. [ABSTRACT FROM AUTHOR]

Nanowires, nanofibers and nanotubes have been widely used as the building blocks in micro/nano-electromechanical systems, energy harvesting or storage devices, and small-scaled measurement equipment. We report that the surface effects of these nanobeams have a great impact on their deflection and internal forces. A simply supported nanobeam is taken as an example. For the displacement and shear force of the nanobeam, its dangerous sections are different from those predicted by the conventional beam theory, but for the bending moment, the dangerous section is the same. Moreover, the values of these three quantities for the nanobeam are all distinct from those calculated from the conventional beam model. These analyses shed new light on the stiffness and strength check of nanobeams, which are beneficial to engineer new-types of nano-materials and nano-devices. [ABSTRACT FROM AUTHOR]

Since carbon-based structures of various dimensions, including one-dimensional (1D) carbon nanotubes, two-dimensional (2D) graphene and three-dimensional (3D) carbon foams, have attracted significant attention as microwave absorption fillers, we present an exceptional hetero-junction filler with a 1D–2D–1D feature, achieved by manipulating 2D graphene into 1D carbon fibers in the fiber-extruding process under the electric field. The as-fabricated 1D–2D–1D structural fillers exhibited much-improved dielectric properties and promoted microwave absorption performance in their composites, which is linked to the establishment of enhanced polarization capability, the generation of increased electric loss pathway and the creation of more favorable electromagnetic energy consumption conditions. The results suggest that employing 2D graphene in the 1D–2D–1D nanostructures played the critical role in tuning the electromagnetic response ability, because of its intrinsic electric advantages and dimensional features. To broaden the effective absorption bandwidth, periodic pattern-absorbing structures were designed, which showed combined absorption advantages for various thicknesses. Our strategy for fabricating 1D–2D–1D structural fillers illuminates a universal approach for manipulating dimensions and structures in the nanotechnology. [ABSTRACT FROM AUTHOR]

Since manipulating electromagnetic waves with electromagnetic active materials for environmental and electric engineering is a significant task, here a novel prototype is reported by introducing reduced graphene oxide (RGO) interfaces in carbon fiber (CF) networks for a hierarchical carbon fiber/reduced graphene oxide/nickel (CF-RGO-Ni) composite textile. Upon charaterizations of the microscopic morphologies, electrical and magnetic properties, the presence of three-dimensional RGO interfaces and bifunctional nickel nanoparticles substantially influences the related physical properties in the resulting hierarchical composite textiles. Eletromagnetic interference (EMI) shielding performance suggests that the hierarchical composite textiles hold a strong shielding effectiveness greater than 61 dB, showing greater advantages than conventional polymeric and foamy shielding composites. As a polymer-free lightweight structure, flexible CF-RGO-Ni composites of all electromagnetic active components offer unique understanding of the multi-scale and multiple mechanisms in electromagnetic energy consumption. Such a novel prototype of shielding structures along with convenient technology highlight a strategy to achieve high-performance EMI shielding, coupled with a universal approach for preparing advanced lightweight composites with graphene interfaces. [ABSTRACT FROM AUTHOR]

We studied the energetic behaviors of interstitial and substitution carbon (C)/nitrogen (N) impurities as well as their interactions with the vacancy in vanadium by first-principles simulations. Both C and N impurities prefer the octahedral site (O-site). N exhibits a lower formation energy than C. Due to the hybridization between vanadium-d and N/C-p, the N-p states are located at the energy from −6.00 eV to −5.00 eV, which is much deeper than that from −5.00 eV to –3.00 eV for the C-p states. Two impurities in bulk vanadium, C–C, C–N, and N–N can be paired up at the two neighboring O-sites along the 〈111〉 direction and the binding energies of the pairs are 0.227 eV, 0.162 eV, and 0.201 eV, respectively. Further, we find that both C and N do not prefer to stay at the vacancy center and its vicinity, but occupy the O-site off the vacancy in the interstitial lattice in vanadium. The possible physical mechanism is that C/N in the O-site tends to form a carbide/nitride-like structure with its neighboring vanadium atoms, leading to the formation of the strong C/N–vanadium bonding containing a covalent component. [ABSTRACT FROM AUTHOR]

As an intermedia between cold and thermal plasmas, warm plasma generated by gliding arc (GA) discharge possesses high conversions and high energy efficiencies for CO2 conversion. However, there is little understanding for the arc characteristics in CO2-based atmosphere and reaction mechanism of CO2 in GA plasma from experimental approach. For this purpose, a magnetically driven GA plasma with a constant length of arc is designed to study GA characteristics and reaction mechanism by changing H2/CO2 molar ratio (from pure CO2 to pure H2). In the entire range of H2/CO2 ratio, the arc channel shows a glow-like feature. The plasma parameters are arc temperature of 2200–3600 K, electron density of ~1.6  ×  1014 cm−3 and electron temperature of ~3 eV. From pure CO2 to pure H2, arc diameter decreases from 1.3 to 0.6 mm, whereas rotational frequency increases from 20 to 64 Hz. Based upon the optical emission spectra of CO, OH, H and O species, chemluminescence spectra of CO and O recombination and CO production rate detected online by gas chromatographs, the reaction mechanism at low and high H2/CO2 molar ratios is disclosed. [ABSTRACT FROM AUTHOR]

Phonon sidebands in the electrolumiescence (EL) spectra of InGaN/GaN multiple quantum well blue light emitting diodes are investigated. S-shaped injection current dependence of the energy spacing (ES) between the zero-phonon and first-order phonon-assisted luminescence lines is observed in a temperature range of 100–150 K. The S-shape is suppressed with increasing temperature from 100 to 150 K, and vanishes at temperature above 200 K. The S-shaped injection dependence of ES at low temperatures could be explained by the three stages of carrier dynamics related to localization states: (i) carrier relaxation from shallow into deep localization states, (ii) band filling of shallow and deep localization states, and (iii) carrier overflow from deep to shallow localization states and to higher energy states. The three stages show strong temperature dependence. It is proposed that the fast change of the carrier lifetime with temperature is responsible for the suppression of S-shaped feature. The proposed mechanisms reveal carrier recombination dynamics in the EL of InGaN/GaN MQWs at various injection current densities and temperatures. [ABSTRACT FROM AUTHOR]

InGaN-based green light-emitting diodes (LEDs) with different green quantum well numbers grown on Si (111) substrates by metal organic chemical vapor deposition are investigated. It is observed that V-shaped pits appear in the AFM images with the green quantum well number increasing from 5 to 9, and results in larger reverse-bias leakage current. Meanwhile, in the case of the sample with the number from 5 to 7 then to 9, the external quantum efficiency increases firstly, and then decreases. These phenomena may be related to the size of V-shaped pits in the active area and the distribution of electrons and holes in the active area caused by V-shaped pits. The optimal number of green quantum wells is determined to be 7. [ABSTRACT FROM AUTHOR]

A blue emission originated from InGaN/GaN superlattice (SL) interlayer is observed in the yellow LEDs with V-pits embedded in the quantum wells (QWs), revealing that sufficient holes have penetrated through the QWs into SLs far away from the p-type layer. In the V-pits embedded LEDs, hole transport has two paths: via the flat c-plane region or via the sidewalls of V-pits. It is proved that the holes in SLs are injected from the sidewalls of V-pits, and the transportation process is significantly affected by working temperature, current density, and the size of V-pits. Four motion possibilities are discussed when the holes flow via the sidewalls. All these may contribute to a better understanding of hole transport and device design. [ABSTRACT FROM AUTHOR]

First-principle calculations reveal that the configuration system of hexagonal boron nitride (h-BN) monolayer with triangular vacancy can induce obvious magnetism, contrary to that of the nonmagnetic pristine boron nitride monolayer. Interestingly, the h-BN with boron atom vacancy (VB-BN) displays metallic behavior with a total magnetic moment being 0.46μB per cell, while the h-BN with nitrogen atom vacancy (VN-BN) presents a half-metallic characteristic with a total magnetic moment being 1.0μB per cell. Remarkably, piezoelectric stress coefficient e11 of the VN-BN is about 1.5 times larger than that of pristine h-BN. Furthermore, piezoelectric strain coefficient d11 (12.42 pm/V) of the VN-BN is 20 times larger than that of pristine h-BN and also one order of magnitude larger than the value for the h-MoS2 monolayer, which is mainly due to the spin-down electronic state in the VN-BN system. Our study demonstrates that the nitrogen atom vacancies can be an efficient route to tailoring the magnetic and piezoelectric properties of h-BN monolayer, which have promising performances for potential applications in nano-electromechanical systems (NEMS) and nanoscale electronics devices. [ABSTRACT FROM AUTHOR]

The temperature-induced complex refractive index (CRI) effect of graphene is demonstrated theoretically and experimentally based on a graphene coated in-fiber MZI (Mach–Zehnder interferometer). The relationships between real and imaginary parts of the graphene CRI and temperature are obtained through investigating the dip wavelength and intensity of the MZI interference spectrum changing with temperature, respectively. The temperature effect of CRI of the graphene is also analyzed theoretically. Both experimental and theoretical studies show that the real part and imaginary part of the CRI nonlinearly decrease and increase with temperature increasing, respectively. This graphene-coated in-fiber MZI structure also possesses the advantages of easy fabrication, miniaturization, low cost and robustness. It has potential applications in nanomaterial-based optic devices for communication and sensing. [ABSTRACT FROM AUTHOR]

The low temperature phase transformation in the Cu2ZnSnS4 (CZTS) films was investigated by laser annealing and low temperature thermal annealing. The Raman measurements show that a-high-power laser annealing could cause a red shift of the Raman scattering peaks of the kesterite (KS) structure and promotes the formation of the partially disordered kesterite (PD-KS) structure in the CZTS films, and the low-temperature thermal annealing only shifts the Raman scattering peak of KS phase by several wavenumber to low frequency and the broads Raman peaks in the low frequency region. Moreover, the above two processes were reversible. The Raman analyses of the CZTS samples prepared under different process show that the PD–KS structure tends to be found at low temperatures and low sulfur vapor pressures. Our results reveal that the control of the phase structure in CZTS films is feasible by adjusting the preparation process of the films. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) are radio transients lasting only about a few milliseconds. They seem to occur at cosmological distances. We propose that these events can originate in the collapse of the magnetospheres of Kerr–Newman black holes (KNBHs). We show that the closed orbits of charged particles in the magnetospheres of these objects are unstable. After examining the dependencies on the specific charge of the particle and the spin and charge of the KNBH, we conclude that the resulting timescale and radiation mechanism fit well with extant observations of FRBs. Furthermore, we argue that the merger of a KNBH binary is a plausible central engine for the potential gamma-ray or radio afterglow following certain FRBs and can also account for gravitational wave (GW) events like GW 150914. Our model leads to predictions that can be tested by combined multi-wavelength electromagnetic and GW observations. [ABSTRACT FROM AUTHOR]

Joining conducting polymer (CP) nanofibers into an interconnected porous network can result in good mechanical and electrical contacts between nanofibers that can be beneficial for the high performance of CP-based devices. Here, we demonstrate the cold welding of polyaniline (PAni) nanofiber loose ends with cold plasma. The room-temperature and atmospheric-pressure helium micro-plasma jet launches highly charged ion bullets at a PAni nanofiber target with high precision and the highly charged ion bullet selectively induces field emission at the sharp nanofiber loose ends. This technique joins nanofiber tips without altering the morphology of the film and protonation thus leading to significantly enhanced electrical and mechanical properties. In addition, this technique has high spatial resolution and is able to selectively weld and dope regions of nanofiber film with promising novel device applications. [ABSTRACT FROM AUTHOR]

How to evaluate plasma-derived heat (PDH) and the synergistic effect of plasma catalysis, especially for in-plasma catalysis (IPC), is still ambiguous. In this work, to exclude the reaction-heat impact on PDH, N2 plasma was first used to compare the heat-uninsulated and heat-insulated cases for empty and packed dielectric barrier discharge (DBD). Compared with the heat-uninsulated cases, the heat-insulation has nearly the same discharge characteristics, and a weak impact on N2 rotational temperature. The heat-insulation, whether for empty or packed DBD, gave much higher outgoing gas temperature (Tg) and reactor wall temperature (Tw) than the heat uninsulation. For methanol-steam reforming in the heat-insulated reactor over various supported catalysts on Al2O3 support (AS), the dependence of PDH indicated by Tw on reaction-heat power was observed. The synergistic effect of plasma and Au/CeZn/AS catalyst in the heat-insulated IPC reactor was verified. For the plasma alone case, methanol conversion was negligible, giving a Tw of 618 K. For the IPC case, the Tw decreased considerably to 545 K due to the effect of reaction-heat power on PDH. Methanol conversion of 46.8% was achieved, which is much higher than the catalysis alone case of 9.0%, even at a higher temperature of 573 K. Moreover, H2 selectivity increased from plasma alone from 80.0% to 95.1%. If the IPC case was heat-uninsulated, the Tw dropped down to 385 K, and accordingly methanol conversion became insignificant. This work demonstrated that heat-insulation is necessary for reliable evaluation of the PDH and the synergistic effect in plasma catalysis. [ABSTRACT FROM AUTHOR]

GaN-based yellow light-emitting diodes (LEDs) on Si substrates are aged at a direct current density of 50 A/cm2 for 500 h. After the aging process, it can be found that the LEDs have a stable electrical property but their light output power is decayed by 4.01% at 35 A/cm2. Additionally, the aging mechanism of GaN-based yellow LED is analyzed. It is found that the decay of light output power may be attributed to the following two reasons: one is the increase of Shockley–Rrad–Hall recombination and the other is the change of the transport path of holes via V-pits after aging, which may induce the radiative recombination current to decrease. In this paper, not only the aging mechanism of GaN-based yellow LED is investigated, but also a new possible research direction in LED aging is given. [ABSTRACT FROM AUTHOR]

Effect of hydrogen (H2) treatment during the GaN barrier growth on the electroluminescence performance of green InGaN/GaN single-quantum-well light-emitting diodes (LEDs) grown on Si substrates is experimentally investigated. We prepare two LED samples with different carrier gas compositions during the growth of GaN barrier. In the H2free LED, the GaN barrier is grown in full nitrogen (N2) atmosphere. For the other H2treated LED, a mixture of N2and H2was used as the carrier gas. It is observed that V-shaped pits decrease in size after H2treatment by means of the scanning electron microscope. Due to the fact that the p–n junction interface would be closer to the p-GaN as a result of smaller V-shaped pits, the tunneling barrier for holes to inject into the InGaN quantum well would become thicker after H2treatment. Hence, the external quantum efficiency of the H2treated LED is lower compared to the H2free LED. However, LEDs would exhibit a better leakage behavior after H2treatment during the GaN barrier growth because of more effective blocking of the threading dislocations as a result of the H2etching at V-shaped pits. [ABSTRACT FROM AUTHOR]

The form of the external potential (FEP) for generating field emission resonance (FER) in a scanning tunneling microscopy (STM) junction is usually assumed to be triangular. We demonstrate that this assumption can be examined using a plot that can characterize FEP. The plot is FER energies versus the corresponding distances between the tip and sample. Through this energy–distance relationship, we discover that the FEP is nearly triangular for a blunt STM tip. However, the assumption of a triangular potential form is invalid for a sharp tip. The disparity becomes more severe as the tip is sharper. We demonstrate that the energy–distance plot can be exploited to determine the barrier width in field emission and estimate the effective sharpness of an STM tip. Because FERs were observed on Pb islands grown on the Cu(111) surface in this study, determination of the tip sharpness enabled the derivation of the subtle expansion deformation of Pb islands due to electrostatic force in the STM junction. [ABSTRACT FROM AUTHOR]

The fabrication of a current collector-contained in-plane micro-supercapacitor (MSC) usually requires the patterning of the current collector first and then subsequent patterning of the active material with the assistance of a photoresist and mask. However, this two-step patterning process is too complicated and the photoresist used is harmful to the properties of nanomaterials. Here, we demonstrate a one-step, mask-free strategy to pattern the current collector and the active material at the same time, for the fabrication of an all-solid-state flexible in-plane MSC. Silver nanowires (AgNWs) are used as the current collector. An atmospheric pressure pulsed cold micro-plasma-jet is used to realize the one-step, mask-free production of interdigitated multi-walled carbon nanotube (MWCNT)/AgNW electrodes. Remarkably, the fabricated MWCNT/AgNW-based MSC shows good flexibility and excellent rate capability. Moreover, the performance of properties including cyclic stability, equivalent series resistance, relaxation time and energy/power densities of the MWCNT/AgNW-based MSC are significantly enhanced by the presence of the AgNW current collector. [ABSTRACT FROM AUTHOR]

InGaN-based green light-emitting diodes (LEDs) with and without Mg-preflow before the growth of p-AlGaN electron blocking layer (EBL) are investigated experimentally. A higher Mg doping concentration is achieved in the EBL after Mg-preflow treatment, effectively alleviating the commonly observed efficiency collapse and electrons overflowing at cryogenic temperatures. However, unexpected decline in quantum efficiency is observed after Mg-preflow treatment at room temperature. Our conclusions are drawn such that the efficiency decline is probably the result of different emission positions. Higher Mg doping concentration in the EBL after Mg-preflow treatment will make it easier for a hole to be injected into multiple quantum wells with emission closer to p- GaN side through the c-plane rather than the V-shape pits, which is not favorable to luminous efficiency due to the preferred occurrence of accumulated strain relaxation and structural defects in upper QWs closer to p-GaN. Within this framework, apparently disparate experimental observations regarding electroluminescence properties, in this work, are well reconciled. [ABSTRACT FROM AUTHOR]

In this study, we deposited Fe films on MoS2 flakes, and investigated the microscopic magnetic behavior on individual flakes. The MoS2 flakes were fabricated on SiO2/Si(1 0 0) substrates using chemical vapor deposition. Fe coverage was deposited on the MoS2 flakes by e-beam evaporation with a thin Pd capping for protection. Investigations by atomic force microscope and Raman spectroscopy confirmed that the MoS2 flakes had a mean lateral size of 10–20 μ m and mostly single layer thick. After depositing 3.6 and 7.0 nm Fe on MoS2/SiO2, clear hysteresis loops were observable with the in-plane magnetic field. From the investigation using a magneto-optical Kerr microscope, we measured the hysteresis curves within individual MoS2 flakes. Although the Fe coverage was much thicker than the MoS2 atomic step height (∼0.66 nm) and the direct connection and strong ferromagnetic coupling between Fe/MoS2 and Fe/SiO2 were expected, a magnetic decoupling between the magnetic domains of Fe/MoS2 and Fe/SiO2 was surprisingly observed. For 3.6 nm Fe/MoS2, the magnetic coercivity (Hc) was 28  ±  5 Oe, while in contrast, the Hc of 3.6 nm Fe/SiO2 ranged 58  ±  5 Oe. With a thicker Fe coverage of 7.0 nm, the Hc of Fe/MoS2 and Fe/SiO2 converged and the magnetic decoupling became too weak to observe. The distinct interface magnetic anisotropy of Fe on different substrates was held responsible for the observed magnetic decoupling across the MoS2 atomic step between Fe/MoS2 and Fe/SiO2 domains. These observations will be valuable in combining a magnetic coverage with a single layer MoS2 for future spintronic applications. [ABSTRACT FROM AUTHOR]

Silver nanowire (AgNW) thin film is a promising candidate to replace traditional indium tin oxide in optoelectronics applications. To date however, the widespread application of AgNW thin film is limited by the weak point contacts between individual AgNWs and the lack of facile patterning techniques. Here, we demonstrate a novel and facile method to not only nanoweld AgNW junctions but also pattern AgNW thin films via mask-free cold plasma-jet scanning in ambient conditions. After the plasma-jet nanowelding treatment, the morphology of AgNWs change substantially and the junctions are welded together. The nanowelded AgNWs-based thin film shows enhanced electrical and mechanical properties. On the other hand, after the plasma-jet patterning treatment, the AgNWs are etched and transformed into separated large particles. Different kinds of patterns are produced via this patterning technique. At last, a simple light emitting diode circuit is fabricated to demonstrate the suitability of the nanowelded and patterned AgNW electrodes for flexible electronic devices. [ABSTRACT FROM AUTHOR]

InGaN-based green light-emitting diodes (LEDs) with different growth temperatures of superlattice grown on Si (111) substrates are investigated by temperature-dependent electroluminescence between 100 K and 350 K. It is observed that with the decrease of the growth temperature of the superlattice from 895°C to 855°C, the forward voltage decreases, especially at low temperature. We presume that this is due to the existence of the larger average size of V-shaped pits, which is determined by secondary ion mass spectrometer measurements. Meanwhile, the sample with higher growth temperature of superlattice shows a severer efficiency droop at cryogenic temperatures (about 100 K–150 K). Electron overflow into p-GaN is considered to be the cause of such phenomena, which is relevant to the poorer hole injection into multiple quantum wells and the more reduced effective active volume in the active region. [ABSTRACT FROM AUTHOR]

Hydrogen (H) is a common impurity in metals and has a significant effect on their purification, even at concentrations of only a few parts per million. Here we present a comparative analysis of the behaviors of H in Au and Ag based on first-principles calculations. In bulk Au and Ag, the results demonstrate that the tetrahedral position is energetically more stable for a single H atom than the octahedral site. The concentration of H dissolving in the interstitial sites as a function of temperature is calculated in both metals. To characterize the dynamic behaviors, in bulk Au and Ag we determine the theoretical diffusivity and permeation of H, which are in quantitative agreement with the experimental data. Further, we investigate the role of vacancy on the formation of the Hn–vacancy (HnV) via a clustering reaction. One vacancy can accommodate up to 9 H atoms in Au and capture as many as 7 H atoms in Ag. The H2 molecule in the vacancy is energetically unstable in both metals. These research results will provide a very useful reference for the refinement of Ag/Au as noble metals in industry. [ABSTRACT FROM AUTHOR]

One-process fabrication of highly active and reproducible surface-enhanced Raman scattering (SERS) substrates via ion beam deposition is reported. The fabricated metal–dielectric–metal (MDM) hierarchical nanostructure possesses rich nanogaps and a tunable resonant cavity. Raman scattering signals of analytes are dramatically strengthened due to the strong near-field coupling of localized surface plasmon resonances (LSPRs) and the strong interaction of LSPRs of metal NPs with surface plasmon polaritons (SPPs) on the underlying metal film by crossing over the dielectric spacer. The maximum Raman enhancement for the highest Raman peak at 1650 cm−1 is 13.5 times greater than that of a single metal nanoparticle (NP) array. Moreover, the SERS activity can be efficiently tailored by varying the size and number of voids between adjacent metal NPs and the thickness of the dielectric spacer. These findings may broaden the scope of SERS applications of MDM hierarchical nanostructures in biomedical and analytical chemistry. [ABSTRACT FROM AUTHOR]

In the present paper, the concentration effect of near-infrared quantum cutting of Tm3+ ion in (Y1–xTmx)3Al5O12 powder phosphor is studied by means of experiments and calculations. In addition, the absorption spectra, visible-to-near-infrared excitation and emission spectra, and fluorescence lifetimes are measured. It is found that (Y1–xTmx)3Al5O12 powder phosphor has a strong four-photon near-infrared quantum cutting luminescence of 1788.0-nm 3F4 → 3H6 fluorescence of Tm3+ ion, when excited by 357.0-nm light. It is also found that the up-limit of the four-photon near-infrared quantum cutting luminescence efficiency of (Y0.700Tm0.300)3Al5O12 powder phosphor is approximately 302.19%. To the knowledge of the authors, this is the first time that a near-infrared quantum cutting efficiency up-limit exceeding 300% has been reported. The results of this manuscript are valuable in aiding the probing of the new generation Ge solar cell. [ABSTRACT FROM AUTHOR]