Ultrafine WC_1–<i>x</i> Nanocrystals: An Efficient Cocatalyst for the Significant Enhancement of Photocatalytic Hydrogen Evolution on g‑C₃N₄

Developing noble metal-free, inexpensive, and highly active cocatalysts to increase the photocatalytic activity of photocatalysts and promote the practical application is significantly important. In this work, ultrafine carbon-deficient tungsten carbide (WC1–x) nanocrystals with an average size of 1.98 ± 0.29 nm are successfully prepared as cocatalysts to dramatically enhance the photocatalytic activity of graphitic carbon nitride (g-C3N4). The optimized system (WC1–xCN5) exhibits the best photocatalytic H2 production rate of 124.5 μmol h–1 (2490 μmol h–1 g–1), which is about 56 times that of bare g-C3N4. In this system, ultrafine WC1–x nanocrystals play a multifunctional role: effectively boosting the carrier separation and transfer and providing rich active sites for H2 production. Hence, the loading of WC1–x nanocrystals remarkably increases the photocatalytic H2 production activity of g-C3N4. This work demonstrates that ultrafine WC1–x nanocrystals have practical application potential to enhance photocatalytic H2 evolution of g-C3N4

Surface Roughening of Nickel Cobalt Phosphide Nanowire Arrays/Ni Foam for Enhanced Hydrogen Evolution Activity

Development of earth-abundant, efficient, and stable electrocatalysts for hydrogen evolution reactions (HER) in alkaline or even neutral pH electrolyte is very important for hydrogen production from water splitting. Construction of bimetal phosphides via tuning the bonding strength to hydrogen and increasing effective active sites through nanostructuring and surface engineering should lead to high HER activity. Here, ternary NiCoP nanowires (NWs) decorated by homogeneous nanoparticles have been obtained on Ni foam for a highly efficient HER property via long-term cyclic voltammetric (CV) sweeping. The electron density transfer between the positively charged Ni and Co and negatively charged P atoms, one-dimensional electron transfer channel of the NWs, and abundant active sites supplied by the nanoparticles and NWs endow the catalyst with low overpotentials of 43 and 118 mV to achieve the respective current densities of 10 and 100 mA cm^–2 together with long durability for at least 33 h in 1 M KOH. A cycled anodic dissolution–redeposition mechanism is disclosed for the formation of the NiCoP nanoparticles during the CV sweeping process. Such a surface roughening method is found to be adaptable to enhance the HER property of other phosphides, including Ni₂P nanoplates/NF, NiCoP nanoparticles/NF, and CoP NW/NF

SnS Nanoflake-Based Field Effect Transistor with an Anisotropic Gate Effect and a Polarization-Dependent Raman Response

SnS has attracted intensive attention because of the strong anisotropic electric and optical properties along the in-plane zigzag and armchair directions. In this work, SnS nanoflakes with the lateral sizes varying from 3 to 112 μm and thicknesses varying from 2.7 to 305.4 nm were synthesized by controlling the growth temperature and time of chemical vapor deposition. With the thickness was decreased from 22.4 to 3.2 nm, obvious red shifts were observed in the “waving” and “breathing” vibration modes along the normal direction of the (010) plane and the “NaCl” type vibration along the in-plane zigzag direction. Meanwhile, the “NaCl” type vibration along the armchair direction shows a distinct blue shift. The intensity of the vibrations along the two typical in-plane directions are also highly in-plane anisotropic and thickness-dependent. The anisotropic electrical properties of SnS thin films were also studied using back-gated multiple-electrode SnS nanostructured field effect transistors. Interestingly, the gate effect is nearly absent along the zigzag direction, while the output characteristic along the armchair direction shows a strong gate effect. The zigzag/armchair conductance ratio reaches as high as 31 when VD = −8 V at Vg = 0 V, which may pave the way for future optoelectronic applications with high anisotropic optical response and electrical transport

CdSe Nanotube Arrays on ITO via Aligned ZnO Nanorods Templating

Using a ZnO nanorod array as the template, vertically aligned CdSe nanotubes have been demonstrated on indium tin oxide (ITO) glass in large scale. The wall thickness of the nanotube is tunable and can be increased until the formation of a continuous porous CdSe network. Detailed morphological and structural characterizations of the samples during the nanotube array formation reveal a growth mechanism that can be generally applied to a wide range of materials. In particular, we found that preferable CdSe nucleation and growth on the side surface ({101̅0} planes) of the ZnO nanorods in the array is critical to the later formation of a tubular structure with controllable wall thickness

Aligned ZnO/CdTe Core−Shell Nanocable Arrays on Indium Tin Oxide: Synthesis and Photoelectrochemical Properties

Vertically aligned ZnO/CdTe core−shell nanocable arrays-on-indium tin oxide (ITO) are fabricated by electrochemical deposition of CdTe on ZnO nanorod arrays in an electrolyte close to neutral pH. By adjusting the total charge quantity applied during deposition, the CdTe shell thickness can be tuned from several tens to hundreds of nanometers. The CdTe shell, which has a zinc-blende structure, is very dense and uniform both radially and along the axial direction of the nanocables, and forms an intact interface with the wurtzite ZnO nanorod core. The absorption of the CdTe shell above its band gap (∼1.5 eV) and the type II band alignment between the CdTe shell and the ZnO core, respectively, demonstrated by absorption and photoluminescence measurements, make a nanocable array-on-ITO architecture a promising photoelectrode with excellent photovoltaic properties for solar energy applications. A photocurrent density of ∼5.9 mA/cm2 has been obtained under visible light illumination of 100 mW cm−2 with zero bias potential (vs saturated calomel electrode). The neutral electrodeposition method can be generally used for plating CdTe on nanostructures made of different materials, which would be of interest in various applications

Quantum frequency conversion and single-photon detection with lithium niobate nanophotonic chips

In the past few years, the lithium niobate on insulator (LNOI) platform has revolutionized lithium niobate materials, and a series of quantum photonic chips based on LNOI have shown unprecedented performances. Quantum frequency conversion (QFC) photonic chips, which enable quantum state preservation during frequency tuning, are crucial in quantum technology. In this work, we demonstrate a low-noise QFC process on an LNOI nanophotonic platform designed to connect telecom and near-visible bands with sum-frequency generation by long-wavelength pumping. An internal conversion efficiency of 73% and an on-chip noise count rate of 900 counts per second (cps) are achieved. Moreover, the on-chip preservation of quantum statistical properties is verified, showing that the QFC chip is promising for extensive applications of LNOI integrated circuits in quantum information. Based on the QFC chip, we construct an upconversion single-photon detector with the sum-frequency output spectrally filtered and detected by a silicon single-photon avalanche photodiode, demonstrating the feasibility of an upconversion single-photon detector on-chip with a detection efficiency of 8.7% and a noise count rate of 300 cps. The realization of a low-noise QFC device paves the way for practical chip-scale QFC-based quantum systems in heterogeneous configurations

Image_1_Association of high PM2.5 levels with short-term and medium-term lung function recovery in patients with pulmonary lobectomy.JPEG

The association between exposure to ambient fine particulate matter with an aerodynamic diameter of ≤ 2.5 μm (PM2.5) and short- and medium-term lung function recovery (LFR) in patients undergoing lobectomy remains uncertain. This study investigated the associations between PM2.5 concentrations and LFR in adult patients (n = 526) who underwent video-assisted thoracoscopic (VATS) lobectomy in Guangzhou, China between January 2018 and June 2021. All patients underwent at least two spirometry tests. Environmental PM2.5 concentrations in the same period were collected from the nearest monitoring station. A multiple linear regression (MLR) model was employed to investigate the associations between changes in PM2.5 concentrations and LFR in patients who underwent lobectomy after adjusting for potential confounders. We assessed short- and medium-term LFR in patients who underwent lobectomy. The three- and 6-month average PM2.5 concentrations in each patient's residential area were divided into regional mild pollution (PM2.5 3), moderate pollution (25 μg/m3 ≤ PM2.5 3), and severe pollution (35 μg/m3 ≤ PM2.5) periods. The MLR model confirmed that PM2.5 was an independent risk factor affecting short-term forced lung capacity (FVC), forced expiratory volume in 1 s (FEV1), and maximum expiratory flow at 50% vital capacity (MEF50) recovery (adjusted P = 0.041, 0.014, 0.016, respectively). The MLR model confirmed that PM2.5 was an independent risk factor affecting medium-term MEF50 recovery (adjusted P = 0.046). Compared with the moderate and severe pollution periods, the short- and medium-term LFR (FVC, FEV1, MEF50) of patients in the mild pollution period were faster and better (P 2.5 levels was associated with significantly reduced speed and degree of short- and medium-term LFR in patients who underwent lobectomy.</p

Co₂N_0.67/MoO₂ Heterostructure as High-Efficiency Electrocatalysts for the Hydrogen Evolution Reaction

The design and development of efficient, cheap, and clean electrocatalysts are of great significance to the large-scale realization of electrocatalytic hydrogen production. Here, for the first time, we used H2O2-treated Mo foil (MF) loaded with cobalt hydroxide carbonate nanowires as precursors and then heated it in an ammonia atmosphere to obtain a Co2N0.67/MoO2 heterostructure. Compared with Co2N0.67/MF, Co2N0.67/MoO2/MF exhibited better hydrogen evolution reaction (HER) activity with a low overpotential of 75.2 mV to reach the current density of 10 mA/cm2 and a good long-term stability. Furthermore, we found that the introduction of MoO2 can improve interfacial conductivity and increase active sites, resulting in excellent electrocatalytic HER performance. Meanwhile, density functional theory results indicate that Co2N0.67/MoO2 shows an optimized hydrogen adsorption Gibbs free energy (ΔGH), which contributes to the outstanding HER activity. It is expected that MoO2 can be combined with more materials (such as sulfides, MXenes, etc.) to develop more excellent and inexpensive electrocatalysts

Robust Two-Dimensional Ferromagnetism in Cr₅Te₈/CrTe₂ Heterostructure with Curie Temperature above 400 K

The discovery of ferromagnetism in two-dimensional (2D) van der Waals crystals has generated widespread interest. The seeking of robust 2D ferromagnets with high Curie temperature (Tc) is vitally important for next-generation spintronic devices. However, owing to the enhanced spin fluctuation and weak exchange interaction upon the reduced dimensionalities, the exploring of robust 2D ferromagnets with Tc > 300 K is highly demanded but remains challenging. In this work, we fabricated air-stable 2D Cr5Te8/CrTe2 vertical heterojunctions with Tc above 400 K by the chemical vapor deposition method. Transmission electron microscopy demonstrates a high-quality-crystalline epitaxial structure between tri-Cr5Te8 and 1T-CrTe2 with striped moiré patterns and a superior ambient stability over six months. A built-in dual-axis strain together with strong interfacial coupling cooperatively leads to a record-high Tc for the CrxTey family. A temperature-dependent spin-flip process induces the easy axis of magnetization to rotate from the out-of-plane to the in-plane direction, indicating a phase-dependent proximity coupling effect, rationally interpreted by first-principles calculations of the magnetic anisotropy of a tri-Cr5Te8 and 1T-CrTe2 monolayer. Our results provide a material realization of effectively enhancing the transition temperature of 2D ferromagnetism and manipulating the spin-flip of the easy axis, which will facilitate future spintronic applications

One-Pot Synthesis of Co-Doped VSe₂ Nanosheets for Enhanced Hydrogen Evolution Reaction

We report a simple one-step hydrothermal method to fabricate cobalt (Co)-doped vanadium diselenide (VSe2) nanosheets on a carbon cloth for the hydrogen evolution reaction (HER) in acid solution. We find that the Co-doped VSe2 shows significantly enhanced catalytic activity compared with the pristine VSe2, including a low overpotential of 230 mV at 10 mA/cm2, a small Tafel slope of 63.4 mV/dec, and high stability. Our density functional theory calculations show that Co dopants dramatically reduce the Gibbs free energy for hydrogen adsorption (ΔGH), leading to improved catalytic activity for hydrogen evolution. Moreover, the Co doping promotes electron transfer and HER kinetics. Our results provide a valuable route to improve the catalytic performance of metal diselenide in HER