Stabilizing Pt Single Atoms through Pt−Se Electron Bridges on Vacancy-enriched Nickel Selenide for Efficient Electrocatalytic Hydrogen Evolution

Rational design of Pt single-atom catalysts provides a promising strategy to significantly improve the electrocatalytic activity for hydrogen evolution reaction. In this work, we presented a novel and efficient strategy for utilizing the low electron-density region of substrate to effectively trap and confine high electron-density metal atoms. The Pt single-atom catalyst supported by nickel selenide with rich vacancies was prepared via a hydrothermal-impregnation stepwise approach. Through experimental testation and DFT theoretical calculation, we confirm that Pt single atoms are well distributed at cationic vacancies of nickel selenide with loading amount of 3.2 wt. %. Moreover, the atomic Pt combined with the high electronegative Se to form Pt−Se bond as a “bridge” between single atoms and substrate for fast electron translation. This novel catalyst shows an extremely low overpotential of 45 mV at 10 mA cm⁻² and an excellent stability over 120 h. Furthermore, the nickel selenide supported Pt SACs exhibits long-term stability for practical application, which maintains a high current density of 390 mA cm⁻² over 80 h with a retention of 99 %. This work points a promising direction for designing single atoms catalysts with high catalytic activity and stability for advanced green energy conversion technologies.     

Calibration model transfer for near-infrared spectra based on canonical correlation analysis

In order to solve the calibration transformation problem in near-infrared (NIR) spectroscopy, a method based on canonical correlation analysis (CCA) for calibration model transfer is developed in this work. Two real NIR data sets were tested. A comparative study between the proposed method and piecewise direct standardization (PDS) was conducted. It is shown that the transfer results obtained with the proposed method based on CCA were better than those obtained by PDS when the subset had sufficient samples.     

A QTAIM and stress tensor perspective of large‐amplitude motions of the tetrasulfur tetranitride S4N4 molecular graph

The nature of the bonding interactions including the intramolecular S? S interactions in tetrasulfur tetranitride, S₄N₄ are probed by performing very large amplitude vibrations of all of the 18 normal modes of vibration. The QTAIM and stress tensor point properties are ‐then investigated and found to be highly dependent on the mode of vibration. A considerable degree of metallicity ξ( r _b) is found for the S? S and S? N bonding interactions. A unique bonding feature is found for a small amplitude vibration of the most anharmonic mode of this investigation, mode 2, where the S? S bond critical point (BCP) transforms from a closed‐shell S? S BCP to a shared‐shell S? S BCP. We find 17 new unique QTAIM topologies for the molecular graphs corresponding to the 18 modes of vibration along with seven “missing” topologies that are mapped onto a spanning 2‐D Quantum topology Phase Diagram (QTPD). In addition, eleven unique topologies existing on 3‐D QTPDs are found due to the presence of non‐nuclear attractors (NNAs). We use the stress tensor eigenvalues to explain the invariance of the numbers and types of QTAIM critical points. The applicability of both the stiffness S and stress tensor stiffness S_σ are also explored. Two new bond measures are introduced, a polarizability P and the stress tensor polarizability P_σ which are derived from the stiffness S and stress tensor stiffness S_σ, respectively. © 2016 Wiley Periodicals, Inc.     

含时密度矩阵重正化群的理论与应用

密度矩阵重正化群(DMRG)作为计算低维强关联体系强有力的方法为人熟知, 在量子化学电子结构计算中得到广泛应用. 最近几年, 含时密度矩阵重正化群(TD-DMRG)的理论取得较快发展, TD-DMRG逐渐成为复杂体系量子动力学理论模拟的重要新兴方法之一. 本文综述了基于矩阵乘积态(MPS) 和矩阵乘积算符(MPO)的DMRG基本理论, 并重点介绍了若干最常见的TD-DMRG时间演化算法, 包括基于演化再压缩(P&C) 的算法、 基于含时变分原理(TDVP)的算法和时间步瞄准(TST)算法; 还对利用TD-DMRG模拟有限温体系的纯化(Purification)算法和最小纠缠典型量子热态(METTS)算法进行了介绍. 最后, 对近年TD-DMRG在复杂体系量子动力学中的应用进行了总结.     

高重频束流采集处理器原型样机的设计

为了实现对高重频硬X射线自由电子激光装置(SHINE)条带型BPM(Beam Position Monitor)系统信号的数字化采样和处理,研制了高重频束流采集处理器原型样机。处理器拥有四通道输入,最高达1 GSps的采样率,16 bit采样位数,采用XILINX公司带有嵌入式CPU(Central Processing Unit)的ZYNQ系列FPGA(Field Programmable Gate Array),可以运行Linux系统,同时可以实现高速采样数据的缓存与读出。处理器采用子母板结构设计,子板为ADC(Analog To Digital Converter)采样板,母板为FPGA数字处理板,子母板通过FMC(FPGA Mezzanine Card)接口进行数据传输。ADC采用JESD204B协议进行数据传输,子母板间通过16对差分信号连接通道,最大总传输速率达到80 Gbps。ADC采样数据传入数字母板后,经过FIFO和DDR的缓存,最后通过TCP/IP协议由RJ45接口传输到上位机进行处理和分析,RJ45接口的数据传输速率约为900 Mbps。经过测试,ADC采集子板的带宽高于480 MHz,且在480 MHz带宽内有效位高于10位。FPGA数字母板运行经Petalinux编译的Linux系统,可以实现对连续或者触发模式下,四通道一百万个采样点的存储与数据传输。整个设计可以满足设计要求。     

The Simulation and Experiment of In 718 in Warm Laser Shock Processing Without Coating

Journal of Russian Laser Research - A modified constitutive model, combining laser shock processing and dynamic strain aging (DSA), is used to obtain the compressive residual stress field of In 718...     

溅射功率对Mo薄膜微结构和性能的影响

 实验采用直流磁控溅射沉积技术在不同溅射功率下制备Mo膜,研究了不同溅射功率下Mo膜的沉积速率、表面形貌及晶型结构,并对其晶粒尺寸和应力进行了研究。利用原子力显微镜观察样品的表面形貌发现随着溅射功率的增加,薄膜表面粗糙度逐渐增大。X射线衍射分析表明薄膜呈立方多晶结构,晶粒尺寸为14.1～17.9 nm;应力先随溅射功率的增大而增大,在40 W时达到最大值(2.383 GPa),后随溅射功率的增大有所减小。     

Tuning the electrical transport properties of n-type CdS nanowires via Ga doping and their nano-optoelectronic applications

Gallium-doped n-type CdS nanowires (NWs) were successfully synthesized via a thermal evaporation method. The conductivities of the CdS NWs were dramatically improved by nearly nine orders of magnitude after Ga doping, and could be further tuned over a wide range by adjusting the doping level. High-performance metal-insulator-semiconductor field-effect transistors (MISFETs) were constructed based on the single CdS : Ga NW with high-κ Si(3)N(4) dielectrics and top-gate geometries. In contrast to back-gate FETs, the MISFETs revealed a substantial improvement in device performance. Nano-light emitting diodes (nanoLEDs) were fabricated from the CdS : Ga NWs by using a n-NW/p(+)-Si substrate hybrid device structure. The nanoLEDs showed a bright yellow emission at a low forward bias. It is expected that the Ga-doped CdS NWs with controlled electrical transport properties will have important applications in nano-optoelectronic devices.     

A highly efficient chemical sensor material for ethanol: Al2O3/Graphene nanocomposites fabricated from graphene oxide

Al(2)O(3)/Graphene nanocomposites are firstly produced from GO solution by a one-step, green, facile, low-cost SC CO(2) method. The as-prepared nanocomposite papers display high CL sensitivity and high selectivity to the ethanol gas, which provides a facile, green and low-cost route for the preparation of ethanol nanoscopic sensing devices with wide applications.     

Gelator-polysaccharide hybrid hydrogel for selective and controllable dye release

In this paper, 1,4-bi(phenylalanine-diglycol)-benzene (PDB) based Low-Molecular-Weight-Gelator (LMWG) hydrogels are modified using hydrophilic polysaccharide (sodium alginate). A set of techniques including Fourier transform infrared (FT-IR) spectroscopy, ¹H Nuclear Magnetic Resonance (¹H NMR), X-ray powder diffraction (XRD), Ultraviolet-Visible (UV-Vis), and circular dichroism (CD) had confirmed a β-turn arrangement of PDB gelators and a semi-interpenetrating network (semi-IPN), which was formed through hydrogen bonds between LMWG fibers and polysaccharide chains. The evaluation of physicochemical properties of hydrogels indicates that gelator-polysaccharide hybrid hydrogels possess better mechanical and water retention properties than LMWG hydrogels. The release study of dyes (model drug) from both LMWG and hybrid hydrogels was carried out. Compared with PDB based hydrogels, hybrid hydrogels show a selective and controllable release property for certain dyes. The results suggest LMWG-polysaccharide hybrid gels may find potential applications as promising drug delivery vehicles for drug molecules.