Recent advances in microfluidic fiber-spinning chemistry

Fiber-spinning chemistry (FSC) has emerged as a promising micro-reaction platform due to its high-specific surface area, efficient heat and mass transfer, and enhanced reaction rate. The FSC strategy employs spinning fibers as microreactors, lessening the emissions of volatile organic compounds (VOCs), and realizing the design of micro/nanoscale fibers and the synthesis of nanomaterials. In this review, we highlight the latest advancements in FSC in respect of preparation mechanisms and technical advantages. Various FSC strategies, including microfluidic spinning, electro-microfluidic spinning (EMS), and microfluidic blow spinning (MBS) are emphasized. In particular, the regulation of microfluidic chips in the FSC process is introduced. Additionally, the application of the FSC strategy is summarized in the synthesis of fluorescent nanomaterials, nonweaving for multidimensional fibers, and all-weather smart textiles. Finally, the advanced progress and future perspectives are discussed. Overall, this review will provide theoretical guidance for the design of well-defined micro/nanoscale fibers based on the FSC platforms.     

Lattice Vibration and Transmissivity in Nd-Doped Yttrium Orthovanadate Crystals

Neodymium-doped yttrium orthovanadate Nd_xY_1—xVO₄(NYV), with x = 0.025, crystallizes with a zircon-type structure in the tetragonal system conforming to the space group I4₁/amd. The lattice constants are a = b = 0.7123 ± 0.0005 and c = 0.6292 ± 0.0005 nm at room temperature. There are the four formulas per unit cell. The lattice-vibration and transmissivity spectra show that the NYV crystal is a good laser host crystal, which provides a suitable crystal field for the active ions. A strong absorption at 808 nm and the stimulated emission at 1.06 μm have provided the practical application as a laser crystal. Also, a strong fluorescent radiation at 0.408 μm, corresponding to a transition ⁴D_3/2 → ⁴I_13/2, is observed.     

Single molecule force spectroscopy on poly(vinyl alcohol) by atomic force microscopy

The elastic properties of poly(vinyl alcohol) (PVA) were investigated on the nanoscale using the new technique of single molecule force spectroscopy by atomic force microscopy (AFM). It was found that the elastic properties of PVA molecules scale linearly with their contour lengths. This finding corroborates that the deformation of individual PVA chains is measured. The force spectra of PVA show a kink at around 200 pN and cannot be fitted by an extended Langevin function. The deviation of the elastic behavior of PVA from a freely jointed chain model may indicate the presence of a suprastructure of PVA in NaCl solution.     

紧凑型X-pinch装置探头标定

 介绍了紧凑型X-pinch脉冲功率装置的电流电压测量设计方法。根据该装置的同轴传输线结构特点,研制了一种利用金属膜连接传输线外筒与负载外筒,构成回路测量负载电流的探头。在传输线末端设计电容分压器作为测量负载电压的探头,并利用电路模拟软件对此过程进行模拟,同时这两个探头需要进行在线标定。实验研究结果表明,该探头性能稳定、响应快,是测量负载电流与电压的理想工具。     

面向空耦电声换能器应用的高性能FEP/PTFE复合膜压电驻极体

压电驻极体(也称为铁电驻极体)是一类具有强压电效应的微孔结构驻极体材料,具有柔韧、低密度、低特性声阻抗等特征,是制备柔性空气耦合声电换能器的理想材料.针对器件对高灵敏度和高温工作环境的应用需求,本文报道高性能氟化乙丙烯/聚四氟乙烯(FEP/PTFE)复合膜压电驻极体的制备和性能表征.研究结果表明,FEP/PTFE膜的特...     

(C4N2H12)[(GeO2)3(BO1.5F)2], a layered borogermanate containing three‐ and nine‐membered rings

A new borogermanate, viz. piperazine‐1,4‐di­ium di­fluoro­nona­oxo­tri­germanium­di­boron, (C₄H₁₂N₂)[(GeO₂)₃(BO_1.5F)₂], was solvo/hydro­thermally synthesized. The crystal structure consists of layers composed of three‐membered‐ring Ge₃O₉ subunits and nine‐membered‐ring channels formed by six GeO₄ tetrahedra and three BO₃F tetrahedral pairs. The diprotonated piperazine cations, which lie about inversion centres, are located between adjacent layers and connect the layers via hydrogen bonds.     

Properties and Applications of Mixed Packing Capillary Electrochromatography

Mixed packing capillary electrochromatography (MP CEC) with the stationary phase comprising a physical mixture of strong cation exchange (SCX) phase and octadecysilyl (ODS) phase was developed. With the existence of a sulfonic acid group on the surface of SCX, not only could the electroosmotic flow (EOF) remain high at low pH, but also the hydrophilicity of the stationary phase was increased greatly, leading to broad adaptable ranges of both pH and organic modifier concentration in the mobile phase. At the same time, with the coexistence of C₁₈ on the surface of ODS, both the retention and the resolution of samples were improved. Accordingly, MP CEC combined the advantages of both SCX and ODS columns. Effects of operation parameters on EOF and the capacity factors of solutes as well as the retention mechanism of such a column were studied systematically. In addition, MP CEC columns were used in the analysis of strong polar solutes as well as for the high speed separation of acidic, basic, and neutral compounds in a single run.     

Single-crystalline layered double hydroxides with rich defects and hierarchical structure by mild reduction for enhancing the oxygen evolution reaction

The oxygen evolution reaction(OER) with sluggish reaction kinetics and large overpotential is the critical reaction in water splitting that is promising for energy storage and conversion. Layered double hydroxides(LDHs), due to their unique lamellar structure and flexibility of chemical component, are very competing material candidates for OER. Herein, the morphology structure and the electronic structure of LDHs were simultaneously tuned to improve the OER catalytic activity by mild solvothermal reduction using ethylene glycol. The increased surface area, the introduction of oxygen vacancies and the construction of hierarchical structure greatly enhanced the electro-catalytic activity of LDHs for OER. The as-prepared LDHs showed a lower over-potential as low as 276 mV at a current density of 10 mA cm~(-2), and a small Tafel slope of 40.3 mV dec~(-1) accompanied with good stability. This work provides an efficient way to the design and optimization of advanced catalysts in the future.     

A Bubble‐Dragged Catalytic Polymer Microrocket

We report the bubble dragged microrocket consisting of functionalized multilayer polymer covered asymmetrically by platinum nanoparticles. The microrocket is pushed back during bubble growth over a small step and dragged forward over a big step during bubble explosion. Each bubble explosion induced a shock wave of gas which propagates in water at ultrafast speed. The bubble dragged microrocket can move along an approximate straight line instead of a fluctuating circle which is the trajectory of a bubble‐pushed microrocket in most cases, which makes it a promising candidate for drug delivery and simulating rod‐shaped bacteria.