纳米阵列中气体驱替液体的流动特征

纳米尺度下气体驱动液体流动特征在纳流控芯片及页岩气开发中具有广泛的应用前景. 利用管径规格为292.8 nm,206.2 nm,89.2 nm,67.0 nm,26.1 nm的氧化铝膜为纳米阵列,进行气驱水实验和单相气体流动实验,分析纳米尺度下气驱水流动特征. 实验表明,纳米阵列中气驱水时气体流量随驱动压力变化经历三个阶段:第一阶段流量缓慢增大,且比单相气体流量降低约一个数量级;第二阶段纳米阵列中的水被大量驱替出,流量迅速增大;第三阶段纳米阵列中的水全部被驱替出,流动特征与单相气体流动保持一致. 分析表明,气驱水第一阶段存在气液界面毛细管力的“钉扎”作用及固液界面相互作用力的影响,是产生非线性流动的主要原因;而一旦“钉扎”作用破坏,气体进入管道推动界面运动,气柱与液柱之间的毛细曲面曲率变化,毛细管力减小,气体流量急剧增大,其中毛细管力随驱替压力增大急剧变化,是造成第二阶段气体流量突变的主要原因.      

Nickel(II) Schiff base complex supported on nano‐titanium dioxide: A novel straightforward route for preparation of supported Schiff base complexes applying 2,4‐toluenediisocyanate

For the first time, a novel, straightforward and inexpensive route for immobilization of metals in Schiff base complex form is reported applying 2,4‐toluenediisocyanate as a precursor of primary amine group. A nickel(II) Schiff base complex supported on nano‐TiO₂ was designed and synthesized as an effective heterogeneous nanocatalyst for organic reactions, and well characterized using various techniques such as Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, energy‐dispersive X‐ray analysis and thermogravimetric analysis. The catalytic efficiency of the complex was evaluated in selective oxidation of sulfide to sulfoxide by hydrogen peroxide as an oxidant under solvent‐free conditions at room temperature, which successfully resulted in high yield and high conversion of products. Effective factors including solvent type, oxidant and catalyst amount were also optimized. The catalyst shows outstanding reusability and could be impressively recovered for six consecutive cycles without significant change of its catalytic efficiency.     

Nano‐MoO3 for highly selective enrichment of polycyclic aromatic hydrocarbons in in‐tube solid‐phase microextraction

Nano‐molybdenum trioxide was prepared from nano‐molybdenum disulfide by simple firing in muffle furnace. Nano‐molybdenum trioxide was used as the extraction coating on the stainless steel wire. Four wires were filled in a polyetheretherketone tube to get an extraction tube. The tube was connected to the six‐port valve of a high performance liquid chromatograph, and the online analysis system was constructed. Extraction selectivity of the tube for different types of compounds, including polycyclic aromatic hydrocarbons, plasticizers, estrogens, anilines and neonicotinoids, was studied. Good enrichment ability for polycyclic aromatic hydrocarbons, but the extraction efficiency of others was not satisfactory. Using eight polycyclic aromatic hydrocarbons as the targets, an analytical method was established after optimizing main factors such as sampling volume, sampling rate, methanol content, and desorption time. The established method exhibited wide linear range to 0.016–20.00 μg/L and low limits of detection to 0.005 μg/L, and the enrichment factors can be up to 2443. The method was applied to the detection of trace polycyclic aromatic hydrocarbons in tap water and river water, and a good recovery was obtained. The tube showed good durability and chemical stability, and it still remained good extraction effect after more than 140 run.     

硫化丁苯橡胶纳观界面耐磨机理及参数影响分析

硫化橡胶因其良好的力学和物理化学性能而被广泛作为摩擦副的基础材料. 本文提出了一种硫化交联算法, 实现了C—C键的硫化互交联和自交联, 构建了硫化丁苯橡胶的分子动力学磨损模型, 从微观摩擦学的角度阐明了硫化交联结构对改善丁苯橡胶磨损性能的机理, 研究了不同界面参数对硫化橡胶微观磨损性能的影响. 结果发现 硫化使丁苯橡胶分子链的界面黏附能力和活动能力更弱, 拉伸和解缠能力更低, 磨损过程中界面累积能量更低, 更不容易脱离橡胶基体, 因此可以表现出更好的摩擦学性能, 更强的抗磨损性能; 随着速度的增大, 硫化橡胶的磨损率降低, 与宏观实验结果一致, 原因是硫化橡胶的原子分布函数和相互作用能随着速度增大而降低, 说明橡胶分子链的黏附能力和活动能力随着速度增加趋弱, 温升更低, 导致较低的磨损率; 压入深度对磨损率的影响规律则呈现相反的结果和趋势.     

Self‐assembled polyurea macromer nanodispersion and resulting hybrid polyurea‐acrylic emulsions and films

A polyurea macromer (PUM) was synthesized and dispersed in basic conditions to form self‐assembled nanoparticles (<20 nm dispersions, up to 30 wt % aq. soln.). These nanoparticles enabled surfactant‐free emulsion polymerization to form hybrid polyurea‐acrylic particles despite the absence of a measureable water‐soluble fraction. The T_g of the starting PUM material was a strong function of the PUM's extent of neutralization and hydration (varying between 100 °C and >175 °C) due to changes in hydrogen and ionic bonding. Two separate hybrid polyurea‐acrylic emulsion systems were prepared: one by direct polymerization of (meth)acrylic monomers in the presence of the nanodispersion and a second by a physical blend of PUM nanodispersion with an acrylic latex control. The direct polymerization method resulted in a hybrid emulsion particle size that developed by a mechanism resembling conventional emulsion polymerization and was unlike that described for seeded polyurethane dispersion systems. Film hardness was shown to increase with increasing coating thickness for the hybrid film prepared by direct polymerization. The resulting mechanical properties could be explained by applying mechanical models for a composite foam structure. These results were unprecedented for normal elastomer films. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1373–1388     

Ultrasonic assisted synthesis of nanocrystalline cellulose as support and reducing agent for Ag nanoparticles: green synthesis and novel effective nanocatalyst for degradation of organic dyes

In this study, nanocrystalline cellulose (NCC) prepared from microcrystalline cellulose using high‐intensity ultrasonication as mechanical method without any chemical treatment. The obtained NCC with around 30–50 nm diameters, utilized as support, reducing and stabilizing agent for in‐situ green and eco‐friendly synthesis of silver nanoparticles (Ag NPs). The catalytic activity of composite was examined for degradation of environmental pollutants. The structure of as‐synthesized composite (Ag@NCC) was characterized by ultraviolet–visible spectroscopy (UV–vis), field emission scanning electron microscopy (FE‐SEM); Transmission electron microscopy (TEM); Energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD) and thermogravimetric analysis (TGA). The results of the catalytic reaction experiments showed that spherically shaped silver nanoparticles of around 20 nm distributed on the surface of nanocellulose demonstrated high catalytic efficiency towards the removal of methyl orange (MO) and 4‐nitrophenol (4‐NP).     

Synthesis of boronic acid‐functionalized poly(glycerol‐oligoγ‐butyrolactone): Nano‐networks for efficient electrochemical sensing of biosystems

Despite the outstanding properties of hyperbranched polyglycerols such as biocompatibility and multifunctionality, enough attention has not been paid to the synthesis of their functional copolymers. This problem has limited the structural diversity of hyperbranched polyglycerols and hampers further developments and their practical usage. In this work, butyrolactone segments were incorporated into the backbone of polyglycerols by one‐pot ring‐opening copolymerization of a mixture of glycidol and γ‐butyrolactone in the presence of tin(II) 2‐ethylhexanoate. Poly(glycerol‐oligoγ‐butyrolactone)s were then crosslinked by 2,5‐thiophenediylbisboronic acid to obtain polymeric nanonetworks with 140 nm average size. Afterwards, the gold electrode was modified by the polymeric nano‐networks, and it was used for the determination of glucose, glycated hemoglobin, and Escherichia coli in phosphate buffer solution (pH = 9.0) through cyclic voltammetry and impedance spectroscopic. Taking advantage of the straightforward synthesis, cheap precursors and multifunctionality of poly(glycerol‐oligoγ‐butyrolactone)s, they could be used for real‐time sensing of a wide range of biosystems. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1430–1439     

Chemical versus Electrochemical Synthesis of Carbon Nano‐onion/Polypyrrole Composites for Supercapacitor Electrodes

The development of high‐surface‐area carbon electrodes with a defined pore size distribution and the incorporation of pseudo‐active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano‐onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission‐ and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g^?1 for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g^?1 for the CNOs/Ppy bilayer (electrochemical deposition).     

Nanocrystalline TiO2, via green combustion synthesis,as an efficient and reusable catalyst for the preparation of 1,8‐dioxooctahydroxanthenes and 1,8‐dioxodecahydroacridines

Nanocrystalline TiO₂ is synthesized using a green combustion method and used as a recyclable catalyst for the one‐pot multicomponent synthesis of 1,8‐dioxodecahydroacridines and 1,8‐dioxooctahydroxanthenes, under solvent‐free conditions. This method is mild, environmentally friendly, inexpensive and highly effective for obtaining good to excellent yields of the products. Copyright © 2015 John Wiley & Sons, Ltd.     

A Universal Nano‐capillary Based Method of Catalyst Immobilization for Liquid‐Cell Transmission Electron Microscopy

A universal nano‐capillary based method for sample deposition on the silicon nitride membrane of liquid‐cell transmission electron microscopy (LCTEM) chips is demonstrated. It is applicable to all substances which can be dispersed in a solvent and are suitable for drop casting, including catalysts, biological samples, and polymers. Most importantly, this method overcomes limitations concerning sample immobilization due to the fragility of the ultra‐thin silicon nitride membrane required for electron transmission. Thus, a straightforward way is presented to widen the research area of LCTEM to encompass any sample which can be externally deposited beforehand. Using this method, Ni_xB nanoparticles are deposited on the μm‐scale working electrode of the LCTEM chip and in situ observation of single catalyst particles during ethanol oxidation is for the first time successfully monitored by means of TEM movies.