Synthesis of Stimuli-responsive Nanoparticles by Solution Polymerization

In this study, stimuli-responsive nanoparticles were prepared by solution polymerization. Two synthesis routes are proposed to synthesize the particles, the monomer route and the polymer/monomer route. For the monomer route, pH and thermal sensitive nanoparticles were synthesized from acrylic acid and N-isopropylacrylamide. For the polymer/monomer route, the pH sensitive nanoparticles were synthesized from chitosan and acrylic acid. The effect of reaction time, initiator concentration and agitation rate on the particle size and the size distribution were investigated. The stimuli-responsive nanoparticles could be directly blended with other polymers to prepare stimuli-responsive functional membranes.     

Preparation and Characteration of UV-cured EA/MMT Nanocomposites Via In-Situ Polymerization

A long-chain surfactant, enzoylbenzyl-N,N-dimethyl-N-octadecylammonium bromide (BDOB) with a benzophenone group, was synthesized to modify the montmorillonites (MMT) for the preparation of nanocomposites via photo-induced polymerization. The BDOB-modified MMT was characterized by the fourier transform infrared spectrometer (FTIR), thermal gravimetric analyzer (TGA) and X-ray diffraction (XRD), and the results of XRD indicated that the intercalated structures of BDOB-modified MMT was obtained. The conversion of the bisphenol A epoxy diacrylate (EA) was quantified by the FTIR, and the results indicated that conversion increased with an increase in the amount of BDOB-modified MMT. The morphologies of the UV-cured EA/MMT nanocomposites prepared from this organically modified MMT were studied by means of XRD and TEM, and the results showed that all the samples contained an intercalated structure with partial exfoliated structure. The results of TGA and mechanical properties also indicated that the thermal and mechanical properties of UV-cured nanocomposites were significantly enhanced due to the presence of the long chain surfactant organically modified MMT.     

Analysis of operation mode of reflective twisted nematic liquid crystal display devices with rear film compensation

The rear film compensated reflective twisted nematic liquid crystal display device was studied in normally black and normally white operation conditions using a dynamic parameter space method. The electro-optical responses and reflectance spectra were also studied for different operation modes. A comparison was made between rear film and front film compensated reflective twisted nematic liquid crystal displays. We show that high quality normally white or normally black modes can be obtained by placing the fast axis of a quarter wave plate at 45° or 0° to the input director direction. The viewing angle characteristics of the optimum modes were also studied.     

Activation of Hydrogen Peroxide by Ionic Liquids: Mechanistic Studies and Application in the Epoxidation of Olefins

Imidazolium‐based ionic liquids that contain perrhenate anions are very efficient reaction media for the epoxidation of olefins with H₂O₂ as an oxidant, thus affording cyclooctene in almost quantitative yields. The mechanism of this reaction does not follow the usual pathway through peroxo complexes, as is the case with long‐known molecular transition‐metal catalysts. By using in situ Raman, FTIR, and NMR spectroscopy and DFT calculations, we have shown that the formation of hydrogen bonds between the oxidant and perrhenate activates the oxidant, thereby leading to the transfer of an oxygen atom onto the olefin demonstrating the special features of an ionic liquid as a reaction environment. The influence of the imidazolium cation and the oxidant (aqueous H₂O₂, urea hydrogen peroxide, and tert‐butyl hydrogen peroxide) on the efficiency of the epoxidation of cis‐cyclooctene were examined. Other olefinic substrates were also used in this study and they exhibited good yields of the corresponding epoxides. This report shows the potential of using simple complexes or salts for the activation of hydrogen peroxide, owing to the interactions between the solvent medium and the active complex.     

Renormalization and conjugacy of piecewise linear Lorenz maps

We investigate the uniform piecewise linearizing question for a family of Lorenz maps. Let f be a piecewise linear Lorenz map with different slopes and positive topological entropy, we show that f is conjugate to a linear mod one transformation and the conjugacy admits a dichotomy: it is either bi-Lipschitz or singular depending on whether f is renormalizable or not. f is renormalizable if and only if its rotation interval degenerates to be a rational point. Furthermore, if the endpoints are periodic points with the same rotation number, then the conjugacy is quasisymmetric.     

Study on the Inherent Factors Affecting the Modification Effect of EVA on Waxy Crude Oils and the Mechanism of Pour Point Depression

The Ar-Sai waxy crude oils were taken as the research objects, and the viscosity reduction rates and the condensation point reduction rates were regarded as the evaluation indexes, the impacts of components content of the crude oils and carbon number distribution of waxes on the modification effect of EVA-type pour point depressant (PPD) were analyzed by using gray correlation analysis method. The oil wax was acquired by applying the extraction and separation techniques initially, then the structures and the lattice parameters of wax crystals before and after adding the PPD were studied by polarized light microscopy observation and x-ray diffraction techniques, the mechanism of pour point depression was discussed at last. The results indicate that wax content and the low carbon number wax have significant influences on the modification effect of PPD, while the impact of high carbon number wax is relatively small. Co-crystallization is the main mechanism of pour point depression, nevertheless, the impacts of the asphaltenes, resins, solid particles, and light components of the crude oils on the modification effect of the PPD cannot be ignored.     

Vacuum Ultraviolet Free-Electron Laser Photoionization Mass Spectrometry of Alpha-pinene Ozonolysis

\begin{document}$\alpha$\end{document}-pinene is the most abundant monoterpene that represents an important family of volatile organic compounds. Molecular identification of key transient compounds during the \begin{document}$\alpha$\end{document}-pinene ozonolysis has been proven to be a challenging experimental target because of a large number of intermediates and products involved. Here we exploit the recently developed hybrid instruments that integrate aerosol mass spectrometry with a vacuum ultraviolet free-electron laser to study the \begin{document}$\alpha$\end{document}-pinene ozonolysis. The experiments of \begin{document}$\alpha$\end{document}-pinene ozonolysis are performed in an indoor smog chamber, with reactor having a volume of 2 m\begin{document}$^3$\end{document} which is made of fluorinated ethylene propylene film. Distinct mass spectral peaks provide direct experimental signatures of previously unseen compounds produced from the reaction of \begin{document}$\alpha$\end{document}-pinene with O\begin{document}$_3$\end{document}. With the aid of quantum chemical calculations, plausible mechanisms for the formation of these new compounds are proposed. These findings provide crucial information on fundamental understanding of the initial steps of \begin{document}$\alpha$\end{document}-pinene oxidation and the subsequent processes of new particle formation.     

Amorphous Carbon Film with Self-modified Carbon Nanoparticles Synthesized by Low Temperature Carbonization of Phenolic Resin for Simultaneous Sensing of Dopamine and Uric Acid

A self-modified film electrode consisting of homogeneous snowflake-shaped nanoparticles on the amorphous carbon substrate (HNAC) was prepared by low temperature carbonization of phenolic resin. Such a unique structure was beneficial to enhance the electroanalysis signal responds. Simultaneous detection of DA and UA was performed on the HNAC using differential pulse voltammetry (DPV) at pH 8 phosphate buffer. The well-defined oxidation peak potential separation reached 260 mV between DA and UA. Meanwhile, the detection limit of HNAC were 0.401 μM (DA) and 2.800 μM (UA).     

硅单粒子位移损伤多尺度模拟研究

本文结合分子动力学方法和动力学蒙特卡罗方法, 研究了单个粒子入射硅引起的位移损伤缺陷的产生和演化过程; 基于Shockley-Read-Hall理论计算了单个粒子入射引起的位移损伤缺陷导致的泄漏电流增加及其演化过程, 比较了缺陷退火因子与泄漏电流退火因子之间的差异, 并将计算结果与实验值进行了对比. 结果表明, 计算泄漏电流时, 仅考虑一种缺陷的情况下缺陷退火因子与泄漏电流退火因子相同, 考虑两种缺陷类型情况下二者在数值上有所区别, 但缺陷退火因子仍能在一定程度上反映泄漏电流的退火行为. 分子动力学模拟中采用Stillinger-Weber势函数和Tersoff势函数时缺陷退火因子和泄漏电流退火因子与实验结果一致, 基于Stillinger-Weber势函数的计算结果与实验值更为接近.     

Recent advances in bismuth vanadate-based photocatalysts for photoelectrochemical water splitting

Photoelectrochemical(PEC) technology is considered to be a promising approach for solar-driven hydrogen production with zero emissions. Bismuth vanadate(BiVO_4) is a kind of photocatalytic material with strong photoactivity in the visible light region and appropriate band gap for PEC water splitting.However, the solar-to-hydrogen efficiency(STH) of BiVO_4 is far away from the 10% target needed for practical application due to its poor charge separation ability. Therefore, this review attempts to summarize the strategies for improving the photocurrent density and especially hydrogen production of BiVO_4 materials through PEC techniques in the last three years, such as doping nonmetal and metal elements, depositing noble metals, constructing heterojunctions, coupling with carbon and metalorganic framework(MOF) materials to further enhance the PEC performance of BiVO_4 photoanode. This review aims to serve as a general guideline to fabricate highly efficient BiVO_4-based materials for PEC water splitting.