Fabrication and morphology control of hollow polymer particles by altering core particle size

Particles with various morphologies were fabricated by changing the size of carboxyl-containing core particles and performing seeded emulsion polymerization as well as alkali posttreatment. The distribution of carboxyl groups, size, and morphology of the resultant particles were characterized with conductometric titration, dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Results indicated that the size of carboxyl-containing core latex particles could be varied from 95 to 240 nm by adjusting the concentration of sodium dodecyl sulfate (SDS). The percentage of carboxyl groups buried inside particles increased clearly along with the encapsulation of core by interlayer and shell polymers, and seeded emulsion copolymerization performed smoothly except the system using core particles with size less than 99 nm. After alkali posttreatment, the morphologies of corresponding particles showed porous, hollow, and bowl-like structure, respectively. Moreover, the relationship between core particle size and alkali-treated particle morphology was elucidated briefly.     

Effect of Monomer Feeding Mode on thePreparation of Hollow Latexes with High MAA Content in the Core Latex Preparation简

In order to prepare hollow latex particles with optimum morphology based on osmotic swelling principle, three- layer core/shell latex particles with 40 wt% MAA in the core were first prepared via multistep seeded emulsion copolymerization, in which monomers were added by a semi-continuous process with monomer addition under two different forms： pure monomers＇ mixture （monomer addition）, and pre-emulsified monomers （pre-emulsion addition）. Then, the hollow latex particles with different morphologies were obtained after alkali post-treatment. Influences of the monomer feeding mode on the emulsion polymerization and the particle morphology were investigated. Results showed that the pre- emulsion addition could significantly improve the polymerization stability in each step, and greatly enhance the uniformity of shell encapsulation. The sizes of the core and core/shell latex particles obtained by the pre-emulsion addition were smaller and more uniform than those synthesized by the monomer addition, and the hollow latex particles with intact morphology were generated by alkali post-treating of the core/shell latexes prepared from the pre-emulsion addition. As the core size increased, the morphology of the post-treated particles underwent evolution from hollow to collapse. Moreover, the mechanism of the particle morphological evolution was proposed.     

Tunable thin-film filter with low angle sensitivity

Conventional angle-tuned thin-film filters have serious angle sensitivity for their low spacer effective refractive index, and it is difficult to fabricate their angle control system. In this paper, we propose and fabricate a novel 100 GHz angle-tuned thin-film filter stack with low angle sensitivity, which uses the high refractive index material TiO2 as the spacer, and its incident angle can be expanded to 25°. Compared with the traditional Ta2O5-SiO2 thin-film filter stack, the novel stack has fewer layers. Using the polarization beam splitters and the half wave plates, the polarization sensitivity of the angle-tuned filter can also be suppressed. Simulation results and the experiments show that the thin-film filter with low angle sensitivity has an effective tuning range of 33 nm, which can cover the whole C-band, and its angle control system is easy to be fabricated.     

基于BP神经网络的传感器网络动态采样模型研究

能耗控制对于农业环境监测无线传感器网络系统具有重要意义。基于误差反向传播的多层前馈神经网络预测和阈值分析建立了一种土壤温度传感器网络动态采样模型,实现了基于土壤温度周期变化特征的采样频率实时调整方法,达到减少网络冗余数据,降低网络功耗的目的。以环境温度和空气相对湿度为BP神经网络实测输入,土壤温度为预测输出,通过判断输出是否进入阈值区间动态调整采样周期。仿真实验结果表明,对于具有周期性特点的土壤温度,BP网络模型对其预测值和实测值之间的均方根误差RMSE及绝对误差AE分别为0.83℃和0.54℃。相比于连续采样,阈值分析动态采样次数减少30%。     

After the electronic field: Structure,bonding, and the first hyperpolarizability of HArF

In this work, we add different strength of external electric field (E_ext) along molecule axis (Z‐axis) to investigate the electric field induced effect on HArF structure. The H‐Ar bond is the shortest at E_ext = ?189 × 10^?4 and the Ar‐F bond show shortest value at E_ext = 185 × 10^?4 au. Furthermore, the wiberg bond index analyses show that with the variation of HArF structure, the covalent bond H‐Ar shows downtrend (ranging from0.79 to 0.69) and ionic bond Ar‐F shows uptrend (ranging from 0.04 to 0.17). Interestingly, the natural bond orbital analyses show that the charges of F atom range from ?0.961 to ?0.771 and the charges of H atoms range from 0.402 to 0.246. Due to weakened charge transfer, the first hyperpolarizability (β_tot) can be modulated from 4078 to 1087 au. On the other hand, make our results more useful to experimentalists, the frequency‐dependent first hyperpolarizabilities were investigated by the coupled perturbed Hartree‐Fork method. We hope that this work may offer a new idea for application of noble‐gas hydrides. © 2013 Wiley Periodicals, Inc.     

硫与Mn2O3空心球的复合结构及其在锂硫电池中的应用

在水热条件下,以碳球为模板合成了Mn₂O₃空心球,并用作锂硫电池的载硫基底材料。测试结果表明载硫量为51%的Mn₂O₃-S复合材料显示了较高的比容量,良好的循环稳定性和倍率性能。循环100圈后,最终可逆容量仍保持657 mA·g^-1,证明该Mn₂O₃空心球是一种有潜力的载硫基底材料。     

Straightforward Oxidation of a Copper Substrate Produces an Underwater Superoleophobic Mesh for Oil/Water Separation

A superhydrophilic and underwater superoleophobic Cu(OH)₂‐covered mesh with micro‐ and nanoscale hierarchical composite structures is successfully fabricated through a one‐step chemical oxidation of a smooth‐copper mesh. Such mesh, without any further modification, can selectively separate water from oil/water mixtures with high separation efficiency, and possess excellent stability even after 60 uses. This method provides a simple, low‐cost, and scalable strategy for the purification of oily wastewater.     

Phase‐Transfer‐Catalyzed Asymmetric Synthesis of Axially Chiral Anilides

Catalytic asymmetric synthesis of axially chiral o‐iodoanilides and o‐tert‐butylanilides as useful chiral building blocks was achieved by means of binaphthyl‐modified chiral quaternary ammonium‐salt‐catalyzed N‐alkylations under phase‐transfer conditions. The synthetic utility of axially chiral products was demonstrated in various transformations. For example, axially chiral N‐allyl‐o‐iodoanilide was transformed to 3‐methylindoline by means of radical cyclization with high chirality transfer from axial chirality to C‐centered chirality. Furthermore, stereochemical information on axial chirality in o‐tert‐butylanilides could be used as a template to control the stereochemistry of subsequent transformations. The transition‐state structure of the present phase‐transfer reaction was discussed on the basis of the X‐ray crystal structure of ammonium anilide, which was prepared from binaphthyl‐modified chiral ammonium bromide and o‐iodoanilide. The chiral tetraalkylammonium bromide as a phase‐transfer catalyst recognized the steric difference between the ortho substituents on anilide to obtain high enantioselectivity. The size and structural effects of the ortho substituents on anilide were investigated, and a wide variety of axially chiral anilides that possess various functional groups could be synthesized with high enantioselectivities. This method is the only general way to access a variety of axially chiral anilides in a highly enantioselective fashion reported to date.     

2‐Aminobenzenethiol‐Functionalized Silver‐Decorated Nanoporous Silicon Photoelectrodes for Selective CO2 Reduction

A molecularly thin layer of 2‐aminobenzenethiol (2‐ABT) was adsorbed onto nanoporous p‐type silicon (b‐Si) photocathodes decorated with Ag nanoparticles (Ag NPs). The addition of 2‐ABT alters the balance of the CO₂ reduction and hydrogen evolution reactions, resulting in more selective and efficient reduction of CO₂ to CO. The 2‐ABT adsorbate layer was characterized by Fourier transform infrared (FTIR) spectroscopy and modeled by density functional theory calculations. Ex situ X‐ray photoelectron spectroscopy (XPS) of the 2‐ABT modified electrodes suggests that surface Ag atoms are in the +1 oxidation state and coordinated to 2‐ABT via Ag?S bonds. Under visible light illumination, the onset potential for CO₂ reduction was ?50 mV vs. RHE, an anodic shift of about 150 mV relative to a sample without 2‐ABT. The adsorption of 2‐ABT lowers the overpotentials for both CO₂ reduction and hydrogen evolution. A comparison of electrodes functionalized with different aromatic thiols and amines suggests that the primary role of the thiol group in 2‐ABT is to anchor the NH₂ group near the Ag surface, where it serves to bind CO₂ and also to assist in proton transfer.     

Antioxidant Properties of Bio-active Substances from Shrimp Head Fermented by Bacillus licheniformis OPL-007

Antioxidative activities were found in the culture supernatant of Bacillus licheniformis OPL-007 using shrimp head waste (SHW) as the sole carbon and nitrogen source. After optimizing fermentation conditions, some bio-active substances were determined from the broth. The contents of total phenols, polysaccharides, reducing sugars, free amino acids, and organic acids were 888.80, 402.74, 85.88, 2,061.79, and 5,426.74 mg/l, respectively. Moreover, the fermentation liquid was found rich in eight essential amino acids and non-protein amino acids. The antioxidant activity of the culture supernatant, in terms of the scavenging activity of DPPH radicals, reducing power, and metal chelating ability, was monitored, and the fermentation liquid showed a strong antioxidant capacity. The results indicate that bio-deproteinization of SHW by B. licheniformis OPL-007 can increase its antioxidant activity, and SHW has the potential application in the production of functional foods.