Enhanced separation performance of PVDF/PVP-g-MMT nanocomposite ultrafiltration membrane based on the NVP-grafted polymerization modification of montmorillonite (MMT)

A novel hydrophilic nanocomposite additive (PVP-g-MMT), coupling of hydrophilic modifier, self-dispersant, and pore-forming agent (porogen), was synthesized by the surface modification of montmorillonite (MMT) with N-vinylpyrrolidone (NVP) via "grafting from" polymerization in the presence of H(2)O(2)-NH(3)·H(2)O as the initiator, and then the nanocomposite membrane of poly(vinylidene fluoride) (PVDF) and PVP-g-MMT was fabricated by wet phase inversion onto clean glass plates. The existence and dispersion of PVP-g-MMT had a great role on structures, morphologies, surface composition, and chemistry of the as-prepared nanocomposite membranes confirmed by varieties of spectroscopic and microscopic characterization techniques, all of which were the correlated functions of PVP-g-MMT content in casting solution. By using the dead-end filtration of protein aqueous solution, the performance of the membrane was evaluated. It was seen that all of the nanocomposite membranes showed obvious improvement of water flux and proper BSA rejection ratio, compared to the control PVDF membrane. Meanwhile, dynamic BSA fouling resistance and flux recovery properties were also greatly enhanced due to the changes of surface hydrophilicity and morphologies. All the experimental results indicated that the as-prepared PVDF nanocomposite membranes showed better separation performances than the control PVDF membrane. Hopefully, the demonstrated method of hydrophilic nanocomposite additive synthesis would be applied for commonly hydroxyl group-containing inorganic nanoparticles, which was favorable to fabricate hydrophilic nanoparticle-enhanced polymer membranes for water treatment.     

低量镱掺杂TiO2纳米光催化剂的溶胶-溶剂热制备及光活性

利用溶胶-溶剂热技术制备了锐钛矿型Yb掺杂和未掺杂TiO2纳米粒子,以亚甲基蓝(MB)溶液在紫外光和可见光照射下的光催化脱色率评价其光活性,考察了溶剂热温度、Yb掺杂量和焙烧温度对样品光活性的影响;结合XRD,BET,XPS,FT-IR,DRS和PL表征手段,探讨了Yb掺杂对TiO2光活性的影响机制.结果表明,低量Yb掺杂不仅显著提高TiO2的紫外光活性,也明显提高其可见光活性.Yb掺杂调整TiO2带隙内部电子分布状态,有效抑制光生e-/h+复合,提高量子效率;并且增加表面羟基,增大比表面积,改善表面织构特性,致使紫外光活性提高.然而Yb掺杂并未引起紫外吸收带边红移,其可见光活性的提高应归因于Yb掺杂强化了表面吸附染料的敏化作用.     

二维纳米材料g-C3N4在电化学发光中的应用研究

电化学发光(ECL)兼备电化学和化学发光的特点,灵敏度高、线性范围宽、背景干扰小,得到了广大分析科学研究者的关注;传统的ECL材料虽然发光效率高,但仍存在价格昂贵、负载量低等缺点。g-C₃N₄是一种不含金属的半导体纳米材料,主要以三嗪环或七嗪环为基本结构单元,通过层间的范德华力以及层内的C—N共价键结合,构成类石墨的二维层状结构,具有性质稳定、能带结构独特、生物兼容性好、环保无毒、易于功能化、原料价廉、制备过程简单等优点。自2012年g-C₃N₄首次被发现具备ECL的性能,至今已被广泛应用到ECL中。本文根据ECL的发光机理、传感器的作用效果、传感的信号类型以及不同的检测对象进行了分类,综述了近年来g-C₃N₄在ECL传感器构建中的研究进展,并阐述了g-C₃N₄在ECL发展中存在的挑战和前景。     

Synthesis,Structures, and Properties of Lanthanide Complexes with Pyrimidine‐2‐carboxylic Acid

Six lanthanide complexes [Ln(pmc)₂NO₃]_n [Hpmc = pyrimidine‐2‐carboxylic acid, Ln = La ( 1 ), Pr ( 2 )], [Ln(pmc)₂(H₂O)₃]NO₃ · H₂O [Ln = Eu ( 3 ), Tb ( 4 ) Dy ( 5 ), Er ( 6 )] were synthesized by the reactions of lanthanide nitrate and pyrimidine‐2‐carboxylic acid in water at room temperature. These complexes were characterized by single‐crystal X‐ray diffraction analysis, elemental analysis, IR, circular dichroism (CD) and fluorescence spectra. Structure analysis shows that complexes 1 and 2 are isostructural with P4₃2₁2 space group, whereas isostructural complexes 3 – 6 belong to the P2₁/c space group. In complexes 1 and 2 , the central metal atoms are coordinated by nitrates and pmc^–, which are self‐assembled to construct a 3D porous network with 6₂.6₂.6₂.6₂.6₂.6₂ (6⁶) topology. In complexes 3 – 6 , H₂O and pmc^– ligands are coordinated and the complexes exhibit a one‐dimensional zigzag chain, which is further expanded into a 3D structure by hydrogen bonding. In addition, the circular dichroism of 1 and 2 proves that the two complexes are both chiral with achiral ligand of Hpmc. Luminescent measurements of compounds 3 – 5 indicate that the characteristic fluorescence of Eu³⁺, Tb³⁺, and Dy³⁺ are observed.     

蚱蝉听觉中间神经元对声信号特征编码的电生理研究

本文首次报道蚱蝉听觉系统中放电模式不同的两类中间神经元的阈值-频率关系曲线,及它们对声刺激信号的强度与时间特征的编码方式.它们的功能可能分别是简易的声强与时间编码器和声脉冲标记器.     

循环载荷下淤泥轻量土的细观变形机理研究1)

基于新型室内固结试验及有限元数值模拟分析方法,研究了淤泥轻量土在循环载荷作用下的细观多相变形机理及其宏、细观变形特性之间的相互关系。结果表明,EPS(expanded polystyrene)颗粒掺量及其粒径大小对淤泥轻量土的细观变形特性有显著的影响。试验发现,在所选用的配合比中EPS掺量相差2.0%时,而淤泥轻量土最大体积变形量却相差了4.1%。在相同循环次数下,试样中上、中、下三个点位的EPS颗粒变形量及其应力应变大小关系并不相同,上点位的EPS颗粒变形量最大。通过对不同循环周期下淤泥轻量土各相细观变形关系定量计算分析发现,EPS颗粒变形量在其整个变形过程中占主导地位,平均占到约60%$\sim$80%。该研究可为后续有关EPS淤泥轻量土的微细观结构之间多相耦合作用的研究及其在软土路基填土工程中的应用提供一定的理论支持。     

Bijective soft set decision system based parameters reduction under fuzzy environments

Gong et al. (2010) and Xiao et al. (2010) have proposed the notion of bijective soft set and exclusive disjunctive soft set, respectively, which is a subtype of soft set. On the basis of their work, this paper extends these notions to fuzzy environments, and formulates the concept of bijective fuzzy soft set, which can deal with more uncertain problems. Moreover, this paper proposes two parameters reduction algorithms: one (Algorithm 1) is based on bijective fuzzy soft system, and the other (Algorithm 2) takes weight of an element into consideration. Since the threshold plays an important role in these algorithms, we proposed an algorithm (Algorithm 3) to decide the optimal value of threshold specially. Afterwards, an example analysis of the two parameters reduction algorithms is given and the result shows that the two algorithms lead to the same parameters reduction of a bijective fuzzy soft system. Since Algorithm 2 considers the detail weights of elements, thus it can be used in more uncertain problems, such as time series analysis problems, than Algorithm 1.     

Correction to: In Silico Structure-Based Identification and Validation of Key Residues of Vip3Aa Involving in Lepidopteran Brush Border Receptor Binding

Applied Biochemistry and Biotechnology - The original version of this article unfortunately contained a mistake. The missing acknowledgement is provided below.     

TEMPO-catalyzed oxidative dimerization and cyanation of indoles for the synthesis of 2-(1H-indol-3-yl)-3-oxoindoline-2-carbonitriles

A method for the combinative oxidative homo dimerization and cyanation of free indole derivatives catalysed by TEMPO along with silver carbonate was demonstrated for the first time This new methodology is both atom and step efficient and is applicable to a broad scope of substrates, allowing the synthesis of a range of synthetically valuable 2-(1H-indol-3-yl)-3-oxoindoline- 2-carbonitriles in moderate to excellent yields. Furthermore, selected compounds 6b and 6g exhibit moderate to good anti-schistosomicidal activities.     

Metal-free catalytic enantioselective silylation of aromatic aldehydes in water

One-step access to chiral α-hydroxysilanes by metal-free catalytic enantioselective silylation of aromatic aldehydes in water was achieved for the first time.