Stripping chronopotentiometric analysis of cysteine on nano-silver coat polyquercetin–MWCNT modified platinum electrode

Silver nanoparticles coat polyquercetin (Qu) and multi-walled carbon nanotube (MWCNT) complex films were prepared using an electrochemical coupling strategy on platinum electrode (Ag/Qu/MWCNT/Ch/Pt). The new composite material was characterized by means of field emission scanning electron microscopy, X-ray photoelectron spectroscopy spectra, X-ray diffraction, and electrochemical techniques, which confirmed that polyquercetin plays an important role to obtain a great deal of uniformly dispersed silver nanoparticles and MWCNT complex film with a diameter of 10 ± 6 nm. The resulting Ag/Qu/MWCNT/Ch/Pt electrode shows a significant electrocatalysis for the redox of cysteine (CysH). The stripping chronopotentiometric analysis of CysH has been successfully used with a satisfying effect. A linear range of 1 × 10⁻¹⁰ to 9 × 10⁻⁸ M was obtained with a detection limit of 3 × 10⁻¹¹ M (3σ) and sensitivity of 35 μA/nM. The films were also robust, surviving up to 100 consecutive cyclic voltammograms and sonication.     

Thickness shear mode quartz crystal resonators with optimized elliptical electrodes

Quartz crystal resonators (QCRs) with circular electrodes have been widely used for various liquid and gas sensing applications. In this work,quartz crystal resonators with elliptical electrodes were studied and tested for liquid property measurement. Mindlin’s theory was used to optimize the dimension and geometry of the electrodes and a 5-MHz QCR with minimum series resistance and without any spurious modes was obtained. A series of AT-cut QCRs with elliptical electrodes of different sizes were fabricated and their sensing performances were compared to devices with circular electrodes. The experimental result shows that the device with elliptical electrodes can obtain lower resonance impedance and a higher Q factor,which results in a better loading capability. Even though the sensitivities of devices with elliptical and circular electrodes are found to be similar,the sensor with elliptical electrodes has much higher resolution due to a better frequency stability. The study indicates that the performance of QCRs with elliptical electrodes is superior to that of traditional QCRs with circular electrodes.     

杀螟丹中间体与异构体互变[JZ]异构理论研究

研究了合成杀虫剂杀螟丹的关键中间体2-N,N-二甲胺基-1,3-二硫氰基丙烷(有效体)及其异构体1-N,N-二甲胺基-2,3-二硫氰基丙烷(无效体)互变异构反应中溶剂和温度的影响. 采用密度泛函理论B3LYP/6-31G(d)方法研究了其在气相中的反应机理, 确定了相应的过渡态和反应活化能. 量子化学计算结果表明, 反应首先通过分子内亲核取代环化生成吖丙啶鎓盐活性中间体, 硫氰基进攻N-三元环中间体过程中发生了分子内重排转位, 转化为异构体. 采用极化连续(Polarizable continuum model, PCM)模型研究了反应体系在甲苯、氯仿、丙酮、乙醇、甲醇、乙腈和DMSO溶液中的溶剂效应. 结果表明, 该重排反应溶剂化效应非常明显, 极性溶剂有利于过渡态的稳定, 降低反应活化能, 提高反应速率. 理论研究结果与实验观察结果相符, 很好地解释了有关实验现象.     

Electrochemical behaviors and determination of melamine in neutral and acid aqueous media

The electrochemical behaviors of melamine (MEL) were studied at paraffin-impregnated graphite electrode in PBS (pH 7.0) and 0.5 M H₂SO₄. Various methods including UV–vis thin-layer spectroelectrochemistry, infrared spectra (IR) and electrochemicatry have been performed to investigate the characteristics. In 0.1 M PBS (pH 7.0), MEL loses two electrons to form a dication, which couples head-to-head with a neutral molecule of MEL to form a dimer accompanying the production of azocompound, the dimer plays a role of a monomer in the following polymerization. In 0.5 M H₂SO₄, unstable MEL mostly hydrolyzes to form ammeline, ammelide, s-triazine-2,4,6-trion, and tricyanic acid, respectively; The hydrolysis could be accelerated by electrochemical method; Meanwhile, MEL associates tricyanic acid to give a plane molecule cake by hydrogen bonding. The spectra responses of MEL at 205 and 234 nm are linearly increasing in a same concentration range of 1.0 × 10⁻⁷–1.0 × 10⁻⁵ M in 0.5 M H₂SO₄ (determination limit, 1 × 10⁻⁸ and 3 × 10⁻⁸ (3σ)). The proposed method was successfully applied to the determination of MEL in real sample.

     

Synthesis and QSAR studies on 1-[(5-substituted-1,3,4-thiadiazol-2-yl)methyl]-1H-1,2,4-triazole as antifungal agents

A series of 1-[(1,3,4-thiadiazol-2-yl)methyl]-1H-1,2,4-triazole derivatives were prepared and evaluated for their antifungal activities. The chemical structures of these compounds were determined by means of elemental analyses, ¹H NMR, and X-ray crystallography. Quantitative structure–activity relationship (QSAR) studies were performed on these compounds using physicochemical parameters as independent parameters and antifungal activity as a dependent parameter, where antifungal activity correlated best (r > 0.9) with hydrophobic parameters (π) and indicator (H). Moreover, the results are interpreted on the basis of a multiple regression model. The model has been internally and externally validated. Furthermore, the domain of applicability which indicates the area of reliable predictions is defined.     

A quantitative structure-activity relationship study of antifungal analogues of 3,4-substituted 5-((1H-1, 2, 4-triazol-1-yl)methyl)-4H-1,2,4-triazole

A series of 5-((1H-1, 2, 4-triazol-1-yl)methyl)-4H-1,2,4-triazole derivatives were prepared and evaluated for their antifungal activities. Quantitative structure–activity relationship studies were performed on these compounds using physicochemical parameters as independent parameters and antifungal activity as a dependent parameter, where antifungal activity correlated best (correlation coefficient r > 0.8) with physicochemical parameters (Hammett’s constants σ _p , F) and van der Waals volume V ₁. Results are interpreted on the basis of multiple regression and cross-validation methodology. Furthermore, the domain of applicability which indicates the area of reliable predictions is defined. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Chemical structures of A1–26 and A39; synthetic procedures; synthesis schemes; mps, yields, ¹H NMR; elemental analyses of compounds and single crystal X-ray diffraction of compounds.     

新型邻甲酰胺基间苯二甲酰胺类化合物的 设计合成及生物活性

以氯虫酰胺结构为基础,设计合成了一系列新型邻甲酰胺基间苯二甲酰胺类化合物,所有化合物均通过核磁共振氢谱和高分辨质谱表征确定.初步的生物活性测试结果表明,在浓度为200 mg/L时,化合物8d的杀粘虫活性可达60％;在浓度为50 mg/L时,化合物8d对苹果轮纹病菌的抑菌率为41.7％,化合物8a对小麦赤霉菌的抑菌率为4...     

Electrodeposition of Silver Nanoparticles on MWCNT Film Electrodes for Hydrogen Peroxide Sensing

Silver （Ag） nanoparticles were directly electrodeposited on multi-walled carbon nanotubes （MWCNT） in AgNO3/LiNO3 containing EDTA （ethylenediaminetetraacetic acid）. The structure and nature of the resulting Ag/MWNT composite were characterized by field emission scanning electron microscopy （FE-SEM）, transmission electron microscopy （TEM） and X-ray diffraction （XRD）, and the distribution shape of Ag nanoparticles was found to be dependent on the presence of EDTA. The modified electrode showed excellent electrocatalytic activity to redox reaction of hydrogen peroxide and the mechanism of hydrogen peroxide was partly reversible procession with oxidation and reduction peaks at 0.77 and -0.83 V, respectively. The oxidation and reduction peak currents were linearly related to hydrogen peroxide concentration in the range of 1×10^-6-3×10^-4 and 1 ×10^-8-7× 10^-4 mol·L^-1 with correlation coefficients of 0.996 and 0.986, and 3s-detection limit of 9 × 10^-7 and 7 × 10^-9 mol·L^-1.     

Ultrasonic preparation of tetraoxalyl ethylenediamine melamine resin-coated multiwalled carbon nanotubes for trace Ni(II) sensing

Under an aid of ultrasonic, tetraoxalyl ethylenediamine melamine resin-coated multiwalled carbon nanotubes were prepared for Ni(II) sensing in aqueous solution. The processes involved the fabrication of tetraoxalyl ethylenediamine melamine resin by one pot way, the coating of tetraoxalyl ethylenediamine melamine resin at multiwalled carbon nanotubes (MWCNTs), and the determination of Ni(II). The present materials were carefully examined by Fourier transform infrared spectroscopy, field emission scanning electron microscope, and electrochemistry techniques. A great deal of amorphous microsphere could be observed for tetraoxalyl ethylenediamine melamine resin with an average diameter of 1.2 μm, and MTE could evenly adhere at the surface of MWCNTs by the ultrasonic. Tetraoxalyl ethylenediamine melamine resin-coated multiwalled carbon nanotube-modified paraffin-impregnated graphite electrode was successfully used for the determination of Ni(II) by differential pulse adsorptive anodic stripping voltammetry. The current responses (?0.3 V) were linearly increased depending on the concentration from 1?×?10^?11 to 3?×?10^?10 M (i (μA)?=?11.1?+?7.9 c (1?×?10^?12 M); R?=?0.9901, 3σ?=?7?×?10^?12 M).     

基于亲电/亲核反应描述符的气体介质绝缘强度预测

研究分子微观参数与气体介质绝缘强度的关联,可为SF₆替代气体筛选提供方向.本文基于密度泛函理论,采用M06-2X泛函与def2系列基组,计算了73种气体分子的亲电/亲核反应描述符,包括轨道能量参数、概念密度泛函理论的参数、不同电子概率密度等值面的静电势参数等;分析了各描述符与气体介质绝缘强度的相关性,以及描述符的独立性,最终提出了绝缘强度预测模型.最低空轨道能量、正负静电势表面积、静电势平均偏差、简缩局部亲电指数最小值与绝缘强度相关性较强,且彼此间相关性较低.预测模型在电子概率密度0.0002 a.u.时精度最优,其可决系数R²为0.809,均方误差MSE为0.096.