A novel hydrogen peroxide sensor based on horseradish peroxidase immobilized on colloidal Au modified ITO electrode

A novel method to fabricate a hydrogen peroxide sensor was developed by immobilizing horseradish peroxidase (HRP) on colloidal An modified ITO conductive glass support. The cleaned glass support was modified with (3-aminopropyl)trimethoxysilane (APTMS) first to yield an interface for the assembly of colloidal An. Then 15 nm colloidal Au particles were chemisorbed onto the amine groups of the APTMS. Finally, HRP was adsorbed onto the surface of the colloidal An. The immobilized HRP displayed excellent electrocatalytical response to the reduction of hydrogen peroxide. The performance and factors influencing the resulted biosensor were studied in detail. The resulted biosensor exhibited fast amperometric response (within 5 s) to H2O2. The detection limit of the biosensor was 8.0 mumol l(-1), and linear range was from 20.0 mumol l(-1) to 8.0 mmol l(-1). Furthermore, the resulted biosensor exhibited high sensitivity, good reproducibility, and long-term stability.

Synthesis and properties of soluble polyimides based on isomeric ditrifluoromethyl substituted 1,4-bis(4-aminophenoxy)benzene

A new fluorinated diamine monomer, [1,4-bis(4-amino-3-trifluoromethylphenoxy)benzene (2)], and a known isomeric analog 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (3) were synthesized. A series of organosoluble polyimides Ia-d and IIa were prepared from the diamines (2, 3) and dianhydrides (a-d) by a high-temperature one-step method. The effects of the trifluoromethyl substituents on the properties of polyimides were evaluated through the study of their soluble, thermal, optical, and gas permeability properties. Polyimides (Ia-d) had glass transition temperatures between 229 and 279 degrees C, and the temperatures at 5% weight loss ranged from 510 to 533 degrees C under nitrogen. These polyimides could be cast into flexible and tough membranes from DMAc solutions. The membranes had tensile strengths in the range of 137-169 MPa, tensile modulus in the range of 1.6-2.2 GPa and elongations at break from 11% to 14%. The polyimide la with trifluoromethyl groups ortho to the imide nitrogen exhibited enhanced gas permeability, solubility, transparency, and thermal stability compared with the isomeric polyimide IIa with the CF3 group meta to the imide nitrogen.

Preparation of CeO2 nanopartides hydrosol

CeO2 nanoparticles hydrosol was synthesized by colloidal chemical method. The optimum experiment conditions for the preparation of CeO2 nanoparticles hydrosol were discussed. The effects of pH values, the reactant concentration and temperature on peptization process were studied. TEM photos showed that the CeO2 nanoparticles were spherical in shape and the size was about 3nm. Particle size distribution was in narrow range, and no agglomerates were observed. ED images indicated that the CeO2 nanoparticles were polycrystalline structure, and some of CeO2 were monocrystal particles.

CeO_2纳米水溶胶的制备

采用胶溶法合成了纳米CeO2 水溶胶 ,探讨了合成CeO2 水溶胶的最佳实验条件 ,研究了pH值、反应物浓度、水浴温度对胶溶过程的影响。TEM分析表明 :所制备的水溶胶中的CeO2 纳米粒子呈球形 ,约 3nm ,粒径分布均匀 ,无明显团聚现象 ;ED分析表明 ,CeO2 纳米粒子为多晶结构 ,并有少量单晶结构。

High-pressure and-temperature synthesis and characterization of mixed valence perovskite oxides LaTi1-xMgxO3

Perovskite oxides LaTi1-xMgxO3 (x = 0.25, 0.5) were synthesized using high-pressure and-temperature method. LaTi0.75Mg0.25O3 is a new compound. This new synthesis route has some advantages. XRD analysis showed that the x = 0.25 sample belongs to cubic perovskite-type structure and the a = 0.5 sample belongs to orthorhombic perovskite-type structure. EPR measurement indicated that Ti ions were in mixed valence state of +3 and +4. IR measurement indicated that the vibration frequency and width of BO6 octahedron stretching vibration absorption band decreases with the increasing of x. The valence state of Ti ions can be altered by high-pressure and-temperature. (C) 2000 Elsevier Science S.A. All rights reserved.

WO_3/ZrO_2固体强酸催化剂上异丁烷/丁烯的烷基化反应Ⅱ.过渡金属的助催化作用

制备了一系列用过渡金属M (M =Pt,Co ,Ni,Mn ,Fe,Cu)活化的WO3 /ZrO2 固体强酸催化剂 ,用XRD ,DTA TG ,H2 TPR ,NH3 TPD等测定了其晶型结构、表面状态和酸量 .结果表明 ,各样品中的ZrO2 主要以T晶相存在 ,但T晶相ZrO2 所占的比例因过渡金属不同而异 ,比表面积比WO3 /ZrO2 稍有下降 ;金属Pt的引入使呈单层分散的WO3 的表面状态发生了改变 .研究了异丁烷 /丁烯烷基化反应 ,其反应活性与酸量的测定结果有对应关系 ;与WO3 /ZrO2 相比 ,M WO3 /ZrO2 上的丁烯转化率均稍有下降 ,但具有更高的i C08选择性 .从反应机理分析了添加过渡金属无显著效果的原因.

十一钼硅钴杂多蓝H_8[SiMo_(11)Co(H_2O)O_(39)]·20H_2O的合成与晶体结构

采用电解法制备了未见文献报道的杂多蓝H8[SiMo11Co（H2O）O39]·20H2O，通过X-射线衍射测定了其晶体结构，该晶体属单斜晶系，空间群P21；。晶胞参数全矩阵最小二乘法修正至中心原子Si与4个氧形成四面体结构，配原子M（M＝11／12Mo＋1／12Co）与O形成12个MO6八面体结构3个MO6共边形成4个M3O13三金属簇，4个三金属簇与SiO4四面体共角相连形成阴离子结构。

Self-assembly of the pre-formed inclusion complexes between cyclodextrins and alkanethiols on gold electrodes

A new kind of self-assembled monolayer (SAM) formed in aqueous solution through the pre-formed inclusion complexes (abbreviated CD . C-n) between alpha-, beta-cyclodextrins (CDs) and alkanethiols (CH3(CH2)(n-1)SH, n = 10, 14 and 18) was prepared successfully on gold electrodes. High-resolution H-1 NMR was used to confirm the formation of CD . C-n. X-ray photoelectron spectroscopy, cyclic voltammetry and chronoamperometry were used to characterize the resulting SAMs (denoted as M-CD . Cn). It was found that M-CD . Cn were more stable against repeated potential cycling in 0.5 M H2SO4 than SAMs of CH3(CH2)(n-1)SH (denoted as M-Cn), with a relative sequence of Mbeta-CD . Cn > Malpha-CD . Cn > M-Cn. In addition, an order of blocking the electron transfer between gold electrodes and redox couples (both Fe(CN)(6)(3-) and Ru(NH3)(6)(3+)) in solution, M-CD . C10 > M-CD . C14 > M-CD . C18, was observed. A plausible explanation is provided to elucidate some of the observations. (C) 1997 Elsevier Science S.A.

硅钨杂多酸在中孔全硅分子筛HMS上的固载及其催化性能

用十二烷基胺代替传统的季铵盐合成了中孔全硅分子筛ＨＭＳ，并将硅钨杂多酸（ＳｉＷ１２）浸渍固载在ＨＭＳ上．用ＸＲＤ，ＦＴ－ＩＲ以及ＮＨ３－ＴＰＤ等手段对ＨＭＳ及不同负载量和焙烧温度的负载催化剂进行了表征．即使在固载量为５０％的ＳｉＷ１２／ＨＭＳ中，ＳｉＷ１２仍保持其Ｋｅｇｇｉｎ结构并均匀分布在载体表面上，没有ＳｉＷ１２晶相生成．同时，在气－固相反应体系中研究了固载在ＨＭＳ上的ＳｉＷ１２在合成乙酸丁酯中的催化性能．实验结果表明，２００℃焙烧可以增强杂多酸与ＨＭＳ内表面之间的相互作用，从而使其对酯化反应活性具有一定的影响，并且固载催化剂在较低反应温度下具有较高的酯化活性，且性能稳定，有一定的应用前景.

AMPEROMETRIC DETECTION OF AMINO-ACIDS IN A FLOW-INJECTION SYSTEM WITH A NICKEL(II)-MODIFIED ELECTRODE WITH AN EASTMAN-AQ POLYMER FILM

Amperometic flow measurements were made at +0.55 V (vs. Ag/AgCl) in 0.1 mol l-1 KOH electrolyte with an Ni(II) chemically modified electrode (CME) with an Eastman-AQ polymer film. The use and characteristics of a Ni(II)-containing crystalline and polymer-modified electrode obtained by a double coating step as a detector for amino acids in a flow-injection system using reversed-phase liquid chromatography are described. The detection of these analytes is based on the higher oxidation state of nickel (NiOOH) controlled by the applied potential. The electroanalytical parameters and the detection current for a series of amines and amino acids were investigated. The use of such a CME in the flow-injection technique was found to be suitable in a solution at low pH. The linear range for glycine is 5 X 10(-6)-0.1 mol 1-1 with a detection limit of 1.0 X 10(-6) mol l-1. A 1 X 10(-4) mol 1-1 mixture of serine and tyrosine was also detected after separation on an Nucleosil C18 column.

CHRONOAMPEROMETRIC STUDIES ON MIGRATION AND DIFFUSION OF COUNTERION IN POLY(3-METHYLTHIOPHENE)

Small amplitude potential step experiments were carried out to study the counterion transfer process in oxidized poly(3-methylthiophene) (PMT) film. The results demonstrate that anion transfer process in PMT film is migration rather than diffusion. A porous metal electrode model-single hole model, which takes into account both the ionic resistance of the film and the uncompensated solution resistance, was found suitable to describe the potential step experiments. According to this model, the ionic resistivity of oxidized PMT film was calculated to be 5.0 x 10(4) OMEGA.cm, and, in turn, the diffusion coefficent of ClO4- ion in PMT film 3.7 x 10(-9) cm2/s.

高分子除湿膜的进展

高分子除湿膜是新近出现的一种气体分离膜。本文就水分子在高聚物中的透过特点和高分子除湿膜的选材进行了扼要的综述。最后介绍了国外几种已商品化的除湿组件的性能和应用。

聚(3-甲基噻吩)薄膜中对离子的迁移与扩散——计时电流法研究

在聚(3-甲基噻吩)(PMT)氧化态进行的小幅度电位阶跃计时电流实验证明,氧化态PMT膜中阴离子的传输是迁移过程,而非扩散过程.适用于该电位跃过程的模型是考虑膜离子阻抗及未补偿溶液电阻的多孔金属电极模型——单孔模型.用该迁移模型得到的PMT膜离子电阻率为5.0×10~4Ω·cm,进而求得ClO_4~-离子在膜内的扩散系数为3.7×10~(-9)cm~2/s.