Nonradiative energy transfer study on the interface of compatibilized linear low density polyethylene/poly(methyl methacrylate) blends

Blends of chromophore-labeled LLDPE and chromophore-labeled PMMA compatibilized by block copolymer of hydrogenated polybutadiene and methyl methacrylate (PHB-b-PMMA) were studied by nonradiative energy transfer (NRET) technique. The ratio of fluorescence intensity of the donor at 336 nm and the acceptor at 408 nm (I-D/I-A) decreased with an increase in block copolymer content. At about 8 wt.-% block copolymer content I-D/I-A reached a minimum value, indicating the interdiffusion of LLDPE chains and PMMA chains in the interface is strongest. The influence of temperature on the interdiffusion of polymer chains in the interface was also examined. Samples quenched in liquid nitrogen from 140 degrees C showed lower energy transfer efficiencies than those annealed from 150 degrees C to room temperature.

Electrochemical investigation of DNA adsorbed on conducting polymer modified electrode

Detection of DNA is a very important task for molecular biology and biomedical field. We have investigated electrochemical behavior of double-stranded DNA and single-stranded DNA adsorbed on conducting polymer modified electrode in presence of cobalt complex. The possibility of using such electrode as gene detector is discussed.

Luminescence properties of the Langmuir-Blodgett film of terbium(III) stearoylanthranilate

Terbium(III) stearoylanthranilate has been prepared as a high property Z-type Langmuir-Blodgett (LB) film on various substrates by a vertical transfer process. The UV-visible absorption spectra and the low angle X-ray diffraction peaks have been collected in order to investigate the molecular arrangement and aggregation in the LB films. The average molecular orientation in multilayer stacking was determined by Attenuated Total Reflection Spectroscopy. The influence of the chemical environment of terbium within the LB films on the luminescence properties has been discussed. (C) 1997 Elsevier Science S.A.

Electrochemical study of the interfacial characteristics of redox-active viologen thiol self-assembled monolayers

The electrochemical behavior of the electroactive self-assembled monolayers (SAMs) of thiol-functionalized viologen, CH3(CH2)(9)V2+(CH2)(8)SH, where V2+ is a viologen group, on the gold electrodes is examined by cyclic voltammetry and electrochemical a.c. impedance. A monolayer of viologen is immobilized on the gold electrode surface via the Au-S bond and the normal potentials corresponding to the two successive one-electron transfer processes of the viologen active centers are -310 mV and -652 mV (vs. Ag/AgCl) in 0.1 mol l(-1) phosphate buffer solution (pH 6.96) respectively. These results suggest that the viologen SAMs are stable and well-behaved monolayers. The experimental impedance data corresponding to different forms of viologen group have been fitted to equivalent electrical circuits, and the surface capacitances and resistances have been given. The heterogenous electron transfer rates of the first and the second redox processes are 7.57 s(-1) and 1.49 s(-1) respectively through a.c. impedance.

AMPEROMETRIC BIOSENSORS BASED ON THE IMMOBILIZATION OF OXIDASES IN A PRUSSIAN BLUE FILM BY ELECTROCHEMICAL CODEPOSITION

Prussian blue has been formed by cyclic voltammetry onto the basal pyrolytic graphite surface to prepare a chemically modified electrode which provides excellent electrocatalysis for both oxidation and reduction of hydrogen peroxide. It is found for the first time that glucose oxidase or D-amino oxidase can be incorporated into a Prussian blue film during its electrochemical growth process. Two amperometric biosensors were fabricated by electrochemical codeposition, and the resulting sensors were protected by coverage with a thin film of Nafion. The influence of various experimental conditions was examined for optimum analytical performance. The glucose sensor responds rapidly to substrates with a detection limit of 2 x 10(-6) M and a linear concentration range of 0.01-3 mM. There was no interference from 2 mM ascorbic acid or uric acid. Another (D-amino acid) sensor gave a detection limit of 3 x 10(-5) M D-alanine, injected with a linear concentration range of 7.0 x 10(-5)-1.4 x 10(-2) M. Glucose and D-amino acid sensors remain relatively stable for 20 and 15 days, respectively. There is no obvious interference from anion electroactive species due to a low operating potential and excellent permselectivity of Nafion.

INFLUENCE OF THE SUBSTITUTION OF Y BY IN ON THE STRUCTURE AND MAGNETIC PROPERTY OF Y2CU2O5

In2CuO5 is isostructural to Y2Cu2O5 both in its crystal and magnetic structure. In and Y can be substituted by each other in any ratio to make new compounds Y2-xInxCu2O5 (x = 0-2) which were identified by XRD and IR spectrum. The structural change in Y2-x

激光光热折射光谱法测量毛细管内液体样品的微弱吸收

本工作采用毛细园柱管为样品池,证实在激光束通过毛细管不发生衍射的情况下,可采用激光光热折射光谱法进行“在线”检测。我们还提出一种通过监测第二针孔光栏产生的菲涅尔衍射条纹,提高检测灵敏度的新方法。检测了内径为300μm毛细管内1.8×10~(-16)mol的结晶紫,相应的最小吸光度为3×10~(-7)。

中国雪参挥发油成分的色谱-质谱分析

本文测定了中国雪参根中人参挥发油的含量,并用色谱-质谱联用仪分析了化学成分及百分含量。从中分离出132种化合物,初步鉴定出49种,占挥发油总量的87.73％,有28种化合物尚未见报道。

激光热透镜光度法测定痕量锑

利用He-Ne激光,观测了锑-孔雀绿络合物的激光热透镜效应。其在苯中最低检测浓度为10ng/ml Sb,测定线性浓度范围为1～120ng/ml,测定的相对标准偏差为6.5％。本方法比常规光度法的测定灵敏度高12倍,相当于吸光度3.3×10~(-4)。

快速扫描针孔法测量脉冲染料激光束直径

本文描述了一种能够快速准确地测量脉冲染料激光束直径的方法,该方法是以步进电机驱动针孔扫描,Boxcar—Computer信号处理系统做高斯拟合,精度优于5％。

时间分辨激光荧光光谱分析方法研究——Ⅱ混合稀土中铽的测定

本文介绍了利用自装的时间分辨激光荧光光谱装置对混合稀土中铽的测定方法。装置采用氮分子激光器为激发光源,Boxcar积分器为信号处理系统,选择了Tb-Sal-乙醇溶液为荧光体系,用标准加入法对样品进样行了测定。并将已知样品的测定结果与其它方法测定结果进行了比较。本法测定铽的相对标准偏差为7.4％,检出限为1.3×10~(-4)μg/ml。

石油亚砜萃取色谱法分离钪和稀土

提出以石油亚砜为固定相,硫氰酸铵和盐酸为流动相的萃取色谱法分离钪和稀土。研究了影响钪和稀土分离的条件,本体系中钪和钕的分离系数达到1.3×10~4。该方法可用于混合稀土中小量钪的分离,提取和分析。

三甲基硅烷基丙炔与五甲基二硅烷基丙炔共聚物膜及其气体透过性

研究了三甲基硅烷基丙块与五甲基二硅烷基丙块共聚物〔poly(TMSP-co-PMDSP)〕的成膜特点。poly(TMSP-co-PMDSP)膜的气体透过系数分别为:P_(O2):4×10~3～12×10~3,P_(N2):3×10~3～8×10~3和P_(CO2):2×10~4～4×10~4barrer,气体透过稳定性低,透过行为偏离第二Fick定律,过系数下降,其中溶解系数降低的比例远大于扩散系数的增加比例,在含有凝聚性气体的环境里,膜的气体透过出现表面吸附控制的特征。

平行入射式光谱电化学池的制作及分析应用

本工作制作了用于定量分析的平行入射式光谱电化学池,电极长度为2 cm,光束高度约为120μm。稳定的吸光度在较宽的浓度范围内具有良好的线性关系,最低检测限对氢醌为3×10~(-8)mol/L,而对邻甲联苯胺为2×10~(-8)mol/L。利用光谱电化学可以在四倍的多巴胺存在下测定抗坏血酸,而大量存在的抗坏血酸对多巴胺的测定无影响。