Xie Qingji

Theory and application of analytical spectroelectrochemistry with long path length spectroelectrochemical cells: Part I. Integral equation connecting the absorbance with the concentration distribution and its use in digital simulation for long path length thin layer spectroelectrochemical cells

Abstract An integral equation connecting the absorbance with the concentration distribution for analytical spectroelectrochemistry in long path length cells was derived. On the basis of the numerical integration form of the equation a finite difference model for digital simulation of the long path length thin layer spectroelectrochemical cell with a single potential step was set up. The concentration distribution at different moments determined with the technique was confirmed by theoretical results and the variation with time of the simulated absorbance curve was in agreement with that obtained by experiment, and hence the treatment can be applied for the estimation of parameter and the study of kinetics and mechanisms of electrochemical systems.

Theory and application of analytical spectroelectrochemistry with long path length spectroelectrochemical cells: Part II: non-linear regression analysis of analytical spectroelectrochemical data for estimation of electrochemical parameters

Abstract The non-linear parameter model underlying single potential step spectroelectrochemical determination of heterogeneous electron transfer rate constants with a long path length cell is presented. Based on the theoretical A — t response model, the computerized non-linear regression can be used to analyse individual spectroelectrochemical response curves to estimate parameters and study mechanisms for many true systems. The regression results of the Fe(CN)63−/Fe(CN)64− quasi-reversible response curves for estimation of the forward heterogeneous electron transfer rate constant are of high precision owing to the high optical sensitivity of the procedure. The method is rapid and accurate for parameter estimation and can be readily adapted to complex electrochemical mechanisms.

Growth and Properties of Poly-o-aminophenol Films with Three Dimensional Combinations of in situ Electrochemical Quartz Crystal Microbalance and Fourier Transform Infrared Spectroelectrochemistry

Abstract A three-dimensional combined technique, in situ quartz crystal microbalance in combination with infrared spectroscopy and electrochemistry was proposed. With this combining technique, the depositing process of poly- o -aminophenol on gold electrode surface was monitored. The oxidation and polymerization of the o -aminophenol, as well as the electrochemical properties of poly- o -aminophenol in acidic solution were investigated. Information about mass coverage of polymer, the doping/dedoping process, and change in structure of the polymer were obtained simultaneously and discussed. The results indicated that this method could be widely applied to the investigation of electrode-surface-relevant processes.

Differential linear sweep and differential cyclic voltabsorptometry in a long-path-length spectroelectrochemical cell: Eqr, Eir and ErCi′

Abstract The theory of differential linear sweep voltabsorptometry (DLSVA) and differential cyclic voltabsorptometry (DCVA) in long-path-length spectroelectrochemistry is presented for irreversible (Eir), quasi-reversible (Eqr) and ErCi′ mechanisms under conditions of semi-infinite diffusion. It is concluded that this method may be suitable for estimating electrochemical parameters because it is more sensitive than the approach using an optically transparent electrode. All the theoretical results re experimentally verified. The standard heterogeneous rate constant k s and the transfer coefficient α of two electrochemical quasi-reversible systems (methylene blue in 1.0 M HCl and indigo carmine in 0.1 M HCl) were estimated using the simplex method and good fits between theory and experiment were obtained. A system comprising K 4 Fe(CN) 6 + ascorbic acid in 0.5 M HNO 3 + 0.5 M glycine buffer was utilized to test the theory for the ErCi′ mechanism. The rate constant of the pseudo-first-order catalytic reaction was also estimated by simplex fitting. The estimated results are in agreement with experimental values.

Comparison of Enzymatic Activities and Electroactivities of Adsorbed Glucose Oxidase on Several Nanomaterial-Modified Electrodes

The quartz-crystal microbalance technique was used to monitor the adsorption of glucose oxidase (GOx) on bare Au, Au-electrodeposited Au (Aued/Au), multiwalled carbon nanotube (MWCNT)modified Au (MWCNTs/Au), and Au-electrodeposited MWCNT-modified Au (Aued/MWCNTs/Au) electrodes. The mass of GOx at saturated adsorption was obtained in each case. The amperometric responses of these enzyme electrodes were examined, and the mass-specific bioactivities of the immobilized (adsorbed) GOx (MSBAi) were evaluated through anodic potentiostatic detection of enzymatically generated H2O2 in the presence of glucose. The direct electrochemistry of adsorbed GOx was studied by cyclic voltammetry, to obtain the electroactivity percentage of the immobilized (adsorbed) GOx (EAPi) in each case. We found that the amounts of enzyme adsorbed and the amperometric responses of these enzyme electrodes follow the order GOx/MWCNTs/Au>GOx/Aued/MWCNTs/Au>GOx/Aued/Au>GOx/Au; the MSBAi values follow the order GOx/Au>GOx/Aued/MWCNTs/Au≥GOx/Aued/Au>>GOx/MWCNTs/Au; and the EAPi values follow the order GOx/MWCNTs/Au>GOx/Aued/MWCNTs/Au>>GOx/Aued/Au≥GOx/Au. The experimental data are interpreted based on hydrophobic/hydrophilic interactions among enzyme molecules and the nanomaterials, [Article] doi: 10.3866/PKU.WHXB201306042 www.whxb.pku.edu.cn 物理化学学报(Wuli Huaxue Xuebao) Acta Phys. -Chim. Sin. 2013, 29 (8), 1727-1734 August Received: March 23, 2013; Revised: June 4, 2013; Published on Web: June 4, 2013. ∗Corresponding author. Email: xieqj@hunnu.edu.cn; Tel: +86-731-88865515. The project was supported by the National Natural Science Foundation of China (21175042, 21075036), Hunan Provincial Educational Department, China (11A069), and Program for Science and Technology Innovative Research Team in Higher Educational Institutions Hunan Province, China. 国家自然科学基金(21175042, 21075036)、湖南省教育厅(11A069)和湖南省高校科技创新团队资助项目 C Editorial office of Acta Physico-Chimica Sinica 1727 Vol.29 Acta Phys. -Chim. Sin. 2013 as well as the amount of adsorbed GOx. It was also verified that the total enzymatic activity of all the electrode-adsorbed enzyme molecules is positively related to the amperometric responses of the enzyme electrodes. This work is useful in studying the immobilization of enzyme on nanomaterials and thus-prepared amperometric enzyme electrodes.