Alkyl chain length effect on the horseradish peroxidase-catalytic reduction of hydrogen peroxide mediated by methylene blue at alkanethiol self-assembled monolayer electrodes

Horseradish peroxidase (HRP) catalytic reduction of H2O2 mediated by methyl ene blue (MB) at alkanethiol self-assembled monolayer electrodes (SAME) was chosen as a model to study the alkyl chain length effect on the electron t ransfer rate of MB and the electro-HRP-catalytic reduction of H2O2 in this work. Proper chain length of alkanethiol and scan rate were selected to ach ieve quasi-reversible reduction of MB. Cyclic voltammetry (CV) results show ed that the standard electron transfer rate constant of MB at SAME decrease s exponentially with the alkyl chain length of alkanethiol, meanwhile the h alf-peak potential of electroenzymocatalytic voltammogram increases linearl y with the chain length, which is consistent with the theory of Nicholson a nd Shain. The method combining diffusion mediator with SAME would provide a new way to analyze electroenzymocatalyzed reaction. (C) 1998 Elsevier Scie nce S.A. All rights reserved.