Electrochemical preparation and characterization of silicotungstic heteropolyanion monolayer electrostatically linked aminophenyl on carbon electrodesurface

In this paper, an organic-inorganic composite film of heteropolyanion was F ormed by attaching a Keggin-type heteropolyanion, SiW12O404-, on carbon ele ctrode surface derivatized by 4-aminophenyl monolayer. The composite film t hus grafted on carbon electrode surface has good stability because of the i onic bonding character between SiW12O404- and surface aminophenyl groups. X -ray photoelectron spectroscopy, scanning tunneling microscopy, and cyclic voltammetry were used to characterize the composite film. Compared with SiW 12O404- electrodeposited on a bare glassy carbon electrode (GCE), the compo site film gives three more sharp and well-defined redox couples attributed to two one- and two-electron processes, and the analyses of the voltammogra ms of SiW12O404- anion in the composite film modified on GCE shows that its surface coverage is close to a closest packing monolayer. STM characteriza tion shows that a two-dimensional order heteropolyanion monolayer was forme d on HOPG substrate. The composite film provides a favorable environment fo r electron and proton transfer between SiW12O404- ion and electrode surface , which may make it suitable for various applications in sensors and microe lectronics devices.