Electrochemical Preparation and Characterization of Silicotungstic Heteropolyanion Monolayer Electrostatically Linked Aminophenyl on Carbon Electrode Surface

In this paper, an organic−inorganic composite film of heteropolyanion was formed by attaching a Keggin-type heteropolyanion, SiW 12 O 40 4 -, on carbon electrode surface derivatized by 4-aminophenyl monolayer. The composite film thus grafted on carbon electrode surface has good stability because of the ionic bonding character between SiW 12 O 40 4 - and surface aminophenyl groups. X-ray photoelectron spectroscopy, scanning tunneling microscopy, and cyclic voltammetry were used to characterize the composite film. Compared with SiW 12 O 40 4 - electrodeposited on a bare glassy carbon electrode (GCE), the composite film gives three more sharp and well-defined redox couples attributed to two one- and two-electron processes, and the analyses of the voltammograms of SiW 12 O 40 4 - anion in the composite film modified on GCE shows that its surface coverage is close to a closest packing monolayer. STM characterization shows that a two-dimensional order heteropolyanion monolayer was formed on HOPG substrate. The composite film provides a favorable environment for electron and proton transfer between SiW 12 O 40 4 - ion and electrode surface, which may make it suitable for various applications in sensors and microelectronics devices.