In this paper, an organic−inorganic composite film of heteropolyanion was formed by attaching a Keggin-type heteropolyanion, SiW12O40 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 SiW12O40 4- and surface aminophenyl groups. X-ray photoelectron spectroscopy, scanning tunneling microscopy, and cyclic voltammetry were used to characterize the composite film. Compared with SiW12O40 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 SiW12O40 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 SiW12O40 4- ion and electrode surface, which may make it suitable for various applications in sensors and microelectronics devices.

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A novel organic-inorganic composite film was formed by attaching Keggin-type heteropolyanion, SiW 12 O 40 4¹ (devoted briefly as SiW 12 ), on a glassy carbon electrode derivatized by 4-aminophenyl group. The composite film has an ionic bonding character between SiW 12 and the surface amino group, which greatly improves the film stability and exhibits a more reversible electrochemical behavior. The modified electrode offers an excellent and stable electrocatalytic response for the reduction of nitrite. Possible mechanism was provided for the reaction of nitrite with SiW 12 O 40 4¹ /aminophenyl composite film.