Electron Transfer to Covalently Immobilized Keggin Polyoxotungstates on Gold

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• 作者：Mustansara Yaqub ; James J. Walsh ; Tia E. Keyes ; Anna Proust ; Corentin Rinfray ; Guillaume Izzet ; Timothy McCormac ; Robert J. Forster
• 刊名：Langmuir
• 出版年：2014
• 出版时间：April 22, 2014
• 年：2014
• 卷：30
• 期：15
• 页码：4509-4516
• 全文大小：352K
• 年卷期：v.30,no.15(April 22, 2014)
• ISSN：1520-5827

文摘

Spontaneously adsorbed monolayers have been formed on gold electrodes using a Keggin polyoxotungstate with covalently attached alkanethiol linkers of two different lengths. Films of both polyoxotungstates show two well-defined reduction processes associated with the polyoxotungstate centers where the ionic liquid, [BMIM][BF₄], acts as supporting electrolyte. The surface coverages are both less than that expected for a close-packed monolayer. For the short and long linkers, the voltammetric response can be described in terms of the Butler鈥揤olmer response involving a surface confined species using standard heterogeneous electron transfer rate constants of 170 and 140 s^鈥? for the first reduction and 150 and 100 s^鈥? for the second reduction processes, respectively. The rate of electron transfer to a solution phase redox probe, ferrocyanide, is significantly more sensitive to the length of the linker than the rate of electron transfer to the tungstate centers. This behavior probably arises due to potential-induced changes in the film structure.