Electrochemical Modification of Gold Electrodes with Azobenzene Derivatives by Diazonium Reduction |
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Authors: | Elo Kibena Dr. Margus Marandi Dr. Uno Mäeorg Luna B. Venarusso Dr. Gilberto Maia Dr. Leonard Matisen Dr. Aarne Kasikov Prof. Väino Sammelselg Dr. Kaido Tammeveski |
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Affiliation: | 1. Institute of Chemistry, University of Tartu, Ravila 14a, 50411 Tartu (Estonia), Fax: (+372)?7375181;2. Department of Chemistry, Universidade Federal de Mato Grosso do Sul, Caixa Postal 549, Campo Grande, MS 79070‐900 (Brazil);3. Institute of Physics, University of Tartu, Riia 142, 51014 Tartu (Estonia) |
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Abstract: | An electrochemical study of Au electrodes electrografted with azobenzene (AB), Fast Garnet GBC (GBC) and Fast Black K (FBK) diazonium compounds is presented. Electrochemical quartz crystal microbalance, ellipsometry and atomic force microscopy investigations reveal the formation of multilayer films. The elemental composition of the aryl layers is examined by X‐ray photoelectron spectroscopy. The electrochemical measurements reveal a quasi‐reversible voltammogram of the Fe(CN)63?/4? redox couple on bare Au and a sigmoidal shape for the GBC‐ and FBK‐modified Au electrodes, thus demonstrating that electron transfer is blocked due to the surface modification. The electrografted AB layer results in strongest inhibition of the Fe(CN)63?/4? response compared with other aryl layers. The same tendencies are observed for oxygen reduction; however, the blocking effect is not as strong as in the Fe(CN)63?/4? redox system. The electrochemical impedance spectroscopy measurements allowed the calculation of low charge‐transfer rates to the Fe(CN)63? probe for the GBC‐ and FBK‐modified Au electrodes in relation to bare Au. From these measurements it can be concluded that the FBK film is less compact or presents more pinholes than the electrografted GBC layer. |
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Keywords: | diazo compounds electrochemistry electron transfer gold electrode oxygen reduction |
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