Ferrocene-terminated alkanethiol self-assembled monolayers: An electrochemical and in situ surface-enhanced infra-red absorption spectroscopy study

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• 作者：Alex ; er V. Rudnev ; Ulmas Zhumaev ; Toru Utsunomiya ; Chunjie Fan ; Yasuyuki Yokota ; Ken-ichi Fukui ; Thomas W ; lowski
• 关键词：Self-assembled monolayer ; Ferrocene ; Alkanethiol ; Infrared spectroscopy ; SEIRAS ; Cyclic voltammetry
• 刊名：Electrochimica Acta
• 出版年：2013
• 出版时间：30 September, 2013
• 年：2013
• 卷：107
• 期：Complete
• 页码：33-44
• 全文大小：3136 K

文摘

The effect of anions on the redox behavior and structure of 11-ferrocenyl-1-undecanethiol (FcC₁₁) monolayers (SAM) on Au(1 1 1) single crystal and Au(1 1 1-25 nm) thin film electrodes was investigated in 0.1 M solutions of HPF₆, HClO₄, HBF₄, HNO₃, and H₂SO₄ by cyclic voltammetry (CV) and in situ surface-enhanced infrared reflection-absorption spectroscopy (SEIRAS). We demonstrate that the FcC₁₁ redox peaks shift toward positive potentials and broaden with increasing hydrophilicity of the anions. In situ surface-enhanced IR-spectroscopy (SEIRAS) provided direct access for the incorporation of anions into the oxidized adlayer. The coadsorption of anions is accompanied by the penetration of water molecules. The latter effect is particularly pronounced in aqueous HNO₃ and H₂SO₄ electrolytes. The adlayer permeability increases with increasing hydrophilicity of the anions. We also found that even the neutral (reduced) FcC₁₁ SAM is permeable for water molecules. Based on the property of interfacial water to reorient upon charge inversion, we propose a spectroscopic approach for estimating the potential of zero total charge of the FcC₁₁-modified Au(1 1 1) electrodes in aqueous electrolytes.