Electrochemical behavior of polycrystalline gold electrode modified by thiolated calix[4]arene and undecanethiol
Abstract
The electrochemical behavior of polycrystalline gold electrode (PAuE) modified by self-assembled monolayers (SAMs) of thiolated calix[4]arene (C4A) and undecanethiol (C11) was investigated by voltammetric methods and electrochemical impedance spectroscopy. Coverage of the thiol SAMs and their stability was tested.
The C11 layer is very stable; the desorption peak was recorded only in basic solutions of pH 12 and higher (at -1.30 V vs. Ag vertical bar AgCl (3 mol L-1 KCl)).
The position of the C4A desorption peak is more pH dependent and it was recorded at -1.08 V at pH 13. Molecular coverage for C4A and C11 SAMs modified PAuE is 364 +/- 52.9 mu C cm(-2) and 137 +/- 20.0 mu C cm(-2) respectively.
The properties of the PAuE modified by C11 and/or C4A were investigated using the model compounds hydroquinone, ferrocene and potassium ferrocyanide. It is assumed that the oxidation of the hydroquinone cannot be realized inside the C4A cavity because the hydroquinone molecule is too big to enter the cavity.
Similar behavior was observed using potassium ferrocyanide. In contrast, cyclic voltammograms of ferrocene oxidation were only negligibly affected by the electrode modification.
Moreover, capacitance measurements proved accumulation of ferrocenium ions at the C4A modified electrode.