Electrochemical Quartz Crystal Microbalance Study of the Behaviour of Bis(2,2--Bipyridyl)Copper(II) Complex Immobilized on a Self-Assembled Monolayer Modified Gold Electrode

Abstract

Modification of a gold electrode of an electrochemical quartz crystal microbalance (EQCM) has been achieved by immobilizing a bis(2,2--bipyridyl)copper(II) complex on a self-assembled monolayer (SAM) of 1-mercapto-11-undecanoic acid (MUA). The electrostatic interaction of the negatively charged SAM with a di-positive copper complex allowed the attachment. The modified electrode exhibited excellent redox behavior. Electro-statically immobilized on a SAM gold modified electrode is reported. A carboxylic acid terminated monolayer was utilized to provide a chemically uniform surface. The dependence of the modified electrode response was investigated in terms of pH, supporting electrolyte and ionic strength. X-ray photoelectron spectroscopy (XPS) was also employed to study the chemical interactions between bis(2,2--bipyridyl)copper(II) and 1-mercapto-11-undecanoic acid (MUA). XPS provides identification of the sorption sites involved in the accumulation of bis(2,2--bipyridyl)copper(II), as well as the forms of species sorbed on the self-assembled monolayer. It is found that sorption occurs on carboxlic functional groups.