Elimination Voltammetry as a New Method for Studying the SAM Formation

摘要

In this paper we present the electrochemical study of self-assembled monolayer (SAM) created ofaliphatic 1-hexadecanethiol (1-HDT) molecules adsorbed onto the gold and Au/Cr QCM crystalsurfaces. We investigated the influence of 1-HDT concentration and scan rate on potential values forboth adsorption and desorption processes. Our study introduces elimination voltammetry with linearscan (EVLS) as a new, improved and sufficient approach to study and characterize the SAM creation.Furthermore, formation of SAM was studied by cyclic voltammetry, electrochemical quartz crystalmicrobalance (QCM) and atomic force microscopy (AFM). Our study showed that the EVLS issuitable method for SAM study and gave detail information about the processes on the electrodesurface. It was found that the adsorption of 1-HDT molecules on QCM crystal was more extensivethan on Au electrode, i.e. molecules of 1-HDT molecules had better coverage on QCM crystal. Theincomplete desorption of previously adsorbed 1-HDT from the electrode surface was observed byQCM measurements. AFM measurements confirmed that created SAM was homogenous withoutdefects. The application of EVLS to the voltammetric signals resulted in significant increase of peakheight and revealed a kinetically controlled reaction before an electron transfer proceeding in adsorbedstate for oxidation processes corresponding to the 1-HDT monolayer adsorption and dithiol formationon both electrodes. A kinetically controlled reaction was detected also before the reductive desorptionof previously adsorbed 1-HDT on both the electrodes.