Interfacial kinetic enhancement of metal ion adsorption on binary mixed self-assembled monolayers

The adsorption of metal ions, a type of surface reaction on binary mixed self-assembled monolayers (SAMs) on a gold surface composed of 1,6-hexanedithiol (HDT) with 11-mercaptoundecanoic acid (MUA), was monitored by in situ surface plasmon resonance (SPR) measurements. The differential SPR reflectance (ΔR) enables the kinetics of adsorption of Pt2+ on the mixed SAMs to be investigated. Unlike single HDT SAM, kinetic analyses of the mixed SAMs showed that the rate of adsorption of Pt2+ was enhanced and that it was highly dependent on the fraction of MUA present. These SPR measurements suggest that the adsorption rate of metal ions can be readily manipulated simply by using mixed SAMs.