Self-assembled monolayers of mercaptosuccinic acid on silver and gold surfaces designed for protein binding.: Part I:: structure of the monolayer

Structure of the monolayers of mercaptosuccinic acid (MSA) on silver and gold electrodes, grown from aqueous solution, has been studied using surface enhanced Raman scattering (SERS) spectroscopy. It was found that MSA chemisorbs via both sulfur atom and one carboxylic group (more close to the sulfur atom) dissociated on the Ag and Au at natural pH (slightly acidic). The influence of the type of the substrate, pH of the solution and time of incubation of the thiol monolayer have been investigated. SERS results show that acidity of one carboxylic group of MSA (more close to the sulfur) decreases on both substrates with simultaneous increase of acidity of the second COOH group, in comparison to the solution. For silver substrate, longer time of incubation is necessary to form a stable monolayer, whereas the structure of monolayer on gold does not exhibit temporal evolution. Copyright (C) 2007 John Wiley & Sons, Ltd.