pH-dependent surface-enhanced Raman scattering studies of N-acetylalanine monolayers self-assembled on a silver surface

Monolayers of N-acetylalanine on a metallic surface can serve as a biocompatible functional interface to construct biosensors. In the present paper, the surf ace-enhanced Raman scattering (SERS) spectra of N-acetylalanine monolayers self-assembled on a silver surface under different pH were recorded. Assignments of the obtained spectra were carried out by density functional theory (DFT) calculations (BLYP/6-311G). On the basis of the SERS effect, the nature of adsorption of N-acetylalanine on a silver surface was deduced. It can be concluded that the fully protonated N-acetylalanine is adsorbed on the silver surface via the imine group together with the carboxylate group, while it anchored onto the surface not only through both the imine and the carboxylate groups but also through the amide group after being completely deprotonated in the basic solution. Copyright (C) 2007 John Wiley & Sons, Ltd.