Theoretical and experimental studies on the adsorption behavior of thiophenol on gold nanoparticles

FT-Raman spectra were obtained for thiophenol UP) and TP on gold nanoparticles. All vibrational fundamentals for the TP molecule are assigned on the basis of the scaled quantum force field procedure. Three model systems are studied and compared for the interactions of TP with the Au atom: (1) TP with a Au atom, C6H5SH-Au; (2) TP anion with a Au atom, C6H5S--Au; and (3) TP with a Au atom and subsequent formation of thiophenylate, C6H5SAu. The equilibrium structures and Raman spectra were calculated for the model systems using density functional theory (DFT) with the B3LYP functionals and the mixed basis set 6-311+G** (for C, S, H) and LANL2DZ (for Au), and theoretical Raman wavenumbers of C6H5SAu and C6H5S--Au were assigned according to potential energy distributions. The third model system is shown to be preferred over the other two. The calculated binding energies are also shown to support the third model system. It is suggested that a simple model, such as the one used in the present study, is reasonable to describe surface-enhanced Raman spectroscopy of thiophenol adsorbed on gold nanoparticles. Copyright (C) 2007 John Wiley & Sons, Ltd.