Adsorption study of 4-MBA on TiO2 nanoparticles by surface-enhanced Raman spectroscopy

In this paper, the adsorption of 4-mercaptobenzoic acid (4-MBA) on TiO2 nanoparticles was studied mostly by surface-enhanced Raman spectroscopy (SERS) and UV-vis spectroscopy, at different pH values as well as under different temperatures and concentrations. The results show that the 4-MBA molecules are bonded to the TiO2 surface both through the sulfur atoms and COO- groups at neutral or alkaline pH, but only through the sulfur atom at acidic pH. Furthermore, the 4-MBA molecules possess high adsorptive stability on TiO2 at a comparatively high temperature (150 degrees C). Concentration-dependent SERS experiments show that the saturation concentration for 4-MBA adsorbed on TiO2 is about 10(-3) M in natural case (pH = 6). Copyright (C) 2009 John Wiley & Sons, Ltd.