Influence of organic solvents on the intensity of surface-enhanced Raman scattering of water molecules

The influence of methanol, ethanol, 1-propanol, and acetone on the intensity of surface enhanced Raman scattering (SERS) of water molecules on Ag electrodes in 0.1 M KBr electrolyte was studied. Immediate increasing of SERS intensity of water was observed upon addition of all the solvents studied during the potential hold after the reduction was completed. It indicates that they are efficient in disrupting the hydrogen bonding between the adsorbed water and the bulk water network. After a subsequent oxidation-reduction cycle (ORC), the SERS intensity was not as strong as those obtained during addition of the organic solvent except ethanol. We believe that it is due to the competition for SERS-active sites among the organic solvent molecules and the interfacial water molecules, and the dilution of water and halide ions. The effect of laser illumination on SERS intensity in 0.1 M KBr electrolyte was also studied. Blocking the laser off during the ORC could lead to large SERS enhancement factor, whether or not the organic solvent was added.