The adsorption behavior of two hydroxyl-terminated Schiff bases on the silver surface and the correlated study of SERS effect

Two hydroxyl-terminated Schiff base probe molecules have been prepared and their configurations have been assigned on the basis of 2D-NOESY experiments. Surface-enhanced Raman scattering (SERS) spectra of the probe molecules have been recorded on the silver surface. In addition, theoretical studies by density functional theory (DFT) method at B3PW91/Lanl2dz level have been applied to predict the vibrational modes and the probable adsorption behavior of Schiff bases on Ag surface. Interestingly, both the theoretical and experimental results suggest that these hydroxyl-terminated Schiff bases are anchored, in a tilted way (with a certain angle between the two non-coplanar benzene rings and the silver surface), on the silver surface via the oxygen atoms instead of the nitrogen ones. Furthermore, the SERS enhancement factor (EF) has been calculated, indicating that the selected probes can be applied in trace analysis.