Ab initio, DFT vibrational calculations and SERRS study of Rhodamine 123 adsorbed on colloidal silver particles

The adsorption of biologically important Rhodamine 123 molecule on silver colloids has been investigated by Surface enhanced resonance Raman scattering (SERRS) spectroscopy. The SERRS spectra are compared with its FTIR spectrum and normal Raman spectrum (NRS) in solution. The optimized structural parameters and computed vibrational wavenumbers have been estimated from ab initio (Hatree–Fock) and density functional theory (DFT) calculations. Some vibrational modes have been reassigned. From frontier orbital theory, the direction of charge transfer (CT) mechanism is concluded.