Raman and Surface Enhanced Raman Scattering of 3-Hydroxyflavone

Normal Raman (NR) and surface enhanced Raman scattering (SERS) spectra of 3-hydroxyflavone (3-HF) have been measured. The SERS spectra are obtained both on an electrode surface and on Ag colloid. Spectral bands are assigned using DFT calculations for the NR, SERS, and FTIR spectra. The IR, normal Raman, and SERS results are compared and in conjunction with a DFT calculation are used to interpret the low-frequency carbonyl stretching vibration in 3-HF. The experimental results support the DFT geometry calculations, which show that an adatom site at the vertex of Ag20 cluster binding with the 3-HF molecular plane tilted at an angle of about 53° to the surface is a low-energy structure. This is consistent with the enhancement of in-plane vibrational modes.