Spectral investigations on 1,4-dimethylamino anthraquinone under laser excitation.

Surface enhanced Raman spectrum of 1,4-dimethylamino anthraquinone (1,4-DMAAQ) adsorbed on silver particles has been analyzed to understand the interaction between the molecule and silver surface. By studying the band intensities, the orientation of the molecule is determined. The high intensity and frequency downshifted peak due to carbonyl stretching vibration plays a major role, which shows that the molecules are chemisorbed through coordinating sites. The new peaks observed due to C-N and N-H stretching vibrations also provide the evidence for adsorption through co-ordinating sites. Optical absorption and laser induced fluorescence spectra of this molecule have also been studied in different solvents to understand the effect of environment. Polarization and anisotropy measurements provide the change in orientation induced by solvent molecules between absorption and emission transition dipoles.