The Surface-Enhanced Raman Scattering Study Of Liquid Crystal 5CB

The Surface-Enhanced Raman Scattering Study ofLiquid Crystal 5CBBy Fulin WangSupervisor: Prof. Haiguang ZhouABSTRACTin this dissertation, the orientation of Liquid Crystal 5CB absorbed on nano-roughened Ag and Au electrodes under different potentials and excitation laser wavelengths are studied with Surface-Enhanced Raman Scattering (SERS) which is now considered as the major technique in the area of surface characterization. The potential varied from O.OOV to-1 .60V. Two pieces of excitation laser wavelengths were used, 632.8nm and 5 l4.Snm respectively. All the experiments were done under room temperature.Our experiments results firstly suggest that the orientation of LC 5CB absorbed on Ag electrode is different from that of Au electrode. This implies that the interaction between LC 5CB and Ag electrode is different from the interaction between LC 5CB and Au electrode. Moreover, the potential-dependent SERS of LC 5CB absorbed on nano-roughened Au electrode is more complicated than that of Ag electrode. After analyzing and discussing, we draw the conclusion that the orientation of LC 5CB absorbed on nano-roughened Ag electrode is perpendicular orientation, and the orientation of LC 5CB absorbed on nano-roughened Au electrode is more complicated, including parallel and perpendicular orientation.The electromagnetic enhancement mechanism for SERS on nano-roughened metal electrode is discussed. Besides, we also give some discussion over the metal dielectric constant, which plays important role for the electromagnetic enhancement mechanism for SERS.