A Study Of Molecular Vibration Spectrum And Surface-enhanced Raman Scattering On Thymine

Thymine, cytosine, adenine and guanine, the four nucleic acid bases are the basic materials composing DNA, and take great part in the genic expression and genic replication. In last years, thymine, thymidine and their derivatives have been investigated abroad,including the spectra of SERS absorbated on different metal surfaces.With the development of computer technology, it becomes true for people to resolve the matrix equation accurately. We could calculate the molecular vibrational spectrum in the level of theory . DFT have considered the electron exchange and electron correlation energy in the process of calculation, so that the calculated results are more precise than other theories.Raman spectroscopy and Infare spectroscopy are two important tools for us to investigate the molecular structure and molecular vibrational spectroscopy. Due to it's strongpoint, such as high sensitivity and low injure, Raman spectroscopy is accepted universally by scientific researcher. SERS (Surface Enhanced Raman Spectroscopy) has very high sensitivity as it's be use to the microanalysis, so it is applied to study the deformation of molecules structure and the interplay between molecules and surface of metals when the molecules were adsorbed on the surface of metals.This study is composed of four parts:1, Introduce the rudimental concept, character and some involved parameters of Raman scattering. Illuminate the importance of Raman scattering technology in the application of material structure token. In addition, depict the developmental history, enhanced mechanism and application of SERS. 2, Introduce the meaning of studying thymine molecular, the theory principle of GAUSSAN 98 soft and the calculated method. Use different theory model to calculate the molecular vibration spectrum of thymine in the gas phase, crystal state and the aqueous solution, and every vibration modes have been assigned.3, The experimental Raman and Infrared spectra of thymine in solid state, and the Raman spectrum of thymine in neutral aqueous solution were recorded. In the same time, the experimental spectra have been compared to the theory calculated results.4, Investigate the SERS of thymine in silver colloids and find out that molecules of thymine were adsorbed on silver nanoparticles in a perpendicular orientation to the silver surface by O7, through the analysis and compare of the experimental and calculated results. Meanwhile research the SERS of thymine adsorbed on copper electrode in different voltages and find out that the way of thymine adsorbed on copper surface was changed when the voltage of copper electrode changed.