Of Ag Sol And The Zno Substrate Surface-enhanced Raman Spectroscopy Study

Surface-enhanced Raman Scattering (SERS) is a unique surface optical phenomenon. It shows high sensitivity for detecting the molecules absorbed on the surface of the metal substrates and presents plentiful Raman information of the molecule structures. Therefore, SERS has been widely used in surface scientific, electrochemistry, mesoporphyrin protection, semiconductor optoelectronic devices, nano-materials, biological medicine, archaeology, and et al. We can observe SERS phenomenon on the surface of the substrates, such as noble metals, alkali metals, transition metals, semiconductors. The main results and conclusions are summarized as follows:1. Colloidal silver nanoparticles were prepared through liquid reduction with sodium citrate as reducing agent. According to a modified Lee and Meisel method, the influence of dosage of reducing agents on the size and distribution of colloidal silver were investigated. Zeta potential and transmission electron microscopy (TEM) are used to check the stability, size and shape of the colloidal silver. And UV/visible absorption spectrophotometry is used to study the optical absorption of colloidal silver. The absorption properties of crystal violet absorbed on silver-sol are studied by using traditional research methods. By using crystal violet as the probe molecule, SERS signals of silver-sols were performed. It shows that the amount of sodium citrate is the main influencing factor to the size, shape and SERS activity of the colloidal silver.2. The change current of the ultraviolet spectra and SERS signals of crystal violet at the addition of HCl, HNO3, H2SO4, NaCl, KCl, NaNO3, KNO3, Na2SO4, K2SO4 are also investigated.3. We choose another four compounds (benzoic acid, methylene blue, 4-mercaptopyridine, pyridine) as the probe molecules. SERS activities of these compounds adsorbed on the surface of silver colloids were studied. Through the Gaussian calculation and the experimental results, the molecular vibration information of the Raman band were presented. And we also calculate the SERS enhancement factor of the probe molecules on the Ag sol.4. We report surface-enhanced Raman scattering (SERS) spectra from crystal voilet (CV) adsorbed on rodlike and dumb-bell ZnO substrates. The maximum enhancement factor has been estimated to be about 102 compared to that of pure CV solution. The charge transfer between the ZnO nanocrystals and the CV molecules is most likely responsible for the observed enhancement of Raman intensity of adsorbed CV molecules as the semiconductor surface plasmon resnonance is away from the excitation light band.