Preparation Of Ordered Silver Nanowire Arrays And 'Chemically Pure' Silver Colloids And Their Application In SERS

As a kind of the interaction between light and material, Raman scattering is the inelastic collision of photons and molecules of scattering material, which results in the change of energy and momentum of incident photons. The difference of scattering photons and incident photons provides us the information of vibrational and rotational states of the molecules of scattering material. So Raman spectroscopy has been playing an important role in the study of molecular structure. However the intensity of normal Raman spectroscopy is so weak that its application has been hindered to some extent. The surface-enhanced Raman scattering(SERS) has the advantages of higher intensity and higher sensitivity, and thus widely extends the application fields.In the research of SERS, the enhancement factor, application and the enhancement mechanisms all depend on the active substrates. So, the preparation methods of active SERS substrates have long been investigated since the discovery of SERS.This thesis consists of three sections as follows:First, the preparation and characterization of porous aluminaPorous alumina was prepared by anodic oxidation. The experiment showed that the formation of porous alumina from electro-oxidation, in the aqueous solution of oxalic acid with appropriate concentration experienced three stages: (1) the formation of barrier layer; (2) the breakdown of alumina at some spots on the films; (3) the stable growth of a porous layer. The result indicated that separated nanopores, which were perpendicular to the film surface but parallel each other, with homogeneous diameter and distribution were dispersed in the template film. The pore diameter can be controled by immersion time in sulfuric acid. The above features of porous aluminashowed that it was a desirable template to fabricate ordered nanowire arrays.Second, the preparation of ordered silver nanowire arrays and its application as SERS substrate.Silver nanowire arrays were obtained by alternate current deposition in the template of porous alumina. The AFM image revealed that the silver nanowire arrays were ordered, perpendicular to the film surface but parallel each other, and its diameter was 60nm. Good-quality SERS spectra of Rh6G on this nanowire arrays were observed, which demonstrated the SERS intensity depending on the wires length emerged above the surface, however the Raman shift was not affected by the surface condtion.Third, the preparation of laser-ablated silver colloids and its application as SERS substrates.The 'chemically pure' silver colloids was prepared by laser ablation of silver with a Nd:YAG laser. This silver colloids only contained solvent and silver nanometer particles. The TEM image showed that the silver particles were uniform and spheric shape, and the average particle size was 20nm. Good-quality SERS spectraum of Py and Rh6G on this silver collids were also observed successfully.