A Study On PVP And PVK By Surface Enhanced Raman Spectra And The Preparation Of Metal Colloids By Laser Ablation

PVP is a kind of macromolecule compound which is water soluble under thecertain conditions. It can dissolve or reunite with various macromolecule materialswhich reveals that PVP has good combination. As an electric charge transfers, PVK hasattracted much attentions in foundation and photoelectric technique field. SurfaceEnhanced Raman Scattering (SERS) is a useful tool for the research of moleculestructure and the interaction between the molecule and the substrate. The Raman modeof PVP/PVK is very sensitive to the charge of the electronic structure for the molecule.The absorption state on the surface of the substrate can be obtained through the Ramanspectrum.The reason why the electronic charge transfers between the molecule and themetal is that a strong interaction exists. In the experiment of SERS, the prepration of the substrates is very important. Themechanism of research and the applications can not get away from an active substrate.Since the SERS effect was discovered, people has been proceeding the quest to anactive base in SERS. In this thesis, some active substrates, which are chemical pure, areprepared by laser ablation, and the characteristics of them are discussed. There are four chapters in this paper, which can be divided into three sections: The first part, namely the first chapter: the basic concept of Raman spectra andSurface Enhanced Raman Spectra, the discovery, characteristics,mechanism,applications and the basic knowledge of SERS are mainly introduced. The second part, namely the second and third chapter:firstly, under the excitationwavelength of 632.8nm, SERS of PVP adsorbed on the surface of Ag mirror is investi-gated. Through compariment of the SERS and the Raman spectrum of PVP, theadsorption state of PVP on the surface of Ag was inferred. Secondly, SERS of PVKmolecules adsorbed on copper substrate, which was prepared by electrochemicalmethod, was studied in the same way. The adsorption state of the PVK molecules on thesurface of copp copper is obtained. The third part, namely the fourth chapter: chemical pure Ag, Au, Cu colloids wereprepared by laser ablation, and the characteristics of them were primarily analyzed. Theexcitation light used in our study was Nd:YAG pulse laser. Compared with the colloidprepared by chemical method, this method has advantages, such as, any ion is notcontained besides the solvent and the metal nanoparticls in the solutions. In the colloidsmade by chmical method, SERS research is easily affected by impurity ions, and thelaser ablation colloids can overcome this shortcoming. The images of SEM and AFMreveal that colloid particls are uniform, and most of them are dispersivly spherical.