The Preparation Of Noble Metal Nanoparticles By Pulsed Laser And The Application In Raman Spectroscopy

With the development of science and technology, there are many different preparation methods of nanoparticlas. As we know, vapor phase synthetic method, sputtering method, chemical reduction method, laser compositing method and so on are all usual methods to prepare metal nanoparticles. However, because the laser compositing method can well control nanoparticles' uniformity and the scale in the preparing process, it be well used widespread in many fields.In this paper, we use the laser ablation method to prepared noble metal (Ag/Au) nanoparticles in redistilled deionized water. The preparing proceses of Ag/Au nanoparticals with different pulse laser wavelength and laser energy density were studied. With the measuring tools of transmission electron microscope (TEM), scan eletron microscope (SEM) and atom force microscoper (AFM), we analyzed the influences of the pulse laser energy density, laser frequency and ablation time to the netal nanoparticles' scaled-size, dispersibility and uniformity. Meanwhile, the ablated Ag/Au plate suface and Ag/Au nanoparticles in laser ablation process were studied at infrared laser wavelength and ultraviolet laser wavelength.Surface-enhanced Raman scattering (SERS) is a highly sensitive technique for probing the interfacial phenomena and the behavior of molecules adsorbed on metal nanoparticles surface. In SERS optical spectroscopy, the noble metal Ag/Au nanoparticles can serve as a highly efficient substrate for SERS investigation, but in prevenient reports, the SERS substrates, such as Ag and Au nanoparticles, were prepared by chemical reduction methods, these methods are simple and rapid, and the enhanced effects of SERS are are very obvious. However, during the process of producing the metal colloids, the presence of residual oxidation products and extraneous ions in the colloids can cause uncontrolled aggregation and diffusive double layer on the metal nanopartices surface, which will disturb the adsorption behavior between the molecules and the metal surface. All of these will bring out many comples factors for analyzing the physical and chemical mechanism of SERS.