Fabrication And Characterization Of Several Nanocomposite Materials And Their Application In SERS

Along with the renovation and advancement of modern nanotechnology, nanocomposite materials have been widely used in the field of information, communication, automobile, medicine, biotechnology, analysis, diagnosis, chemistry, manufacture and environment protection. Interest in nanocomposite materials mainly results from their size-dependent physicochemical properties, making them potential candidates for a wide variety of applications in nonlinear optic, mechanics, magnetics, electrics, catalyzer and sensor. The development of surface-enhanced Raman scattering(SERS) are closely related to nanocomposite materials, so the research of SERS on nanocomposite materials will have attracted more and more attention in the future. In this thesis, several nanocomposite materials have been fabricated and characterized, and their SERS activities are studied. The main conclusions are summaried as below:(1) Spherical and rodlike silver nanoparticles have been fabricated using a new technique"homogeneous shaking", then these silver nanoparticles are successfully self-assembled on APTMS modified glass slides by an electrostatic interaction to obtain SERS substrates. Atomic force microscope (AFM) is employed to investigate the morphologies of the substrates. The optical properties of the silver nanoparticles were examined by the UV-vis spectra.(2) Silica spheres are used as a template to prepare Ag-coated silica nanospheres (SiO2@Ag) through an electrostatic interaction. Subsequently, these monodispersed SiO2@Ag nanospheres are assembled onto the glass substrates, which have been functionalized by APTMS, to form close-packed three-dimensional SiO2@Ag nanosphere arrays by electrostatic interaction. The SiO2@Ag nanospheres are investigated as substrates for surface-enhanced Raman scattering (SERS) using Rhodamine 6G (R6G) as probe molecules, and the enhancement factor of the Raman signal obtained on the SiO2@Ag nanospheres is about 2×109 for Rhodamine 6G. Comparing with pure silver hydrosols, the SERS-active SiO2@Ag substrates possess better Raman enhancement efficiency.(3) Core-shell structure of Au@SiO2 nanoparticles and silver coated Au@SiO2 nanoparticles (Au@SiO2@Ag NPs) have been fabricated by a seed-mediated growth technique under shaking. Then hollow Ag nanoparticles with a shell thickness of 30 nm and with movable Au cores of 30 nm diameter inside (Au@air@Ag NPs) are further prepared by dissolving silica shell within Au@SiO2@Ag NPs by HF. The morphologies of those obtained nanoparticles are characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The application of the as-prepared Au@air@Ag substrates in SERS is investigated by using Rhodamine B as a probe molecule. The results indicate that the Au@air@Ag NPs are ideal SERS-active materials.