Templated Synthesis Of Surface Enhanced Raman Scattering Substrate And Its Application

In recent years, mesoporous SBA-15 has attracted considerable interest in the field of catalysis due to their high surface areas, uniform mesostructures, tunable pore sizes and high hydrothermal stability. Metals can be assembled inside the channels of mesoporous silica through attaching the hydroxyl groups on the channel walls of the mesoporous material, which can greatly improve the catalytic performance. The surface-enhanced Raman spectroscopy (SERS) integrated high sensitivity and can detect the structure of monolayer, sub-monolayer and even single molecule. The SERS by assistant with the Ag/SBA-15 compositions was employed to probe the catalytic mechanism at molecular level. In this thesis, Ag nanostructures attached onto the inner wall of SBA-15 have been fabricated with high SERS activity and reasonable catalytic performance. The catalytic mechanism was proposed. The main achievements of this thesis are listed as follows:(1) Mesoporous molecular sieves SBA-15 with tunable pore sizes were synthesized by conventional hydrothermal method. The hydroxyl groups on the channel of the inner and outer wall of SBA-15 were modified with functional molecules .Tunable monodisperse Ag nanoparticles and nanorods inside mesoporous SBA-15 materials were successfully synthesized.(2) The catalytic activities for the reduction of 4-nitrophenol in the presence of Ag nanostructures inside mesoporous SBA-15 were characterized by UV-vis absorption spectroscopy. The pure Ag nanoparticles were served as a comparison. The results showed that the as-obtained Ag materials /SBA-15 exhibited much better activity compared with the Ag nanorods/SBA-15. Furthermore, the SBA-15-confined silver materials have a better activity than the pure Ag nanoparticles. (3) SERS activities of Ag nanoparticles and nanorods inside mesoporous SBA-15 materials were characterized by using thiophenol (TP) as the probe molecule. The results revealed both Ag nanoparticles and nanorods in the inner of SBA-15 exhibited high SERS activities, and it indicated that the Ag/SBA-15 composition could be used as a SERS substrate.(4) To investigate the process of the catalytic reduction of 4-nitrophenol, the in situ SERS was employed to monitor the time depended reaction process. The result involves the initial formation of nitrosophenol in the reduction reaction of 4-nitrophenol to 4-aminophenol. Preliminary results makes it attractive which can provide a new way to in situ probe the catalytic mechanism of noble metal catalysts at molecular level.