The Synthesis Of Mesoporous Zeolite And Assembly Of Nanosized Semiconductors

The aim of this dissertation is to synthesize mesoporous zeolites with high purity and assemble semiconductor nanoparticles into the channel of the zeolites. First, the layered sodium silicate, Kanemite, was prepared by utilizing solid-state synthesis method. Results indicate that the reaction mechanism was remarkably determined by the state of silicon in the raw material, and the presence of sodium was critical for the cleavage of Si-O-Si bond; water molecules played an important role in stablizing the layered structure. With hexadecanyltrimethylammonium (CTMA) as a template, zeolite FSM-16 was synthesized by reconstruction of the layered structure of Kanemite. XRD, IR and FT-Raman spectroscopic characterizations demonstrate that the formation of three-dimensional structure of zeolite FSM-16 is associated with puckering of layered silicate framework around the micell of CTMA. The frequency shifts and changes in intensity of the characteristic Raman and IR bands strongly suggest that The 5104 tetrahedron was distorted, and the terminal Si-On was altered from Q2 form to Q3 form during the formation process of FSM-16 framework. With the treatment of Ti2(S04)3, the organic surfactant molecules in FSM- I 6/CTMA were partially replaced by Ti3~ ions, which were further converted to nanosized Ti02 particles during the calcination process. The formation of nano-sized Ti02 particles had no influence on the formation of zeolite framework. However, the nanosized Ti02 particles formed inside the channel of the zeolite resulted in a strong interaction with the framework and consequently less extraction of the zeolite framework after removing the template CTMA molecules. Moreover, the quantum effect of nanosized Ti02 was observed as indicated by the fact that the Raman characteristic bands of Ti02 shifted to low wavenumber relative to those in the spectrum of the bulk material. The nanosized Ti02 in zeolite FSM-16 showed high photocatalytic activity for the oxidation of phenol, which were directly degraded to CO2 under the illumination of UV lights. Microwave technique was further employed in the preparation of a complex material of zeolite Y and CdCI2. It was found that under the treatment of microwave, Na~ ions 2+ were replaced by Cd ions via a solid-state ion exchange mechanism. As the loading extent of CdCI2 increased, an additional diffusion process of CdCl2 into channel of the zeolite simultaneously occurred. Thus, except for the Cd2~ ions at cation sites, electroneutral CdCI2 molecules also exist in the channel of zeolite, most probably existing as a submonolayer on the internal surface of the zeolite. In 1125 atmosphere, the Cd2~ ions were spontaneously converted to nanosized CdS particles in the channel of zeolite. The blue-shift in the band positions observed in absorption and fluorescence spectra demonstrates the size-effect of CdS confined by the channel of the zeolite.