Studies On The Preparation, Characterization And Optical Properties Of(MCM-41)-La₂O₃ Nanocomposite Material

In this thesis, nanometer MCM-41 molecular sieve was synthesized in alkaline medium by hydrothermal method using cetyltrimethylammonium bromide as template, tetraethoxysilane as silicon resource. La2O3 was incorporated into the mesoporous channels of the MCM-41 molecular sieve by solid phase thermal diffusion method. The (MCM-41)-La2O3 nanocomposite materials with different concentrations were prepared. By means of chemical analysis, powder X-ray diffraction, Fourier transform infrared spectroscopy, low temperature at nitrogen adsorption-desorption technique 77 K, solid state diffuse reflection asorption spectroscopy, Ramam spectroscopy, scanning electronic microscopy (SEM) characterize analysis and luminescence spectra, the host-guest nanocomposites materials were characterized. Powder XRD results showed that La2O3 has been successfully assembled into the pores of molecular sieve and the frameworks of the prepared materials were not destroyed. The prepared (MCM-41)-La2O3 host-guest nanocomposite materials still had high ordered property. As the increase in the concentration of the embedded guest material, the degree of order of the composite materials decreased. Infrared spectra showed that the host molecular sieve frameworks of the prepared nanocomposite material intact. The low-temperature nitrogen adsorption-desorption technology indicated that the La2O3 has been partially occupied the pores of the MCM-41 molecular sieve, which resulted in the decrese in the surface area and the pore volume of the molecular sieve. The solid state diffuse reflection absorption spectra showed that for the absorption peaks of absorption spectra blue shift phenomena took place and the quantum confinement effect exhibited. It indicated that La2O3 has been encapsulated in the pores of the MCM-41 molecular sieve. Raman spectra showed that for the prepared composite materials no new peak appeared, showing La2O3 has been incorporated into the channels of the MCM-41 molecular sieve. SEM showed that the appearance of the (MCM-41)-La2O3 was very orderly and the mainly presented form was globular structure. When the content of La2O3 was 10%, the mean particle diameter of the (MCM-41)-La2O3 was 114±10 nm. The results on the studies of luminous spectra showed that the host MCM-41 molecular sieve itself had no luminous phenomenon, the (MCM-41)-La2O3 samples prepared have good luminous properties. Thus, the (MCM-41)-La2O3 have the potential foreground as luminous material.