The Preparation And Properties Of Functional Composite Mesoporous Materials Research

Hollow spheres with mesoporous wall consist of silica or nitrogen doped Titania were prepared via a surfactant-assisted sol-gel process. The silica hollow spheres showed excellent adsorption performance to organic molecules such as methylene blue, while the nitrogen doped Titania hollow can degregate methylene blue efficiently under the irradiation of visible light. In addition, the influence of different pH values on the adsorption of methylene blue from it aqueous solution to mesoporous silica were studied in details. The multifunctional system of Ag@Fe3O4@C (particles@nuclear@shell), which integrated mesopores, magnetic function and antibacterial nanoparticles were fabricated using the spray drying and the ultrasonic technology. The main points of this dissertation go as follows.(1) Using the surface charged and acid dissolvable melamine formaldehyde (MF) microspheres as sacrificial hard templates, CTAB as a mesoporous directing agent, and TEOS as silica source, silica coated MF core-shell composite microspheres, denoted as MF@SiO2, were synthesized via the surfactant-assisted sol-gel process. Hollow SiO2spheres with mesoporous shells were then obtained after selective removal of the MF cores and the pore directing surfactant by hydrochloric acid etching or calcinations in air. The influence of the ratio of MF sphere to TEOS and the removal method of the MF core on the size of the hollow spheres, the shell thickness and the shell surface roughness have been studied. The composition, the thermal stability, the morphology, the surface area and pore size distribution, the wall thickness and adsorption properties of the hollow spheres derived from hydrochloric acid etching and calcinations were also investigated and compared based on the FTIR, SEM, TEM, TGA, Nitrogen adsorption-desorption and spectrophotometer techniques or measurements.(2) N-doped TiO2hollow spheres with mesoporous wall were prepared based on a sol-gel synthesis and calcination process using the surface charged melamine formaldehyde (MF) microspheres as hard templates. Cetyltrimethyl ammonium bromide (CTAB) was used as both pore directing agents and N-doping precursor, and hollow TiO2spheres with size in range of0.4-1.2μm could be obtained. Characterization of the monodisperse hollow titania spheres by X-ray diffraction (XRD) revealed that the obtained hollow spheres nanocrystals had fine anatase crystalline structure. Furthermore, N-doped TiO2hollow spheres showed an obvious absorption in the visible region and possesses superior photocatalytic activity on the degradation of MB under visible light irradiation (wavelength>420nm) irradiation. These phenomena have been attributed to the influence of nitrogen ions doping to the TiO2lattice that could extend its optical response to the visible-light region. (3) Methylene blue (MB) was used as model molecule to investigate the effects of surface properties and solvent pH values on the adsorption and desorption (or release) behaviors of mesoporous SBA-15materials (t-SBA-15) by weak alkali treatment and untreated SBA-15materials (p-SBA-15). It has been demonstrated that both the adsorption rate and adsorption capacity of t-SBA-15was higher than that of p-SBA-15. In addition, It is very interesting to note that both the t-SBA-15and the p-SBA-15samples showed the releasing maximum at a pH value around2, however, the releasing amount is quite low at a pH value of7. But the treated SBA-15samples showed a higher releasing quantity than the p-SBA-15samples. The influence mechanisms of base treatment on the adsorption ability and that of pH values on the releasing properties of SBA-15samples have been analyzed and been discussed based on the composition, the morphology, the surface area and pore size distribution and guest molecule adsorption/desorption measurements.(4) A composite of Ag@Fe3O4@C with particles@core@shell structure were prepared via a spray drying assisted template method and an ultrasonic route. In the process of spray drying, chitosan as the carbon precursor and commercial colloidal silica as a pore-forming agent. After the carbonization of the as-formed silica@Fe3O4@chitosan composites at550℃under a nitrogen atmosphere, and the removal of silica template by NaOH treatment, Fe3O4@C mesoporous nanocomposites Fe3O4@C materials can then be loaded with Ag nanoparticles by an ultrasonic route without adding any chemical redox reagent. The resulting samples were investigated and compared based on the SEM, TEM, Nitrogen adsorption-desorption, X-ray diffraction etc.