Synthesis And Property On SiO₂/TiO₂-based Nanocomposite Materials

The research and application of self-assembly technique are of great scientific and technological importance, the preparation of inorganic material-based films using self-assembly technique has attracted intense research interest over recent years. This paper presents a novel method based on self-assembly for the fabrication of a series of air-water interfacial oxide nanofilms with ordered structure, using surfactants as template and gelatin as stabilizers with organic metallic alkoxide precursors. X-ray diffraction (XRD), fourier-transform infrared spectra (FT-IR), N2 adsorption-desorption isotherms, Raman spectra, thermal gravity and differential thermal analysis (TG-DTA), scaning electron microscope (SEM), transmission electron microscope (TEM) and energy dispersive spectra (EDS) are use to characterize the morphologies, structures, compositions and self-assembly mechanisms of the self-assembled nanofilms. The catalytic properties, surface-enhanced Raman spectroscopy and antibacterial properties have been carefully investigated and discussed after modification of the nanofilms.The main contents are summarized as following:Mesoporous-like amorphous silicon oxide nanofilms are self-assembled with gelatin as stabilizer by using cetyltrimethylammonium bromide (CTAB) as template and TEOS as precursor. The interaction between surfactant headgroups (dimeric molecular bar) and mesoporous-like silicon oxide is approved to be the formation mechanism to form the nanostructure by XRD, SEM, BET, TEM and Raman. The thermal property of the silicon oxide nanofilms is also investigated. TEM is successfully applied to observe the microstructural changes of air-water interfacial SiO2 secondary particles and the transformation mechanism is investigated, which analyze the morphology and structure of the SiO2 nanoparticles after calcination at different temperatures. The SiO2 nanoparticles as a microreactor are soaked into silver nitrate (AgNO3) aqueous solution. Then the dendritic Ag nanoparticles can be prepared by a reaction of silver nitrate with template agent (CTAB) and AgBr decompose into elemental Ag nanoparticles under visible light irradiation in the SiO2 microreactor. The morphology and structure of as-prepared Ag nanodendrites are characterized by XRD, SEM, TEM and UV-vis, the correlated surface-enhanced Raman scattering (SERS) effect have been investigated when 2-Mercaptobenzothiazole (2-MBT) is used as a Raman probe. The results clearly show that the dendritic nanostructures can be obtained through oriented attachment of nanoparticles along a crystallographically special direction and the morphology of the dendrites is dependent on the reaction duration in the reaction process. After soaked in silver nitrate (AgNO3) aqueous solution for 5min, the SiO2 nanoparticles are soaked into sodium thiosulfate (NaS2O3) solution so that the sphereical Ag-SiO2 composite nanoparticles can be obtained by the same method. The composite nanoparticles are used to the antimicrobial experiments, the experiments indicate that the Ag-SiO2 composite nanoparticles have good anti-bacterial properties. The action mechanism has also been discussed.By CTAB as template, gelatin as stabilizer and Ti(OC4H9)4 as precursor, Titanium oxide nanofilms composed of lamellar structure have been self-assembled. The TiO2 nanofilms are soaked into silver nitrate (AgNO3) aqueous solution. Then the Ag-TiO2 composite nanoparticles can be prepared by a reaction of silver nitrate and sodium thiosulfate with template agent (CTAB), the Ag-TiO2 particles are used to the antimicrobial tests and the experiments indicate that the Ag-TiO2 nanoparticles have good anti-bacterial properties. The structure of composite nanoparticles may be strengthened after heated treatment. We investigate the SERS effect on the surfaces of the composite nanoparticles. Methyl orange is used as the degradable agent in photocatalytic experiment by using the Ag-TiO2 particles as a photocalalyst. The Ag-TiO2 nanoparticles can be applied to improve catalytic activity of the epoxidation of styrene oxides. Styrene oxide is the main product of catalytic reaction with H2O2 as the oxidant by using Ag-TiO2 nanoparticles as catalysts. High catalytic activitity of styrene oxide can be obtainable. The reaction temperature, reaction time, the molar ratio of H2O2/styrene and solvent affect greatly the catalytic epoxidation of styrene and the stability of the catalyst has been analysed.By anionic surfactant sodium dodecyl sulfate (SDS) as template, the self-assembled TiO2 nanofilms are prepared under acidic conditions. The TiO2 nanofilms are soaked into barium chloride (BaCl2) aqueous solution. Then the BaSO4-TiO2 nanocomposite particles can be prepared by a reaction of BaCl2 with template agent (SDS). According to the heat treatment conditions, the amorphous TiCl2 nanofilms transform into anatase TiO2 after calcination at 400℃. The photocatalytic activities are described, and the catalyst has been proved to the instability in repeated using.TiO2-SiO2 binary nanofilms are self-assembled with cetyltrimethylammonium bromide as template. The nanofilms are composed of lamellar particles. Contrasted by Ag-TiO2 catalysts, TiO2-SiO2 has a little lower activity, but has characteristics of higher stability.