Air - Water Interface Protein And Sio <sub> 2 </ Sub> Film Role

Recently, the preparations of nano-thin films have increased widely interests. In the preparation system, the addition of biopolymers is very popular. In this paper, air-water interfacial SiO₂ films with regular nanostructures have been prepared by cationic surfactant cetyl trimethyl ammonium bromide (CTAB), casein and tetraethyl orthosilicate (TEOS). A series of analytical methods have been applied to characterize the self-assembled films and analyze the interaction of protein and cation surfactant, including X-ray diffraction (XRD), Ultraviolet visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FT-IR), Raman spectra, Fluorescence spectrography, Surface tension, Scanning electron microscope (SEM), Transmission electron microscope (TEM) and so on. The main work is summarized in the following:(1) Air-water interfacial SiO₂ films with nano-structure are prepared with cationic surfactant CTAB and casein under pH=12. Results show that the morphology of SiO₂ films transferred from the sphere particle into a ball-rod mixed aggregation in the presence of casein. Additionally, the diameters of ordered mesopores in the films have been little increased compared to the films without casein.(2) At pH=12, the interaction between casein and CTAB and the properties of casein solution have been investigated by UV-vis, Fluorescence spectrography. In the presence of alkaline solution, the secondary structure of casein was different from that in neutral solution. The complex of casein/CTAB was formed by electrostatic interaction and hydrophobic interaction. Accordingly, the formation mechanism of SiO₂ films was proposed. This kind of air-water interfacial SiO₂ films was formed by the interaction of Casein/CTAB and SiO₂OH^-. Furthermore, casein played the roles of dispersant and stabilizer in the self-assembled process.(3) Some other proteins (gelatin and bovine serum albumin) and anion surfactant (sodium dodecyl sulfonate) have also been employed to prepare air-water interfacial SiO₂ films. Both obtained films display different structures. TEM results of SiO₂ films assembled with gelatin showed ordered lamellar structures, which were more regular than the samples with bovine serum albumin. The morphologies and structures of SiO₂ films templated by CTAB seemed better than the products with SDS.(4) After calcination of SiO₂ films, the products with mesoporous structures showed nano ball-like morphologies. Finally, the kinds of SiO₂ film before and after calcination have been purposely applied as cocatalysts in the photocatalytic field.