Synthesis Of Ordered Mesoporous Silica Films Using Molecular Templating Method

The ordered mesoporous thin films may be found great potential applications in catalysis, sensing, medicine, purifying environment, photonics and microelectronics, as they have uniform pores arraying orderly and the size of the pores can be tuned in the range of 2³0 nm.The ordered mesoporous thin films were synthesized by the evaporation-induced self-assembly using cetyltrimethylammonium bromide (CTAB) as template and tetraethyl--orthosilicate (TEOS) as silica source. During the synthesis, these processes were utilized including sol-gel, spin-coating, calcining, solvent-extraction and dehydroxylating of the films. The microstructure and properties of the thin films were characterized using XRD, TEM, FT-IR, TG-DTA and Ellisometry. The results were as follows:(1) The influence on the mesostructure and properties of the thin films were studied by varying the ratio of EtOH/TEOS, HCl/TEOS and CTAB/TEOS. And a rational proportion(mol ratio ) of the raw materials is:1TEOS : 10H₂O : 10EtOH : 1.8×10^-3HCl : 0.2CTAB(2) By comparing the influence on the thin films executed by the calcinations and solvent-extraction of the surfactant, a reasonable method for removal of the surfactant was that dipping the thin film in the mixture of the isopropyl alcohol and hydrochloric acid followed by drying the film using super-critical fluid drying. This method had not been reported in other articles befor.(3) After dehydroxylating the thin film using trimethlchlorosilane(TMCS), the order and stability of the film remained very good.(4) The analysis of the microstructure of the thin film showed that the XRD spectrum of the thin film had unique diffraction peak around 3° related with the ordered mesoporous structures and well orderly arranged pores could be seen in the TEM pictures of the film. The properties of the thin films prepared using solvent-extraction and SCFD were as follows: pore diameter: 2.5nm, thickness: 400nm, porosity: 38.34%.(5) The process of the assembly of template and silica oligomers was testified by changing the reaction condition. The results revealed that with the aid of stiring, the procusor of silica entered into the interspace between the ordered micells and grew into organic-inorganic composite.