چكيده به لاتين
Highly ordered mesoporous titania thin films having many kinds of applications such as chemical sensors, photocatalysts, self-cleaning coatings, antibacterial coatings, lithium batteries and solar cells due to the unique structure and electronic and magnetic properties of these materials. The application of these materials is affected by the microstructure parameters such as pores structure, specific surface area, and framework crystallization. In this project, the mechanism of mesostructure formation, effective parameters, and step by step controlling from precursor sol to final film was studied. Optimizing the material properties by adding dopant and finally the application of these materials as antibacterial materials were studied. At first, the possibility of thin film formation by using the sol-gel process and spin coating method was studied. The effect of many types of effective factors such as synthesis process, sol conditions, sol and film aging and suitable calcinations process was investigated. Then aluminum and cerium were selected and the optimum amount of these materials was determined. In order to investigate the microstructures, phases and morphologies of the samples the XRD, FESEM, HRTEM, GISAXS, UV-Visible, and Raman was utilized. The low temperature and humidity aging condition for the film as well as the low acidic sol pH (-0.5 to 0.3) was the optimum condition for highly ordered mesostructure formation. Increasing the solvent amount in precursor sol solution increased the film flexibility and mobility and changed the structure from disorder to order mesostructure. By using the F127 and P123 surfactants, two types of mesoporous symmetry Im3 ̅m and P63/mmc were achieved, respectively. The crystallization temperature and the first formed phase were 350oC and anatase phase, respectively. The ordered mesoporous Im3 ̅m structure was stable up to 350oC and the anisotropic shrinkage was observed in all films. By increasing the calcinations temperature up to 400oC, the ordered mesostructure was collapsed due to the crystalline grain growth in the framework. The nitrogen adsorption-desorption isotherms of samples calcined up to 500oC, was shown the IV isotherm, broad H1 hysteresis, and capillary condensation step. The narrow pore size distribution of the 350oC calcined sample was about 10nm.The pore diameter and the crystallite sizes of the materials were increased from 10.02 to 31.08 nm and 12nm to 20nm, respectively by increasing the calcination temperature.
The band gap energy was decreased from 3.97ev to 3.93ev due to increasing the calcination temperature from 300oC to 500oC. The highly ordered mesostructure was retained and the thermal stability was increased by adding 5% molar aluminum tetraisopropoxide. The thermal stability of the titania-alumina films compare to pure ones was increased, and the thermal shrinkage also was decreased due to dopant existence. By adding 1mol% cerium nitrate to the sol solution, the stability of the films was increased up to 450oC and the anatase peak was observed at 146cm-1 in Raman pattern. Finally, the mesoporous titania thin films prepared with the optimum synthesis conditions and calcined at 450oC was showed the highest antibacterial properties in comparison to other samples and commercial available antibacterial products.
