Preparation And Performance Of N And Al Co-doped Titania Thin Films

TiO₂ is regarded as the most promising green photocatalyst due to its wide bandgap semiconductor, nature stability, avirulent and high active photocatalyst. However, there still exist two major defects for TiO₂ as follows:â‘ low photo quantum efficiency due to the higher recombination rate in photogenerated electron-hole pairs;â‘¡only small UV fraction of solar light, about 2-4%, can be utilized by TiO₂ because of its large band gap of 3.0-3.2eV. How to further improve photo-catalytic activity of TiO₂ and increase the utilization ratio to visible light are the key to technology application of TiO₂ photocatalyst. Therefore, developing high active TiO₂ photocatalyst is of great importance.The pure TiO₂ thin films, nitrogen-doped TiO₂ thin films and nitrogen and aluminum co-doped TiO₂ thin films were prepared on glass substrates and silicon substrates by vacuum arc deposition in this paper. Electronic structure of nitrogen-doped TiO₂ thin films and nitrogen and aluminum co-doped TiO₂ thin films were calculated by quantitative software based on First Principle. It was carried to investigate the influence of N-doped and N-Al co-doped on structure, composition, surface morphology, optics, photocatalyst and fantimicrobial performances of films. Compared pure TiO₂ films with doped TiO₂ thin films, the mechanisms of co-doping effect were discussedResults of this paper appear as followed: The results of calculation by quantification software. based on the first principle showed a small amount of N-doped could result in narrowing down band gaps of TiO₂. N and Al co-doped displacement could cause band gaps widely. N and Al co-doped gap digit could cause band gaps narrowly.The structure of as-deposited pure TiO₂ thin films, nitrogen-doped TiO₂ thin films and nitrogen and aluminum co-doped TiO₂ thin films were amorphous. After annealed at 400℃, structures of films were anatase phrase and with (101) appeared preferred orientation. The rounded or ellipse grains and micropores formed on the surface of thin films. The absorption of light wavelength was red-shifted as the deposited time extended.N-doped could lead to red shift of the absorption limit of N-doped TiO₂ thin films, and expansion of absorbed wavelengths scope. Visible light catalytic activity of N-doped TiO₂ thin films deposited for 15 min and annealed at 500℃was the best. Visible light catalytic activity of the N-doped TiO₂ thin films deposited with ion beam assisted was better than that without ion beam assisted.The N and Al elements hindered phase transfer of TiO₂, restrained growth of nano-TiO₂ particles and improved the crystallization temperature. Degradation ability of N and Al co-doped TiO₂ thin films annealed at 500℃to acid fuchsin whether under UV light or under artificial simulated sun light was the best.N and Al interstitial co-doped resulted that carrier mobility of TiO₂ thin films was improved and carriers recombination was restrained. The synergy between N and Al led to improvement in photocatalytic activity of visible light. The photocatalytic activity under visible light decreased in order of N and Al co-doped TiO₂ thin films, N doped TiO₂ thin films and pure TiO₂ thin films.Degradation process of N and Al co-doped TiO₂ thin films to acid fuchsin under visible light did not at all abide by first order reaction kinetics equation and included different reactive course. During the reactive course, there existed different apparent rate constant at different reactive phases. The kinetics of reaction model of visible light photocatalytic degradation was put forward and verified by experiment.The experimental results have also shown that antibacterial activity of TiO₂ films without annealing was bad. The antibacterial rates of pure TiO₂ thin films, nitrogen-doped TiO₂ thin films and nitrogen and aluminum co-doped TiO₂ thin films annealed were all over 99.9% against the growth of Escherichia coil and Staphylococcus aureus after 2h exposure to light. The effect of thickness of films against the growth of Escherichia coil was often larger than that of Staphylococcus aureus. Antibacterial activity of TiO₂ thin films deposited with ion beam assisted was higher than that without ion beam assisted.