Preparation And Characterization Of Titanium Dioxide Nanoparticles With Highly Photoactive & Study On Photocatalytic Degradation Of Biomolecules

Chapter 1:This chapter reviews the recent 30-year progress made on TiO₂ photocatalytic technique both at home and abroad is introduced, including the principle and mechanism of photocatalysis, preparation and modification of TiO₂ with high photocatalytic activity, the ways for enhancing photocatalytic efficiency, and its application for biomedical field. Chapter 2:The iron-doped nano-titania were prepared from titanium tetrachloride precursor by a two-step method, involving microwave and comventional heating treatments. The iron-doped nano-titania was characterized with XRD, TEM, SEM, UV-Vis, XPS and FT-IR techniques. The results indicated that the iron-doped nano-titania with an average diameter of 10 nm, contained anatase as the main phase, along with rutile. It was found that the dopant of ferric ions at proper concentration promoted the formed rutile phase, and reduced the crystallite size of anatase. The increase of 0.3 eV of binding energy of Ti2p was observed after the nano-titania doped with 0.5 % mole ratio ferric ions. Moreover, the photoresponse shifted to visible light was also detected with the iron-doped nano-titania. Photocatalytic activity was evaluated by measuring decomposition rates of vitamin B₁₂ exposed to UVA(320⁴00 nm) radiation. The results indicated that optimum ferric ions concentration was 0.5 % mole ratio for the iron-doped nano-titania, of which the reaction rate is high up to two fold of that of the undoped nano-titania. Chapter 3:Numerous preparation methods exist for the high photocatalytic activity TiO₂ particles. The majority of these processes require long reaction times, high pressures and temperatures. In this work, pure and silver doped TiO₂ powders were prepared by the microwave synthesis. The result highly crystalline TiO2 colloids were characterized using XRD, TEM, XPS, and UV-Vis. It is found that Ag doping promotes the phase transformation and has an effect on the anatase grain growth. With a suitable amount, the Ag dopant reduces anatasegrain size. The photocatalytic activity of the Ag doped TiO2 was investigated and studied in photocatalytic degradation of rhodamine B under UV irradiation in comparison with pure TiO2 powders. The result exhibits a considerable growth in improving the TiO2 photocatalytic activity. Chapter 4: The photooxidation (λ= 253.7 nm) of the compound vitamin B12, catalysed by the photocatalyst TiO2(Degussa P25) was investigated in an aqueous suspension. The photocatalytic process was found to conform to a Langmuir adsorption isotherm. The effect of the initial concentrations vitamin B12, the amount of TiO2 and the pH value on the photocatalytic rate was studied. A mechanism involving the oxidation of the axial ligands in vitamin B12 induced by free radical, firstly leading to the dissociation of the axial ligands in vitamin B12, is proposed there.