Preparation Of Titania Nanomaterials Using Proteins As Bio-templates And Exploration Of The Mechanism

In recent years, a variety of biological tissues for the template synthesis of materials have attracted extensive attention. Amongst, proteins are of particular interests due to their inherent advantages. Proteins can closely integrate with many inorganic materials in vivo to form the body such as bone, shell of arthropods and skeleton of diatoms. Moreover, proteins are cheap and accessible with a wide range of sources.Casein and egg albumin are employed as bio-templates to synthesize titania and zinc oxide with good photocatalytic activities.We employ casein as template with water as solvent and obtain titania nanosheets from static solution at room temperature after 10 days. The titania nanosheets are amorphous with smooth surface. Their length and width are in micron-level and their thickness is about 20 nm. The morphology of nanosheets can be preserved to some extent after calcined at 500℃. The calcined titania nanosheets exhibit good photocatalytic activity in the degradation of phenol under UV and visible light irradiation.Egg albumin has been used as a template in water solution for the synthesis of titania. Uniform and well dispersed TiO2 nanoparticles with a diameter of ca.9 nm can be obtained. The as-prepared TiO2 nanoparticles are characterized by means of TEM, XPS, FTIR, TG-DTA and UV-Vis. Based on the characterization results, a possible mechanism of heat-induced denatured protein network as template matrix to fabricate TiO2 nanoparticles was carefully proposed, which is described as below:egg albumin solutions and amorphous TiO2 could form inorganic-protein conjugation complexes at room temperature. As temperature increased to 80℃, the protein molecules unfolded, denatured and formed a huge network matrix, with TiO2 embedding in the inner and absorbing on the outer surface of the matrix. At higher temperatures up to 150℃, the gelation network decomposed and uniform TiO2 nanoparticles were obtained after proper crystallization process. The as-prepared TiO2 nanoparticles exhibit superior photocatalytic activity in degradation of methyl orange under UV light irradiation.In the second part of work, casein has been applied as a bio-template for synthesis of zinc oxide, which acts as a potential photocatalyst, and some results have been obtained. ZnO particles with regular shape are obtained by means of bio-template and good photocatalytic activity was achieved.