Tailored TiO2 nanoparticles by means of template and microemulsion routes

TiO2 materials with tailored pore size and particle dimensions, high specific surface area, and well-defined crystalline frameworks have potential applications in several fields such as solar energy conversion, photocatalysis, catalytic production of gases, and Li-ion batteries. Therefore, a great deal of efforts has been devoted in recent years to the development of new synthetic routes that allow the relevant morphological properties of titania powders to be controlled.1,2 In the present work, two synthetic methods have been optimized in order to obtain titania particles with controlled structure, morphology and surface state: a template route3,4 and a microemulsion mediated method,5,6 both starting from alkoxide precursor in hydroalcoholic medium. In the template route, a block copolymer employed as a structure-directing agent is added in the pre-synthesized titania nanoparticulate sol. Alternatively, the titania nanoparticles are synthesized using a reverse microemulsion system containing surfactant and co-surfactant, water and non-polar solvents.7 All samples are characterized under the structural (XRPD), morphological (BET, HRTEM), optical (DRS) and spectroscopic (XPS, Raman) points of view. Selected samples are tested for their photocatalytic activity. The effects of several synthetic parameters, such as the polymer content, the role of the surfactant, the evaporation method and the annealing conditions, on sample morphology and surface/bulk properties are discussed.