26. August 2014 at 12 in Physicums aud A106 will defend Urmas Joost his doctoral theses in materials science "Impurity and preparation dependent properties of titania thin films".
Senior Research Fellow Vambola Kisand, University of Tartu
Professor Mika Valden, Optoelectronics Research Centre, Tampere University of Technology
Titania (TiO2) is widely used in industry and our everyday life. It finds use as white pigment and anticaking agent in paints, plastic, paper and other consumer products. It also finds application in sunscreens as UV blocker and in foodstuff as colouring agent (E171).
Titania has been considered also as a perspective material for many advanced applications. It has been studied extensively as a promising photocatalyst, solar cell material, biocompatible material, material for anti-fogging and self-cleaning coatings. Nanostructure, crystal structure, purity and other qualities all play important roles in many of titania applications.
Influence of the different dopants and the substrate pretreatment to the sol-gel film structure and crystal phase composition was thoroughly investigated. It was demonstrated that exact crystal phase transition temperature and extent from anatase to rutile are highly dependent on the doping element and the substrate pre-treatment. Also during annealing the impurity element tends to segregate out of the titania matrix and form dopant rich regions on the surface of the film.
It was shown that the photoactivity of the TiO2 film depends on the choice of the impurity element and the nanostructure of the films. Beside titania sol-gel thin films also titania thin films consisting of premade nanoparticles were prepared and their photoactive properties were investigated. It was shown that thin titania films consisting of small premade nanoparticles exhibited enhanced photocatalytic and antibacterial properties. The films consisting of premade nanoparticles are simple to prepare and they are also efficient photocatalysts which means that they are potentially scalable to industrial level.