Adam Argondizzo

Allen G10A Desk #1
(412) 648-8871


Titanium Dioxide has been a material of interest for almost fifty years due to its ability to photocatalyze chemical reactions on its surface under UV excitation. This thesis discusses the properties of electrons in the conduction band of TiO2, which are probed by a variety of new experimental techniques as well as novel combinations of techniques. These measurements give insight into the electronic and photocatalytic properties of TiO2, as well as characterizing a number of new excitations that have not been detected until now. The discovery of a transition from an occupied Ti-3d defect band of t2g symmetry to an unoccupied eg symmetry d band (d-d transitions) in TiO2 gives a better understanding of the electronic structure in the surface region as well as providing a new method for probing the distribution of defect carriers in the bulk and surface. Additionally this newly discovered transition allowed for the identification and characterization of the polaron character of the initial state in photoemission process. A polaron state has been predicted by the theory, but experimental verification has been hard to achieve by spectroscopic means. Finally the interactions of molecules including CO2, CH3OH, and O2 with the defect states was characterized by observing the effect of molecular adsorption on the d-d transitions. By varying the temperature, surface preparation and coverage of the adsorbates, the electron dynamics and interactions of these molecules were studied and produced an increased understanding of the importance of molecular interactions in regards to photoactivity of the surface. This work advances the general knowledge of TiO2 and gives a solid framework for determining the complex electronic interactions that define its photocatalytic activity.



Graduate Advisor

Hrvoje Petek