Odosiy L. New lightsensitive photocatalytic materials: heterostructures of titanium(IV) oxide and a polymethine dye

Thesis for scientific degree candidate of chemical science, specialty 02.00.04 - physical chemistry. - Yuriy Fedkovych National University of Chernivtsi, 2016. The thesis deals with experimental data related to design methods of the wide-zone lightsensitive systems by construction of the heterostructures containing titanium(IV) oxide and a polymethine dye, which exhibit advanced optical and redox properties. A character of dependencies between spectral, electrochemical and energy characteristics of the dyes on one hand and their structure and the polymethine chain length on the other have been found. The oxidation and reduction potentials of the dyes were measured, the HOMO and LUMO energy values have been calculated and the possibilities of utilization of the dyes as TiO2 sensitizers were discussed in the context of development of new highly effective redox systems. Particular features of the dyes' sensitizing activity, energy transformation and electron transfers were also extensively analysed for the processes induced by light from different spectral zones. An influence of titanium(IV) oxide on the dye-sensitizer has been analyzed and a mechanism of photocatalytic activity of the heterostructures was proposed. Then the mechanism has been verified by investigation of the redox processes of methylene blue reduction and iodide ions oxidation. Finally, the redox processes efficiency changes with the dye's concentration and nature have been found and explained.