Investigations on the Photoinduced reactions of certain Porphyrins and Phycoerythrin with TiO2 and metal-TiO2 nanoparticles and calf thymus DNA with TiO2 nanoparticles

Abstract

Photochemistry is concerned with the absorption, excitation and emission of photons by atoms, molecules, ions, etc. The interaction of an electronically excited molecule with a second species in its ground state often leads to new, interesting, photophysical and photochemical processes. Photochemistry also provides some fascinating insights into the way in which chemical reactions occur. It finds applications including solar energy conversion, photocatalysis, photography, photopolymerization, the production of photodegradable polymers and in organic synthesis an exciting and developing area is the use of photochemistry to provide novel medicinal treatments. This thesis deals with investigations on the Photoinduced reactions of certain Porphyrins and Phycoerythrin with TiO2 and metal-TiO2 nanoparticles and calf thymus DNA with TiO2 nanoparticles. TiO2 and metal-TiO2 nanoparticles were prepared by the literature method and characterized by using Scanning and Transmission Electron Microscopic measurements as well as X-Ray Diffraction analysis. Various spectroscopic techniques such as UV-visible absorption, steady state and time resolved fluorescence and transient absorption flash photolysis were used to study the interaction of porphyrins, phycoerythrin and DNA with M-TiO2. Adsorption of porphyrins and phycoerythirn through their anchoring groups on the surface of colloidal TiO2 and resulted the formation of ground state complex has been observed. The apparent association constants were calculated from both absorption and fluorescence methods and they agreed well. The type of quenching whether it follows dynamic or static has been suggested and proved by steady state and time resolved fluorescence techniques respectively. The mechanism of fluorescence quenching whether it follows energy or electron transfer has also been confirmed by energy level diagrams as well as transient absorption flash photolysis measurements.