Spectroscopic investigations of interaction between TiO₂ and newly synthesized phenothiazine derivative-PTA dye and its role as photo-sensitizer

Interaction of TiO₂ nanoparticles (NPs) on newly synthesized phenothiazine derivative-(E)-2-cyano-3-(10-decyl-10H-phenothiazin-7-yl) acrylic acid (PTA dye) has been studied using absorption, fluorescence and electrochemical techniques. From the results of absorption spectra of PTA dye in the presence of TiO₂ NPs and the magnitude of association constant (k_a) determined from Benesi-Hildebrand theory, strong association between the PTA dye and TiO₂ NPs was confirmed. Fluorescence study, under both steady and transient states, reveals the energy transfer between PTA dye and TiO₂ NPs as dynamic phenomenon in ethyl acetate. A study of Rehm-Weller theory indicates the predominant electron transfer process between PTA dye and TiO₂ NPs in polar solvent (Acetonitrile) than in less polar solvent (Ethyl acetate). Electron transfer process has been exploited in solar energy harvesting applications by fabricating PTA dye sensitized solar cell. Photovoltaic energy conversion efficiency (η) and fill factor (FF) of PTA dye were found to be 1.24% and 0.54 respectively under AM 1.5 irradiation (1000 W/m²).