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The effect of position of benzo group in coumarin derivatives, 5,6 benzo-4-azidomethyl coumarin (5BAMC) and 7,8 benzo-4-azidomethyl coumarin (7BAMC) during their interaction with TiO2 nanoparticles in ethyl acetate, tetrahydrofuran, butan-1-ol and acetonitrile solvents has been studied using different spectroscopic methods and electrochemical analysis. Benesi-Hildebrand plots indicate that nature of interaction between 7BAMC and TiO2 is 1:2 in solvent with low dielectric constant whereas for 5BAMC and TiO2, it is 1:1 in all the solvents. From the fluorescence quenching study and binding equilibria analysis, it is observed that interaction between 5BAMC and TiO2 depends on the dielectric constant of the solvent. Time resolved quenching study reveals that quenching is dynamic for 5BAMC in solvent with high dielectric constant. Whereas for 7BAMC, it is dynamic in solvent with low dielectric constant. Hence the nature of interaction of these two coumarin derivatives with TiO2 NPs is different. From electrochemical analysis, it is observed that, free energy change for electron transfer is more negative for 5BAMC-TiO2 compared to 7BAMC-TiO2 therefore quenching is more efficient for 5BAMC-TiO2 compared to 7BAMC-TiO2 system, which is also confirmed from fluorescence quenching studies. Non-radiative energy transfer rate is more than radiative energy transfer rate for both the systems according to FRET study. [ABSTRACT FROM AUTHOR]

In this paper, effect of titanium dioxide (TiO 2 ) nanoparticles (NPs) on newly synthesized phenothiazine dye i.e., ( Z )-2-cyano-3-(10-heptyl-10 H -phenothiazin-7-yl) acrylic acid (CPTA dye) has been studied using spectroscopic techniques such as absorption, fluorescence and electrochemical. Absorption spectra of CPTA dye in the presence of TiO 2 appears broadened without any shift in the absorption peaks which suggests possible interactions between the CPTA dye and TiO 2 NPs and absence of complex formation. These inferences were validated by determining association constant ( k a ) according to Benesi–Hildebrand theory. In order to see the role of fluorescence quenching, S-V theory was invoked, it was observed that phenomenon of quenching follows dynamic or collisional process under both steady and transient states. Experimentally determined magnitude of bimolecular quenching rate parameter is equal to the order of maximum collisional quenching rate parameter. Role of energy transfer between CPTA dye and TiO 2 NPs has been discussed using Rehm-Weller theory. From this it reveals that electron transfer process is more pronounced under more polar solvent (Methanol) than less polar solvent (ethyl acetate). Electron transfer mechanism has been exploited in solar energy harvesting applications by fabricating solar cell sensitized by CPTA dye. From this, it was observed that the efficiency and fill factor of fabricated DSSC was 2.15% and 0.58 respectively under optimized conditions and solar harvesting property of newly synthesized phenothiazine derivative of CPTA dye is the first report. [ABSTRACT FROM AUTHOR]