Effect of TiO 2 nanoparticles on some photophysical characteristics of ketocyanine dyes.

The effect of titanium dioxide (TiO2 ) nanoparticles (NPs) on photophysical characteristics of 2,5-di[(E)-1-(4-dimethylaminophenyl) methylidine]-1-cyclopentanone (2,5-DMAPMC) and 2,5-di[(E)-1-(4-diethylaminophenyl)methylidine]-1-cyclopentanone (2,5-DEAPMC) ketocyanine dyes has been studied using absorption, steady-state and time-resolved fluorescence spectroscopy. The magnitudes of association constants determined based on modified absorption spectrum of dyes due to the presence of TiO2 NPs indicate the interaction of TiO2 NPs with dye molecules. The quenching of fluorescence intensity of dyes by TiO2 NPs is observed and it follows linear Stern-Volmer (S-V) equation. The magnitude of quenching rate parameter suggests the involvement of static quenching mechanism. The involvement of electron transfer process in reducing fluorescence intensity of dyes has been discussed. Also, varying influence of TiO2 NPs on two dyes is explained based on the presence of different alkyl substituent in two dyes.