Photophysics of a molecular rotor inside the block co-polymers

[Display omitted] •Twisting dynamics of a molecular rotor AuO was reported.•Fluorescence lifetime value of AuO was increased on addition of both the block co-polymers.•F127 can be used as good drug delivery system as compared to F108.•On increasing the temperature some AuO molecules drive out from the micelle core to the bulk water. 4 Auramine O, an ultrafast molecular rotor, a diphenylmethane cationic dye is weakly fluorescent in aqueous media. In this article the excited state twisting dynamics of Auramine O in Pluronic F127 and F108 block co-polymer have been reported by using different types of spectroscopic techniques. We observed interesting ground state as well as excited state phenomenon due to the addition of block co-polymers to the aqueous solution of Auramine O. The fluorescence intensity gradually increases with increase in the concentration of both the block co-polymers along with blue shift in the emission maxima. The average lifetime value of Auramine O enhanced significantly with the addition of both the block co-polymers, respectively. Such changes in the spectral properties of Auramine O in the presence of block co-polymers indicate presence of Auramine O inside the micelle. From fluorescence measurement we have also determined partition coefficient of Auramine O between the micellar environment and the aqueous medium. It was observed that in the case of F127 partition coefficient value is higher compare to F108. We have measured the effect of temperature on the photophysics of Auramine O in the presence of block co-polymers. It was observed that the spectroscopic properties of Auramine O/micelle complex are highly dependent on temperature.