Kinetics of Photochromic Induced Energy Transfer between Manganese-Doped Zinc-Selenide Quantum Dots and Spiropyrans

Fluorescence resonance energy transfer (FRET) is investigated with manganese-doped ZnSe nanoparticles (quantum dots) as long fluorescence lifetime donors and spiropyran molecules as acceptors. The kinetics of photochemical ring-opening reaction of spiropyran upon UV-illumination is exploited to achieve efficient quenching of the manganese fluorescence lifetimes at a low temperature of 78 K in methylcyclohexane/isopentane mixture. Modulation of the acceptor structure from closed to open form allows us to investigate the temporal decrease in donor lifetime accompanied with an increase in the efficiency of FRET transfer. A theoretical model proposed by us describes very well the experimental data, thus providing the intimate parameters of FRET transfer in the system quantum dot−dye molecule.