Electron transfer dynamics of dye-55026 J-aggregate to AgBr grains studied by ultrafast fluorescence spectroscopy

摘要

Direct detection of the dynamics of photo-induced electrons in AgBr photographic system sensitized by dye-55026 was performed using picosecond time-resolved fluorescence spectroscopy. The dependence of the electron transfer rate on different conditions and microcosmic mechanism of electron transfer were analyzed. The experiment setup in our work was a system of high-speed streak photography (Streak Cameras) with a time-resolution of 5 ps. With stead spectroscopy, the peak of absorption and fluorescence of J-aggregation on AgBr grains both have a red shift contrast to monomer. On the same time the absorption spectrum band of J-aggregation becomes narrow. The fluorescence decay curves of J-aggregation on both the cubic and tabular AgBr grains (T-grains) were gained with different dye concentrations. These curves are fitted well by a sum of double exponential functions, which includes a fast and a slow component. Because of large amplitudes (68-99percent for T-grains and 68-80percent for cubic grains) of the fast decay (2.4-12.1ps for T-grains and 4.1-5.8ps for cubic grains) and the estimated quantum yield of the electron injection, this fast decay should be mainly attributable to the electron transfer from excited J-aggregation to conduction band of AgBr. At low concentration (<4.51mmol/molAg), the fluorescence decay lifetime for T-grains is longer than that for cubic grains. As the increase of the concentration, it will become more rapidly for T-grains than that for cubic grains.