Using femtosecond time-resolved upconversion fluorescence spectroscopy technology, the fluorescence decay properti-es of J-aggregates of anionic-cationic cyanine dye, anionic cyanine dye and cationic cyanine dye adsorbed on surfaces of the cubic AgBrI grains are investigated. The kinetics of the electron transfer and the spectral sensitization property are analyzed in detail. The experiment setup in our work is the fluorescence upconversion(also called fluorescence frequen-cy generation)spectrometer. The time-resolution reaches about 140 fs. Anionic-cationic cyanine dye studied in our ex-periment is new-type cyanine dye, which formed by anionic cyanine dye reacting with cationic cyanine dye.
By contrary of the sensitization performances of several cyanine dyes, It is found that the sensitization performance of cubic AgBrI sensitized by anionic-cationic dye is marked higher than those of anionic cyanine dye, cationic cyanine dye and the mixture of anionic cyanine dye and cationic cyanine dye. The fluorescence decay curves of cyanine dyes J-aggregates obtained by femtosecond fluorescence upconversion spectrometer are analyzed as a sum of double exponent-ials, and the fitting curves consist of a fast and a slow component. Because of the large amplitude, this fast decay should be mainly attributable to the electron transfer from dye J-aggregates to conduction band of AgBrI. The electron transfer velocity of anionic-cationic cyanine dye J-aggregates is larger than those of anionic cyanine dye, cationic cyanine dye and the mixture of anionic cyanine dye and cationic cyanine dye, which is consistent with the results of the sensitization performance and the photoelectron lifetime. Dye1 has higher sensitizing efficiency than other cyanine dyes on the cubic AgBrI grains.
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 (68-99% for T-grains and 68-80% 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.