Kinetics study of ultrafast electron transfer from sensitized dyes to silver halide microcrystals

Spectral sensitization micromechanism of cyanine dyes J-aggregate adsorbedon the tabular and cubic AgBr microcrystals with different dyeconcentrationsis studied by using picosecond time-resolved fluorescence spectroscopy, andthe dependences of electron transfer and spectral efficiency sensitizationon different conditions are analysed in detail. With the steadyspectroscopy, the wavelengths of absorption and fluorescence of J-aggregateadsorbed on AgBr microcrystals are found to shift to red relative to dyemonomer. The spectrum of fluorescence has a red shift relative to theabsorption peak. With the time-resolved fluorescence spectroscopy, thefluorescence decay curves of cyanine dyes J-aggregate adsorbed on thetabular and cubic AgBr grains are found to be fitted well by adouble-exponential decay function. The fitting curves consist of a fast anda slow component. Because of the large amplitude of the fast component, thisfast decay should be attributable mainly to the electron transfer fromJ-aggregate of dye to a conduction band of AgBr.