Temperature-dependent electron-transfer quenching of dye monomer fluorescence on octahedral silver bromide grains

Abstract

At very low coverage, in the range of 0.005, fluorescence decay of dye molecules, 3,3'-diethylthiacanine iodide, is independent of coverage on the (111) face of monodisperse octahedral AgBr grains in a gelatin emulsion. Fluorescence decay of the adsorbed monomers is monoexponential from room temperature down to 5 K. The decay time increases from 56 ps at room temperature to 550 ps at 100 K, and it remains constant below 100 K. When the decay is fast, ground-state dye molecules are consumed and silver clusters are formed in the AgBr grains. The short decay times above 100 K are attributed to electron transfer from the excited singlet state of adsorbed dye monomers to the empty conduction band of AgBr