Spectral and kinetic luminescence characteristics of emulsion microcrystals AgBr(I) with adsorbed organic dye.

To reveal the structure of tunnel-luminescence centres in AgBr(I) emulsion microcrystals (EMCs), we perform spectro-sensitometric and kinetic studies of their low-temperature (T = 77 K) luminescence. The luminescence characteristics depending on the binder, the presence and the nature of sensitizing additions (dyes) and the oxygen treatment are studied quantitatively. Special attention is paid to the comparative studies of the Stokes and dye-induced anti-Stokes luminescence components in the AgBr(I) EMCs. When the dye-sensitized AgBr(I) EMCs distributed in the polyvinyl alcohol are excited by the light photons with the energies corresponding to the intrinsic absorption region of the EMCs (λmax ≈ 460 nm), the kinetics of the luminescence band centred at the wavelength λmax ≈ 560 nm is monotonic. On the contrary, upon excitation by the photons corresponding to the absorption region of a J-aggregated dye (λmax ≈ 680 nm), the kinetics of the anti-Stokes glow (λmax ≈ 560 nm) is characterized by a rapid 'flash' followed by a gradual decrease to a stationary level (a 'flash enhancement'). These results indicate that a non-equilibrium transfer of charge carriers from the dye, which is adsorbed on the EMC surface, to the EMC volume depends essentially on the binder. If gelatine is the binder, this process is significantly affected by the oxygen adsorption, whereas the resulting effect depends on the aggregate form of the adsorbed dye. Understanding of physicochemical processes that govern the luminescence centres should enable one to control the structural transformations of the donor-acceptor complexes and clusters, which are responsible for the unique photometric properties of AgBr(I), and optimize their parameters for various applications in optoelectronics, holography, photographic materials science, optical sensors and solar energy systems. [ABSTRACT FROM AUTHOR]