MORPHOLOGY AND STRUCTURE OF PHOTOSENSITIVE DYE J-AGGREGATES ADSORBED ON AGBR MICROCRYSTALS GROWN IN GELATIN

Though the cyanine dye J-aggregates carry the role to sense the exposi ng light in the silver halide photographic system, little research on the morphology of the aggregates in adsorption has been made with mode rn surface analytical methods. In this paper, we describe the size, ep itaxy, multi-layered array formation, nucleation and preferential adso rption, and irregular distribution of population between particles and the segregation on a particle, of J-aggregates adsorbed on AgBr grown in gelatin. We employed cathodoluminescence microscopy, low energy hi gh resolution scanning electron microscopy, and atomic force microscop y. Dye molecules aggregate together near the surface of AgBr and adsor b on the surface. The growth of adsorbed aggregates is controlled by t he diffusion of dye molecules from the surrounding solution. The popul ation of J-aggregates adsorbed on an AgBr particle varies from almost none to full coverage. Each aggregate is about (20-30) x (30-50) nm in size and is 2.1 nm thick for thiacarbocyanine with sodium ion, 1.04 n m for thiacarbocyanine with tosyl ion, and 0.5 nm for an oxacarbocyani ne. The aggregates connect their longer edges to each other to form ar rays, and the arrays build up multi-layered stacks. The arrays align p arallel and segregate to form terraces. The longer edges of J-aggregat es align along [210] on AgBr (100) or [632] on AgBr (111). (C) 1998 Wi ley-Liss, Inc.