Nucleation and growth of cyanine dye J-aggregates on AgBr emulsion crystals studied by analytical color fluorescence electron microscopy

Cathodoluminescence images of 3,3'-bis-sulfopropyl-5,6,5',6'-dibenz-9-ethyl-oxacarbocyanine J-aggregates adsorbed on (100) surfaces of practical emulsion AgBr microcrystals were used to study nucleation, preferential adsorption, and growth. Nucleation of J-aggregates occurred when dye molecules were added to gelatin sols of AgBr microcrystals and the aggregate nuclei adsorbed to the surface of AgBr. Residual dyes in the solution worked to increase the size of existing aggregate nuclei on the surface and did not contribute nucleation of new aggregates. The temperature rise of solutions during aging led to normal size distribution of J-aggregates, suggesting that there is a most stable size of J-aggregates for given growing conditions. The surface selectivity of J-aggregates on adsorption was checked by comparing J-aggregation on AgBr cubes, octahedra, and cuboctahedra.