Aggregates of cyanine dyes: photographic problems

The aggregation of cyanine dyes on the surfaces of AgHal microcrystals is examined. It is shown that the photochemical activity of the aggregates in processes involving the spectral sensitisation of photographic materials is determined to a large extent by the occurrence of secondary dark reactions in which photoelectrons recombine with dye holes - the so-called type II dye self-desensitisation processes. The inhibition of the self-desensitisation of dyes increases the effectiveness of the spectral sensitisation, i.e. leads to supersensitisation. The principal mechanisms of the supersensitisation of photographic emulsions are discussed. The bibliography includes 149 references.