Cooperative sensitization by reduction and chemical sensitization in AgX core-shell emulsions

Cubic core-shell AgBr and AgBrI emulsions prepared by the twice emulsified method were used to observe the cooperative sensitization of reduction sensitization in the core and sulfur-plus-gold sensitization on the surface of core-shell grains through a space separation of different sensitizing centres by a AgBr shelled layer. The results showed: (1) that core-shell emulsions doped by Ag₂ centres in cores reduced by DMAB exhibited a remarkable increase in sensitivity relative to the corresponding undoped emulsions; (2) that I_- ions in AgBrI grains did not affect the sensitization of internal Ag₂ centres, but were beneficial to the inhibition of fog density; (3) cooperative sensitization by the internal reduced Ag₂ and the surface S+Au sensitizations was considered to result from two different mechanisms, i.e. trapping holes by the former and concentrating electrons by the latter, both of which were beneficial to the efficiency of latent image formation.