Energy Transfers between Crystals and Adsorbed Dyes II Effect of Concentration on Efficiency of Sensitization*

The effect of density of sensitizer molecules adsorbed on a cadmium sulfide surface on the efficiency of sensitization by them has been studied for malachite green, pinacyanole, erythrosin, and 3,3′ diethylthiacarbocyanine. The losses in the case of the first two are drastic and can be accounted for directly in terms of the properties of the solid dyes. The detailed process of electron transfer from a dye molecule or aggregate to a crystal substrate is considered briefly. It is concluded that there should in general be a loss of efficiency in passing from the state in which molecules are adsorbed singly and broadside, to that in which they are adsorbed as a close-packed aggregate.