It is known that the spectral sensitivity (by a dye) of photographic emulsions increases when the emulsions are soaked in a concentrated AgNO
3 solution. This Ag
+ ion effect has also been identified with an electrochemical method as an increase in sensitized photocurrents, which are due to electron injection from photo-excited sensitizing dyes to AgX (X =Br or Cl) conduction band. The Ag
+ ion effect is considered to be based on an anodic shift of the conduction band of silver halide. In order to clarify the mechanism of the Ag
+ ion effect more precisely, the sensitized photocurrents were measured at various concentrations of Cl
- or Br
- ions, and they were generally found to be decreased with an increase in the concentration of halide ion. This halide ion effect can be considered as a reverse effect of the Ag
+ ion on the sensitized photocurrents. It can therefore be concluded that the Ag
+ ion and halide ion effects are based on anodic and cathodic shifts of the band edge of the silver halide, respectively.
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