The Effect of Three Different 4-hydroxy-1,3,3a,7-tetraazaindenes on the Melt pAg, Ionic Activation Energies and Photocarrier Responses of an AgBr Emulsion

Abstract

Melts and coatings of a 0.3-μm octahedral AgBr emulsion were prepared with four concentrations of each of three different 4-hydroxy-1,3,3a,7-tetraazaindenes (TAIs). pAg measurements were made on the melt samples and ionic thermocurrent and radiofrequency photoconductivity measurements were made on the coated samples. The melt pAg (i.e., a measure of the Br− desorbed from the grain surface) increased as the pKsp and the concentration of the TAI added to the sample increased. The concentration of desorbed Br− measured as a function of TAI concentration was consistent with the proposal that TAI anions compete with Br− for adsorption to the surface of the grain. The ionic activation energy for formation of interstitial silver ions and the photoelectron lifetime increased as the pKsp and the concentration of TAI− increased. A linear correlation between desorbed Br− and ionic activation energy was observed. The log of the rate constant for electron trapping decreased linearly as the ionic activation energy increased. The presence of TAI did not affect the photohole response. For TAIs with pKa<5.0, these effects were independent of pH for pH values between 4.5 and 7.0, whereas when pKa > 6, these effects decreased with decreasing pH.