Visible illumination to a rhodamine B (RhB) aqueous solution containing powdery AgBr results in
N-deethylation of RhB and formation of metallic Ag in AgBr. The formal quantum efficiencies for these two processes,
FQE (-
Et) and
FQE (
Ag), have been measured under various conditions. In O
2-free suspensions the ratio
FQE (
Ag)/
FQE (-
Et) was roughly 2. This establishes a stoichiometry of [reduced Ag
+]/[injected electron]≅1, because single
N-deethylation requires removal of two electrons from a RhB molecule. Aeration of the suspension did not affect
FQE (-
Et), but significantly lowered
FQE (
Ag) due to the competition for electron capture between interstitial Ag
+ and surface-adsorbed O
2. Doping of AgBr with Cd
2+ influenced
FQE (-
Et) in O
2-free suspensions. For nine photographic dyes, a good correlation exists between the interfacial energetics and the
FQE (
Ag) value by visible illumination; a highest value (≅8%) of the latter was found for erythrosine in an O
2-free medium. Three desensitizing dyes, methylene blue, phenosafranine, and malachite green, gave
FQE (
Ag)≅0 at 580-600 nm, but suppressed the
FQE (
Ag) value at an intrinsic absorption wavelength of AgBr (435nm).
抄録全体を表示