Abstract:

The changes of chemical states of sulfur element in photographic gelatin before and after electroless depositions are studied using in situ Ar+ beam sputtering and ESCA scanning techniques of X-ray Photoelectron Spectroscopy in this paper. The depth distributions of copper and gold within electrically conductive layer produced by electroless copper deposition are carried out, and the mechanism of electroless copper deposition catalyzed by gold in photographic gelatin is investigated. The results indicate that under acidic condition(pH=3.20), methionine sulfone in gelatin macromolecule still having relatively high reducing power and methionine of gelatin macromolecule, which are both oxidized to methionine sulfoxide, reduce Au3+ finally to colloidal gold which is the catalytic center of electroless copper deposition at the initial stage of reduction. Afterwards the reduction deposition of Cu2+ continues because of the autocatalysis of new-formed copper. Under basic condition (pH=12.50) in the process of electroless deposition, methionine sulfoxide in gelatin is partly reduced to methionine by reductive agent HCHO.

Key words: Photographic gelatin, Reducing power, Electroless copper deposition, Depthprofiling, Chemical state