Electroless copper deposition in the photographic gelatin layer

An electroless copper deposition process consisting of two stages: (1) form ing gold catalytic centers, and (2) electroless copper deposition, was stud ied in this paper, The changes of the chemical state of sulfur in photograp hic gelatin before and after electroless copper deposition were studied by X-ray photoelectron spectrometry. The depth distribution of copper and gold within the electrically conductive layer produced by electroless copper de position was determined and the mechanism of electroless copper deposition catalyzed by gold in the photographic gelatin layer was discussed. The resu lts indicated that under acidic conditions (pH 3.20), methionine sulfoxide in the gelatin macromolecule had relatively high reducing power When the ge latin sample was immersed into the chloroauric acid solution, methionine su lfoxide and methionine were oxidized to methionine sulfone, reducing Au3+ t o colloid gold which acted as the catalytic center at the initial stage of the electroless copper deposition. During the electroless deposition the re duction of Cu2+ by HCHO could continue, and el en the copper completely cov ered the gold because the reaction was autocatalyzed by newly formed copper , (C) 1999 The Electrochemical Society. S0013-4651(98)06-006-6, All rights reserved.