在照相明胶层中金催化的铜无电沉积

Electroless Copper Deposition Catalyzed by Gold in Photographic Gelatin Layer

利用X射线光电子能谱的原位氩离子束溅射和ESCA技术，研究了无电沉积前后照相明胶中硫元素化学形态的变化，对无电沉积所形成的导电膜进行了深度剖析，探讨了照相明胶层中金催化的铜无电沉积机理．结果表明：在酸性条件下（pH＝3．20），明胶大分子的蛋氨酸亚砜对AU3+仍具有较大的还原能力，明胶大分子的蛋氨酸、蛋氨酸亚砜将Au3+最终还原为胶态金，而蛋氨酸和蛋氨酸亚砜均被氧化为蛋氨酸砜．在无电沉积初期，胶态金作为催化中心引发铜的无电沉积，之后的反应为Cu2+在新生态铜的自催化下的还原沉积．在无电沉积过程的碱性条件下（pH＝12．50），明胶中的部分蛋氨酸砜又被甲醛还原为蛋氨酸．

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.