照相明胶与化学增感剂相互作用的XPS研究

本文采用X射线光电子能谱技术研究了两种照相明胶与化学增感剂相互作用的机理.当两种照相明胶样品在HAuCl₄溶液中反应5min后,明胶中的蛋氨酸、蛋氨酸亚砜均被氧化为蛋氨酸砜.与此同时,明胶吸附的大部分Au³⁺被还原为Au⁺,并且Au⁺以络合形态存在于明胶之中.根据与AuCl₃反应之后明胶中Au³⁺与Au⁺的比例,法国明胶的还原性略高于包头明胶.添加到明胶中的Na₂S₂O₃能将明胶大分子所含的蛋氨酸亚砜全部还原为蛋氨酸.S₂O₃^2-、蛋氨酸和蛋氨酸砜可以稳定共存于明胶体系之中,外加的S₂O₃^2-的还原性高于明胶中蛋氨酸、蛋氨酸亚砜的还原性.添加Na₂S₂O₃后的两种照相明胶均可以将其溶胀吸附的Au³⁺全部还原为胶态金.此时,参与氧化还原反应的主要基团是S₂O₃^2-而非明胶中的蛋氨酸残基.由于Na₂S₂O₃的添加,照相明胶对AuCl₃的还原能力增强.

STUDY ON THE INTERACTION BETWEEN PHOTOGRAPHIC GELATINS AND CHEMICAL SENSITIZERS BY XPS

The mechanism of interaction between two kinds of photographic gelatins and chemical sensitizers was studied by X-ray Photoelectron Spectroscopy. After the gelatin samples had been immersed into the chloroauric acid solution for 5 minutes, methionine and methionine sulfoxide in gelatins were oxidized to methionine sulfone, reducing most part of Au3+ to Au+ which was coordinated by gelatin macromolecule. According to the ratio of Au3+ to Au+ in gelatins, the reducing capacity of Roussalot gelatin is slightly higher than that of Baotou gelatin. Addition of sodium thiosulfate to gelatins, methionine sulfoxide was reduced to methionine. Thiosulfate, which is stronger reducer than methionine and methionine sulfoxide, could coexist steadily with methionine and methionine sulfone in gelatins. Two kinds of photographic gelatins added with Na2S2O3 can reduce Au3+ to colloid gold. In this oxide-reduction reaction, the main reducer is thiosulfate but not methionine of gelatins. The reducing capacity of photographic gelatins to chloroauric acid increased when the thiosulfate was added.