出版社：The Society of Photographic Science and Technolgy of Japan
摘要：Thin film of silver alginate, silver salt of a typical high molecular weight carboxylic acid in nature, was decomposed by 253.7 nm light from a 15W low-pressure mercury lamp. As a primary photochemical process, one electron transfer from the carboxylate ion to the bound Ag+ ion has been assumed, which gives rise to silver atom and carboxyl radical. When the silver alginate film was photolyzed in wet air at room temperature, a clear silver mirror was formed on the irradiated surface. Photolytic silver had a tendency to precipitate on the irradiated side of the film despite relatively homogeneous absorption of 253.7 nm light by the silver alginate film. To examine the mechanism of a “segregation-like” behavior of photolytic silver, we have introduced a simple diffusion model which allows diffusion and deposition of silver atoms and clusters in the film and on the irradiated surface. It was found that three parameters, tinie constant of the formation of photolytic silver, τ, of 1000 s, rate constant of deposition in the film, k, of 10-3S-1, and diffusion coefficient, D, of 10-10cm2S-1, are suitable for photochemical formation of silver metal film on the film surface. This model could be successfully applied to vacuum photolysis of the silver alginate film in which the main product is not the silver metal film but either colloidal silver particles (room temperature) or large silver clusters (liquid nitrogen temperature) distributed rather uniformly in the polymer film.
