Reversible Transformations Of Silver Oxide And Metallic Silver Nanoparticles Inside Sio_2 Films

摘要

Reversible transformation of silver oxide and metallic nanoparticles inside a relatively porous silica film has been established. Annealing of Ag-doped films in oxidizing (air) atmosphere at 450 ℃ yielded colorless films containing AgO_x. These films were turned yellow when heated in H_2-N_2 (reducing atmosphere) due to the formation of Ag nanoparticles. This yellow coloration (due to nano Ag~0) and bleaching (conversion of Ag~0 → Ag~+) are reversible. Optical and photoluminescence spectra are well consistent with this coloration and bleaching. The soaking test of the air-annealed film in Na_2S_2O_3 solution supports the presence of Ag~+. Grazing incidence X-ray diffraction and transmission electron microscopy studies reveal the formation of Ag-oxides and Ag nanoparticles in the oxidized and reduced films, respectively.