AMBIENCE-INDUCED ALTERNATING CHANGE OF OPTICAL-ABSORPTION FOR THE POROUS SILICA HOST LOADED WITH SILVER NANOMETER PARTICLES

Reversible change of optical absorption with alternating exposure to a mbient environment with high relative humidity and thermal annealing a t 573 K to 973 K is reported for the porous silica host dispersed with silver nanometer particles within its pores. A phase, silver silicate was found at the interface between pore walls and silver particles wi thin pores. The formation of the interface phase is responsible for th e ever-increasing absorption peak at around 410 nm and back ground abs orption in the whole measured region. From optical absorption measurem ents, the formation amount of the interface phase was found to be subj ect to a power function of exposure time to a given ambience. This int erface phase can be eliminated by subsequent annealing at 573 K to 973 K. The alternating change of optical absorption is explained by forma tion and decomposition of the interface phase induced by a given ambie nt condition.