Characterization of sonochemically prepared silver–silica monolithic mesoporous nanocomposite

Ag/SiO2 mesoporous nanocomposite was prepared by a simple impregnation of the preformed monolithic porous silica in silver nitrate aqueous solution followed by ultrasonic irradiation of the liquid–solid mixture under Ar atmosphere. The particles are determined from HRTEM, Uv-vis absorption, and TEM analyses. It is found that the encapsulated metal particles are smaller in size than those formed almost simultaneously in the corresponding soaking solution. The employed mesoporous host has several roles in the preparation. It allows for uniform dispersion and encapsulation of Ag particles, and controls the particle sizes with narrow distribution that is determined by the pore diameter (say, less than 10 nm mostly). The proposed mechanism of noble Ag nanoparticles formed within pores of mesoporous silica is discussed. It is assumed that the longer-lived carriers of reducing power caused by the acoustic cavitation at the surface or near surface of porous monoliths is believed to play a major role in this pore doping processing.