Synthesis and structural and optical properties of mesoporous silica containing silver nanoparticles

Mesoporous silica with silver (Ag) nanoparticles within its pores was synthesized by thermal decomposition of silver nitrate. The structure of this new material was examined by x-ray diffraction, transmission electron microscope and Brunauer - Emmett - Teller techniques, and its optical absorption spectra were measured. It has been shown that Ag nanoparticles are isolated from each other and highly uniformly dispersed in pores which are less than 8 nm in diameter. The size of Ag particles follows a log-normal distribution function. Ag particle doping leads to a large red shift of the absorption edge and the edge position can be controlled across the whole visible region by varying the amount of Ag doping. There is no surface plasmon resonance peak other than an absorption edge on the absorption spectra. These facts are explained in terms of interband absorption and dipole interaction of Ag particles in silica, and interaction between pore walls and Ag particles.