Semiconducting optical properties of silver/silica mesoporous composite

The optical absorption properties were investigated for mesoporous silica loaded with different amounts (up to 5% in weight) of silver (Ag) nanoparticles (less than 4 nm in diameter) into its pores. In contrast to the previously reported glasses containing Ag particles, in this Ag particle-loaded silica no apparent surface plasmon resonance peak of Ag particle, other than an absorption edge, was observed. This composite exhibits the optical features of a semiconductor with direct band gap. The absorption edge shifts in the range from about 200 to about 700 nm with an increasing Ag loading amount up to 5% in weight, and hence, is controllable. Adsorption of oxygen in air on the surface of Ag particles within the pores, and scattering inside the porous structure were used to explain these results. (C) 1998 American Institute of Physics. [S0003-6951(98)04145-X].