Aggregates in silica based matrices

Embedding nano-aggregates in silica based supports may be a usefull method to control their size and protect them against degradation. Some Some examp les are given to illustrate the potentiality of this method. Metal aggregat es can be obtained on reducing an oxide or salt dispersed in a silica gel o r by ion implantation in dense silica layers. In both cases the particles s ize can be controlled by the conditions of elaboration. Organic nano-crysta ls such as fullerenes and polydiacetylenes can be also incorporated in meso porous silica. In this case, the size of the crystals is controled by the s ite of the pores.