Sol-gel processing of silica-coated gold nanoparticles

Two procedures are presented which allow the homogeneous incorporation of silica-coated gold nanoparticles within transparent silica gels. Both UV-visible absorption spectra and transmission electron microscopy show that there is no aggregation of the metal particles during sol-gel transition. The optical properties of the gels are compared with those of the starting sols and interpreted on the basis of the porous structure of the gets and standard optical theories. Evidence is also shown of the potential of these methods for the preparation of gels with different particle sizes and shapes as well as with very high nanoparticle concentrations, which can be useful for several applications.