Preventing sintering of Au and Ag nanoparticles in silica-based hybrid gels using phenyl spacer groups

Gold and silver metal salts were reduced in the presence of phenylethylthiol as capping agent to form metal nanoparticles of 2.1–2.4 nm diameter. These clusters were then added to a sol–gel process using phenyltriethoxysilane as a hybrid component to optimize the dispersion of the metal particles in the matrix. The encapsulated metal particles grow in the sol–gel process to an average diameter of 6 nm. This method permits a controlled variation of the materials' porosity by simply regulating the synthesis pH values. Optimized mixed micro-/mesoporous materials are obtained at pH = 6. The metal particles and the matrix are thermally stable, and catalyze CO oxidation.