Facile synthesis of monodispersed Au nanoparticles-coated on Stöber silica

• The 2–4 nm colloidal gold nanoparticles are highly dispersed onto Stöber silica.
• Neither surfactant nor catalytic-poisonous compound is applied during coating.
• Small gold nanoparticles still exist after calcined at 300 °C for 4 h.
• Calcined gold particles are further fixed on silica by removing hydroxyl species.
• This method provided possibility for SiO2@Au-like materials used for catalysis.

The homogeneous and tiny colloidal gold nanoparticles (2–4 nm) were utilized as the precursor and coated onto the non-porous Stöber silica by a facile method. For the first time, the coating process is fulfilled without either organosilanes or thiols compounds, which was invariably applied for Stöber silica to fix the gold particles and thus limited the application of the gold material in catalysis field. For better understanding, the mechanism of the synthesis process was further analyzed. During the coating process, the gold nanoparticles protected by polyvinyl alcohol (PVA) surrounded with hydroxyl species were higher dispersed on the surface of Stöber silica. The following calcination facilitated the combining removal of hydroxyl species in both PVA and silica structure, and the gold nanoparticles anchored by residual hydroxyl species on the surface of Stöber silica. Major of the small particles about 3 nm remained their sizes even after calcination, which was just the satisfied size for some reactions such as CO oxidation. This simple and environmental synthesis method provided an available strategy for synthesizing gold catalysts with very small and orderly sizes that can be used for further investigation in the catalysis field.

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