One-pot synthesis of M (M = Ag, Au)@SiO2 yolk–shell structures via an organosilane-assisted method: preparation, formation mechanism and application in heterogeneous catalysis

Abstract

We demonstrate the fabrication of yolk–shell catalysts consisting of a single M (M = Ag, Au) nanoparticle encapsulated within a hollow mesoporous organosilica shell via an organosilane-assisted strategy. The advantages of our method lie in its good controllability of the void space as well as the thickness of the mesoporous shell. The M@CTAB/SiO₂ synthesized through a modified Stöber method can transform to yolk–shell structures after adding (3-aminopropyl)trimethoxysilane (APTMS)/TEOS or (3-aminopropyl)triethoxysilane (APTES)/TEOS into the synthetic medium. We give unambiguous evidence that the middle CTAB/SiO₂ layer transforms into a less dense APTMS-rich organic–inorganic layer which was selectively removed in alkaline aqueous solution, while the amino-functionalized hybrid shells remain intact. Moreover, we discuss the role of alkylamino groups in the shell in the transformation from Ag@SiO₂ nanorattles to hollow structures when impregnating the as-synthesized Ag@SiO₂ nanorattles in HAuCl₄ aqueous solution. The nanorattles also exhibit high catalytic activity for the catalytic reduction of p-nitrophenol.