Synthesis of novel ultrasmall Au-loaded magnetic SiO2/carbon yolk-shell ellipsoids as highly reactive and recoverable nanocatalysts

Abstract

A facile synthetic strategy was developed for novel Au-loaded magnetic SiO2/carbon yolk-shell ellipsoids (Fe@SiO2-Au@H-C) composing of magnetic Fe@SiO2 yolks, mesoporous carbon shells and numerous sub-3 nm Au nanoparticles (NPs). The SiO2/polymer resin double-shell structures (Fe2O3@SiO2@RF) were prepared by the one-pot extended Stöber method, followed by carbonization-hydrothermal etching to attain hierarchical yolk-shell architectures (Fe2O3@SiO2@H-C) with mesoporous carbon shells. The H2 annealing reduction based on the unique deposition-precipitation method mediated with Au(en)2Cl3 compounds was post conducted to accomplish both the in-situ encapsulation of ultrasmall Au NPs and integration of inner entrapped Fe cores with strong magnetism. Hybrid formation of double-shell hollow structures and amorphous yolk structures was discernable in the yolk morphologies of Fe@SiO2-Au@H-C ellipsoids, and the embedded Au NPs displayed excellent dispersibility and enhanced thermal stability due to the protection of ethylenediamine stabilizer. With the merits of configural advantages and enhanced synergy of dual movable Au-embedded yolk/shell structures, the Fe@SiO2-Au@H-C ellipsoids as nanocatalysts were shown with outstanding activity and reusability toward the reduction of 4-nitrophenol and organic dyes, and appeared highly recoverable with well-preserved initial morphologies during the recycling processes.