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Fabrication of Ellipsoidal Silica Yolk-Shell Magnetic Structures with Extremely Stable Au Nanoparticles as Highly Reactive and Recoverable Catalysts.

Research paper by Jiasheng J Fang, Yiwei Y Zhang, Yuming Y Zhou, Shuo S Zhao, Chao C Zhang, Hongxing H Zhang, Xiaoli X Sheng, Kunpeng K Wang

Indexed on: 02 Mar '17Published on: 02 Mar '17Published in: Langmuir



Abstract

A novel strategy was reported for the fabrication of yolk-shell magnetic MFSVmS-Au nanocomposites (NCs) consisting of double-layered ellipsoidal mesoporous silica shells, numerous sub-5 nm Au nanoparticles (NPs), and magnetic Fe central cores. The hierarchical FSVmS NCs with ellipsoidal α-Fe2O3@mSiO2/mSiO2 as yolks/shells were firstly prepared through the facile sol-gel template-assisted method, and plenty of extremely stable ultrafine Au NPs were post encapsulated within interlayer cavities through the unique deposition-precipitation method mediated with Au(en)2Cl3 compounds. Notably, ethylenediamine ligands were used to synthesize the stable cationic complexes [Au(en)2]3+ that readily underwent the deprotonation reaction to chemically modify on negatively charged mesoporous silica under alkaline conditions. The subsequent two-stage programmed hydrogen annealing initiated the in-situ formation of Au NPs and reduction of α-Fe2O3 into magnetic Fe, where the synthesized Au NPs were highly resistant to harsh thermal sintering even at 700℃. Given its structural superiority and magnetic nature, the MFSVmS-Au was demonstrated as a highly efficient and recoverable nanocatalyst with superior activity and reusability toward the reduction of 4-nitrophenol to 4-aminophenol, and the pristine morphology still retained after six recycling tests.