Magnetic TiO2–SiO2 hybrid hollow spheres with TiO2 nanofibers on the surface and their formation mechanism

Xiangcun Li; Vijay T. John; Gaohong He; Jibao He; Leonard Spinu

doi:10.1039/C2JM31967E

Magnetic TiO₂–SiO₂ hybrid hollow spheres with TiO₂ nanofibers on the surface and their formation mechanism†

Xiangcun Li,*^ab Vijay T. John,^b Gaohong He,^a Jibao He^b and Leonard Spinu^c

* Corresponding authors

^a State Key Laboratory of Fine Chemicals, The R&D Center of Membrane Science and Technology, Dalian University of Technology, Linggong Road, 2#, Dalian, China
E-mail: lixiangcun@dlut.edu.cn
Fax: +86-0411-84986291
Tel: +86-0411-84986291

^b Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, USA

^c Advanced Materials Research Institute, University of New Orleans, Louisiana 70148, USA

Abstract

TiO₂–SiO₂ hollow spheres with new hierarchical structures and magnetic response were prepared by etching mesoporous SiO₂/TiO₂/Fe₂O₃ hybrid particles in alkaline solution. Different from the conventional synthetic approaches to hollow particles which were always based on template methods, the shell layer of the SiO₂/TiO₂/Fe₂O₃ hybrid particles were solidified firstly by controlling the calcination temperature, which resulted in the removal of particle core and reservation of the shell layer during the etching process. The mechanism proposed was the dual porous structures in SiO₂/TiO₂/Fe₂O₃ spheres facilitated the diffusion of the alkaline solution into the particle interior and led to the destruction and removal of Si–O–Si bonds, and the residual Ti–O–Ti structures remained as TiO₂ nanofibers on the Ti–O–Si shell of the hollow spheres. Furthermore, encapsulation of Fe₂O₃ in the fibers induced the magnetic response of the hollow sphere. The hollow capsule with robust Ti–O–Si shell in the extreme pH solution made it applicable in many fields such as water treatment, bioseparation, microreactor and drug delivery systems. This work provided a new concept for the preparation of functional hollow spheres from its porous precursor. We believed that the present facile route was a significant breakthrough in the synthesis of hollow spheres and could be extended to the preparation of other hollow particles.

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Article information

DOI: https://doi.org/10.1039/C2JM31967E
Article type: Paper
Submitted: 29 Mar 2012
Accepted: 21 Jun 2012
First published: 25 Jun 2012

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J. Mater. Chem., 2012,22, 17476-17484

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Magnetic TiO₂–SiO₂ hybrid hollow spheres with TiO₂ nanofibers on the surface and their formation mechanism

X. Li, V. T. John, G. He, J. He and L. Spinu, J. Mater. Chem., 2012, 22, 17476 DOI: 10.1039/C2JM31967E

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Journal of Materials Chemistry