Synthesis and structural evolution of hollow flower-type mesoporous silica microspheres
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Synthesis and structural evolution of hollow flower-type mesoporous silica microspheres Shanshan Wang • Zhimin Chen • Hailian Zhang • Yuanlong Guo Bo Wang • Linmei Li • Guo Tian • Xing Wei • Dandan Zhu • Yinghua Li • Hongxia Yang • Qun Xu
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Received: 17 July 2012 / Accepted: 1 November 2012 / Published online: 27 November 2012 Ó Springer Science+Business Media New York 2012
Abstract Hollow flower-type mesoporous silica microspheres (designated as HFMSs) with tunable smaller pores and lager pores in the shell have been successfully synthesized via a structural difference-based selective etching treatment of solid silica core/mesoporous silica shell (sSiO2@mSiO2) microspheres. The structure of sSiO2@ mSiO2 microspheres could evolve to rattle-type, hollow structure, flower-type structure, and peanut-type structure from core/shell structure just by varying the etching agent from Na2CO3 solution to ammonia solution and adjusting the concentration of etching agent, respectively. Transmission electron microscopy, scanning electron microscopy, and nitrogen adsorption–desorption analysis are applied to characterize the synthesized samples. The mechanism of such a structural evolution is explained in this work.
Introduction Hollow spherical materials with porous shells are of great interest in many current and emerging areas of technology due to their unique properties, such as adjustable and welldefined pore structure, low density, large surface area, excellent loading capacity, high permeability, and extensive or potential applications in catalysis, sorption, separation, solar cells, optics, and biomedical fields [1–12]. As
S. Wang Z. Chen (&) H. Zhang Y. Guo B. Wang L. Li G. Tian X. Wei D. Zhu Y. Li H. Yang Q. Xu (&) College of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450052, China e-mail: [email protected] Q. Xu e-mail: [email protected]
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a special type of these materials, inorganic silica microspheres have attracted widespread attention because of their biocompatibility, low density, and high thermal and mechanical stability. A large number of synthetic strategies have been reported for the successful fabrication of hollow porous particles of silica [13–18], carbon [19–22], metallic oxide [23–25], such as conventional hard-template [26–32] and soft-template methods [33–40] as well as newly emerging methods based on sacrificial template [41–44] and template-free [9, 45–47] have been employed. Among these approaches, the hard-template routes are probably the most commonly used. They have dramatically expanded the range of hollow particles available for fabrication of hollow structures from templates of essentially any size, shape, and composition. For instance, based on polymer polystyrene colloidal templates, Caruso et al. first synthesized inorganic silica hollow capsules through layerby-layer (LBL) technique [27]. The assembly cycle can be repeated to form multilayer structure with well-defined wall thickness. Hyeon et al. prepared hollow microspheres of Pd by adsorpt
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