Synthesis of hierarchical hollow silica microspheres containing surface nanoparticles employing the quasi-hard template of poly(4-vinylpyridine) microspheres.
ABSTRACT A facile method of preparing hierarchical hollow silica microspheres containing surface silica nanoparticles (HHSMs) through the sol-gel process of tetraethylorthosilicate employing a quasi-hard template of non-cross-linking poly(4-vinylpyridine) microspheres is proposed. The quasi-hard template contains the inherent catalyst of the basic pyridine group, and a few of the polymer chains can escape from the template matrix into the aqueous phase, which initiates the sol-gel process spontaneously both on the surface of the template used to prepare the hollow silica shell and in the aqueous phase to produce the surface silica nanoparticles. By tuning the weight ratio of the silica precursor to the quasi-hard template, HHSMs with a size of about 180 nm and a shell thickness ranging from 14 to 32 nm and surface silica nanoparticles ranging from 17 to 36 nm are produced initially through the deposition of surface silica nanoparticles onto the silica shell, followed by template removal either by calcination or solvent extraction. The synthesized HHSMs are characterized, and a possible mechanism for the synthesis of HHSMs is proposed.
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ABSTRACT: Rigid, porous objects and surfactants serve as powerful templates for the formation of mesoporous and macroporous materials. When both types of template are combined in a single synthesis, materials with intricate architectures and hierarchical porosity can be obtained. In this tutorial review, we explain how to conduct syntheses with both soft and hard templates; moreover, we describe methods to control the final structure present in the templated material. Much of the foundation for multiple templating lies in the study of materials made with only one type of template. To establish a foundation in this area, a description of hard and soft templating is given, delving into the templates available and the steps required for effective templating. This leads into an extended discussion about materials templated with both hard and soft templates. Through the use of recent examples in the literature, we aim to show the diversity of structures possible through multiple templating and the advantages these structures can provide for a wide range of applications. An emphasis is placed on how various factors-such as the type of template, type of precursor, heat-treatment temperature, confinement within a small space, and template-template interactions-impact morphology.Chemical Society Reviews 10/2012; · 24.89 Impact Factor