Template-directed synthesis of hollow silica beads by an interfacial sol–gel route

• The hollow silica beads were prepared by a template-directed sol–gel process.
• The templates were prepared by coating proteins on the surface of agarose beads.
• The shell/core template was possessed of low solid content and dense protein shell.
• The hollow silica beads were featured by tuned shell thickness and large bead size.
• The shell thickness of hollow beads was related upon the silica precursor amounts.

Hollow silica beads with controllable shell thickness are successfully fabricated by means of an improved template-directed interfacial sol–gel polymerization. Templates made by the proteins-entrapped agarose beads with strong functionalities such as preventing collapse and unwanted permeation from shells allow us to construct desired hollow beads. Our investigations show that the resulting beads are nearly uniform with an average cavity size of 210 µm. The beads are with less shrinkage and good surface roughness when the cores are completely removed. Shell thickness can be tuned from 1 to 9 µm by simply altering the volume ratio of silica precursors to solvent from 0.02 to 0.15. The mechanical stability increases with shell thickness under compression tests. The pore size of amorphous shells is about 5 nm and the specific surface area is about 315 m2 g−1, which is ready for some specific applications. Besides the importance of material selections we stressed in this work, it is worth to note that our fabrication can be in a batch mode and thus might open a way to synthesize other inorganic hollow beads, which already found applications in the inertial confinement fusion experiments etc., to overcome some mass production issues.

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