A simple and efficient route to prepare inorganic hollow microspheres using polymer particles as template in supercritical fluids

Using the excellent transport properties of supercritical carbon dioxide, tetraethyl orthosilicate (TEOS) could be easily carried into the template of the cross-linked polystyrene (PS) microspheres. Through the sol–gel procedure, the TEOS penetrated into the PS microspheres was transferred into silica. After sintering these composite particles, hollow silica microspheres were obtained. Through the above method, the hollow titanium dioxide microspheres also could be synthesized. The formation mechanism of the hollow particles was discussed and the morphology of the hollow microspheres was characterized by transmission electron microscopy (TEM) and scanning electronic microscope (SEM).