Synthesis of uniform hollow TiO2 and SiO2 microspheres via a freezing assisted reverse microemulsion-templated sol–gel method

•TiO2 and SiO2 hollow microspheres were fabricated by a freezing assisted method.•Thickness of SiO2 hollow microspheres can be adjusted by changing hydrolysis time.•Freezing-assisted process possesses the advantages of hard and soft templating.

Uniform titania and silica hollow microspheres of 300–500 nm diameter with controlled wall thickness have been successfully synthesized using monodispersed micro-ice as the template generated by freezing water droplets in a reverse microemulsion at −40 °C and −80 °C and subsequent sol–gel reactions on the surface of the formed micro-ice. Furthermore, the growth mechanism of the hollow spheres by this facile and interesting technique was discussed in detail.

Graphical abstractUniform titania and silica hollow microspheres of 300–500 nm diameter have been successfully synthesized using monodisperse micro-ice as the template generated by freezing water droplets in a reverse microemulsion at −40 °C and −80 °C after sol–gel polymerization process. Moreover, wall thickness of hollow SiO2 microspheres has been controlled from 10 to 100 nm.Figure optionsDownload full-size imageDownload as PowerPoint slide