Template-free synthesis of TiO2 microcages in agarose gels with improved photocatalytic activity.

A template-free synthesis of TiO 2 microcages by using (NH 4) 2TiF 6 and NaOH as the reactants and the agarose gel as the reaction medium is developed. The resultant TiO 2 microcages possess a pseudo-cubic morphology with the edge size of 1–2 μm and the shell thickness around 48 nm. It is found that the shell of TiO 2 microcages consists of anatase TiO 2 nanoparticles about 15 nm in diameter, and possesses the mesopores about 3.8 nm in size. A proposed formation mechanism suggests that pseudo-cubic Na 5Ti 3F 14 microcages firstly generate in agarose gels due to the incomplete hydrolysis of TiF 62− and the inhibited diffusion effect of gels, and then transform into anatase TiO 2 without changing the morphology as the agarose gels are removed in hot water about 90 °C. These TiO 2 microcage samples exhibit higher photocatalytic activity than Degussa P25 for the degradation of methyl orange under artificial solar light irradiation, which can be attributed to their well-preserved hollow structure with mesopores. This study may devote a novel and facile approach for the template-free synthesis of hollow structure functional materials. [ABSTRACT FROM AUTHOR]