Facile preparation of magnetic gamma-Fe2O3/TiO2 Janus hollow bowls with efficient visible-light photocatalytic activities by asymmetric shrinkage

In this paper, on the basis of a simple side-by-side co-electrospray procedure with a subsequent non-equilibrium calcination process, we have for the first time developed an asymmetric shrinkage approach for the fabrication of magnetic gamma-Fe2O3/TiO2 Janus hollow bowls (JHBs) by constructing a precursor solution pair with different gelation rates during the solvents evaporation process. The formation mechanisms of the bowl-shapes as well as the hollow interiors are proposed and confirmed. The as-obtained gamma-Fe2O3/TiO2 JHBs have a transition layer of Fe3+-doped-TiO2 between the gamma-Fe2O3 and TiO2 phases, and show an efficient visible-light photocatalytic activity and convenient magnetic separation for water purification because of the unique structure and morphology as well as the fine magnetic properties. Moreover, the method reported here can be readily extended to the fabrication of other bi-, tri- and multi-component metal oxides hollow particles with asymmetric shapes. Due to the interesting bowl-shaped hollow nanostructure, the as-prepared gamma-Fe2O3/TiO2 JHBs are expected to have a number of applications that involve drug delivery, micro-/nano-motors, microcontainers, microreactors, sensors, and so forth.