Ionic liquids for the controllable preparation of functional TiO2 nanostructures: a review

Ionic liquids (ILs), as an innovative class of structure-directing agents, make them promising materials for composites in materials science. Particularly, the integration of ILs with TiO 2 -based photocatalysts opens up a new dimension in simplifying synthetic methods and improving TiO 2 functions. This review summarizes recent progresses of IL-assisted strategies for the fabrication of functional TiO 2 -based photocatalysts with a special emphasis on the facilitation in the IL-assisted synthesis techniques including sol-gel reaction, hydrothermal/solvothermal process, and microwave method, as well as the enhancement in photocatalytic applications. Multiple roles that ILs played in the synthesis and photocatalysis (soft-template, crystallization promotion, microwave absorber, doping source, surface complex, etc.) have been classified and discussed in detail. In comparison with traditional methods, the advantages and shortages, as well as the future perspectives of ILs, are also proposed. It is believed that with the continuous exploration and development, new generation ILs will surely benefit materials science community.