Programming surface morphology of TiO2 hollow spheres and their superhydrophilic films

Long-term stable superhydrophilic films without UV irradiation consisting of hierarchical raspberrylike metal-ion-doped TiO(2) hollow spheres were fabricated by a simple spinning-coat method. The hierarchical surface morphology of metal-ion-doped TiO(2) hollow spheres can be programmed from "smooth", "moderate roughness" to "roughness" by adjusting the molar ratio of Co(2+) ions to Zn(2+) ions. Our results show that the substitution Co(2+) and Zn(2+) for Ti(4+) has effect on the phase transformation from anatase to rutile and further lead to different papillas on the surface of hollow nanospheres. And their films consisting of corresponding hollow nanospheres can be controlled from hydrophilic to superhydrophilic: 28, 7, and 0°. Therefore, our works open an avenue to design hierarchical surface morphology of nanospheres and further fabricate antifogging superhydrophilic films.