Monodisperse rutile TiO2 nanorod-based microspheres with various diameters: hydrothermal synthesis, formation mechanism and diameter- and crystallinity-dependent photocatalytic properties

Monodisperse microspheres constructed with rutile TiO2 nanorods were synthesized by a hydrothermal reaction of TiCl3 with Na2C2O4, ethylene glycol (EG) and H2O at 140–220°C for 4–12 h. The diameter of the microspheres can be changed in the range of 190–1200 nm by tuning the reaction temperature and time. The constituent nanorods grow along the c-axis of rutile, the side facets of which are (110), ( $\overline{1}10),(1\overline{1}0)$ , and ( $\overline{1}\overline{1}0)$ . The formation of the rod-like structure results from the selective adsorption of $\mathrm{C}₂\mathrm{O}₄^2-$ ions on {110} prismatic faces of rutile TiO2 nanorods. The hydrogen bonding formed between rutile TiO2 nanorods adsorbing EG drives the formation of the nanorod-based spherical nanoarchitectures. The photocatalytic ability of the as-prapared the anatase-rutile composite TiO2 nanorod-based nanospheres with a diameter of about 190 nm is stronger than that of rutile TiO2 nanorod-based nanospheres with diameters of 500 and 1000 nm.