One-pot synthesis of nano titanium dioxide in supercritical water

Supercritical hydrothermal synthesis of nanosized metal oxides is of great interest for scholars due to its one-pot and readily realizing commercial production process. Hydrothermal synthesis of nanosized TiO2 in subcritical and supercritical water was investigated with different reaction temperatures (250-450°C), time (3-10 min), precursor species (Ti(SO4)2, TiCl4), and the addition of a surfactant (CH3(CH2)5NH2). TiO2 synthesized under supercritical state has a higher degree of crystallinity when compared with TiO2 obtained from subcritical state, which is attributed to a higher reaction rate. Extending reaction time from 3 to 10 min leads to the growth of crystal and broader size distribution (36.66 ± 8.5 nm). More uniform products can be obtained when Ti(SO4)2 acting as the precursor compared with TiCl4 being the precursor. The application of surfactant CH3(CH2)5NH2 in the synthesis makes chemical bonding between the particle surface and organic ligand. It affects the growth direction of TiO2 crystal; as a result, rod-like TiO2 crystal is obtained.