Abstract: Flower-like titania nanocrystals were synthesized by hydrolysis of titanium (IV) chloride at a low temperature of 70℃ in 4–6 h, employing nanocrystal cellulose (NCC) as a morphology controlling agent. The obtained nanocrystals were characterized by transmission electron microscope (TEM), high-resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and FTIR. TEM and HRTEM investigations reveal that the morphologies of the nancrystals are flower-like, and each flower is composed of several nanoneedles with a diameter of 15–20 nm and a length of 100–200 nm. The XRD results show that the crystalline phase of the nanocrystals have a strong dependence on the mole ratio of TiCl₄ to H₂O and the reaction time. FTIR result shows that a chemical bond is formed between NCC and TiO₂. A possible growth mechanism is proposed based on the characteristic results. The NCC whose surface is full of hydrophilic groups can establish hydrogen bonding with TiO₂ to promote the nucleation and crystal growth of TiO₂ at low temperature. Moreover, the selective adsorption of NCC molecules on the crystal face of TiO₂ varies the growth rate of different crystal planes, and the anisotropic crystal growth leads to the formation of nanoneedles. Then these nanoneedles aggregate together to assemble into a flower-like secondary structure. TiO₂ prepared at low temperature exhibites high activity in the photocatalytic degradation of methyl orange in aqueous solution under metal halide lamp.

Key words: nanocrystal cellulose (NCC), titania, flower-like, titanium chloride