Effect of seed particles on crystallization and crystallite size of anatase TiO2 nanocrystals by solvothermal treatment

• Seeds induced local crystallization and growth of anatase TiO2 from amorphous state.
• Preferential growth of anatase TiO2 occurred at vicinity of the crystalline seed.
• Above 120 °C, homogeneous nucleation and growth of anatase TiO2 crystals prevailed.

Commercial TiO2 nanoparticles (Degussa P25) with a mean diameter of ca. 20 nm and of predominately anatase phase were deliberately added in sol–gel-prepared amorphous TiO2 particles as “seed” before being subjected altogether to a mild solvothermal treatment over a temperature range from 100 to 200 °C. The presence of seed particles reduced the crystallization temperature moderately from 127.2 to 122.4 °C when the seed of up to 10 wt.% was added, resulted in crystalline anatase nanocrystals. On the other hand, crystallite size of the anatase nanocrystals increased up to an average of 28 nm (+40%) with the seed. This seed-induced grain growth appeared to occur preferentially at vicinity of the seed particles. As temperature was raised above the crystallization temperature (∼120 °C), homogeneous nucleation and growth of the anatase TiO2 nanocrystals prevailed so that a massive anatase structure with a crystal dimension of 8–12 nm resulted after the solvothermal treatment.

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