Precisely controlled heterogeneous nucleation sites for TiO2 crystal growth

Abstract

The development of new methods which enable exquisite control over crystal size over a wide range is highly desired for optimizing their performance. In this work, we employed anatase TiO₂ as an example to demonstrate a heterogeneous nucleation approach by coupling the slow hydrolysis of a titanium precursor and a dispersible silica substrate. After tight control of the number of nucleation sites, the crystal size is greatly dependent on the number of seeds. An in-depth nucleation analysis was carried out that showed that the reaction product, hydrofluoric acid (HF), plays a key role in selective etching of the substrate and further leads to crystal–substrate separation. Additionally, our preliminary results illustrated that the growth of Fe₂O₃ crystals can also be tuned by such a method without shape and composition variation. To the best of our knowledge, this is the first report of fine-tuning the crystal size of anatase TiO₂ by a heterogeneous nucleation method, and this provides a promising way to design and synthesize new materials with appropriate size and shape.