Prof. Ya-Hsuan Liou from NTU RCFE and Dr. Li Cheng Kao, postdoctoral researcher, discovered a simple way to synthesize heterogeneous crystals by synthesizing in a hierarchical structure with crystal defects. Their research was published in Journal of Material Chemistry A (IF=8.8) of Royal Society of Chemistry and selected as the cover article of Issue 23, 2018.
With the development of electron microscope and nanotechnology, researchers now can use microscopes to observe growth processes of crystals which have not been recorded in the past. In the study, Prof. Liou and Dr. Gao used the liquid phase growth method so the crystal can grow along a fixed direction. They successfully made TiO2 nanorod arrays with anatase/rutile crystal form on the substrate. When nanomaterials adhere and grow in a fixed direction, the difference in the planar structure of the lattice on two different planes may cause interface dislocations or defects, which will change the activity of the material.
The team overcame the difficulty in growing anatase TiO2. Through modifying liquid phase environment, the growth rate and crystal form of TiO2 also changed. Prof. Liou cooperated with the team led by Dr. Jinghua Guo from Advanced Light Source Lab, University of California, Santa Cruz. Synchrotron X-ray spectroscopy was used to confirm the physical and chemical properties of the nanomaterial, as well as the spatial distribution of different crystal forms. In addition, resonant inelastic X scattering was used to observe the defects resulting from directional attachment growth. The photocatalytic degradation of pollutants indicates that materials with heterogeneous crystal structures exhibit enhanced photocatalytic activity. TiO2 nanomaterial developed in this research has broad application prospects in the fields of energy and environment.