Controllable Synthesis of Inverse Opal TiO2-x Photonic Crystals and Their Photoelectric Properties.

In this study, inverse opal TiO2-x photonic crystals (IO-TiO2-x ) have been successfully synthesized by a two-step calcination. The whole synthesis is safe and feasible. Additionly, the reduction degree and the structure of IO-TiO2-x can be precisely controlled. A series of IO-TiO2-x samples with different reduction degree were prepared and characterized. The TEM images show that the obtained samples possess a 3D-ordered macroporous inverse opal structure. The reduced Ti atoms/oxygen vacancies were confirmed by Raman and XPS spectroscopy. All IO-TiO2-x samples showed better photoelectric properties than those of common TiO2 which indicates their great potential to be applied to photoelectric fields. The improvement of photoelectric properties is attributed to the efficient electron-hole separation efficiency induced by moderately reduced Ti atoms/oxygen vacancies. Meanwhile, the 3D-ordered macroporous inverse opal structure and the band gap are regulated to "capture" more solar energy. This new approach is proven to be a meaningful method to synthesize high-performance TiO2 materials.