Optical Hot Spot Generation by the Plasmonic Coupling of Au Nanoparticles in the Nanospaces of Mesoporous Titanium(IV) Oxide

Controllable Microemulsion Synthesis of Hybrid TiO2-SiO2 Hollow Spheres and Au-Doped Hollow Spheres with Enhanced Photocatalytic Activity

Hollow structures in TiO₂ materials can enhance the photocatalytic properties by reducing the diffusion length and improving the accessibility of active sites for the reactants. However, existing approaches for preparing hollow TiO₂ materials have two drawbacks that restrict their engineering applicability: first, a heavy reliance on templates to form a hollow structure, which makes the preparation laborious, complicated, and costly; second, difficult-to-achieve high crystallization while maintaining the small grain size in calcinated TiO₂, which is crucial for enhancing photocatalytic activity. Herein, a simple, effective method is proposed that not only enables the preparation of hybrid TiO₂-SiO₂ hollow spheres without the template fabrication and removal process via microemulsion technology but also achieves both high crystallization and a small grain size in calcinated TiO₂ at once through the calcination of amorphous TiO₂ with organosilane at a high temperature of 850 °C. The prepared TiO₂-SiO₂ hollow spheres with tunable sizes demonstrate high photocatalytic activity with a maximum k value of 133.74 × 10^-3 min^-1, which is superior to commercial photocatalyst P25 (k = 114.97 × 10^-3 min^-1). In addition, Au can be doped in the hybrid TiO₂-SiO₂ shell to gain Au-doped hollow spheres that show a high k value of up to 694.14 × 10^-3 min^-1, which is 6 times larger than that of P25 and much better than that reported in the literature. This study not only provides an effective approach to stabilize and tune the grain growth of the TiO₂ photocatalyst during calcination but also enables the simple preparation of hollow TiO₂-based materials with controllable hollow nanostructures.