Sonochemical synthesis of CeO₂ nanoparticles with high photocatalytic and antibacterial activities under visible light

Cerium oxide (CeO 2 ), one of the most significant heterogeneous catalysts, has attracted extensive research interest. Herein, ultrafine spherical CeO 2 with a diameter of 5 nm is successfully synthesized within a reaction time of 25 min by a simple and environmentally friendly sonochemical method without any additional oxidants or high temperature and pressure conditions, and 50 nm spherical CeO 2 was obtained by heat treating the 5 nm spherical CeO 2 in 400°C air atmosphere condition for 3 h. By controlling the ultrasonic condition, a specific surface area of up to 194.2 m 2 /g and a bandgap as low as 2.2 eV are achieved in the CeO 2 nanoparticles without any heat treatment. Further study has shown that the as‐prepared spherical CeO 2 without heat treatment exhibits remarkable photocatalytic and antibacterial activities under visible light conditions. The study is beneficial for energy conservation in fabricating ultrafine photocatalytic and antibacterial nanomaterials.