Ultrasmall Day–Night Photocatalysts of LnYVO4:Eu3+ (Ln = Nd, Tm, and Er) Nanoparticles

Day–night photocatalysts that can persistently generate reactive oxygen species (ROS) after ceasing light attracted intensive attention in diverse fields. However, current strategies of combining a photocatalyst and an energy storage material can hardly fulfill the demands, especially in size. We herein present a one-phase sub-5 nm day–night photocatalyst via simply doping Nd, Tm, or Er into YVO4:Eu3+ nanoparticles, efficiently producing ROS in both day and night modes. We demonstrate that the rare earth ions acted as a ROS generator, and Eu3+ and defects contributed to the long persistency. Furthermore, the ultrasmall size led to remarkable bacterial uptake and bactericidal efficacy. Our finding suggests an alternative mechanism of day–night photocatalysts that could be ultrasmall and thus may shed light on disinfection and other applications.