Liquid Metal Amplified Charge Separation in Photocatalytic Micro/Nanomotors for Antibacterial Therapy

Abstract

Photocatalytic micro/nanomotors (MNMs) driven by electrophoresis have attracted considerable attention by virtue of their active mobility and versatile functionality. However, the rapid recombination of photogenerated electron-hole pairs on light illumination severely compromises the involvement of charge species in the catalytic redox reactions of fuels, thus hindering both the propulsion and the application performance of photocatalytic MNMs. Herein, we report a facile strategy to amplify charge separation by incorporating liquid metal (LM) into the construction of photocatalytic MNMs, thereby strengthening the electrophoretic propulsion of MNMs and promoting the generation of reactive oxygen species (ROS) for antibacterial application. The MNMs are constructed with a gallium (Ga) LM core, coated with abundant graphite-phase carbon nitride (g-C₃N₄) nanosheets and half covered by a thin platinum layer. These MNMs exhibit self-propulsion in hydrogen peroxide (H₂O₂) solution, with their motion dynamics further enhanced by light irradiation. Theoretical calculations and simulations reveal that the composition between Ga and g-C₃N₄ forms an ohmic junction in the electronic energy band structure, which effectively improves the charge separation efficiency of electron-hole pairs. These results align well with the experimental electrochemical tests and consequently intensify the catalytic redox reactions of H₂O₂, as well as accelerate the charge migration across MNMs, contributing to the enhancement of their propulsion performance. Simultaneously, the amplified separation of electrons facilitates increased ROS generation, empowering the MNMs with motion-enhanced antibacterial activity against <i>Escherichia coli</i>. Finally, an in vivo wound healing experiment is conducted, verifying the superior antibacterial therapeutic performance of photocatalytic MNMs. This work not only provides insights into the role of charge species in phoretic motion of MNMs but also gives inspiration for developing photocatalytic MNMs with advanced biomedical applications.