Self-electrophoresis-propelled and self-built electric field-enhanced photocatalytic nanomotors for round-the-clock environmental remediation

Abstract

Photocatalytic degradation of water pollutants and pathogenic microorganisms works only under sunlight illumination. Herein, Janus nanomotors (NMs) integrate “round-the-clock” self-electrophoretic motion and self-built electric field-enhanced photocatalytic degradation of estradiol and E. coli for environmental remediation. ZnGa₂O₄:Cr³⁺ (ZGC) nanodots are deposited on silica-coated Fe₃O₄ nanoparticles (NPs), and Janus IO/Si@ZGC-Au NMs are constructed by sputter-coating with Au caps on one side, while mannose is grafted on the Au layer to obtain IO/Si@ZGC-Au-Man. Au layers effectively suppress electron–hole re-combination to improve the photocatalytic production of reactive oxygen species (ROS), and the generation of self-built electric field produces self-electrophoretic force to drive NM locomotion. In addition, the excited electrons are stored in the defects of ZGC and then slowly released and transferred to the Au cap, generating persistent self-electrophoretic force and degradation capability in the dark. Mannose-modified IO/Si@ZGC-Au-Man NMs increase bacterial capture in the dark and then promote bactericidal efficacy by photocatalytic ROS generation upon reillumination. The magnetic cores make it easier to recycle NMs and remove dead bacteria, and the recovered NMs retain the capabilities of active motion and photocatalytic efficacy. Thus, the self-built electric field and long afterglow of IO/Si@ZGC-Au Janus NMs achieve fuel-free light-powered motion and “round-the-clock” ROS generation for environmental remediation.