Biohybrid magnetic microrobots for enhanced photocatalytic RhB degradation and E.coli inactivation under visible light irradiation

Scheme 1. Schematic illustration of the composite structure, enhanced visible light response, magnetic propulsion, recollection of CFB microrobots and their photocatalytic removement towards RhB and E.coli . • Chlorella@Fe 3 O 4 @BiOCl magnetic microrobots were fabricated by a biotemplated method. • An enhanced photocatalytic ability was achieved compared to BiOCl. • Visible light utilization was improved by photosynthesis pigments in Chlorella Cells. • Higher photocatalytic rates were obtained with magnetic actuation. Wastewater remediation has become an urgent task, to solve this problem, various photocatalysts towards harmful organic pollutants and pathogenic microorganisms have been developed. However, it is still challenging to exploit mass-produced microrobotic platforms with high photocatalytic efficiency, flexible manipulation, and recycling capability. Herein, we proposed a novel ternary biohybrid photocatalytic microrobot based on Chlorella ( Ch. ) cells. Fe 3 O 4 nanoparticles (NPs) and BiOCl nanosheets (NSs) were deposited on the biotemplates in sequence to form the Ch. @Fe 3 O 4 @BiOCl (CFB) microrobots. The as-prepared microrobots could be stimulated to degrade Rhodamine B (RhB) and inactivate E.coli cells under visible light irradiation, with a higher photocatalytic rate compared with BiOCl. Further, they could be propelled precisely with high velocities by magnetic fields, resulting in significant enhanced photocatalytic efficiency as well as magnetic recycling capability. The k -value (0.2 min −1 ) could be improved 3.1 times than static state (0.064 min −1 ) and the inactivation rate could achieve 99.37% within 10 min with swarming rolling microrobots. Such excellent photocatalytic performance can be ascribed to the composite microstructure, the abundant natural photosensitizers in biotemplates, and also the enhanced fluidic interaction under magnetic actuation. These intriguing properties enable the microrobots to be a promising and efficient platform for dye degradation and bacterial inactivation.