Anaerobic self-assembly of regenerable bacteria-quantum dots hybrid for solar hydrogen production

Inorganic-biological hybrid systems (bio-hybrid), comprising fermentative bacteria and inorganic semiconductor photosensitizers for synergistic utilization of solar energy and organic wastes, offer opportunities for sustainable fuel biosynthesis, but the low quantum efficiency, photosensitizer biotoxicity and inability for self-regeneration are remaining hurdles to overcome. Here, we unveiled a previously-neglected role of oxygen in suppressing the biosynthesis of cadmium selenide quantum dots (CdSe QDs) and the metabolic activities of Escherichia coli, and accordingly adopted a simple oxygenregulation strategy to enable self-assembly of bacterial-QDs hybrid for efficient solar hydrogen production. Shifting from aerobic to anaerobic biosynthesis significantly lowered the intracellular reactive oxygen species level and raise the NADPH and thiol-protein production, enabling two-order-of-magnitude higher bio-QDs synthesis rate and resulting in CdSe-rich products. The bacteria with abundant biocompatible intracellular bio-QDs naturally formed high-activity, self-regenerable bio-hybrid and achieved quantum efficiency of 28.7% for visible-light-driven photocatalytic hydrogen production, outperforming all the existing existing bio-hybrids. It also exhibited high stability during cyclic operation and robust performance for treating real wastewater under simulated sunlight. Our work provides valuable new insights into the metallic nanomaterial biosynthesis process to guide the design of self-assembled bio-hybrid towards sustainable energy and environmental applications.