Light-Driven Fe ₃ O ₄ – <i>Azotobacter vinelandii</i> Biohybrids for Enhanced Nitrogen Fixation

Developing sustainable strategies for ambient ammonia synthesis is a critical challenge in materials science and catalysis. While bioinorganic hybrid systems have emerged as a promising solution by combining the light-harvesting efficiency of semiconductors with the catalytic specificity of biological nitrogenases, balancing material toxicity with electron transfer efficiency remains a major bottleneck. In this study, we constructed a robust and biocompatible inorganic-bacterial hybrid system via the in situ binding of magnetite (Fe 3 O 4 ) nanoparticles (NPs) to whole-cell microorganisms. In this architecture, Fe 3 O 4 NPs function as photosensitizers that capture solar energy to generate photoexcited electrons. These electrons are efficiently transferred to the attached Azotobacter vinelandii ( A. vinelandii ), thereby supplementing the intracellular electron pool. This continuous exogenous electron supply significantly boosts the energy conversion efficiency and nitrogenase activity within the biohybrid. This study underscores the potential of nanobiohybrid systems in solar-to-chemical energy conversion and paves the way for the sustainable production of diverse functional chemicals utilizing solar energy.