Hybrid structures of colloidal quantum dots and nitrogen-fixing bacteria for synthesis of ammonia

Abstract

Colloidal quantum dots (QDs) are semiconductor nanoparticles having a characteristic that the bandgap structure of the QD varies depending on the size of the particle. The QDs can absorb and emit light of different wavelengths based on the bandgap size. In this study, we investigated the characteristics of QDs that generate electrons and holes when exposed to light. We utilized the induced electrons to facilitate chemical reactions, focusing particularly on the production of ammonia. Azotobacter vinelandii (A. vinelandii) is a dinitrogen-fixing bacterium capable of fixing nitrogen in the atmosphere and producing ammonia during aerobic growth. However, these nitrogen-fixing bacteria exhibit low ammonia conversion efficiency for industrial ammonia production. Therefore, we propose a hybrid system combining colloidal QDs and A. vinelandii to enhance the ammonia productivity of the bacterium. In this study, indium phosphide (InP) based QDs were employed to develop a hybrid system suitable for biological applications. Through this research, we anticipate the environmentally friendly production of ammonia under milder temperature and pressure conditions compared to the existing Haber-Bosch process, utilizing the nitrogen-fixing bacteria and QDs in a hybrid structure.