LAUSR

Abstract The demand for disposable power sources has propelled the development of cyanobacterial biophotovoltaics to effectively and self-sustainably generate biophotoelectricity. However, garnering electricity from cyanobacteria remains challenging because of the low efficiency of cyanobacterial electron harvesting and extracellular electron transfer. In this work, we propose biocompatible and highly stable gold nanoparticles intracellularly biosynthesized within the cyanobacteria as an effective light-absorber to increase photo-excited electrons and as an electrical conduit to improve the electron transfer through the cell membrane. The nanoparticles were synthesized internally and directly on the surface of Synechocystis sp. PCC 6803, through bioelectrochemical reduction of the metal ions. The cyanobacterial biophotovoltaics with the intracellular gold nanoparticles enhanced the maximum power density by as much as 33.6 times compared with the device without the nanoparticles. Even after the long cultivation (~120 h), only a few dead cells (