Plasmon-Enhanced Photocurrent of Photosynthetic Pigment Proteins on Nanoporous Silver

In a quest to fabricate novel solar energy materials, the high quantum efficiency and long charge separated states of photosynthetic pigment-proteins are being exploited through their direct incorporation in bioelectronic devices. In this work, a biohybrid photocathode comprised of bacterial reaction center-light harvesting 1 (RC-LH1) complexes self-assembled on a nanostructured silver substrate yields a peak photocurrent of 166 A cm(-2) under 1 sun illumination, and a maximum of 416 A cm(-2) under 4 suns, the highest reported to date on a bare metal electrode. A 2.5-fold plasmonic enhancement of light absorption per RC-LH1 complex is observed on the rough silver substrate. This plasmonic interaction is assessed using confocal fluorescence microscopy, revealing an increase of fluorescence yield, and radiative rate of the RC-LH1 complexes, signatures of plasmon-enhanced fluorescence. Nanostructuring of the silver substrate also enhanced the stability of the protein under continuous illumination by almost an order of magnitude relative to a nonstructured bulk silver control. Due to its ease of construction, increased protein loading capacity, stability, and more efficient use of light, this hybrid material is an excellent candidate for further development of plasmon-enhanced biosensors and biophotovoltaic devices.