Heterogeneous bacteriorhodopsin/gold nanoparticle stacks as a photovoltaic system

To mimic the stack structure of granum, for the first time we demonstrate bacteriorhodopsin (bR)/gold nanoparticles (AuNPs) heterogeneous multilayers to perform as a novel photovoltaic stack system with improved photoelectric performance. Upon a cooperative control of the diameter of AuNPs and the stacking layers, the photocurrent can be effectively regulated to reach about 350nAcm^-2. The possible mechanism for enhanced photocurrent recorded in our system is revealed by analyzing the flash kinetics of photocycle intermediates M₄₁₂, O₆₄₀, and J₆₀₀ of bR layers, which are accelerated under proper AuNPs in this stacking structure. A bypass photocycle model of bR photocycle from M₄₁₂ to B₅₇₀ state is proposed and supported by tested accumulation of M₄₁₂ and O₆₄₀ intermediate during the bR photocycle process. Interestingly, with this stack system, the input flickering light can be effectively modulated into regular photoelectric signals that are well controlled under different flickering frequency and proton concentration gradient. Based on above results, this system potentially serves as solar energy converter to power nano-devices.