title: Tailoring plasmonic and electrostatic field effects to maximize solar energy conversion by bacteriorhodopsin, the other natural photosynthetic system.
abstract: We have explored the plasmonic field enhancement of current production from bacteriorhodopsin (bR) by maximizing the blue light effect, where the influx of blue photons absorbed by the long-lived M intermediate drastically shortens the time scale of the bR photocycle, leading to current enhancement. To this end, we used three approaches in our solution-based cell: (1) We improved the charge carrier separation in solution through the use of a proton-selective Nafion membrane. (2) We maximized the plasmonic surface field effects by selecting the capping polymer with minimum surface field screening and best nanoparticle stability. (3) We selected the plasmonic nanoparticle with the strongest plasmonic field whose surface plasmon resonance has the largest spectral overlap with the blue light absorbing M-intermediate. Theoretical models are used to explain experimental results, which show a 40 nm cuboidal nanoparticle capped with 55k PVP polymer to give the best photocurrent enhancement. Enhanced by this particle, bR in our Nafion membrane solution cell gave a photocurrent of 0.21 μA/cm(3), which is 5000 times larger than the published results for thin film bR electrochemical cells even with an applied bias. Additional possible enhancements are proposed.
authors.affiliation: Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States.
authors.forename: Chun-Wan
authors.initials: CW
authors.lastname: Yen
authors.forename: Steven C
authors.initials: SC
authors.lastname: Hayden
authors.forename: Erik C
authors.initials: EC
authors.lastname: Dreaden
authors.forename: Paul
authors.initials: P
authors.lastname: Szymanski
authors.forename: Mostafa A
authors.initials: MA
authors.lastname: El-Sayed
mesh_terms: D001436:Bacteriorhodopsins / Q000737:chemistry*; D007477:Ions; D008027:Light; D053758:Nanoparticles / Q000737:chemistry; D036103:Nanotechnology / Q000379:methods*; D010777:Photochemistry / Q000379:methods; D017785:Photons; D010788:Photosynthesis; D012993:Solar Energy; D055672:Static Electricity; D020349:Surface Plasmon Resonance
chemical_list: D007477:Ions; D001436:Bacteriorhodopsins