Plasmonic Field Enhancement of the Bacteriorhodopsin Photocurrent during Its Proton Pump Photocycle

Abstract

The proton pump photocycle of bacteriorhodopsin (bR) produces photocurrent on a microsecond time scale which is assigned to the deprotonation step forming the M(412) intermediate. The return of the M(412) intermediate to the bR ground state (bR(570)) has two pathways: (1) thermally via multiple intermediates (which takes 15 ms) or (2) by a more rapid and direct process by absorbing blue light (which takes hundreds of nanoseconds). By using nanoparticles (Ag, Ag-Au, and Au NPs) having different surface plasmon resonance extinction spectra, it is found that Ag NPs whose spectrum overlaps best with the M(412) absorption regions enhance the stationary photocurrent 15 times. This large enhancement is proposed to be due to the accelerated photoexcitation rate of the M(412) (in the presence of the plasmon field of the light in this region) as well as short-circuiting of the photocycle, increasing its duty cycles.

Bacteriorhodopsin‐Based Biophotovoltaic Devices Driven by Chemiluminescence as Endogenous Light Source

“…The maximum current density of 157.32 nA cm −2 was obtained by bR/OPV electrode with 20 × 10 −6 m of OPV, which was 3.2 times larger than that of bR electrode. And the current density was significantly higher than that reported in the literatures based on up‐conversion nanoparticles (5 nA cm −2 ) and Au nanoparticles (25 nA cm −2 ) . With further increasing OPV concentration (30 × 10 −6 m , 40 × 10 −6 m, and 50 × 10 −6 m ), the current density decreased slightly (151.20, 140.79, and 110.32 nA cm −2 ), which was consistent with the trend of CRET efficiency changes (Figure b).…”

“…Hence, in order to get consecutive photocycle and steady photocurrent, external light source with additional blue light is usually introduced. Up‐conversion nanoparticles with blue and green emissions, quantum dots that emitted 530 nm fluorescence under the illumination of 410 nm, and the surface plasmon resonance of Au nanoparticle that could enhance the intensity of blue light have been incorporated into bR‐based photoelectric devices to induce stationary photocurrent . At present, in the bR‐based photoelectric devices, the way to initiate bR photocycle is to directly use two monochromatic light with high intensity or to use laser light source that excites the fluorescent materials to emit fluorescence, which are high‐energy and limited to the external instruments .…”

Enhanced photocurrent generation in bacteriorhodopsin based bio-sensitized solar cells using gel electrolyte

“…In general organic based solvents are used as a solvent for dyes, while BR uses water as a solvent which provides an additional advantage of stability and eco friendly nature to the solar cells. In addition, BR functionally tolerates broad range of pH (5-11) [10][11][12][13][14][15]. The first BSSC made with TiO 2 / BR having triiodide electrolyte combination showed short circuit current (J sc ) maximum of 0.38 mA/cm 2 [16].…”

Photoconductive NSOM for mapping optoelectronic phases in nanostructures

“…A high resolution photocurrent microscopy technique based on the cathodoluminescence of quantum dots has been demonstrated [42]. Additionally, biomaterials like membrane proteins have also been studied using NSOM where illumination of light can give rise to local displacement currents [43][44][45][46][47][48][49][50][51][52]. The NSOM tip can also be utilized to illuminate a finite size of molecules in a monolayer or few-layer membrane protein film.…”