(140g) Tuning Photocurrent Responses from Photosystem I Interfaced with Tailored Plasmonic Gold and Silver Nanopatterns

Photosystem I (PSI), a photosynthetic membrane protein, undergoes light-activated charge separation and unidirectional electron transfer with near-unity quantum efficiency. The robust photo-electrochemical (PEC) activities of PSI makes it an ideal candidate for bio-hybrid optoelectronic devices. But, the first step toward the fabrication of such devices requires its successful integration with suitable biotic-abiotic interfaces for the rational design of PSI-based PEC electrode assemblies. Herein, we present our fundamental investigations into tuning the optoelectronic properties of multi-chromophore PSI complexes by interfacing them with plasmonic noble metal nanopatterns tailored for specific plasmonic absorption wavelengths and hence, resonance modes. Our hypothesis is that PSI assembly with tailored plasmonic nanopatterns can provide a rational strategy to enhance the light harvesting properties and photon-to-electrochemical energy conversions in PSI thin films via electric field coupling with the localized surface plasmon resonance (LSPR) effects of the nanostructures. Such efforts can overcome the inherent limitations of low light absorption and poor quantum efficiencies in conventional PSI thin-film assemblies on inorganic substrates. Our earlier works had reported the first-ever experimental observation of plasmon-induced photocurrent enhancements from PSI immobilized on Fischer patterns of Ag-nanopyramids (Ag-NPs) whose plasmonic resonant peaks were tuned to the PSI absorption peaks at ~450 and ~680 nm.¹ Our recent investigations have extended these studies for spatially localized and spectrally resolved plasmon-enhanced photocurrents from PSIs assembled around highly ordered Au and Ag nano-discs (NDs) whose dipolar plasmon resonance modes are tuned to the wavelengths of ~680 nm and ~560 nm, respectively.² Specifically, our results indicate ~6.8 and ~17.5-fold enhancements in PSI photocurrents under the excitation wavelengths of ~680 and ~565 nm respectively, as compared to PSI assembled on planar ITO substrates. We also report the spectrally-resolved specificity of PSI-plasmon interactions via action spectra for photocurrent enhancements recorded over wavelength ranges of 395–810 nm using nine discrete LED light sources; while, spatially resolved photocurrent enhancements are estimated from FDTD simulations on Au and Ag ND patterns. The significant findings from these investigations include: 1) direct correlations between wavelength-dependent photocurrent enhancements from PSI assemblies and the plasmonic resonance modes for the respective nanopatterned substrates, and 2) broadband photocurrent enhancements from plasmon-coupled photo-activations of the otherwise blind chlorophyll regions of the native PSI absorption spectra.

References:

1. Pamu R, Sandireddy VP, Kalyanaraman R, Khomami B, Mukherjee D. Plasmon-Enhanced Photocurrent from Photosystem I Assembled on Ag Nanopyramids. The Journal of Physical Chemistry Letters. 2018; 9(5):970-977.
2. Pamu R, Lawrie BJ, Khomami B, Mukherjee D. Broadband Plasmonic Photocurrent Enhancement from Photosystem I Assembled with Tailored Arrays of Au and Ag Nanodisks. ACS Applied Nano Materials. 2021.