Strong plasmonic fluorescence enhancement of individual plant light-harvesting complexes

TL;DR

This study demonstrates a cost-effective method to significantly enhance the fluorescence of individual plant light-harvesting complexes using gold nanorods, revealing new insights into their fluorescence dynamics at the single-molecule level.

Contribution

It introduces a simple layer-by-layer technique to couple gold nanorods with light-harvesting complexes, achieving unprecedented fluorescence enhancement and lifetime reduction.

Findings

Up to 240-fold fluorescence brightness enhancement

109-fold decrease in fluorescence lifetime

Spectral overlap enables strong plasmonic coupling

Abstract

Plasmonic coupling of metallic nanoparticles and adjacent pigments can dramatically increase the brightness of the pigments due to the enhanced local electric field. Here, we demonstrate that the fluorescence brightness of a single plant light-harvesting complex (LHCII) can be significantly enhanced when coupled to single gold nanorods (AuNRs). The AuNRs utilized in this study were prepared via chemical reactions, and the hybrid system was constructed using a simple and economical spin-assisted layer-by-layer technique. Enhancement of fluorescence brightness of up to 240-fold was observed, accompanied by a 109-fold decrease in the average (amplitude-weighted) fluorescence lifetime from approximately 3.5 ns down to 32 ps, corresponding to an excitation enhancement of 63-fold and emission enhancement of up to 3.8-fold. This large enhancement is due to the strong spectral overlap of the longitudinal localized surface plasmon resonance of the utilized AuNRs and the absorption or emission bands of LHCII. This study provides an inexpensive strategy to explore the fluorescence dynamics of weakly emitting photosynthetic light-harvesting complexes at the single molecule level.