Metal-Enhanced Fluorescence of Chlorophylls in Single Light-Harvesting Complexes

• Published in: Nano letters 2008-02, Vol.8 (2), p.558-564
• Main Authors: Mackowski, Sebastian, Wörmke, Stephan, Maier, Andreas J, Brotosudarmo, Tatas H. P, Harutyunyan, Hayk, Hartschuh, Achim, Govorov, Alexander O, Scheer, Hugo, Bräuchle, Christoph
• Format: Article
• Language: English
• Subjects: Chlorophyll - chemistry; Collective excitations (including excitons, polarons, plasmons and other charge-density excitations); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Light-Harvesting Protein Complexes - chemistry; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Materials Testing; Metals - chemistry; Nanostructures - chemistry; Nanostructures - ultrastructure; Nanotechnology - methods; Particle Size; Physics; Spectrometry, Fluorescence - methods; Surface and interface electron states; Surface Plasmon Resonance - methods; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/nl072854o

Ensemble and single-molecule spectroscopy demonstrates that both emission and absorption of peridinin−chlorophyll−protein photosynthetic antennae can be largely enhanced through plasmonic interactions. We find up to 18-fold increase of the chlorophyll fluorescence for complexes placed near a silver metal layer. This enhancement, which leaves no measurable effects on the protein structure, is observed when exciting either chlorophyll or carotenoid and is attributed predominantly to an increase of the excitation rate in the antenna. The enhancement mechanism comes from plasmon-induced amplification of electromagnetic fields inside the complex. This result is an important step toward applying plasmonic nanostructures for controlling the optical response of complex biomolecules and improving the design and functioning of artificial light-harvesting systems.