Interactions of Photosystem I with Plasmonic nanostructures

The plasmonic interaction effects of various nanostructures on the fluorescence properties of photosystem I as found by single-molecule spectroscopy are summarized. The used nanostructures are spherical Au nanoparticles, silver island films as well as hexagonal arrays of nanometer-sized Au- and Ag-triangles (the Fischer patterns). The fluorescence emission of photosystem I is intensified due to coupling with these nanostructures. For single photosystem I complexes, enhancement factors of up to 37 were observed. The average enhancements vary between 2.2 for Au Fischer pattern and 9 for spherical Au nanoparticles. The enhancement of the fluorescence of photosystem I demonstrates in all cases a strong wavelength dependence. This wavelength dependence can be explained by the spatially largely extended multichromophore composition of photosystem I complexes. From the viewpoint of the usability of these nanostructures for spectroscopic signal enhancement, the Fischer patterns are beneficial, due to their very low autoluminescence.