Plasmonic interactions of photosystem I with Fischer patterns made of Gold and Silver

Single-molecule spectroscopy has been used to investigate the plasmonic interaction effects of nanometer-sized hexagonal arrays of Au- and Ag-triangles on the fluorescence properties of photosystem I (PSI) - a key component of the photosynthetic apparatus. The fluorescence emission of PSI is intensified upon coupling with these nanostructures. For single PSI trimers, enhancement factors of up to 10.5 (Au) and 15 (Ag) were observed. The average enhancement is 2.2/5.7 for Au/Ag, respectively. Comparison of the emission spectra shows that the enhancement depends on the wavelength. This wavelength dependence can be explained by the multichromophore composition of PSI. Furthermore, plasmonic interaction increases the fluorescence emission of spectral components, which are barely visible under natural conditions. The metal nanostructures produced via nanosphere lithography turned out to be beneficial tools for signal enhancement due to the very low intensity of their autoluminescence signal. (C) 2012 Elsevier B. V. All rights reserved.