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Plasmon excitations in metallic nanoparticles are effective means for controlling the optical properties of light-harvesting complexes [1-6]. Recent work has demonstrated that the emission of light-harvesting complex, peridinin-chlorophyll-protein can be enhanced by coupling to inhomogeneous distribution of silver islands [1,2], while fluorescence and absorption of Photosystems can increase by attaching gold nanoparticles [3,4].
Precise engineering of the light harvesting process requires careful design of the plasmonic nanostructure in order to enhance absorption in particular spectral range. Since the plasmon induced effects depend crucially on the separation between the light-harvesting complex and the metallic nanoparticle, control of this distance is required [5-6]. In order to control this distance we use dielectric spacer layers. In this contribution we describe recent results of optical spectroscopy of hybrid nanostructures assembled from light-harvesting complexes and metallic nanoparticles. For the LH2 complex from purple bacteria coupled to a monolayer of Au spherical nanoparticles we observe enhancement of the fluorescence for separation of 12 nm [6]. Complementary time-resolved fluorescence measurements show no change of the fluorescence decay time, thus we attribute the enhancement to the increase of the absorption rate. We also tune the optical properties of the infrared absorption in the LH2 by using properly designed Au nanorods. The result is qualitatively similar, providing thus an elegant way to control the light-harvesting properties of natural photosynthetic systems through plasmon engineering. In this case we find strong spectral dependence of the fluorescence enhancement. Finally, we present possible ways to control circular dichroism in light-harvesting complexes via plasmon interactions. Financial support from the WELCOME program 'Hybrid nanostructures as a stepping-stone towards efficient artificial photosynthesis' awarded by the Foundation for Polish Science is gratefully acknowledged. [1] S. Mackowski (2010) J. Phys. Condens. Matter 22, 193102. [2] S. Mackowski, S. Wormke, A. J. Maier, T.H.P. Brotosudarmo, H. Harutyunyan, A. Hartschuh, A. O. Govorov, H. Scheer, C. Bruchle (2008) Nano Lett. 8, 558. [3] I. Carmeli, I. Lieberman, L. Kraversky, Z. Fan, A.O. Govorov, G. Markovich, S. Richter, (2010) Nano Lett. 10, 2069. [4] J.B. Nieder, R. Bittl, M. Brecht (2010) Angew. Chem. Int. Ed., 49, 1. [5] N. Czechowski, P. Nyga, M.K. Schmidt, T.H.P. Brotosudarmo, H. Scheer, D. Piatkowski, S. Mackowski, Plasmonics, 7, (2012) 115 |
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