title: Plasmon enhanced light harvesting: multiscale modeling of the FMO protein coupled with gold nanoparticles.
abstract: Plasmonic systems, such as metal nanoparticles, are becoming increasingly important in spectroscopies and devices because of their ability to enhance, even by several orders of magnitude, the photophysical properties of neighboring systems. In particular, it has been shown both theoretically and experimentally that combining nanoplasmonic devices with natural light-harvesting proteins substantially increases the fluorescence and absorption properties of the system. This kind of biohybrid device can have important applications in the characterization and design of efficient light-harvesting systems. In the present work, the FMO light-harvesting protein was combined with gold nanoparticles of different sizes, and its photophysical properties were characterized using a multiscale quantum-mechanical classical-polarizable and continuum model (QM/MMPol/PCM). By optimal tuning of the plasmon resonance of the metal nanoparticles, fluorescence enhancements of up to 2 orders of magnitude were observed. Orientation effects were found to be crucial: amplifications by factors of up to 300 were observed for the absorption process, while the radiative decay of the emitting state increased at most by a factor of 10, mostly as a result of poor alignment of the emitting state with the considered metal aggregates. Despite being a limiting factor for high-fluorescence-enhancement devices, the strong orientation dependence may represent an important feature of the natural light-harvesting system that could allow selective enhancement of a specific excited state of the complex.
authors.affiliation: Department of Chemistry, University of Pisa, Via Moruzzi 3, 56124 Pisa, Italy.
authors.forename: Oliviero
authors.initials: O
authors.lastname: Andreussi
authors.affiliation: Department of Chemistry, University of Pisa, Via Moruzzi 3, 56124 Pisa, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Caprasecca
authors.affiliation: Department of Chemistry, University of Pisa, Via Moruzzi 3, 56124 Pisa, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Cupellini
authors.affiliation: Department of Chemistry, University of Pisa, Via Moruzzi 3, 56124 Pisa, Italy.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Guarnetti-Prandi
authors.affiliation: Department of Chemistry, University of Pisa, Via Moruzzi 3, 56124 Pisa, Italy.
authors.forename: Ciro A
authors.initials: CA
authors.lastname: Guido
authors.affiliation: Department of Chemistry, University of Pisa, Via Moruzzi 3, 56124 Pisa, Italy.
authors.forename: Sandro
authors.initials: S
authors.lastname: Jurinovich
authors.affiliation: Department of Chemistry, University of Pisa, Via Moruzzi 3, 56124 Pisa, Italy.
authors.forename: Lucas
authors.initials: L
authors.lastname: Viani
authors.affiliation: Department of Chemistry, University of Pisa, Via Moruzzi 3, 56124 Pisa, Italy.
authors.forename: Benedetta
authors.initials: B
authors.lastname: Mennucci
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D019414:Chlorobi; D003198:Computer Simulation; D005453:Fluorescence; D017612:Gold Compounds / Q000737:chemistry*; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008956:Models, Chemical; D055668:Photochemical Processes; D011789:Quantum Theory; D013057:Spectrum Analysis; D020349:Surface Plasmon Resonance
chemical_list: D001426:Bacterial Proteins; C086320:FMO bacteriochlorophyll protein, Bacteria; D017612:Gold Compounds; D045342:Light-Harvesting Protein Complexes