scholarly journals Broadband 2D Electronic Spectroscopy Reveals a Carotenoid Dark State in Purple Bacteria

Science ◽  
2013 ◽  
Vol 340 (6128) ◽  
pp. 52-56 ◽  
Author(s):  
Evgeny E. Ostroumov ◽  
Rachel M. Mulvaney ◽  
Richard J. Cogdell ◽  
Gregory D. Scholes
Keyword(s):  
Energy Flow ◽  
Light Harvesting ◽  
Purple Bacteria ◽  
Electronic Spectroscopy ◽  
Natural Light ◽  
Dark State ◽  
The Past ◽  
Transfer Processes ◽  
Harvesting Systems ◽  
Underlying Mechanisms

Although the energy transfer processes in natural light-harvesting systems have been intensively studied for the past 60 years, certain details of the underlying mechanisms remain controversial. We performed broadband two-dimensional (2D) electronic spectroscopy measurements on light-harvesting proteins from purple bacteria and isolated carotenoids in order to characterize in more detail the excited-state manifold of carotenoids, which channel energy to bacteriochlorophyll molecules. The data revealed a well-resolved signal consistent with a previously postulated carotenoid dark state, the presence of which was confirmed by global kinetic analysis. The results point to this state’s role in mediating energy flow from carotenoid to bacteriochlorophyll.

scholarly journals Structure, Dynamics, and Function in the Major Light-Harvesting Complex of Photosystem II

2012 ◽  
Vol 65 (6) ◽  
pp. 583 ◽  
Author(s):  
Gabriela S. Schlau-Cohen ◽  
Graham R. Fleming
Keyword(s):  
Excited State ◽  
Photosystem Ii ◽  
Light Harvesting ◽  
Protein Complexes ◽  
Electronic Spectroscopy ◽  
Emergent Properties ◽  
Light Harvesting Complex ◽  
Natural Systems ◽  
Harvesting Systems ◽  
And Function

In natural light-harvesting systems, pigment-protein complexes (PPC) convert sunlight to chemical energy with near unity quantum efficiency. PPCs exhibit emergent properties that cannot be simply extrapolated from knowledge of their component parts. In this Perspective, we examine the design principles of PPCs, focussing on the major light-harvesting complex of Photosystem II (LHCII), the most abundant PPC in green plants. Studies using two-dimensional electronic spectroscopy (2DES) provide an incisive tool to probe the electronic, energetic, and spatial landscapes that enable the efficiency observed in photosynthetic light-harvesting. Using the information about energy transfer pathways, quantum effects, and excited state geometry contained within 2D spectra, the excited state properties can be linked back to the molecular structure. This understanding of the structure-function relationships of natural systems constitutes a step towards a blueprint for the construction of artificial light-harvesting devices that can reproduce the efficacy of natural systems.

scholarly journals All-optical manipulation of singlet exciton transport in individual supramolecular nanostructures by triplet gating

2021 ◽  
Author(s):  
Bernd Wittmann ◽  
Till Biskup ◽  
Klaus Kreger ◽  
Jürgen Köhler ◽  
Hans-Werner Schmidt ◽  
...  
Keyword(s):  
Excitation Energy ◽  
Organic Molecules ◽  
Light Harvesting ◽  
Optical Manipulation ◽  
Natural Light ◽  
Singlet Exciton ◽  
Directed Transport ◽  
Exciton Transport ◽  
All Optical ◽  
Harvesting Systems

Directed transport of singlet excitation energy is a key process in natural light-harvesting systems and a desired feature in assemblies of functional organic molecules for organic electronics and nanotechnology applications....

scholarly journals Manipulation of supramolecular 2D assembly of functional dyes toward artificial light-harvesting systems

2015 ◽  
Vol 87 (1) ◽  
pp. 3-14 ◽  
Author(s):  
Yohei Ishida
Keyword(s):  
Energy Transfer ◽  
Light Harvesting ◽  
Purple Bacteria ◽  
Short Review ◽  
Artificial Light ◽  
Effective Utilization ◽  
Host Interactions ◽  
Excellent Research ◽  
Harvesting Systems ◽  
Functional Dyes

AbstractIn recent years, excellent research has revealed that light-harvesting systems (LHSs) are composed of beautifully aligned chlorophyll molecules; the regulated alignment of chlorophylls is responsible for the efficient and selective light-harvesting energy transfer processes in purple bacteria. This finding led to the construction of a regularly arranged assembly of functional dyes as a step toward fabricating artificial LHSs. While most approaches toward the construction of dye assemblies have depended on molecular interactions such as covalent, coordination, and hydrogen bonds, my approach involves guest–host interactions using an inorganic nanosheet as the host material. This short review presents the construction of a 2D dye assembly and its effective utilization in artificial light-harvesting applications. Owing to the highly stable and uniform 2D alignment of functional dyes on inorganic nanosheets, nearly 100 % singlet–singlet energy transfer and efficient light-harvesting were achieved. I believe that the results presented herein will contribute to the construction of efficient photochemical reaction systems in supramolecular host–guest assemblies, which may facilitate the realization of artificial photosynthesis.

scholarly journals Fully Quantum Modeling of Exciton Diffusion in Mesoscale Light Harvesting Systems

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3291
Author(s):  
Fulu Zheng ◽  
Lipeng Chen ◽  
Jianbo Gao ◽  
Yang Zhao
Keyword(s):  
Light Harvesting ◽  
Purple Bacteria ◽  
Time Dependent ◽  
Graphic Processing Units ◽  
Exciton Diffusion ◽  
Quantum Mechanical Treatment ◽  
Exciton Transfer ◽  
Harvesting Systems ◽  
Intractable Problem ◽  
Computational Resources

It has long been a challenge to accurately and efficiently simulate exciton–phonon dynamics in mesoscale photosynthetic systems with a fully quantum mechanical treatment due to extensive computational resources required. In this work, we tackle this seemingly intractable problem by combining the Dirac–Frenkel time-dependent variational method with Davydov trial states and implementing the algorithm in graphic processing units. The phonons are treated on the same footing as the exciton. Tested with toy models, which are nanoarrays of the B850 pigments from the light harvesting 2 complexes of purple bacteria, the methodology is adopted to describe exciton diffusion in huge systems containing more than 1600 molecules. The superradiance enhancement factor extracted from the simulations indicates an exciton delocalization over two to three pigments, in agreement with measurements of fluorescence quantum yield and lifetime in B850 systems. With fractal analysis of the exciton dynamics, it is found that exciton transfer in B850 nanoarrays exhibits a superdiffusion component for about 500 fs. Treating the B850 ring as an aggregate and modeling the inter-ring exciton transfer as incoherent hopping, we also apply the method of classical master equations to estimate exciton diffusion properties in one-dimensional (1D) and two-dimensional (2D) B850 nanoarrays using derived analytical expressions of time-dependent excitation probabilities. For both coherent and incoherent propagation, faster energy transfer is uncovered in 2D nanoarrays than 1D chains, owing to availability of more numerous propagating channels in the 2D arrangement.

scholarly journals Modeling the optical properties of excitons in linear and tubular J-aggregates

2006 ◽  
Vol 2006 ◽  
pp. 1-10 ◽  
Author(s):  
Jasper Knoester
Keyword(s):  
Optical Properties ◽  
Fluorescence Spectra ◽  
Light Harvesting ◽  
Cyanine Dyes ◽  
Natural Light ◽  
Artificial Light ◽  
Absorption And Fluorescence Spectra ◽  
Harvesting Systems ◽  
J Aggregates ◽  
Frenkel Excitons

The theory of the optical properties of linear and tubular molecular J-aggregates is reviewed. The primary optical excitations in these systems are Frenkel excitons, which may be delocalized over many molecules. The collective nature of these excitations gives rise to special optical properties and dynamics, which are of interest for purely scientific reasons, but also enable the application of J-aggregates as photographic sensitizers and artificial light-harvesting systems. The focus of this paper is on the effect of aggregate geometry, disorder, and temperature on the absorption and fluorescence spectra. Also transport of excitations between J-aggregates is discussed. Connection is made to experiments on aggregates of cyanine dyes and natural light-harvesting systems.

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