Artificial Light-harvesting Antenna Research Articles

Efficient two-step excitation energy transfer in artificial light-harvesting antenna based on bacteriochlorophyll aggregates

Chlorosomes of green photosynthetic bacteria are large light-harvesting complexes enabling these organisms to survive at extremely low-light conditions. Bacteriochlorophylls found in chlorosomes self-organize and are ideal candidates for use in biomimetic light-harvesting in artificial photosynthesis and other applications for solar energy utilization. Here we report on the construction and characterization of an artificial antenna consisting of bacteriochlorophyll c co-aggregated with β-carotene, which is used to extend the light-harvesting spectral range, and bacteriochlorophyll a, which acts as a final acceptor for excitation energy. Efficient energy transfer between all three components was observed by means of fluorescence spectroscopy. The efficiency varies with the β-carotene content, which increases the average distance between the donor and acceptor in both energy transfer steps. The efficiency ranges from 89 to 37% for the transfer from β-carotene to bacteriochlorophyll c, and from 93 to 69% for the bacteriochlorophyll c to bacteriochlorophyll a step. A significant part of this study was dedicated to a development of methods for determination of energy transfer efficiency. These methods may be applied also for study of chlorosomes and other pigment complexes.

AIE Luminogen-Rhodamine 6G FRET pair based light harvester and Hg2+ chemosensor for real life applications

Aggregation Induced Emission (AIE) is an intriguing photophysical phenomenon exhibited by certain chromophores that are non-emissive in dilute solutions but are induced to emit light upon aggregation. A “Turn-on” emission has been observed in Dodecyl Carbazole-Barbituric acid conjugate (DCBA) with the addition of poor solvent like water. FRET between an AIE luminogen- DCBA as donor and Rh6G as acceptor has been investigated using steady-state and time-resolved fluorescence studies. There is a significant spectral overlap between the AIE emission of DCBA and the absorption spectra of Rh6G in 9:1 water to THF binary solution. DCBA AIE emission quenching upon addition of Rh6G is identified as due to FRET. The energy transfer efficiency is found to increase linearly with acceptor concentration, reaching an optimum efficiency of 43 %. It holds the promise of being a multiple-donor single-acceptor artificial light harvesting antenna, with an antenna effect of 20.5 %. The proposed FRET system demonstrates excellent pH stability in pH range of 3 to 11. This FRET pair can serve as a turn off fluorescent probe in real water samples and live cells for sensing of Hg2+ ions with high sensitivity, selectivity, and low cytotoxicity. The sensor is also effective for paper strip based Hg2+ detection.

Bio-templated energy transfer system for constructing artificial light-harvesting antennae, white light generation, and photonic nanowires

Developing environmentally friendly, sustainable, and biocompatible artificial light-harvesting systems has become an essential area of research to understand natural light-harvesting processes involving multistep resonance energy transfer and building efficient energy conversion systems related to energy and optoelectronic applications. In this direction, bio-scaffolded artificial energy transfer systems for panchromatic light collection and sequential energy transfer have fascinated the scientific community. In this review, we have discussed what the dynamic structure and intrinsic physical properties of biomolecules like deoxyribonucleic acid, proteins, and peptides can provide for the development of new optical devices, sustainable and environmentally friendly white emitting materials, and cascaded energy transfer systems for energy harvesting from light. In doing so, we have highlighted some of the recent advances in bio-scaffolds as a platform for the assembly of different types of donor–acceptor chromophores involved in fluorescence energy transfer.

Delocalized Excitation or Intramolecular Energy Transfer in Pyrene Core Dendrimers.

Light-harvesting and then intramolecular energy transfer are the crucial steps in natural photosynthesis. Dendrimers are one of the most promising artificial light-harvesting antennas. Insight into the relationship between molecular structure and energy transfer (or delocalized excitation) in dendrimers would help in understanding and mimicking photosynthesis. Here, a series of dendrimers T1-T4 based on pyrene as a core and fluorene/carbazole as the dendrons have been studied with time-resolved fluorescence and femtosecond transient absorption spectroscopies, revealing that the large planar structure of T1 and T2 has led to strong coupling of pyrene and fluorene units, enabling delocalized excitation over the entire molecules. But for T3 and T4, the carbazole units linking the first- and second-generation branches have broken the planar structure and suppressed the π-electron delocalization, enabling the Förster resonance energy transfer. The efficient intramolecular energy transfer from peripheral branches to the core occurs within 2 ps.

Quantum Chemical Simulation of the Qy Absorption Spectrum of Zn Chlorin Aggregates for Artificial Photosynthesis.

Zn chlorin (Znchl) is easy to synthesize and has similar optical properties to those of bacteriochlorophyll c in the nature, which is expected to be used as a light-harvesting antenna system in artificial photosynthesis. In order to further explore the optical characteristics of Znchl, various sizes of a parallel layered Znchl-aggregate model and the THF-Znchl explicit solvent monomer model were constructed in this study, and their excited state properties were simulated by using time-dependent density functional theory (TDDFT) and exciton theory. For the Znchl monomer, with a combination of the explicit solvent model and the implicit solvation model based on density (SMD), the calculated excitation energy agreed very well with the experimental one. The Znchl aggregates may be simplified to a Zn36 model to reproduce the experimental absorption spectrum by the Förster coupling theory. The proposed Znchl aggregate model provides a good foundation for the future exploration of other properties of Znchl and simulations of artificial light-harvesting antennas. The results also indicate that J-aggregrates along z-direction, due to intermolecular coordination bonds, are the dominant factor in extending the band of Znchl into the near infrared region.

A stimuli responsive lanthanide-based hydrogel possessing tunable luminescence by efficient energy transfer pathways

Energy transfer as an important component in light-harvesting antenna systems can mimic effectively natural photosynthesis processes, showing great potential in optoelectronic devices. Herein, we report a responsive polymeric hydrogel based on the combination of excited state intramolecular proton transfer (ESIPT) molecule (Salicylic acid, Sal) and terbium (III) (Tb3+), as enabled by external stimuli to construct artificial light-harvesting antenna systems. Benefiting from unique photophysical properties of Sal, the synthesized hydrogel displays a temperature-dependent reversible opaque ↔ transparent states transition, accompanied with an interesting photoluminescence behavior. Moreover, by further incorporating europium (III) (Eu3+) into the hydrogel, we demonstrate well-defined cascades of energy transfer that provides a tunable optical output from the collection of lanthanides by the excitation of a common sensitizer (Sal) upon base vapor stimulation. Efficient energy transfer efficiency from Tb3+ to Eu3+, as high as 97.8%, was also obtained as established by the time-resolved fluorescence spectroscopy analysis.

Bioinspired supramolecular nanosheets of zinc chlorophyll assemblies

Two-dimensional sheet-like supramolecules have attracted much attention from the viewpoints of their potential application as functional (nano)materials due to unique physical and chemical properties. One of the supramolecular sheet-like nanostructures in nature is visible in the self-assemblies of bacteriochlorophyll-c–f pigments inside chlorosomes, which are major components in the antenna systems of photosynthetic green bacteria. Herein, we report artificial chlorosomal supramolecular nanosheets prepared by the self-assembly of a synthetic zinc 31-methoxy-chlorophyll derivative having amide and urea groups in the substituent at the 17-position. The semi-synthetic zinc chlorophyll derivative kinetically formed dimeric species and transformed into more thermodynamically stable chlorosomal J-aggregates in the solid state. The kinetically and thermodynamically formed self-assemblies had particle-like and sheet-like supramolecular nanostructures, respectively. The resulting nanosheets of biomimetic chlorosomal J-aggregates had flat surfaces and well-ordered supramolecular structures. The artificial sheet-like nanomaterial mimicking chlorosomal bacteriochlorophyll-c–f J-aggregates was first constructed by the model molecule, and is potentially useful for various applications including artificial light-harvesting antennas and photosyntheses.

Enhancement of Photocurrent by Integration of an Artificial Light-Harvesting Antenna with a Photosystem I Photovoltaic Device

Photosynthetic pigment–protein-based biophotovoltaic devices are attracting interest as environmentally friendly energy sources. Photosystem I (PSI), a photosynthetic pigment–protein, is a proven biophotovoltaic material because of its abundance and high charge separation quantum efficiency. However, the photocurrent of these biophotovoltaic devices is not high because of their low spectral response. We have integrated an artificial light-harvesting antenna into a PSI-based biophotovoltaic device to expand the spectral response. To fabricate the device, a perylene di-imide derivative (PTCDI) was introduced onto a TiO2 surface as an artificial antenna. In the photovoltaic cells formed by the PTCDI/PSI-assembled TiO2 electrode, the magnitude of the incident photon-to-current conversion efficiency spectrum was significantly enhanced in the range 450–750 nm, and the photocurrent increased to 0.47 mA/cm2. The result indicates that the photons absorbed by PTCDI transfer to PSI via Forster resonance energy transfer.

Disassembly of an Interconjugated Polyelectrolyte Complex Using Ionic Surfactants

The ability to manipulate the state of assembly of light-harvesting molecular materials can be important to control light-induced damage at high illumination intensities. Disassembly of such materials is thus an important consideration from a photoprotection perspective. Here, we show that an artificial light-harvesting antenna based on an interconjugated polyelectrolyte complex can be disassembled using ionic surfactants in aqueous solution. We demonstrate that both anionic and cationic surfactants can do so with comparable efficiency, thereby shutting electronic energy transfer between the exciton donor and acceptor conjugated polyelectrolytes. However, the structural evolution of the aqueous complexes both above and below the critical micelle concentration differed significantly depending on the sign of the ionic surfactant and the relative polyion charge ratio.

Real-Space Investigation of Energy Transfer through Electron Tomography

We herein report the first real-space investigation of Forster resonance energy transfer (FRET) in two different types of quantum dot (QD) supramolecular assemblies by observing their three-dimensional (3D) configurations through high-resolution electron tomography. Owing to its critical role in photosynthesis, artificial light-harvesting antennas, and investigation of protein–protein interactions, the mechanism of FRET has been intensively studied by monitoring its excited-state dynamics via various spectroscopic techniques. The utilized electron tomography technique allowed the direct localization of 3D coordinates of individual QDs in self-assembled nanostructures and theoretical estimation of the FRET efficiency of a single fluorophore, domain, or supramolecular assembly. Moreover, the experimental value of the FRET efficiency determined by fluorescence spectroscopy was in good agreement with the magnitude obtained via electron tomography. We believe that the described strategy can be used in single-m...

Orange Carotenoid Protein as a Control Element in an Antenna System Based on a DNA Nanostructure.

Taking inspiration from photosynthetic mechanisms in natural systems, we introduced a light-sensitive photo protective quenching element to an artificial light-harvesting antenna model to control the flow of energy as a function of light intensity excitation. The orange carotenoid protein (OCP) is a nonphotochemical quencher in cyanobacteria: under high-light conditions, the protein undergoes a spectral shift, and by binding to the phycobilisome, it absorbs excess light and dissipates it as heat. By the use of DNA as a scaffold, an antenna system made of organic dyes (Cy3 and Cy5) was constructed, and OCP was assembled on it as a modulated quenching element. By controlling the illumination intensity, it is possible to switch the direction of excitation energy transfer from the donor Cy3 to either of two acceptors. Under low-light conditions, energy is transferred from Cy3 to Cy5, and under intense illumination, energy is partially transferred to OCP as well. These results demonstrate the feasibility of controlling the pathway of energy transfer using light intensity in an engineered light-harvesting system.

Two-dimensional artificial light-harvesting antennae with predesigned high-order structure and robust photosensitising activity.

Highly ordered discrete assemblies of chlorophylls that are found in natural light-harvesting antennae are key to photosynthesis, which converts light energy to chemical energy and is the principal producer of organic matter on Earth. Porphyrins and phthalocyanines, which are analogues of chlorophylls, exhibit a strong absorbance of visible and near-infrared light, respectively. A highly ordered porphyrin-co-phthalocyanine antennae would harvest photons over the entire solar spectrum for chemical transformation. However, such a robust antennae has not yet been synthesised. Herein, we report a strategy that merges covalent bonds and noncovalent forces to produce highly ordered two-dimensional porphyrin-co-phthalocyanine antennae. This methodology enables control over the stoichiometry and order of the porphyrin and phthalocyanine units; more importantly, this approach is compatible with various metalloporphyrin and metallophthalocyanine derivatives and thus may lead to the generation of a broad structural diversity of two-dimensional artificial antennae. These ordered porphyrin-co-phthalocyanine two-dimensional antennae exhibit unique optical properties and catalytic functions that are not available with single-component or non-structured materials. These 2D artificial antennae exhibit exceptional light-harvesting capacity over the entire solar spectrum as a result of a synergistic light-absorption effect. In addition, they exhibit outstanding photosensitising activities in using both visible and near-infrared photons for producing singlet oxygen.

Exciton Migration and Surface Trapping for a Photonic Crystal Displaying Charge-Recombination Fluorescence.

A compact donor-acceptor molecular dyad has been synthesized by attaching an N,N-dimethylamino fragment to a naphthalic anhydride residue. The dyad shows fluorescence from an intramolecular charge-transfer state (i.e., charge-recombination fluorescence) in solution, with the photo-physical properties being strongly dependent on the solvent polarity. Similar emission is seen for single crystals of the target compound, the molecules being aligned head-to-head, although time-resolved emission profiles display dual-exponential kinetics. A second polymorph with the head-to-tail alignment also gives rise to two lifetimes that differ somewhat from those of the first structure, which are assigned to bulk and surface-bound molecules. Growing the crystal in the presence of Rhodamine B localizes the dye around the surface. Excitation of the crystal is followed by sub-ps exciton migration along the aligned stacks, with occasional crossing to adjacent stacks and trapping at the surface. Rhodamine B present at very low levels acts as the acceptor for excitons entering the surface layer. Crystals embedded in a polyester resin form an artificial light-harvesting antenna able to sensitize an amorphous silicon solar cell.

Exciton Transfer and Emergent Excitonic States in Oppositely-Charged Conjugated Polyelectrolyte Complexes.

Photosynthetic organisms have mastered the use of "soft" macromolecular assemblies for light absorption and concentration of electronic excitation energy. Nature's design centers on an optically inactive protein-based backbone that acts as a host matrix for an array of light-harvesting pigment molecules. The pigments are organized in space such that excited states can migrate between molecules, ultimately delivering the energy to the reaction center. Here we report our investigation of an artificial light-harvesting energy transfer antenna based on complexes of oppositely charged conjugated polyelectrolytes (CPEs). The conjugated backbone and the charged side chains of the CPE lead to an architecture that simultaneously functions as a structural scaffold and an electronic energy "highway". We find that the process of ionic complex formation leads to a remarkable change in the excitonic wavefunction of the energy acceptor, which manifests in a dramatic increase in the fluorescence quantum yield. We argue that the extended backbone of the donor CPE effectively templates a planarized acceptor polymer, leading to excited states that are highly delocalized along the polymer backbone.

Three-dimensional nano-optical assembly of antenna structures with collective near-field coupling

Metallic nanostructures are used for various applications because of their characteristic optical responses that generate strong near-fields. We have theoretically clarified that the configuration of nanoparticles (NPs) and their optical properties can be controlled by optical manipulation. In this study, we greatly improved our previously reported simulation method, and this improvement enables investigation of the stable states of optically trapped NPs in a three-dimensional system. On the basis of this method, the assembly process of rod-shaped silver NPs is concisely clarified, where NPs of a specific shape are selectively assembled even in a mixture of NPs of different shapes. In particular, our simulation method clarifies how a light-induced force drives assembly processes, which is an important subject to consider for extending the degree of freedom of an optical manipulation. Furthermore, as reported in our previous studies, an assembled structure inherits the properties of light used for the optical trapping; e.g., rod-shaped silver NPs are radially connected to each other and assembled into a ring-shaped structure under the irradiation of a radially polarized vector beam with a ring-shaped intensity distribution. The assembled structure is an artificial light-harvesting antenna because it theoretically exhibits an enhancement of near-field and extinction in a broader wavelength range than that of the original NPs composing the antenna and also a response to the non-polarized light such as the sunlight. On the basis of an optically manipulated configuration of NPs and their optical properties, we discuss the selective optical assembly in a three-dimensional simulation.

Photochemical Bleaching of an Elaborate Artificial Light-Harvesting Antenna.

The target artificial light-harvesting antenna, comprising 21 discrete chromophores arranged in a logical order, undergoes photochemical bleaching when dispersed in a thin plastic film. The lowest-energy component, which has an absorption maximum at 660 nm, bleaches through first-order kinetics at a relatively fast rate. The other components bleach more slowly, in part, because their excited-state lifetimes are rendered relatively short by virtue of fast intramolecular electronic energy transfer to the terminal acceptor. Two of the dyes, these being close to the terminal acceptor but interconnected through a reversible energy-transfer step, bleach by way of an autocatalytic step. Loss of the terminal acceptor, thereby switching off the energy-transfer route, escalates the rate of bleaching of these ancillary dyes. The opposite terminal, formed by a series of eight pyrene-based chromophores, does not bleach to any significant degree. Confirmation of the various bleaching steps is obtained by examination of an antenna lacking the terminal acceptor, where the autocatalytic route does not exist and bleaching is very slow.

Artificial light-harvesting arrays for solar energy conversion.

Solar fuel production, the process whereby an energy-rich substance is produced using electrons provided by water under exposure to sunlight, requires the cooperative accumulation of multiple numbers of photons. Identifying the optimum reagents is a difficult challenge, even without imposing the restriction that these same materials must function as both sensitiser and catalyst. The blockade caused by an inadequate supply of photons at the catalytic sites might be resolved by making use of an artificial light-harvesting array whose sole purpose is to funnel photons of appropriate frequency to the active catalyst, which can now be a dark reagent. Here we consider several types of artificial photon collectors built from fluorescent modules interconnected via electronic energy transfer. Emphasis is placed on the materials aspects and on establishing the basic operating principles.

Solvent-dependent Photoreactions of Porphyrin-Spiropyran Dyad: Ring-opening or Protonation

E-mail: ejs@sunchon.ac.krReceived July 5, 2013, Accepted July 17, 2013Key Words : Porphyrin, Diprotonated porphyrin, Spiropyran, Merocyanine, AggregationPorphyrin (Por) has a strong absorption characteristics inthe range of sunlight due to a chemical structure of highconjugation and rigidity, good redox properties, and well-established synthetic methods. Accordingly, porphyrin-basedmulticomponent compounds have been investigated in avariety of applications such as artificial light-harvestingantenna, molecular energy storage devices, solar cells, opto-electronic switches, and photodynamic therapy.

Structure Determination of a Bio-Inspired Self-Assembled Light-Harvesting Antenna by Solid-State NMR and Molecular Modeling

The molecular stacking of an artificial light-harvesting antenna self-assembled from 3(1)-aminofunctionalized zinc-chlorins was determined by solid-state NMR in combination with quantum-chemical and molecular-mechanics modeling. A library of trial molecular stacking arrangements was generated based on available structural data for natural and semisynthetic homologues of the Zn-chlorins. NMR assignments obtained for the monomer in solution were validated for self-assembled aggregates and refined with (1)H-(13)C heteronuclear correlation spectroscopy data collected from samples with (13)C at natural abundance. Solid-state ring-current shifts for the (1)H provided spatial constraints to determine the molecular overlap. This procedure allows for a discrimination between different self-assembled structures and a classification of the stacking mode in terms of electric dipole alignment and π-π interactions, parameters that determine the functional properties of light-harvesting assemblies and conducting nanowires. The combination with quantum-mechanical modeling then allowed building a low-resolution packing model in silico from molecular stacks. The method allows for moderate disorder and residual polymorphism at the stack or molecular level and is generally applicable to determine molecular packing structures of aromatic molecules with structural asymmetry, such as is commonly provided by functionalized side chains that serve to tune the self-assembly process.

Bio-inspired artificial light-harvesting antennas for enhancement of solar energy capture in dye-sensitized solar cells

Download options Please wait... Article information DOI https://doi.org/10.1039/C3EE24229C Article type Perspective Submitted 29 Nov 2012 Accepted 01 Feb 2013 First published 01 Feb 2013 Download Citation Energy Environ. Sci., 2013,6, 2041-2052 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Bio-inspired artificial light-harvesting antennas for enhancement of solar energy capture in dye-sensitized solar cells F. Odobel, Y. Pellegrin and J. Warnan, Energy Environ. Sci., 2013, 6, 2041 DOI: 10.1039/C3EE24229C To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Fabrice Odobel Yann Pellegrin Julien Warnan