Light-harvesting Systems Research Articles

Spontaneous Symmetry Breaking of Iridium and Ruthenium Metallophosphors for the Constructions of Chiral Light-Harvesting Systems

Spontaneous Symmetry Breaking of Iridium and Ruthenium Metallophosphors for the Constructions of Chiral Light-Harvesting Systems

Structure of a unique PSII-Pcb tetrameric megacomplex in a chlorophyll d-containing cyanobacterium.

Acaryochloris marina is a unique cyanobacterium using chlorophyll d (Chl d) as its major pigment and thus can use far-red light for photosynthesis. Photosystem II (PSII) of A. marina associates with a number of prochlorophyte Chl-binding (Pcb) proteins to act as the light-harvesting system. We report here the cryo-electron microscopic structure of a PSII-Pcb megacomplex from A. marina at a 3.6-angstrom overall resolution and a 3.3-angstrom local resolution. The megacomplex is organized as a tetramer consisting of two PSII core dimers flanked by sixteen symmetrically related Pcb proteins, with a total molecular weight of 1.9 megadaltons. The structure reveals the detailed organization of PSII core consisting of 15 known protein subunits and an unknown subunit, the assembly of 4 Pcb antennas within each PSII monomer, and possible pathways of energy transfer within the megacomplex, providing deep insights into energy transfer and dissipation mechanisms within the PSII-Pcb megacomplex involved in far-red light utilization.

Chiral silver cluster-based light-harvesting systems: Enantioselective chirality transfer and amplified circularly polarized luminescence

Chiral silver cluster-based light-harvesting systems: Enantioselective chirality transfer and amplified circularly polarized luminescence

Introduction of a terminal electron sink in chloroplasts decreases leaf cell expansion associated with higher proteasome activity and lower endoreduplication.

Foliar development involves successive phases of cell proliferation and expansion that determine the final leaf size, and is characterized by an early burst of reactive oxygen species generated in the photosynthetic electron transport chain (PETC). Introduction of the alternative PETC acceptor flavodoxin in tobacco chloroplasts led to a reduction in leaf size associated to lower cell expansion, without affecting cell number per leaf. Proteomic analysis showed that the biogenesis of the PETC proceeded stepwise in wild-type leaves, with accumulation of light-harvesting proteins preceding that of electron transport components, which might explain the increased energy and electron transfer to oxygen and reactive oxygen species build-up at this stage. Flavodoxin expression did not affect biogenesis of the PETC but prevented hydroperoxide formation through its function as electron sink. Mature leaves from flavodoxin-expressing plants were shown to contain higher levels of transcripts encoding components of the proteasome, a key negative modulator of organ size. Proteome profiling revealed that this differential accumulation was initiated during expansion and led to increased proteasomal activity, whereas a proteasome inhibitor reverted the flavodoxin-dependent size phenotype. Cells expressing plastid-targeted flavodoxin displayed lower endoreduplication, also associated to decreased organ size. These results provide novel insights into the regulation of leaf growth by chloroplast-generated redox signals, and highlight the potential of alternative electron shuttles to investigate the link(s) between photosynthesis and plant development.

Chiral Aggregation-Induced Emission Carbon Dot-Based Multicolor and Near-Infrared Circularly Polarized Delayed Fluorescence via a Light-Harvesting System.

Circularly polarized luminescence (CPL) materials are the research frontier of chiral luminescence. As a kind of luminescent carbon material, carbon dots (CDs) are expected to become excellent candidates for the construction of CPL materials. However, the construction of CD-based circularly polarized afterglow emission, especially multicolor and near-infrared emission, remains a great challenge due to aggregation-caused quenching and the instability of triplet excitons. In this work, we synthesized chiral CDs with aggregation-induced emission using dithiosalicylic acid and l/d-arginine as precursors through a one-step solvothermal method. Notably, the CDs exhibit green delayed fluorescence (DF) in poly(vinyl alcohol) films. Furthermore, multicolor and near-infrared circularly polarized delayed fluorescence is successfully realized via engineering a chiral light-harvesting system in which the CDs with green DF emission act as energy donors and fluorescent dyes with emission colors ranging from yellow to the near infrared serve as energy acceptors.

Linear and Nonlinear Optical Properties of All-cis and All-trans Poly(p-phenylenevinylene).

Poly(p-phenylenevinylene) (PPV) is a staple of the family of conjugated polymers with desirable optoelectronic properties for applications including light-emitting diodes (LEDs) and photovoltaic devices. Although the significant impact of olefin geometry on the steady-state optical properties of PPVs has been extensively studied, PPVs with precise stereochemistry have yet to be investigated using nonlinear optical spectroscopy for quantum sensing, as well as light harvesting for biological applications. Herein, we report our investigation of the influence of olefin stereochemistry on both linear and nonlinear optical properties through the synthesis of all-cis and all-trans PPV copolymers. We performed two-photon absorption (TPA) using a classical and entangled light source and compared both classical TPA and entangled two-photon absorption (ETPA) cross sections of these stereodefined PPVs. Whereas the TPA cross section of the all-trans PPV was expectedly higher than that of all-cis PPV, presumably because of the larger transition dipole moment, the opposite trend was measured via ETPA, with the all-cis PPV exhibiting the highest ETPA cross section. DFT calculations suggest that this difference might stem from the interaction of entangled photons with lower-lying electronic states in the all-cis PPV variant. Additionally, we explored the photoinduced processes for both cis and trans PPVs through time-resolved fluorescence upconversion and femtosecond transient absorption techniques. This study revealed that the sensitivity of PPVs in two-photon absorption varies with classical versus quantum light and can be modulated through the control of the geometry of the repeating alkenes, which is a key stepping stone toward their use in quantum sensing, bioimaging, and the design of polymer-based light-harvesting systems.

Bioinspired polymeric supramolecular columns as efficient yet controllable artificial light-harvesting platform

Light-harvesting is an indispensable process in photosynthesis, and researchers have been exploring various structural scaffolds to create artificial light-harvesting systems. However, achieving high donor/acceptor ratios for efficient energy transfer remains a challenge as excitons need to travel longer diffusion lengths within the donor matrix to reach the acceptor. Here, we report a polymeric supramolecular column-based light-harvesting platform inspired by the natural light-harvesting of purple photosynthetic bacteria to address this issue. The supramolecular column is designed as a discotic columnar liquid crystalline polymer and acts as the donor, with the acceptor intercalated within it. The modular columnar design enables an ultrahigh donor/acceptor ratio of 20000:1 and an antenna effect exceeding 100. Moreover, the spatial confinement within the supramolecular columns facilitates control over the energy transfer process, enabling dynamic full-color tunable emission for information encryption applications with spatiotemporal regulation security.

Description of a new freshwater bacterium Aquirufa regiilacus sp. nov., classification of the genera Aquirufa, Arundinibacter, Sandaracinomonas, and Tellurirhabdus to the family Spirosomataceae, classification of the genus Chryseotalea to the family Fulvivirgaceae and Litoribacter to the family Cyclobacteriaceae, as well as classification of Litoribacter alkaliphilus as a later heterotypic synonym of Litoribacter ruber

Strains LEOWEIH-7CT and LEPPI-3A were isolated from the Leopoldskroner Weiher, a lake located in the city of Salzburg, Austria. 16S rRNA gene similarities and phylogenetic reconstructions with 16S rRNA gene sequences as well as based on genome sequences revealed that the new strains belong to the A. antheringensis branch of the genus Aquirufa. Calculated whole-genome average nucleotide identity (gANI) and digital DNA–DNA hybridization (dDDH) values with the closely related type strains showed that the two strains represent a single new species. The strains grew aerobically and chemoorganotrophically, and the cells were rod shaped, on average 0.8 µm long and 0.3 µm wide, red pigmented and motile by gliding. The genome size of both strains was 2.6 Mbp and the G+C value was 41.9%. The genomes comprised genes predicted for the complete light-harvesting rhodopsin system and various carotenoids. We proposed to establish the name Aquirufa regiilacus sp. nov. for strain LEOWEIH-7CT (=DSM 116390T = JCM 36347T) as the type strain. Strain LEPPI-3A (=DSM 116391 = JCM 36348) also belongs to this new species. The calculated genome-based phylogenetic tree revealed that Aquirufa and some other genera currently allocated in the family Cytophagaceae need a reclassification. Aquirufa, Arundinibacter, Sandaracinomonas, and Tellurirhabdus should be designated to the family Spirosomataceae, the genus Chryseotalea to the family Fulvivirgaceae, and the genus Litoribacter to the family Cyclobacteriaceae. Furthermore, based on calculated gANI and dDDH values, Litoribacter alkaliphilus should be reclassified as a later heterotypic synonym of Litoribacter ruber.

Monitoring Hierarchical Assembly of Ring-in-Ring and Russian Doll Complexes Based on Carbon Nanoring by Förster Resonance Energy Transfer.

We presented the construction of the ring-in-ring and Russian doll complexes on the basis of triptycene-derived carbon nanoring (TP-[12]CPP), which not only acts as a host for pillar[5]arene (P5A) but also serves as an energy donor for building Förster resonance energy transfer (FRET) systems. We also demonstrated that their hierarchical assembly processes could be efficiently monitored in real time using FRET. NMR, UV-vis and fluorescence, and mass spectroscopy analyses confirmed the successful encapsulation of the guests P5A/P5A-An by TP-[12]CPP, facilitated by C-H···π and ···π interactions, resulting in the formation of a distinct ring-in-ring complex with a binding constant of Ka = 2.23 × 104 M-1. The encapsulated P5A/P5A-An can further reverse its role to be a host for binding energy acceptors to form Russian doll complexes, as evidenced by the occurrence of FRET and mass spectroscopy analyses. The apparent binding constant of the Russian doll complexes was up to 3.6 × 104 M-1, thereby suggesting an enhanced synergistic effect. Importantly, the Russian doll complexes exhibited both intriguing one-step and sequential FRET dependent on the subcomponent P5A/P5A-An during hierarchical assembly, reminiscent of the structure and energy transfer of the light-harvesting system presented in purple bacteria.

A supramolecular oligo[2]rotaxane constructed by orthogonal platinum(II) metallacycle and pillar[5]arene-based host–guest interactions

Oligo[n]rotaxanes are one of the most extensively studied categories of mechanically bonded macromolecules. In this study, a supramolecular oligo[2]rotaxane is successfully constructed driven by platinum(II) metallacycle and pillar[5]arene-based host–guest interactions in an orthogonal way. The supramolecular oligo[2]rotaxane is further applied in fabricating a light harvesting system.

A comparative physiological study of three red varieties in the Demarcated Douro Region

In certain regions, especially those with a Mediterranean climate, that are highly susceptible to climate change, viticulture is expected to become less suitable for the production of high-quality wines. From an evolutionary perspective, grapevine varieties have evolved genetic adaptations in the form of protective mechanisms to withstand summer stress, reflecting the climatic conditions in which grapevines were initially domesticated. The in-depth knowledge of the structural and functional characteristics of grapevines can aid in the identification and selection of varieties that are better suited to adverse environmental conditions and to the increasingly challenging conditions imposed by climate change. Following, this study aims to evaluate the extent to which the water status adjustment and the leaf biophysical and biochemical processes influence the respective photosynthetic performance of a currently neglected grapevine variety, Tinto Cão (TC) and two commonly used varieties in the Douro region, Touriga-Nacional (TN) and Tinta-Roriz (TR). The experiment was undertaken in the Baixo-Corgo sub-region of the Demarcated Douro Region in the north of Portugal. Grapevine water status, chlorophyll contents, leaf reflectance indices, chlorophyll a fluorescence (modulated and transient) and leaf gas exchange (including A/PPFD and A/Ci curves) were evaluated in three different phenological stages. The results indicate that, compared to TN and TR varieties, the TC minimizes the light-harvesting system while promoting thermal energy dissipation, which can be interpreted as photoprotective mechanisms at the photosynthetic apparatus level. These mechanisms imply the downregulation of the photochemical reactions but without significant losses of net productivity compared to TN, while TR remained increased. Despite the minor expression of Tinto-Cão nowadays, this variety can also have great adaptability for very hot and sunny wine-growing regions.

Construction and Performance Study of Artificial Light‐harvesting Based on Al3+ Fluorescence Regulation

AbstractA light‐emission system coordinating the amide 2‐amino‐3‐5‐dibromo‐N‐((2‐hydroxy‐naphthalene) benzoylhydrazine (R) and Al3+ was successfully prepared. Compared with that of R, the fluorescence emission band of the R–Al3+ group considerably improved. Therefore, using the R–Al3+ complex as a donor and two dyes (Nile Red and SR101) as acceptors, two artificial light–harvesting systems (ALHSs) were prepared. The energy transfer processes of the R–Al3+–Nile Red and R–Al3+–SR101 systems were confirmed. The findings will help in improving the current situation of ALHSs and have potential application value in ion detection and energy development.

Light-Harvesting Efficiency Cannot Depend on Optical Coherence in the Absence of Orientational Order.

The coherence of light has been proposed as a quantum-mechanical control for enhancing light-harvesting efficiency. In particular, optical coherence can be manipulated by changing either the polarization state or the spectral phase of the light. Here, we show that, in weak light, light-harvesting efficiency cannot be controlled using any form of optical coherence in molecular light-harvesting systems and, more broadly, those comprising orientationally disordered subunits and operating on longer-than-ultrafast time scales. Under those conditions, optical coherence does not affect the light-harvesting efficiency, meaning that it cannot be used for control. Specifically, polarization-state control is lost in disordered samples or when the molecules reorient on the time scales of light harvesting, and spectral-phase control is lost when the efficiency is time-averaged over a period longer than the optical coherence time. In practice, efficiency is always averaged over long times, meaning that coherent optical control is only possible through polarization and only in systems with orientational order.

Robust vibrational coherence protected by a core-shell structure in silver nanoclusters.

Vibrational coherence has attracted considerable research interests because of its potential functions in light harvesting systems. Although positive signs of vibrational coherence in metal nanoclusters have been observed, the underlying mechanism remains to be verified. Here, we demonstrate that robust vibrational coherence with a lifetime of 1 ps can be clearly identified in Ag44(SR)30 core-shell nanoclusters, in which an icosahedral Ag12 core is well protected by a dodecahedral Ag20 cage. Ultrafast spectroscopy reveals that two vibrational modes at around 2.4 THz and 1.6 THz, corresponding to the breathing mode and quadrupolar-like mode of the icosahedral Ag12 core, respectively, are responsible for the generation of vibrational coherence. In addition, the vibrational coherence of Ag44 has an additional high frequency mode (2.4 THz) when compared with that of Ag29, in which there is only one low frequency vibration mode (1.6 THz), and the relatively faster dephasing in two-layer Ag29 relative to that in Ag44 further supports the fact that the robust vibrational coherence in Ag44 is ascribed to its unique matryoshka-like core-shell structure. Our findings not only present unambiguous experimental evidence for a multi-layer core-shell structure protected vibrational coherence under ambient conditions but also offers a practical strategy for the design of highly efficient quantum optoelectronic devices.

Non-adiabatic molecular dynamics simulations provide new insights into the exciton transfer in the Fenna-Matthews-Olson complex.

A trajectory surface hopping approach, which uses machine learning to speed up the most time-consuming steps, has been adopted to investigate the exciton transfer in light-harvesting systems. The present neural networks achieve high accuracy in predicting both Coulomb couplings and excitation energies. The latter are predicted taking into account the environment of the pigments. Direct simulation of exciton dynamics through light-harvesting complexes on significant time scales is usually challenging due to the coupled motion of nuclear and electronic degrees of freedom in these rather large systems containing several relatively large pigments. In the present approach, however, we are able to evaluate a statistically significant number of non-adiabatic molecular dynamics trajectories with respect to exciton delocalization and exciton paths. The formalism is applied to the Fenna-Matthews-Olson complex of green sulfur bacteria, which transfers energy from the light-harvesting chlorosome to the reaction center with astonishing efficiency. The system has been studied experimentally and theoretically for decades. In total, we were able to simulate non-adiabatically more than 30 ns, sampling also the relevant space of parameters within their uncertainty. Our simulations show that the driving force supplied by the energy landscape resulting from electrostatic tuning is sufficient to funnel the energy towards site 3, from where it can be transferred to the reaction center. However, the high efficiency of transfer within a picosecond timescale can be attributed to the rather unusual properties of the BChl a molecules, resulting in very low inner and outer-sphere reorganization energies, not matched by any other organic molecule, e.g., used in organic electronics. A comparison with electron and exciton transfer in organic materials is particularly illuminating, suggesting a mechanism to explain the comparably high transfer efficiency.

Carbazole-based artificial light-harvesting system for photocatalytic cross-coupling dehydrogenation reaction.

A carbazole-based artificial light-harvesting system (LHS) was successfully fabricated based on the supramolecular assembly of AIE-enhanced donor (CTD), water-soluble phosphate-pillar[5]arene (WPP5), and eosin Y (ESY) acceptor. The formed WPP5-CTD possessed remarkable AIE emission, featuring an ideal energy donor for light harvesting. After encapsulation of ESY, the energy of WPP5-CTD was efficiently transferred to ESY in WPP5-CTD-ESY, and the antenna effect was 38.5, which was much higher than that of recently reported LHSs. Notably, WPP5-CTD-ESY was successfully utilized as a photocatalyst to realize the cross-coupling dehydrogenation reaction of diphenylphosphine oxide and benzothiazole derivatives, suggesting great potential for aqueous photocatalytic applications of this LHS.

A sequential light-harvesting system with thermosensitive colorimetric emission in both aqueous solution and hydrogel.

Inspired by natural photosynthetic systems that feature both sequential energy transfer and temperature response, we herein report an artificial thermosensitive sequential light-harvesting system (LHS) based on an amphiphilic molecule TPEO. It self-assembles into fluorescent nanoparticles in water and shows tunable LCST behavior. By loading ESY as the first acceptor and NiR as the second acceptor into the nanoparticles, an artificial LHS with two-step FRET was successfully constructed. Interestingly, the system exhibits thermosensitive colorimetric fluorescence in both aqueous solution and hydrogel by taking advantage of a combination of LCST and sequential FRET.

Ultra-low-power indoor light harvesting and solar cell characterisation system

Ultra-low-power indoor light harvesting and solar cell characterisation system

Cyclodextrin supramolecular assembly confined luminescent materials.

The macrocyclic supramolecular assembly confinement effect not only induces or extends the fluorescence/phosphorescence luminescence behavior of guest molecules but has also been widely applied in the research fields of chemistry, biology, and materials. This review primarily describes recent advances in cyclodextrin (CD) supramolecular assembly confined luminescent materials. Taking advantage of their hydrophobic cavity, CDs and their derivatives effectively encapsulate guest molecules and special functional groups or further assemble and polymerize to restrict the motion of guest chromophores, inducing and enhancing the luminescence behavior and realizing intelligent stimulus-responsive luminescence depending on changes in temperature, light, redox reactions and solvent polarity, which are successfully applied in targeted cell imaging, sensing, information encryption, anti-counterfeiting and flexible electronic light-emitting devices. With the emergence of new chromophores and CD primitives, spatial confinement within CD supramolecular assemblies will further realize the rapid development of supramolecular science and technology in circularly polarized luminescence, fluorescence/phosphorescence cascade energy transfer, light-harvesting energy-transfer systems and long persistent luminescent materials.

A multifunctional organogel for constructing artificial light harvesting systems with excellent energy transfer efficiency

Fluorescent gels with excellent physical properties were synthesised using polyvinyl alcohol/telmisartan. An artificial light-harvesting system with high energy-transfer efficiency and antenna effect was constructed by adding acridine yellow G and rhodamine B.