Long-distance Energy Transfer Research Articles

Polariton-assisted long-distance energy transfer between excitons in two-dimensional semiconductors

Polariton-assisted long-distance energy transfer between excitons in two-dimensional semiconductors

Excitation-Dependent High-Lying Excitonic Exchange via Interlayer Energy Transfer from Lower-to-Higher Bandgap 2D Material.

High light absorption (∼15%) and strong photoluminescence (PL) emission in monolayer (1L) transition metal dichalcogenides (TMDs) make them ideal candidates for optoelectronic device applications. Competing interlayer charge transfer (CT) and energy transfer (ET) processes control the photocarrier relaxation pathways in TMD heterostructures (HSs). In TMDs, long-distance ET can survive up to several tens of nm, unlike the CT process. Our experiment shows that an efficient ET occurs from the 1Ls WSe2-to-MoS2 with an interlayer hexagonal boron nitride (hBN), due to the resonant overlapping of the high-lying excitonic states between the two TMDs, resulting in enhanced HS MoS2 PL emission. This type of unconventional ET from the lower-to-higher optical bandgap material is not typical in the TMD HSs. With increasing temperature, the ET process becomes weaker due to the increased electron-phonon scattering, destroying the enhanced MoS2 emission. Our work provides new insight into the long-distance ET process and its effect on the photocarrier relaxation pathways.

Nanodiscs as a novel approach to resolve inter-protein energy transfer within the photosynthetic membrane of purple bacteria.

Photosynthetic purple bacteria capture sunlight and convert it to chemical energy with almost 100% quantum efficiency: almost every photon absorbed leads to charge separation. Such high efficiency is achieved through a series of ultrafast inter-protein energy transfer events within an antenna network of light-harvesting proteins located in the photosynthetic membrane. Understanding how the organization of proteins within the membrane leads to efficient energy transfer is imperative to designing efficient artificial solar harvesting techniques. Determining inter-protein energy transfer between light-harvesting complex 2 (LH2) proteins, the most common light-harvesting protein in vivo, has proven challenging due to the heterogeneous organization of proteins within the membrane environment. In this work, we introduce model membrane nanodiscs as a novel technique to reconstruct the complex membrane environment in a controlled manner. By forming nanodiscs large enough to incorporate two variants of LH2, we can directly resolve inter-protein energy transfer. By controlling nanodisc size, we can change the inter-protein distance and resolve the effect of membrane organization on energy transfer rate. Using a combination of ultrafast transient absorption spectroscopy, cryogenic electron microscopy, and quantum chemical calculations, we find that LH2 complexes prefer to associate closely in the membrane (25 Å), with an energy transfer rate of 5.7 ps. The results suggest that these tightly-packed LH2s are important for long-distance energy transfer, as the 25 Å distance is similar to the most common inter-protein distance in vivo. Overall, our work introduces nanodiscs as a platform to study complex energy transfer events and the effect of membrane organization on critical biological processes.

Photon upconversion through triplet exciton-mediated energy relay

Exploration of upconversion luminescence from lanthanide emitters through energy migration has profound implications for fundamental research and technology development. However, energy migration-mediated upconversion requires stringent experimental conditions, such as high power excitation and special migratory ions in the host lattice, imposing selection constraints on lanthanide emitters. Here we demonstrate photon upconversion of diverse lanthanide emitters by harnessing triplet exciton-mediated energy relay. Compared with gadolinium-based systems, this energy relay is less dependent on excitation power and enhances the emission intensity of Tb3+ by 158-fold. Mechanistic investigations reveal that emission enhancement is attributable to strong coupling between lanthanides and surface molecules, which enables fast triplet generation (<100 ps) and subsequent near-unity triplet transfer efficiency from surface ligands to lanthanides. Moreover, the energy relay approach supports long-distance energy transfer and allows upconversion modulation in microstructures. These findings enhance fundamental understanding of energy transfer at molecule-nanoparticle interfaces and open exciting avenues for developing hybrid, high-performance optical materials.

Defect-Tolerant Plasmonic Elliptical Resonators for Long-Range Energy Transfer.

Energy transfer allows energy to be moved from one quantum emitter to another. If this process follows the Förster mechanism, efficient transfer requires the emitters to be extremely close (<10 nm). To increase the transfer range, nanophotonic structures have been explored for photon- or plasmon-mediated energy transfer. Here, we fabricate high-quality silver plasmonic resonators to examine long-distance plasmon-mediated energy transfer. Specifically, we design elliptical resonators that allow energy transfer between the foci, which are separated by up to 10 μm. The geometry of the ellipse guarantees that all plasmons emitted from one focus are collected and channeled through different paths to the other focus. Thus, energy can be transferred even if a micrometer-sized defect obstructs the direct path between the focal points. We characterize the spectral and spatial profiles of the resonator modes and show that these can be used to transfer energy between green- and red-emitting colloidal quantum dots printed with subwavelength accuracy using electrohydrodynamic nanodripping. Rate-equation modeling of the time-resolved fluorescence from the quantum dots further confirms the long-distance energy transfer.

Analytical Model of a 25–50 m Robust Single-Wire Electric-Field Coupling Power Transfer System Using a Limiter

A 25–50 m robust single-wire electric-field coupling power transfer (ECPT) system using a limiter is presented. Extending the transfer distance is always the key issue in energy transfer fields, whereas the distance of wireless power transfer systems is limited to several meters. On the other hand, characteristics of the traditional single-wire ECPT systems are very sensitive to the transfer distance. Solving these problems, in the range of tens of meters, the proposed scheme can eliminate the decrease of the transfer efficiency and variation of the output power without any tuning, which realizes strictly stable and long-distance energy transfer. The coupled-mode model of the system is built first, and then the transfer performances are analyzed. The modal solutions and action mechanism of the system are specified. Furthermore, the parameter design method to realize target efficiency and critical distance is also presented. A circuit model is built to verify the theoretical analysis. Simulated results indicate that, within the critical distance, the proposed system can achieve energy transfer with constant efficiency of 50% and constant output power of 4.1 kW, which does not need any tuning. Besides, the critical distance can be achieved from about 25 m to 50 m by adjusting the system parameters.

Hydrothermal synthesis of NaYF&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;:Yb&amp;lt;sup&amp;gt;3+&amp;lt;/sup&amp;gt;,Sm&amp;lt;sup&amp;gt;3+&amp;lt;/sup&amp;gt; and photo-thermal effect under 980 nm excitation

In this paper, NaYF4:Yb3+,Sm3+ optical heaters were prepared by a simple hydrothermal method. Based on a reliable upconversion luminescence thermometer, its photothermal conversion properties under 980 nm radiation were studied. To overcome the thermal effects caused by laser radiation, an intermittent spectral scanning method was used to study the relationship between NaYF4:Yb3+,Sm3+ photothermal conversion and pumping power density. The results show that the temperature of the laser radiation point is linearly related to the pumping power density. More interestingly, it is noted that the photothermal response depends on the Yb3+ doping concentration. The 95% Yb3+ doping shows the strongest photogenerated heat at low power density, but the 60% Yb3+ doping corresponds to the maximum photo-thermal responsivity (373 (K mm2)/W). The probable reason is that the high concentration of Yb3+ doping facilitates the absorption of 980 nm photons, but the long-distance energy transfer between Yb3+ suppresses the energy transfer from Yb3+ to Sm3+, thereby reducing the photo-thermal responsivity.

Long-Distance Resonant Energy Transfer Mediated by Hybrid Plasmonic–Photonic Modes

Metallic nanostructures are well known for their potential to enhance resonant energy transfer between chromophores, mediated by their plasmonic field. In most cases, the distances for efficient energy transfer are determined by the dimensions of the structure, making dissipation in the metal dominant when long-range energy transfer is desired. Here, we propose and study a new mechanism for long-distance energy transfer, which can lead to highly efficient energy transfer over distances comparable to the optical wavelength, based on hybrid photonic–plasmonic modes in metal-dielectric structures. We study such structures theoretically and characterize the energy-transfer processes in them, showing that within these structures, energy can be funneled with ∼25% efficiency over a range of about 150 nm, with minimal dependence on the location of the acceptor molecules inside the structure. Finally, we demonstrate this new mechanism experimentally, providing a proof-of-concept for long-distance energy transfer i...

On the Existence of Excitonic Signatures in the Optical Response of Metal-Organic Frameworks: Comment on "van der Waals Metal-Organic Framework as an Excitonic Material for Advanced Photonics".

In a recent experimental paper, it was claimed that pronounced excitonic signatures are observed in optical response of Zn-based metal-organic frameworks (MOFs) at room temperature. Performing ab initio modelling, it is demonstrated that an alternative interpretation based on single-electron optical transitions between narrow π-bands in the system of aromatic rings of the ligand is far more plausible. Although these results do not rule the possibility of exciton formation in MOFs out completely, they show that extreme caution should be taken in attributing the features in photoabsorption spectra alone to excitons, and additional proof, such as data on long-distance energy transfer, is necessary.

Is the AChR a Cuckoo-Clock? Local and Remote Interactions of the α M2-3 Linker in Gating

The αM2-3 linker of pentameric ligand-gated ion channels (18-residues in AChRs) is at the interface of the extracellular and transmembrane domains, which twist relative to each other early in the channel-opening process (phi∼0.7). Phi-analyses of mouse muscle AChRs indicate that residues in this linker and those at the transmitter binding sites share a common, even-earlier position in the gating transition state (phi∼0.9). To understand the mechanism for the similar behavior of these two separated regions (∼30 Å), whose combined motions appear to trigger channel-opening, we used single-channel free-energy mutant cycle analyses (A-A pairs) to measure the extents to which α-subunit linker residues (265-268) interact with other amino acids. The significant interactions (>0.5 kcal/mol) were as follows (n pairs tested; energies in kcal/mol): i) αloop2 (7), αE45-αP265 ∼+3.5 (positive is unfavorable); ii) αcys-loop (2), αV132-αS268 ∼+1; iii) agonist sites (3), αS268 and αY93 or αY198 showed no coupling but the interaction with αY190 was ∼-1.2 (favorable); iv) intra-linker (4), no significant coupling; v) εloop9 (6), εG183-αS268 and εG183-αT267 ∼+1.4; vi) εpre-M1 (1), εL221-αT267, no coupling. The large, unfavorable interaction between αP265 and its loop 2 neighbor αE45 (∼5 Å separation in GLIC) suggests that these side chains share a common energetic environment that is perturbed by the gating conformational change (twist). The long-distance, favorable interaction between αS268A in the linker and αY190A at the agonist site is more surprising. We hope to elucidate a network of apposed residues whose shared energy changes might be associated with the twist. More importantly, we are exploring the possibility that there is a long-distance energy transfer between the agonist binding site and transmembrane domain via the backbone that is not by a cuckoo-clock-like mechanical linkage.

Long-distance energy transfer photosensitizers arising in hybrid nanoparticles leading to fluorescence emission and singlet oxygen luminescence quenching

This paper presents energy transfer occurring in small organically modified core-shell nanoparticles (core lanthanide oxide, shell polysiloxane) (diameter < 10 nm) conjugated with photosensitizers designed for photodynamic therapy applications. These nanoparticles covalently encapsulate a photosensitizing PDT drug in different concentrations. Stable dispersions of the nanoparticles were prepared and the photophysical properties of the photosensitizers were studied and compared to those of the photosensitizers in solution. Increasing the photosensitizer concentration in the nanoparticles was not found to cause any changes in the absorption properties while fluorescence and singlet oxygen quantum yields decreased. As a possible explanation, we have suggested that both long distance energy transfer such as FRET and self-quenching could occur into the nanoparticles. A simple "trend" model of this kind of energy transfer complies with results of experiments on steady state fluorescence and singlet oxygen luminescence.

Integration of Catalysis with Storage for the Design of Multi-Electron Photochemistry Devices for Solar Fuel

Decarbonization of the transport system and a transition to a new diversified energy system that is scalable and sustainable, requires a widespread implementation of carbon-neutral fuels. In biomimetic supramolecular nanoreactors for solar-to-fuel conversion, water-splitting catalysts can be coupled to photochemical units to form complex electrochemical nanostructures, based on a systems integration approach and guided by magnetic resonance knowledge of the operating principles of biological photosynthesis, to bridge between long-distance energy transfer on the short time scale of fluorescence, ~10−9 s, and short-distance proton-coupled electron transfer and storage on the much longer time scale of catalysis, ~10−3 s. A modular approach allows for the design of nanostructured optimized topologies with a tunneling bridge for the integration of storage with catalysis and optimization of proton chemical potentials, to mimic proton-coupled electron transfer processes in photosystem II and hydrogenase.

A chemical approach toward photosynthetic reaction center

Abstract

Kinetics of partly diffusion controlled reactions XXII: Competition between long-distance energy transfer and collision quenching — first results

In the case of immunological assays, it is possible to use molecular emission spectroscopy techniques based on long-distance electronic energy transfer occurring between different fluorescent donors and acceptors, located in different proteins. Moreover, the same type of transfer can occur with the same protein between identical chromophores, which can modify the sensitivity of the titration. To check that these two types of transfer exist, we have developed a fluorescence quenching technique based on reactions partially controlled by molecular transport phenomena. We have shown that in fact this is the case, and our experimental results are consistent with the kinetics model developed, which is based on coupling between long-distance energy transfer and diffusional quenching. When the quenching of an electronically excited donor occurs through a time-dependent process, the excitation of the donor chromophore by long-distance energy transfer is in fact at the origin of the system re-initialization, which, in the case of diffusion-controlled reactions, implies an apparent increase in the quenching rate. The model we developed takes into account this re-initialization step and has been experimentally checked by adding a variable number of fluorescein molecules to the same protein followed by studying the fluorescence quenching by iodide ions.