Investigation Of Energy Transfer Research Articles

Microwave analogy of Förster resonance energy transfer and effect of finite antenna length

The near-field interaction between quantum emitters, governed by Förster resonance energy transfer (FRET), plays a pivotal role in nanoscale energy transfer mechanisms. However, FRET measurements in the optical regime are challenging as they require nanoscale control of the position and orientation of the emitters. To overcome these challenges, microwave measurements were proposed for enhanced spatial resolution and precise orientation control. However, unlike in optical systems for which the dipole can be taken to be infinitesimal in size, the finite size of microwave antennas can affect energy transfer measurements, especially at short distances. This highlights the necessity to consider the finite antenna length to obtain accurate results. In this study, we advance the understanding of dipole–dipole energy transfer in the microwave regime by developing an analytical model that explicitly considers finite antennas. Unlike previous works, our model calculates the mutual impedance of finite-length thin-wire dipole antennas without assuming a uniform current distribution. We validate our analytical model through experiments investigating energy transfer between antennas placed adjacent to a perfect electric conductor mirror. This allows us to provide clear guidelines for designing microwave experiments, distinguishing conditions where finite-size effects can be neglected and where they must be taken into account. Our study not only contributes to the fundamental physics of energy transfer but also opens avenues for microwave antenna impedance-based measurements to complement optical FRET experiments and quantitatively explore dipole–dipole energy transfer in a wider range of conditions.

A Quantum Algorithm from Response Theory: Digital Quantum Simulation of Two-Dimensional Electronic Spectroscopy.

Multidimensional optical spectroscopies are powerful techniques to investigate energy transfer pathways in natural and artificial systems. Because of the high information content of the spectra, numerical simulations of the optical response are of primary importance to assist the interpretation of spectral features. However, the increasing complexity of the investigated systems and their quantum dynamics call for the development of novel simulation strategies. In this work, we consider using digital quantum computers. By combining quantum dynamical simulation and nonlinear response theory, we present a quantum algorithm for computing the optical response of molecular systems. The quantum advantage stems from the efficient quantum simulation of the dynamics governed by the molecular Hamiltonian, and it is demonstrated by explicitly considering exciton-vibrational coupling. The protocol is tested on a near-term quantum device, providing the digital quantum simulation of the linear and nonlinear response of simple molecular models.

Signature of Quantum Coherence in the Exciton Energy Pathways of the LH2 Photosynthetic Complex.

Unraveling the energy transfer pathways in photosynthetic complexes is an important step toward understanding their structure-function interplay. Here, we use an open quantum systems approach to investigate energy transfer within the LH2 photosynthetic apparatus and its dependence on environmental conditions. We find that energy transfer pathways strongly depend on the environment-induced dephasing time. A comparison between the computational results and experiments performed on similar systems demonstrates that quantum coherences are present in these systems under physiological conditions and have an important role in shaping the energy transfer pathways. Moreover, our calculations indicate that relatively simple spectroscopy experiments can be used to detect traces of quantum coherence. Finally, our results suggest that quantum coherence may play a role in photosynthesis, but not in enhancing the efficiency as was previously suggested.

Molecular-Doped Protein-Based Elastomers as a Versatile Platform for Energy-Transfer Studies and Emissive Down-Converting Polymers for Light-Emitting Applications.

Much effort is being employed for designing "green" environmental emissive materials that are capable of color-tuning, i.e., down-converting the emission, and white-light generation (WLG). Here, we introduce a protein-based elastomer that can noncovalently bind a variety of chromophores while preventing their aggregation. Such binding capabilities are unique to the albumin-based materials that we use here in a process we refer to as "molecular doping". In the first part of this study, we explore the energy transfer across five different chromophores within the protein matrix, where the closely packed chromophore organization enables high energy-transfer efficiencies among them. In the second part, we show the easy control of blue, green, and red chromophores within the biopolymer, resulting in tunable emission properties of the film and WLG. The highly affordable chosen protein and the straightforward molecular doping strategy make our protein elastomers an attractive choice for an emissive material, as either a scaffold for investigating energy transfer in proteins or possible integration in light-emitting applications.

Research on NCFCP compact broadband NIR detector imaging and energy transfer function.

Nonlinear crystal frequency conversion imaging with direct detection by silicon-based detectors is an effective way to break through the limitations for existing near-infrared (NIR) detectors with expensive cost and high noise. In this paper, a broadband NIR detector imaging scheme based on the principle of nonlinear crystal frequency conversion (NCFCP) was proposed. A thin film of nonlinear crystal frequency conversion material (NCFCM) combined with a silicon-based detector was used to form a broadband NIR detector. The theoretically investigated energy transfer function was used as a guidance for experiment. Meanwhile, the relationship between the imaging effect and the energy transfer of the NCFCP-based compact broadband NIR detector in the NIR band was measured experimentally. The accuracy of the theoretical study had been verified by the measured transfer results.

Effect of protein matrix on CP29 spectra and energy transfer pathways

We investigate energy transfer pathways between strongly coupled chlorophylls (Chls) in the CP29 (LHCII B4.1) antenna complex of Pisum sativum, including the possibility of higher energy states. We test for the environmental effects caused by the protein, membrane and solvent using a hybrid QM/MM approach. Classical molecular dynamics simulations of the full CP29 complex embedded in a DOPC membrane have been performed, followed by calculations of the time dependent DFT spectra of all Chls at several timesteps. The relative orientations of transition dipole moments (TDMs) were specifically analyzed, including and excluding the point charge field (PCF) of the surrounding environment.The PCF is found to drastically shift the spectra of specific Chls, while the majority of Chls is mostly unaffected. The net effect on the sum spectrum is however found to be negligible: The few strong changes in Chl spectra cancel each other due to being opposite in sign. We further find that the spectra of the Chls coordinating to water show a blue shift upon introduction of the environment. Conversely, the spectra of the Chls coordinating to glutamine show a red shift upon activation of the PCF.As the main influence of the PCF for tuning the couplings, we identify the energetic position of the individual chromophores. The fine-tuning, especially for states energetically above the Qy state, is however controlled by the changes in the TDM orientations. We also find an indication for the PCF to steer potentially harmful high energy excitations away from the PSII core complex.

Tuning and Directing Energy Transfer in the Whole Visible Spectrum through Linker Installation in Metal-Organic Frameworks.

While limited choice of emissive organic linkers with systematic emission tunability presents a great challenge to investigate energy transfer (ET) over the whole visible light range with designable directions, luminescent metal-organic frameworks (LMOFs) may serve as an ideal platform for such study due to their tunable structure and composition. Herein, five Zr6 cluster-based LMOFs, HIAM-400X (X=0, 1, 2, 3, 4) are prepared using 2,1,3-benzothiadiazole and its derivative-based tetratopic carboxylic acids as organic linkers. The accessible unsaturated metal sites confer HIAM-400X as a pristine scaffold for linker installation. Six full-color emissive 2,1,3-benzothiadiazole and its derivative-based dicarboxylic acids (L) were successfully installed into HIAM-400X matrix to form HIAM-400X-L, in which the ET can be facilely tuned by controlling its direction, either from the inserted linkers to pristine MOFs or from the pristine MOFs to inserted linkers, and over the whole range of visible light. The combination of the pristine MOFs and the second linkers via linker installation creates a powerful two-dimensional space in tuning the emission via ET in LMOFs.

Tuning and Directing Energy Transfer in the Whole Visible Spectrum through Linker Installation in Metal–Organic Frameworks

AbstractWhile limited choice of emissive organic linkers with systematic emission tunability presents a great challenge to investigate energy transfer (ET) over the whole visible light range with designable directions, luminescent metal‐organic frameworks (LMOFs) may serve as an ideal platform for such study due to their tunable structure and composition. Herein, five Zr6 cluster‐based LMOFs, HIAM‐400X (X=0, 1, 2, 3, 4) are prepared using 2,1,3‐benzothiadiazole and its derivative‐based tetratopic carboxylic acids as organic linkers. The accessible unsaturated metal sites confer HIAM‐400X as a pristine scaffold for linker installation. Six full‐color emissive 2,1,3‐benzothiadiazole and its derivative‐based dicarboxylic acids (L) were successfully installed into HIAM‐400X matrix to form HIAM‐400X‐L, in which the ET can be facilely tuned by controlling its direction, either from the inserted linkers to pristine MOFs or from the pristine MOFs to inserted linkers, and over the whole range of visible light. The combination of the pristine MOFs and the second linkers via linker installation creates a powerful two‐dimensional space in tuning the emission via ET in LMOFs.

Whole-body energy transfer strategies during football instep kicking: implications for training practices

ABSTRACT Knowledge of whole-body energy transfer strategies during football instep kicking can help inform empirically grounded training practices. The aim of this study was thus to investigate energy transfer strategies of 15 semi-professional players performing kicks for speed and accuracy. Three-dimensional kinematics and GRFs (both 1000 Hz) were incorporated into segment power analyses to derive energy transfers between the support leg, torso, pelvis and kick leg throughout the kick. Energy transferred from support leg (r = 0.62, P = 0.013) and torso (r = 0.54, P = 0.016) into the pelvis during tension arc formation and leg cocking was redistributed to the kick leg during the downswing (r = 0.76, P < 0.001) and were associated with faster foot velocities at ball contact. This highlights whole-body function during instep kicking. Of particular importance were: (a) regulating support leg energy absorption, (b) eccentric formation and concentric release of a ‘tension arc’ between the torso and kicking hip, and (c) coordinated proximal to distal sequencing of the kick leg. Resistance exercises that replicate the demands of these interactions may help develop more powerful kicking motions and varying task and/or environmental constraints might facilitate development of adaptable energy transfer strategies.

Variations in Photoluminescence Intensity of a Quantum Dot Assembly Investigated by Its Adsorption on Cubic Metal–Organic Frameworks

In this study, a novel method is proposed for investigating energy transfer between quantum dots (QDs), especially of the same type, in an ensemble by employing cubic crystals of a commonly used metal–organic framework-5 (MOF-5). Three types of QDs were synthesized by standard methods and ligand-exchanged with weakly bound pyridine derivatives; thereafter, they were instantaneously adsorbed on MOF-5 in a monolayer by simply mixing both the materials. When two types of QDs were simultaneously loaded, energy transfer from the green- to red-emitting QDs as reflected by an increase in the photoluminescence (PL) intensity of the long-wavelength component was clearly observed. Conversely, when the same type of QDs were loaded on MOF-5, the increase in the PL intensity was lower than that expected corresponding to the amount of QDs and the deviation between the expected and measured values was different based on the type of QDs. These behaviors are discussed in relation to the occurrence of the Förster resonance energy transfer between the same species in close distance and the existence of temporarily or permanently dark QDs.

Vlasov simulation of electrons in the context of hybrid global models: an eVlasiator approach

Abstract. Modern investigations of dynamical space plasma systems such as magnetically complicated topologies within the Earth's magnetosphere make great use of supercomputer models as well as spacecraft observations. Space plasma simulations can be used to investigate energy transfer, acceleration, and plasma flows on both global and local scales. Simulation of global magnetospheric dynamics requires spatial and temporal scales currently achievable through magnetohydrodynamics or hybrid-kinetic simulations, which approximate electron dynamics as a charge-neutralizing fluid. We introduce a novel method for Vlasov-simulating electrons in the context of a hybrid-kinetic framework in order to examine the energization processes of magnetospheric electrons. Our extension of the Vlasiator hybrid-Vlasov code utilizes the global simulation dynamics of the hybrid method whilst modelling snapshots of electron dynamics on global spatial scales and temporal scales suitable for electron physics. Our eVlasiator model is shown to be stable both for single-cell and small-scale domains, and the solver successfully models Langmuir waves and Bernstein modes. We simulate a small test-case section of the near-Earth magnetotail plasma sheet region, reproducing a number of electron distribution function features found in spacecraft measurements.

On nonlinear energy flows in nonlinearly coupled oscillators with equal mass

Due to the near monopoly held by nonlinear energy sinks in the study of targeted energy transfer, little research has been done on the flow of mechanical energy between oscillators with comparable mass. The goal of the present paper is to investigate the flow of mechanical energy between two nonlinearly coupled oscillators with comparable mass that arise due to the breaking of dynamic reciprocity. The first oscillator represents the prototypical linear oscillator (LO), whereas the second oscillator represents a nonlinear oscillator (NO) that is nonlinearly coupled to the LO only. By breaking dynamic reciprocity, one-way energy propagation is achieved in the system, such that energy can only be irreversibly transferred from the NO to the LO. As such, the NO is isolated from the LO for physically reasonable energies whenever it is not directly excited. Moreover, when the NO is directly excited, there exist regimes where the LO, despite being linear and of comparable mass to the NO, behaves like a nonlinear energy sink and parasitically and irreversibly absorbs energy from the NO. The theoretical portion of this works employs direct numerical simulation of the structure to explore the strongly nonreciprocal dynamics and resulting energy transfers. The theoretical results are then verified through experimental measurements of a comparable structure. The present study promotes a new paradigm for investigating energy transfer in mechanical structures and opens the way for passively controlling the flow of energy in complex mechanical systems.

Femtosecond visible transient absorption spectroscopy of chlorophyll-f-containing photosystem II

The recently discovered, chlorophyll-f-containing, far-red photosystem II (FR-PSII) supports far-red light photosynthesis. Participation and kinetics of spectrally shifted far-red pigments are directly observable and separated from that of bulk chlorophyll-a We present an ultrafast transient absorption study of FR-PSII, investigating energy transfer and charge separation processes. Results show a rapid subpicosecond energy transfer from chlorophyll-a to the long-wavelength chlorophylls-f/d The data demonstrate the decay of an ∼720-nm negative feature on the picosecond-to-nanosecond timescales, coinciding with charge separation, secondary electron transfer, and stimulated emission decay. An ∼675-nm bleach attributed to the loss of chl-a absorption due to the formation of a cation radical, PD1+•, is only fully developed in the nanosecond spectra, indicating an unusually delayed formation. A major spectral feature on the nanosecond timescale at 725 nm is attributed to an electrochromic blue shift of a FR-chlorophyll among the reaction center pigments. These time-resolved observations provide direct experimental support for the model of Nürnberg et al. [D. J. Nürnberg et al., Science 360, 1210-1213 (2018)], in which the primary electron donor is a FR-chlorophyll and the secondary donor is chlorophyll-a (PD1 of the central chlorophyll pair). Efficient charge separation also occurs using selective excitation of long-wavelength chlorophylls-f/d, and the localization of the excited state on P720* points to a smaller (entropic) energy loss compared to conventional PSII, where the excited state is shared over all of the chlorin pigments. This has important repercussions on understanding the overall energetics of excitation energy transfer and charge separation reactions in FR-PSII.

Temperature induced emission enhancement and investigation of Nd3+→Yb3+ energy transfer efficiency in NaGdF4:Nd3+, Yb3+, Er3+ upconverting nanoparticles

Inorganic upconverting nanoparticles that can be excited with 808 nm laser radiation are gaining much attention recently. Living tissues, as well as water do not heat up as intensively when embedded upconverting nanoparticles are excited under such wavelength if compared to commonly used 980 nm laser radiation for excitation. To this end, a series of NaGd0.995-xYbxNd0.005F4 nanoparticles were synthesized in order to investigate energy transfer efficiency between Nd3+ and Yb3+ dopants under 808 nm laser excitation to better suit biological applications. The impact of Yb3+ concentration increase on crystal phase formation as well as downconversion (DC) properties was investigated. Temperature dependent luminescence measurements in NIR region revealed that no thermal quenching of Nd3+−Yb3+ pair in NaGdF4 system was observed in the entire 77–500 K temperature range. Finally, Er3+ ions were introduced in the investigated system in order to obtain multiple excitation and visualisation tool with performance in both VIS and NIR regions. The effective energy difference (ΔE) was also calculated from the thermally coupled levels (TCLs) of Er3+. The promising results and observations of synthesized compounds will be discussed, as NaGd0.475Yb0.5Er0.02Nd0.005F4 has a potential to be used as a luminescent temperature sensor.

Energy transfers between aerodynamic and acoustic fields in a rectangular impinging jet

Ventilation systems in buildings are of vital importance for the provision of acceptable thermal conditions and air quality while meeting stringent energy requirements. When a rectangular jet hits a slotted plate, an acoustic disturbance can be generated and self-sustained tones produced. Self-sustaining tones appear when a feedback loop develops between the surface of impact and the jet instabilities near to the jet exit. In order to control this phenomenon, more attention should be given to the source of energy that amplifies the resulting noise. Few studies have considered the fluctuation of the aerodynamic field using High Speed 3D Tomographic-PIV in the presence of self-sustaining tones. In this work, we investigate energy transfer between the aerodynamic and acoustic fields for different Reynolds numbers (Re=5294 and Re=5956) to better understand the noise generated by a rectangular jet impinging on a slotted plate. High Speed 3D Tomographic-PIV was performed at a sampling rate of 2 KHz and main flow vortices frequencies below 0.4 KHz. It was found that in the case of an optimal configuration for self-sustaining tones, the fluctuation of the Z-component of velocity presented higher amplitudes near the jet exit region.

C-N Bond Rotation Controls Photoinduced Electron Transfer in an Aminostyrene-Stilbene Donor-Acceptor System.

We investigate energy transfer and electron transfer in a dimethylsilylene-spaced aminostyrene-stilbene donor-acceptor dimer using time-dependent density functional theory calculations. Our results confirm that the vertical S3, S2, and S1 excited states are, respectively, a local excitation on the aminostyrene, local excitation on the stilbene, and the charge-transferred (CT) excited state with electron transfer from aminostyrene to stilbene. In addition, an energy minimum with the C-N bond of the amino group twisted at about 90° is also identified on the S1 potential energy surface. This S1 state exhibits a twisted intramolecular charge transfer (TICT) character. A potential energy scan along the C-N bond torsional angle reveals a conical intersection between the S2 stilbene local excitation and the S1 CT/TICT state at a torsional angle of ∼60°. We thus propose that the conical intersection dominates the electron transfer dynamics in the donor-acceptor dimer and copolymers alike, and the energy barrier along the C-N bond rotation controls the efficiency of such a process. Moreover, we show that despite the zero oscillator strength of the S1 excited states in the CT and TICT minima, an emissive S1 state with a V-shaped conformational structure can be located. The energy of this V-shape CT structure is thermally accessible; therefore, it is expected to be responsible for the CT emission band of the dimer observed in polar solvents. Our data provide a clear explanation of the complex solvent-dependent dual emission and photoinduced electron transfer properties observed experimentally in the dimer and copolymer systems. More importantly, the identifications of the conical intersection and energy barrier along the C-N bond rotation provide a novel synthetic route for controlling emissive properties and electron transfer dynamics in similar systems, which might be useful in the design of novel organic optoelectronic materials.

Investigation of Energy Transfer in Star-Shaped White Polymer Light-Emitting Devices via the Time-Resolved Photoluminescence.

A series of white polymer light-emitting devices (WPLEDs) were fabricated by utilizing star-shaped white-emission copolymers containing tri[1-phenylisoquinolinato-C2,N]iridium (Ir(piq)3), fluorenone (FO) and poly(9,9-dioctylfluorene) (PFO) as red-, green- and blue-emitting (RGB) components, respectively. In these WPLEDs, a maximum current efficiency of 6.4 cd·A−1 at 20 mA·cm−2 and Commission Internationale d’Eclairage (CIE) coordinates of (0.33, 0.32) were achieved, and the current efficiency was still kept to 4.2 cd·A−1 at the current density of 200 mA·cm−2. To investigate energy transfer processes among the three different chromophores of the star-shaped copolymers in these WPLEDs, the time-resolved photoluminescence (PL) spectra were recorded. By comparing the fluorescence decay lifetimes of PFO chromophores in the four star-like white-emitting copolymers, the efficient energy transfer from PFO units to Ir(piq)3 and FO chromophores was confirmed. From time-resolved PL and the analysis of energy transfer process, the results as follows were proved. Owing to the star-like molecular structure and steric hindrance effect, intermolecular interactions and concentrations quenching in the electroluminescence (EL) process could also be sufficiently suppressed. The efficient energy transfer also reduced intermolecular interactions’ contribution to the enhanced device performances compared to the linear single-polymer white-light systems. Moreover, saturated stable white emission results from the joint of energy transfer and trap-assisted recombination. This improved performance is expected to provide the star-like white-emitting copolymers with promising applications for WPLEDs.

Broadband-sensitive upconversion emission of Er,Ni,Nb-codoped Gd3Ga5O12 garnet

We synthesized Gd3Ga5O12 garnet codoped with Er, Ni, and Nb to realize transparent ceramics of broadband-sensitive upconverters used for crystalline silicon solar cells. We investigated energy transfer between the Er3+ and Ni2+ dopants using time-resolved measurements of both Ni2+ and Er3+ emissions. Most of the Ni2+ dopants occupied the six-coordinated Ga sites in the synthesized powder samples. Under 1.1–1.45 µm excitation, energies absorbed by the six-coordinated Ni2+ sensitizers almost perfectly transferred to the Er3+ emitters, leading to upconversion (UC) emission of the Er3+ at 0.98 µm. Combined with the UC emission directly excited at 1.45–1.65 µm, a broad sensitivity range of 1.1–1.65 µm was realized. However, the internal quantum efficiency of the UC emission was lower than that of previously developed La(Ga0.5Sc0.5)O3:Er,Ni,Nb, most likely owing to energy dissipation to a small amount of the Ni2+ dopants locating at the four-coordinated Ga sites. To improve the UC performance, the four-coordinated Ni2+ should be eliminated.

Direct Numerical Simulations to Investigate Energy Transfer between Meso- and Synoptic Scales

Abstract Understanding the development of the atmospheric energy spectrum across scales is necessary to elucidate atmospheric predictability. In this manuscript, the authors investigate energy transfer between the synoptic scale and the mesoscale using direct numerical simulations (DNSs) of two-dimensional (2D) turbulence transfer under forcing applied at different scales. First, DNS results forced by a single kinetic energy source at large scales show that the energy spectra slopes of the direct enstrophy cascade are steeper than the theoretically predicted −3 slope. Second, the presence of two inertial ranges in 2D turbulence at intermediate scales is investigated by introducing a second energy source in the meso-α-scale range. The energy spectra for the DNS with two kinetic energy sources exhibit flatter slopes that are closer to −3, consistent with the observed kinetic energy spectra of horizontal winds in the atmosphere at synoptic scales. Further, the results are independent of model resolution and scale separation between the two energy sources, with a robust transition region between the lower synoptic and the upper meso-α scales in agreement with classical observations in the upper troposphere. These results suggest the existence of a mesoscale feedback on synoptic-scale predictability that emerges from the concurrence of the direct (downscale) enstrophy transfer in the synoptic scales and the inverse (upscale) kinetic energy transfer from the mesoscale to the synoptic scale in the troposphere.

Yb3+ concentration influences UV–Vis to NIR energy conversion in nanostructured Pr3+ and Yb3+ co-doped SiO2-Nb2O5 materials for photonics

We describe the synthesis of Pr3+/Yb3+ co-doped and Pr3+-doped SiO2-Nb2O5 nanocomposites; we also investigate energy transfer processes between the doping ions, which involve UV–Vis to infrared energy conversion. The emission spectra in the near infrared (NIR) region, 900–1650 nm, indicated energy transfer from Pr3+ to Yb3+ upon blue excitation of the Pr3+ ions. UV charge transfer band excitation elicited efficient Yb3+ emission at about 1.0 µm. The nanocomposite co-doped with 0.5 mol% Pr3+ and 1.0 mol% Yb3+ provided maximum energy transfer efficiency. The Pr3+ ion 3P0 excited state lifetime decreased from 11.8 to 3.7 µs as the Yb3+ ion content in the Yb3+/Pr3+ co-doped nanocomposites increased from 0.25 to 1.0 mol%. This observation attests for energy transfer from Pr3+ to Yb3+ ions. On the basis of these results, Pr3+/Yb3+ co-doped SiO2-Nb2O5 nanocomposites are promising materials for UV–Vis to NIR energy conversion.