Energy Transfer Phenomenon Research Articles

The physics of energy transfer toward improved subgrid-scale models

Starting from physical insight on the energy transfer phenomena in wall turbulent flows, it is shown how modeling of subgrid stresses in large-eddy simulations can be improved. Each model should aim at reproducing the double feature of energy sink and source of the small scales of wall flows which become relevant when large filter lengths are considered. Here we propose one possible choice where the main ingredient is the coupling of the classical linear formulation of eddy viscosity with the nonlinear anisotropic features of the velocity increments tensor. This approach, which actually presents most of the features of the mixed models, captures the near-wall dynamics for very large filter lengths reproducing the small scales source physics responsible for backward energy transfer. A posteriori tests show excellent agreement with direct numerical simulation of turbulent channel flows even when very coarse grids are considered. The capability of the balance of the filtered second order structure function as a post-processing tool to evaluate the physics of any model is also shown.

Application of phasor plot and autofluorescence correction for study of heterogeneous cell population.

Protein-protein interactions in cells are often studied using fluorescence resonance energy transfer (FRET) phenomenon by fluorescence lifetime imaging microscopy (FLIM). Here, we demonstrate approaches to the quantitative analysis of FRET in cell population in a case complicated by a highly heterogeneous donor expression, multiexponential donor lifetime, large contribution of cell autofluorescence, and significant presence of unquenched donor molecules that do not interact with the acceptor due to low affinity of donor-acceptor binding. We applied a multifrequency phasor plot to visualize FRET FLIM data, developed a method for lifetime background correction, and performed a detailed time-resolved analysis using a biexponential model. These approaches were applied to study the interaction between the Toll Interleukin-1 receptor (TIR) domain of Toll-like receptor 4 (TLR4) and the decoy peptide 4BB. TLR4 was fused to Cerulean fluorescent protein (Cer) and 4BB peptide was labeled with Bodipy TMRX (BTX). Phasor displays for multifrequency FLIM data are presented. The analytical procedure for lifetime background correction is described and the effect of correction on FLIM data is demonstrated. The absolute FRET efficiency was determined based on the phasor plot display and multifrequency FLIM data analysis. The binding affinity between TLR4-Cer (donor) and decoy peptide 4BB-BTX (acceptor) was estimated in a heterogeneous HeLa cell population.

Quantum Langevin equation approach to electromagnetic energy transfer between dielectric bodies in an inhomogeneous environment

Near-field and resonance effects have a strong influence on nanoscale electromagnetic energy transfer, and detailed understanding of these effects is required for the design of new, optimized nano-optical devices. We provide a comprehensive microscopic view of electromagnetic energy transfer phenomena by introducing quantum Langevin heat baths as local noise sources in the equations of motion for the thermally fluctuating electric dipoles forming dielectric bodies. The theory is, in a sense, the microscopic generalization of the well-known fluctuational electrodynamics theory and thereby provides an alternative and conceptually simple way to calculate the local emission and absorption rates from the local Langevin bath currents. We apply the model to study energy transfer between silicon carbide nanoparticles located in a microcavity formed of two mirrors and next to a surface supporting propagating surface modes. The results show that the heat current between dipoles placed in a cavity oscillates as a function of their position and separation and can be enhanced by several orders of magnitude as compared to the free-space heat current with a similar interparticle distance. The predicted enhancement can be viewed as a many-body generalization of the well-known cavity Purcell effect. Similar effects are also observed in the interparticle heat transfer between dipoles located next to a surface of a polar material supporting surface phonon polaritons.

Organic–Inorganic Interface‐Induced Multi‐Fluorescence of MgO Nanocrystal Clusters and Their Applications in Cellular Imaging

Surface functionalization of inorganic nanomaterials through chemical binding of organic ligands on the surface unsaturated atoms, forming unique organic-inorganic interfaces, is a powerful approach for creating special functions for inorganic nanomaterials. Herein, we report the synthesis of hierarchical MgO nanocrystal clusters (NCs) with an organic-inorganic interface induced multi-fluorescence and their application as new alternative labels for cellular imaging. The synthetic method was established by a dissolution and regrowth process with the assistance of carboxylic acid, in which the as-prepared MgO NCs were modified with carboxylic groups at the coordinatively unsaturated atoms of the surface. By introducing acetic acid to partially replace oleic acid in the reaction, the optical absorption of the produced MgO NCs was progressively engineered from the UV to the visible region. Importantly, with wider and continuous absorption profile, those MgO NCs presented bright and tunable multicolor emissions from blue-violet to green and yellow, with the highest absolute quantum yield up to (33±1) %. The overlap for the energy levels of the inorganic-organic interface and low-coordinated states stimulated a unique fluorescence resonance energy transfer phenomenon. Considering the potential application in cellular imaging, such multi-fluorescent MgO NCs were further encapsulated with a silica shell to improve the water solubility and stability. As expected, the as-formed MgO@SiO2 NCs possessed great biocompatibility and high performance in cellular imaging.

Tracing photon transmission in dye-doped DNA-CTMA optical nanofibers

We experimentally demonstrate the novel phenomena of photoluminescence (PL) and fluorescence resonance energy transfer (FRET) assisted three-color PL separating in DNA optical nanofibers consisting of the stretched and connected DNA-cetyltrimethyl ammonium wires. The PL experiments are performed to comparatively trace photon transmission between single dye-doped DNA-CTMA optical nanofiber and PMMA optical nanofiber. A cascade FRET including DNA minor groove binder and DNA intercalators is used to further trace photon transmission inside DNA-CTMA wire. These experimental results will help to intrigue the new applications of DNA-CTMA as molecular waveguide in optobioelectronics area.

Nanosized complex fluorides based on Eu3+ doped Sr2LnF7 (Ln=La, Gd)

A simple co-precipitation approach taking place between Ln3+, Sr2+ cations and F− anions, led to the formation of nanocrystalline Eu3+ doped Sr2LnF7 (Ln=La and Gd) complex fluorides. The reaction was carried out in the presence of polyethylene glycol, PEG 6000 as a surfactant/surface modifier, providing small size and homogeneity of the products. The synthesized compounds were composed of small nanoparticles with an average size of 15 nm. All obtained Eu3+ doped compounds exhibited an intensive red luminescence. In the case of gadolinium based compounds, the energy transfer phenomena could be observed from Gd3+ ions to Eu3+ ions. In order to study the structure and morphology of the synthesized fluorides, powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements were performed. Also FT-IR spectra of the products were recorded, revealing the presence of PEG molecules on the nanoparticles surface. A spectrofluorometry technique was applied to examine optical properties of the synthesized nanoparticles. Excitation and emission spectra as well as luminescence decay curves were measured and analysed. The performed analysis revealed a red luminescence, typical for the Eu3+ ion situated in the inorganic, highly symmetric matrix. Concentration quenching phenomena and lifetimes shortening, together with an increasing of the Eu3+ doping level, were observed and discussed. Judd-Ofelt analysis was also performed for all doped samples, in order to support the registered spectroscopic data and examine in details structural and optoelectronic properties of the synthesized nanomaterials.

FRET (Fluorescence Resonance Energy Transfer), which is a phenomenon of energy transfer between two adjacent fluorescent molecules, has been applied to visualization of interaction between proteins in living cells and so on. To carry out high-efficiency F

Genes to CellsVolume 19, Issue 3 p. i-i Cover ImageFree Access FRET (Fluorescence Resonance Energy Transfer), which is a phenomenon of energy transfer between two adjacent fluorescent molecules, has been applied to visualization of interaction between proteins in living cells and so on. To carry out high-efficiency FRET, not only the distance between two molecules must be very close (less than about 10 nm) but the relative orientation of two chromophores must also be optimized. One of the women in this picture carries the other with attention paid on how they are oriented to each other, and successfully lightens the plum blossoms just like FRET. Designed by TRAIS Co., Ltd. (Kobe, Japan) First published: 24 February 2014 https://doi.org/10.1111/gtc.12141AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume19, Issue3March 2014Pages i-i RelatedInformation

Preparation and photophysical properties of luminescent nanoparticles based on lanthanide doped fluorides (LaF3:Ce3+, Gd3+, Eu3+), obtained in the presence of different surfactants

A series of nanomaterials composed of LaF3:Ce3+ 10%, Gd3+ 30%, Eu3+ 1% was synthesized via a facile co-precipitation approach. The reaction between appropriate lanthanide (Ln3+) and fluoride ions resulted in the formation of crystalline, Ln3+ doped fluorides and was performed in the presence of a series of organic modifiers, acting as surfactants and anti-agglomeration agents. Modifiers such as polyacrylic acid (PAA), ethylenediaminetetraacetic acid (EDTA), citric acid and oleylamine most significantly influenced the morphology and spectroscopic properties of the products. The product obtained in the presence of PAA was composed of the smallest nanoparticles (ca. 5–6nm), with narrow size/shape distribution. All fluorides synthesized exhibited intensive, bright red luminescence under UV irradiation (λex≈250nm), because of the presence of Eu3+ ions in their structure. The efficient intensity of luminescence was a result of indirect excitation, via energy transfer (ET) phenomena occurring in the system (Ce3+→Gd3+→Eu3+). The structure and morphology of the obtained nanomaterials were established by powder X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) measurements. Optical properties of the obtained compounds were studied and discussed on the basis of excitation emission spectra and luminescence decay curves. On the basis of the performed measurements, luminescence quantum yield (absolute and relative) and radiative lifetimes were calculated and analyzed. FT-IR spectroscopy was applied to examine the presence of molecules of the organic modifiers on the nanoparticles surface.

Homogeneous Fluorescence Resonance Energy Transfer Immunoassay for the Determination of Zearalenone

This study demonstrates the use of antigen-antibody binding for the detection of zearalenone. Based on the principle of the fluorescence resonance energy transfer (FRET) phenomenon between antibody and antigen, an immunoassay, in which zearalenone coupled with the anti-zearalenone antibody, was developed, optimized, and applied. Owing to intrinsic fluorescence properties in basic pH conditions with the optimal cationic surfactant, anti-zearalenone and zearalenone played roles as the respective donor and acceptor in the FRET immunoassay. As the concentration of analyte increased, the antigen/antibody emission intensity ratio (I 430 nm/I 350 nm) was enhanced due to larger amounts of zearalenone/anti-zearalenone complexes. This assay, based on the ratio of intensities (I 430 nm/I 350 nm), displayed high specificity and sensitivity with a detection limit of 0.8 ng mL−1 for zearalenone. The results obtained from analysis of spiked wheat grain samples were found to be in good agreement with those obtained by employing a direct competitive enzyme-linked immunosorbent assay. The label-free, noncompetitive, and homogeneous FRET immunoassay strategy served as a powerful tool for the simple, rapid, and sensitive quantitative determination of zearalenone in food and feed matrices.

Photophysical studies of an encapsulated neutral guest intercalated into the 2-dimensional space of α-Zr(iv) phosphate

Our long-range objective of developing surface anchored supramolecular assemblies as artificial light harvesting systems led us to explore the intercalation of guest molecules confined within octaamine hydrochloride (OAm·HCl) in the 2-dimensional galleries of layered inorganic material α-Zr(IV)phosphate (α-ZrP). Photophysical properties of 4,4'-dimethylbenzil, camphorthione, 4,4'-dimethylstilbene, pyrene and coumarin-1 were used to probe the intercalation behavior of OAm capsules within the galleries of α-ZrP. (1)H NMR and emission spectral investigations suggested the inclusion of guests within OAm and also confirmed the stability of host-guest complexes under acidic conditions in water. Stirring guest encapsulated OAm capsule with exfoliated α-ZrP nanosheets resulted in intercalation of the host-guest assembly as a whole in the case of 4,4'-dimethylbenzil, camphorthione, and 4,4'-dimethylstilbene as guests. According to powder X-ray diffraction and emission data these capsules are stable in the galleries of α-ZrP. The fact that the capsules are stable and can be included in α-ZrP nanosheets opens up further opportunities to explore inclusion of two different capsules, one with a donor and the other with an acceptor, and study the energy and electron transfer phenomenon between neutral molecules in α-ZrP galleries.

MULTIMODE ANALYSIS AND PIC SIMULATION OF A METAL PBG CAVITY GYROTRON OSCILLATOR

This paper is devoted to the study of beam-wave interaction behavior of a 35 GHz photonic band gap (PBG) cavity gyrotron operating in a higher order TE3,4,1 mode. For the present gyrotron, PBG cavity is used instead of conventional tapered cylindrical cavity due to its promising feature of the mode selectivity. In order to observe beam-wave interaction behavior, multimode theory has been used for the PBG cavity operating at the fundamental harmonic mode. Results obtained from the analysis have been validated using a commercially available 3D PIC code. The energy and phase variations of electrons demonstrate the bunching mechanism as well as energy transfer phenomena. RF power output obtained from the analysis as well as PIC simulation is compared and is found in close agreement within 12%. More than 45 kW of stable RF power output is achieved in TE3,4,1 mode with ∼ 17% efficiency. The existence of competing modes has been considerably reduced, and the single mode operation of PBG cavity gyrotron has been achieved.

Enhanced single-molecule spectroscopy in highly confined optical fields: from λ/2-Fabry–Pérot resonators to plasmonic nano-antennas

While single-molecule fluorescence from emitters with high quantum efficiencies such as organic dye molecules can easily be detected by modern apparatus, many less efficient emission processes such as Raman scattering and metal luminescence require dramatic enhancement to exceed the single-particle detection limit. This enhancement can be achieved using resonant optical systems such as plasmonic particles or nanoantennas, the study of which has led to substantial progress in understanding the interaction of quantum emitters with their electromagnetic environment. This review is focused on the advances in measurement techniques and potential applications enabled by a deeper understanding of fundamental optical interaction processes occurring between single quantum systems on the nanoscale. While the affected phenomena are numerous, including molecular fluorescence and also exciton luminescence and Raman scattering, the interaction itself can often be described from a unified point of view. Starting from a single underlying model, this work elucidates the dramatic enhancement potential of plasmonic tips and nanoparticles and also the more deterministic influence of a Fabry-Pérot microresonator. With the extensive knowledge of the radiative behavior of a quantum system, insight can be gained into nonradiative factors as well, such as energy transfer phenomena or spatial and chemical configurations in single molecules.

Screening for protein kinase C ligands using fluorescence resonance energy transfer.

Protein kinase C (PKC) is correlated with cell signaling pathways and also receives attention as a therapeutic target for cancer and Alzheimer-type dementia. The application of Förster/fluorescence resonance energy transfer (FRET) phenomena to detect binding between proteins and small molecules, for example, PKC and its ligands, underlies a fluorescence-based assay method suitable for high-throughput screening. To accelerate studies on PKC functions in processing signals using small molecules and the development of drugs that target PKC, novel methods for the assessment of the PKC binding affinity of compounds are necessary. We previously developed solvatochromic fluorophore-based methods for that assessment. In this study, a novel method for a FRET-based PKC binding assay was developed and is expected to overcome the limitations of solvatochromic fluorophores.

PIC simulation study of a 35 GHz, 200 kW Gyroklystron

A three-dimensional PIC simulation of a 35 GHz, 200 kW two cavity gyroklystron amplifier has been performed to study the electron beam and RF wave interaction behavior using a commercial PIC code 'MAGIC'. The electromagnetic field analysis of the RF structure in the absence of the electron beam and beam-wave interaction study in the presence of the electron beam have been carried out for the performance evaluation of the device. Electromagnetic field analysis has been done using the eigenmode solver, which ensures the structure operation in the desired TE01 operating mode at 35 GHz frequency. Electron beam and RF wave interaction simulation confirm that the present gyroklystron meet the required specification in terms of output power and gain. Moreover, the particles phase space behavior along the interaction length has been also demonstrated to realize the energy transfer phenomena. An output power around 200 kW at 34.95 GHz with ~35% efficiency and a bandwidth of 0.29% have been obtained considering no spread in electrons velocity. Our simulated result matches with the experimental values within 8%.

Ce decay curves in Ce, Tb co-doped LaF3 and the energy transfer mechanism

Energy transfer phenomena can play an important role in the development of luminescent materials, and hosts co-doped with Ce3+ and Tb3+ ions continue to be actively studied. Several recent reports on Ce, Tb co-doped phosphors suggest different mechanisms for the energy transfer from Ce3+ to Tb3+ ions and further study is required to reach consensus on the mechanism or to understand why different mechanisms dominate in different hosts. A more direct method of analysis is proposed to distinguish between the different types of multipole energy transfer mechanisms. When applied to Ce, Tb co-doped LaF3, the experimental data shows a poor match to any of these models but is consistent with energy transfer through the exchange mechanism. The decay curves of Ce emission in Ce, Tb co-doped LaF3 were also studied to obtain further insight on the energy transfer mechanism. Although the decrease in lifetime with increasing Tb concentration shows that energy transfer occurs through a non-radiative mechanism, the form of the decay curves does not correspond to what is expected for energy transfer via multipole interactions.

Study of the induration phenomena in single pellet to traveling grate furnace

The process for pelletizing iron ore fines is an important operation unit for producing high quality of raw materials for the subsequent reduction processes such as blast furnace or direct reduction. The process essentially involves production of green pellets and induration on a traveling grate furnace to promote inner partial melt and agglomeration that confers adequate physical and metallurgical properties. This work focuses on the phenomena that occur in the firing step aiming the construction of a mathematical model that describes each phase and chemical species. The model was formulated based on transport equations able to predict the evolution of the temperature profile inside the pellet for each zone on the induration furnace. It was taken into account coupled phenomena of momentum, energy and mass transfer between gas and particles within the agglomerates. The finite volume method was used to discretize the transport equations of momentum, mass and energy describing the behavior of a pellet in an industrial traveling grate furnace. Model results are shown for the temperature profile along the pellet radius during the residence time inside the furnace. In this context, in the present work i a tool was developed to optimize the thermal profile in the induration furnace and hence control the mechanical strength of the agglomerate.

Ho3+ ion in a (Ba, La)-tellurite glass: Strong ∼2.0 μm NIR emission and Yb3+ aided efficient NIR to vis upconversion

(Ba, La)-tellurite glasses doped respectively with only Yb3+, only Ho3+ and co-doped with (Yb3++Ho3+) have been prepared and their optical properties are studied. The experimental absorption and the emission spectra of the Ho3+ doped glass and calculations of its various Judd–Ofelt parameters, show that the Ho3+ ion in the glass has superior absorption and emission transition probabilities and higher emission rates and emission cross-sections. Similar spectroscopic studies on the Yb3+/Ho3+ co-doped – glass; on the other hand, demonstrate that the ∼2.0μm emission of Ho3+ of the glass can further be enhanced by phonon assisted non-resonance energy transfer from Yb3+. The derived emission cross-section spectrum of the 5I7→5I8 transition of Ho3+ of the glass and its related gain spectrum, indicate that the glass is prospective for use as a tunable solid state laser medium in this spectral region 1.972–2.053μm. Yb3+→Ho3+ energy transfer phenomenon also helps the Ho3+ ions of the co-doped glass to exhibit strong green (545nm) and red (600nm) upconversion emission upon excitation of its Yb3+ ions by 980nm laser. All the observed superior optical properties of Ho3+ ion in the glass have been explained in the light of crystal field effect of the host.

Study on honeysuckle active ingredients and comparative analysis on their interactive mechanisms with different proteins

To analyze and compare molecular mechanisms of active ingredients of honeysuckle (chlorogenic acid, CGA) with bovine lactoferrin (BLF) or bovine serum albumin (BSA). The spectral experiment and the computer analog technology were combined to determine the binding parameters, energy transfer parameters and thermodynamic functions between CGA and proteins, study the molecular mechanism, and compare the differences in interactive mechanism between CGA and BLF or BSA. The interactive mechanism between CGA and BLF or BSA was a dynamic molecular mechanism, whereas the static quenching mechanism existed between the interaction of CGA and BSA, with differences in the bonding intensity due to difference temperature. The binding distance r between CGA and BLF/BSA was very short, indicating the phenomenon of energy transfer. The results of the molecular modeling showed that the main interaction force between CGA and BLF or BSA was hydrogen bonds, together with Van der Waals' forces and hydrophobic effect. The computer analog shows consistent results with spectral experiment.

Optimization of energy transfer between quantum dots and gold nanoparticles in head-to-head configuration for detection of fusion gene

We report simultaneous detection of the variants 3a and 3b in the oncogenic EML4–ALK fusion gene using cDNA from lung cancer patients based on energy transfer between CdSe/ZnS quantum dots (QDs) and gold nanoparticles (AuNPs). To overcome the limitations of the conventional detection methods based on energy transfer, we have applied a head-to-head configuration of QDs and AuNPs. This allowed us not only to use longer probe oligonucleotides than the conventional methods, but also to optimize interparticle distance between QDs and AuNPs for maximum sensitivity and selectivity. By functionalizing two types of QDs (i.e., green- and red-emitting QDs) and 5nm AuNPs with probe oligonucleotides, we demonstrated that energy was selectively transferred from green-emitting QDs to AuNPs when variant 3a was present in target cDNA, or from red-emitting QDs to AuNPs with variant 3b, resulting in fluorescence quenching. Our method could successfully be used to simultaneously detect two variants of EML4–ALK fusion gene at the target DNA concentration (3.45nM) that was lower than the previously reported limit of detection values based on energy transfer phenomenon.

Internal energy transfer phenomenon and light-emission properties of γ-LiAlO2 phosphor doped with Mn2+

γ-LiAlO2:Mn2+ phosphor was synthesized using the cellulose-citric acid sol-gel method, and its light emission and energy transfer properties were investigated. Excitation and emission spectrum analysis revealed a decrease in intensity of the spectrum as the amount of Mn2+ doping increased. Blasse’s equation determined the maximum distance for energy transfer between Mn2+ ions as 4.3142 nm. Dexter’s theory verifies that the mechanism of energy transfer between Mn2+ ions conforms to an electric dipole and electric quadrupole interaction.