Nonradiative Excitation Energy Transfer Research Articles

Ligand-assisted excitation of Eu(III) during interaction of Eu(FOD)3 with xenon difluoride in acetonitrile solution

The interaction of tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedionato)europium(III), (Eu(FOD)3), with xenon difluoride in acetonitrile solution was found to be accompanied by chemiluminescence (CL). The kinetic curve of CL at a ratio of reagents Eu3+/XeF2 of 1:2 has a complex form; an initial rapid decrease is replaced by an increase in CL intensity, the maximum of which is reached approximately 10 min after the start of the reaction. Next, an exponential decay of the CL intensity is observed over several tens of minutes. The CL spectrum is located in the wavelength range 400–750 nm and corresponds to the emission of an electronically excited europium (III) ion coordinated with FOD and fluoride ion. Spectral methods were used to identify the reaction products – europium (III) fluoride in the sediment and oxygen difluoride in the gas phase. A mechanism for chemiexcitation of europium(III) has been proposed, including: 1) acceptance of fluorine anion from the XeF2 molecule by europium ion with the formation of active intermediate XeF+; 2) oxidative fluorination of the ligand, which is initiated by the interaction of oxygen atom of the FOD ligand with XeF+ cation and ends with the formation of oxygen difluoride and the electronically excited product P*, presumably a fluorinated ketone; 3) non-radiative transfer of excitation energy from P* to the europium ion within its coordination sphere, followed by its radiative deactivation.

The effect of polarity and hydrogen bonding on the electronic and vibrational structure of the salicylate anion in acetonitrile and water: implicit and explicit solvation approaches.

This study investigates the fluorescence quenching of the salicylate anion in water compared to acetonitrile (ACN) and the stability of its keto structure in ACN using DFT and TD-DFT methods at the 6-311++G(d,p) basis set. Computational simulations in implicit and explicit environments of ACN and water reveal the effects of solvent polarity and hydrogen bonding on enol [Od-H⋯Oa] and keto [Od⋯H-Oa] tautomerization, fluorescence quenching, and the spectral profile of the salicylate anion. Implicit solvation models show a barrier height of approximately 1.9 kcal mol-1 in ACN and 3.6 kcal mol-1 in water for enol-keto tautomerization in the ground state, with no barrier in the excited state, leading to an ESIPT reaction in both solvents, but only ground state proton transfer in ACN. Simulated absorption spectra for both enol and keto forms are similar in both solvents, while the emission spectrum is red-shifted in water. Explicit solvation studies indicate greater stabilization of the salicylate anion in water than in ACN, with a blue shift in absorption and emission spectra and varying oscillator strengths. Solvent molecule positioning affects enol-keto stabilization in the ground state, but only the keto structure is stabilized in the excited state. Simulated IR spectra in water show a blue shift in Od-H stretching frequency and increased water molecule vibrational frequencies, suggesting non-radiative excitation energy transfer from salicylate ions to water molecules via n → σ* intermolecular hydrogen bonding interactions. This mechanism explains the fluorescence quenching observed in water and results align with experimental data, indicating hydrogen-bonded keto form stabilization both in water and ACN.

Optical Properties of a Composite System with Nematic LC and Colloids Quantum Dots

Background: Optical luminescence in a composite system with nematic LC 4- octyloxy-4’-cyanobuphenyl (8OCB) and semiconductor quantum dots CdSe/CdS and CdSe/CdS/ZnS has been synthesized by a water-organic method. Methods: Composites have been investigated by means of polarizing microscopy, dynamic light scattering, and measurements of dielectric properties in the frequency range from 20 Hz to 5 MHz. The non-radiative excitation energy transfer from the liquid crystal molecules to the quantum dot in the LC-QD composite is detected by using the luminescence spectroscopy method. Results: This effect as well as the shift of the luminescence band is owing to components’ intermolecular interaction. Conclusion: The optimal concentration of QD in a composite that enhanced luminescence intensity was detected.

Effect of plasmonic-shell nanoparticles on the nonradiative transfer of electron excitation energy in donor/acceptor pairs

Effect of plasmonic-shell nanoparticles on the nonradiative transfer of electron excitation energy in donor/acceptor pairs

Dextran-graft-PNIPAM / Au nanoparticles / perylenediimide hybrid system as thermosensitive optical switches and fluorescent labels for potential use in nanophotonics and biomedical applications

A triple thermosensitive polymer Dextran-g-Poly(N-isopropylacrylamide)/Au nanoparticles/Perylenediimide (D-g-PNIPAM/AuNPs/PDI) hybrid nanosystem was formulated in aqueous solution for potential use as thermoresponsive fluorescent optical switch and label. The completely reversible effect of sharp enhancement-quenching of the photoluminescence of D-g-PNIPAM/AuNPs/PDI nanosystem was revealed during the heating-cooling cycle in the narrow temperature range of 25–47 °C, containing the temperature point of the LCST phase transition of the thermosensitive polymer. The sharp change in the intensity of photoluminescence was shown to result from the competing effects of plasmonic enhancement and non-radiative FRET transfer of electronic excitation energy during thermo-induced LCST transition of the D-g-PNIPAM macromolecule. The observed effect allows to carry out the temperature control of the photoluminescence intensity, which appears to be particularly important for potential applications of D-g-PNIPAM/AuNPs/PDI hybrid nanosystem in photonics, biology and medicine, such as thermosensitive fluorescent optical switch and label or intracellular fluorescent thermometer.

Template synthesis of luminescent oligoperoxide coated YBO3 nanoparticles doped with Ce3+, Tb3+ and Eu3+ ions

The template synthesis with different concentrations of heterofunctional oligoperoxide NVP-co-VEP-co-GMA (2-tert-butylperoxy-5-methyl-1-hexene-3-yne) was performed to obtain inorganic nanoparticles of controlled size. An increase of polymer concentration provides the decrease of nanoparticle size and polydispersity index. As a result of template synthesis, the polymer molecules were adsorbed unto the nanoparticle surface forming irreversibly attached functional shell protecting the nanoparticles from aggregation. Such the polymer coated nanoparticles showed significantly lower aggregation even after high-temperature annealing, which is necessary to increase their luminescence efficiency. The luminescence spectral-kinetic study of YBO3–Ce, YBO3–Ce, Tb and YBO3–Ce,Tb, Eu nanoparticles revealed an efficient nonradiative transfer of excitation energy from Ce to Tb ions in YBO3–Ce, Tb and from Ce to Tb to Eu in YBO3–Ce,Tb, Eu nanoscale host. The potential use of YBO3–Ce, YBO3–Ce, Tb and YBO3–Ce,Tb, Eu nanoparticles for biological imaging was demonstrated by the luminescence microscopy.

Плазмон-активированный фёрстеровский перенос энергии в молекулярных системах

To explain the experimentally observed effect of silver nanoparticles on the fluorescence of organic dyes and the nonradiative intermolecular transfer of electronic excitation energy in multilayer nanostructures, the previously proposed theoretical model of plasmon resonance in spherical nanoparticles of metals was used. The rates of radiative and nonradiative (FRET) processes in film structures with Ag nanoparticles were calculated for fluorescein and rhodamine B molecules, as well as for two-component systems fluorescein–nile red (NR) and rhodamine B–NR. A version of the model was used that takes into account the effect of NPs on FRET between molecules, the radiative decay of donor and acceptor molecules, and the energy transfer from the dye to plasmonic nanoparticles. The calculation of the UDA rate for pairs with different energy transfer efficiency showed a greater increase in the UDA parameter for the fluorescein–nile red pair than for the rhodamine B–nile red pair. Estimation of the fluorescence enhancement factor of donor and energy acceptor molecules and the rate of energy transfer from the dye to silver NPs showed their insignificant contribution to the formation of the resulting energy transfer efficiency enhancement in the presence of plasmonic NPs.

Влияние наноалмазов на усиление флуоресценции продуктов реакции фототрансформации триптофана в присутствии галогенуглеводородов

The role of nanodiamonds in the reaction of photochemical transformation of tryptophan in the presence of halogen hydrocarbons has been studied. The photochemical transformation of free tryptophan in a suspension with diamond nanoparticles and in a hybrid complex with them when exposed to UV radiation in the presence of chloroform is investigated. Data from stationary and time-resolved spectroscopic studies show the presence of non-radiative transfer of electron excitation energy between tryptophan molecules and its photodestruction products for the case of a covalent complex with a nanodiamond. It is shown that in the presence of energy transfer, an increase in the intensity of integral fluorescence occurs in the range of ~ 450 nm. Thus, a covalent tryptophan complex with a nanodiamond can serve as a fluorescent marker for the presence of chloroform in solution.

Влияние сферической наночастицы с металлической оболочкой на дезактивацию возбужденной квантовой точки

The plasmon-exciton interaction between a spherical nanoparticle with a dielectric core and a metal shell and a quantum dot in the mode of strong or weak confinement has been theoretically investigated. The rate of nonradiative transfer of electron excitation energy from a quantum dot to a nanoparticle and the rate of spontaneous emission of a quantum dot in the presence of a nanoparticle are calculated. It is shown that at the radii of the nanoparticle core, for which the frequency of the plasmon oscillation coincides with the frequency of the electronic transition in the quantum dot, the rates of radiative and nonradiative processes increase sharply. The kinetics of energy exchange between a nanoparticle and a quantum dot has been studied, and the values of the parameters of the system under consideration, at which the kinetics has the character of damped oscillations, have been established.

Plasmon-activated Forster energy transfer in molecular systems

To explain the experimentally observed effect of silver nanoparticles on the fluorescence of organic dyes and the nonradiative intermolecular transfer of electronic excitation energy in multilayer nanostructures, the previously proposed theoretical model of plasmon resonance in spherical nanoparticles of metals was used. The rates of radiative and nonradiative (FRET) processes in film structures with Ag nanoparticles were calculated for fluorescein and rhodamine B molecules, as well as for two-component systems fluorescein-nile red (NR) and rhodamine B-NR. A version of the model was used that takes into account the effect of NPs on FRET between molecules, the radiative decay of donor and acceptor molecules, and the energy transfer from the dye to plasmonic nanoparticles. The calculation of the UDA rate for pairs with different energy transfer efficiency showed a greater increase in the UDA parameter for the fluorescein-nile red pair than for the rhodamine B-nile red pair. Estimation of the fluorescence enhancement factor of donor and energy acceptor molecules and the rate of energy transfer from the dye to silver NPs showed their insignificant contribution to the formation of the resulting energy transfer efficiency enhancement in the presence of plasmonic NPs. Keywords: energy transfer, silver nanoparticles, plasmon, model

Effect of nanodiamonds on fluorescence enhancement of tryptophan phototransformation reaction products in the presence of halocarbons

The role of nanodiamonds in the reaction of photochemical transformation of tryptophan in the presence of halogen hydrocarbons has been studied. The photochemical transformation of free tryptophan in a suspension with diamond nanoparticles and in a hybrid complex with them when exposed to UV radiation in the presence of chloroform is investigated. Data from stationary and time-resolved spectroscopic studies show the presence of non-radiative transfer of electron excitation energy between tryptophan molecules and its photodestruction products for the case of a covalent complex with a nanodiamond. It is shown that in the presence of energy transfer, an increase in the intensity of integral fluorescence occurs in the range of ~ 450 nm. Thus, a covalent tryptophan complex with a nanodiamond can serve as a fluorescent marker for the presence of chloroform in solution. Keywords: nanoscale diamonds, hybrid complexes, tryptophan phototransformation, spectral-luminescent properties, fluorescence decay kinetics, chloroform.

Highly luminescent nanocomposites of nematic liquid crystal and hybrid quantum dots CdSe/CdS with ZnS shell

This work is focused on synthesis of highly luminescent hybrid CdSe/CdS ”core/shell” quantum dots (QDs) with different core sizes and an additional ZnS shell. These quantum dots were doped into a nematic liquid crystal (NLC) phase to obtain new composites. According to the dielectric and femtosecond laser spectroscopy data, sizes of the QD cores and built-up additional ZnS shells are correlated with luminescence and dielectric characteristics of the ZhK-1282 and QD composites. With larger QD cores in the ZhK-1282, a decrease in dielectric relaxation frequency of the LC molecules rotating around their short axis is observed, same for the activation energy of this process. A shift to a shorter wavelength of the LC main luminescence peak and the strong luminescence quenching effect can be observed for the composites with the 2 nm QD cores. This effect is the result of nonradiative excitation energy transfer from LCs to QDs in the composite. The adhesion work values have been calculated for all the samples, alignment substances and substrates. Optimized homeotropic aligning layers with the best composite anchoring parameters have been selected both for normal glass and glass with a sputtered indium tin oxide (ITO) layer.

Sensitized Luminescence Kinetics as a Tool for Identification of Nonradiative Energy Transfer

A simple equation is proposed for calculating the sensitized luminescence kinetics of acceptors caused by nonradiative excitation energy transfer (Forster Resonance Energy Transfer (FRET)) from donors. As parameters, the equation includes the lifetimes of the donor and acceptor excited states and the experimental luminescence decay kinetics of donors in the presence of FRET. The equation does not specify a certain FRET mechanism. It is proposed to use this equation to fit the experimental sensitized luminescence kinetics in order to quantitatively confirm the existence of FRET between donor and acceptors.

Optical Properties of Nematic Liquid Crystal Composites with Semiconducting Quantum Dots

The synthetic route to obtain stable composites of liquid crystal ZhK-777 with semiconductor quantum dots CdSe/CdS and CdSe/CdS/ZnS has been proposed. The dependents of fluorescence intensity of the composites on size and concentration of used quantum dots has been established. The shift of the luminescence band and decrease of its intensity has been observed both for liquid crystal and quantum dots. This effect indicates that quantum dots interaction with liquid crystals caused by a nonradiative excitation energy transfer from liquid crystal molecules to quantum dots. The dielectric spectroscopy of ZhK-777 and composites revealed that doping with quantum dots results in change of molecular relaxation frequencies in composites.

Nonradiative energy transfer of electronic excitation between Tm3+ ions in Y2O3:Tm laser ceramics

The cross relaxation of Tm3+ ions (3H4→3F4, 3H6→3F4) in Y2O3:Tm laser ceramics was studied. This process significantly affects the creation of an inverse population between the 3F4 and 3H6 levels of Tm3+ ions in two-micron lasers when they are pumped to the 3H4 level by laser diodes with a wavelength of λexc~800 nm. The efficiency of the cross-relaxation process of Tm3+ ions (3H4→3F4, 3H6→3F4) was equal to 97% for Y2O3:Tm ceramics with the thulium concentration of 3 at.%.It was revealed that the nonradiative transfer of electron excitation energy by Tm3+ ions through cross-relaxation (3H4→3F4, 3H6→3F4) is due to the dipole-dipole mechanism. The interaction microparameter CDA was determined equal to 9.2∙10−39 cm6/s.

IR Luminescence of Polyfunctional Associates of Indocianine Green and Ag-=SUB=-2-=/SUB=-S Quantum Dots-=SUP=-*-=/SUP=-

In this work, manifestations of IR luminescence sensitization of Indocyanine Green during conjugation with colloidal Ag2S quantum dots with average size of 2.2 and 3.7 nm, passivated with thioglycolic acid molecules (Ag2S/TGA QDs) are studied using absorption and luminescence techniques. The possibility of enhancing luminescence in the dye monomer band (820 nm) under excitation of 660 nm by a factor of 6 in the presence of Ag2S/TGA QDs (2.2 nm) due to a decrease in the dye polymethine chain due movement via coordination interaction with quantum dots was demonstrated. The way to switch-over from the first therapeutic window of biological tissue transparency (NIR-I, 700-950 nm) to the second (NIR-II, 1000-1700 nm), based on sensitization of IR luminescence of Ag2S/TGA QDs with an average size of 3.7 nm in the region of 1040 nm due to of resonance non-radiative transfer of excitation energy from Ag2S/TGA (2.2 nm) QDs at 900 nm to Ag2S/TGA QDs (3.7 nm) via the J-aggregate of ICG dye, which acts as an exciton bridge.

Nonradiative Energy Transfer in “Colloidal Quantum Dot Nanocluster–Dye” Hybrid Nanostructures: Computer Experiment

A computer model of nonradiative electronic excitation energy transfer from nanoclusters of colloidal quantum dots of cadmium selenide to the meso-tetra(3-pyridyl)porphyrin molecule in hybrid nanostructures nanocluster–dye has been constructed and analyzed. The model uses the experimental luminescence and absorption spectra of quantum dots and the dye, takes into account heterogeneity of the properties of quantum dots in nanoclusters and the different location of the dye in the hybrid structure. It has been shown that, in the ideal case, due to such energy transfer, the intensity of the luminescent signal of the dye can be increased by five orders of magnitude. However, this value is significantly reduced due to nonluminescent particles, the presence of a protective ligand shell, a large size distribution of the particles, and the nonoptimal geometric structure of the hybrid system.

Luminescence decay characteristics of CdS quantum dots doped with europium ions

In the present paper, we present an analysis of the luminescence decays for colloidal quantum dots (QDs) with interfaces doped with Eu3+ ions of the corresponding thenoyltrifluoroacetone complexes. The luminescence decay features related to concentration and temperature effects are considered. The Stern-Volmer plots obtained at 300 and 77 K for the trap state luminescence of CdS:Eu3+ QDs show that the QD luminescence quenching is of a dynamic character with the Stern-Volmer constant being Kdyn=3.7⋅105 M−1. Non-radiative excitation energy transfer from the trap state luminescence centers in CdS quantum dots to Eu3+ ions is observed. In addition, the value of the quenching rate kdyn=2.37⋅1013s−1⋅M−1 indicates that the energy transfer process has a non-diffusive nature. This conclusion is supported by the effective quenching in a frozen solution at 77 K where there is no diffusion. For CdS/TGA QDs doped with europium ions, we observe a significant increase in the luminescence lifetime (from 190 μs to 346 μs) for the band peaked at about 615 nm as compared to the free Eu:TTA complex. We conclude that Eu3+ ions are incorporated into the QD interfaces.

Energy transfer in hybrid optoelectronic structures between perovskite nanocrystals and an organic matrix

Solution-processed hybrid perovskite materials are attracting considerable attention as active layers of solar cells and hybrid light-emitting diodes (LEDs). Introducing perovskite CsPbBr3 nanocrystals (NCs) into light-emitting polymer (MEH-PPV) matrix can improve the processability and stability of such hybrid LEDs. In this work we investigate experimentally and consider theoretically the nonradiative excitation energy transfer from perovskite CsPbBr3 NCs to organic conjugated polymer MEH-PPV matrix along with experimental investigation of optical properties of such MEH-PPV:CsPbBr3 hybrid thin film structures. The theoretical analysis is carried out based on the Förster theory. The relative photoluminescence (PL) intensity of the MEH-PPV matrix is calculated as a function of the embed CsPbBr3 NC concentration. The decrease of the PL intensity with the increase of the CsPbBr3 NC concentration is found both theoretically and experimentally. It was found that the PL decay obtained experimentally is stronger with respect to that found theoretically. The reasons for the quantitative distinctions between the experimental data and as a result of the theoretical consideration are discussed.

Luminescent Properties of Hybrid Nanostructures Based on Quantum Dots of CdS, Europium 1,3-Diketonate, and Methylene Blue Molecules

The luminescent properties of hybrid nanostructures constructed from colloidal quantum dots (QDs) of CdS passivated with thioglycolic acid, europium(III) tris(tenoyltrifluoroacetonate), and methylene blue dye molecules are studied. Spectral features typical for the formation of core/shell QDs of the CdS/CdS:Eu3+ type are found. It is noted that the adsorption of the europium complex at the QD interfaces and the formation of QDs of the CdS/TGA/Eu3+ are probable. Spectral patterns that reveal nonradiative energy transfer from the recombination luminescence centers of CdS QDs to the Eu3+ ions in the CdS/CdS:Eu3+ and CdS/TGA/Eu3+ structures are obtained. This is manifested in quenching the recombination luminescence of QDs and in the ignition of the intracentric luminescence of Eu3+, which enhance with an increase in the concentration of the europium complex. When such structures are combined with methylene blue molecules, the half-width of the absorption spectra is found to increase by 10–15% with an unchanged position of the absorption band maximum. With an increase in the concentration of methylene blue molecules, decreases in the intensity of the recombination luminescence band of CdS QDs at a wavelength of 530 nm and in the luminescence intensity of Eu3+ ions and simultaneously the rise up of the fluorescence of methylene blue at a wavelength of about 675 nm are observed. At the same time, a decrease in the luminescence lifetime of the bands of QDs and europium ions are observed. It is concluded that the nonradiative excitation energy transfer from both the recombination luminescence centers and Eu3+ ions to methylene blue molecules takes place.