Electronic Excitation Energy Transfer Research Articles

Photoluminescence Study of Undoped and Eu-Doped Alkali-Niobate Aluminosilicate Glasses and Glass-Ceramics

In this study, the photoluminescence (PL) behavior of two aluminosilicate glass series containing alkali-niobates ranging from 0.4 to 20 mol% was investigated. The glasses exhibit an intense visible emission centered at ~18,400 cm−1 for the peralkaline series and at higher energies (~19,300 cm−1) for the metaluminous glasses. However, the photoluminescence emission intensity varies significantly with the niobate content and the bulk chemistry. PL and fluorescence lifetime measurements indicate that the broad emission bands result from the overlap of different niobate populations, whose distribution changes with niobate content. The distinct PL behavior in the two glass series was related to the structural evolution of the niobate units upon niobium addition. An enhancement of the visible emission was observed for a higher fraction of distorted [NbO6] units. Eu-doping was carried out as a structural probe of the glass network, and also to determine if these glasses could be used as potential rare earth element (REE) activators. The crystal field strength around Eu ions is strongly dependent on the bulk chemistry and the niobate content. Furthermore, the peralkaline series showed energy transfer from the host [NbO6] to Eu3+, confirming the feasibility of exploring niobate glasses and glass-ceramics as lanthanide ion-activated luminescent materials. In addition, glass-ceramics (GCs) containing alkali-niobate phases with a perovskite-like structure were developed and studied to verify the optical performance of these materials. It was verified that the bulk chemistry influences crystallization behavior, and also the photoluminescence response. The transparent GC from the metaluminous series exhibits a quenching of the Eu3+ emission, whereas an enhanced emission intensity is observed for the peralkaline GC. The latter shows a strong excitation-dependent PL emission, suggesting energy transfer and migration of electronic excitation from one Eu population to another. Additionally, Eu3+ emissions arising from the D15 and D25 excited states were observed, highlighting the low phonon energy achievable in niobo-aluminosilicate hosts.

Spectral and conformational characteristics of phycocyanin associated with changes of medium pH.

C-phycocyanin (C-PC) is the main component of water-soluble light-harvesting complexes (phycobilisomes, PBS) of cyanobacteria. PBS are involved in the absorption of quantum energy and the transfer of electronic excitation energy to the photosystems. A specific environment of C-PC chromophoric groups is provided by the protein matrix structure including protein-protein contacts between different subunits. Registration of C-PC spectral characteristics and the fluorescence anisotropy decay have revealed a significant pH influence on the chromophore microenvironment: at pH 5.0, a chromophore is more significantly interacts with the solvent, whereas at pH 9.0 the chromophore microenvironment becomes more viscous. Conformations of chromophores and the C-PC protein matrix have been studied by Raman and infrared spectroscopy. A decrease in the medium pH results in changes in the secondary structure either the C-PC apoproteins and chromophores, the last one adopts a more folded conformation.

Nanoobjects for the Luminescence Determination of Fluoroquinolones

Fluoroquinolones are the most successful antibiotics, which also show antiviral and antitumor activity. The widespread use of fluoroquinolones in medicine, pharmaceutical chemistry, veterinary medicine and in animal, poultry, and fish feeds requires continuous improvement of methods for their determination in various samples. Sensitized fluorescence based on resonance electronic excitation energy transfer (RET) during the formation of chelates with terbium and europium ions is a promising and highly sensitive method for the determination of fluoroquinolones. This review analyzes the use of two types of nanoobjects—liquid micellar nanosystems and quantum dots based on the nanoparticles of silver, gold, and semiconductors and carbon, magnetic, and other nanomaterials—for increasing the efficiency of energy transfer and the sensitivity of the determination of fluoroquinolones in various samples. The terminology used in the inductive-resonance and exchange-resonance mechanisms of energy transfer is considered, and the fundamental difference in RET between liquid and solid types of nanoobjects is shown. Linear dynamic ranges of determined concentrations, limits of detection, and examples of practical application of sensitized fluorescence to the determination of fluoroquinolones in real samples with the use of nanoparticles and micellar nanosystems are tabulated.

Nanoobjects for the Luminescence Determination of Fluoroquinolones

Fluoroquinolones are the most successful antibiotics, which also show antiviral and antitumor activity. The widespread use of fluoroquinolones in medicine, pharmaceutical chemistry, veterinary medicine and in animal, poultry, and fish feeds requires continuous improvement of methods for their determination in various samples. Sensitized fluorescence based on resonance electronic excitation energy transfer (RET) during the formation of chelates with terbium and europium ions is a promising and highly sensitive method for the determination of fluoroquinolones. This review analyzes the use of two types of nanoobjects—liquid micellar nanosystems and quantum dots based on the nanoparticles of silver, gold, and semiconductors and carbon, magnetic, and other nanomaterials—for increasing the efficiency of energy transfer and the sensitivity of the determination of fluoroquinolones in various samples. The terminology used in the inductive-resonance and exchange-resonance mechanisms of energy transfer is considered, and the fundamental difference in RET between liquid and solid types of nanoobjects is shown. Linear dynamic ranges of determined concentrations, limits of detection, and examples of practical application of sensitized fluorescence to the determination of fluoroquinolones in real samples with the use of nanoparticles and micellar nanosystems are tabulated.

Surface crossing and energy flow in many-dimensional quantum systems

Energy flow in molecules, like the dynamics of other many-dimensional finite systems, involves quantum transport across a dense network of near-resonant states. For molecules in their electronic ground state, the network is ordinarily provided by anharmonic vibrational Fermi resonances. Surface crossing between different electronic states provides another route to chaotic motion and energy redistribution. We show that nonadiabatic coupling between electronic energy surfaces facilitates vibrational energy flow and, conversely, anharmonic vibrational couplings facilitate nonadiabatic electronic state mixing. A generalization of the Logan-Wolynes theory of quantum energy flow in many-dimensional Fermi resonance systems to the two-surface case gives a phase diagram describing the boundary between localized quantum dynamics and global energy flow. We explore these predictions and test them using a model inspired by the problem of electronic excitation energy transfer in the photosynthetic reaction center. Using an explicit numerical solution of the time-dependent Schrödinger equation for this ten-dimensional model, we find quite good agreement with the expectations from the approximate analytical theory.

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.

Förster Resonance Energy Transfer between Fluorescent Organic Semiconductors: Poly(9,9-dioctylfluorene-alt-benzothiadiazole) and 6,13-Bis(triisopropylsilylethynyl)pentacene

In the present study, an investigation of the electronic excitation energy transfer between two p-type fluorescent semiconductors, F8BT [poly(9,9-dioctylfluorene-alcohol-benzothiadiazole] and TIPS-P [6,13-bis(triisopropylsilylethynyl)pentacene], has been carried out in a chloroform solution using steady-state and time-domain fluorescence techniques. The spectral overlap integral between donor (F8BT) emission and acceptor (TIPS-P) absorption is 2.04 × 1015 nm4/(M cm), and the corresponding critical transfer distance is 53.12 Å. In donor decay dynamics, at the lower acceptor concentrations, the observed results deviate from the Förster theory due to the combined effect of diffusion and energy migration. However, it does not exhibit energy migration and distribution for higher acceptor concentrations, and the system follows the Förster model of resonance excitation energy transfer (FRET). The higher value of the donor-acceptor interaction strength than self-interaction (donor-donor interaction) appears to be responsible for this behavior. Further, in acceptor decay, the appearance of the rise time and its decrease with the acceptor concentration confirms FRET from F8BT to TIPS-P.

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.

Sensitized fluorescence and superluminescence of a dye in a functional chitosan–gelatin matrix

A method for the formation of a functional biopolymer matrix based on specific mixing of chitosan and gelatin is proposed. It makes it possible to obtain the binding complexes of organic dyes such as eosin (energy donor) and rhodamine C (acceptor) with chitosan that are advantageous for the realization of inductive-resonant electron excitation energy transfer between these dyes. An efficient sensitized steady-state fluorescence of rhodamine C and superluminescence of this dye under pulsed excitation were observed in this system. The obtained results can be used for the development of two-component solid-state dye lasers.

Influence of Lattice Fluctuation Disorder on the Thermally Induced Electron-Excitation Energy Transfer

Influence of Lattice Fluctuation Disorder on the Thermally Induced Electron-Excitation Energy Transfer

Energy transfer of intrinsic electronic excitation to impurities in the CaSO4 − Mn crystal

The nature of the impurity emission center and the energy transfer mechanisms from intrinsic electronic excitations to the Mn2+ impurity centers in the CaSO4 − Mn crystal have been investigated. The methods of vacuum ultraviolet, atomic absorption and luminescence spectroscopy are used in a wide temperature range from 5 K to 300 K. The energy transfer of intrinsic electronic excitations to impurity emission centers in CaSO4 − Mn has been detected.

Effect of logarithmic perturbations in ohmic like spectral densities in dynamics of electronic excitation using variational polaron transformation approach

Electronic excitation energy transfer is a ubiquitous process that has generated prime research interest since its discovery. Recently developed variational polaron transformation-based second-order master equation is capable of interpolating between Förster and Redfield limits with exceptional accuracy. Forms of spectral density functions studied so far through the variational approach provide theoretical support for various experiments. Recently introduced ohmic like spectral density function that can account for logarithmic perturbations provides generality and exposition to a unique and practical set of environments. In this paper, we exploit the energy transfer dynamics of a two-level system attached to an ohmic like spectral density function with logarithmic perturbations using a variational polaron transformed master equation. Our results demonstrate that even for a relatively large bath coupling strength, quantum coherence effects can be increased by introducing logarithmic perturbations of the order of one and two in super-ohmic environments. Moreover, for particular values of the ohmicity parameter, the effect of logarithmic perturbations is observed to be insignificant for the overall dynamics. In regard to ohmic environments, as logarithmic perturbations increase, damping characteristics of the coherent transient dynamics also increase in general. It is also shown that, having logarithmic perturbations of the order of one in an ohmic environment can result in a less efficient energy transfer for relatively larger system bath coupling strengths.

LaF3:Tb3+ − Bengal Rose nanocomplexes for X-ray activated ROS generation

Herein we report the creation of nanocomplexes on the base of scintillation nanoparticles (SNPs) LaF3:Tb3+ and organic photosensitizer Rose Bengal (RB) with an efficient electronic excitation energy transfer upon both UV-light and X-ray irradiation. In such LaF3:Tb3+ − RB complexes, SNPs act as an energy transducer absorbing high-energy photons and transferring them to the organic RB photosensitizer with subsequent singlet oxygen 1O2 generation for X-ray activated photodynamic therapy (PDT). For the first time, it has been shown that under X-ray irradiation LaF3:Tb3+ SNPs produce hydroxyl radicals ·OH via X-ray induced holes interactions with water molecules adsorbed at the surface of SNPs. Such extra-bonus of LaF3:Tb3+ SNPs can solve the problem of low efficiency of conventional PDT in hypoxic areas of the tumor, which suffer from the lack of oxygen molecules.

Chemiluminescence Detection in the Study of Free-Radical Reactions. Part 1.

The present review, consisting of two parts, considers the application of the chemiluminescence detection method in evaluating free radical reactions in biological model systems. The first part presents a classification of experimental biological model systems. Evidence favoring the use of chemiluminescence detection in the study of free radical reactions, along with similar methods of registering electromagnetic radiation as electron paramagnetic resonance, spectrophotometry, detection of infrared radiation (IR spectrometry), and chemical methods for assessing the end products of free radical reactions, is shown. Chemiluminescence accompanying free radical reactions involving lipids has been the extensively studied reaction. These reactions are one of the key causes of cell death by either apoptosis (activation of the cytochrome c complex with cardiolipin) or ferroptosis (induced by free ferrous ions). The concept of chemiluminescence quantum yield is also discussed in this article. The second part, which is to be published in the next issue, analyzes the application of chemiluminescence detection using luminescent additives that are called activators, a.k.a. chemiluminescence enhancers, and enhance the emission through the triplet–singlet transfer of electron excitation energy from radical reaction products, followed by light emission with a high quantum yield.

Радиолиз трансформаторного масла в присутствии трихлорбензола и нано--Al2O3

In this work, a comparative study of the kinetics of changes in the pH indicator, the formation of H2O2 and CO2 depending on the absorbed dose at the radiolysis of TCB containing transformer oil in the presence and without nano-γ-Al2O3 under the action of γ radiation was carried out. During radiolysis of both systems (TСB + transformer oil and TСB + transformer oil + 0.1 g of nano-γ-Al2O3), the radiation-chemical yield of CO2 decreases with an increase in the initial concentration of TCB, although at the presence of nano-particles, the values of the radiation-chemical riels of CO2 become less. Unlike CO2, the radiation-chemical yields of H2O2 increase with an increase in the initial concentration of TCB, but their values are less in the presence of nano-γ-Al2O3. The results obtained are explained by the reactions of active particles, radiolysis of the main components of transformer oil, such as hydrogen atoms and hydrocarbon radicals with TCB and dissolved oxygen molecules. In addition, there is a transfer of electronic excitation energy from alkane and cycloalkane molecules to aromatic hydrocarbon molecules. The effect of nano-γ-Al2O3 on the radiolysis of the mixture is discussed on the basis of the reaction of electron and hole centers with the molecules of the components of the irradiated mixture.