Phosphorescence Decay Research Articles

Kinetics study on reaction of atenolol with singlet oxygen by directly monitoring the 1O2 phosphorescence

The pharmaceutically active compound atenolol, a kind of β-blockers, may result in adverse effects both for human health and ecosystems if it is excreted to the surface water resources. To effectively remove atenolol in the environment, both direct and indirect photodegradation, driven by sunlight play an important role. Among indirect photodegradation, singlet oxygen (1O2), as a pivotal reactive species, is likely to determine the fates of atenolol. Nevertheless, the kinetic information on the reaction of atenolol with singlet oxygen has not been well investigated and the reaction rate constant is still ambiguous. Herein, the reaction rate constant of atenolol with singlet oxygen is investigated directly through observing the decay of the 1O2 phosphorescence at 1270 nm. It is determined that the reaction rate constant between atenolol and 1O2 is 7.0×105 (mol/L)−1·s−1 in D2O, 8.0×106 (mol/L)−1·s−1 in acetonitrile, and 8.4×105 (mol/L)−1·s−1 in EtOH, respectively. Furthermore, the solvent effects on the title reaction were also investigated. It is revealed that the solvents with strong polarity and weak hydrogen donating ability are suitable to achieve high rate constant values. These kinetics information on the reaction of atenolol with singlet oxygen may provide fundamental knowledge to the indirect photodegradation of β-blockers.

Люминесцентные свойства облученных электронами с энергией 12 MeV кристаллов шпинели MgO· 2.5Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-

The investigation of the luminescent properties of nonstoichiometric spinel compositions of MgO·2,5Al2O3 irradiated in direct and scattered beams of 12 MeV electrons on M-30 microtron are given. The phosphorescence decay kinetics of these compounds that occur after irradiation have been studied. It was found that the kinetics of induced luminescence can be described the Becquerel’s hyperbola. The degree parameter of this hyperbola is increased with increasing the dose of radiation. The regularities of the thermoluminescence peak change in the range of 110-250ºC with the dose are investigated. It is concluded that obtained results can be used for clinical and technological dosimetry of pulsed electron beams.

Design, Synthesis, and Evaluation of a Luminescent Cholesterol Mimic.

The development of new chemical tools with improved properties is essential to chemical and cell biology. Of particular interest is the development of mimics of small molecules with important cellular function that allow the direct observation of their trafficking in a cell. To this end, a novel 15-azasterol has been designed and synthesized as a luminescent cholesterol mimic for the monitoring of cholesterol trafficking. The brightness of this probe, which is ∼32-times greater than the widely used dehydroergosterol probe, is combined with resistance to photobleaching in solution and in human fibroblasts and an exceptionally large Stokes-like shift of ∼150-200 nm. The photophysical properties of the probe have been studied experimentally and computationally, suggesting an intersystem crossing to the triplet excited state with subsequent phosphorescent decay. Molecular dynamics simulations show a similar binding mode of cholesterol and the azasterol probe to NPC proteins, demonstrating the structural similarity of the probe to cholesterol.

Phosphorescent palladium-tetrabenzoporphyrin indicators for immunosensing of small molecules with a novel optical device

Small-molecule detection is important for many applications including clinical diagnostics, drug discovery, environmental screening, and food technology. Current techniques suffer from various limitations including cost, complex sample processing, massive instrumentation, and need for expertise. To overcome these limitations, a new optical immunosensing assay for the detection of small molecules was developed and assessed with the targets estrone (E1) and estradiol (E2). For this purpose, phosphorescent indicators were designed based on the tetrabenzoporphyrin skeleton directly linked to E1 or E2, or attached through a linker, with phosphorescence lifetimes in the range of ~100–~300 μs. The assay is an indicator displacement assay (IDA). The best performances of our optical immunosensor were obtained with the indicators E1-L-Por and E2-L-Por. As they bound to specific polyclonal antibodies, their phosphorescence (τ ~200 μs) was quenched. When an endogenous competitor was added, the indicator was displaced, and the phosphorescence was immediately recovered. These effects were measured with a new optical device, described here, and able to detect picograms of luminescent molecules emitting in the NIR range, simply by measuring phosphorescence decay. This radical switch-off/switch on process demonstrates that E1-L-Por and E2-L-Por are good candidates for in vivo and in vitro immunosensing of E1 and E2. Importantly, the present immunosensing assay can be easily adapted to other small molecules such as other hormones and drugs.

Oxygen sensing performance of biodegradable electrospun nanofibers: Influence of fiber composition and core-shell geometry

The ability to continuously monitor tissue oxygenation in vivo is highly desired for a variety of biomedical applications. Implantable optical oxygen sensors can be constructed through incorporation of an oxygen-sensitive chromophore within a biocompatible polymer host. In this work, a Pd (II) benzoporphyrin that absorbs (630 nm) and phosphoresces (810 nm) within the optical tissue window was incorporated into various biodegradable polymer matrices via electrospinning. A unique in situ fluorimeter setup was constructed and used to rigorously characterize the sensor performance in the physiologically relevant dissolved oxygen range (∼0−90 μM) in 37 °C phosphate buffered saline. Single-component polycaprolactone (PCL) fibers exhibited high sensitivity (KSV: 1.25 × 105 M−1) and monoexponential decay curves, indicating a homogenous chromophore environment. The ability to move from a single-component composition (PCL) to blended (PCL:gelatin) and core-shell systems (PCL:gelatin-PCL) without compromising the desirable properties of the single-component sensor was demonstrated. These variations may offer the potential to tune degradation time of the resulting sensor while maintaining high sensitivity and monoexponential decays. In contrast, blended 50:50 PCL:poly(d,l-lactide-co-glycolide) (PLGA) exhibited significantly reduced sensitivity (KSV: 6.66 × 104 M−1) and biexponential decays. Despite the observation of biexponential lifetime decays for PCL:PLGA, all electrospun sensors exhibited linear Stern-Volmer behavior over the physiologically relevant dissolved oxygen range. This work rigorously evaluated biodegradable candidates for in vivo oxygen sensing under physiologically relevant conditions in which the character of the individual phosphorescence decay curves offered insight into the nature of the chromophore environment.

Kinetics process of room temperature phosphorescence and fluorescence of gadolinium porphyrin in aqueous solution

The behavior of room temperature phosphorescence quenching and fluorescence enhancing of gadolinium labeled sinoporphyrin sodium (Gd-DVDMS) in the aqueous solution were studied. Gd-DVDMS was characterized by various techniques including mass spectra, Fourier transform infrared spectra and transmission electron microscopy. The optical behavior was monitored through UV–vis absorption spectra and photoluminescence spectra. The result shows that the phosphorescence intensity gradually quenches, almost disappears after dissolved 120 min, meanwhile the fluorescence intensity enhances 5 times. The above behavior is attributed to the decreased population of Gd-DVDMS as first excited triplet state (T1). Based on the time-invariant of both absorption spectra and phosphorescence decay curves at 710 nm of Gd-DVDMS in different dissolution time, the reason for the decreased population of Gd-DVDMS in T1 state is that the intersystem crossing from first excited state (S1) to T1 is prevented. In addition, the fluorescent decay curves of Gd-DVDMS initially dissolved in the aqueous solution and dissolved for 120 min were also measured for comparison. The big change in fluorescent lifetime further proves the conclusion that intersystem crossing is prevented, meanwhile, the increase in fluorescence intensity is demonstrated. In this work, the possibility of decomposition of Gd-DVDMS is excluded because the phosphorescence decay curve in Gd-DVDMS aqueous solution is sensible to DVDMS.

Некоторые особенности спектра и кинетики фосфоресценции трифенилена в бромбензоле при 77 К

The spectrum and kinetics of triphenylene phosphorescence under monochromatic and broadband excitation in bromobenzene at 77 K were studied. It was found that the intensity distribution in the phosphorescence spectrum depends on the spectral composition of the exciting light. In the transition from excitation by monochromatic radiation of a nitrogen laser ($\lambda_{ex} = 337$ nm) to broadband excitation by a high-pressure xenon lamp with a filter of 313 nm, a 0--0 band gain is observed relative to the most intense vibronic band of a half-symmetric oscillation ($\nu =1605$ cm$^{-1})$. In this case, a broadening of the 0--0 band and a shift of its maximum to the short-wave region by 1.8 nm are observed. The decay of triphenylene phosphorescence under these conditions is two-exponential with characteristic decay times $\tau_{1} = 0.40$ s and $\tau_{2} = 0.13$ s. The contribution of the component damping with $\tau_{1}$ to the total intensity increases with the allocation of the short-wave section of the 0--0 band. The contribution of the component damping with $\tau_{2}$ increases with the allocation of the long-wave portion of the 0-0 band. An increase in the contribution of the component with $\tau_{2}$ is also observed with monochromatic laser excitation in comparison with broadband excitation. Based on these results, it was concluded that there are two spatially separated emission centers with different probabilities of deactivation of triplet excitations of triphenylene molecules. The interpretation of the results is based on the generally accepted literature provisions that halogen atoms (chlorine, bromine, iodine) increase the probability of spin forbidden and symmetry transitions in highly symmetric molecules such as triphenylene (symmetry type D$_{3h})$ and coronene (symmetry type D$_{6h})$. Based on a comparison of changes in the relative intensity of the 0-0 band of centers with $\tau_{1}$ and $\tau_{2}$, it was concluded that external heavy atoms (bromine) to a greater extent enhance the symmetry-forbidden transitions of centers with $\tau_{1}$ than with $\tau_{2}$. The faster attenuation of the phosphorescence of centers with $\tau_{2}$ than of centers with $\tau_{1}$ is due to a greater degree to an increase in their triplet - singlet transition forbidden along the spin.

Novel white-emitting afterglow phosphor Na2CaSn2Ge3O12:Dy3+: Preparation, photoluminescence, and phosphorescence properties

Afterglow was found in germanate (Na2CaSn2Ge3O12) doped with Dy3+ phosphor, which was prepared at 1250 °C through the traditional solid-state reaction in air. Na2CaSn2Ge3O12:Dy3+ phosphors were comprehensively characterized by XRD, photoluminescence excitation and emission spectra, thermo-luminescence and long persistent phosphorescence decay curves to study the effects of the Dy3+ concentration on their properties. The XRD results indicates that a single phase of Na2CaSn2Ge3O12 can be obtained. Upon excitation by 248-nm UV light, all samples emit white light, which is composed of yellow and blue originating from the Dy3+ (4F9/2→6HH/2, H = 11, 13, 15 transition). The Na2CaSn2Ge3O12:Dy3+ phosphor exhibited the perfect luminescent property and longest afterglow time when the Dy3+ concentration was 0.6 mol%. The CIE chromaticity coordinates for Na2CaSn2Ge3O12:Dy3+ were (0.3916, 0.3914). From the long persistent phosphorescence decay curve of the Na2CaSn2Ge3O12:Dy3+ phosphor, it was concluded that this process contains a fast and a slow decay. The afterglow luminescence from the Na2CaSn2Ge3O12:Dy3+ phosphor persisted for more than 7.8 h after irradiation with ultraviolet lamp. The Na2CaSn2Ge3O12:Dy3+ phosphor is deemed to be a potential storage phosphor that can be applied in the field of practical application. After incorporation of Dy3+ into the Na2CaSn2Ge3O12 matrix, new foreign traps (DyCa°, DyNa°°) were produced, and the concentration of internal traps (VCa″, VNa′) increased approximately 10 times. The luminous mechanism of the Na2CaSn2Ge3O12:Dy3+ phosphor was studied.

Naphthalene Benzimidazole Based Neutral Ir(III) Emitters for Deep Red Organic Light-Emitting Diodes.

Rigid naphthalene benzimidazole (NBI) based ligands (L1 and L2) are synthesized and utilized to make deep red phosphorescent cyclometalated iridium(III) complexes ([Ir(NBI)2(PyPzCF3)] (1) and [Ir(DPANBI)2(PyPzCF3)] (2)). Complexes 1 and 2 are prepared from the reaction of L1/L2 with the aid of ancillary ligands (PyPzCF3, 2-(3-(trifluoromethyl)-1H-pyrazol-5-yl)pyridine) in a two step method. The complexes are characterized by analytical and spectroscopic methods, as well as X-ray diffraction for 1. These complexes show a strong emission in the range of 635-700 nm that extends up to the near-infrared region (800 nm). The introduction of the diphenylamino (DPA) donor group on the naphthalene unit leads to a further red-shift in the emission. The complexes exhibit radiative quantum efficiency (ΦPL) of 0.27-0.29 in poly(methylmethacrylate) film and relatively short phosphorescence decay lifetimes (τ = 1.1-3.5 μs). The structural, electronic, and optical properties are investigated with the support of density functional theory (DFT) and time-dependent-DFT calculations. The calculation results indicate that the lowest-lying triplet (T1) excited state of 1 has a mixed metal-to-ligand charge transfer (3MLCT) and ligand-centered (3LC) character, while 2 shows a dominant 3LC character. Deep red-emitting organic light-emitting diodes fabricated using 1 as a dopant display a maximum external quantum efficiency of 10.9% with the CIE color coordinates of (0.690, 0.294), with an emission centered at 644 and 700 nm. Similarly, the emitter 2 also shows a maximum external quantum efficiency of 6.9% with emissions at 657 and 722 nm.

Structure-lock induced phosphorescence lifetime enhancing of (9H-carbazol-9-yl)(phenyl)methanone: An organic phosphorescent materials

Different molecular design strategies have been performed to study purely organic materials with room-temperature phosphorescence (RTP) by suppressing nonradiative deactivation and facilitating intersystem crossing. In this work, a synthetic strategy based on CPM ((9H-carbazol-9-yl)(phenyl)methanone) has been performed to achieve long lived RTP by immobilizing the torsion of benzophenone moiety and forming a six-membered heterocyclic ring containing nitrogen element. This synthesized locked-CPM (8H-indolo[3,2,1-de]phenanthridin-8-one) with higher rigidity has planar configuration both in the singlet state and the triplet state, whose locking configuration effectively inhibits the twist intramolecular charge transfer (TICT) of CPM and significantly reduces the energy gap between the singlet and triplet states to 0.89 ev. This change facilitates intersystem crossing and the generalization of triplet excitons. By fitting the phosphorescence decay curves, we demonstrate that the phosphorescence lifetime of the locked-CPM has increased by nearly forty times compared with that of the CPM, indicating that the presented strategy will bring insight into the developing long lived RTP materials. It is noted that suppress the vibration and torsion of molecular and reduce the energy gap between single-triplet states will favors of long phosphorescence lifetime.

Molecular-Level Insight of Cu(I) Complexes with the 7,8-Bis(diphenylphosphino)-7,8-dicarba-nido-undecaborate Ligand as a Thermally Activated Delayed Fluorescence Emitter: Luminescent Mechanism and Design Strategy.

Investigation of the clear structure-property relationship and microscopic mechanism of thermally activated delayed fluorescence (TADF) emitters with high emission quantum yield is a direction worthy of continuous efforts. The instructive theoretical principle of TADF material design is critical and challenging. Here, we carried out theoretical calculation on two experimental Cu(I) complexes with the same 7,8-bis(diphenylphosphino)-7,8-dicarba-nido-undecaborate (dppnc) but different N^N ligands [dmbpy = 6,6'-dimethyl-2,2'-bipyridine (1) or dmp = 2,9-dimethyl-1,10-phenanthroline (2)] to briefly elaborate the structure-TADF performance relationship and luminescence mechanism. It was found that enhanced rigidity by the fused benzene ring between two pyridyl units in complex 2 leads to (i) higher allowedness of S1 → S0, (ii) more effective reverse intersystem crossing (RISC), and (iii) better relative stability of the T1 state, which could be responsible for its excellent TADF behavior. Thus, a strategy of extending π conjugation in the N^N ligand could be deduced to further enhance the quantum yield. We validated it and have succeeded in designing analogue complex 4 by extending π conjugation with an electron-withdrawing pyrazinyl. Benefiting from the smaller energy gap (ΔEST) and plunged reorganization energy between the S1 and T1 states, the rate of RISC in complex 4 (1.05 × 108 s-1) increased 2 orders of magnitude relative to that of 2 (5.80 × 106 s-1), showing more superiority of the TADF behavior through a better balance of RISC, fluorescence, and phosphorescence decay. Meanwhile, the thermally activated temperature of 4 is only 165 K, implying that there is a low-energy barrier. All of these indicate that the designed complex 4 may be a potential TADF candidate.

Determination of a Kinetic Law of Phosphorescence Decay Using a Conventional Photo Camera and Free Image Processing Software

Investigation of the kinetics of phosphorescence decay is a suitable learning task in studying the formal kinetics, and also properties of crystal phosphors. Kinetics of phosphorescence decay of crystal phosphors can be experimentally investigated at home as part of distance learning, using a conventional digital photo camera and a luminescent object such as a glow-in-the-dark toy. During the work, students get acquainted with the basic laws of phosphorescence decay kinetics and determine which law is observed in their object and what mechanism it corresponds to.

Luminescent Rhenium(I)tricarbonyl Complexes Containing Different Pyrazoles and Their Successive Deprotonation Products: CO2 Reduction Electrocatalysts.

Cationic fac-[Re(CO)3(pz*H)(pypzH)]OTf (pz*H = pyrazole, pzH; 3,5-dimethylpyrazole, dmpzH; indazole, indzH; 3-(2-pyridyl)pyrazole, pypzH) were obtained from fac-[ReBr(CO)3(pypzH)] by halide abstraction with AgOTf and subsequent addition of the corresponding pyrazole. Successive deprotonation with Na2CO3 and NaOH gave neutral fac-[Re(CO)3(pz*H)(pypz)] and anionic Na{fac-[Re(CO)3(pz*)(pypz)]} complexes, respectively. Cationic fac-[Re(CO)3(pz*H)(pypzH)]OTf, neutral complexes fac-[Re(CO)3(pz*H)(pypz)], and fac-[Re(CO)3(pypz)2Na] were subjected to photophysical and electrochemical studies. They exhibit phosphorescent decays from a prevalently 3MLCT excited state with quantum yields (Φ) in the range between 0.03 and 0.58 and long lifetimes (τ from 220 to 869 ns). The electrochemical behavior in Ar atmosphere of cationic and neutral complexes indicates that the oxidation processes assigned to ReI → ReII occurs at lower potentials for the neutral complex compared to cationic complex. The reduction processes occur at the ligands and do not depend on the charge of the complexes. The electrochemical behavior in CO2 saturated media is consistent with CO2 electrocatalyzed reduction, where the values of the catalytic activity [icat(CO2)/icat(Ar)] ranged from 2.7 to 11.5 (compared to 8.1 for fac-[Re(CO)3Cl(bipy)] studied as a reference). Controlled potential electrolysis for the pyrazole cationic (3a) and neutral (4a) complexes after 1 h affords CO in faraday yields of 61 and 89%, respectively. These values are higher for indazole complexes and may be related to the acidity of the coordinated pyrazole.

Iridium Corroles Exhibit Weak Near-Infrared Phosphorescence but Efficiently Sensitize Singlet Oxygen Formation

Six-coordinate iridium(III) triarylcorrole derivatives, Ir[TpXPC)]L2, where TpXPC = tris(para-X-phenyl)corrole (X = CF3, H, Me, and OCH3) and L = pyridine (py), trimethylamine (tma), isoquinoline (isoq), 4-dimethylaminopyridine (dmap), and 4-picolinic acid (4pa), have been examined, with a view to identifying axial ligands most conducive to near-infrared phosphorescence. Disappointingly, the phosphorescence quantum yield invariably turned out to be very low, about 0.02 – 0.04% at ambient temperature, with about a two-fold increase at 77 K. Phosphorescence decay times were found to be around ~5 µs at 295 K and ~10 µs at 77 K. Fortunately, two of the Ir[TpCF3PC)]L2 derivatives, which were tested for their ability to sensitize singlet oxygen formation, were found to do so efficiently with quantum yields Φ(1O2) = 0.71 and 0.38 for L = py and 4pa, respectively. Iridium corroles thus may hold promise as photosensitizers in photodynamic therapy (PDT). The possibility of varying the axial ligand and of attaching biotargeting groups at the axial positions makes iridium corroles particularly exciting as PDT drug candidates.

Kinetics of Phosphorescence Decay of the New Paramagnetic Osmium(IV) Tetra-Crown Porphyrinate in Polystyrene at Temperatures of 77 and 298 K

The reaction of osmium(II) tetra-15-crown-5-porphyrin (Os(II)TCP) with molecular iodine in high yield yielded the corresponding osmium(IV) porphyrin containing iodide ions in the axial positions of the osmium(IV) atom and possessing paramagnetic properties according to 1H NMR. The iodine anions in the complex create an additional heavy atom effect in addition to such an effect from the osmium(IV) cation, which is of certain interest from the point of view of increasing the probability of phosphorescence transitions in osmium(IV) crown porphyrin molecules. The paramagnetism of osmium(IV) crown porphyrin also affects the probability of phosphorescence transitions, and this effect depends on temperature. These two effects (paramagnetism and the heavy atom effect) create some interest in terms of the possibility of creating a phosphorescent temperature sensor based on the new osmium(IV) crown porphyrin. A comparative analysis of the kinetics of phosphorescence decay of osmium(IV), osmium(VI) and osmium(II) porphyrins in the polystyrene matrix at temperatures of 298 and 77 K. It was found that the new osmium(IV) crown porphyrin has the highest phosphorescence lifetime with temperature in this series and can be considered as a luminescent temperature sensor for changes in phosphorescence lifetime.

A general framework for non-exponential delayed fluorescence and phosphorescence decay analysis, illustrated on Protoporphyrin IX

Delayed fluorescence (DF) is a long-lived luminescence process used in a variety of applications ranging from oxygen sensing in biological tissues to organic Light Emitting Diodes. In common cases, DF results from the de-excitation of the first excited triplet state via the first excited singlet state of the chromophore, which produces a mono-exponential light signal whose amplitude and lifetime give an insight into the probed environment. However, non-linear de-excitation reactions such as triplet-triplet annihilation, which can cause decays to lose their mono-exponential nature, are often neglected. In this work, we derive a global framework to properly interpret decays resulting from a combination of linear and non-linear de-excitation processes. We show why the standard method of using multi-exponential models when decays are not mono-exponential is not always relevant, nor accurate. First, we explain why the triplet de-excitation and light production processes should be analyzed individually: we introduce novel concepts to precisely describe these two processes, namely the deactivation pathway – the reaction which mainly contributes to the triplet state de-excitation – and the measurement pathway – the reaction which is responsible for light production. We derive explicit fitting functions which allow the experimenter to estimate the reaction rates and excited state concentrations in the system. To validate our formalism, we analyze the in vitro Transient Triplet Absorption and DF of Protoporphyrin IX, a well-known biological aromatic molecule used in photodynamic therapy, cancer photodetection and oxygen sensing, which produces DF through various mechanisms depending on concentration and excitation intensity. We also identify the precise assumptions necessary to conclude that triplet-triplet annihilation DF should follow a mono-exponential decay with a lifetime of half the triplet state lifetime. Finally, we describe why the commonly used definitions of triplet / DF lifetime are ill-defined in the case where second-order reactions contribute to the deactivation process, and why the fitting of precise mixed-orders DF kinetics should be preferred in this case. This work could allow the correct interpretation of various long-lived luminescence processes and facilitate their understanding.

Mechanism study of TADF and phosphorescence in dinuclear copper (I) molecular crystal using QM/MM combined with an optimally tuned range-separated hybrid functional

Abstract Investigations of the detailed photophysical processes are of great significance for future material improvements and novel designing strategies. Herein, the interconversion and decay rates of the first excited singlet state (S1) and triplet state (T1) for the Cu2I2(P^N)3 complex are calculated using the thermal vibration correlation function (TVCF) theory, combined with the optimally tuned range-separated hybrid functional (OT-ωB97XD) method at different temperature. A methodology with the building different ONIOM models, was carried over into simulation of crystal environment. All calculated results perfectly match the experimentally available data, demonstrating the validity of our applied theoretical approach. It has been found that the reverse intersystem crossing (RISC) rate kRISC from T1 to S1 is 3.11 × 1010 s−1 at 300 K, about 7 order of magnitude larger than the phosphorescence rate kr(T) = 3.71 × 103 s−1, and far more than ISC rate kISC(T1-S0) of 6.38 s−1. The S1 state can be an efficient thermal population from the T1 state by the RISC pathway, leading to an occurrence of thermally activated delayed fluorescence (TADF), and the estimated delayed time of τ(TADF) = 10 μs. On the other hand, the T1 state also exhibits stronger admixtures with higher lying singlet states due to stronger SOC, having a larger ZFS of 17 cm−1, thus, a relatively fast phosphorescence decay rate of kr(T) = 8.542 × 103 s−1 estimated by Einstein emission formula is observed. Further calculation results show that the emission intensities are stemming by 91% from the S1 state as TADF and by 9% as phosphorescence from the T1 state at 300 K, which indicates the ambient temperature emission represents the combined luminescence of TADF and phosphorescence. Our work would be useful for improving and designing the luminescent material combined high-efficiency TADF with phosphorescence.

Diffusion-inspired time-varying phosphorescent decay in a nanostructured environment

Structured environment controls dynamics of light-matter interaction processes via modified local density of electromagnetic states. In typical scenarios, where nanosecond-scale fluorescent processes are involved, mechanical conformational changes of the environment during the interaction processes can be safely neglected. However, slow decaying phosphorescent complexes (e.g. lanthanides) can efficiently sense micro- and millisecond scale motion via near-field interactions. As the result, lifetime statistics can inherit information about nano-scale mechanical motion. Here we study light-matter interaction dynamics of phosphorescent dyes, diffusing in a proximity of a plasmonic nanoantenna. The interplay between the time-varying Purcell enhancement and stochastic motion of molecules is considered via a modified diffusion equation, and collective decay phenomena is analysed. Fluid properties, such as local temperature and diffusion coefficient are mapped on phosphorescent lifetime distribution extracted with the help of inverse Laplace transform. We present rather simple photonic platform enabling contactless all-optical thermometry and diffusion measurement and paving a way for a plethora of possible applications. Among them, the proposed analysis can be used for detailed studies of nanofluidic processes in lab-on-a-chip devices, which are extremely hard or even impossible to analyse with other optical methods.

Luminescent properties and energy transfer mechanism from Tb3+ to Eu3+ doped in Y3Al5O12 phosphors

The structural and luminescent properties of Y3Al5O12:Eu,Tb (YAG) compounds produced by a modified sol-gel method using glucose as a polymerising agent are investigated in this study. X-ray diffraction is utilised in order to analyse the formation of the crystalline phase. The luminescent properties are investigated by excitation and emission measurements from photoluminescence and X-ray excited optical luminescence (XEOL) measurements, which are strongly influenced by the concentration of Eu3+ and Tb3+ dopants. X-ray absorption spectroscopy (XAS) is measured at the Eu LIII–edge in order to confirm the Eu valence. The results indicate good stability of Eu ions in the YAG structure when submitted to higher ionising energies. The chromaticity diagram indicates that, with different molar ratios of Eu3+ and Tb3+ ions, it is possible to obtain white-light emission. In addition, it is observed that the amount of dopant/co-dopant ions leads to changes in the phosphorescent decay time.

Кинетика затухания фосфоресценции при наличии статистического распределения молекул по скоростям излучательной и безызлучательной дезактивации триплетных возбуждений

Approximate formulas of phosphorescence decay kinetics under the conditions of the statistical scatter of molecules over rate constants of radiative or non-radiative deactivation of triplet excitation have been obtained. It is shown that the phosphorescence decay function has different form for these two cases. The obtained difference in kinetics was used to establish the reason for the deviation from the exponential law and faster decay of the sensitized phosphorescence of naphthalene and diphenyl in n-paraffin matrices ( T = 77 K) in the presence of heavy atoms in the donor.