Dependence Of Luminescence Intensity Research Articles

Synthesis and photoluminescence properties of Ba3(PO4)2:Eu3+/2+ phosphors

Single-phase phosphors of Ba3–хEu2х/3(PO4)2 (x = 0.01, 0.02) were obtained for the first time using solid-phase synthesis. These phosphors are isostructural to the palmierite mineral. The self-reduction of Eu3+ to Eu2+ in the Ba3(PO4)2 host was observed in air at high temperature. The dependence of luminescence intensity on temperature was studied over a broad range of 80–500 K. The luminescence intensity of Eu3+ is significantly depends on temperature and decreases as the temperature increases, while Eu2+ emission remains stable between 150 and 500 K. Eu3+ ions incorporated into the polyhedra of the M1 sites of the Ba3(PO4)2 structure demonstrated improved thermal stability compared to Eu3+ ions in the polyhedra of the M2 sites. Photoluminescence spectra, when excited at 395 nm, consist of intense bands at 585 nm and 610 nm, typical for Eu3+ cations. When excited at 330 nm, the luminescence spectra display a broad band centered at 425 nm, typical for Eu2+ cations. The resulting orange-red phosphors have potential applications in solid-state lighting.

Anti-thermal quenching of luminescence in Y2W3O12:Yb3+/RE3+ (RE = Er/Ho/Tm) and its temperature sensing application.

Herein, a series of Y2W3O12:10%Yb3+/x%RE3+ (RE = Er/Ho/Tm) phosphors is prepared via a solid-state reaction. The upconversion and downshift luminescence properties of the phosphors were investigated under an excitation of 980 nm. The bright blue light emission from Tm3+ ion and the green and red light emissions from Ho3+(Er3+) ions were observed. The near-infrared light intensity of NIR-I (Tm3+, ∼850 nm), NIR-II (Er3+: ∼1550 nm; Tm3+: ∼1783 nm) and NIR-III (Ho3+: ∼2050 nm) were analyzed. In particular, the dramatic thermal enhancement phenomenon in visible and NIR regions was exhibited by the Y2W3O12:10%Yb3+/x%RE3+ (RE = Er/Ho/Tm) phosphors. Among them, the green light intensity of Er3+ ions increased 26.77 times, from 303 to 573 K. The NIR-II emission band (∼1783 nm) intensity of Tm3+ ions at 533 K increased 168.7 times compared to that at 313 K. The possible thermal enhancement mechanism is illustrated by the negative thermal expansion (NTE) and Frenkel defect of the Y2W3O12 host. Finally, the optical temperature sensing performances of Y2W3O12:10%Yb3+/x%RE3+ (RE = Er/Ho/Tm) samples are investigated according to the luminescence intensity dependence relationship on temperature. The maximum value of SR reached 4.24% K-1 at 353 K for Y2W3O12:10%Yb3+/0.6%Ho3+ phosphor. The results indicate that the Y2W3O12:10%Yb3+/x%RE3+ (RE = Er/Ho/Tm) phosphors possess anti-thermal quenching properties and are suitable for developing optical temperature sensors.

Simple express precursor synthesis of erbium-doped yttrium oxide luminescent material for optical thermometry

A new, simple and inexpensive method for the preparation of nanosized (Y1-xErx)2O3 oxides, including the stages of synthesis and thermolysis of Y1-xErx(HCOO)3 precursors, has been developed. The precursors were obtained by the interaction of mixtures of yttrium and erbium nitrates with formic acid. The effect of erbium concentration on the structure, morphology, and optical properties of (Y1-xErx)2O3 oxides was studied using X-ray diffraction, scanning electron microscopy, and optical absorption methods. Under UV excitation (Y1-xErx)2O3 oxides with 0.005≤x ≤ 0.25 exhibit strong green luminescence related to the 2H11/2/4S3/2 → 4I15/2 transitions and weak red luminescence associated with the 4F9/2 → 4I15/2 transition. According to the CIE chromaticity coordinates, the oxides demonstrate a yellowish-green color emission. A noticeable decrease in the luminescence intensity was recorded for oxides with erbium concentrations above 2.5 mol.% (x = 0.025). Yellowish-green and yellow green upconversion emission resulting from the 4S3/2 → 4I15/2 and the 4F9/2 → 4I15/2 transitions of Er3+ ions were observed upon continuous 980 nm diode laser excitation. When the concentration of erbium in (Y1-xErx)2O3 oxides increases, the luminescence color changes and the intensity of upconversion emission rises. The maximum intensity of upconversion emission was observed for the (Y0.9Er0.1)2O3 oxide. A two-photon upconversion mechanism was established based on the pumping power dependence of UC luminescence intensity. The thermoluminescence characteristics of (Y0.9Er0.1)2O3 oxides based on the ratio of the intensities of the lines corresponding to thermal-coupled 2H11/2 and 4S3/2 levels were determined, the absolute and relative sensitivity values was calculated, and the prospects for using this oxide in non-contact optical thermometers were estimated.

ЗАВИСИМОСТЬ СОСТАВА И ЛЮМИНЕСЦЕНТНЫХ ХАРАКТЕРИСТИК ЛЮМИНОФОРОВ ОТ ТЕМПЕРАТУРЫ ПИРОЛИЗА ПРЕКУРСОРОВ

General conditions for the synthesis of phosphors based on mixed oxides of REE and rare elements by the low-temperature extraction-pyrolytic method were discussed. Dependence of morphology, composition and relative integrated luminescence intensity of phosphors on the pyrolysis temperature of precursors was investigated.

Dy3+ and Eu3+ co-activated gadolinium aluminate borate phosphor: Synthesis, enhanced luminescence, energy transfer and tunable color

The synthesis of GdAl3(BO3)4 phosphors incorporated with activators of Dy3+ and Dy3+/ Eu3+was successful and achieved through the gel combustion method. Powder X-ray diffraction (XRD) was employed to identify phase purity and the effects of dopant concentration on the crystallographic structure. The results of Photoluminescence (PL) measurements revealed that the intensity and lifetime of luminescence properties varied depending on the concentrations of Dy3+ and Eu3+ ions. The dependence of luminescence intensity on doping concentration is investigated with respect to the energy transfer process between Eu3+ and Dy3+ ions. A decrease in luminescence lifetime occurs with increasing concentrations of Eu3+ co-doping. The energy transfer was also investigated using decay curve analysis. The co-doping of Eu3+ significantly boosts the energy transfer efficiency from 26% to 84%. These findings make GdAl3(BO3)4: Dy3+, Eu3+ phosphors an ideal choice for LED applications in solid state lighting and displays.

Ультранизкочастотные осцилляции интенсивности люминесценции полимерной мембраны в водных растворах солей

The paper studies luminescence from the Nafion polymer membrane surface at its swelling in the isotonic aqueous solutions and bi-distilled water using the experimental photo luminescent spectroscopy. Liquid samples were preliminarily treated with the electric pulses with duration of 1 µs and amplitude of 0.1 V using antenna in the form of a flat capacitor. Experiments in photo luminescent spectroscopy were carried out 20 min after the electric pulse treatment. Typical luminescence intensity dependence on the membrane swelling time could be represented as the exponentially decreasing function. Characteristic decay time of the corresponding functions and stationary level of the membrane luminescence intensity depend on the electrical pulses repetition rate. The obtained dependencies could well be reproduced. However, dependence of the luminescence intensity at certain pulse repetition rates appears to be a random function, and the reproducibility is missing. It could be assumed that these stochastic effects are associated with exposure to random external force of the electromagnetic nature acting on the polymer membrane during swelling. Low-frequency pulsations of neutron stars or white dwarfs are the source of this random force according to the authors of the work. This effect is associated with depolarization during the low-frequency electromagnetic field scattering caused by the neutron stars pulsation. Depolarization effect arises due to scattering on long-living anisotropic clusters of nano-bubbles, which, in turn, are becoming anisotropic in the external field of a flat capacitor. Depolarized scattered radiation causes stochastic oscillations of the polymer fibers unwound into the bulk liquid. In this case, luminescence should also acquire the stochastic character taking into account the effect of resonant luminescence energy transfer from a donor to the luminescence acceptor

Bi3+ - doped garnets as possible ultraviolet persistent phosphors

Ultraviolet (UV) persistent luminescence (afterglow) and thermally stimulated luminescence observed in the 3.6–4.2 eV energy range are studied for microcrystalline powders of the Bi3+-doped Lu3Ga5O12, Y3Ga5O12, and Ca3Ga2Ge3O12 garnets after their selective UV irradiation at 295 K in the 4–6 eV energy range. Emission and excitation spectra and decay kinetics of the persistent luminescence, as well as the luminescence intensity dependence on the irradiation duration, are measured at 295 K. No UV emission has been observed in the afterglow spectrum of the Gd3Ga5O12:Bi, Lu3Al5O12:Bi, and Y3Al5O12:Bi garnets. The processes resulting in the appearance of the UV persistent luminescence in the investigated Bi3+-doped garnets are discussed. The conditions are formulated which ensure the appearance of this phenomenon in Bi3+-doped compounds and, thus, could inspire the discovery of new effective UV persistent phosphors.

Luminescence and energy transfer of Ce3+, Eu2+ co-doped Ba2Mg(BO3)2 for potential anti-counterfeiting applications

The phosphors Ba2Mg(BO3)2 activated with Ce3+ and Eu2+ ions are prepared by a solid-state reaction method at high-temperature and the Rietveld structure refinement of the host compound is performed. The synchrotron radiation VUV - UV excitation, UV – vis emission and luminescence decay spectra, as well as the dependencies of luminescence intensity and lifetime on doping content and temperature are systematically investigated. In addition, the electron-vibrational interaction (EVI) of Eu2+ ions with coordination surroundings and the Ce3+→Eu2+ energy transfer (ET) dynamics are studied in detail. Based on above discussion, the potential applications of co-doped phosphors in excitation wavelength and temperature dual-response optical anti-counterfeiting are demonstrated.

Effect of fluorine substitution on the structure and spectral property of fluorotellurite glass for upconversion luminescence thermometry

A series of TeO2–ZnO–ZnF2–La2O3–Yb2O3–Er2O3 glasses (TZL) with different amount of ZnF2 were prepared by the melt quenching method. The effects of fluorine concentration on the density, refractive index, thermal behavior, and vibrational characteristic of TZL glasses were analyzed. The Judd-Ofelt (J-O) theory was employed to study the spectroscopic properties of Er3+ ions. By using the J-O intensity parameters the spontaneous radiative transition probabilities, fluorescence branching ratios, and radiative lifetimes of some concerned transitions of Er3+ were predicted. The potential of TZL glasses for the gain around 1.5 μm was briefly evaluated. Moreover, the upconversion luminescence was investigated under the excitation of 980 nm laser. The dependence of luminescence intensity on pump power revealed that the upconversion luminescence of Er3+ in TZL glasses are contributed by two-photon involved energy transfer processes. Furthermore, the adjacent upconversion green emissions of Er3+ ions were used to temperature sensing based on the fluorescence intensity ratio (FIR) technique. High absolute sensitivity and resolution have been obtained, which indicate that the TZL glasses are potential materials for optical fiber temperature sensors.

Study of synthesis temperature effect on β-NaGdF4: Yb3+, Er3+ upconversion luminescence efficiency and decay time using maximum entropy method

Upconversion materials have several advantages for many applications due to their great potential in converting infrared light to visible. For practical use, it is necessary to achieve high intensity of UC luminescence, so the studies of the optimal synthesis parameters for upconversion nanoparticles are still going on. In the present work, we analyzed the synthesis temperature effect on the efficiency and luminescence decay of β-NaGd0.78Yb0.20Er0.02F4 (15–25 nm) upconversion nanoparticles with hexagonal crystal structure synthesized by anhydrous solvothermal technique. The synthesis temperature was varied in the 290 °C–320 °C range. The synthesis temperature was shown to have a significant influence on the upconversion luminescence efficiency and decay time. The coherent scattering domain linearly depended on the synthesis temperature and was in the range 13.1–22.3 nm, while the efficiency of the upconversion luminescence increases exponentially from 0.02 to 0.10% under 1 W cm−2 excitation. For a fundamental analysis of the reasons for the upconversion luminescence intensity dependence on the synthesis temperature, it was proposed to use the maximum entropy method for luminescence decay kinetics processing. This method does not require a preliminary setting of the number of exponents and, due to this, makes it possible to estimate additional components in the luminescence decay kinetics, which are attributed to different populations of rare-earth ions in different conditions. Two components in the green luminescence and one component in the red luminescence decay kinetics were revealed for nanoparticles prepared at 290 °C–300 °C. An intense short and a weak long component in green luminescence decay kinetics could be associated with two different populations of ions in the surface quenching layer and the crystal core volume. With an increase in the synthesis temperature, the second component disappears, and the decay time increases due to an increase in the number of ions in the crystal core volume and a more uniform distribution of dopants.

A giant enhancement in the up-conversion luminescence and high temperature sensitivity of Bi3+ doped ZnMoO4:Er3+ up-conversion phosphor.

Luminescence intensity is a critical factor for upconversion (UC) oxides with high phonon energy. Herein, an effective enhancement in UC luminescence is achieved in the ZnMoO4:Er3+ phosphor via Bi3+ doping. UV-vis-NIR diffuse reflectance spectroscopy verifies the fact that the absorption at 980 nm is enhanced by the introduction of Bi3+. The physical mechanism is that Bi3+ doping affects the transition probability between the f-levels of Er3+. Therefore, the green and red emission intensities are increased 82.4 and 37 times, respectively. The dependence of luminescence intensity on the power of Bi3+-doped ZnMoO4:Er3+ combined with density functional theory (DFT) calculations also confirms the proposed energy transfer mechanism. Based on the excellent green emission, the 980 nm excited optical temperature sensing property of the synthesized sample is realized in a wide temperature range by monitoring the intensity of UC luminescence. The theoretically calculated absolute sensitivity of the optical temperature sensor was SA = 3.04% K-1 at 1253 K. This work paves a new way for enhancing UC luminescence and will arouse extensive interest in noncontact temperature-sensing applications.

Intense single-band red upconversion luminescence of Er3+/Yb3+ codoped BiOCl nanocrystals via a facile solvothermal strategy

Lanthanide doped BiOCl phosphors have recently emerged as a new type of upconversion (UC) host material due to their distinct crystal structure and tailorable UC emissions. However, the modulated single-band red UC luminescence through host size manipulation has not been well explored. In this work, we reported a facile solvothermal strategy to obtain the single-band red UC emission in BiOCl: Yb3+/Er3+ nanocrystals. It shows that just by changing the ethanol amount in the mixed solvent, the intense and pure red UC luminescence of Er3+ ion can be achieved at the same time. The possible reason for the single-band red UC emission and the dependence of UC luminescence intensity on the nanosheet size are proposed and discussed. The results of this work can provide an effective route to control the UC emission of Ln3+ doped layered materials, which might be widely applied in the areas of color displays and biological imaging.

Luminescent and structural properties of ScxY1-xVO4:Eu3+ solid solutions

Solid solutions of ScxY1-xVO4:Eu3+ were grown by solid state method and their structural and luminescent properties were studied using XRD, SEM and luminescence spectroscopy techniques. The influence of annealing on sample phase purity is investigated. A linear decrease of crystal lattice constants with the increase of x value is shown. The influence of crystal structure disorder on the features of Eu3+ emission spectra in the solid solutions is studied. The dependence of luminescence intensity on x value under intracenter Eu3+ excitation differs from that obtained under interband and high-energy excitations due to the peculiarities of energy transfer from the host to Eu3+ emission centers. The role of VO43− group as well as cation electronic states in the energy transfer to Eu3+ emission centers is discussed. The bandgap values are determined using the data of TSL excitation spectra.

Photoluminescence characteristics and energy transfer phenomena in Ce3+-doped YVO4 single crystal

Abstract The undoped YVO4 and Ce3+-doped YVO4 single crystals have been successfully grown by the Czochralski method in a medium frequency induction furnace. The X-ray diffraction patterns testified that all samples exhibited the pure tetragonal YVO4 crystalline phase without any parasitic phases. The optical properties of Ce3+-doped YVO4 single crystals with different doping concentrations were investigated via a combination of absorption, emission, and excitation spectra. Dependence of luminescence and absorption intensity on Ce3+ doping concentration was discussed at different excitation wavelengths. The typical transitions of Ce3+ ions and the unusual intrinsic luminescent phenomena of VO 4 3 − {\text{VO}}_{4}^{3-} groups were observed and investigated in Ce3+-doped YVO4 crystals. More attentions were paid to ascertaining the corresponding transition states, analyzing luminescent mechanism, and revealing the energy transfer from VO 4 3 − {\text{VO}}_{4}^{3-} to Ce3+ ions. In addition, the CIE chromaticity coordinates and correlated color temperature were calculated on a basis of emission spectra under different excitation wavelengths.

Temperature and spatial dependence of carrier lifetime and luminescence intensity in Ge0.95Sn0.05 layer

In this work we present a study of spatial and temperature dependencies of carrier lifetime and photoluminescence in pseudomorphic Ge0.95Sn0.05 layer on silicon by applying contactless time-resolved differential absorption and photoluminescence techniques. The observed small lifetime and photoluminescence intensity spatial variations (~10%) indicate for good material homogeneity. Differential transmission kinetics exhibit fast bleaching and slow absorption components related to thermalization (few hundreds of picoseconds) and surface recombination (few tens of nanoseconds) processes. Temperature dependent photo-luminescence measurements indicate activation of carriers from L to Γ valley, governing dominant direct photoluminescence emission band at 1850 nm at 300 K. These direct transitions explain more efficient and blue-shifted by 150 nm photoluminescence emission at room temperature. At low temperatures direct emission is related to non-thermalized carriers, while indirect one is caused by depopulation of light hole band with temperature.

Effect of carbon backbone on luminescence properties of Eu-organic hybrid thin films prepared by ALD/MLD

Here we show that the backbone of the organic ligand has a profound impact on the luminescence characteristics of lanthanide-organic materials. We employ the emerging atomic/molecular layer deposition (ALD/MLD) technique to deposit europium-based thin films where the organic ligands vary in terms of the number of aromatic rings in their backbone (benzene, naphthalene and anthracene). Enlarging the backbone shifts the excitation towards visible wavelengths, but it simultaneously decreases the emission intensity. Moreover, for the Eu-terephthalate films with the single benzene ring as the organic backbone, we investigate the effects of diluting the Eu3+ concentration with Y3+ to reveal that the emission intensity is optimized around 12% Eu3+ concentration. Interestingly, such a dependence of luminescence intensity on the concentration of emitting species suggests that our (Eu,Y)-organic thin films behave more like ionic phosphors than discrete metal–ligand molecules.Graphical abstract

Thermal quenching of luminescence in (Lu,Gd,Y)3(Ga, Al)5O12:Ce complex garnet ceramics at high and low temperatures

Cerium-doped complex garnets with the general formula (Lu,Y,Gd)3,(Ga,Al)5O12:Ce are promising materials to be used in PET and CT scanners. By modifying garnet composition (bandgap engineering), one can adjust its scintillation properties to fit a specific set of requirements. In certain compositions, Ce3+ luminescence intensity can decrease upon cooling (negative thermal quenching). The reason for that is still a matter of active debate. This article is focused on negative thermal quenching in Ce-doped (Lu,Gd)3(Ga,Al)5O12 garnet ceramics. We have measured thermally stimulated luminescence, temperature dependence of the X-ray excited luminescence intensity, and other scintillation properties of samples which have different Lu and Ga content and were annealed in different conditions. We discuss that negative thermal quenching in our samples can be attributed to the process of charge carrier localization on traps at lower temperatures.

SYNTHESIS AND LUMINESCENCE PROPERTIES OF K0,5xBi1-0,5x(MoxV1-x)O4 SOLID SOLUTIONS

The conditions of heterovalent substitution in cationic and anionic positions of хK0,5Bi0,5MoO4 – (1-х)BiVO4 system within range of х = 0.1-0.9 with forming of К0,5xBi1-0,5x(MoxV1-x)O4 solid solutions, those possess scheelite-like type structure have been studied. All the samples of series were obtained by solid state technique. It was shown by IR spectroscopy and X-ray diffraction studies that molybdenum and vanadium occupying one crystallographic position with statistical distribution in х = 0.1–0.9 range of substitution. As result a lowering of lattice symmetry from tetragonal to monoclinic take place with increasing of molybdenum content. Charge compensation in system is realized through proportional substitution of bismuth by potassium in (К/Bi)O8 polyhedra. The data on diffuse reflectance indicate that increasing of substitution degree, x, lead to proportional increasing of band gap values from 2.33 to 2.72 eV for the semiconductors obtained. Intrinsic photoluminescence of the samples has been observed at low temperatures but is absent at room temperature. Total intensity of visible luminescence increases with increasing of molybdenum content in К0.5xBi1-0.5x(MoxV1-x)O4 solid solutions. Spectra of photoluminescence consist of wide two-component band with maxima at 620 and 705 nm, respectively. Simultaneous analysis of literature data and dependences of luminescence intensity on molybdenum content allow assumption that short-wavelength component related with centers, those formed on molybdate groups. Long-wavelength component related with vanadate groups. The wide bands at 375 and 410 nm in the photoluminescence excitation spectra were ascribed to absorption transitions in molybdate and vanadate oxyanions, respectively. The solid solutions studied can be used as hosts for luminescent ions or in elaboration of photocatalysts.

Kinetics of luminescence calcium gallate activated by Yb3+, Er3+ ions

The paper presents the results of a study of the luminescent properties of calcium gallate activated by trivalent rare earth ions Yb3+ and Er3+. IR luminescence spectra of samples with a single activator Ca1‑хYbxGa2O4,Ca1‑хErxGa2O4 were studied when excited by radiation sources with a wavelength of 940 and 790 nm, respectively. The dependence of the luminescence intensity of samples on the concentration of rare earth ions is obtained. When the two-activator composition of Ca1‑х‑yYbxEryGa2O4 is excited by a semiconductor laser diode with a wavelength of 940 nm, IR luminescence is registered in the regions of 980-1100 nm and 1450-1670 nm. The radiation in these bands corresponds to electronic transitions in Yb3+ and Er3+ ions, respectively. For a luminescence band with a maximum at a wavelength of 1540 nm, the excitation spectra were measured, the maximum intensity is at the wavelengths: 930, 941, 970, 980 nm. The dependence of the IR luminescence intensity of a solid solution of Ca1‑х‑yYbxEryGa2O4 on the concentration of Er3+ ions was studied. With an increase in the concentration of Er3+ ions in the luminescence spectra, there is a redistribution in the intensity of the bands belonging to Yb3+ and Er3+ ions, which indicates the presence of energy transfer processes between these ions. The kinetics of IR luminescence attenuation was studied for series with one and two activators: Ca1‑хYbxGa2O4,Ca1‑хErxGa2O4, Ca1‑х‑yYbxEryGa2O4. It is established that the luminescence attenuation occurs mainly according to the exponential law, which indicates the predominance of the intracenter luminescence mechanism in the studied structures. Based on the analysis of the excitation and luminescence spectra of experimental samples, conclusions are made about the interaction of Yb3+ and Er3+ activator ions in the crystal lattice of calcium gallate.

A Biomimicking Method for Fabrication of Polymer Nanocomposites and Study of Their Physicochemical Properties

NpCdS nanocrystals are prepared by a microbial synthesis technique at the NRC “Kurchatov Institute”—GOSNIIGENETIKA. The stabilizing layer of nanocrystals consists of proteins, and the composition of the protein layer depends on the strain used in nanoparticle (NP) biosynthesis. The morphology and size, hydrodynamic diameter, zeta-potential, and luminescence properties of the biogenic NPs are investigated using electron microscopy, dynamic light scattering, and spectrofluorimetry, and the NPs are identified as quantum dots. The effects that temperature, pressure, and solvents have on the stability and luminescence intensity of biogenic NPs are studied in collaboration with the National Research Center Kurchatov Institute—IREA. For the aqueous NpCdS suspension, the dependence of luminescence intensity on the NP concentration range is established. The feasibility of incorporation and identification of NpCdS in an epoxy resin, polyimide, and polyvinyl alcohol is evaluated. Polymer nanocomposites find use in optoelectronics, biomedicine, and agriculture.