Decay Lifetime Research Articles

Downshifting and up-conversion luminescence of Yb3+-activated borotungstate Gd2(B2WO9) phosphor

Borotungstate phosphors Gd2–2xYb2x(B2WO9) (x=0, 0.05, 0.1, 0.15, 0.20, 0.25, 0.30) were synthesized using a straightforward high-temperature solid-state reaction method. The structural and luminescent properties of these phosphors were analyzed through X-ray powder diffraction, optical reflectance, excitation, and luminescence spectra. The up-conversion (UC) and downshifting (DS) processes, along with dynamic decay curves, were studied relative to the Yb3+ activator doping concentration. Upon near-UV excitation, a broadband near-IR luminescence (850–1150 nm) was observed from the 2F5/2→2F7/2 transitions in Yb3+ activators facilitated by significant energy transfer (ET) from the WO6 polyhedra to the Yb3+ activators within the lattices. Additionally, under 980 nm excitation to the 2F7/2 excitation states of Yb3+, blue cooperative up-conversion luminescence originating from Yb3+ pairs was detected. The mechanism behind this blue up-conversion was elucidated by analyzing decay lifetimes and emission intensity dependence on pump power, revealing that the cooperative de-excitation of adjacent Yb3+-Yb3+ ion pairs drives this process. This investigation introduces a practical approach for developing a novel Yb3+-doped borotungstate phosphor capable of exhibiting both downshifting and up-conversion luminescence.

Effect of the Crystalline Phase Type on the Thermoluminescent Response of ZrO2 Due to Different Synthesis Methods

ZrO2 samples were obtained using three different synthesis methods (Calcination, Co-precipitation and Hydrothermal). The samples were characterized to analyze the effect of the crystalline phase on their thermoluminescent (TL) and photoluminescent (PL) responses. The ZrO2 phase was analyzed by X-Ray diffraction (XRD) and Raman. Nanoparticle size distribution was obtained by scanning electron microscopy (SEM). For optical analysis, characterizations included absorbance measurements, where samples exhibited modifications in color centers, PL emission and experimental fluorescence lifetime decay ([Formula: see text] measurements. Additionally, their TL response was studied under UV (245[Formula: see text]nm and 385[Formula: see text]nm), and 6[Formula: see text]MV photon energy from LINAC excitation. The obtained results show the improvement of TL and PL properties due to ZrO2 phase while an amorphous ZrO2 synthesized by hydrothermal method is an excellent prospect to be used as TL material and it may be a promising scintillator material at 254[Formula: see text]nm.

Mechanistic Insights into Cellular and Molecular Targets of Zinc Oxide Quantum Dots (ZnO QDs) in Fungal Pathogen, Candida albicans: One Drug Multi-Targeted Therapeutic Approach.

Rationally designed multitargeted drugs, known as network therapeutics/multimodal drugs, have emerged as versatile therapeutic solutions to combat drug-resistant microbes. Here, we report novel mechanistic insights into cellular and molecular targets of ZnO quantum dots (QDs) against Candida albicans, a representative of fungal pathogens. Stable, monodispersed 4-6 nm ZnO QDs were synthesized using a wet chemical route, which exhibited dose-dependent inhibition on the growth dynamics of Candida. Treatment with 200 μg/mL ZnO QDs revealed an aberrant morphology and a disrupted cellular ultrastructure in electron microscopy and led to a 23% reduction in ergosterol content and a 53% increase in intracellular reactive oxygen species. Significant increase in steady-state fluorescence polarization and fluorescence lifetime decay of membrane probe 1,6-diphenyl-1,3,5-hexatriene (DPH) in treated cells, respectively, implied reduction in membrane fluidity and enhanced microviscosity. The observed reduction in passive diffusion of fluorescent Rhodamine 6G across the membrane validated the intricate relationship between ergosterol, membrane fluidity, and microviscosity. An inverse relationship existing between ergosterol biosynthetic genes, ERG11 and ERG3 in treated cells, related well with displayed higher susceptibilities. Furthermore, treated cells exhibited impaired functionality and downregulation of ABC drug efflux pumps. Multiple cellular targets of ZnO QDs in Candida were validated by in silico molecular docking. Thus, targeting ERG11, ERG3, and ABC drug efflux pumps might emerge as a versatile, nano-ZnO-based strategy in fungal therapeutics to address the challenges of drug resistance.

Efficient broadband NIR emission of Yb3+-activated double-perovskite tungstate Ba0.5MgLaWO6☆

Broad-band near-infrared (NIR) phosphors have garnered increasing attention due to the versatile applications in spectroscopy technology fields, but the choice of efficient NIR phosphors remains a challenge. Here, Yb3+-activated cubic double-perovskite tungstate Ba0.5MgLaWO6 was synthesized using a solid-state reaction method. A broadband NIR emission (800–1150 nm) is observed from the 2F5/2→2F7/2 transition of Yb3+ activators in Ba0.5MgLaWO6 under the excitation by UV and near-UV light. Photoluminescence (PL) spectra, decay and emission lifetimes, concentration-dependent intensities, and low temperature luminescence of Yb3+-activated Ba0.5MgLaWO6 were investigated to study the energy transfer (ET) from isolated WO6 polyhedra to Yb3+ activators. The main luminous mechanism involves cooperative energy transfer (CET), wherein, one high-energy excitation photon absorbed by host WO6 group converts to two NIR photons emitted by Yb3+. The partial substitution of Mo6+ for W6+ in Ba0.5MgLaWO6 further leads to a significant increase of the intensity and lifetime of the NIR luminescence. This work provides a feasible strategy for developing a new Yb3+-doped perovskite tungstate, which demonstrates efficient wavelength down-conversion from UV and near-UV to NIR. This material could find versatile applications as an effective NIR luminescent candidate.

Importance of Cosmic-Ray Propagation on Sub-GeV Dark Matter Constraints

We study sub-GeV dark matter (DM) particles that may annihilate or decay into Standard Model particles producing an exotic injection component in the Milky Way that leaves an imprint in both photon and cosmic-ray (CR) fluxes. Specifically, the DM particles may annihilate or decay into e + e −, μ + μ −, or π + π − and may radiate photons through their e ± products. The resulting e ± products can be directly observed in probes such as Voyager 1. Alternatively, the e ± products may produce bremsstrahlung radiation and upscatter the low-energy Galactic photon fields via the inverse Compton process, generating a broad emission from X-ray to γ-ray energies observable in experiments such as XMM-Newton. We find that we get a significant improvement in the DM annihilation and decay constraints from XMM-Newton (excluding thermally averaged cross sections of 10−31 cm3 s−1 ≲ 〈σ v〉 ≲ 10−26 cm3 s−1 and decay lifetimes of 1026 s ≲ τ ≲ 1028 s, respectively) by including best-fit CR propagation and diffusion parameters. This yields the strongest astrophysical constraints for this mass range of DM of 1 MeV to a few GeV and even surpasses cosmological bounds across a wide range of masses as well.

Simple MATLAB and Python scripts for multi-exponential analysis.

Multi-exponential decay is prevalent in magnetic resonance spectroscopy, relaxation, and imaging. This paper describes simple MATLAB and Python functions and scripts for regularized multi-exponential analysis methods for 1D and 2D data and example test problems and experiments. Regularized least-squares solutions provide production-quality outputs with robust stopping rules in ~5 and ~20 lines of code for 1D and 2D inversions, respectively. The software provides an open-architecture simple solution for transforming exponential decay data to the distribution of their decay lifetimes. Examples from magnetic resonance relaxation of a complex fluid, a Danish North Sea crude oil, and fluid mixtures in porous materials-brine/crude oil mixture in North Sea reservoir chalk-are presented. Developed codes may be incorporated in other software or directly used by other researchers, in magnetic resonance relaxation, diffusion, and imaging or other physical phenomena that require multi-exponential analysis.

Efficiency improvement for Ho3+/Pr3+co-doped 3 μm fiber laser in AlF3-based glass fiber

Over the past few decades, significant advancements have been made in the development of 3 μm fiber lasers utilizing Ho3+/Pr3+ doped fluoride fiber, particularly in terms of slope efficiency and output power. While achieving an efficiency of ∼15 % for the 3 μm laser in AlF3 fiber with a Ho3+/Pr3+ doping ratio of ∼10:1, further improvements are necessary to approach the Stokes efficiency limit of ∼40 %. Our study focused on the influence of the Ho3+/Pr3+ doping ratio on 3 μm laser efficiency. We conducted experiments on Ho3+/Pr3+ co-doped glass and fiber with doping ratios ranging from 1:0.01 to 1:1. Luminescence decay lifetime tests of the Ho3+: 5I6 and 5I7 energy levels in the Ho3+/Pr3+ doped AlF3 glass samples revealed the primary energy transfer progress that affected the 3 μm laser efficiency. When pumped by a 1150 nm Raman fiber laser, a maximum slope efficiency of 29.3 % at 3 μm was obtained in a 1mol%Ho3+/0.6mol%Pr3+ co-doped AlF3 Fiber.

Novel single phase warm white-emitting phosphor BaLaGaO4:Dy3+,Sm3+ with high thermal stability and color stability

In this study, new phosphors BaLaGaO4 (BLGO) doped with dysprosium (Dy3+) and samarium (Sm3+) ions were created using a high-temperature solid-state method. Characterizations with X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and elemental mapping revealed successful doping and uniform elemental distribution. Then the samples were tested for photoluminescence (PL) spectra, the results indicated that the BaLaGaO4:xDy3+ (BLGO:xDy3+) phosphors emitted strong blue and yellow light upon excitation at 350 nm. The emission peaks were located at 480 and 572 nm, respectively. By introducing different proportions of Sm3+ ions, the BaLaGaO4:0.04Dy3+,ySm3+ (BLGO:0.04Dy3+,ySm3+) samples could be excited at 365 nm, and enhancing the red emission component of the phosphor. Meantime, with increasing Sm3+ content, the correlated color temperature (CCT) decreased from 5507 to 3767 K. And the emission spectrum and decay lifetime of BLGO:0.04Dy3+,ySm3+ confirmed the energy transfer from Dy3+ to Sm3+. Furthermore, at 423 K, the luminous intensity of BLGO:0.04Dy3+,0.04Sm3+ retained 86 % of its strength at 298 K, and the chromaticity shift (ΔS) was only 0.00574, which indicated that the sample had excellent thermal stability and excellent color stability. Finally, using the prepared sample and a 365 nm light-emitting diode (LED) chip, a white light-emitting diode (WLED) was fabricated. The CCT of the manufactured WLED also showed a corresponding reduction (from 3423 to 2814 K). Moreover, under the working conditions of 3.4 V and 0.6A, the thermal imaging obtained after 90 min of WLED operation shows the stability of the packaged WLED at high temperature. These researches show that the phosphor has potential application value in indoor lighting technologies.

Investigation of photoluminescence properties of Eu3+ doped La(OH)3 nanopowder synthesized by combustion method

Pure and different doping percentages of Eu 3+ ion (2, 5, and 10 wt%) doped La(OH)3 nanoparticles were produced using the urea-assisted combustion method followed by a three-hour calcination at 800 °C. A pure hexagonal phase of La(OH)3 structure is confirmed using X-ray diffraction (XRD) results. The photoluminescence (PL) investigations of Eu-doped La(OH)3 nanoparticles revealed orange and red emissions from 5D0→7F1 and 5D0→7F2 transitions of Eu3+ ions with excitation wavelength 395 nm. The CIE coordinate represents the orange and red zone of the La(OH)3 sample doped with Eu3+ions. The CCT values obtained are 2145 K, 2469 K, and 2583 K also the decay lifetime is 0.273 ns, 0.266 ns, and 0.493 ns for 2, 5, and 10 wt% of Eu3+ ions. The results confirmed among the three dopant concentrations of Eu3+ doped La(OH)3 nanoparticles, the optimal concentration of 10 wt% Eu3+ ion can be used for red and orange emitting phosphors.

Prediction of mid-infrared 2.72 μm lasing in heavily Er3+-doped fluorotellurite glass

Fluorotellurite glasses heavily doped with Er3+ are prepared in less demanding conditions as compared with fluoride glasses. Specifically, the effects of PbF2 added in the system of AlF3–MgF2–CaF2–SrF2–BaF2–TeO2 (AMCSBYT) are systematically studied on the correlation between glass structure and mid-infrared (MIR) luminescent properties of Er3+. These PbF2-modified glasses with an improved thermal stability and a noticeably reduced phonon energy as compared with telluride glasses exhibit an intense MIR emission at 2.72 μm and a long radiative decay lifetime. Calculation and analysis based on the Judd-Ofelt theory provide deeper insights into the interdependence of luminescent properties and glass structure. Numerical simulation is conducted for a MIR fiber laser based on the experimental data derived from the proposed glass. The 2.72 μm lasing output of 0.68 W is predicted with a slope efficiency of 3.38 %. It is expected that the performance of the fiber laser can be further optimized such that the output power can be increased over 1.0 W. The results emphasize the potential of the PbF2-modified fluorotellurite glass as a promising gain material for 2.72 μm fiber lasers.

Judd-Ofelt analysis of Sm3+ doped Ca2LiMg2V3O12 phosphors: Unveiling luminescent and thermometric properties for multifunctional applications

This study investigated the luminescent and thermometric properties of pure and Sm³⁺-doped Ca₂LiMg₂V₃O₁₂ (CLMV) garnet-type vanadates synthesized by the solid-state reaction method. The synthesized materials, with varying Sm³⁺ concentrations (0.01–0.09 mol%), were comprehensively characterized using powder X-ray diffraction (PXRD) analysis to confirm their phase purity. Diffuse reflectance spectroscopy (DRS) measurements were employed to determine the band gap energy of both pure CLMV and CLMV:0.07Sm³⁺ samples. Photoluminescence (PL) excitation and emission spectra were recorded for the pure and Sm³⁺-doped CLMV phosphors using an excitation wavelength of 345 nm and monitoring the emission at 618 nm. These spectra revealed detailed information about the energy levels involved in light emission processes. An efficient energy transfer from the (VO₄)³⁻ groups to the Sm³⁺ ions was observed, exceeding 48%. This energy transfer process is crucial for achieving high-intensity luminescence in Sm³⁺-doped materials. Judd–Ofelt (J-O) theory was applied from the emission spectra and calculate the Judd–Ofelt intensity parameters, which govern the radiative properties of the Sm³⁺ ions. Based on the J-O analysis, the branching ratio (β) was estimated to be greater than 75%. This value, exceeding the threshold of 50% for display devices, signifies the suitability of the phosphor for solid-state lighting applications due to its efficient light emission. The thermal quenching behavior of both the Sm³⁺ ions and the (VO₄)³⁻ groups was further investigated to explore the optical thermometric characteristics of the Sm³⁺-doped CLMV phosphors. Notably, a maximum absolute sensitivity (Sa) of 0.35 K⁻1 and a relative sensitivity (Sr) of 2.55% K⁻1 were achieved, demonstrating the materials potential for non-contact optical temperature sensing applications. Lifetime decay analysis revealed double exponential decay behavior, indicating the presence of multiple luminescence centers within the phosphor. The average lifetime in the millisecond range further supports the suitability of these materials for practical applications. Finally, the CIE color coordinates, correlated color temperature (CCT), and color rendering index (CRI) values were also reported, providing insights into the colorimetric properties of the Sm³⁺-doped CLMV phosphors. These aspects are crucial for optimizing the materials for solid-state lighting applications.

Charge transfer dynamics in graphene quantum dot-porphyrin derivative nanohybrids appraised via experimental and theoretical calculations

This article is designed to unveil the electronic and spectroscopic property changes of electron withdrawing/releasing group substituted porphyrins, in porphyrin-graphene quantum dot nanohybrids via experimental and computational calculations. Herein, amino, methyl, fluoro & nitro derivatives of meso substituted Tetraphenylporphyrin referred as TAPP, TMPP, TFPP & TNPP respectively, are synthesized from the corresponding benzaldehydes. Charge transfer dynamics of their nanohybrid systems with graphene quantum dots are investigated by electronic spectroscopy, steady state fluorescence and lifetime decay analysis. Negative Gibb's free energy change and dynamic quenching constants stipulate a photoinduced electron transfer with dynamic quenching mechanism within the nanohybrids under scrutiny. Further the computational calculations with the aid of optimized geometries, scatter plots and energy decomposition analysis reflect the same experimental observations. Both experimental and computational studies show that the electron withdrawing group substituted porphyrins have higher interaction with GQD than the electron releasing group substituted porphyrins.

Luminescence studies and Judd Ofelt parameterization of Dy3+ activated La2(WO4)3 yellow phosphor

The synthesis and detailed luminescence studies of a series of La2-xDyx(WO4)3 (x = 0.02, 0.1, 0.2, 0.4, 0.6, 0.8) phosphors synthesized via microwave-assisted co-precipitation technique is reported in this paper. The XRD analysis confirmed that the phosphors were crystalized in a monoclinic structure with space group C2/c and FTIR analysis identified the characteristic vibrational modes. Morphological studies were conducted using FESEM analysis, and the EDS technique substantiated the effective incorporation of Dy3+ ions in La2(WO4)3. The photoluminescence excitation and emission spectra of varying concentrations of Dy3+ ions were recorded and an optimum concentration of 10% exhibited the highest intensity. The emission spectra of all phosphors were dominated by peaks at 484 nm and 574 nm. The radiative properties were evaluated using Judd-Ofelt analysis and the JO intensity parameters followed the trend Ω2 > Ω6 > Ω4. The gradual decrease in the decay lifetime value of 4F9/2 excited level with an increase in doping concentration elucidates concentration quenching phenomena due to dipole – quadrupole interaction. The emission data were also analyzed by calculating CIE coordinates and concluded that Dy3+ doped La2(WO4)3 phosphors have potential applications in yellow light generation.

Ultrafast Dynamics of Strong Near‐Field Coupled Localized and Delocalized Surface Plasmons

AbstractThis paper reports transient dynamics of strong near‐field coupling behavior of plasmons in a multilayer metal nanostructure that enables ultrahigh‐efficient optical switching. Particle plasmon on the top array units couples with localized/delocalized plasmons on the bottom Au film to produce dipolar and high‐order hybrid modes with nearly suppressed reflection. The mode coupling can be tuned from near‐field to far‐field regime readily mediated by the spacer thickness. The dipolar mode inherits the high dispersive property of the delocalized plasmon, but the higher‐order one shows limited dispersion. Transient spectroscopy illustrates both hybrid modes have a picosecond timescale redshift under on‐ and off‐resonance excitation. However, the higher‐order mode exhibits a longer decay lifetime than the dipolar one because of resonance characteristics and cavity properties. An ultrafast optical switching effect with a response time of τ = 3.2 ps and an ultrahigh efficiency of 5100 mOD mJ−1 cm2 is achieved under an extremely low pump fluence.

Modulation and Enhancement of Red Luminescence in Ca2GdSbO6: Eu3+ Phosphor by Co-Doping with Bi3.

The double perovskite structure of Ca2GdSbO6 as a fluorescent phosphor matrix material possesses a stable structure, making it an excellent candidate for a matrix material. In this study, single-doped Ca2GdSbO6: Eu3+ fluorescent phosphors and Bi3+ sensitized Ca2GdSbO6: Eu3+, Bi3+ fluorescent phosphor materials were synthesized using the high-temperature solid-state method. The luminescence of this phosphor is based on the 5D0→4F2 transition emission of Eu3+ ions, which occurs at 612nm. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) spectra, high-temperature fluorescence spectra, and fluorescence decay lifetimes to study the phase structure, optical properties, crystal structure, and chemical purity of the samples. The performance of the single-doped phosphor was significantly improved by the addition of Bi3+ sensitizer. The luminescence intensity increased by nearly 100% compared to Ca2GdSbO6: Eu3+ phosphor, with a quantum efficiency increase of 124%. The thermal quenching activation energy was found to be 0.299eV, and the luminescence intensity remained at 70.3% of room temperature at 453K. These results indicate that the co-doping of Bi3+ has a modulation and enhancement effect on the luminescence of Ca2GdSbO6: Eu3+ red phosphor, showing great potential for application in near-ultraviolet-excited white LED devices.

Luminescence and two-photon absorption assisted optical limiting properties of Ag-doped CdWO4 nanorods

The emerging demand for the fabrication of nonlinear optical materials with high limits of optical power is obvious in nonlinear optics due to their wide application in photonic devices. We report the linear and third-order nonlinear optical properties of Ag-doped CdWO4 nanorods and their dependence on Ag-doping concentration. CdWO4 nanorods with different Ag concentrations were synthesized by the chemical precipitation method and characterized by UV–Vis absorption, X-ray diffraction (XRD), Raman, Photoluminescence and its lifetime studies, X-ray Photoelectron spectroscopy and Transmission Electron Microscopy (TEM). The introduction of Ag ions has led to an increased redshift in the CdWO4 absorption spectra extended into longer wavelength bands, thus enhancing optical absorption within the visible range. The XRD pattern showed that the nanorods crystallized in a monoclinic wolframite structure. The incorporation of Ag in CdWO4 decreases the luminescence emission intensity due to surface quenching effect. Luminescence lifetime measurement reveals the longer decay lifetime for Ag-doped CdWO4 nanorods due to the reduction of density of defects and deep trap state. The nonlinear optical behaviour of the nanorods was investigated by an Open aperture Z-scan technique at 532 nm using pulsed wave Nd: YAG laser. Experimental results showed that reverse saturable absorption is responsible for the observed nonlinearity in the nanorods. The addition of Ag can significantly improve the nonlinear absorption coefficient and optical limiting effects of CdWO4 which can be used as a potential material in nonlinear optical devices.

Thermally stable Tb3+/Sm3+-doped Lu2O2S phosphors with tunable multicolor luminescence under light and X-ray excitation

Lu2O2S has high density, high melting temperature, and favorable thermal stability, making it an excellent matrix material for rare earth luminescence and X-ray sensitization screens. However, achieving high quality fluorescent powders with high crystal quality on a large scale is still challenging. By employing an optimized solid phase approach, Lu2O2S:Tb3+/Sm3+phosphors with a hexagonal shape and uniform particle size and showing high crystallization have been successfully synthesized. Spectral analysis reveals energy interaction between Sm3+ and Tb3+ in the Lu2O2S system (multistage interaction), indicated by spectral overlap, relative changes in luminescence intensity, and lifetime decay. By changing the excitation wavelength and dopant concentration, multicolor phosphors such as yellow-–green, orange–red, and orange–yellow could be created. Temperature-dependent emission spectroscopy shows that the system shows good luminescence performance even at high temperatures. X-ray excitation spectroscopy further confirm that the phosphors emit different colors (yellow, green and red) depending on the doping concentrations of Tb3+ and Sm3+ ion, indicating that the system has wide application potential in color displays and other relevant fields.

Search for heavy dark matter from dwarf spheroidal galaxies: leveraging cascades and subhalo models

The Fermi Large Area Telescope (Fermi-LAT) has been widely used to search for Weakly Interacting Massive Particle (WIMP) dark matter signals due to its unparalleled sensitivity in the GeV energy band. The leading constraints for WIMP by Fermi-LAT are obtained from the analyses of dwarf spheroidal galaxies within the Local Group, which are compelling targets for dark matter searches due to their relatively low astrophysical backgrounds and high dark matter content. In the meantime, the search for heavy dark matter with masses above TeV remains a compelling and relatively unexplored frontier. In this study, we utilize 14-year Fermi-LAT data to search for dark matter annihilation and decay signals in 8 classical dwarf spheroidal galaxies within the Local Group. We consider secondary emission caused by electromagnetic cascades of prompt gamma rays and electrons/positrons from dark matter, which enables us to extend the search with Fermi-LAT to heavier dark matter cases. We also update the dark matter subhalo model with informative priors respecting the fact that they reside in subhalos of our Milky Way halo aiming to enhance the robustness of our results. We place constraints on dark matter annihilation cross section and decay lifetime for dark matter masses ranging from 103 GeV to 1011 GeV, where our limits are more stringent than those obtained by many other high-energy gamma-ray instruments.

Crystal Growth, Photoluminescence and Radioluminescence Properties of Ce3+-Doped Ba3Y(PO4)3 Crystal

Inorganic scintillation crystals have been widely used in applications of high-energy physics, nuclear medical imaging, industrial nondestructive inspection, etc. In this work, a single crystal Ba3Y(PO4)3 (BYP) with 1.0 at% Ce3+-doping concentration was first grown by the Czochralski method, and the electronic structure was calculated using first principles based on density functional theory. In addition, a series of Ce3+-doped BYP phosphors were synthesized, and the fluorescence emission under UV excitation was measured through low-temperature spectroscopy, containing double-peaked emission from 5d–4f transition and self-trapped exciton recombination. A comparison of the UV and X-ray-excited fluorescence spectra reveals the existence of oxygen vacancies as well as F+ centers in the crystal. The air annealing of the crystal effectively reduces the thermoluminescence defects but reduces the emission intensity under UV or X-ray excitation. The BYP:Ce crystal shows a fast decay lifetime of 15.5 ns, and the fast component is as short as 8 ns. The results show that the Ce3+-doped BYP crystal has potential as a kind of scintillator with fast decay properties.

Synthesis of near-infrared-activated YF3:Yb3+, Tm3+/Bi2MoO6 upconversion photocatalytic materials for the photocatalytic degradation of antibiotics based on fluorescence resonance energy transfer

Photocatalytic degradation of pollutants, an ecofriendly technology, is widely used for environmental remediation. However, the design and synthesis of photocatalytic materials for near-infrared light photocatalysis are challenging. In this study, an upconversion photocatalyst with fluorescence resonance energy transfer (FRET), YF3:Yb3+, Tm3+/Bi2MoO6 (YFYT/BMO), was developed and synthesised based on rare-earth upconversion luminescence. YFYT converted near-infrared (NIR) light into blue–violet light via upconversion. The rapid decay of the fluorescence lifetime of YFYT/BMO at 478 nm (Tm3+:1G4-3H6) verified that FRET efficiently occurred between YFYT and BMO. The degradation rate of tetracycline by YFYT/BMO was 2.6 times higher than that by BMO under NIR light. A great enhancement of 42.1 % on the tetracycline degradation efficiency was achieved in YFYT/BMO compared with pure BMO within 90 min of visible-NIR irradiation. This study provides a basis for developing and designing rare-earth upconversion photocatalytic materials that can achieve excellent photocatalytic degradation of antibiotics using NIR light for environmental remediation.