Downconversion Emission Research Articles

A Synergy Approach to Enhance Upconversion Luminescence Emission of Rare Earth Nanophosphors with Million-Fold Enhancement Factor

Lanthanide (Ln3+)–doped upconversion nanoparticles (UCNPs) offer an ennormous future for a broad range of biological applications over the conventional downconversion fluorescent probes such as organic dyes or quantum dots. Unfortunately, the efficiency of the anti−Stokes upconversion luminescence (UCL) process is typically much weaker than that of the Stokes downconversion emission. Albeit recent development in the synthesis of UCNPs, it is still a major challenge to produce a high−efficiency UCL, meeting the urgent need for practical applications of enhanced markers in biology. The poor quantum yield efficiency of UCL of UCNPs is mainly due to the fol-lowing reasons: (i) the low absorption coefficient of Ln3+ dopants, the specific Ln3+ used here being ytterbium (Yb3+), (ii) UCL quenching by high−energy oscillators due to surface defects, impurities, ligands, and solvent molecules, and (iii) the insufficient local excitation intensity in broad-field il-lumination to generate a highly efficient UCL. In order to tackle the problem of low absorption cross-section of Ln3+ ions, we first incorporate a new type of neodymium (Nd3+) sensitizer into UCNPs to promote their absorption cross-section at 793 nm. To minimize the UCL quenching induced by surface defects and surface ligands, the Nd3+-sensitized UCNPs are then coated with an inactive shell of NaYF4. Finally, the excitation light intensity in the vicinity of UCNPs can be greatly enhanced using a waveguide grating structure thanks to the guided mode resonance. Through the synergy of these three approaches, we show that the UCL intensity of UCNPs can be boosted by a million−fold compared with conventional Yb3+–doped UCNPs.

Lanthanide ions doped nonhygroscopic La2Mo3O12 microcrystals based on multimode luminescence for optical thermometry

The non-contact thermometry based on fluorescence intensity ratio of phosphors has been extensively investigated owing to its high sensitivity and fast response. However, most of them only use a single mode of upconversion or downconversion emission for temperature sensing and ignore the affection of the humidity. In this work, the Yb/Er ions doped La2Mo3O12 microcrystals with nonhygroscopic property and multimode luminescence have been developed for temperature sensing. The optical thermometer could be based on not only luminescent intensity ratio of upconversion and downconversion, but also average fluorescence decay lifetime. The maximal absolute sensitivity can reach up to 6.2% K−1 and the maximal relative sensitivity is 1.63% K−1. Moreover, the fluorescence emission intensity of the doped La2Mo3O12 microcrystals will not be affected by the humidity compared to some doped molybdate and tungstate. These excellent performances suggest that the La2Mo3O12:Yb/Er microcrystals possess great potential for practical applications in temperature sensing.

Enrichment of Crystal Field Modification via Incorporation of Alkali K+ Ions in YVO4:Ho3+/Yb3+ Nanophosphor and Its Hybrid with Superparamagnetic Iron Oxide Nanoparticles for Optical, Advanced Anticounterfeiting, Uranyl Detection, and Hyperthermia Applications.

In this work, we report a polyol route for easy synthesis of upconversion (UC) phosphor nanoparticles, YVO4:Ho3+-Yb3+-K+, which enables large-scale production and enhancement of luminescence. Upon 980 nm laser excitation, the UC emission spectrum shows a sharp bright peak at ∼650 nm of Ho3+ ion; and the luminescence intensity increases twofold upon K+ codoping. Upon 300 nm excitation, the downconversion emission spectrum shows a broad peak in the 400–500 nm range (related to the charge transfer band of V–O) along with Ho3+ peaks. In addition, the polyethylene glycol-coated UC nanoparticles are highly water-dispersible and their hybrid with Fe3O4 nanoparticles shows magnetic-luminescence properties. A hyperthermia temperature is achieved from this hybrid. Both UC and hybrid nanoparticles show interesting security ink properties upon excitation by a 980 nm laser. The particles are invisible in normal light but visible upon 980 nm excitation and are useful in display devices, advanced anticounterfeiting purposes, and therapy of cancer via hyperthermia and bioimaging (since it shows red emission at ∼650 nm). Using UC nanoparticles, detection of uranyl down to 20 ppm has been achieved.

Brilliant Nonlinear Optical Response of Ho3+ and Yb3+ Activated YVO4 Nanophosphor and Its Conjugation with Fe3O4 for Smart Anticounterfeit and Hyperthermia Applications.

YVO4:Ho3+/Yb3+ nanophosphors prepared by an effective polyol-mediated route show dual-mode behavior in photoluminescence. Upon 980 nm excitation, the upconversion red emission spectrum exhibits a bright red peak at ∼650 nm, characteristic of the electronic transition of the Ho3+ ion via involvement of two-photon absorption, which has been confirmed by the power-dependent luminescence study. Moreover, at 300 nm excitation, downconversion emission peaks are observed at 550, 650, and ∼755 nm. The nonradiative resonant energy transfer occurs from the V–O charge transfer band to Ho3+ ions, resulting in an improved emission of Ho3+ ions. Moreover, polyethylene glycol-coated nanoparticles make it suitable for water dispersibility; and these particles are conjugated with Fe3O4 nanoparticles to form magnetic–luminescent hybrid nanoparticles. Highly water-dispersible magnetic–luminescent hybrid material attained the hyperthermia temperature (∼42 °C) under an applied AC magnetic field. The specific absorption rate value is found to be high (138 W/g), which is more than that of pure superparamagnetic Fe3O4 nanoparticles. At 300 nm excitation, the high quantum yield value of ∼27% is obtained from YVO4:Ho3+/Yb3+, which suggests that it is a good phosphor material. By employing the neutron activation analysis technique, it is shown that nanophosphor particles can absorb Au3+ up to the ppm level. Interestingly, such nanophosphor also shows the potentiality for anticounterfeiting applications.

Facile synthesis and size-dependent luminescence of gadolinium compounds with multiform morphologies and tunable particle sizes

A series of monodisperse size-controllable amorphous Gd(OH)CO3 spherical particles with good dispersity have been prepared by a simple homogeneous precipitation route with ethylene glycol (EG) as auxiliary solvent. The average diameters of precursor spheres can be tuned in the range of 70–220 nm by simply changing the volume ratios of EG/H2O in the solvent. In general, the particle size of the spherical particles gradually increases by enhancing the proportion of H2O for the mixing solvent of EG/H2O. Moreover, the long flakes and sheet-like microstructures of the crystalline precursors [Gd2O(CO3)2∙H2O] are obtained by increasing reaction temperature or prolonging reaction time. Thus, the multiform precursors with tunable morphologies and particle sizes have been achieved by systematically adjusting the reaction conditions. It is worth pointing out that the corresponding gadolinium oxide (Gd2O3) products perfectly inherit the good morphology, unifomity, and dispersity of the precursor particles except for a shrinkage in diameters after an annealing process in air, resulting in the uniform and well-dispersed Gd2O3 spheres with tunable particle sizes (50–180 nm). The lanthanide ions (Ln3+) doped samples exhibit their corresponding characteristic down-conversion (DC) or up-conversion (UC) multicolor emissions under UV or NIR excitation. The size-dependent luminescence properties of the Ln3+-doped phosphors are also investigated in detail. The as-manufactured LED device prepared by the phosphor and LED chip can exhibit characteristic emission of activator ion, which directly prove the potential applications of the phosphors in LEDs and optoelectronics. Furthermore, the as-proposed synthesis strategy may provide some insight for the design and fabrication of other rare earth functional materials with controllable morphology and particle sizes.

The effects of dopant concentration and excitation intensity on the upconversion and downconversion emission processes of β-NaYF4:Yb3+,Er3+ nanoparticles

The effects of dopant concentration and excitation intensity on the upconversion and downconversion emission processes of β-NaYF4:Yb3+,Er3+ nanoparticles

Photoluminescence of green nanophosphors Sr2MgSi2O7 doped with Tb3+ under 374-nm excitation* *Project supported by the National Natural Science Foundation of China (Grant No. 11004092) and the Foundation of Science and Technology Department of Liaoning Province, China (Grant No. 201602455).

A series of Sr2MgSi2O7:Tb3+ nanophosphors is prepared using a high-temperature solid-state reaction. The x-ray diffraction patterns show that the crystal structure of the sample is not significantly affected by Tb3+ ions. However, the images of the scanning electron microscope illustrate that the average size of nanoparticles becomes larger with the increase of Tb3+ concentration. Unlike earlier investigations on down-conversion emission of Tb3+ ion excited by deep ultraviolet light, in this work, the photoluminescence characteristics of Sr2MgSi2O7 nanophosphors doped with different Tb3+ concentrations are analyzed under 374-nm excitations. The intense green emission at 545 nm is observed at an optimal doping concentration of 1.6 mol%. The main reason for the concentration quenching is due to the electric dipole–electric dipole interaction among Tb3+ ions.

Efficient coupling of down-converted photon pairs into single mode fiber

We present the analysis of the down-conversion emission profile from a critically phase-matched type-I nonlinear crystal. The emission profile of the down-conversion modes shows asymmetry in cylindrical coordinate system due to the birefringent effects of the nonlinear crystal, i.e. pump walk-off. This effect leads to reduced collection of the pairs from the source to the single mode fiber, which limits the brightness as a function of the crystal length. We propose a method to improve the symmetry of the down-conversion modes by inserting a lens off-centered with respect to the optical axis. Our theoretical and experimental results show that the asymmetry of the system increases with the crystal length by L0.5, and the brightness is proportional to crystal length by L0.72 and L0.91 for uncorrected and corrected down conversion mode profiles, respectively. The proposed method allows more efficient use of photon pair sources in terms of brightness which is to be used in quantum optics applications.

Structural evolution, crystallization behaviour and mid-infrared emission properties in Yb/Ho codoped oxyfluoride germanosilicate glass ceramics with varied Si/Ge ratio

Changes in glass structure and crystallization behaviour from oxyfluoride silicate glass to oxyfluoride germanate glass were studied by modifying the ratio of Si/Ge in oxyfluoride germanosilicate glass ceramics, and transparent glass ceramic with low light scattering and efficient mid-infrared emissions were obtained. The NaYF4 nanocrystals crystallization ability of oxyfluoride glass was decreased with the increase in Ge content, which can be attributed to the weakened oxide and fluoride phase separation in GeO2-rich glass. Upconversion and down-conversion emission spectra together with Ho3+: 5I6 energy level fluorescent decay curves have been discussed for SiO2-rich glass ceramics and GeO2-rich glass ceramics, in which the fluoride crystallization induced the decrease of multi-phonon non-radiative decay rates plays the main role in the energy transfer processes. The influence of Si/Ge ratio on 2 μm and 3 μm fluorescent emissions in glasses and glass ceramics, and its link with glass network structural changes were discussed. The optimized Yb/Ho codoped oxyfluoride germanosilicate glass ceramic with low light scattering, high peak emission cross section(11.18 × 10−21cm2) and maximum gain coefficient (1.387 cm−1) at 2888 nm provides a potential application in the development of new 3 μm laser devices based on transparent oxyfluoride glass ceramic materials.

Down-shifting and down-conversion emission properties of novel CdO–P2O5 invert glasses activated with Pr3+ and Pr3+/Yb3+ for photonic applications

The down-shifting and down-conversion emission properties of novel CdO–P2O5 invert glasses activated with Pr3+ and Pr3+/Yb3+ were respectively studied. The down-shifting emission spectra of Pr6O11 singly doped glasses upon 443 nm excitation (Pr3+: 3H4 → 3P2), displayed the feature Pr3+ transitions in the visible and near-infrared (NIR) regions, reaching the optimum intensity at 0.7 and 0.3 mol% of Pr6O11, respectively. The emission tonality can be adjusted from the reddish-orange to orange-pink region, depending on the Pr6O11 content. Such fact coupled with the superposition of the blue light excitation might be attractive for white light-emitting diodes (W-LEDs) applications. The cross-relaxation processes involved between Pr3+-Pr3+ pairs seem to be mediated by an electric quadrupole-quadrupole interaction, as revealed by the Inokuti-Hirayama model. The emission spectra of the Pr6O11 and Yb2O3 doped glasses upon 443 nm excitation showed, in addition to the Pr3+ related transitions, a band at 977 nm associated with the Yb3+: 2F5/2 → 2F7/2 transition, which gradually grows at expenses of non-radiative energy transfer from Pr3+. This process might lead to a down-conversion (quantum cutting) emission with theoretical quantum efficiencies up to 144%. Analysis complemented by the Inokuti-Hirayama or Dexter model revealed that the non-radiative Pr3+ → Yb3+ energy transfer process arisen from Pr3+: 3P0 and 1D2 levels are most likely dominated by electric dipole-dipole and quadrupole-quadrupole interactions, respectively. The global emission properties suggest that the Pr3+ and Pr3+/Yb3+ activated CdO–P2O5 invert glasses might be interesting for WLEDs and crystalline silicon (c-Si) solar cell applications.

Multifunctional up/down-conversion luminescence of core/shell nanocomposite for self-monitored heating and fluorescence imaging

The simultaneous realization of real-time thermal sensing at physiological temperature range and fluorescence imaging during photothermal therapy (PTT) via single-component biocompatible nanocomposite could furthest avoid collateral damage and enhance phototherapeutic effect, which, up to now, is of great interest and still in a formidable challenge. Under near-infrared (NIR) light irradiation, Nd3+-doped nanoparticles (NPs) have emerged as candidates with outstanding properties such as down-conversion emissions in biological window (BW) and capable of light-to-heat conversion. However, these two properties associated with Nd3+ doping concentrations induce opposite changing trend and difficult to combine within one single nanocomposite. In this work, for breaking through the obstacles, core/shell NaLuF4:1%Nd@NaLuF4@NaLuF4:15%Yb,3%Er@NaLuF4:15%Yb@NaLuF4:85%Nd 808 nm light-triggered co-enhancement up/down-conversion luminescence (UCL/DCL) nanocomposite was purposely designed with efficient heating, thermal sensing and fluorescence imaging concurrently. The core emits high quantum yield (QY) DCL in BW while the outermost layer could convert the absorbed photon into thermal energy and also transfer a fraction of energy inwards to internal layer with exciting the UCL (Nd→Yb→Er) for thermal sensing via thermally coupled levels 2H11/2/4S3/2 of Er using the fluorescence intensity ratio (FIR) method. The simultaneously enhanced UCL/DCL and thermal effect in the engineered nanocomposite are satisfactorily realized due to suppressing the interionic quenching owing to the inert two layers NaLuF4 and NaLuF4:15%Yb. Such smart designed nanocomposite has potential application on PTT-based noninvasive cancer therapy.

The effects of dopant concentration and excitation intensity on the upconversion and downconversion emission processes of β-NaYF4:Yb3+,Er3+ nanoparticles

The optimal dopant concentration in UCNPs for simultaneous visible and NIR luminescence was determined by controlling the sensitizer-to-activator ratio while maintaining the total amount of dopants.

Dual mode emissions with enhanced green up-conversion luminescence by Gd3+doping and down-conversion from Eu3+in NaMnF3:Yb,Er@NaGdF4:Eu

NaMnF3:Yb,Er and NaMnF3:Yb,Er@NaGdF4:xEu (x = 0, 0.3, 0.6, and 0.9) samples were synthesized by a simple hydrothermal method. The as-obtained NaMnF3:Yb,Er particles show a single red emission under the irradiation of infrared light (980 nm), due to the energy exchange transfer process between Mn2+ ions and Er3+ ions. Notably, further growth of NaGdF4:Eu on the basis of NaMnF3:Yb,Er enhanced the green up-conversion luminescence of Er3+ ions, which gradually shifted from red to green with the increase of the Gd3+ ion doping amount. In addition, NaMnF3:Yb,Er@NaGdF4:Eu exhibits red color under ultraviolet excitation (397 nm). These results provide a possible means for controlling the luminescence properties of the lanthanide doped up-conversion system. The luminescent film synthesized with NaMnF3:Yb,Er@NaGdF4:Eu can show different luminescent colors under different light irradiation (near infrared and ultraviolet), which indicates that they have potential applications in multi-mode anti-counterfeiting.

Estimating dynamic vascular perfusion based on Er-based lanthanide nanoprobes with enhanced down-conversion emission beyond 1500 nm.

Peripheral artery disease (PAD) is a common, yet serious, circulatory condition that can increase the risk of amputation, heart attack or stroke. Accurate identification of PAD and dynamic monitoring of the treatment efficacy of PAD in real time are crucial for optimizing therapeutic outcomes. However, current imaging techniques do not enable these requirements.Methods: A lanthanide-based nanoprobe with emission in the second near-infrared window b (NIR-IIb, 1500-1700 nm), Er-DCNPs, was utilized for continuous imaging of dynamic vascular structures and hemodynamic alterations in real time using PAD-related mouse models. The NIR-IIb imaging capability, stability, and biocompatibility of Er-DCNPs were evaluated in vitro and in vivo.Results: Owing to their high temporal-spatial resolution in the NIR-IIb imaging window, Er-DCNPs not only exhibited superior capability in visualizing anatomical and pathophysiological features of the vasculature of mice but also provided dynamic information on blood perfusion for quantitative assessment of blood recovery, thereby achieving the synergistic integration of diagnostic and therapeutic imaging functions, which is very meaningful for the successful management of PAD.Conclusion: Our findings indicate that Er-DCNPs can serve as a promising system to facilitate the diagnosis and treatment of PAD as well as other vasculature-related diseases.

Tunable dual-mode photoluminescences from SrAl2O4: Eu/Yb nanofibers by different atmospheric annealing

One-dimensional Eu/Yb co-doped SrAl2O4 nanofibers were successfully synthesized via an electrospinning technique. The morphologies, crystal structures, and chemical valences were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), respectively. The results revealed that the valence of Eu ions was primary trivalent (Eu3+) after annealing in oxygen ambient (air), and the red up-conversion (UC) luminescence was observed which was derived from 5D0–2 to ground state 7FJ (J = 0–6) of Eu3+ ions. While they evolved to bivalent (Eu2+) after annealing in a reduced (H2/Ar) ambient, showing green down-conversion (DC) luminescence under the exposure of 365 nm, which was ascribed to Eu2+ 4f-5d allowed transition. The mixed valence of Eu2+/Eu3+ could be realized through a partially oxidation in air again, strikingly, resulting in dual-mode UC and DC. Herein, we demonstrate the tunable dual-mode UC and DC emission performance in SrAl2O4: Eu/Yb nanofibers through selective annealing processes. Consequently, the synthesized SrAl2O4: Eu/Yb nanofibers may offer potentials applications towards multifunctional luminescent occasion.

Ultrabroadband Tuning and Fine Structure of Emission Spectra in Lanthanide Er-Doped ZnSe Nanosheets for Display and Temperature Sensing.

Realizing multicolored luminescence in two-dimensional (2D) nanomaterials would afford potential for a range of next-generation nanoscale optoelectronic devices. Moreover, combining fine structured spectral line emission and detection may further enrich the studies and applications of functional nanomaterials. Herein, a lanthanide doping strategy has been utilized for the synthesis of 2D ZnSe:Er3+ nanosheets to achieve fine-structured, multicolor luminescence spectra. Simultaneous upconversion and downconversion emission is realized, which can cover an ultrabroadband optical range, from ultraviolet through visible to the near-infrared region. By investigating the low-temperature fine structure of emission spectra at 4 K, we have observed an abundance of sublevel electronic energy transitions, elucidating the electronic structure of Er3+ ions in the 2D ZnSe nanosheet. As the temperature is varied, these nanosheets exhibit tunable multicolored luminescence under 980 and 365 nm excitation. Utilizing the distinct sublevel transitions of Er3+ ions, the developed 2D ZnSe:Er3+ optical temperature sensor shows high absolute (15.23% K-1) and relative sensitivity (8.61% K-1), which is superior to conventional Er3+-activated upconversion luminescent nanothermometers. These findings imply that Er3+-doped ZnSe nanomaterials with direct and wide band gap have the potential for applications in future low-dimensional photonic and sensing devices at the 2D limit.

Valley depolarization in downconversion and upconversion emission of monolayer WS2 at room temperature

Abstract Benefiting from strong photon–exciton and phonon–exciton interactions in atomic thickness, transition metal dichalcogenides (TMDCs) are viewed as one promising platform for exploring elementary excitonic photoluminescence (PL) and intrinsic spin–valley properties at the monolayer limit. Despite well-studied Stokes downconversion (DC) PL, the anti-Stokes upconversion (UC) PL has been recently reported in TMDC monolayers, which mainly focus on UC mechanisms while detailed valley-related dynamical processes are unwittingly less concerned. Here, we carry out an in-depth investigation on both DC and UC emission features of monolayer WS2 at room temperature, where UC PL persists with energy gain up to 190 meV. The PL excitation and power-dependent experiments clearly distinguish the origins of DC PL and UC PL, which refer to saturated absorption and phonon-assisted transition from charged trions to neutral A-excitons. And contrast valley properties are observed in DC and UC scenarios with polarization-resolved PL and pump–probe measurements. According to the experimental facts, phenomenological dynamical DC and UC scenarios are modeled with intervalley depolarization taken into consideration, in which intermediates from spontaneous intervalley depolarization account for the observed emission and valley properties. This work can help understand the light–matter interactions and valley properties in monolayer TMDCs.

Excitation induced enhancement of spectral response and energy transfer mechanisms in Fe/Sm modified ZnO phosphors

The present study aims to analyze the tunability of photonic emissions as a function of excitation wavelengths in Fe/Sm co-doped ZnO phosphors. We have investigated the up-conversion (UC) and down-conversion (DC) luminescences in detail along with possible channels for energy transfer and their local electronic structures. These phosphors are polycrystalline with a hexagonal wurtzite structure, and the co-doping of Fe/Sm ions leads the 3D-pyramid like morphology of the ZnO to transform in flower-shaped nanorods. Further, from the UV–Vis spectra, it is found that bandgap contracts due to the formation of defects. The DC emission spectra (λex = 325 nm) show an enhancement of polychromatic emission as a function of the Sm concentration and tune from orange to red along with the transition from the warm to cool region in the Commission International de l'Eclairage 1931 XY spectral chromaticity coordinates. X-ray absorption spectra confirm the presence of Fe2+/Fe3+ ions and Sm3+ ions. Using the decay kinetics and transfer efficiencies, the energy transfer between the host defect levels and dopant ions is explained with the help of the energy level diagram. The UC emission spectra (λex = 980 nm) exhibit monochromatic red emission along with a strong near-infrared emission lying in the cool region with 100% color purity. These phosphors are expected to find applications in solid-state lighting applications, optoelectronics, and biomedical engineering, etc.

Luminescent anti-reflection coatings based on down-conversion emission of Tb3+-Yb3+ co-doped NaYF4 nanoparticles for silicon solar cells applications

To improve energy conversion efficiency (Eff) of silicon solar cells, luminescent down-conversion (DC) is an effective approach to adjust solar spectrum by converting ultraviolet light to visible and near-infrared light. In this paper, Tb3+- Yb3+ co-doped NaYF4 phosphors (DCNPs) were successfully synthesized by a simple solvothermal method. It was confirmed from the strong photoluminescence excitation (PLE) and photoluminescence (PL) emission peaks that the energy transfer occured between Tb3+ and Yb3+ ions. The DCNPs were added in the SiO2 sol-gel to prepare anti-reflection coatings with DC performance, enhancing the visible and near-infrared region transmittance which matched with the band gap of silicon. An optimized short-circuit current density (Jsc) of 33.39 mA/cm2 and a relatively enhanced Eff of 6.74% were achieved in the silicon solar cells with the bi-functional film. These results indicated the availability of anti-reflection coating with DCNPs for improving energy conversion efficiency of silicon solar cells.

Controllable synthesis and luminescence properties of NaYF4@YOF composite microcrystals with multiform morphologies

A variety of α-NaYF4@YOF composites with diverse morphologies and particles sizes have been fabricated via an easy-to-operate approach. First of all, the YB(OH)4CO3 precursor was obtained by a urea-based homogeneous precipitation route. Subsequently, the uniform and well-dispersed β-NaYF4 microcrystals with a variety of crystal shapes were synthesized by a simple hydrothermal process. The morphology and particle size of the β-NaYF4 samples can be adjusted in a controlled manner by simply tuning the reaction temperature and time, feeding molar ratio of precursor/NaF, or total amount of the reactants. Finally, the β-NaYF4 microcrystals converted to α-NaYF4@YOF composites which inherited the morphology and dispersity of the hydrothermal products after an annealing process in air. Upon UV or NIR excitation, the as-synthesized lanthanide ions Ln3+ (Eu3+, Tb3+, Yb3+/Er3+, Yb3+/Ho3+) doped α-NaYF4@YOF samples show the intense characteristic down-conversion (DC) or up-conversion (UC) multicolor emissions. Moreover, the calcination process not only broadens the excitation range but also improves the emission efficiency of the phosphors due to the enhanced crystallintiy and formation of YOF shell. The as-synthesized Ln3+-doped luminescent materials may find potential applications in fields of color displays, optoelectronic devices, and light-emitting diodes (LEDs).