Effect of Tb3+ and Ce3+ co-doping on the structural stability and photoluminescence properties of hexagonal boron nitride phosphors

Effect of Tb3+ and Ce3+ co-doping on the structural stability and photoluminescence properties of hexagonal boron nitride phosphors | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Effect of Tb 3+ and Ce 3+ co-doping on the structural stability and photoluminescence properties of hexagonal boron nitride phosphors Lunshuai Nie, Kai Jia, Hongguang Guo, Jiaqin He, Zhehui Weng, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3872075/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 23 Mar, 2024 Read the published version in Journal of Fluorescence → Version 1 posted 7 You are reading this latest preprint version Abstract In the paper, we have successfully prepared hexagonal boron nitride (h-BN) phosphors with melamine as the nitrogen source. The X-ray powder diffraction patterns confirm that the sample possesses a hexagonal crystal structure within the P m2 space group. It is interesting that the co-doping combination of Tb 3+ and Ce 3+ can markedly enhance the threshold concentration of doped activators within the limited solid solution of h-BN phosphors. Under 302 nm excitation, the h-BN:Ce 3+ phosphors exhibit broadband blue light emission at 406 nm. In h-BN:Tb 3+ , Ce 3+ phosphors, the co-doping of Ce 3+ not only ensures high phase purity but also results in strong green light emission. The energy transfer efficiency from Ce 3+ to Tb 3+ is about 55%. The fluorescence lifetime increases with the increase of Ce 3+ and Tb 3+ concentration, and the fluorescence lifetime of h-BN:0.025Tb 3+ , 0.05Ce 3+ phosphor reached 2.087 ms. Additionally, the h-BN:0.025Tb 3+ , 0.05Ce 3+ phosphor exhibits excellent thermal performance with an activation energy value of 0.2825 eV. Moreover, the photoluminescence quantum yield of the sample exceeds 52%. Therefore, the h-BN:Tb 3+ , Ce 3+ samples can be used as green phosphors for solid state lighting and fluorescent labeling. Hexagonal boron nitride Co-doping Ce3+ and Tb3+ Energy transfer Green phosphor Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1. Introduction In recent years, solid state lighting have emerged as a next-generation lighting source, surpassing incandescent and fluorescent lamps in terms of efficiency, lifetime, and energy consumption [ 1 – 3 ]. Currently, the combination of light-emitting diodes (LEDs) chips and phosphor has become the most crucial approach to achieving commercialized solid state lighting [ 4 ]. Furthermore, 60–100% of the white light of white LEDs comes from phosphors, so it is especially important to search for high-quality phosphors [ 5 ]. YAG:Ce 3+ yellow phosphors with a garnet crystal structure have been widely used in commercialized white LEDs [ 6 ]. However, the emission band of YAG: Ce 3+ yellow phosphors lacks red-emitting components, resulting in white LEDs with higher correlated color temperature (CCT) and lower color rendering index (CRI) [ 7 ]. As a result, researchers have shifted their focus towards green and red phosphors to improve the optical quality of white LEDs, such as Y 2 O 3 :Eu 3+ and β-SiAlON:Eu 2+ [ 8 ]. Nitride and oxide nitride phosphors doped with rare earth activators have gained significant attention due to their excellent visible light emission and resistance to luminescence thermal quenching [ 9 ]. More and more phosphors with nitride as the matrix have been prepared, and used as light conversion materials for white LEDs. For example, Wagatha P reported a red nitride phosphor α-Sr 2 [MgAl 5 N 7 ]: Eu 2+ with a luminous efficiency 1.2 to 1.5 times higher than mainstream red phosphors like (Ca, Sr)AlSiN 3 :Eu 2+ [ 10 , 11 ]. Additionally, nitride phosphors exhibit high thermal decomposition temperature and strong emission at high temperature, making them particularly suitable for high-power white LEDs [ 12 ]. Most nitride phosphors possess broad excitation bands that can be utilized for ultraviolet LED chips or blue LED chips. For instance, LiSi 2 N 3 phosphors doped with Eu 2+ or Ce 3+ have an excitation band ranging from 320 to 460 nm [ 13 ]. The nitride matrix can offer a strong crystal field to the activated ions, resulting in phosphors with various emitting colors. For example, Sr[Li 2 Al 2 O 2 N 2 ]:Eu 2+ features narrow-band emission at 614 nm, and CaAlSiN 3 :Eu 2+ phosphors exhibit red emission peaking at 649 nm [ 14 , 15 ]. Additionally, AlN:Tb 3+ , Eu 3+ nitride phosphors can emit different color light ranging from green to red [ 16 ]. Wang reports on a green phosphor, SrLuSi 4 N 7 :Ce 3+ , Tb 3+ , capable of tuning its color under ultraviolet excitation for use in white LEDs [ 17 ]. Binary nitrides, known for their straightforward structure and wide bandgap, have gained attention as matrices for nitride phosphors, including rare earth ion-doped GaN, AlN, and Si 3 N 4 phosphors [ 18 – 24 ]. Hexagonal boron nitride (h-BN) possesses a wide bandgap of approximately 5.2 eV and outstanding thermochemical stability, and has been identified as an ideal host material for inorganic phosphors [ 25 – 28 ]. However, there have been few articles on h-BN phosphors except for Eu 3+ and Ce 3+ doped h-BN [ 29 – 32 ]. Tb 3+ doped phosphors have poor absorption in the ultraviolet region due to the forbidden 4 f − 4 f transition. However, Ce 3+ doped h-BN has strong absorption and emission in the ultraviolet and visible light regions, respectively [ 33 , 34 ]. Notably, there is cross relaxation and energy transfer between Ce 3+ and Tb 3+ , and then Ce 3+ is often employed as a sensitizer to enhance the photoluminescence (PL) intensity of Tb 3+ in phosphors [ 35 , 36 ]. In the article, we synthesized h-BN using melamine as the nitrogen source and boric acid as the boron source. We investigated the influence of rare earth activators on the formation of BN crystal phases. It was interesting that co-doping Ce 3+ and Tb 3+ ions resulted in a significant increase in the critical concentration of the activators in h-BN [ 37 ]. Therefore, we doped Ce 3+ and Tb 3+ into h-BN to investigate the fluorescence properties of h-BN phosphors and the energy transfer between Ce 3+ and Tb 3+ ions. Additionally, we conducted a meticulous analysis of the correlation between the crystal structure of the matrix and its luminescent properties. The Ce 3+ and Tb 3+ co-doped h-BN phosphor exhibited strong green light emission under ultraviolet irradiation, making it a new green-emitting phosphor for solid-state lighting and fluorescent labeling. 2. Experimental process 2.1 Sample raw materials and their preparation A series of rare earth ion doped h-BN phosphors were synthesized by high-temperature solid state reaction. The starting materials included boric acid (H 3 BO 3 , AR), melamine (C 3 H 6 N 6 , AR), terbium trioxide (Tb 2 O 3 , 99%), and cerium dioxide (CeO 2 , 99%). The raw materials were weighted according to the predetermined stoichiometric ratio, and were thoroughly mixed by grinding them in an agate mortar for approximately 10 minutes. The mixture was put into an alumina crucible, and then calcined at 1250°C for 3 hours in a tube furnace under a reducing atmosphere of H 2 :N 2 (5:95). After naturally cooling to room temperature, the samples were reground into powder for further analysis. The experimental process is illustrated in Fig. 1 . 2.2 Performance characterization The crystal structure was detected on a Bruker D2 PHASER X-ray powder diffractometer with the 2θ range of 15°-70°. Transmission electron microscopy (FEI Talos F200s) was used to detect the morphology and crystallinity of phosphors. Surface morphologies and compositions were determined by a Hitachi Regulus 8100 scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS). Photoluminescence excitation (PLE), PL, temperature-dependent luminescence spectra and fluorescence decay curves were measured on an Edinburgh FS5 spectrometer with a temperature-controlled heating apparatus (TAP-02). Besides, Commission Internationale de l’Eclairage (CIE) chromaticity coordinates were calculated by using a CIE1931 program according to the emission spectra. 3. Results and discussion 3.1 Crystal structure analysis As shown in Fig. 2 (a), (S1) and (S2), the XRD patterns exhibit well-defined diffraction peaks at 26.76°, which corresponds to the (002) crystal faces of h-BN (JCPDS No.34–0421), In addition, Chang Sik Son's group reported that a high synthesis temperature can enhance the crystallinity of h-BN phosphors doped with Ce 3+ ions [ 31 ]. Moreover, we discovered that the co-doping of Tb 3+ with Ce 3+ can also improve the structural stability of h-BN phosphors, as depicted in Fig. 2 (a). Consequently, h-BN phosphors with high phase purity have been successfully synthesized. The h-BN crystal exhibits a layered structure similar to graphite, thus exhibiting excellent properties such as a wide band gap and high thermal stability. These BN layers consist of interleaved boron (B) and nitrogen (N) atoms, connected by powerful covalent bonds. Figure 2 (b) depicts B atoms facing N atoms in neighboring layers, alternating along the c-axis orientation. Utilizing the crystal structure of h-BN (CCDC#1500064) as the initial refinement model, Rietveld refinement of XRD pattern of h-BN phosphors was performed using GSAS software, which results are shown in the Fig. S3 and summarized in Table 1. The h-BN:0.001Tb 3+ , 0.002Ce 3+ crystallizes in the hexagonal crystal system with the space group Pm2. Its cell parameters are a = b = 2.486(3) Å, c = 6.71746(5) Å, V = 35.953(9) Å 3 . Among these cell parameters, the c value of h-BN:Tb 3+ , Ce 3+ is significantly larger than that (c = 6.6357(2)) of h-BN without activators. Therefore, it can be inferred that the activators enter the gap between layers, causing an increase in the cell parameter c . The radii of six-coordinated cations B 3+ , Tb 3+ and Ce 3+ are 0.27 Å, 0.92 Å and 1.01 Å, respectively [ 38 , 39 ]. The significant difference in ionic radii prevents rare earth cations (Tb 3+ , Ce 3+ ) from entering the main lattice but rather into interstitial sites, forming interstitial solid solutions [ 40 , 41 ]. Figure 2 (c) shows that Ce 3+ and Tb 3+ ions enter the h-BN lattice and locate at lattice gap sites. The increase of rare earth ion concentration leads to a gradual decrease in the diffraction peak intensity at 26.76° in h-BN XRD patterns, suggesting reduced crystallinity [ 42 ]. As shown in Fig. 2 (S1), when the concentration of Tb 3+ ions exceeds 0.001, an impure phase of TbBO 3 (JCPDS No.24-1272) appears in Tb 3+ doped h-BN phosphors. Similarly, the impure phase Ce(BO 2 ) 3 (JCPDS No.23–0877) is not observed until the Ce 3+ concentration exceeds 0.02 in Fig. 2 (S2). However, in Tb 3+ and Ce 3+ co-doping phosphors, the hexagonal crystal phase remains intact even with Tb 3+ and Ce 3+ concentrations as high as 0.025 and 0.05, respectively. Table 1 Refined structural data of the h-BN phosphors h-BN:0.001Tb 3+ ,0.002Ce 3+ Crystal system Space group Lattice parameters Unit cell volume R wp R p χ 2 Hexagonal Pm2 a = b = 2.486(3) Å, c = 6.71746(5) Å, α = β = 90˚, γ = 120˚ V = 35.953(9) Å 3 , Z = 2 5.63% 4.02% 1.86 3.2 SEM, EDS and TEM analysis The morphology and structure of h-BN:0.025Tb 3+ , 0.05Ce 3+ phosphors were characterized by SEM and TEM [ 43 ]. In Fig. 3 (a), the surface of h-BN crystal is fully covered by very tiny particles, which form a layered structure. As shown in Fig. 3 (b) and (c), TEM images reveal that these small particles composing the h-BN fluorescent powder tend to form agglomerates with a well-defined lattice structure. These agglomerates exhibit an apparent elliptical plane structure, measuring approximately 5 nm in size [ 44 ]. As shown in HRTEM images Fig. 3 (d), the d-spacing of h-BN:0.025Tb 3+ , 0.05Ce 3+ phosphors is 0.347 nm, and corresponds to the distance of (002) crystal plane of h-BN which d-spacing is 0.333 nm. The larger d-spacing of h-BN phosphors is consistent with its XRD pattern, indicating the successful incorporation of Ce 3+ and Tb 3+ into the h-BN lattice to form a stable interstitial solid solution. To provide additional evidence of the successful incorporation of Ce 3+ and Tb 3+ ions into the h-BN lattice, we conducted EDS spectroscopy detection on Ce 3+ and Tb 3+ co-doped h-BN phosphors, and investigated their elemental composition. As shown in Fig. 4 (a), the sample includes elements B, N, O, Ce, and Tb, clearly indicating the doping of Ce 3+ and Tb 3+ into the h-BN lattice. Furthermore, Fig. 4 (b)-(f) shows that these elements are uniformly distributed on the surface of the phosphors. The element O is considered an impurity element that can occupy gaps to balance valence states, making it an inevitable component in h-BN phosphors [ 30 , 45 , 46 ]. 3.3 Photoluminescence and energy transfer properties Ce 3+ is an attractive ion for phosphors as it not only acts as a luminescent ion but also functions as a sensitizer for other activators. Figure 5 (a) exhibits PLE and PL emission spectra of h-BN:0.002Ce 3+ phosphors. The phosphor displays two broad excitation bands in the regions of 230–290 nm and 290–370 nm, corresponding to 2F J → 5 d (J = 5/2 and 7/2) electron transitions of the Ce 3+ [ 47 ]. Under an ultraviolet excitation at 302 nm, the phosphor has a broad asymmetric emission band centered at around 406 nm, which is attributed to the characteristic parity-allowed transitions from the 5d to 2F 5/2 and 2F 7/2 levels. Figure 5 (b) shows the PLE and PL spectra of h-BN:0.001Tb 3+ , 0.002Ce 3+ phosphors. Under near-ultraviolet excitation at 302 nm, h-BN:0.001Tb 3+ , 0.002Ce 3+ phosphors exhibit strong green emission at 488 nm, 541 nm, 583 nm, and 620 nm, corresponding to the 5D 4 → 7F J (J = 6, 5, 4, 3) transition of Tb 3+ ions, respectively. The excitation spectra of h-BN:0.001Tb 3+ , 0.002Ce 3+ phosphors exhibit a wide band with a peak at 305 nm, which is assigned to the characteristic 4 f → 5 d transition of Ce 3+ ions. Compared to h-BN:0.001Tb 3+ , h-BN:0.001Tb 3+ , 0.002Ce 3+ phosphors emit strong green light from the electron transition of Tb 3+ . Additionally, as shown in Fig. S4. the emission spectra of h-BN matrix, h-BN:Tb 3+ under 302 nm excitation exhibit similarities, which implies that h-BN:Tb 3+ hardly emits light. While the h-BN:Tb 3+ , Ce 3+ under 302 nm excitation has strong emission peaks. The above results suggest the efficient energy transfer from Ce 3+ sensitizers to Tb 3+ activators [ 47 ]. To confirm the energy transfer from Ce 3+ to Tb 3+ , a series of h-BN:Tb 3+ , Ce 3+ (Tb 3+ /Ce 3+ = 0.5) phosphors was prepared under a H 2 :N 2 (5:95) atmosphere. As shown in Fig. 6 (a), the luminescence intensity is increases linearly with the rise in activator concentration. The energy transfer efficiency ( η ET ) from Ce 3+ (sensitizer) to Tb 3+ (activator) can be expressed by the given equation [ 48 ]: where η ET is the energy transfer efficiency, I and I 0 are the peak intensity of the sensitizer (Ce 3+ ) with and without activator (Tb 3+ ) under 305 nm excitation and 480 nm emission, respectively. As shown in Fig. 6 (b), the energy transfer efficiency from the sensitizer (Ce 3+ ) to the activator (Tb 3+ ) is approximately 55% while maintaining a constant concentration ratio. According to previous reports, as the concentration ratio of Tb 3+ /Ce 3+ increases, the energy transfer between Ce 3+ and Tb 3+ increases linearly within a certain concentration range [ 49 , 50 ]. Thus, the energy conversion efficiency is closely associated with the ratio of sensitized ion concentration to luminescent ion. The energy transfer process between the activator Tb 3+ and the sensitizer Ce 3+ is show in Fig. 6 (c) and (d). Under 305 nm excitation, h-BN can absorb UV light and result in electron transition of Ce 3+ from the 4 f ground state to the 5 d excited state However, these electrons in the 5 d state of Ce 3+ are unstable, and transfer energy to the electrons in the high-energy excited state 5D 4 of Tb 3+ . Subsequently, the electrons in 5D 4 level can release energy in the form of photon radiation, and return to four different ground states 7F J (J = 6, 5, 4, 3) of Tb 3+ . As a result, the phosphor exhibits intense green light emission. To accurately research the luminescence color of the phosphors, we characterized it with a CIE chromaticity diagram, as depicted in Fig. 7 As indicated by the chromaticity coordinates in Table 2 , the luminescent color shifts from yellow-green light to green light as the concentration of luminescent ions increases. As shown in the inset of Fig. 7 , the sample emits bright green light under UV irradiation. The luminescence intensity increases with the increase of Tb 3+ and Ce 3+ concentration. 3.4 Fluorescence lifetime and thermal luminescence properties To further study the luminescence mechanism, the decay curves of h-BN:Tb 3+ , Ce 3+ phosphors were measured monitored at 302 nm UV excitation and 541 nm emission. As shown in Fig. 8 (a), it is obvious that the fluorescence decays strictly obey the exponential rule in the Tb 3+ and Ce 3+ co-doped sample. The decay curves of the phosphor series were well-fitted using a second-order exponential function [ 51 ]: where y is the fluorescence intensity, y 0 is the initial intensity, A 1 and A 2 are constants, t 1 and t 2 represent the rapid and slow lifetimes for second order exponential components. Additionally, the effective lifetime constant ( τ ) can be calculated by the formula as follow [ 51 ]: The fluorescence lifetimes of h-BN:Tb 3+ , Ce 3+ phosphors, as illustrated in Fig. 8 (b), exhibit a rising trend as the activator concentration increases, measuring 1.126, 1.729, 1.912, and 2.087 ms, respectively. Typically, an increase in activator concentration leads to a greater extent of energy transfer that is mainly caused by electric multipolar interaction and radiation reabsorption among them. Strong electric multipolar interaction between activators usually leads to the decay of fluorescence lifetime [ 52 ]. Conversely, high radiation reabsorption usually results in an increase in fluorescence lifetime [ 53 ]. Therefore, the energy transfer between Tb 3+ and Ce 3+ in h-BN phosphors is primarily attributed to the spectral reabsorption between the emission of Ce 3+ and the excitation of Tb 3+ . Generally, the operating temperature of light-emitting diodes exceeds 100°C, making it crucial to investigate the thermal stability of h-BN:Tb 3+ , Ce 3+ phosphors. Figure 8 (c) shows the relationship between emission intensity and ambient temperature of h-BN:Tb 3+ , Ce 3+ phosphors. As the temperature increases from 25°C to 200°C, the PL intensity of the samples gradually declines. This decline can be attributed to the increased population of higher vibration levels, phonon density, and probability of non-radiative transfer at high temperatures. The relationship between temperature and fluorescence intensity can be investigated by analyzing the fitting of the activation energy ΔE , which is calculated using the thermal quenching equation [ 54 ]: I is the intensity at a given temperature T, I 0 is the initial intensity, C is a constant, ΔE is the activation energy for thermal quenching, k is the Boltzmann’s constant. Furthermore the linear fitting of ln[(I 0 /I) −1 ] and 1/kT is shown in Fig. 8 (d), the activation energy ( ΔE ) value of the phosphor is about 0.2825 eV. Furthermore, h-BN exhibits a significant energy gap between its conduction and valence bands, with a band width of approximately 5.9 eV. Consequently, the h-BN phosphor is expected to possess a high activation energy and low thermal quenching effect [ 55 ]. In addition, the position and shape of the emission wavelength remain almost unaltered as temperature increases, which is critical for applying phosphors to LEDs. In addition, to assess the potential application of the h-BN:Tb 3+ , Ce 3+ phosphors in white LEDs, we measured the IQE and EQE values of h-BN:0.025Tb 3+ , 0.05Ce 3+ green phosphors are measured through using the following equations [ 56 ] : where L S refers to the emission spectrum of the sample, ε is the absorption efficiency, E S and E R represent the spectra of excitation light with and without the sample in the integrating sphere, respectively. For the optimal h-BN:0.025Tb 3+ , 0.05Ce 3+ sample, the IQE and EQE are measured to be 52.1% and 14.6%, respectively, as shown in Fig. S5. Additionally, the IQE of the commercially available silicate S525 green phosphor was measured under the same test conditions, found to be 77.8%. Although the quantum efficiency of h-BN:Tb 3+ , Ce 3+ phosphor may be lower than that of commercial green phosphors, it can be enhanced through the optimization of activator concentration and preparation conditions. Therefore, the Tb 3+ /Ce 3+ co-doped h-BN green phosphor can be used for solid state lighting and fluorescent labeling [ 56 ]. 4. Conclusion Using melamine as nitrogen source, a series of h-BN phosphors were prepared by conventional solid-state reaction method. When the sample was doped solely with Tb 3+ or Ce 3+ , impurities were observed at lower dopant concentrations, such as TbBO 3 or Ce(BO 2 ) 3 . Conversely, co-doping of Tb 3+ and Ce 3+ makes h-BN maintain its monocrystalline phase even at high doping concentrations. Tb 3+ or Ce 3+ can successfully enter the lattice gap between BN layers, resulting in a slight lattice distortion and an increase in the crystal plane spacing along the c-axis. Under excitation at 302 nm, h-BN:Ce 3+ phosphor exhibits an asymmetric emission band centered at 406 nm. Due to the forbidden f - f transition of Tb 3+ , the h-BN:Tb 3+ phosphor exhibits limited emission under UV radiation. Moreover, under 302 nm excitation, h-BN:Tb 3+ , Ce 3+ phosphors have strong green emission at 488 nm, 541 nm, 583 nm and 620 nm, corresponding to 5D 4 → 7F J (J = 6, 5, 4, 3) electron transition of Tb 3+ . Ce 3+ ions are used as sensitizers for Tb 3+ activators in the energy transfer process. The energy transfer efficiency was about 55% when the ratio of [Tb 3+ ]/[Ce 3+ ] was 0.5, and remained relatively stable with the increase of activator concentration. The fluorescence lifetime of phosphors increased with the increase of activator concentration. Specifically, the fluorescence lifetime of h-BN:0.025Tb 3+ , 0.05Ce 3+ reaches 2.087 ms. Besides, the phosphor has a high activation energy value of approximately 0.2825 eV, indicating that h-BN phosphors have excellent thermal stability. Moreover, the PL quantum yield of h-BN:0.025Tb 3+ , 0.05Ce 3+ reaches 52.1%. Therefore, the phosphor shows potential as a green phosphor for solid state lighting and fluorescent labeling. Declarations Author Contributions Lunshuai Nie: Conceptualization, Software, Data curation, Writing–original draft, Methodology, Investigation. Kai Jia: Conceptualization, Formal analysis, Software, Validation. Hongguang Guo: Data curation, Investigation, Writing–original draft. Jiaqin He: Investigation, Methodology. Zhehui Weng and Yizhou Li: Resources, Supervision, Validation. Haidong Ju: Funding acquisition, Resources, Supervision, Writing–review & editing. Funding This work was financially supported by the National Natural Science Foundation of China (NSFC) (No. 22165016, 22066014), Applied Basic Research Foundation of Yunnan Province (No. 2018FH001-008), Reserve Talents of Young and Middle-aged Academic and Technical Leaders in Yunnan Province (No. 202205AC160042), the Yunnan Provincial Education Department Scientific Research Fund Project of Yunnan Province (No. 2022Y740), and Innovative Research Teams (in Science and Technology) in the University of Yunnan Province (IRTSTYN). Data Availability The data that support the findings of this study are available from the corresponding author upon reasonable request. Ethics Approval This paper meets the ethical standards of this journal. Competing Interest The authors declare no competing interests. Availability of data and materials This paper allows which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory. 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J Mater Chem C 7:10471–10480. 10.1039/c9tc03664d Li W, Qiu M, Li Y, Zhang S, Li Q, Lin W, Mu Z, Wu F (2019) Energy Transfer and Multicolor-Tunable Emissions of Sr 3 La 6 (SiO 4 ) 6 :Ce 3+ , Tb 3+ , Eu 3+ . J Electron Mater 49:1404–1411. 10.1016/S1010-6030(03)00381-2 Ding J, Huang S, Zheng H, Huang L, Zeng P, Ye S, Wu Q, Zhou J (2021) A novel broad-band cyan light-emitting oxynitride based phosphor used for realizing the full-visible-spectrum lighting of white LEDs. J Lumin 231:117786. 10.1016/j.jlumin.2020.117786 Tang H, Zhang X, Cheng L, Wang H, Xie J, Yu X, Wang Y, Mi X, Liu Q (2021) Luminescence properties and applications of Ce 3+ -activated Lu 3 Mg 2 GaSi 2 O 12 yellow-green emission garnet phosphors. Ceram Int 47:13100–13106. 10.1016/j.ceramint.2021.01.174 Iwaki M, Uematsu K, Sato M, Toda K (2023) Structure and Luminescence Studies of a Ce 3+ -Activated Ba 5 La 3 MgAl 3 O 15 Green-Emitting Phosphor. Inorg Chem 62:1250–1256. 10.1021/acs.inorgchem.2c04018 Du P, Yu JS (2017) Photoluminescence, cathodoluminescence and thermal stability of Sm 3+ -activated Sr 3 La(VO 4 ) 3 red‐emitting phosphors. Luminescence 32:1504–1510. 10.1002/bio.3351 Zhou Y, Hu Y, Liu R, Liu Y, Zhuang W, Cao M, Gao T, Tian J, Li Y, Chen G (2021) Blue-emitting Sr 1 – x Ca x Lu 2 O 4 :Ce 3+ phosphors for high CRI white LEDs. J Rare Earths 39:627–633. 10.1016/j.jre.2020.04.016 Huang X, Xu Z, Devakumar B (2023) Near-UV-excitable broadband green-emitting Ca 2 LaHf 2 GaAl 2 O 12 :Ce 3+ garnet-type phosphors for high color rendering warm-white LEDs. Ceram Int 49:26420–26427. 10.1016/j.ceramint.2023.05.178 Additional Declarations No competing interests reported. Supplementary Files SupportingInformation.docx Cite Share Download PDF Status: Published Journal Publication published 23 Mar, 2024 Read the published version in Journal of Fluorescence → Version 1 posted Editorial decision: Revision requested 08 Feb, 2024 Reviews received at journal 06 Feb, 2024 Reviewers agreed at journal 29 Jan, 2024 Reviewers invited by journal 29 Jan, 2024 Editor assigned by journal 29 Jan, 2024 Submission checks completed at journal 22 Jan, 2024 First submitted to journal 17 Jan, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3872075","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":268471188,"identity":"78aceabc-76b7-4790-9436-8532a479dae8","order_by":0,"name":"Lunshuai Nie","email":"","orcid":"","institution":"Kunming University","correspondingAuthor":false,"prefix":"","firstName":"Lunshuai","middleName":"","lastName":"Nie","suffix":""},{"id":268471189,"identity":"2bbf901f-0dd8-499f-818a-97eb91ca7d46","order_by":1,"name":"Kai Jia","email":"","orcid":"","institution":"Kunming 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phosphors.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3872075/v1/7b55147b8da017bbeea8bea5.png"},{"id":50116545,"identity":"861117ae-ae37-4562-8f39-bf548cf8905d","added_by":"auto","created_at":"2024-01-24 18:51:27","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":879145,"visible":true,"origin":"","legend":"\u003cp\u003e(a)\u003cstrong\u003e \u003c/strong\u003eXRD patterns of h-BN: Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e, (b) Crystal structure of h-BN, and (c) Lattice positions of Ce\u003csup\u003e3+\u003c/sup\u003e in h-BN\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-3872075/v1/8c75567d66ac1af47b764bb2.png"},{"id":50117666,"identity":"915a3bde-4adf-4046-8fee-a0c20afef31c","added_by":"auto","created_at":"2024-01-24 18:59:27","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1249154,"visible":true,"origin":"","legend":"\u003cp\u003e(a) SEM image of h-BN:0.025 Tb\u003csup\u003e3+\u003c/sup\u003e, 0.05 Ce\u003csup\u003e3+\u003c/sup\u003e, (b)-(d) TEM image of h-BN: 0.025 Tb\u003csup\u003e3+\u003c/sup\u003e, 0.05 Ce\u003csup\u003e3+\u003c/sup\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-3872075/v1/20060bc6d922c8eeec4c0d0b.png"},{"id":50116551,"identity":"27d4f4c3-ca63-4a85-92aa-44a2cf46e018","added_by":"auto","created_at":"2024-01-24 18:51:27","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":331628,"visible":true,"origin":"","legend":"\u003cp\u003e(a) EDS element spectrum, (b)-(f) EDS element mapping diagram.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-3872075/v1/be1ba932afc0a900542d2a42.png"},{"id":50117665,"identity":"2c82b3d2-76a5-480b-b83f-fa4a5629b394","added_by":"auto","created_at":"2024-01-24 18:59:27","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":105201,"visible":true,"origin":"","legend":"\u003cp\u003e(a) PLE and PL spectra of h-BN:0.002Ce\u003csup\u003e3+\u003c/sup\u003e phosphors, (b) PLE and PL spectra of h-BN:0.001 Tb\u003csup\u003e3+\u003c/sup\u003e, 0.002 Ce\u003csup\u003e3+\u003c/sup\u003e phosphor\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-3872075/v1/2654c5d14cbdc1f402b3c1f5.png"},{"id":50117667,"identity":"793c35bd-bfe8-4349-98bf-82bcb606d081","added_by":"auto","created_at":"2024-01-24 18:59:27","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":186186,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Emission spectra of h-BN:\u003cem\u003ey\u003c/em\u003eTb\u003csup\u003e3+\u003c/sup\u003e, \u003cem\u003ex\u003c/em\u003eCe\u003csup\u003e3+\u003c/sup\u003e phosphors, (b) Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e energy conversion efficiency, (c) and (d) Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e energy transfer process.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-3872075/v1/5a0b0558bc61cab1adcb4e1a.png"},{"id":50117664,"identity":"2527e5c5-bd34-4a19-8f65-5417de6e9006","added_by":"auto","created_at":"2024-01-24 18:59:27","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":232589,"visible":true,"origin":"","legend":"\u003cp\u003eCIE color coordinates of [Tb\u003csup\u003e3+\u003c/sup\u003e]/[Ce\u003csup\u003e3+\u003c/sup\u003e] co-doped h-BN phosphors.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-3872075/v1/9c9623d5199d97a00f849efb.png"},{"id":50116548,"identity":"ce9d6436-088f-4826-83c6-ace0f5a12208","added_by":"auto","created_at":"2024-01-24 18:51:27","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":563033,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Fluorescence decay curves and theoretical fitting curves of co-doped h-BN:\u003cem\u003ey\u003c/em\u003eTb\u003csup\u003e3+\u003c/sup\u003e, \u003cem\u003ex\u003c/em\u003eCe\u003csup\u003e3+\u003c/sup\u003e, (b) The change of fluorescence lifetime with various activator concentration, (c) Emission spectrum of h-BN phosphor as a function of temperature, (d) Linear fitting of \u003cem\u003eln[I\u003c/em\u003e\u003csub\u003e\u003cem\u003eT\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/I\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e-1]\u003c/em\u003e and \u003cem\u003e1/(kT)\u003c/em\u003e at 541 nm emission wavelength.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-3872075/v1/344180b40e64dcc86f31d684.png"},{"id":53403877,"identity":"0ff9eaf1-0ed1-40df-b8ce-5b02d4e8573a","added_by":"auto","created_at":"2024-03-25 15:15:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3903334,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3872075/v1/c8aa56f4-fc56-4f76-ae31-6387f0125888.pdf"},{"id":50116554,"identity":"57a20d92-afdf-43be-ac56-7a10ec12758a","added_by":"auto","created_at":"2024-01-24 18:51:28","extension":"docx","order_by":11,"title":"","display":"","copyAsset":false,"role":"supplement","size":2634804,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-3872075/v1/cc17b03883c5d1b5c49508e4.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eEffect of Tb\u003csup\u003e3+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e co-doping on the structural stability and photoluminescence properties of hexagonal boron nitride phosphors\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eIn recent years, solid state lighting have emerged as a next-generation lighting source, surpassing incandescent and fluorescent lamps in terms of efficiency, lifetime, and energy consumption [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Currently, the combination of light-emitting diodes (LEDs) chips and phosphor has become the most crucial approach to achieving commercialized solid state lighting [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Furthermore, 60\u0026ndash;100% of the white light of white LEDs comes from phosphors, so it is especially important to search for high-quality phosphors [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. YAG:Ce\u003csup\u003e3+\u003c/sup\u003e yellow phosphors with a garnet crystal structure have been widely used in commercialized white LEDs [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. However, the emission band of YAG: Ce\u003csup\u003e3+\u003c/sup\u003e yellow phosphors lacks red-emitting components, resulting in white LEDs with higher correlated color temperature (CCT) and lower color rendering index (CRI) [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. As a result, researchers have shifted their focus towards green and red phosphors to improve the optical quality of white LEDs, such as Y\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e:Eu\u003csup\u003e3+\u003c/sup\u003e and β-SiAlON:Eu\u003csup\u003e2+\u003c/sup\u003e [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Nitride and oxide nitride phosphors doped with rare earth activators have gained significant attention due to their excellent visible light emission and resistance to luminescence thermal quenching [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMore and more phosphors with nitride as the matrix have been prepared, and used as light conversion materials for white LEDs. For example, Wagatha P reported a red nitride phosphor α-Sr\u003csub\u003e2\u003c/sub\u003e[MgAl\u003csub\u003e5\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003e]: Eu\u003csup\u003e2+\u003c/sup\u003e with a luminous efficiency 1.2 to 1.5 times higher than mainstream red phosphors like (Ca, Sr)AlSiN\u003csub\u003e3\u003c/sub\u003e:Eu\u003csup\u003e2+\u003c/sup\u003e [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Additionally, nitride phosphors exhibit high thermal decomposition temperature and strong emission at high temperature, making them particularly suitable for high-power white LEDs [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Most nitride phosphors possess broad excitation bands that can be utilized for ultraviolet LED chips or blue LED chips. For instance, LiSi\u003csub\u003e2\u003c/sub\u003eN\u003csub\u003e3\u003c/sub\u003e phosphors doped with Eu\u003csup\u003e2+\u003c/sup\u003e or Ce\u003csup\u003e3+\u003c/sup\u003e have an excitation band ranging from 320 to 460 nm [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The nitride matrix can offer a strong crystal field to the activated ions, resulting in phosphors with various emitting colors. For example, Sr[Li\u003csub\u003e2\u003c/sub\u003eAl\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003eN\u003csub\u003e2\u003c/sub\u003e]:Eu\u003csup\u003e2+\u003c/sup\u003e features narrow-band emission at 614 nm, and CaAlSiN\u003csub\u003e3\u003c/sub\u003e:Eu\u003csup\u003e2+\u003c/sup\u003e phosphors exhibit red emission peaking at 649 nm [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Additionally, AlN:Tb\u003csup\u003e3+\u003c/sup\u003e, Eu\u003csup\u003e3+\u003c/sup\u003e nitride phosphors can emit different color light ranging from green to red [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Wang reports on a green phosphor, SrLuSi\u003csub\u003e4\u003c/sub\u003eN\u003csub\u003e7\u003c/sub\u003e:Ce\u003csup\u003e3+\u003c/sup\u003e, Tb\u003csup\u003e3+\u003c/sup\u003e, capable of tuning its color under ultraviolet excitation for use in white LEDs [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Binary nitrides, known for their straightforward structure and wide bandgap, have gained attention as matrices for nitride phosphors, including rare earth ion-doped GaN, AlN, and Si\u003csub\u003e3\u003c/sub\u003eN\u003csub\u003e4\u003c/sub\u003e phosphors [\u003cspan additionalcitationids=\"CR19 CR20 CR21 CR22 CR23\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Hexagonal boron nitride (h-BN) possesses a wide bandgap of approximately 5.2 eV and outstanding thermochemical stability, and has been identified as an ideal host material for inorganic phosphors [\u003cspan additionalcitationids=\"CR26 CR27\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. However, there have been few articles on h-BN phosphors except for Eu\u003csup\u003e3+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e doped h-BN [\u003cspan additionalcitationids=\"CR30 CR31\" citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Tb\u003csup\u003e3+\u003c/sup\u003e doped phosphors have poor absorption in the ultraviolet region due to the forbidden 4\u003cem\u003ef\u003c/em\u003e\u0026thinsp;\u0026minus;\u0026thinsp;4\u003cem\u003ef\u003c/em\u003e transition. However, Ce\u003csup\u003e3+\u003c/sup\u003e doped h-BN has strong absorption and emission in the ultraviolet and visible light regions, respectively [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Notably, there is cross relaxation and energy transfer between Ce\u003csup\u003e3+\u003c/sup\u003e and Tb\u003csup\u003e3+\u003c/sup\u003e, and then Ce\u003csup\u003e3+\u003c/sup\u003e is often employed as a sensitizer to enhance the photoluminescence (PL) intensity of Tb\u003csup\u003e3+\u003c/sup\u003e in phosphors [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn the article, we synthesized h-BN using melamine as the nitrogen source and boric acid as the boron source. We investigated the influence of rare earth activators on the formation of BN crystal phases. It was interesting that co-doping Ce\u003csup\u003e3+\u003c/sup\u003e and Tb\u003csup\u003e3+\u003c/sup\u003e ions resulted in a significant increase in the critical concentration of the activators in h-BN [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Therefore, we doped Ce\u003csup\u003e3+\u003c/sup\u003e and Tb\u003csup\u003e3+\u003c/sup\u003e into h-BN to investigate the fluorescence properties of h-BN phosphors and the energy transfer between Ce\u003csup\u003e3+\u003c/sup\u003e and Tb\u003csup\u003e3+\u003c/sup\u003e ions. Additionally, we conducted a meticulous analysis of the correlation between the crystal structure of the matrix and its luminescent properties. The Ce\u003csup\u003e3+\u003c/sup\u003e and Tb\u003csup\u003e3+\u003c/sup\u003e co-doped h-BN phosphor exhibited strong green light emission under ultraviolet irradiation, making it a new green-emitting phosphor for solid-state lighting and fluorescent labeling.\u003c/p\u003e"},{"header":"2. Experimental process","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Sample raw materials and their preparation\u003c/h2\u003e \u003cp\u003eA series of rare earth ion doped h-BN phosphors were synthesized by high-temperature solid state reaction. The starting materials included boric acid (H\u003csub\u003e3\u003c/sub\u003eBO\u003csub\u003e3\u003c/sub\u003e, AR), melamine (C\u003csub\u003e3\u003c/sub\u003eH\u003csub\u003e6\u003c/sub\u003eN\u003csub\u003e6\u003c/sub\u003e, AR), terbium trioxide (Tb\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e, 99%), and cerium dioxide (CeO\u003csub\u003e2\u003c/sub\u003e, 99%). The raw materials were weighted according to the predetermined stoichiometric ratio, and were thoroughly mixed by grinding them in an agate mortar for approximately 10 minutes. The mixture was put into an alumina crucible, and then calcined at 1250\u0026deg;C for 3 hours in a tube furnace under a reducing atmosphere of H\u003csub\u003e2\u003c/sub\u003e:N\u003csub\u003e2\u003c/sub\u003e (5:95). After naturally cooling to room temperature, the samples were reground into powder for further analysis. The experimental process is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Performance characterization\u003c/h2\u003e \u003cp\u003eThe crystal structure was detected on a Bruker D2 PHASER X-ray powder diffractometer with the 2θ range of 15\u0026deg;-70\u0026deg;. Transmission electron microscopy (FEI Talos F200s) was used to detect the morphology and crystallinity of phosphors. Surface morphologies and compositions were determined by a Hitachi Regulus 8100 scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS). Photoluminescence excitation (PLE), PL, temperature-dependent luminescence spectra and fluorescence decay curves were measured on an Edinburgh FS5 spectrometer with a temperature-controlled heating apparatus (TAP-02). Besides, Commission Internationale de l\u0026rsquo;Eclairage (CIE) chromaticity coordinates were calculated by using a CIE1931 program according to the emission spectra.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and discussion","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Crystal structure analysis\u003c/h2\u003e\n \u003cp\u003eAs shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e(a), (S1) and (S2), the XRD patterns exhibit well-defined diffraction peaks at 26.76\u0026deg;, which corresponds to the (002) crystal faces of h-BN (JCPDS No.34\u0026ndash;0421), In addition, Chang Sik Son\u0026apos;s group reported that a high synthesis temperature can enhance the crystallinity of h-BN phosphors doped with Ce\u003csup\u003e3+\u003c/sup\u003e ions [\u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e]. Moreover, we discovered that the co-doping of Tb\u003csup\u003e3+\u003c/sup\u003e with Ce\u003csup\u003e3+\u003c/sup\u003e can also improve the structural stability of h-BN phosphors, as depicted in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e(a). Consequently, h-BN phosphors with high phase purity have been successfully synthesized. The h-BN crystal exhibits a layered structure similar to graphite, thus exhibiting excellent properties such as a wide band gap and high thermal stability. These BN layers consist of interleaved boron (B) and nitrogen (N) atoms, connected by powerful covalent bonds. Figure \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e(b) depicts B atoms facing N atoms in neighboring layers, alternating along the c-axis orientation. Utilizing the crystal structure of h-BN (CCDC#1500064) as the initial refinement model, Rietveld refinement of XRD pattern of h-BN phosphors was performed using GSAS software, which results are shown in the Fig. S3 and summarized in Table\u0026nbsp;1. The h-BN:0.001Tb\u003csup\u003e3+\u003c/sup\u003e, 0.002Ce\u003csup\u003e3+\u003c/sup\u003e crystallizes in the hexagonal crystal system with the space group Pm2. Its cell parameters are \u003cem\u003ea\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u003cem\u003eb\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2.486(3) \u0026Aring;, \u003cem\u003ec\u003c/em\u003e\u0026thinsp;=\u0026thinsp;6.71746(5) \u0026Aring;, \u003cem\u003eV\u003c/em\u003e\u0026thinsp;=\u0026thinsp;35.953(9) \u0026Aring;\u003csup\u003e3\u003c/sup\u003e. Among these cell parameters, the \u003cem\u003ec\u003c/em\u003e value of h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e is significantly larger than that (c\u0026thinsp;=\u0026thinsp;6.6357(2)) of h-BN without activators. Therefore, it can be inferred that the activators enter the gap between layers, causing an increase in the cell parameter \u003cem\u003ec\u003c/em\u003e.\u003c/p\u003e\n \u003cp\u003eThe radii of six-coordinated cations B\u003csup\u003e3+\u003c/sup\u003e, Tb\u003csup\u003e3+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e are 0.27 \u0026Aring;, 0.92 \u0026Aring; and 1.01 \u0026Aring;, respectively [\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e]. The significant difference in ionic radii prevents rare earth cations (Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e) from entering the main lattice but rather into interstitial sites, forming interstitial solid solutions [\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e]. Figure \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e(c) shows that Ce\u003csup\u003e3+\u003c/sup\u003e and Tb\u003csup\u003e3+\u003c/sup\u003e ions enter the h-BN lattice and locate at lattice gap sites. The increase of rare earth ion concentration leads to a gradual decrease in the diffraction peak intensity at 26.76\u0026deg; in h-BN XRD patterns, suggesting reduced crystallinity [\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e]. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e(S1), when the concentration of Tb\u003csup\u003e3+\u003c/sup\u003e ions exceeds 0.001, an impure phase of TbBO\u003csub\u003e3\u003c/sub\u003e (JCPDS No.24-1272) appears in Tb\u003csup\u003e3+\u003c/sup\u003e doped h-BN phosphors. Similarly, the impure phase Ce(BO\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e (JCPDS No.23\u0026ndash;0877) is not observed until the Ce\u003csup\u003e3+\u003c/sup\u003e concentration exceeds 0.02 in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e(S2). However, in Tb\u003csup\u003e3+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e co-doping phosphors, the hexagonal crystal phase remains intact even with Tb\u003csup\u003e3+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e concentrations as high as 0.025 and 0.05, respectively.\u003c/p\u003e\n \u003cp\u003eTable 1 Refined structural data of the h-BN phosphors\u003c/p\u003e\n \u003ctable id=\"Taba\" border=\"1\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"2\"\u003e\n \u003cp\u003eh-BN:0.001Tb\u003csup\u003e3+\u003c/sup\u003e,0.002Ce\u003csup\u003e3+\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCrystal system\u003c/p\u003e\n \u003cp\u003eSpace group\u003c/p\u003e\n \u003cp\u003eLattice parameters\u003c/p\u003e\n \u003cp\u003eUnit cell volume\u003c/p\u003e\n \u003cp\u003eR\u003csub\u003ewp\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003eR\u003csub\u003ep\u003c/sub\u003e\u003c/p\u003e\n \u003cp\u003e\u0026chi;\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eHexagonal\u003c/p\u003e\n \u003cp\u003ePm2\u003c/p\u003e\n \u003cp\u003ea\u0026thinsp;=\u0026thinsp;b\u0026thinsp;=\u0026thinsp;2.486(3) \u0026Aring;, c\u0026thinsp;=\u0026thinsp;6.71746(5) \u0026Aring;,\u003c/p\u003e\n \u003cp\u003e\u0026alpha;\u0026thinsp;=\u0026thinsp;\u0026beta;\u0026thinsp;=\u0026thinsp;90˚, \u0026gamma;\u0026thinsp;=\u0026thinsp;120˚\u003c/p\u003e\n \u003cp\u003eV\u0026thinsp;=\u0026thinsp;35.953(9)\u0026nbsp;\u0026Aring;\u003csup\u003e3\u003c/sup\u003e, Z\u0026thinsp;=\u0026thinsp;2\u003c/p\u003e\n \u003cp\u003e5.63%\u003c/p\u003e\n \u003cp\u003e4.02%\u003c/p\u003e\n \u003cp\u003e1.86\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 SEM, EDS and TEM analysis\u003c/h2\u003e\n \u003cp\u003eThe morphology and structure of h-BN:0.025Tb\u003csup\u003e3+\u003c/sup\u003e, 0.05Ce\u003csup\u003e3+\u003c/sup\u003e phosphors were characterized by SEM and TEM [\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e]. In Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(a), the surface of h-BN crystal is fully covered by very tiny particles, which form a layered structure. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(b) and (c), TEM images reveal that these small particles composing the h-BN fluorescent powder tend to form agglomerates with a well-defined lattice structure. These agglomerates exhibit an apparent elliptical plane structure, measuring approximately 5 nm in size [\u003cspan class=\"CitationRef\"\u003e44\u003c/span\u003e]. As shown in HRTEM images Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(d), the d-spacing of h-BN:0.025Tb\u003csup\u003e3+\u003c/sup\u003e, 0.05Ce\u003csup\u003e3+\u003c/sup\u003e phosphors is 0.347 nm, and corresponds to the distance of (002) crystal plane of h-BN which d-spacing is 0.333 nm. The larger d-spacing of h-BN phosphors is consistent with its XRD pattern, indicating the successful incorporation of Ce\u003csup\u003e3+\u003c/sup\u003e and Tb\u003csup\u003e3+\u003c/sup\u003e into the h-BN lattice to form a stable interstitial solid solution. To provide additional evidence of the successful incorporation of Ce\u003csup\u003e3+\u003c/sup\u003e and Tb\u003csup\u003e3+\u003c/sup\u003e ions into the h-BN lattice, we conducted EDS spectroscopy detection on Ce\u003csup\u003e3+\u003c/sup\u003e and Tb\u003csup\u003e3+\u003c/sup\u003e co-doped h-BN phosphors, and investigated their elemental composition. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(a), the sample includes elements B, N, O, Ce, and Tb, clearly indicating the doping of Ce\u003csup\u003e3+\u003c/sup\u003e and Tb\u003csup\u003e3+\u003c/sup\u003e into the h-BN lattice. Furthermore, Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(b)-(f) shows that these elements are uniformly distributed on the surface of the phosphors. The element O is considered an impurity element that can occupy gaps to balance valence states, making it an inevitable component in h-BN phosphors [\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e45\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e46\u003c/span\u003e].\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003e3.3 Photoluminescence and energy transfer properties\u003c/h2\u003e\n \u003cp\u003eCe\u003csup\u003e3+\u003c/sup\u003e is an attractive ion for phosphors as it not only acts as a luminescent ion but also functions as a sensitizer for other activators. Figure \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e(a) exhibits PLE and PL emission spectra of h-BN:0.002Ce\u003csup\u003e3+\u003c/sup\u003e phosphors. The phosphor displays two broad excitation bands in the regions of 230\u0026ndash;290 nm and 290\u0026ndash;370 nm, corresponding to 2F\u003csub\u003eJ\u003c/sub\u003e \u0026rarr; 5\u003cem\u003ed\u003c/em\u003e (J\u0026thinsp;=\u0026thinsp;5/2 and 7/2) electron transitions of the Ce\u003csup\u003e3+\u003c/sup\u003e [\u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e]. Under an ultraviolet excitation at 302 nm, the phosphor has a broad asymmetric emission band centered at around 406 nm, which is attributed to the characteristic parity-allowed transitions from the 5d to 2F\u003csub\u003e5/2\u003c/sub\u003e and 2F\u003csub\u003e7/2\u003c/sub\u003e levels. Figure \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e(b) shows the PLE and PL spectra of h-BN:0.001Tb\u003csup\u003e3+\u003c/sup\u003e, 0.002Ce\u003csup\u003e3+\u003c/sup\u003e phosphors. Under near-ultraviolet excitation at 302 nm, h-BN:0.001Tb\u003csup\u003e3+\u003c/sup\u003e, 0.002Ce\u003csup\u003e3+\u003c/sup\u003e phosphors exhibit strong green emission at 488 nm, 541 nm, 583 nm, and 620 nm, corresponding to the 5D\u003csub\u003e4\u003c/sub\u003e \u0026rarr; 7F\u003csub\u003eJ\u003c/sub\u003e (J\u0026thinsp;=\u0026thinsp;6, 5, 4, 3) transition of Tb\u003csup\u003e3+\u003c/sup\u003e ions, respectively. The excitation spectra of h-BN:0.001Tb\u003csup\u003e3+\u003c/sup\u003e, 0.002Ce\u003csup\u003e3+\u003c/sup\u003e phosphors exhibit a wide band with a peak at 305 nm, which is assigned to the characteristic 4\u003cem\u003ef\u003c/em\u003e \u0026rarr; 5\u003cem\u003ed\u003c/em\u003e transition of Ce\u003csup\u003e3+\u003c/sup\u003e ions. Compared to h-BN:0.001Tb\u003csup\u003e3+\u003c/sup\u003e, h-BN:0.001Tb\u003csup\u003e3+\u003c/sup\u003e, 0.002Ce\u003csup\u003e3+\u003c/sup\u003e phosphors emit strong green light from the electron transition of Tb\u003csup\u003e3+\u003c/sup\u003e. Additionally, as shown in Fig. S4. the emission spectra of h-BN matrix, h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e under 302 nm excitation exhibit similarities, which implies that h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e hardly emits light. While the h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e under 302 nm excitation has strong emission peaks. The above results suggest the efficient energy transfer from Ce\u003csup\u003e3+\u003c/sup\u003e sensitizers to Tb\u003csup\u003e3+\u003c/sup\u003e activators [\u003cspan class=\"CitationRef\"\u003e47\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003eTo confirm the energy transfer from Ce\u003csup\u003e3+\u003c/sup\u003e to Tb\u003csup\u003e3+\u003c/sup\u003e, a series of h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e (Tb\u003csup\u003e3+\u003c/sup\u003e/Ce\u003csup\u003e3+\u003c/sup\u003e = 0.5) phosphors was prepared under a H\u003csub\u003e2\u003c/sub\u003e:N\u003csub\u003e2\u003c/sub\u003e (5:95) atmosphere. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(a), the luminescence intensity is increases linearly with the rise in activator concentration. The energy transfer efficiency (\u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003e\u003cem\u003eET\u003c/em\u003e\u003c/sub\u003e) from Ce\u003csup\u003e3+\u003c/sup\u003e (sensitizer) to Tb\u003csup\u003e3+\u003c/sup\u003e (activator) can be expressed by the given equation [\u003cspan class=\"CitationRef\"\u003e48\u003c/span\u003e]:\u003c/p\u003e\n \u003cp\u003e\u003cimg src=\"data:image/png;base64,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\" width=\"342\" height=\"35\"\u003e\u003c/p\u003e\n \u003cp\u003ewhere \u003cem\u003e\u0026eta;\u003c/em\u003e\u003csub\u003e\u003cem\u003eET\u003c/em\u003e\u003c/sub\u003e is the energy transfer efficiency, \u003cem\u003eI\u003c/em\u003e and \u003cem\u003eI\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e are the peak intensity of the sensitizer (Ce\u003csup\u003e3+\u003c/sup\u003e) with and without activator (Tb\u003csup\u003e3+\u003c/sup\u003e) under 305 nm excitation and 480 nm emission, respectively. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e (b), the energy transfer efficiency from the sensitizer (Ce\u003csup\u003e3+\u003c/sup\u003e) to the activator (Tb\u003csup\u003e3+\u003c/sup\u003e) is approximately 55% while maintaining a constant concentration ratio. According to previous reports, as the concentration ratio of Tb\u003csup\u003e3+\u003c/sup\u003e/Ce\u003csup\u003e3+\u003c/sup\u003e increases, the energy transfer between Ce\u003csup\u003e3+\u003c/sup\u003e and Tb\u003csup\u003e3+\u003c/sup\u003e increases linearly within a certain concentration range [\u003cspan class=\"CitationRef\"\u003e49\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e50\u003c/span\u003e]. Thus, the energy conversion efficiency is closely associated with the ratio of sensitized ion concentration to luminescent ion. The energy transfer process between the activator Tb\u003csup\u003e3+\u003c/sup\u003e and the sensitizer Ce\u003csup\u003e3+\u003c/sup\u003e is show in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(c) and (d). Under 305 nm excitation, h-BN can absorb UV light and result in electron transition of Ce\u003csup\u003e3+\u003c/sup\u003e from the 4\u003cem\u003ef\u003c/em\u003e ground state to the 5\u003cem\u003ed\u003c/em\u003e excited state However, these electrons in the 5\u003cem\u003ed\u003c/em\u003e state of Ce\u003csup\u003e3+\u003c/sup\u003e are unstable, and transfer energy to the electrons in the high-energy excited state 5D\u003csub\u003e4\u003c/sub\u003e of Tb\u003csup\u003e3+\u003c/sup\u003e. Subsequently, the electrons in 5D\u003csub\u003e4\u003c/sub\u003e level can release energy in the form of photon radiation, and return to four different ground states 7F\u003csub\u003eJ\u003c/sub\u003e (J\u0026thinsp;=\u0026thinsp;6, 5, 4, 3) of Tb\u003csup\u003e3+\u003c/sup\u003e. As a result, the phosphor exhibits intense green light emission. To accurately research the luminescence color of the phosphors, we characterized it with a CIE chromaticity diagram, as depicted in Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e As indicated by the chromaticity coordinates in Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e, the luminescent color shifts from yellow-green light to green light as the concentration of luminescent ions increases. As shown in the inset of Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e, the sample emits bright green light under UV irradiation. The luminescence intensity increases with the increase of Tb\u003csup\u003e3+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003econcentration.\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u003cimg 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\" width=\"621\" height=\"202\"\u003e\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.4 Fluorescence lifetime and thermal luminescence properties\u003c/h2\u003e\n \u003cp\u003eTo further study the luminescence mechanism, the decay curves of h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e phosphors were measured monitored at 302 nm UV excitation and 541 nm emission. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e(a), it is obvious that the fluorescence decays strictly obey the exponential rule in the Tb\u003csup\u003e3+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e co-doped sample. The decay curves of the phosphor series were well-fitted using a second-order exponential function [\u003cspan class=\"CitationRef\"\u003e51\u003c/span\u003e]:\u003c/p\u003e\n \u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\n \u003cdiv class=\"EquationNumber\"\u003e\u003cimg src=\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAYoAAAAfCAYAAAD5oopUAAAIOElEQVR4Ae2cPW7cPBCGfYfcIAF8AzduU9i1i6RzlwBpDR/AcBfAMNzbfRC4DHKAJH0OYCBtcgAfQB+exfc6E5oUqRVFyfIQWFDiz8zwfaUZ/uzuTufJEXAEHAFHwBHoQWCnp86rnjgCP3/+7L5+/brYUVxfX3fY6OkxAkvnDoudv8e8rbXEA8VKmcXR8CIvPZ2dnXmwCEh6KtxhtvMXkLfSWw8UKyT29+/f3bt377r7+/vFjw5b375925F76jY4PBXu4Mv5ex5PrQeKFfJ8fHzcffnyZZaRoffk5GSQ7ouLi46Pp66bi7tteBNfzp+QWG/ugWIkt7xgcznlmOnM8Pb29mbZzmEF8+bNm8G62WrB5lariqVxJh7n4m5b3mR3a/6k1/M0Ajs7Za69uF1aldfkEOAF2d3dHewYc3LH1DO7e/369SzbTtvOSnFU2NxiVbFEzsT3XNxty5vsbsmfdHoeR+DHjx8dzv/Xr18PDQ4ODjZllIeBgXaU0a8vlYWdPgnPtE4vx4sXLxYTKGQT2xetU2yvesi3YrB56gAnfJbEmXiSba25G8ub7G/Bn3R5nkYgDBIfPnz4Jwi8evUqGSxscAk1PNtAwSxqzAyWfXgOYV++fNlsyyQkL7znpceeMeMKZZbeo9Pq/fTp0yBscDQ5LNfImfCdi7uxvMn+Ev7U1vNpECAofPz48R/hvIc2acURriDox8ojlQYHCh4IolY4K+OBm2JGOJW+MU5HS/WhY2aGDW7gp3MEtkJURjkyNWbd//nzZ3NAzP7/9+/fN30l4+7u7oFbyUJGjcQ40cOHaxI6sN1ybWelXFOnfrZvn03YHD5TYfs5OMOGqXkTroy/BncteRNHJfypref1EdAWUt+qAK2pdqlyWTo4UNARZxHOXCk7PDx8NLu2Ts86D3udezmG6NPAcvm2TgdbcNhsFTA26zD7dLICsT9+sy8Wzh45cpTo4OyD9ug5Ojp6CC6SQR84sPrpV8vZaCx2nAQp6Vc9OWOxHGobxZbZ9rFri0esnrLWnKGzBW/oqc1dK97EVQl/aut5fQRYOeBTc4l2qZUD21LhikTy8pLV0uRyBDhKJWaSNzc3uq2aT6FvG6eDHfpWT8ym1KDlBGxw1LWcqbYemK3HflcQC0qaOZKTpEcyU/YMLZceflwVJruaUB12DD3kL3E0LTljLMJTXNlcGNfgzeqSXGE5Jm/Bm+wr4U9tPa+PANtOOPpcIkikVh3UISeWqgWKz58/P1pNxBRuUxZzykP1laxsbOCL2RmTkeuDHF7Y3P477eSYYjIps6sH217ORf11rzHE7LZOj+uwj/qSyxkyjjDRL+zLfWhr2C+8p49WVKorsTuGlfqTx2Tk+qh/K97QF+MuZvvSeBNWMf5U5/n0CJQEClYT4ZmFtax6oEA4D7GcAQ956u8ixj7sGkipPrXP5TiB0MH19aG9/SGZnGeJDPqGTjCmi3b7+/v/nAmonR2/ymQD/UgxZ6O2Y3LpwQabKE+tfsK2tl/susTRMM4SvCWf9ttyhgz6t+ANXVNw14I3YV3Cn9p6Xh+BXKDg8Dq1WpA1kwQKHgwCBQetU205aQDktfUNcTq8xDqXkE16sZGTS2qL07F7/JQrwFodONnQQcUCRejIUo4hZ1+uHn7ZdgpXRXDCxybZUIKL7YecUL6t57olZ+hrxRu6hNvQABtiZO9b8CZ9Jfypref1Eeg7o2CriSCQS9XPKFCoB+P09HSyLSc7sD59vNB8hqRSpwMBsV8N4+DZBpCjZ3uMoJlKOIBw20DBACfBzFzfYOIenThOlSl4aOmoA3DrWGJbdCl7SsvR9+3btw2+One4vLzc3MdWEwpeHHzjqLAphw22MA6tUFO21eYMPdjZ9+y04A07anNXgzfxkMOIdiX8SZ7n9RHQt5bCr71SHju7CAOH+pPH0lZnFAiSQ+h7yWIKty1L6cOJ2U+p/JzTYVw4cjl3OTHN/FROTt3V1dUGk5R+HAGzcskkEAg7OSNyku6lA1v1IvKHcZQjB3nItYmAKltt+dBr5KBDgUmODLsJUtTzCZN4Oj8/f7CNYEp5Kkl2TJ7tU5uz29vbDQdsT6Xsa8Ub42T8Y7lDRi3esIkVMM9pDiPszvFnufTr+giwtWS/taTfTMiP2Fzvtayo/jsKCebFSr1calMzT+njAeZBxoHHvpVT04Y+WSn7+voMqVOgCANDKEOrEQWhsH6O+xw22BpbtbWyNWffGDtKeUPHErnT2Pswmps/2eh5t5lEplYFffgQRPr6bbWi4MGwe+19BtSo69NHcOAF80DxF2lmdkua3fU5GaymHoc6V+IbdFOlIYECG5bGnXDpw2hu/mSj539/UBduQaWw0ZZTrn1xoOBhYHnJfqX25VPKa5SX6sMWAgmfFnalxoa9fKZKQxwOQTN2fjCVbTm5fdiwQmI7DZvnSDzPuVXaGLuG8IaepXGHTX0Yzc3fGG7W3Dd2LhEbLyuJklTW6v+ZDnufrZwxM6sSfeyXM9vho4PfkoHXboMznAIbXkQCtPYXc98M0rgInHNuxckO8j5sFOht+1bX6Cagvn//vvoKeVveGPuSuMthNCd/rZ4T19N1xYHCwXp6CCiILtVydzJpZpbOHZY7f2n+1lbjgWJtjPp4HAFHwBGojIAHisqAujhHwBFwBNaGgAeKtTHq43EEHAFHoDICHigqA+riHAFHwBFYGwIeKNbGqI/HEXAEHIHKCHigqAyoi3MEHAFHYG0IeKBYG6M+HkfAEXAEKiPggaIyoC7OEXAEHIG1IeCBYm2M+ngcAUfAEaiMwH/5G8MvUnPjNwAAAABJRU5ErkJggg==\" width=\"394\" height=\"31\"\u003e\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003ewhere \u003cem\u003ey\u003c/em\u003e is the fluorescence intensity, \u003cem\u003ey\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e is the initial intensity, \u003cem\u003eA\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eA\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e are constants, \u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003et\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e represent the rapid and slow lifetimes for second order exponential components. Additionally, the effective lifetime constant (\u003cem\u003e\u0026tau;\u003c/em\u003e) can be calculated by the formula as follow [\u003cspan class=\"CitationRef\"\u003e51\u003c/span\u003e]:\u003c/p\u003e\n \u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\n \u003cdiv class=\"EquationNumber\"\u003e\u003cimg src=\"data:image/png;base64,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\" width=\"400\" height=\"31\"\u003e\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003eThe fluorescence lifetimes of h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e phosphors, as illustrated in Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e(b), exhibit a rising trend as the activator concentration increases, measuring 1.126, 1.729, 1.912, and 2.087 ms, respectively. Typically, an increase in activator concentration leads to a greater extent of energy transfer that is mainly caused by electric multipolar interaction and radiation reabsorption among them. Strong electric multipolar interaction between activators usually leads to the decay of fluorescence lifetime [\u003cspan class=\"CitationRef\"\u003e52\u003c/span\u003e]. Conversely, high radiation reabsorption usually results in an increase in fluorescence lifetime [\u003cspan class=\"CitationRef\"\u003e53\u003c/span\u003e]. Therefore, the energy transfer between Tb\u003csup\u003e3+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e in h-BN phosphors is primarily attributed to the spectral reabsorption between the emission of Ce\u003csup\u003e3+\u003c/sup\u003e and the excitation of Tb\u003csup\u003e3+\u003c/sup\u003e.\u003c/p\u003e\n \u003cp\u003eGenerally, the operating temperature of light-emitting diodes exceeds 100\u0026deg;C, making it crucial to investigate the thermal stability of h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e phosphors. Figure \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e(c) shows the relationship between emission intensity and ambient temperature of h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e phosphors. As the temperature increases from 25\u0026deg;C to 200\u0026deg;C, the PL intensity of the samples gradually declines. This decline can be attributed to the increased population of higher vibration levels, phonon density, and probability of non-radiative transfer at high temperatures. The relationship between temperature and fluorescence intensity can be investigated by analyzing the fitting of the activation energy \u003cem\u003e\u0026Delta;E\u003c/em\u003e, which is calculated using the thermal quenching equation [\u003cspan class=\"CitationRef\"\u003e54\u003c/span\u003e]:\u003c/p\u003e\n \u003cdiv id=\"Equ3\" class=\"Equation\"\u003e\n \u003cdiv class=\"EquationNumber\"\u003e\u003cimg src=\"data:image/png;base64,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\" width=\"338\" height=\"36\"\u003e\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003e\u003cem\u003eI\u003c/em\u003e is the intensity at a given temperature \u003cem\u003eT, I\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e is the initial intensity, \u003cem\u003eC\u003c/em\u003e is a constant, \u003cem\u003e\u0026Delta;E\u003c/em\u003e is the activation energy for thermal quenching, \u003cem\u003ek\u003c/em\u003e is the Boltzmann\u0026rsquo;s constant. Furthermore the linear fitting of \u003cem\u003eln[(I\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/I)\u003c/em\u003e\u003csup\u003e\u003cem\u003e\u0026minus;1\u003c/em\u003e\u003c/sup\u003e\u003cem\u003e]\u003c/em\u003e and \u003cem\u003e1/kT\u003c/em\u003e is shown in Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e(d), the activation energy (\u003cem\u003e\u0026Delta;E\u003c/em\u003e) value of the phosphor is about 0.2825 eV. Furthermore, h-BN exhibits a significant energy gap between its conduction and valence bands, with a band width of approximately 5.9 eV. Consequently, the h-BN phosphor is expected to possess a high activation energy and low thermal quenching effect [\u003cspan class=\"CitationRef\"\u003e55\u003c/span\u003e]. In addition, the position and shape of the emission wavelength remain almost unaltered as temperature increases, which is critical for applying phosphors to LEDs.\u003c/p\u003e\n \u003cp\u003eIn addition, to assess the potential application of the h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e phosphors in white LEDs, we measured the \u003cem\u003eIQE\u003c/em\u003e and \u003cem\u003eEQE\u003c/em\u003e values of h-BN:0.025Tb\u003csup\u003e3+\u003c/sup\u003e, 0.05Ce\u003csup\u003e3+\u003c/sup\u003e green phosphors are measured through using the following equations [\u003cspan class=\"CitationRef\"\u003e56\u003c/span\u003e] :\u003c/p\u003e\n \u003cdiv id=\"Equ4\" class=\"Equation\"\u003e\n \u003cdiv class=\"EquationNumber\"\u003e\u003cimg src=\"data:image/png;base64,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\" width=\"365\" height=\"180\"\u003e\u003c/div\u003e\n \u003c/div\u003e\n \u003cp\u003ewhere \u003cem\u003eL\u003c/em\u003e\u003csub\u003e\u003cem\u003eS\u003c/em\u003e\u003c/sub\u003e refers to the emission spectrum of the sample, \u003cem\u003e\u0026epsilon;\u003c/em\u003e is the absorption efficiency, \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eS\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eR\u003c/em\u003e\u003c/sub\u003e represent the spectra of excitation light with and without the sample in the integrating sphere, respectively. For the optimal h-BN:0.025Tb\u003csup\u003e3+\u003c/sup\u003e, 0.05Ce\u003csup\u003e3+\u003c/sup\u003e sample, the \u003cem\u003eIQE\u003c/em\u003e and \u003cem\u003eEQE\u003c/em\u003e are measured to be 52.1% and 14.6%, respectively, as shown in Fig. S5. Additionally, the \u003cem\u003eIQE\u003c/em\u003e of the commercially available silicate S525 green phosphor was measured under the same test conditions, found to be 77.8%. Although the quantum efficiency of h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e phosphor may be lower than that of commercial green phosphors, it can be enhanced through the optimization of activator concentration and preparation conditions. Therefore, the Tb\u003csup\u003e3+\u003c/sup\u003e/Ce\u003csup\u003e3+\u003c/sup\u003e co-doped h-BN green phosphor can be used for solid state lighting and fluorescent labeling [\u003cspan class=\"CitationRef\"\u003e56\u003c/span\u003e].\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Conclusion","content":"\u003cp\u003eUsing melamine as nitrogen source, a series of h-BN phosphors were prepared by conventional solid-state reaction method. When the sample was doped solely with Tb\u003csup\u003e3+\u003c/sup\u003e or Ce\u003csup\u003e3+\u003c/sup\u003e, impurities were observed at lower dopant concentrations, such as TbBO\u003csub\u003e3\u003c/sub\u003e or Ce(BO\u003csub\u003e2\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e. Conversely, co-doping of Tb\u003csup\u003e3+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e makes h-BN maintain its monocrystalline phase even at high doping concentrations. Tb\u003csup\u003e3+\u003c/sup\u003e or Ce\u003csup\u003e3+\u003c/sup\u003e can successfully enter the lattice gap between BN layers, resulting in a slight lattice distortion and an increase in the crystal plane spacing along the c-axis. Under excitation at 302 nm, h-BN:Ce\u003csup\u003e3+\u003c/sup\u003e phosphor exhibits an asymmetric emission band centered at 406 nm. Due to the forbidden \u003cem\u003ef\u003c/em\u003e-\u003cem\u003ef\u003c/em\u003e transition of Tb\u003csup\u003e3+\u003c/sup\u003e, the h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e phosphor exhibits limited emission under UV radiation. Moreover, under 302 nm excitation, h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e phosphors have strong green emission at 488 nm, 541 nm, 583 nm and 620 nm, corresponding to 5D\u003csub\u003e4\u003c/sub\u003e \u0026rarr; 7F\u003csub\u003eJ\u003c/sub\u003e (J\u0026thinsp;=\u0026thinsp;6, 5, 4, 3) electron transition of Tb\u003csup\u003e3+\u003c/sup\u003e. Ce\u003csup\u003e3+\u003c/sup\u003e ions are used as sensitizers for Tb\u003csup\u003e3+\u003c/sup\u003e activators in the energy transfer process. The energy transfer efficiency was about 55% when the ratio of [Tb\u003csup\u003e3+\u003c/sup\u003e]/[Ce\u003csup\u003e3+\u003c/sup\u003e] was 0.5, and remained relatively stable with the increase of activator concentration. The fluorescence lifetime of phosphors increased with the increase of activator concentration. Specifically, the fluorescence lifetime of h-BN:0.025Tb\u003csup\u003e3+\u003c/sup\u003e, 0.05Ce\u003csup\u003e3+\u003c/sup\u003e reaches 2.087 ms. Besides, the phosphor has a high activation energy value of approximately 0.2825 eV, indicating that h-BN phosphors have excellent thermal stability. Moreover, the PL quantum yield of h-BN:0.025Tb\u003csup\u003e3+\u003c/sup\u003e, 0.05Ce\u003csup\u003e3+\u003c/sup\u003e reaches 52.1%. Therefore, the phosphor shows potential as a green phosphor for solid state lighting and fluorescent labeling.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLunshuai\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eNie:\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003eConceptualization, Software, Data curation, Writing\u0026ndash;original draft, Methodology, Investigation. \u003cstrong\u003eKai Jia:\u003c/strong\u003e Conceptualization, Formal analysis, Software, Validation. \u003cstrong\u003eHongguang Guo:\u0026nbsp;\u003c/strong\u003eData curation, Investigation, Writing\u0026ndash;original draft. \u003cstrong\u003eJiaqin He:\u0026nbsp;\u003c/strong\u003eInvestigation, Methodology. \u003cstrong\u003eZhehui Weng and Yizhou Li:\u0026nbsp;\u003c/strong\u003eResources, Supervision, Validation. \u003cstrong\u003eHaidong Ju:\u0026nbsp;\u003c/strong\u003eFunding acquisition, Resources, Supervision, Writing\u0026ndash;review \u0026amp; editing. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was financially supported by the National Natural Science Foundation of China (NSFC) (No.\u0026nbsp;22165016,\u0026nbsp;22066014), Applied Basic Research Foundation of Yunnan Province (No.\u0026nbsp;2018FH001-008), Reserve Talents of Young and Middle-aged Academic and Technical Leaders in Yunnan Province (No. 202205AC160042),\u0026nbsp;the Yunnan Provincial Education Department Scientific Research Fund Project of Yunnan Province (No. 2022Y740), and\u0026nbsp;Innovative Research Teams (in Science and Technology) in the University of Yunnan Province (IRTSTYN).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data that support the findings of this study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics Approval\u0026nbsp;\u003c/strong\u003eThis paper meets the ethical standards of this journal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interest\u0026nbsp;\u003c/strong\u003eThe authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis paper allows which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. 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Ceram Int 49:26420\u0026ndash;26427. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1016/j.ceramint.2023.05.178\u003c/span\u003e\u003cspan address=\"10.1016/j.ceramint.2023.05.178\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-fluorescence","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jofl","sideBox":"Learn more about [Journal of Fluorescence](https://www.springer.com/journal/10895)","snPcode":"10895","submissionUrl":"https://submission.nature.com/new-submission/10895/3","title":"Journal of Fluorescence","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Hexagonal boron nitride, Co-doping, Ce3+ and Tb3+, Energy transfer, Green phosphor","lastPublishedDoi":"10.21203/rs.3.rs-3872075/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3872075/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn the paper, we have successfully prepared hexagonal boron nitride (h-BN) phosphors with melamine as the nitrogen source. The X-ray powder diffraction patterns confirm that the sample possesses a hexagonal crystal structure within the P\u003cspan class=\"InlineEquation\"\u003e\u003c/span\u003em2 space group. It is interesting that the co-doping combination of Tb\u003csup\u003e3+\u003c/sup\u003e and Ce\u003csup\u003e3+\u003c/sup\u003e can markedly enhance the threshold concentration of doped activators within the limited solid solution of h-BN phosphors. Under 302 nm excitation, the h-BN:Ce\u003csup\u003e3+\u003c/sup\u003e phosphors exhibit broadband blue light emission at 406 nm. In h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e phosphors, the co-doping of Ce\u003csup\u003e3+\u003c/sup\u003e not only ensures high phase purity but also results in strong green light emission. The energy transfer efficiency from Ce\u003csup\u003e3+\u003c/sup\u003e to Tb\u003csup\u003e3+\u003c/sup\u003e is about 55%. The fluorescence lifetime increases with the increase of Ce\u003csup\u003e3+\u003c/sup\u003e and Tb\u003csup\u003e3+\u003c/sup\u003e concentration, and the fluorescence lifetime of h-BN:0.025Tb\u003csup\u003e3+\u003c/sup\u003e, 0.05Ce\u003csup\u003e3+\u003c/sup\u003e phosphor reached 2.087 ms. Additionally, the h-BN:0.025Tb\u003csup\u003e3+\u003c/sup\u003e, 0.05Ce\u003csup\u003e3+\u003c/sup\u003e phosphor exhibits excellent thermal performance with an activation energy value of 0.2825 eV. Moreover, the photoluminescence quantum yield of the sample exceeds 52%. Therefore, the h-BN:Tb\u003csup\u003e3+\u003c/sup\u003e, Ce\u003csup\u003e3+\u003c/sup\u003e samples can be used as green phosphors for solid state lighting and fluorescent labeling.\u003c/p\u003e","manuscriptTitle":"Effect of Tb3+ and Ce3+ co-doping on the structural stability and photoluminescence properties of hexagonal boron nitride phosphors","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-01-24 18:51:22","doi":"10.21203/rs.3.rs-3872075/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-02-08T15:14:36+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-02-06T13:59:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"6fd33323-5e01-4332-bd33-9875d0cfb5e2","date":"2024-01-29T16:29:45+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-01-29T12:45:41+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-01-29T12:44:23+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-01-22T05:25:49+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Fluorescence","date":"2024-01-17T06:28:38+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-fluorescence","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jofl","sideBox":"Learn more about [Journal of Fluorescence](https://www.springer.com/journal/10895)","snPcode":"10895","submissionUrl":"https://submission.nature.com/new-submission/10895/3","title":"Journal of Fluorescence","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"ccd333cc-7792-401e-9932-a8e2f8f43114","owner":[],"postedDate":"January 24th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-03-25T15:11:09+00:00","versionOfRecord":{"articleIdentity":"rs-3872075","link":"https://doi.org/10.1007/s10895-024-03663-3","journal":{"identity":"journal-of-fluorescence","isVorOnly":false,"title":"Journal of Fluorescence"},"publishedOn":"2024-03-23 15:01:22","publishedOnDateReadable":"March 23rd, 2024"},"versionCreatedAt":"2024-01-24 18:51:22","video":"","vorDoi":"10.1007/s10895-024-03663-3","vorDoiUrl":"https://doi.org/10.1007/s10895-024-03663-3","workflowStages":[]},"version":"v1","identity":"rs-3872075","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3872075","identity":"rs-3872075","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}