Article Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
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Enhanced Persistence Properties through Modifying the Trap Depth and Density in Y3Al2Ga3O12:Ce3+,Yb3+ Phosphor by Co-doping B3+ Dandan Zhou, Zhizhen Wang, Zhen Song, Feixiong Wang, Shiyou Zhang, and Quanlin Liu*
Inorg. Chem. Downloaded from pubs.acs.org by UNITED ARAB EMIRATES UNIV on 01/08/19. For personal use only.
The Beijing Municipal Key Laboratory of New Energy Materials and Technologies, School of Materials Sciences and Engineering, University of Science and Technology Beijing, Beijing 100083, China ABSTRACT: Long persistence phosphors with high emitting intensity are promising materials for safety signage and energy storage applications. Herein, an improved persistent luminescence of Y3Al2Ga3O12 phosphor by co-doping Ce3+, Yb3+, and B3+ is achieved using conventional solid-state reaction. On one hand, the incorporation of H3BO3 can improve the crystallinity; on the other hand, B3+ can replace Al3+/Ga3+ in tetrahedral sites in the host lattice, causing lattice contraction and modifying the trap depth and density. It is found that adding B3+ forms a much deeper trap with ∼1.10 eV depth. In addition, the density of the electron trap can also be dramatically increased compared to the sample without B3+. The charging process for persistent luminescence is demonstrated by comparing the photoluminescence excitation spectrum with the thermoluminescence excitation spectrum. The persistence luminescence mechanism is given by a visual energy level diagram on the basis of the vacuum referred binding energy scheme of Y3Al2Ga3O12.
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INTRODUCTION Persistent luminescence (PersL) is continuous luminescence that can last for minutes, hours, or even days after ceasing the stimulations.1−3 Owing to their specific optical phenomenon, many persistent phosphors have been successfully used in applications such as emergency lighting,4 vivo bioimaging,5−7 and optical information storage.8−10 The most widely used persistent phosphor SrAl2O4:Eu2+,Dy3+ with bright green persistent luminescence (λem = 510 nm) was first discovered by Matsuzawa et al. in 1996.11 Since then, many other aluminates, silicates, and nitrides based phosphors doped with Eu2+, Ce3+, or Mn2+ as luminescence center and Dy3+, Nd3+, or other rare earth ions as carrier trapping center have become increasingly popular, such as Sr4Al14O25:Eu2+,Dy3+,12 β-Zn3(PO4)2:Mn2+,13 and M2Si5N8:Eu2+,Tm3+ (M = Ca, Ba).14,15 Although experimental and theoretical studies have been devoted to enhance the luminescent color range, initial intensity, and persistent duration, however, only a few sulfide and nitride phosphors could be excited by visible blue light (∼450 nm) with poor persistence properties.15−17 In order to extend the color range and create a white display of long persistence, the red and yellow persistent luminescences induced by not only UV and violet light but also longwavelength light are still highly demanded. We have once extended the persistent duration and the excitation to longer wavelength by Na+-Nb5+ substituting for Ca2+-Ti4+ in CaTiO3:Pr3+ phosphor.18 Recently, Ce3+-doped garnet phosphors, (A)3[B2]{C3}O12:Ce3+ used as visible phosphors in conventional white LEDs, have received extensive attention owing to their high luminous efficiency, long lifetime, and energy-saving capability as indoor illumination.19−22 The garnet phosphor powders © XXXX American Chemical Society
with excellent morphology can also be successfully synthesized, improving better performance in WLED devices.21 Moreover, the garnet structure (space group Ia3̅d) with rigid interpenetrated sublattices makes it stable in thermal luminescence quenching.23 All of these peculiarities allow this yellow phosphor to have great promise for the persistent phosphor in white-LED illuminations. Originally, Holloway and Kestigian have observed the PersL phenomenon in Y3Al2Ga3O12:Ce3+ and Y3Al1.5Ga3.5O12:Ce3+ excited by UV light with duration time for a few seconds.24 About 40 years later, Kanai et al. reported another phosphor Gd3+d(Al, Ga)5−dO12:Ce3+ which persisted for milliseconds under X-ray excitation.25 The brightness and durations were still rather limited. A breakthrough was made by Ueda et al.26 in 2011; they reported a garnet structural phosphor Y3Sc2Ga3O12:Ce3+ with several hours of PersL. Whereafter, a series of garnet persistent phosphors doping with different ions with enhanced properties were reported, for instance, YAGG:Ce3+,Cr3+,27 YAGG:Ce3+,Yb 3+ ,28 and YAGG:Ce 3+ ,V 3+ .9 In the three persistent phosphors mentioned above, the co-doping element Cr3+, Yb3+, or V3+ as trapping center can form deeper electron traps and dramatically enhance the duration. Wang et al.29 have presented Y3Al5−xGaxO12 (x = 0−5):Ce3+ samples with the addition of Pr3+, resulting in prolonging the duration time and adding red-emissive components, and they also make much effort in AC-LED using garnet structural persistent phosphors.30,31 In our previous work, we found that a negative correlation exists between temperature-dependent luminescence and persistent luminescence with gallium content Received: November 23, 2018
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DOI: 10.1021/acs.inorgchem.8b03270 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry
Instrument Co. Ltd., Hangzhou, China) with a 1000 lx artificial light source. The samples were irradiated for 10 min; then the measurements commenced after 1 s as soon as the excitation is stopped. The persistent luminance time was counted until the intensity reaches to 2 mcd/m2. Thermoluminescence (TL) curves were measured with an SL08 system (Ai-dirui-sheng Company, Guangzhou, China) in the temperature range between 35 and 350 °C, with a heating rate of 1 °C/s. The thermoluminescence excitation spectra (TLEs) were carried out with a self-improved system, combined with the FLS 920 fluorescence spectrophotometer (Edinburgh Instruments Ltd., U.K.) equipped with a 150 W xenon lamp as the excitation source and an SL08 system. The TLEs is composed of a series of integral TL curves which were obtained under particular excitation from 300 to 500 nm with the interval about 20 nm. Detailed information about the TLE test has been reported in the previous work by Bos et al.47
variation, and theoretical calculations reveal that oxygen vacancies provide trap levels which implement the persistent luminescence.32 Note that introducing deficiencies and co-doping other elements, such as B3+, Zn2+, and Lu3+,33−35 are good ways to improve the PersL properties. Among these candidates, B3+ is one of the most attractive ones in many fields, such as improving the scintillation performance,36−38 increasing the luminescent intensity,39,40 and prolonging the PersL duration.33,41 It is worth mentioning that, except the effect on the optical properties, the crystallinity can also be enhanced by adding B2O3 or H3BO3 as flux.42 Recently, we have successfully synthesized the nitrides Sr2Si5N8:Eu2+ with improved PersL property under the participation of H3BO3.43 Despite that much endeavor has been focused on improving the preparation, luminescent performance, and PersL property of the phosphors, however, to the best of our knowledge, whether B3+ can improve the PersL of these garnet structural materials has not been reported yet. Kang et al. have reported the enhanced luminescence intensity of Gd3Ga2Al3O12:Ce3+ with the addition of B3+ ions,44 but did not mention the effect on PersL property. Recently, we have devoted to study the PersL mechanism in several phosphors, including Y3Al5−xGaxO12:Ce3+ (x = 0−5), and explain the persistence mechanism using the Dorenbos model. 45 Herein, we successfully synthesized B3+ co-doped Y3Al2Ga3O12:Ce3+,Yb3+ with high crystallizaton and improved PersL property and the influence of B3+ is explored. Moreover, we investigate the source of ionized electrons in Y3Al2Ga3O12:Ce3+,Yb3+,xB3+ and then explain the PersL mechanism via a visual energy level diagram.
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RESULTS AND DISCUSSION Figure 1a displays the observed XRD profiles of all the samples along with the magnified range of 32−34°. It can be obviously
EXPERIMENTAL SECTION
A series of Y3Al2Ga3O12:Ce3+,Yb3+ with different H3BO3 content were synthesized by a solid-state reaction method. The concentration of Ce3+ and Yb3+ was 0.5% and 0.1%, respectively, the same as the previous report.28 Stoichiometric amounts of Y2O3 (A.R.), Yb2O3 (A.R.), Al2O3 (>99.99%), Ga2O3 (99.99%), CeO2 (A.R.), and H3BO3 (≥99.5%) were thoroughly mixed and ground in an agate mortar. Then the mixture was transferred into an alumina crucible and positioned in a graphite furnace with a high-purity nitrogen atmosphere to fire at 1450 °C under 0.7 MPa for 4 h. The obtained samples were naturally cooled down to room temperature, and ground with a mortar. Then the powders were washed several times using distilled water and hydrochloric acid solution (pH ≈ 4), thereafter dried in a vacuum oven at 60 °C for 12 h. All the samples after postprocessing were used for further characterization. The final precipitates obtained were denoted with Y3Al2Ga3O12:Ce3+,Yb3+,xB3+, where x was the H3BO3-doped mass concentrations varying as 0, 0.5%, 1%, 2%, 5%, and 10%. The morphology of the samples was determined by a scanning electron microscope (SEM, JEOL JSM-6510). The powder X-ray diffraction (XRD) patterns were carried out on a D8 Advance diffractometer (Bruker Corporation, Germany) operating at 40 kV and 40 mA with monochromatized Cu Kα radiation (λ = 1.5406 Å). Crystal structure solving and Rietveld refinements were performed using the Fullprof Suite package.46 The photoluminescence (PL) and PL excitation (PLE) spectra were recorded using an FLS 920 fluorescence spectrophotometer (Edinburgh Instruments Ltd., U.K.), equipped with a 150 W xenon lamp as the excitation source. The PL spectra in the range of 300−700 nm were measured using a photomultiplier tube operating at 400 V covered with a 445 nm filter. Meanwhile, the NIR spectra in the range of 900−1150 nm were tested using an InGaAs detector covered with a 645 nm filter. All the PL spectra were calibrated by a built-in file “Emission Correction R”. The persistent luminance (mcd/m2) was measured by using a PR 305 persistent luminance instrument (Zhejiang University Sensing
Figure 1. (a) The XRD patterns of Y3Al2Ga3O12:Ce3+,Yb3+,xB3+, with x varying from 0 to 10%. The standard data is Y3Al2Ga3O12 phase (ICSD# 280107); magnified XRD curves in the range of 32−34° are displayed laterally. (b) Crystal structure of Y3Al2Ga3O12 and the coordination environments for Y3+, Al3+, Ga3+, Yb3+, Ce3+, and B3+ are given. Among these ions, B3+ prefers to stay in a tetrahedral site.
concluded by comparing the Bragg positions with the standard pattern that all the samples can be indexed based on the cubic (Ia3̅d) Y3Al2Ga3O12 phase (ICSD# 280107). However, as the content of H3BO3 increases to 5%, an additional Bragg reflection (corresponding probably to YBO3) is observed at ca. 20°, of which amount could be ignored. It is noted that the Bragg reflections are narrowed and their intensities are increased after adding H3BO3, implying H3BO3 can act as a high temperature solvent (flux) to accelerate grain growth and improve the crystallinity. The typical SEM images displayed in Figure 2 exhibit that the uniform particles with the size of several microns to tens of microns were observed, which B
DOI: 10.1021/acs.inorgchem.8b03270 Inorg. Chem. XXXX, XXX, XXX−XXX
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Inorganic Chemistry
Figure 2. SEM images of Y3Al2Ga3O12:Ce3+,Yb3+,xB3+: (a) x = 0, (b) x = 0.5%, (c) x = 1%, (d) x = 2%, (e) x = 5%, and (f) x = 10% samples.
Figure 3. PL and PLE spectra of Y3Al2Ga3O12:Ce3+,Yb3+,xB3+ samples. PL spectra excited by 432 nm and PLE spectra monitoring the luminescence at 520 nm.
areconsistent with the variation tendency of XRD result. In addition, the diffraction peaks are slightly shifted to higher angles as a function of boron concentration as plotted in magnified patterns in Figure 1a, indicating a lattice contraction. To explicitly prove the effect of B3+ on the crystal structure, the Rietveld refinements have been performed using the FullProf program,46 and detailed crystal structure information are obtained. Lattice parameters (a) of all samples are extracted and listed in Table 1. It could be obviously seen that the
through the nonequivalent substitution of Si4+ ions which store a part of the excitation energy, leading to the decrease of the emission intensity.43 However, equivalent substitution between B3+ and Al3+ proceeds in the Y3Al2Ga3O12 host, so the defects compensating for the excessive charge cannot be formed. Since the ionic radius of B3+ is much smaller than that of Al3+, the irregularity of the coordination polyhedron of the dopant site can increase, which could lead to a strong local strain. Then the strain could be partially released by forming trigonal planar units BO3, which tends to the formation of oxygen vacancy and finally decreases the emission intensity.33,42 To understand the PersL properties of the Y3Al2Ga3O12:Ce3+,Yb3+,B3+ phosphor, the measurements of PersL decay curves are performed after visible light irradiation for 10 min, as shown in Figure 4. It is evident that the duration of
Table 1. Lattice Parameters of Y3Al2Ga3O12:Ce3+,Yb3+,xB3+ x%
a (Å)
0 0.5 1 2 5 10
12.1829(4) 12.1780(2) 12.1713(2) 12.1624(3) 12.1599(2) 12.1583(2)
lattices are shrinking on increasing H3BO3 concentration. An analogous phenomenon of a SrAl2O4 host has been reported by Whangbo et al.33 and Niittykoski et al.42 Given the structure evidence and the ionic radius matching rule, we consider that Yb3+ and Ce3+ ions are located in the Y3+ site and a small amount of B3+ ions (r = 0.11 Å, CN = 4) are reasonably expected to occupy Al3+ (r = 0.39 Å, CN = 4) or Ga3+ (r = 0.47 Å, CN = 4) at a tetrahedral site, shown in Figure 1b. However, the precise content has not yet been known. The room-temperature PL spectra excited by 432 nm and the PLE spectra monitoring 520 nm of Y3Al2Ga3O12:Ce3+,Yb3+ with different B3+ concentrations are depicted in Figure 3 The strong green luminescence band peaked at 520 nm is corresponding to transitions from the lowest 5d1 energy level to the 4f energy levels of Ce3+. In the PLE spectra, there are two bands at around 432 and 350 nm, which are attributed to the transitions of Ce3+ ion from the ground 4f level to the lowest 5d1 level and the second lowest 5d (5d2) level, respectively. In addition to the Ce3+: 5d1 → 4f band, sharp PL lines at around 1025 nm of the Yb3+: 2F5/2 → 2F7/2 transitions due to energy transfer from Ce3+ to Yb3+ are observed under 432 nm excitation, which is consistent with a previous result reported by Ueda et al.28 The introduction of B3+ can hardly change the emission position and profile. However, the intensity is gradually decreasing with more B3+ content. It was suggested in our previous report of Sr2 Si5N8:Eu2+ phosphor that the addition of B3+ can create extra defects
Figure 4. PersL decay curves of Y3Al2Ga3O12:Ce3+,Yb3+,xB3+ samples, excited for 10 min under visible light.
Y3Al2Ga3O12:Ce3+,Yb3+ is dramatically prolonged with increasing B3+ content. The variation trend of the persistent luminance is different from the steady-state emission. The duration upon 2 mcd/m2 of Y3Al2Ga3O12:Ce3+,Yb3+ with 10% H3BO3 is almost 47 times longer than that of the sample without B3+. Note that the luminance value 2 mcd/m2 is the minimum value in use for emergency signs set by the Japan Industry Standard for luminance 60 min after excitation has C
DOI: 10.1021/acs.inorgchem.8b03270 Inorg. Chem. XXXX, XXX, XXX−XXX
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Inorganic Chemistry ceased.48 On the contrary, with the B3+ concentration increasing, the initial intensity of the persistent luminance, which corresponds to the electron trap density, gradually decreases. These results indicate that the PersL decay rate, which corresponds to the slope, becomes slower on increasing B3+ content. The deeper electron trap causes a slower detrapping rate.28 Thus, as we expect, the deeper electron trap and higher electron trap density have been successfully achieved by introducing appropriate B3+. To examine the significant effect of B3+ on the PersL property, TL glow curves are recorded. The captured electrons can escape from traps under higher temperature; therefore, the TL glow curves can qualitatively reveal the characteristic of the trap and then clarify the PersL properties. As displayed in Figure 5a, one broad TL band ranging from 300 to 500 K is
1.10 eV than both Y3Al2Ga3O12:Ce3+,Yb3+ (1.01 eV)28 and Y3Al2Ga3O12:Ce3+,Cr3+ (0.81 eV).27 Similar evidence was found in SrAl2O4 containing Eu2+, Dy3+, and B3+ ions;33 they consider the replacement of Al3+ by B3+ can lead to extra peaks in TL. Moreover, B3+ has a higher ionization potential than does Al3+ (259.8 eV vs 120.2 eV), so the strong participation of the orbitals of B3+ can also cause a slight change in the trap depth.42 The probable PersL mechanism for Y3Al2Ga3O12:Ce3+,Yb3+,xB3+ will be discussed in this section. The widely adopted mechanism of PersL proposed by Dorenbos45 states that the excited 5d electrons can easily be thermally activated into the conduction band (CB) and subsequently captured by a trap and then be thermally released from the trap. On the basis of this theory, Bos et al.47 have studied the photoionization processes and proved the source of charge carriers liberated during exposure using TLEs. By comparing TLEs with PLE spectra, they conclude that the ionized electron can not only from exciting electrons in occupied impurity states (donor states) but also be directly excited from the valence band to unoccupied impurity states (acceptor states). In order to explain the PersL mechanism and demonstrate whether the thermal ionization is from the excited 5d state in Y3Al2Ga3O12:Ce3+,Yb3+,xB3+, we collected the TLEs displayed in Figure 6a, together with the PLE spectrum of Ce3+: 5d1 → 4f
Figure 5. (a) TL glow curves of all the samples. The insets show the magnified pattern of the sample without B3+. (b) The normalized results of all the samples.
observed in all the samples. These TL peaks, assigned to Yb3+ in the garnet crystal reported before,28 shift to higher temperature with higher B3+ content, as visually shown in Figure 5b. Moreover, an additional intense TL peak between 500 and 650 K appears when the concentration of H3BO3 is greater than 2%. It is well-known that different TL peaks correspond to different trap energy levels, and the proper adjustment of the trap can lead to longer decay time. In this consideration, another deeper electron trap may probably be created with higher B3+ content. The trap depth, shown in
Figure 6. (a) Normalized PLE spectrum and TLEs of the sample with 2% H3BO3. (b) The vacuum referred binding energy (VRBE) diagram showing the PersL mechanism of Y 3 Al 2 Ga 3 O 12 :Ce 3+ ,Yb 3+ ,B 3+ phosphor, include the energy levels of Ce3+: 4f, 5d and selected electron traps in the Y3Al2Ga3O12 host. The trap level moves deeply after the addition of B3+, from 0.69 to 1.10 eV.
Table 2. Trap Depth of Y3Al2Ga3O12:Ce3+,Yb3+,xB3+ x%
0
0.5
1
2
5
10
trap depth (eV)
0.69
0.69
0.69
0.72
0.73 1.10
0.74 1.10
emission. The observation apparently shows that both spectra are almost the same in peak positions, and this suggests that, during the charging process for PersL, the electrons in the 4f ground state are first excited to the 5d level and then thermally stimulated to the conduction band. However, the relative intensity of the two peaks for TLEs is apparently different from that for PLEs; the explanation of this phenomenon will be given in the next part. According to the comparison of TLEs and PLE spectra, the source of released electron of Y3Al2Ga3O12:Ce3+,Yb3+,xB3+ can be clearly known. In order to demonstrate the PersL mechanism visually, an energy level diagram is constructed in Figure 6b. With all the electronic structure information, the band gap between the top of the valence band and bottom of the conduction band is calculated to be 7.01 eV, consistent with previous reports.50 With the previously reported electronic structure data of Y3Al2Ga3O12, the binding energy of the valence band top EV (−9.14 eV),51 the charge transfer (CT) energy Evf (3.63 eV),50,52 and the energy differences EdC
Table 2, is estimated based on the method proposed by Randall and Wilkins as follows49 ε = Tm/500
(1)
where ε is the trap depth (eV), and Tm is the peak position of the TL glow curve (K). Comparing to the sample without B3+, inserted in Figure 5a, the TL intensity is dramatically increased with increasing B3+ content, indicating that the trap density is increased simultaneously. By combining all the data, we speculate that the improved PersL performance is on account of the cooperation of B3+, which promotes the formation of another new deeper trap level in Y3Al2Ga3O12:Ce3+,Yb3+,xB3+. Co-doping with B3+ makes a much deeper electron trap with D
DOI: 10.1021/acs.inorgchem.8b03270 Inorg. Chem. XXXX, XXX, XXX−XXX
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Inorganic Chemistry (0.51 eV)51 between conduction band and the lowest 5d level are all compiled in the diagram. The preceding research has proved that the valence band can move upward and the conduction band moves downward with 60% Ga fraction in Y3Al5−xGaxO12, which results in the decrease of the band gap compared to that of Y3Al5O1.27,32 Considering the change of band gap, the excited 5d2 level of Ce3+ is located in the conduction band, and the 5d1 level stays closely under the conduction band. The energy gap between the ground 4f level and the two lowest 5d levels of Ce3+ can be accurately acquired from the PLE spectra, which is 2.87 and 3.62 eV, respectively. We have listed all the trap levels formed in this phosphor in Table 2, and placed the shallowest one (0.69 eV) and the new deepest one (1.10 eV) in the energy level scheme. In the process of charging, plenty of electrons can be excited from the 4f ground state to the 5d1 and 5d2 states under the visible light irradiation. Due to the proximity to the host’s conduction band (since the 5d2 level is located in CB), some excited electrons can easily escape from 5d1 states aided by thermal activation to the conduction band of Y3Al2Ga3O12, in which some excited electrons can move freely until captured by the trap. In the detrapping process, these electrons captured by the diverse traps are released under thermal stimulation at proper temperature and then recaptured by luminescent ions. Since the excited 5d2 level is just located in the CB, the electrons in this level are more easily released into the CB and then recaptured by the trap, which can well explain the different relative intensity of 5d2 to 5d1 in Figure 6a. Ultimately, the recaptured electrons transfer to the ground state, then produce the PersL.
Fundamental Research Funds for the Central Universities (FRF-TP-17-005A2).
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(1) Van den Eeckhout, K.; Smet, P. F.; Poelman, D. Persistent luminescence in Eu2+-doped compounds: a review. Materials 2010, 3, 2536−2566. (2) Van den Eeckhout, K.; Poelman, D.; Smet, P. F. Persistent Luminescence in Non-Eu2+-Doped Compounds: A Review. Materials 2013, 6, 2789−2818. (3) Li, Y.; Gecevicius, M.; Qiu, J. Long persistent phosphors-from fundamentals to applications. Chem. Soc. Rev. 2016, 45, 2090−2136. (4) Botterman, J.; Smet, P. F. Persistent phosphor SrAl2O4: Eu, Dy in outdoor conditions: saved by the trap distribution. Opt. Express 2015, 23, A868−A881. (5) Maldiney, T.; Bessière, A.; Seguin, J.; Teston, E.; Sharma, S. K.; Viana, B.; Bos, A. J.; Dorenbos, P.; Bessodes, M.; Gourier, D.; Scherman, D.; Richard, C. The in vivo activation of persistent nanophosphors for optical imaging of vascularization, tumours and grafted cells. Nat. Mater. 2014, 13, 418. (6) Li, Z.; Zhang, Y.; Wu, X.; Huang, L.; Li, D.; Fan, W.; Han, G. Direct aqueous-phase synthesis of sub-10 nm “luminous pearls” with enhanced in vivo renewable near-infrared persistent luminescence. J. Am. Chem. Soc. 2015, 137, 5304−5307. (7) Zhou, Z.; Zheng, W.; Kong, J.; Liu, Y.; Huang, P.; Zhou, S.; Chen, Z.; Shi, J.; Chen, X. Rechargeable and LED-activated ZnGa2O4: Cr3+ near-infrared persistent luminescence nanoprobes for background-free biodetection. Nanoscale 2017, 9, 6846−6853. (8) Xu, X.; Yan, L.; Yu, X.; Yu, H.; Jiang, T.; Jiao, Q.; Qiu, J. Concentration-dependent effects of optical storage properties in CSSO: Dy. Mater. Lett. 2013, 99, 158−160. (9) Li, W.; Zhuang, Y.; Zheng, P.; Zhou, T.; Xu, J.; Ueda, J.; Tanabe, S.; Wang, L.; Xie, R. Tailoring Trap Depth and Emission Wavelength in Y3Al5−xGaxO12: Ce3+, V3+ Phosphor-in-Glass Films for Optical Information Storage. ACS Appl. Mater. Interfaces 2018, 10, 27150− 27159. (10) Zhuang, Y.; Wang, L.; Lv, Y.; Zhou, T. L.; Xie, R. Optical Data Storage and Multicolor Emission Readout on Flexible Films Using Deep-Trap Persistent Luminescence Materials. Adv. Funct. Mater. 2018, 28, 1705769. (11) Matsuzawa, T.; Aoki, Y.; Takeuchi, N.; Murayama, Y. A New Long Phosphorescent Phosphor with High Brightness, SrAl2O4: Eu2+, Dy3+. J. Electrochem. Soc. 1996, 143, 2670−2673. (12) Lin, Y.; Tang, Z.; Zhang, Z.; Nan, C. W. Anomalous luminescence in Sr4Al14O25: Eu, Dy phosphors. Appl. Phys. Lett. 2002, 81, 996−998. (13) Wang, J.; Wang, S.; Su, Q. Synthesis, photoluminescence and thermostimulated-luminescence properties of novel red long-lasting phosphorescent materials β-Zn3(PO4)2: Mn2+, M3+ (M = Al and Ga). J. Mater. Chem. 2004, 14, 2569−2574. (14) Li, J.; Lei, B.; Qin, J.; Liu, Y.; Liu, X. Temperature-Dependent Emission Spectra of Ca2Si5N8: Eu2+, Tm3+ Phosphor and its Afterglow Properties. J. Am. Ceram. Soc. 2013, 96, 873−878. (15) Höppe, H.; Lutz, H.; Morys, P.; Schnick, W.; Seilmeier, A. Luminescence in Eu2+-doped Ba2Si5N8: fluorescence, thermoluminescence, and upconversion. J. Phys. Chem. Solids 2000, 61, 2001− 2006. (16) Botterman, J.; Van den Eeckhout, K.; Bos, A. J.; Dorenbos, P.; Smet, P. F. Persistent luminescence in MSi2O2N2: Eu phosphors. Opt. Mater. Express 2012, 2, 341−349. (17) Jia, D. Enhancement of Long-Persistence by Ce Co-Doping in CaS: Eu2+, Tm3+ Red Phosphor. J. Electrochem. Soc. 2006, 153, H198. (18) Zhang, R.; Song, Z.; He, L.; Xia, Z.; Liu, Q. Improvement of red-emitting afterglow properties via tuning electronic structure in perovskite-type (Ca1‑xNax)[Ti1‑xNbx]O3: Pr3+ compounds. J. Alloys Compd. 2017, 729, 663−670. (19) He, X.; Liu, X.; You, C.; Zhang, Y.; Li, R.; Yu, R. Clarifying the preferential occupation of Ga3+ ions in YAG:Ce,Ga nanocrystals with
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CONCLUSIONS In summary, we have prepared a series of Y3Al2Ga3O12:Ce3+,Yb3+ persistent phosphors co-doping with various amounts of B3+ by solid-state reaction. The H3BO3 addition can increase the crystallinity as flux; meanwhile, B3+ ions can replace Al3+/ Ga3+ randomly in the host lattice, modifying the trap depth and trap density. Y3Al2Ga3O12:Ce3+,Yb3+,B3+ phosphors can emit green persistent light (Ce3+: 5d → 4f) under the excitation of blue light, and show better persistence properties due to deeper trap depth and larger trap density compared to the sample without B3+. Furthermore, we confirm that, during the charging process for PersL, the electrons in the 4f ground state are first excited to the 5d level and then thermally stimulated to the conduction band and captured by the traps. Finally, the PersL mechanism is constructed in an energy level diagram, where the processes of charging and detrapping are clearly shown. The persistence phosphor Y3Al2Ga3O12:Ce3+,Yb3+,B3+ can be a promising candidate for potential applications.
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REFERENCES
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. ORCID
Quanlin Liu: 0000-0003-3533-7140 Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work is supported by the National Natural Science Foundation of China (Nos. 51672027 and 51602019) and E
DOI: 10.1021/acs.inorgchem.8b03270 Inorg. Chem. XXXX, XXX, XXX−XXX
Article
Inorganic Chemistry various Ga3+-doping concentrations by nuclear magnetic resonance spectroscopy. J. Mater. Chem. C 2016, 4, 10691−10700. (20) Xia, Z.; Meijerink, A. Ce3+-Doped garnet phosphors: composition modification, luminescence properties and applications. Chem. Soc. Rev. 2017, 46, 275−299. (21) Song, Z.; Liao, J.; Ding, X.; Liu, X.; Liu, Q. Synthesis of YAG phosphor particles with excellent morphology by solid state reaction. J. Cryst. Growth 2013, 365, 24−28. (22) Lin, H.; Wang, B.; Xu, J.; Zhang, R.; Chen, H.; Yu, Y.; Wang, Y. Phosphor-in-glass for high-powered remote-type white AC-LED. ACS Appl. Mater. Interfaces 2014, 6, 21264−21269. (23) George, N.; Pell, A. J.; Dantelle, G. r.; Page, K.; Llobet, A.; Balasubramanian, M.; Pintacuda, G.; Chmelka, B. F.; Seshadri, R. Local environments of dilute activator ions in the solid-state lighting phosphor Y3−xCexAl5O12. Chem. Mater. 2013, 25, 3979−3995. (24) Holloway, W.; Kestigian, M. Optical properties of ceriumactivated garnet crystals. J. Opt. Soc. Am. 1969, 59, 60−63. (25) Kanai, T.; Satoh, M.; Miura, I. Characteristics of a nonstoichiometric Gd3+δ(Al,Ga)5−δO12: Ce garnet scintillator. J. Am. Ceram. Soc. 2008, 91, 456−462. (26) Ueda, J.; Aishima, K.; Nishiura, S.; Tanabe, S. Afterglow luminescence in Ce3+-doped Y3Sc2Ga3O12 ceramics. Appl. Phys. Express 2011, 4, No. 042602. (27) Ueda, J.; Kuroishi, K.; Tanabe, S. Bright persistent ceramic phosphors of Ce3+-Cr3+-codoped garnet able to store by blue light. Appl. Phys. Lett. 2014, 104, 101904. (28) Ueda, J.; Miyano, S.; Tanabe, S. Formation of Deep Electron Trap by Yb 3+ Codoping Leads into Super-Long Persistent Luminescence in Ce3+-doped Yttrium Aluminum Gallium Garnet Phosphors. ACS Appl. Mater. Interfaces 2018, 10, 20652−20660. (29) Wang, B.; Lin, H.; Yu, Y.; Chen, D.; Zhang, R.; Xu, J.; Wang, Y. Ce3+/Pr3+: YAGG: A Long Persistent Phosphor Activated by BlueLight. J. Am. Ceram. Soc. 2014, 97, 2539−2545. (30) Lin, H.; Wang, B.; Huang, Q.; Huang, F.; Xu, J.; Chen, H.; Lin, Z.; Wang, J.; Hu, T.; Wang, Y. Lu2CaMg2(Si1−xGex)3 O12: Ce3+ solidsolution phosphors: bandgap engineering for blue-light activated afterglow applicable to AC-LED. J. Mater. Chem. C 2016, 4, 10329− 10338. (31) Lin, H.; Xu, J.; Huang, Q.; Wang, B.; Chen, H.; Lin, Z.; Wang, Y. Bandgap tailoring via Si doping in inverse-garnet Mg3Y2Ge3O12: Ce3+ persistent phosphor potentially applicable in AC-LED. ACS Appl. Mater. Interfaces 2015, 7, 21835−21843. (32) Song, Z.; Wang, Z.; He, L.; Zhang, R.; Liu, X.; Xia, Z.; Geng, W.; Liu, Q. After-glow, luminescent thermal quenching, and energy band structure of Ce-doped yttrium aluminum-gallium garnets. J. Lumin. 2017, 192, 1278−1287. (33) Clabau, F.; Rocquefelte, X.; Jobic, S.; Deniard, P.; Whangbo, M.-H.; Garcia, A.; Le Mercier, T. Mechanism of phosphorescence appropriate for the long-lasting phosphors Eu2+-doped SrAl2O4 with codopants Dy3+ and B3+. Chem. Mater. 2005, 17, 3904−3912. (34) Yuan, X.; Shi, X.; Shen, M.; Wang, W.; Fang, L.; Zheng, F.; Wu, X. Luminescent properties of Pr3+ doped (Ca, Zn) TiO3: Powders and films. J. Alloys Compd. 2009, 485, 831−836. (35) Zhang, X.; Zhang, J.; Zhang, X.; Chen, L.; Lu, S.; Wang, X.-J. Enhancement of red fluorescence and afterglow in CaTiO3: Pr3+ by addition of Lu2O3. J. Lumin. 2007, 122−123, 958−960. (36) Donnald, S. B.; Tyagi, M.; Rothfuss, H.; Meng, F.; Hayward, J. P.; Koschan, M.; Melcher, C. L. The Effect of B3+ and Ca2+ CoDoping on Factors Which Affect the Energy Resolution of Gd3Ga3Al2O12: Ce. IEEE Trans. Nucl. Sci. 2013, 60, 4002−4006. (37) Tyagi, M.; Meng, F.; Koschan, M.; Donnald, S. B.; Rothfuss, H.; Melcher, C. L. Effect of codoping on scintillation and optical properties of a Ce-doped Gd3Ga3Al2O12 scintillator. J. Phys. D: Appl. Phys. 2013, 46, 475302. (38) Foster, C.; Koschan, M.; Wu, Y.; Melcher, C. L. Boron codoping of Czochralski grown lutetium aluminum garnet and the effect on scintillation properties. J. Cryst. Growth 2018, 486, 126−129.
(39) Ma, J.; Qi, G.; Chen, Y.; Liu, S.; Cao, S.; Wang, X. Luminescence property of ZnAl2O4:Cr3+ phosphors co-doped by different cations. Ceram. Int. 2018, 44, 11898−11900. (40) Shu, W.; Qiang, R. F.; Xiao, S.; Yang, X.; Ding, J. W. Enhanced red emission in LiAl5O8: Fe3+ phosphor by B3+ doping. J. Alloys Compd. 2011, 509, 3886−3888. (41) Inan Akmehmet, G.; Š turm, S.; Bocher, L.; Kociak, M.; Ambrožič, B.; Ow-Yang, C. Structure and Luminescence in Long Persistence Eu, Dy, and B Codoped Strontium Aluminate Phosphors: The Boron Effect. J. Am. Ceram. Soc. 2016, 99, 2175−2180. (42) Niittykoski, J.; Aitasalo, T.; Hölsä, J.; Jungner, H.; Lastusaari, M.; Parkkinen, M.; Tukia, M. Effect of boron substitution on the preparation and luminescence of Eu2+ doped strontium aluminates. J. Alloys Compd. 2004, 374, 108−111. (43) Wang, S.; Song, Z.; Kong, Y.; Zhang, S.; Xia, Z.; Liu, Q. Enhanced performance of Sr2Si5N8: Eu2+ red afterglow phosphor by co-doping with boron and oxygen. J. Lumin. 2018, 204, 36−40. (44) Kang, J.-G.; Kim, M.-K.; Kim, K.-B. Preparation and luminescence characterization of GGAG: Ce3+, B3+ for a white light-emitting diode. Mater. Res. Bull. 2008, 43, 1982−1988. (45) Dorenbos, P. Mechanism of persistent luminescence in Eu2+ and Dy3+ codoped aluminate and silicate compounds. J. Electrochem. Soc. 2005, 152, H107−H110. (46) Roisnel, T.; Rodríquez-Carvajal, J. WinPLOTR: a windows tool for powder diffraction pattern analysis. Mater. Sci. Forum 2001, 378, 118−123. (47) Bos, A. J.; Van Duijvenvoorde, R. M.; Van der Kolk, E.; Drozdowski, W.; Dorenbos, P. Thermoluminescence excitation spectroscopy: A versatile technique to study persistent luminescence phosphors. J. Lumin. 2011, 131, 1465−1471. (48) Xu, J.; Ueda, J.; Kuroishi, K.; Tanabe, S. Fabrication of Ce3+− Cr3+ co-doped yttrium aluminium gallium garnet transparent ceramic phosphors with super long persistent luminescence. Scr. Mater. 2015, 102, 47−50. (49) Randall, J. T.; Wilkins, M. H. F.; Oliphant, M. L. E. Phosphorescence and electron traps-I. The study of trap distributions. Proc. R. Soc. London, Ser. A 1945, 184, 365−389. (50) Dorenbos, P. Electronic structure and optical properties of the lanthanide activated RE3(Al1−xGax)5O12 (RE = Gd, Y, Lu) garnet compounds. J. Lumin. 2013, 134, 310−318. (51) Mayolet, A. Etude des processus d’absorption et de transfert d’energie au sein de materiaux inorganiques luminescents dans le domaine uv et vu. Doctoral dissertation, Université Paris Sud-Paris XI, Paris, France, 1995. (52) Liu, L.; Young, J.; Smeu, M.; Halasyamani, P. S. Ba4B8TeO19: A UV Nonlinear Optical Material. Inorg. Chem. 2018, 57, 4771−4776.
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DOI: 10.1021/acs.inorgchem.8b03270 Inorg. Chem. XXXX, XXX, XXX−XXX
