Simultaneous adjustment of afterglow wavelength and intensity in indium-substituted Ga_1.99−xIn_xO₃:0.01Cr³⁺

Abstract

Near-infrared persistent luminescent nanoparticles (PLNPs) are widely used for deep tissue penetration in bio-imaging. Ga₂O₃:Cr³⁺, a promising phosphor material, has been extensively studied for its suitable band gap and tunable emission wavelength. Although a redshift in the fluorescence wavelength has been achieved, the persistent luminescence properties of Ga₂O₃:Cr³⁺ following this redshift have not been extensively explored. Herein, we have prepared Ga_1.99−xIn_xO₃:0.01Cr³⁺ (x = 0–1.99)(GIO) PLNPs utilizing a hydrothermal method followed by calcination. Replacing gallium with indium in the crystal structure of Ga₂O₃:Cr³⁺ redshifts the emission wavelength to 830 nm and induces persistent luminescence, which is attributed to lattice distortion caused by the substitution of gallium with indium, which modifies the crystal field around the Cr³⁺ ions. The as-prepared GIO nanoparticles show potential for future low-cost, deep-tissue bioimaging applications.

---

1. Introduction

Near-infrared (NIR) technology is extensively utilized in bio-imaging due to its advantages, including high sensitivity, high resolution, and the absence of harmful radiation.¹ Recent advancements in technology have led to significant interest in NIR luminescent materials in both academic and industrial fields.^2,3 In recent years, a diverse array of NIR luminescent materials have been developed, including quantum dots (QDs),^4,5 organic luminescent materials (OLMs),⁶ and aggregation-induced luminescent materials (AIEs).^7–9 While the luminescent characteristics of these materials can be efficiently adjusted through rigid molecular groups^10,11 and the quantum size effect,^12,13 many still encounter limitations, such as the requirement for in situ excitation, short delayed fluorescence durations, and unavoidable background noise.^14,15

Persistent luminescence nanoparticles (PLNPs) can emit long-lasting luminescence without in situ light excitation.¹⁶ In brief, these materials contain appropriate trap centers that, when exposed to light, enable electrons to absorb energy and become excited into the conduction band.¹⁷ Upon the removal of the light source, some of the electrons can be captured in the traps, thereby enabling the luminescent centers to gain energy via the recombination of electrons and holes.¹⁸ As a result, PLNPs have found applications in various fields, including bioimaging,^19,20 therapy,^21–23 photocatalysis,^24,25 anti-counterfeiting,^26–29 and data storage.^30,31

Recent studies have demonstrated the tuning of emission wavelengths through ion doping, leading to the optimization of the optical properties.^32–34 Among various doping options, Cr³⁺ has emerged as an exceptionally favorable choice for the design of red phosphors and has been extensively investigated.³⁵ Bessiere and his colleagues reported that ZnGa₂O₄ doped with Cr³⁺ can be excited by ultraviolet radiation, exhibiting a maximum emission peak at 696 nm.³⁶ Pan et al. synthesized β-Ga₂O₃:Cr³⁺ nanowires by a hydrothermal process followed by calcination, which also demonstrated an afterglow maximum emission peak at 696 nm.³⁷ Incorporation of different ions alters the optical properties of the material; for instance, LiGa₅O₈:Cr³⁺ displays an emission wavelength spectrum of afterglow emission wavelength from 650 to 800 nm, peaking at 716 nm.³⁸ Wang et al. reported In³⁺ doping of Ga₂O₃:Cr³⁺.³⁹ Micro-doping of In³⁺ in Ga₂O₃:Cr³⁺ enhances the persistent luminescence time, although the maximum afterglow emission peak remains at 690 nm.

In bioimaging, longer wavelengths can reduce scattering and provide deeper tissue imaging.⁴⁰ Recently, Ga_1.98−x (Al_0.68In_0.32)_xO₃:0.02Cr³⁺ (x = 0–0.8) exhibited a fluorescence emission range from 650 to 1000 nm due to the co-doping of Al³⁺ and In³⁺.⁴¹ Additionally, Ga_2−xIn_xO₃:Cr³⁺ (0 ≤ x ≤ 0.5), used as a NIR LED light source ranging from 713 to 820 nm, was also prepared using high-temperature solid-state synthesis.⁴² However, these materials function as phosphors and lack long afterglow capabilities. Furthermore, the high-temperature solid-state synthesis often results in larger particle sizes and poor water solubility, which limits their application in biomedical settings. The co-doping of Mg²⁺–Ge⁴⁺ in (Ga_1−xMg_x)(Ga_1−xGe_x)O₃:Cr³⁺ leads to a notable red shift in emission peaks, with a change from 726 to 830 nm.⁴³ However, the decay curves of these materials decrease from 221.2 to 55.9 μs, which is insufficient for long-term after-glow bioimaging. While most of the iron-doped Ga₂O₃ materials show a significant red shift in fluorescence, they couldn’t provide persistent luminescence.

In this work, Ga_1.99−xIn_xO₃:0.01Cr³⁺ (x = 0–1.99)(GIO:Cr) with an average lifetime of 17.24 s were prepared using a hydrothermal method combined with calcination. As the amount of In³⁺ substitution increased, the emission peak of GIO:Cr showed a significant redshift from 700 to 830 nm and persistent luminescence was induced, which is attributed to lattice distortion caused by the substitution of gallium with indium, which modifies the crystal field around the Cr³⁺ ions. The afterglow wavelength and intensity of GIO:Cr can be tuned by the ratio of Ga³⁺/In³⁺ and exhibits considerable potential for application in ratiometric luminescence and deep tissue bioimaging.⁴⁴

2. Experimental details

2.1. Reagents and instruments

All reagents were used as received without further purification. Cr (NO₃)₃·9H₂O (99.95%), Ga₂O₃ (99.99%), InCl₃ (99.99%), and ethylene glycol were purchased from Aladdin (Shanghai, China). Concentrated nitric acid and aqueous ammonia (15 wt%) were obtained from Shanghai Chemical Reagent. Ultrapure water (Hangzhou Wahaha Group Co. Ltd, Hangzhou, China) was used.

XRD patterns were recorded on a D/max-2500 diffractometer (Rigaku, Japan) using Cu Kα radiation (λ = 1.5418 A). TEM and high-resolution TEM images were obtained on a JEOL-100CX II microscope and a JEM-2100F field emission transmission electron microscope (JEOL, Japan), respectively. Photoluminescence spectra were recorded on an F-4500 spectrofluorometer (Hitachi, Japan).

2.2. Synthesis of Ga_1.99−xIn_xO₃:Cr³⁺PLNPs

Ga_1.99−xIn_xO₃:Cr³⁺ were synthesized using a hydrothermal followed by calcination. Typically, for Ga_1.64In_0.35O₃:0.01Cr, 5.0 mL of ethylene glycol, 3.28 mL of Ga³⁺ solution (0.2 mol L⁻¹), 0.7 of mL In³⁺ solution (0.2 mol L⁻¹), and 0.4 mL of Cr³⁺ solution (0.01 mol L⁻¹) were mixed and stirred for 30 minutes. The pH was adjusted to 9.0 with aqueous ammonia (15 wt%), and the mixing process was maintained for 1 h. The resulting mixture was poured into a 25 mL Teflon-lined autoclave, which was tightly sealed and heated to 170 °C for a duration of 16 h. Following naturally cooling to room temperature, the formed nanocrystals were washed with pure water and ethanol, separated by centrifugation, and subsequently dried. Finally, the nanocrystals were annealed at 700 °C for 3 h.

3. Results and discussion

3.1. Structure and phase

The XRD patterns of Ga_1.99−xIn_xO₃:Cr³⁺ with varying In³⁺ contents are presented in Fig. 1a. As observed in the XRD analysis, the as-synthesized sample Ga_1.99O₃:0.01Cr³⁺ without In³⁺ (x = 0) exhibits a pure monoclinic phase, which is indexed to β-Ga₂O₃ (JCPDS: 41-1103). The diffraction peaks of Ga_1.99O₃:0.01Cr³⁺ observed at 18.75°, 30.46°, 31.69°, 35.18°, 38.39° and 64.67° correspond to the (201), (401), (202), (111), (311) and (712) planes of β-Ga₂O₃, respectively. The amount of Cr³⁺ in Ga_1.99O₃:0.01Cr³⁺ was insufficient to influence the crystal structure of β-Ga₂O₃. In β-Ga₂O₃, there are two crystallographically distinct Ga³⁺ positions: one tetrahedrally coordinated by oxygen (coordination number 4), and the other octahedrally coordinated by oxygen (coordination number 6).⁴² In³⁺ preferentially occupies the octahedral sites rather than the tetrahedral sites, consistent with its larger ionic radius compared to Ga³⁺.⁴⁵ As shown in the XRD analysis, the diffraction peaks gradually shifted to lower angles upon introducing In³⁺ (x = 0.14–0.94) into the samples. This shift is attributed to the substitution of smaller Ga³⁺ (62 pm) with In³⁺ (92 pm) in Ga₂O₃, resulting in the expansion of the crystal lattice and the corresponding shift of the diffraction peaks. This expansion is attributed to substituting smaller Ga³⁺ with larger In³⁺, which prefers the octahedral sites. The crystal structure of PLNPs progressively transitioned from β-Ga₂O₃ to GaInO₃ with increasing In content in the PLNPs. When the In content exceeded 1.04 (x), peaks corresponding to In₂O₃ began to emerge, whereas the peaks of Ga₂O₃ disappeared. The crystal structure of PLNPs gradually transfers from GaInO to In₂O₃. Furthermore, as the concentration of In³⁺ increases, In³⁺ exhibits a stronger energy preference for the octahedral site where Ga is completely substituted in the PLNPs, and the XRD pattern of the PLNPs (x = 1.99) well matches the structure of In₂O₃ (JCPDS: 1-929). The crystal structures depicted in Fig. 1b are derived from X-ray powder diffraction analysis, with structural data associated with β-Ga₂O₃ (ICSD: 34243), GaInO₃ (ICSD: 30339), and In₂O₃ (ICSD: 426846). These structures represent the phase transition from β-Ga₂O₃ to In₂O₃ during In³⁺ doping and suggest that Ga³⁺ and In³⁺ ions are coordinated in similar octahedral environments within the β-Ga₂O₃ phase.

Fig. 1 (a) XRD patterns of Ga_1.99−xIn_xO₃:Cr³⁺ and (b) crystal structures of β-Ga₂O₃ (ICSD: 34243; PDF: 41-1103), β-GaInO₃ (ICSD: 30339; PDF: 21-334) and In₂O₃ (ICSD: 426846; PDF: 1-929).

3.2. Morphology of Ga_0.75In_1.24O₃:Cr³⁺

Fig. 2a shows the TEM image of the GIO:Cr nanoparticles. These PLNPs exhibit a particle size of approximately 60 nm. High-resolution transmission electron microscopy (HR-TEM) analysis (Fig. 2b) reveals that GIO:Cr structures exhibit two distinct types of clear lattice fringes at 0.563 nm and 0.283 nm, corresponding to the d-spacing of the spinel β-Ga₂O₃ (202) and rh-In₂O₃ (400) lattice planes, respectively. In summary, the structure of GIO:Cr consists of a mixed gallium indium-oxide incorporating both β-Ga₂O₃ and rh-In₂O₃, which aligns with the XRD results. The energy dispersive X-ray spectroscopy (EDS) of GIO:Cr (Fig. 2c–g) indicates that the elements (Ga, In, O, and Cr) are uniformly distributed in the sample, and no other elements were detected.

Fig. 2 (a) TEM, (b) HR-TEM, and (c)–(g) EDS mapping of the Ga_0.75In_1.24O₃:Cr³⁺.

3.3. Photoluminescence of GIO:Cr

As illustrated in Fig. 3a, the excitation spectrum of GIO:Cr, monitored at 800 nm, reveals a strong absorption peak at 300 nm, which is attributed to the combination of the Ga₂O₃ host excitation band and the O–Cr charge transfer band.^46,47 Additionally, other absorption peaks at 460 nm and 600 nm are attributed to the ⁴A₂ → ⁴T₁ and ⁴A₂ → ⁴T₂ electron transition.⁴⁸ Cr³⁺ serves as the luminescence center, contributing to the near-infrared emission.⁴⁹ With increasing concentration of In³⁺, the PL of GIO:Cr shows a significant redshift of 130 nm, with the main peak shifting from 700 nm to 830 nm. This shift is associated with the crystal field strength of Cr³⁺ in Ga₂O₃.⁴⁰ This phenomenon may be caused by the larger radius of In³⁺ compared to Ga³⁺, which is expected to alter the crystal field of GIO:Cr.⁵⁰ The crystal field of Cr³⁺ can be characterized by the crystal field D_q and the Racah parameter, B, calculated using the equation:⁵¹

10D_q = E(⁴T₂) = E(⁴T₂ → ⁴A₂) (1)

11D_q + 15/2B = E(⁴T₁ → ⁴A₂) (2)

Fig. 3 (a) Excitation spectra of GIO:Cr. (b) Emission spectra of GIO:Cr. (c) Persistent luminescence decay curves of GIO:Cr after UV irradiation for 10 min. (d) Thermoluminescence spectra of GIO:Cr (x = 1.24) recorded within a temperature range extending from room temperature to 700 K (monitoring from 350 nm to 900 nm).

The emission transitions of Cr³⁺ depend on the D_q/B. In a strong crystal field, Cr³⁺ exhibits a narrow, intense emission at 700 nm, along with a broadband emission associated with a weaker crystal field.^52,53 In this work, the main peak of GIO:Cr emission at 718 nm, generated by the ⁴T₂ → ⁴A₂ transition of Cr³⁺, was observed with excitation at 440 nm, attributed to the ⁴A₂ → ⁴T₁ transition of Cr³⁺.¹⁴ For Ga_1.99O₃:0.01Cr (x = 0), the D_q/B for Cr³⁺ was found to be 1.41. In the case of Ga_1.45In_0.54O₃:0.01Cr (x = 0.54), the D_q/B for Cr³⁺ decreased to 1.28. As the concentration of In³⁺ increased, the crystal structure of Ga₂O₃ changed, indicating a transition of the crystal field experienced by Cr³⁺ from a strong to a weak crystal field, which resulted in a redshift and broadband emission.⁴⁰

The afterglow decay curves and images of GIO:Cr (x = 0–1.24) were collected after 10 min of 254 nm UV irradiation (Fig. 3c and Fig. S2, ESI†). Although the average lifetime of GIO:Cr decreases with increasing concentration of In³⁺, GIO:Cr still has an obvious afterglow at an In³⁺ concentration of 1.24 (τ_av = 17.24 s). The lifetime of GIO:Cr can be accurately represented by eqn (3):³⁹

Briefly, t is the decay time of the afterglow, I₀ is the initial intensity of the PL, the A are constants and depend on the rapid luminescent intensity when t = 0, and τ₁, τ₂, and τ₃ are the time constants, indifferent to the afterglow decay lifetimes. In addition, GIO:Cr with different ratios of Ga³⁺/In³⁺ are shown in Fig. S1 (ESI†). The fitted decay curve results are shown in Table S1 (ESI†), and the decay time of afterglow was tuned by In³⁺.

Trapping levels play an important role in PLNPs.^54,55 An appropriate density of traps in persistent phosphors can effectively preserve the excitation energy and primarily determines the intensity and lifetime of persistent luminescence.^56–58Fig. 3d presents the thermoluminescence (TL) spectra of GIO:Cr (x = 1.24). The TL peak temperature, Tm, GIO:Cr (x = 1.24), was recorded as 383 K. The expression used to approximate the trap-level model is as per the following equation (eqn (4)):⁵⁹

E = T_m/500 (4)

T_m is the temperature corresponding to the maximum intensity of the emission wavelength. The results show that GIO:Cr exhibits deep electron traps (E = 0.766 eV) when the In³⁺ content increases to 1.24. Consequently, electrons are stored in deep traps, allowing GIO:Cr to retain an afterglow at 830 nm after the excitation source is removed.

As shown in Fig. 4a, different thicknesses of pork were placed over Ga₂O₃:Cr and Ga_0.75In_1.24O₃:0.01Cr³⁺. Fig. S3a and b (ESI†) demonstrate that the persistent luminescence intensity decreases with increasing pork tissue thickness, regardless of whether the emission wavelength is 696 nm or 830 nm. Fig. 4b and c show persistent luminescence images of Ga₂O₃:Cr (λ_em = 696 nm) and Ga_0.75In_1.24O₃:0.01Cr³⁺ (λ_em = 830 nm) captured at different time intervals. Specifically, for the emission peak at 696 nm, the afterglow signal sharply declines at 8 mm, and no detectable afterglow is observed beyond this thickness. In contrast, for the emission peak at 830 nm, a detectable afterglow signal remains even at a thickness of 1 cm. These results highlight the potential of GIO:Cr for deep tissue imaging, offering valuable non-invasive imaging for early diagnosis and disease monitoring.

Fig. 4 (a) Photos of Ga₂O₃:Cr³⁺ and Ga_0.75In_1.24O₃:0.01Cr³⁺ covering pork with different thicknesses (0 mm, 2 mm, 4 mm, 6 mm, 8 mm, 1.0 cm). (b) After irradiation under 254 nm UV light (6 W) for 10 minutes, with an exposure time of 10 s, the persistent luminescence images of Ga₂O₃:Cr³⁺ (λ_em = 696 nm) were recorded at different times for various pork thicknesses. (c) After irradiation under 254 nm UV light (6 W) for 10 minutes, with an exposure time of 10 s, the persistent luminescence images of Ga_0.75In_1.24O₃:0.01Cr³⁺ (λ_em = 830 nm) were recorded at different times for various pork thicknesses.

The persistent luminescence mechanism of GIO:Cr is depicted in Fig. 5. In GIO:Cr (x = 1.24), the trap levels are broadly distributed across a wide energy range, as evidenced by the extensive thermoluminescence spectra in Fig. 3d. Upon 254 nm UV excitation, electrons are promoted from the valence band to the conduction band, with some being captured by electron traps through non-radiative transitions, while others transition to deeper traps via interstitial crossing. After the UV excitation ceases, these trapped electrons are slowly released, and return to the excited state via interstitial crossing and subsequently relax to the ground state, emitting NIR light at 830 nm.

Fig. 5 Schematic illustration of the persistent NIR luminescence mechanism.

4. Conclusions

We have successfully synthesized Ga_1.99−xIn_xO₃:0.01Cr³⁺ (x = 0–1.99) PLNPs using a hydrothermal method combined with calcination. The fine-tuning of the Ga³⁺/In³⁺ ratio has been demonstrated to markedly alter the luminescence properties of the PLNPs, representing a breakthrough in the design of deep-red emissive materials. Notably, the optimized nanoparticles exhibit a maximum emission peak at 830 nm with an extended lifetime of 17.24 s. These deep-red nanoscale PLNPs show great potential for biomedical applications, particularly in deep-tissue imaging, where deeper penetration and longer persistence are crucial.

Author contributions

Qingqing Xie: data curation, writing – original draft preparation; AilijiangTuerdi: data curation, writing – original draft preparation; Xiangkai Qiao: data curation; YalinZheng: data curation; AikelaimuAihemaiti: data curation; Peng Yan: data curation; AbdukaderAbdukayum: methodology, conceptualization, supervision, funding acquisition, writing – reviewing and editing.

Data availability

The data supporting this article have been included as part of the ESI.†

Conflicts of interest

The authors declare no competing financial interest.

Acknowledgements

This work is supported by the Natural Science Foundation of Xinjiang Uygur Autonomous Region, China (2022D01E16), the National Natural Science Foundation of China (22364016), the Xinjiang Tianshan Talent Training Program, China (2024TSYC), and the Tianshan Innovation Team Plan of Xinjiang Uygur Autonomous Region, China (2023D14002).

References

1. L.-L. Chen, L. Zhao, Z.-G. Wang, S.-L. Liu and D.-W. Pang, Small, 2022, 18, 2104567.
2. Z. Hu, W. H. Chen, J. Tian and Z. Cheng, Trends Mol. Med., 2020, 26, 469–482.
3. W.-T. Huang, V. Rajendran, M.-H. Chan, M. Hsiao, H. Chang and R.-S. Liu, Adv. Opt. Mater., 2023, 11, 2202061.
4. C. Ding, Y. Huang, Z. Shen and X. Chen, Adv. Mater., 2021, 33, 2007768.
5. F. P. García de Arquer, D. V. Talapin, V. I. Klimov, Y. Arakawa, M. Bayer and E. H. Sargent, Science, 2021, 373, eaaz8541.
6. Q. Dang, Y. Jiang, J. Wang, J. Wang, Q. Zhang, M. Zhang, S. Luo, Y. Xie, K. Pu, Q. Li and Z. Li, Adv. Mater., 2020, 32, 2006752.
7. J. Lin, X. Zeng, Y. Xiao, L. Tang, J. Nong, Y. Liu, H. Zhou, B. Ding, F. Xu, H. Tong, Z. Deng and X. Hong, Chem. Sci., 2019, 10, 1219–1226.
8. W. Xu, D. Wang and B. Z. Tang, Angew. Chem., Int. Ed., 2021, 60, 7476–7487.
9. Z. Zhang, W. Wang, Y. Jiang, Y. X. Wang, Y. Wu, J. C. Lai, S. Niu, C. Xu, C. C. Shih, C. Wang, H. Yan, L. Galuska, N. Prine, H. C. Wu, D. Zhong, G. Chen, N. Matsuhisa, Y. Zheng, Z. Yu, Y. Wang, R. Dauskardt, X. Gu, J. B. Tok and Z. Bao, Nature, 2022, 603, 624–630.
10. B. Li, M. Liu, L. Sang, Z. Li, X. Wan and Y. Zhang, Adv. Opt. Mater., 2023, 11, 2202610.
11. G. Feng and B. Liu, Acc. Chem. Res., 2018, 51, 1404–1414.
12. M. J. Afshari, C. Li, J. Zeng, J. Cui, S. Wu and M. Gao, ACS Nano, 2022, 16, 16824–16832.
13. T. Yuan, T. Meng, Y. Shi, X. Song, W. Xie, Y. Li, X. Li, Y. Zhang and L. Fan, J. Mater. Chem. C, 2022, 10, 2333–2348.
14. A. Abdukayum, J. T. Chen, Q. Zhao and X. P. Yan, J. Am. Chem. Soc., 2013, 135, 14125–14133.
15. S. K. Sun, H. F. Wang and X. P. Yan, Acc. Chem. Res., 2018, 51, 1131–1143.
16. T. Matsuzawa, Y. Aoki, N. Takeuchi and Y. Murayama, J. Electrochem. Soc., 1996, 143, 2670–2673.
17. F. Clabau, X. Rocquefelte, S. Jobic, P. Deniard, M.-H. Whangbo, A. Garcia and T. Le Mercier, Chem. Mater., 2005, 17, 3904–3912.
18. Q. le Masne de Chermont, C. Chaneac, J. Seguin, F. Pelle, S. Maitrejean, J. P. Jolivet, D. Gourier, M. Bessodes and D. Scherman, Proc. Natl. Acad. Sci. U. S. A., 2007, 104, 9266–9271.
19. X. Fu, L.-X. Yan, X. Zhao, L.-J. Chen and X.-P. Yan, Chem. Eng. J., 2024, 480, 147740.
20. X. Fu, X. Zhao, L.-J. Chen, P. Ma, T. Liu and X.-P. Yan, Biomater. Sci., 2023, 11, 5186–5194.
21. Z. Zhou, Y. Li and M. Peng, Chem. Eng. J., 2020, 399, 125688.
22. N. Liu, X. Chen, X. Sun, X. Sun and J. Shi, J. Nanobiotechnol., 2021, 19, 113.
23. X. Liu, R. Xi, Y. Hu, Y. Wang and A. Abdukayum, Dalton Trans., 2024, 53, 6601–6608.
24. A. Tuerdi and A. Abdukayum, RSC Adv., 2019, 9, 17653–17657.
25. F. He, A. Abulimiti, B. Li, Y. Wu, Y. Chen, M. Zhang and A. Abdukayum, ACS Appl. Nano Mater., 2023, 6, 12871–12881.
26. X. Zhang, Z. Wang, C. Xu, D. Gao, Q. Pang, J. Xu and X. Wang, Laser Photonics Rev., 2025, 19, 2401376.
27. Q. Kuang, X. Hou, C. Du, X. Wang and D. Gao, Phys. Chem. Chem. Phys., 2023, 25, 17759–17768.
28. D. Gao, C. Du, Y. Wang, W. Xu, W. Gao, Q. Pang and Y. Wang, J. Mater. Chem. C, 2024, 12, 19487–19497.
29. X. Qiao, L. Kasim, A. Tuerdi, G. Hu and A. Abdukayum, ACS Appl. Nano Mater., 2023, 6, 20831–20840.
30. D. Gao, Z. Wang, Q. Pang, Q. Kuang, F. Gao, X. Zhang, S. Yun and X. Wang, Adv. Opt. Mater., 2023, 11, 2300303.
31. D. Gao, Z. Wang, X. Zhang, Q. Pang and X. Wang, ACS Appl. Mater. Interfaces, 2025, 17, 3587–3596.
32. F. Kang, M. Peng, X. Yang, G. Dong, G. Nie, W. Liang, S. Xu and J. Qiu, J. Mater. Chem. C, 2014, 2, 6068–6076.
33. F. Kang, H. Zhang, L. Wondraczek, X. Yang, Y. Zhang, D. Y. Lei and M. Peng, Chem. Mater., 2016, 28, 2692–2703.
34. F. Kang, G. Sun, P. Boutinaud, F. Gao, Z. Wang, J. Lu, Y. Y. Li and S. Xiao, J. Mater. Chem. C, 2019, 7, 9865–9877.
35. M. N. da Silva, J. M. de Carvalho, M. C. de Abreu Fantini, L. A. Chiavacci and C. Bourgaux, ACS Appl. Nano Mater., 2019, 2, 6918–6927.
36. A. Bessiere, S. Jacquart, K. Priolkar, A. Lecointre, B. Viana and D. Gourier, Opt. Express, 2011, 19, 10131–10137.
37. Y. Y. Lu, F. Liu, Z. J. Gu and Z. W. Pan, J. Lumin., 2011, 131, 2784–2787.
38. F. Liu, W. Yan, Y. J. Chuang, Z. Zhen, J. Xie and Z. Pan, Sci. Rep., 2013, 3, 1554.
39. L. Li, K. Xu, Y. Wang, Z. Hu and H. Zhao, Opt. Mater. Express, 2016, 6, 1122–1130.
40. T. Jia and G. Chen, Coord. Chem. Rev., 2022, 471, 214724.
41. C.-Y. Chang, N. Majewska, K.-C. Chen, W.-T. Huang, T. Leśniewski, G. Leniec, S. M. Kaczmarek, W. K. Pang, V. K. Peterson, D.-H. Cherng, K.-M. Lu, S. Mahlik and R.-S. Liu, Chem. Mater., 2022, 34, 10190–10199.
42. J. Zhong, Y. Zhuo, F. Du, H. Zhang, W. Zhao and J. Brgoch, ACS Appl. Mater. Interfaces, 2021, 13, 31835–31842.
43. J. Zhong, L. Zeng, W. Zhao and J. Brgoch, ACS Appl. Mater. Interfaces, 2022, 14, 51157–51164.
44. L. M. Pan, X. Zhao, X. Wei, L. J. Chen, C. Wang and X. P. Yan, Anal. Chem., 2022, 94, 6387–6393.
45. W. T. Chen, H. S. Sheu, R. S. Liu and J. P. Attfield, J. Am. Chem. Soc., 2012, 134, 8022–8025.
46. F. Shi and H. Qiao, CrystEngComm, 2020, 22, 7794–7799.
47. H. Kwak, J.-S. Kim, D. Han, J. S. Kim, J. Park, G. Kwon, S.-M. Bak, U. Heo, C. Park, H.-W. Lee, K.-W. Nam, D.-H. Seo and Y. S. Jung, Nat. Commun., 2023, 14, 2459.
48. J. Zhang, W. Mu, K. Zhang, J. Sun, J. Zhang, N. Lin, X. Zhao, Z. Jia and X. Tao, CrystEngComm, 2020, 22, 7654–7659.
49. B. Viana, S. K. Sharma, D. Gourier, T. Maldiney, E. Teston, D. Scherman and C. Richard, J. Lumin., 2016, 170, 879–887.
50. M. G. Brik, S. J. Camardello, A. M. Srivastava, N. M. Avram and A. Suchocki, ECS J. Solid State Sci. Technol., 2016, 5, R3067.
51. B. Struve and G. Huber, Appl. Phys. B, 1985, 36, 195–201.
52. Y. Jin, Y. Hu, L. Yuan, L. Chen, H. Wu, G. Ju, H. Duan and Z. Mu, J. Mater. Chem. C, 2016, 4, 6614–6625.
53. B. Bai, P. Dang, D. Huang, H. Lian and J. Lin, Inorg. Chem., 2020, 59, 13481–13488.
54. M. Allix, S. Chenu, E. Véron, T. Poumeyrol, E. A. Kouadri-Boudjelthia, S. Alahraché, F. Porcher, D. Massiot and F. Fayon, Chem. Mater., 2013, 25, 1600–1606.
55. Y. Zhuang, L. Wang, Y. Lv, T.-L. Zhou and R.-J. Xie, Adv. Funct. Mater., 2018, 28, 1705769.
56. X. Chen, Y. Li, K. Huang, L. Huang, X. Tian, H. Dong, R. Kang, Y. Hu, J. Nie, J. Qiu and G. Han, Adv. Mater., 2021, 33, 2008722.
57. J. Du, A. Feng and D. Poelman, Laser Photonics Rev., 2020, 14, 2000060.
58. L. Liang, J. Chen, K. Shao, X. Qin, Z. Pan and X. Liu, Nat. Mater., 2023, 22, 289–304.
59. K. Van den Eeckhout, P. F. Smet and D. Poelman, Materials, 2010, 3, 2536–2566.

---

Footnotes

† Electronic supplementary information (ESI) available. See DOI: https://doi.org/10.1039/d4tc05353b

‡ Qingqing Xie and Ailijiang Tuerdi contributed equally.

---