Calcium Doped Self-activated Zinc Germanate Long Afterglow Materials: Multicolor Afterglow and Application in Dynamic Anti-counterfeiting

doi:10.15541/jim20220733

Abstract

Abstract:

Long afterglow materials have wide application in the fields of safety indication, anti-counterfeiting and biological imaging, whereas their defect regulation and afterglow mechanism remain unclear. Self-activated long afterglow materials attracted attention due to their simple composition and structure, which is convenient for revealing the mechanism of long afterglow. A series of calcium doped self-activated zinc germanate long afterglow materials Zn_2-_xCa_xGeO₄ (x=0, 0.1, 0.2, 0.3, 0.4, 0.5) were synthesized by high temperature solid reaction. The results showed that yellow luminescence peak of calcium doped zinc germanate sample was observed when excited by 376 nm UV light. Upon 267 nm excitation, the fluorescence intensity of Zn_1.5Ca_0.5GeO₄ increased by 6.2 times. According to the afterglow spectra and their decay curves, the initial afterglow intensity is enhanced by 25.1 times. In addition, Zn_1.5Ca_0.5GeO₄ maintains an afterglow intensity nearly 5 times that of zinc germanate during the first 300 s afterglow duration. Further characterization of TL curves show that the depth of the main trap is about 0.7 eV. After adding proper concentration of Ca²⁺, the TL peaks become significantly stronger, indicating that the trap density increases significantly after calcium doping. Finally, taking advantage of the difference of the afterglow decay rate of different emission wavelengths, the dynamic change of the "flower" color is realized, which indicates that the obtained materials have the potential application in the field of dynamic anti-counterfeiting.

Key words: self-activating long afterglow material, Zn_2-_xCa_xGeO₄, multi-color afterglow, trap distribution, dynamic anti-counterfeiting

CLC Number:

O433

ZENG Qiqi, WU Yanzheng, CHENG Huangyu, SHAO kang, HU Tianyu, PAN Zaifa. Calcium Doped Self-activated Zinc Germanate Long Afterglow Materials: Multicolor Afterglow and Application in Dynamic Anti-counterfeiting[J]. Journal of Inorganic Materials, 2023, 38(8): 901-909.

Figures/Tables 9

Fig. 1 Structure characterization of ZCGO series samples (a) XRD patterns of ZCGO series samples; (b) Structure diagram of Zn2GeO4

Fig. 2 Fitting plot of mass percentage change of Ca element(x) in ZCGO samples

Fig. 3 Diffuse reflection spectra and band gap widths of ZCGO series samples (a) UV-Vis diffuse reflectance spectra of ZCGO samples; (b) (F(R)×E)1/2-E diagram of ZCGO series sample; Colorful figures are available on website (Band gap energy is estimated by intercept of the tangential)

Fig. 4 Excitation spectra under different monitoring wavelengths and photos in different light sources of ZCGO series samples (a) 450 nm; (b) 526 nm; (c) 600 nm; (d) Photographs of ZCGO samples excited by daylight, 254 and 365 nm; Colorful figures are available on website

Fig. 5 Emission spectra of ZCGO series samples at different excitation wavelengths (a, b) Steady-state emission spectra of ZCGO samples excited at (a) 267 nm and (b) 376 nm; (c, d) Time-resolved emission spectra of ZCGO samples excited at (c) 267 nm, (d) 376 nm; Colorful figures are available on website

Fig. 6 Afterglow decay curves of ZCGO series samples and ZCGO-5 samples under different monitoring wavelengths (a, b) Afterglow decay curves of ZCGO samples excited at 267 nm and monitored at (a) 450 nm and (b) 526 nm; (c) Afterglow decay curves of ZCGO samples excited at 376 nm and monitored at 600 nm; (d) Afterglow decay curves of ZCGO-5 samples monitored at 450 nm, 526 nm and 600 nm; Colorful figures are available on website

Table 1 Parameters for double-exponentially fitting afterglow decay of ZCGO-5 and ZGO samples

Sample	τ₁/s	A₁	τ₂/s	A₂	τ_avg/s
ZCGO-1	6.82	0.61	81.44	0.58	75.88
ZCGO-2	6.52	0.91	90.57	0.97	85.26
ZCGO-3	7.88	0.67	87.94	0.85	82.68
ZCGO-4	6.78	0.85	88.58	0.98	83.47
ZCGO-5	9.17	0.65	88.49	0.83	82.53
ZGO	4.92	0.65	66.13	0.40	63.47

Fig. 7 TL curves of ZCGO series samples under different monitoring wavelengths and trap depth histogram of samples (a, b) TL curves of ZCGO series samples monitored at (a) 526 and (b) 600 nm; (c) TL curves of ZCGO-1 and ZGO samples monitored at 766 nm; (d) Trap depths corresponding to TL peaks of ZCGO series samples; Colorful figures are available on website

Fig. 8 Photos of flowers stimulated with 254 and 365 nm UV light, and the afterglow after the UV light was turned off

References 25

[1]	XU Z Y. Luminescence mechanism and structure characteristics of long afterglow phosphors. Modern Chemical Research, 2017, 8: 54.
[2]	ZHOU Z H, LI Y Y, PENG M Y. Near-infrared persistent phosphors: synthesis, design, and applications. Chemical Engineering Journal, 2020, 399: 125688.
[3]	HUANG K, LE N, WANG J S, et al. Designing next generation of persistent luminescence: recent advances in uniform persistent luminescence nanoparticles. Advance Materials, 2022, 34(14): 2107962.
[4]	XU J, TANABE S. Persistent luminescence instead of phosphorescence: history, mechanism, and perspective. Journal of Luminescence, 2019, 205: 581. DOI URL
[5]	LIN Y H, ZHANG Z T, TANG Z L, et al. The characterization and mechanism of long afterglow in alkaline earth aluminates phosphors co-doped by Eu₂O₃ and Dy₂O₃. Materials Chemistry and Physics, 2001, 70: 156. DOI URL
[6]	SRIVASTAVA B B, GUPTA S K, LI Y, et al. Bright persistent green emitting water-dispersible Zn₂GeO₄:Mn nanorods. Dalton Transactions, 2020, 49(22): 7328. DOI URL
[7]	SUZUKI V Y, DE PAULA N H, GONCALVES R, et al. Exploring effects of microwave-assisted thermal annealing on optical properties of Zn₂GeO₄ nanostructured films. Materials Science and Engineering: B, 2019, 246: 7. DOI URL
[8]	BAI Q, WANNG Z J, LI P L, et al. Zn_2-_aGeO₄:aRE and Zn₂Ge_1-_aO₄:aRE (RE=Ce³⁺, Eu³⁺, Tb³⁺, Dy³⁺): 4f-4f and 5d-4f transition luminescence of rare earth ions under different substitution. RSC Advances, 2016, 6(104): 102183.
[9]	CHI F F, WEI X T, JIANG B, et al. Luminescence properties and the thermal quenching mechanism of Mn²⁺ doped Zn₂GeO₄ long persistent phosphors. Dalton Transactins, 2018, 47(4): 1303.
[10]	LI H, WANG Y H, CHEN S H, et al. Enhanced persistent luminescence of Zn₂GeO₄ host by Ti⁴⁺ doping. Journal of Materials Science: Materials in Electronics, 2017, 28(19): 14827. DOI URL
[11]	SHANG M M, LI G G, YANG D M, et al. (Zn, Mg)₂GeO₄:Mn²⁺ submicrorods as promising green phosphors for field emission displays: hydrothermal synthesis and luminescence properties. Dalton Transactions, 2011, 40(37): 9379. DOI URL
[12]	ANOOP G, KRISHNA M K, JAYARAJ M K, et al. The effect of Mg incorporation on structural and optical properties of Zn₂GeO₄ :Mn phosphor. Journal of the Electrochemical Society, 2008, 155(1): J7. DOI URL
[13]	HE H L, ZHANG Y H, PAN Q W, et al. Controllable synthesis of Zn₂GeO₄:Eu nanocrystals with multi-color emission for white light-emitting diodes. Journal of Materials Chemistry C, 2015, 3(21): 5419. DOI URL
[14]	ZHANG S A, HU Y H, CHEN R, et al. Photoluminescence and persistent luminescence in Bi³⁺-doped Zn₂GeO₄ phosphors. Optical Materials, 2014, 36(11): 1830. DOI URL
[15]	PENG X L, TANG Z T, LUO Y H, et al. Visual color modulation and luminescence mechanism studies on Mn/Eu co-doped Zn-Mg- Ge-O long afterglow system. Ceramics International, 2020, 46(9): 14005. DOI URL
[16]	SHI L X, ZHENG W W, MIAO H Y, et al. Ratiometric persistent luminescence aptasensors for carcinoembryonic antigen detection. Microchimica Acta, 2020, 187(11): 615. DOI
[17]	GAO D L, MA K W, WANG P, et al. Tuning multicolour emission of Zn₂GeO₄:Mn phosphors by Li⁺ doping for information encryption and anti-counterfeiting applications. Dalton Transactions, 2022, 51(2): 553. DOI URL
[18]	GAO D L, KUANG Q Q, GAO F, et al. Achieving opto-responsive multimode luminescence in Zn₁₊_xGa_2-2_xGe_xO₄:Mn persistent phosphors for advanced anti-counterfeiting and information encryption. Materials Today Physics, 2022, 27: 100765.
[19]	LIU Z S, JING X P, WANG L X. Luminescence of native defects in Zn₂GeO₄. Journal of The Electrochemical Society, 2007, 154(6): 500.
[20]	BANDPAY M G, AMERI F, ANSARI K, et al. Mathematical and empirical evaluation of accuracy of the Kubelka-Munk model for color match prediction of opaque and translucent surface coatings. Journal of Coatings Technology and Research, 2018, 15(5): 1117. DOI
[21]	LÓPEZ R, GÓMEZ R. Band-gap energy estimation from diffuse reflectance measurements on Sol-Gel and commercial TiO₂: a comparative study. Journal of Sol-Gel Science and Technology, 2012, 61(1): 1. DOI URL
[22]	MALDINEY T, LECOINTRE A, VIANA B, et al. Controlling electron trap depth to enhance optical properties of persistent luminescence nanoparticles for in vivo imaging. Journal of the American Chemical Society, 2011, 133(30): 11810. DOI URL
[23]	WANG K, YAN L P, SHAO K, et al. Near-infrared afterglow enhancement and trap distribution analysis of silicon-chromium co-doped persistent luminescence materials Zn₁₊_xGa_2-2_xSi_xO₄:Cr³⁺. Journal of Inorganic Materials, 2019, 39(9): 983.
[24]	WANG C L, JIN Y H, LÜ Y, et al. Trap distribution tailoring guided design of super-long-persistent phosphor Ba₂SiO₄:Eu²⁺, Ho³⁺ and photostimulable luminescence for optical information storage. Journal of Materials Chemistry C, 2018, 6(22): 6058. DOI URL
[25]	MARTINČEK I, TUREK I, TARJÁNYI N. Effect of boundary on refractive index of PDMS. Optical Materials Express, 2014, 4(10): 1997. DOI URL