一、成果简介

余辉是一种古老而又新奇的物理现象，指的是材料在激发光停止后仍然能够持续发光的能力。中国古代的“夜明珠”能够在黑暗中发出耀眼的光芒，即利用了余辉现象。余辉材料在照明、装饰、信息存储、生物成像等领域具有广泛的应用。传统的余辉材料主要依赖于于硫化物、铝酸盐、氧硫化物、氮化物、锗酸盐、硅酸盐，近些年金属卤化物也表现出优异的余辉性能。

然而，目前余辉的物理机制主要是通过掺杂引入外部稀土等离子，产生缺陷态用于捕获光子，并且缓慢释放形成余辉。对于缺陷和发光中心的控制非常复杂，此外昂贵的稀土离子也增加了成本。由于掺杂离子的局限性，红色余辉发光容易实现，而蓝色则较为少见。

为解决上述问题，本工作提出了新型的锑酸盐余辉材料CaSb₂O₆，可以不经过任何外部掺杂，实现本征蓝光余辉。理论和实验证实，本征的氧空位可能是缺陷中心，而发光中心可能源于少量的Sb³⁺离子。该材料的余辉时间达到8000 s, 并且可以抵抗严酷的高温、酸碱、紫外辐照等环境，展现出了良好的稳定性。本工作进一步展示了粉末、陶瓷、3D成型、防伪等初步应用。

Figure 1. a) Illustration of the CaSb₂O₆crystal structure. b) XRD patterns of CaSb₂O₆ powder synthesized at different temperatures. c) SEM images of CaSb₂O₆powder. d) Elemental mapping of the corresponding CaSb₂O₆powder measured by EDX. e) HAADF results of CaSb₂O₆powder.

Figure 2. a) Absorption spectrum of CaSb₂O₆obtained from diffuse reflectance measurement. The inset is the Tauc plot. b) XPS curve of Sb 3p_3/2 orbital from CaSb₂O₆, Sb₂O₃, and Sb₂O₅, showing the existence of Sb³⁺ in CaSb₂O₆. c) Photoluminescence spectrum of CaSb₂O₆. The inset is the optical microscope image of CaSb₂O₆powder under white light and UV light. d) PL life time of CaSb₂O₆monitored at 440 nm. e) Emission spectra of CaSb₂O₆excited at different wavelengths. f) Photoluminescence spectra measured at different temperatures (RT to 493 K).

Figure 3. a) The intensity of LPL integrated from 320-1100 nm measured on CaSb₂O₆ sample after being charged with a LED at 315 nm. b) The normalized LPL spectrum of CaSb₂O₆, showing one emission center same as the PL spectrum, and the other emission center around 480 nm. c) The upper panel: TL spectrum measured promptly after ceasing the UV irradiation, which can be fitted by shallow trap center and deep trap center. The lower panel: The TL spectrum measured after ceasing the UV irradiation for 5 minutes delay, which can only be fitted by the deep trap center. d-f) The trap depth and intensity of shallow trap and deep trap derived from TL spectra measured from CaSb₂O₆ after being charged at different conditions: d) for different charge time; e) at different irradiation power; f) with different irradiation wavelength. g-h) The spectra of CaSb₂O₆ during charge and after charge, with the LED wavelength of g) 275 nm and h) 315 nm. i) The integrated luminescence intensity of CaSb₂O₆ under and after charged by 315 nm and 275 nm irradiation, respectively.

Figure 4. a) The formation energies of intrinsic point defects at Sb rich (left panel) and Sb-poor conditions (right panel) as a function of Fermi level in CaSb₂O₆. b) Transition energy levels of intrinsic defects for CaSb₂O₆. c) The trap depth of CaSb₂O₆ samples synthesized under Sb poor, stoichiometry, and Sb rich conditions derived from TL. d) The trap intensity of CaSb₂O₆ samples synthesized under Sb poor, stoichiometry, and Sb rich conditions derived from TL. e) LPL decay of CaSb₂O₆sample measured at low temperature of 80 K, showing the tunneling effect. f) Configuration coordinate diagram for the LPL mechanisms of CaSb₂O₆.

三、论文信息

Nano Letters

Stable long-persistent luminescence from self-activated CaSb₂O₆ induced by intrinsic defects

Yanbing Han‡, Qingqing Mo‡, Zhuangzhuang Ma, Jinglu Zhang, Dongwen Yang*, Ying Liu, Xu Chen, Han Gao*, Xinjian Li, Chongxin Shan, and Zhifeng Shi*

First published: 5 November 2024

https://pubs.acs.org/doi/10.1021/acs.nanolett.4c04471

四、作者介绍

韩炎兵，郑州大学物理学院副教授，2019年博士毕业于复旦大学，并加入郑州大学物理学院史志锋团队。主要从事氧化物和硫化物等新型半导体材料的制备和物理光电特性研究，目前主持国 家青年基金等项目。以第 一作者或通讯作者在Chemical Reviews, Applied Physics Reviews, Advanced Functional Materials等期刊发表论文20余篇，出版专著1部，授权发明专利3项。