Cr3+单掺杂及Eu3+/Cr3+共掺杂GdAlO3近红外长余辉发光纳米粒子的制备、微结构及光学特性

doi:10.3964/j.issn.1000-0593(2021)01-0080-08

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摘要：同时可作为磁共振成像造影剂与近红外余辉光学成像光学探针双功能的纳米粒子，在生物医学领域具有重要的应用价值。采用自蔓延燃烧法制备了不同掺杂浓度的GdAlO₃∶x%Cr³⁺及GdAlO₃∶1%Cr³⁺, y%Eu³⁺近红外长余辉发光纳米粒子。并采用X射线衍射、扫描电子显微镜、激发和发射光谱及发光动力学分析等技术手段，较系统地研究了其微结构及光学特性。实验结果表明，Cr³⁺取代了GdAlO₃中的Al³⁺的格位，单掺样品的平均粒子尺寸约为202 nm。GdAlO₃∶x%Cr³⁺样品的激发谱显示，激发峰来源于Cr³⁺和Gd³⁺的跃迁；在583 nm的激发下，在650～750 nm近红外范围内，出现四个近红外光发射峰。其中，725 nm处的发射峰归属为禁戒跃迁²E到⁴A₂的零声子线, 700和750 nm处的发射峰则为声子边带的发射。在0.2%～2.0%的掺杂浓度范围内，随着Cr³⁺掺杂浓度的增加，这些发射峰的强度先增强后减弱，最优浓度为1%。而位于735 nm处的发射峰强度随Cr³⁺浓度增大而增大，其归属于Cr³⁺-Cr³⁺对的发光。同时，单掺样品可观察到位于725 nm的长余辉发光，其中GdAlO₃∶1%Cr³⁺纳米粒子的余辉时间最长，并超过30 s。在上述Cr³⁺最优浓度（1%）基础上，通过Eu³⁺取代GdAlO₃基质中Gd³⁺的格位，实现了Eu³⁺/Cr³⁺共掺杂。实验发现，在266 nm激发下，在红光区域范围内可观察到以位于614 nm处的发射为主的一系列发射峰。尤其，由于存在Eu³⁺到Cr³⁺的能量传递，在近红外区出现了位于725 nm处Cr³⁺的近红外发射峰。当Eu³⁺浓度为13%时，与Cr³⁺单掺杂样品相比，其样品的平均粒子尺寸虽然减小到167 nm，但在275 nm紫外光照射5 min停止后，发现共掺样品在位于725 nm处Cr³⁺的余辉发光强度明显增强。通过比较分析单掺和共掺样品的吸收和发射光谱及发光动力学的结果，验证了由于Eu³⁺到Cr³⁺的持续能量传递可引起较显著地近红外余辉发光增强的结论。同时，该研究为设计新型的近红外长余辉发光纳米材料提供了新的思路。

关键词：光致发光；Cr³⁺；Eu³⁺；能量传递；余辉；荧光粉

Abstract：It is important to prepare new nanoparticles that can be simultaneously used as contrast agents for magnetic resonance imaging and optical probes for near-infrared afterglow optical imaging in the biomedical field. In this paper, single-phase GdAlO₃∶x%Cr³⁺ and GdAlO₃∶1%Cr³⁺,y%Eu³⁺ near-infrared persistent luminescent nanoparticles with different doping concentrations wereprepared by a self-propagating combustion method. Their microstructure and optical properties were studied by means of X-ray diffraction, scanning electron microscopy, excitation and emission spectra and luminescent kinetics analysis. It is found that, for Cr³⁺ single doped samples, Cr³⁺ ions replace the Al³⁺ sites and the average particle size is ~202 nm. From excitation spectra of GdAlO₃∶x%Cr³⁺ samples, it can be found that, the excitation peaks are attributed to transitions of Cr³⁺ and Gd³⁺ ions. Meanwhile, four emission peaks appear in the near-infrared range of 650～750 nm upon 583 nm excitation. Among them, the emission peak at 725 nm belongs to the zero phonon line (PZL) and those peaks at 700 and 750 nm can be attributed to the emissions from phonon sidebands (PS) of the ²E→⁴A₂ forbidden transitions, respectively. In the doping concentration range of 0.2%～2.0%, the intensities of these emission peaks show an initial increase and a subsequent decrease with the increase of Cr³⁺ doping concentration. When the doping concentration reaches 1%, the strongest intensity can be obtained. However, the intensity of the emission peak at 735 nm increases with the increase of Cr³⁺ concentration, which is attributed to the emission from Cr³⁺-Cr³⁺ pairs. It is found that long afterglow luminescence at 725 nm can be observed for Cr³⁺ single-doped nanoparticles. Among them, the afterglow time of GdAlO₃∶1%Cr³⁺ nanoparticles is the longest and exceeds 30 s. On the basis of the above optimal Cr³⁺ concentration (1%), single-phase Eu³⁺/Cr³⁺ co-doped GdAlO₃ nanoparticles were prepared by the replacement of Gd³⁺by Eu³⁺. It is found that several emission peaks dominated by the emission at 614 nm can be observed in the red region under 266 nm excitation. In particular, the near-infrared emission peak of Cr³⁺ at 725 nm appears under 266 nm excitation due to the presence of the energy transfer from Eu³⁺ to Cr³⁺. It is found that, compared to the Cr³⁺ single-doped sample, GdAlO₃∶1%Cr³⁺, 13%Eu³⁺ sample exhibits the stronger afterglow emission intensity of Cr³⁺ at 725 nm after stopping 275 nm UV light irradiation for 5 minutes, although its average particle size is reduced to ~167 nm. By the comparative analyses of the results of absorption and emission spectra and luminescence kinetics of single-doped and co-doped samples, it is proved that the existence of a persistent energy transfer from Eu³⁺ to Cr³⁺leads to the enhanced near-infrared afterglow intensity. Meanwhile, this study provides new strategies for designing new near-infrared long persistent luminescent nanomaterials.

Key words：Photoluminescence; Cr³⁺ ions; Eu³⁺ ions; Energy transfer; Afterglow; Phosphor

收稿日期: 2019-12-11 修订日期: 2020-04-18

中图分类号:

O469

基金资助: 国家自然科学基金面上项目（11874103，12074062）资助

通讯作者: 刘春光 E-mail: liucg@.nenu.edu.cn

作者简介: 战盈霏，女，1994年生，东北师范大学物理学院硕士研究生 e-mail: 1340083558@qq.com

引用本文:

战盈霏，刘春光，王明炜，杨健，祝汉成，严端廷，徐长山，刘玉学. Cr³⁺单掺杂及Eu³⁺/Cr³⁺共掺杂GdAlO₃近红外长余辉发光纳米粒子的制备、微结构及光学特性[J]. 光谱学与光谱分析, 2021, 41(01): 80-87.
ZHAN Ying-fei, LIU Chun-guang, WANG Ming-wei, YANG Jian, ZHU Han-cheng, YAN Duan-ting, XU Chang-shan, LIU Yu-xue. Preparation, Microstructure and Optical Properties of Cr³⁺ Single-Doped and Eu³⁺/Cr³⁺ Co-Doped GdAlO₃ Near Infrared Long Persistent Luminescent Nanoparticles. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2021, 41(01): 80-87.

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