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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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

Received: 2019-12-11 Accepted: 2020-04-18

ZTFLH:

O469

Corresponding Authors: LIU Chun-guang E-mail: liucg@.nenu.edu.cn

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http://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2021)01-0080-08 OR http://www.gpxygpfx.com/EN/Y2021/V41/I01/80