Spinel-phase Zn2Ga2.98−xGe0.75O8:Cr0.020,Prx (ZGGO:Cr3+,Pr3+) near infrared (NIR) persistent luminescence nanoparticles (PLNPs) with different amounts of Pr3+ dopant were prepared by a hydrothermal method in combination with a subsequent annealing in a vacuum. For these nanoparticles, the averaged particle size decreases from 64 to 37 nm with increasing Pr3+ doping concentration from 0 to 0.025 and Cr3+ and Pr3+ ions are uniformly doped into the interior and surface of a single nanoparticle. It can be found that Pr3+ doping leads to the appearance of more anti-site pairs () around distorted octahedral Cr3+ ions and enhanced NIR emissions around 697 nm, which originate from the 2E(2G) → 4A2(4F) and 4T2(4F) → 4A2(4F) transitions of the interior and surface Cr3+ ions in the nanoparticles. In particular, for the interior Cr3+ ions in the Pr3+ doped nanoparticles, the enhanced NIR luminescence can be attributed to the suppressed energy transfer of the excited electrons from the 4T2(4F) level to the trap level related to anti-site pairs () around the distorted octahedral Cr3+ ions. Our results suggest that Pr3+ doped ZGGO:Cr3+ PLNPs have potential applications for bio-imaging.
Zheng Gong,Jian Yang,Hancheng Zhu,Duanting Yan,Chunguang Liu,Changshan Xu,Yuxue Liu
Gd 3+ and Cr 3+ codoped zinc gallogermanate (ZGGO:Cr 3+ , Gd 3+ ) nanoparticles were prepared by a hydrothermal method in combination with a subsequent vacuum annealing. It is found that Gd 3+ doping not only endows ZGGO:Cr 3+ nanoparticles with magnetic property, but also results in the decreased nanoparticle size and the enhanced near infrared (NIR) afterglow intensity. Strikingly, amino group functionalized SiO 2 layer coating enabling Gd 3+ doped ZGGO:Cr 3+ nanoparticles well dispersed in water enhances persistent luminescence which is because of the weakened quenching effect of OH − groups in water. Validation of high-quality bioimaging was demonstrated using the surface functionalized Gd 3+ doped ZGGO:Cr 3+ nanoparticles dispersed in human serum albumin (HSA). In particular, it is found that the longitudinal relaxivity (7.33 s −1 (mM) −1 ) of Gd 3+ doped ZGGO:Cr 3+ nanoparticles is higher than that of commercial magnetic resonance imaging (MRI) contrast agent (Gd-DTPA) and it leads to the high-quality in vitro T 1 -weigthed images.
Zheng Gong,Yufei Gong,Junhui Hao,Zeyang Jang,Jiawei Yan,Tianle Bai,Yudong Xiao,Chun Wang
Near-infrared long-afterglow nanomaterials hold significant potential in nanomedicine platforms, including targeted drug delivery, precise imaging, and immunotherapy. Improving the particle size distribution and reducing the nanoparticle size to enhance biocompatibility are crucial. Due to the small size effect, reducing the nanoparticle size and improving uniformity typically lead to a decrease in afterglow performance. In this study, near-infrared long-afterglow nanoparticles, Zn 2 Ga 2.98 − x Ge 0.75 O 8 :Cr 3+ 0.02 ,Sm 3+ x ( x = 0, 0.02, 0.04, 0.06, 0.08) (ZGGO:Cr 3+ ,Sm 3+ x ), were synthesized using the Sm 3+ ion doping strategy at varying doping concentrations. This work reveals how cation substitution simultaneously affects the nanoparticle size and enhances the near-infrared long-afterglow luminescent performance. The Sm 3+ ion doping overcame the increased surface defects caused by the reduced particle size, while simultaneously improving the number of effective luminescent centers by modifying the crystal field environment around the luminescent center. The afterglow intensity and duration of ZGGO:Cr 3+ ,Sm 3+ x nanoparticles were significantly enhanced. The study shows that Sm 3+ ion doping effectively reduces the size of ZGGO:Cr 3+ ,Sm 3+ x nanoparticles while extending the near-infrared long-afterglow time by modulating trap depth, the interaction between traps and excited-state energy levels, and the competition between thermal activation and tunneling processes.
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