Near Infrared-Emitting Cr(3+)/Eu(3+) Co-doped Zinc Gallogermanate Persistence Luminescent Nanoparticles for Cell Imaging

Near infrared (NIR)-emitting persistent luminescent nanoparticles have been developed as potential agents for bioimaging. However, synthesizing uniform nanoparticles with long afterglow for long-term imaging is lacking. Here, we demonstrated the synthesis of spinel structured Zn(3)Ga(2)Ge(2)O(10):Cr(3+) (ZGGO:Cr(3+)) and Zn(3)Ga(2)Ge(2)O(10):Cr(3+),Eu(3+) (ZGGO:Cr(3+),Eu(3+)) nanoparticles by a sol-gel method in combination with a subsequent reducing atmosphere-free calcination. The samples were investigated via detailed characterizations by combined techniques of XRD, TEM, STEM, selected area electron diffraction, photoluminescence excitation (PLE)/photoluminescence (PL) spectroscopy, and temperature-dependent PL analysis. The single-crystalline nanoparticles are homogeneous solid solution, possessing uniform cubic shape and lateral size of ~ 80–100 nm. Upon UV excitation at 273 nm, ZGGO:Cr(3+),Eu(3+) exhibited a NIR emission band at 697 nm ((2)E → (4)A(2) transition of distorted Cr(3+) ions in gallogermanate), in the absence of Eu(3+) emission. NIR persistent luminescence of the sample can last longer than 7200 s and still hold intense intensity. Eu(3+) incorporation increased the persistent luminescence intensity and the afterglow time of ZGGO:Cr(3+), but it did not significantly affect the thermal stability. The obtained ZGGO:Cr(3+),Eu(3+)-NH(2) nanoparticles possessed an excellent imaging capacity for cells in vitro.