One-step construction of bifunctional nanoprobes for NIR afterglow and T_2-weighted MR imaging

摘要

In this study, spinel-phase Zn_2Ga_(3-x)Fe~(3+)xGe_(0.75)O_8 (x = 0, 0.002, 0.004, 0.02, 0.04, 0.08, 0.2) and Zn_2Ga_(2.98-x)Fe~(3+x)Cr_(0.02)Ge_(0.75)O_8 (x = 0, 0.0004, 0.001, 0.002 0.003, 0.004) nanoparticles were prepared by one-step hy-drothermal method in combination with vacuum annealing. For ZGGO: Fe + nanoparticles, the near infrared (NIR) emissions (~725 nm) originate from the T1(~4 G)→ A_1( ~6S) transition of Fe~(3+) occupying octahedral and tetrahedral sites of Ga~(3+). Furthermore, their afterglow time is more than 15 min and Fe~(3+) doping will infuence the generation of antisite defects pair (Ga_(zn)~) Zn_(Ga)). For Cr~(3+) and Fe~(3+) co-doped ZGGO nanoparticles with average size of ~46 nm, the NIR persistent luminescence around ~700 nm, originating from the ~2E→ ~4A_2 and T_2→~4A_2 transitions of Cr~(3+), can be observed and the afterglow time exceeds 850 min. With the increase of Fe~(3+) concentration, the afterglow intensity decreases due to the decreased number of (Ga_(Zn)~) Zn_(Ga)) defects and deeper traps. In particular, autofuorescence-free imaging and MR imaging were successfully realized by using ZGGO: Cr~(3+), Fe_(0.02)~(3+) nanoparticles dispersed in the simulated biological fuid environments (H_2O, SLS and HSA). Their clear afterglow images can be acquired within 3 min after the stoppage of the UV irradiation and their transversal relaxivity (r_2) is in the range of 227-140 mM~(-1) s~(-1) , which is close to the conventional Feridex T_2 agent (108 mM~(-1)s~(-1) ). Our results suggest that ZGGO: Cr~(3+), Fe~(3+) nanoprobes have potential applications in the diagnosis and therapy of disease.