A vacuum-annealing strategy for improving near-infrared super long persistent luminescence in Cr3+ doped zinc gallogermanate nanoparticles for bio-imaging

摘要

Novel Cr3+ doped zinc gallogermanate (ZGGO) nanoparticles with 697 nm near-infrared (NIP) super long afterglow were prepared via a hydrothermal method. Subsequently, a vacuum-annealing strategy was adopted to improve NIR afterglow in ZGGO:Cr3+ nanoparticles. For the sample annealed at 800 degrees C, no variation in the particle size is observed, the persistent luminescence increases by an order of magnitude (similar to 14 times) and the NIR afterglow time reaches more than 15 hours relative to the as-prepared sample. After annealing at temperatures higher than 880 degrees C, the persistent luminescence of the nanoparticles is enhanced, but they show aggregated-surface behavior. Meanwhile, shallow and deep traps are generated, related to the Zn-Ga - Ga-zn antisite defects and V-Ge-Cr3+-V-o defect clusters, respectively. Finally, we apply ZGGO:Cr3+ persistent luminescence nanoparticles (PLNPs) to a human serum albumin (HSA) colloid solution, and more than 1 h of MR persistent luminescence is detected under 320 nm excitation. The quenching effect of NIR luminescence by OH- in the HSA solution is observed based on the reduced contribution of surface Cr3+ in PLNPs to NIR luminescence. Our results suggest that ZGGO:Cr7+ PLNPs have potential applications for in vivo bio-imaging.