Near-Infrared Long-Persistent Phosphors Based On Novel Spinals: Synthesis, Luminescence Mechanism And Application

In this dissertation,near-infared and long-persistent luminescent nanoparticles(NLPLNPs)of spinel-structured ZnGa2-x(Mg/Ge)xO4:0.005Cr3+have been synthesized by sol-gel processing,with emphasis on the tunable composition structures and band gaps.The luminescent properties and afterglow emission mechanism were defined.The construction of nano-probes and the biological applications were achieved.Detailed characterizations of the samples were achieved by combined techniques of XRD,FE-SEM,HR-TEM,STEM,SAED,FT-IR,UV-vis,PL/PLE,long-persistent decay curve,nanoprobe toxicity analysis,in vivo and in vitro imaging analysis,and the main conclusions are listed as follows.The spinel-structured nanoparticles of ZnGa2-x(Mg/Ge)xO4:0.005Cr3+ with a diameter of 50?200 nm have been abtained by sol-gel processing,followed by calcinations at 1000?.When the doping amount x of Mg2+/Ge4+is above 1.25,the products are not a pure phase.Under UV exciation at 265 nm,the phosphor exhibitits typical near-infrared emission centered at 695 nm,and enhanced fluorescence intensities were observed with increasing the calcination temperature.The morphology and crystal lattice parameters of phosphors are not significantly affected by the incorporation of Mg2+/Ge4+.However,worse crystallinity,down shifting of the 2E and 4T2 energy levels,up shifting of the 4T1(4P)and 4T1(4F)energy levels,widened band gap,were resulted from the incorporation of Mg2+/Ge4+.Strongest fluorescence intensity and longest afterglow time were soberved for the x=1 sample.Thus,the ZnGaMg0.5Ge0.5O4:0.005Cr3+ was identified as the optimized sample,whose afterglow can last more than 48 h after the stoppage of UV excitation.Furthermore,the afterglow was enhanced and lasted at least 6 h after re-excited with a red LED,exhibiting an excellent recharging ability.The well-dispersed NLPLNPs with low toxicity(diameter of ?100 nm)processed by surface modification exhibited good biocompatibility and water solubility,which can be successfully applied in tissue and cell imaging(labeling).NIR fluorescence in vivo imaging was performed by subcutaneous and intravenous injection of NLPLPS-NH2 probes,which emitted NIR emission in vivo for 120 min in the absence of in situ excitation and for another 120 min through re-excition by a red LED.The NLPLNPs-NH2 probes were mainly distributed in the liver and spleen by the in vitro organ imaging.The whole experiment shows that the NLPLNPs are ideal materials for in vivo targeted imaging with the characteristics of low background noise,and high sensitivity and signal-to-noise ratio.