Influence Of The Addition Of Rare Earth Ions On The Long Afterglow Luminescence Of Germanate Nanoprobes

In the field of biological or medical research,luminescence imaging techniques can be used to obtain clear,intuitive static or dynamic images,and even to observe the cellular state of local tissues or the distribution of specific molecules in the body.At present,the development of luminescence imaging technology is mainly limited by the absorption of light by organisms and the self-excited fluorescence of organisms.In recent years,near-infrared long afterglow luminescent nanoparticles,as a representative of the new generation of imaging agents,can effectively solve the current dilemma.Near-infrared long afterglow luminescent nanoparticles can solve the problems associated with conventional imaging such as high cost,low sensitivity,prolonged in situ real-time monitoring and varying degrees of harm to the body.Most of the developed NIR long afterglow nanoprobes are based on Cr³⁺as the luminescence centre,however,Cr³⁺is highly toxic to living organisms,which has limited the application of NIR long afterglow nanoprobes in luminescence imaging.Therefore,the development of novel long afterglow nanoprobes with low toxicity and high stability is of great significance for the practical application of long afterglow luminescence imaging.In this thesis,a germanate-based long afterglow nanoprobe with Mn²⁺as the luminescence centre was designed and synthesized.This probe has low toxicity and excellent biosafety,and its luminescence wavelength is 650 nm,which belongs to the near-infrared region and is beneficial for bioimaging.The CaMg Ge₂O₆:Mn²⁺synthesized by complexed sol-gel method has excellent chemical stability and small particles（around 15-30 nm）.Based on this,the effect of the addition of different rare earth ions such as Sm³⁺,Dy³⁺,Yb³⁺and Eu³⁺on their long afterglow luminescence properties was investigated,and the mechanism of the effect of different rare earth ions on the long afterglow luminescence of germanate nanoprobes was also investigated in this study.Through pyrophoric luminescence and spectroscopic characterization,it is found that the rare earth ions can modify the afterglow luminescence by modulating the gain and loss of electrons to obtain more trap species and higher trap concentrations.Based on the above findings,a new long afterglow luminescent mechanism is proposed to explain the possible reasons for the enhancement or weakening（or even quenching）of long afterglow luminescence by the co-doping of Mn²⁺with different rare earth ions in this paper.Finally,CaMg Ge₂O₆:0.5%Mn²⁺,1%Sm³⁺with the optimal luminescence performance was chosen for in vivo imaging and the obtained results show that the imaging is well defined and sensitive,and the in vivo imaging time can persist 15 min.