Controlled Synthesis And Bioimaging Application Of Lanthanide-doped Nanocrystals

The current thesis involves the research into the lathanide-doping mechanism on the formation of Na Mn F3:Yb,Er nanoparticles in Liquid-Solid-solution?LSS?solvothermal system,and the development of a facile synthetic method based on this mechanism for the preparation of lanthanide-doping or shell-coating nanoparticles,and the application of the resulting lanthanide-doping downconversion core-shell nanoparticles in multimodal imaging of tumor.First,LSS solvothermal method was exploited to prepare hollow Na Mn F3,Na Mn F3:Yb,Er and solid Na Yb F₄:Er nanostructures.The morphology,component and optical property of nanoparticles at different synthetic stages were comprehensively characterized to figure out the doping mechanism in the formation of Na Mn F3:Yb,Er nanoparticles.The nanostructures can be well tuned by controlling the molar ratio of Mn2+ and F-.The results demonstrate that different sized host matrix?Na Mn F3?and lanthanide?Yb-Er?precursors are formed respectively at room temperature through the reaction of LSS system,and the lanthanide-doping process follows the basic principle of selffocusing effect,which is that the difference in their solubility causes the growth of larger sized Na Mn F3 nanoparticles at the expense of smaller sized lanthanide nanoclusters at high temperature.In addition,the controlled synthesis of Na Mn F3:Yb,Er hollow and solid nanostructures is found to be dependent on the morlar amount of Mn2+ and F-.Second,based on the insights into lanthanide-doping mechanism in LSS solvothermal system,the nanocluster precursors of core,dopant,shell were prepared at room temperature,and used to synthesize Nd3+ ion doped nanoparticles through self-focusing effect in one pot reaction.Four types of Nd3+-doped nanoparticles were obtained from different combination of Na YF₄ and Na Gd F₄ as core and shell respectively.The dependence of their optical propties on particle size and structure shows Na YF₄:Nd@Na Gd F₄ core-shell nanoparticles possess the strongest luminescence.Finally,Na YF₄:Nd@Na Gd F₄ core-shell nanoparticles with the strongest luminescence were selected for the application of bio-imaging.They were modified with DSPE-PEG2 k to show excellentcolloid stability and biocompatibility.The NIR II luminescence of nanoparticles was utilized for monitoring the evaluation of tumor vasculature from subcutaneous 4T1 tumor-bearing mice with different growth time.The results are compared and verified by H&E histological analysis.The T1-weighted magnetic resonance imaging and X-ray computed tomography were performed on tumor-bearing mice with dense vasculature to overcome the penetration issue of NIR II imaging.The results demonstrate the advantage of multimodal imaging in acquiring comprehensive and accurate imaging information.