中文摘要：

采用溶剂热法在稀土掺杂NaYF4∶Yb3＋,Er3＋上转换纳米粒子上包覆一层NaGdF4,再利用反相微乳液法在NaGdF4上覆盖一层TaOx,从而合成NaYF4∶Yb3＋,Er3＋@NaGdF4@TaOx核壳壳结构的纳米探针。使用透射电镜（TEM）、X射线衍射（XRD）及X射线能量色散谱分析（EDS）对NaYF4∶Yb3＋,Er3＋@NaGdF4@TaOx纳米探针的结构和组成进行表征。并通过荧光光谱、磁滞回线以及电子计算机X射线横断扫描（CT）造影成像等方法对其性能进行了表征,证明该纳米探针具有良好的光学、磁学和CT造影特性。将NaYF4∶Yb3＋,Er3＋@NaG-dF4@TaOx纳米探针应用于小鼠活体成像实验,结果表明,这种纳米探针对小鼠肿瘤部位的磁共振成像（MRI）和CT信号均有较好的增强效果,表明其在多模态造影成像方面有潜在的应用前景。

英文摘要：

Using solvothermal method,NaYF4 ∶ Yb3＋,Er3＋@NaGdF4 was synthesized by deposition of a layer of NaGdF4 on the NaYF4 ∶ Yb3＋,Er3＋ upconverting nanoparticles（UCNPs） Then,NaYF4 ∶ Yb3＋,Er3＋@NaGdF4@TaOx core@shell@shell nanoparticles were prepared through decorating the radiopaque but fluorescence-transparent TaOx onto the surface of NaYF4 ∶ Yb3＋,Er3＋@NaGdF4 by a facile reverse microemulsion strategy.The structure of the NaYF4 ∶ Yb3＋,Er3＋@NaGdF4@TaOx nanoparticle was characterized by transmission electron microscopy（TEM）,powder X-ray diffraction（XRD）,energy-dispersive X-ray analysis（EDS）.The X-ray attenuation,magnetic and upconversion luminescent studies suggested that the as-prepared NaYF4 ∶ Yb3＋,Er3＋@NaGdF4 @TaOx nanoparticle could be employed as multimodal nanoprobe for bioimaging applications.Furthermore,the feasibility of NaYF4 ∶ Yb3＋,Er3＋@NaGdF4 @TaOx for electronic computer X-ray transaction scan/magnetic resonance imaging（CT/MRI） in vivo was demonstrated.The brightness enhancement of MRI and CT signals in the tumor region were clearly observed at prolonged post-injection to 0.5 h,indicating that the NaYF4 ∶ Yb3＋,Er3＋@NaGdF4 @TaOx hold great potential for multimodal imaging in vivo.