荧光成像技术是生物医学常用的分析手段。其中，第二近红外区域（NIR-II）荧光成像因具有穿透深度大、光散射作用小等优点，可获得活体深层组织器官的高分辨荧光图像，在活体成像领域表现出得天独厚的优势。稀土络合物具有Stokes位移大、发射峰窄、发射谱带丰富等优点，是一类极具潜力的NIR-II荧光材料。但稀土络合物对近红外光的吸收能力弱，致使其NIR-II发光效率低，严重阻滞了其在活体成像领域的应用。本项目拟基于染料敏化作用增强稀土络合物的近红外光吸收能力，显著提升其NIR-II发光效率，进而构建新型NIR-II荧光探针。拟探究该类探针NIR-II发光效率与染料分子、配体结构、稀土离子种类间的构效关系，获取染料对稀土络合物NIR-II发光增敏效能的调控策略，并实现高分辨活体荧光成像，为开发性能优异的NIR-II荧光探针提供新思路，奠定稀土络合物NIR-II荧光探针用于活体成像的实践及理论基础。

Fluorescence imaging technique has been commonly used in biomedical assays. Noticeably, the second near-infrared (NIR-II) fluorescence imaging shows some superior characteristics for in vivo imaging, and can provide high-resolution fluorescence images of deep tissues in living animals, due to high penetration depth and weak photon scattering. Rare-earth complexes possess some crucial merits including large Stokes shift, sharp and tunable emissions, and are considered as promising NIR-II luminescent materials. Unfortunately, the low NIR-II emission efficiency, originating from the faint absorptivity of rare-earth ions, seriously retards their applications in bioimaging. In this project, novel NIR-II fluorescence probes will be designed based on a dye-sensitization strategy through the integration of NIR organic dyes with rare-earth complexes. The NIR-II emission efficiency of rare-earth complexes can be significantly improved through promoting their photon-absorption abilities with the assistance of organic dyes. The structure-activity relationship between the emission efficiency of the NIR-II fluorescence probes and the structure of organic dyes and organic-ligands, and the choice of rare-earth ions will be investigated for exploring regulating strategies to obtain the optimized sensitization performance. Furthermore, in vivo high-resolution fluorescence imaging will be confirmed using the developed dye-sensitized rare-earth complexes system as NIR-II fluorescent probes. Herein, a novel strategy has been proposed for developing the rare-earth complexes based NIR-II fluorescence probes, and provides significant theoretical reference and experimental database for the promising applications of the rare-earth complexes based fluorescence probes in NIR-II bioimaging.