Lanthanide-doped CaS NIR-Ⅱ Luminescent Nanoprobes:Controlled Synthesis,Optical Properties And Bioapplication

In this thesis,we provide a comprehensive survey on lanthanide(Ln³⁺)-doped CaS near-infrared-II（NIR-II）luminescent nanoprobes from the controlled synthesis,optical properties to their application for in vitro biodetection of disease biomarkers.The main research contents are as follows:First,we develop a unique strategy for the controlled synthesis of monodisperse and highly emissive Ln³⁺-doped CaS nanocrystals（NCs）with tunable size via a high-temperature co-precipitation method.By varying the ratio of the surfactants,the size of the NCs can be facilely tuned from 10 nm to 26 nm.X-ray diffraction（XRD）and Transmission electron microscope（TEM）characterizations reveal the cubic phase and high crystallinity of the resulting NCs.Second,we investigate systematically the optical properties of Ce³⁺singly-doped,Ce³⁺/Er³⁺and Ce³⁺/Nd³⁺co-doped CaS NCs by means of steady-state and transient photoluminescence（PL）spectroscopies.We reveal the influence of the NC size and doping concentration on the PL and energy transfer efficiency of the NCs.Specifically,through sensitization by Ce³⁺,highly efficient NIR-II luminescence from Er³⁺and Nd³⁺with PL quantum yields up to 9.3%and 7.7%is achieve in Ce³⁺/Er³⁺and Ce³⁺/Nd³⁺co-doped CaS NCs,respectively,under blue-LED excitation.Finally,to render the hydrophobic CaS:Ce³⁺,Er³⁺NCs hydrophilic and biocompatible,we conjugate the NCs with a layer of amphiphilic phospholipids（Lipo,DSPE-PEG-NH₂）through ligand adsorption.By taking advantage of the intense NIR-II luminescence,we demonstrate the application of the Lipo-coated CaS:Ce³⁺,Er³⁺nanoprobe for sensitive and selective detection of an important disease biomarker xanthine（XA）with a detection limit down to 32 nM.Further analytical parameters including the coefficient of variations（CVs;<6.7%）and the recoveries（in the range of98.8–106.2%）confirm the excellent accuracy and precision of the assay.These results reveal the great potential of CaS:Ln³⁺NCs as a new class of blue-LED-excitated NIR-II luminescent nanoprobes for clinic bioassays.