Synthesis Of High Quality InP-Based Quantum Dots And Their Application For Fluorescence Quantitative Detection Of C-Reactive Protein

Quantum dots（QDs）,as a new fluorescent probe,are widely used in biomedical fields such as cell labeling,photodynamic therapy and biosensing due to their adjustable luminescence peak,high quantum yield,high color purity and good chemical stability.Especially in the field of in vitro diagnotics,the chemical synthesis of QDs materials with high quantum yield and high stability suitable for biological environment is a necessary condition for the construction of high quality fluorescent probes.At present,the application research of QDs fluorescence probes is mostly based on groupⅡ-ⅥQDs materials,the Cd-based QDs as a represent have made great progress.InP-based QDs not only have the advantages of Cd-based QDs,but also have excellent biocompatibility.To meet the vitro diagnosis needs,the high-quality InP-based QDs are critical to be synthesized in order to construct bright and stable fluorescence probes.In this paper,the high-quality InP core-shell structure QDs were constructed bright and ultra-stable fluorescence probes to realize the rapid and sensitive detection of C-reactive protein（CRP）.What’s more,the construction of high-quality InP QDs were mainly through improving the lattice matching degree between InP core and shell material and shell thickness.The details are as follows:（1）Synthesis of InP/ZnSe/ZnS/ZnS core-shell quantum dots with thick shells and their application for quantitative detection of CRP.Based on the shell design strategy,oleamine-sulfur（OAm-S）and dodecanethiol（DDT）were used as sulfur precursors by regulating the activity of the precursor and taking advantage of the different characteristics of the reactivity of sulfur compounds of different ligands.OAm-S has high activity and acts as a precursor to the growth of inner layer ZnS.DDT is less active and acts as a precursor to the growth of outer layer ZnS.The main reason is that the activity of DDT is low,so it can grow thicker ZnS shells.DDT can be used as a sulfur source or ligand,and the bonding ability of sulfhydryl group is stronger than that of amine group,which is conducive to improving the stability of quantum dots.Based on this,the thick-shell InP/ZnSe/ZnS/ZnS core-shell QDs with an average size of 8.99 nm and quantum yield of more than 80%were successfully synthesized.Subsequently,the aqueous phase transfer of the QDs was realized by polymer coating method.The aqueous phase quantum dots can maintain high fluorescence intensity at p H=4-12 and in different buffer solutions,showing good stability.The biological probe was successfully assembled based on fluorescence linked immunsorptionbent assay（FLISA）to achieve quantitative detection of CRP,with the limt of detection（LOD）7.81 ng/m L and the detection range of 10-400 ng/m L.（2）Synthesis of graded InP/ZnSe/ZnSe_xS_（1-x）/ZnS/ZnS quantum dots and their application for quantitative detection of CRP.In this chapter,based on the precise design strategy of shell structure,ZnSe_xS_（1-x）alloy layer is introduced between ZnSe and ZnS shells to reduce the accumulation of lattice stress and reduce the influence of surface effects on QDs.The graded InP/ZnSe/ZnSe_xS_（1-x）/ZnS/ZnS QDs with a quantum yield of 90%and an average size of 10.74 nm were synthesized.The fluorescence attenuation curve of stable oil phase InP-based core-shell QDs is almost unchanged after water phase transfer,showing ultra-high stability.In addition,the fluorescence intensity of aqueous QDs can maintain above 80%at p H=3-13and in different buffer solutions,showing excellent stability of biological environment.Fluorescent probe was assembled based on FLISA and applied to the detection of CRP.The LOD was 0.95 ng/m L,and the detection range was 1-800 ng/m L.Compared with the previous chapter,the detection sensitivity was increased by 8 times.In conclusion,InP core-shell structure QDs with high quantum yield and high stability have been successfully synthesized through the introduction of double-layer ZnS shell and ZnSe_xS_（1-x）alloy layer,and realize high sensitive detection of CRP as fluorescence probes.