Study On Preparation And Property Of Water-Soluble Doped ZnS Fluorescent Quantum Dots

Due to their unique optical and chemistry property, fluorescent quantum dots have attracted extensive attentions in biomedical labeling, cell imaging and analytical chemistry fields. At present, cadmium-containing quantum dots possess high quantum yield, but their biotoxicity have restricted the development of cadmium-containing quantum dots. However the low toxicity of zinc-containing quantum dots have received more and more extensive attentions. In attition, the transition metal ion doped and surface modification can not only improve the quantum efficiency of zinc-containing quantum dots but make them have good water solubility and biocompatibility. So this paper focuses on synthesizing water-soluble L-cysteine-modified doped ZnS core/shell quantum dots with high quantum yield in aqueous solution, results are listed as following:(1) Water-soluble ZnS:Mn and ZnS:Mn/ZnS quantum dots have been synthesized successfully using L-cysteine as stabilizer in aqueous solution. X-ray power diffraction (XRD), transmission electron microscope(TEM), energy dispersive X-ray analysis(EDX), infrared spectrum(IR), UV-Vis absorption spectrum(UV-Vis) and photoluminescence spectrum(PL) were applied to characterize the structure, morphology, size, component and optical property of the quantum dots. The results showed that L-cysteine-modified ZnS:Mn and ZnS:Mn/ZnS quantum dots have good monodispersity, excellent fluorescence property, water-soluble and biocompatible. The quantum yield of quantum dots increased from2.4%to15.1%after doped with Mn2+and ZnS shell formed.(2) Water-soluble ZnS:Co and ZnS:Co/ZnS quantum dots have been synthesized successfully using L-cysteine as stabilizer in aqueous solution. XRD、TEM、EDX、IR、 UV-Vis and PL spectrum were applied to characterize the structure, morphology, size, component and optical property of the quantum dots. The influences of prepartion conditions on the fluorescence characterization of the quantum dots were investigated in detail by PL spectrum. The results showed that L-cysteine-modified ZnS:Co and ZnS:Co/ZnS quantum dots have good monodispersity, excellent fluorescence property, water-soluble and biocompatible. The quantum yield of quantum dots increased from 2.4%to9.8%after doped with Co2+and ZnS shell formed. The optimal synthetic conditions:50℃, n(L-Cys):n(Zn2+):(S2’):(Co2+)=2:1:1:0.02, pH=11.0, nc:ns=1:0.15.(3) Water-soluble ZnS:Cu quantum dots have been synthesized by co-precitation menthod using L-cysteine as stabilizer in aqueous solution. XRD、TEM、EDX、IR、 UV-Vis、and PL spectrum were applied to characterize the structure, morphology, size, component and optical property of the quantum dots. The results showed that the ZnS:Cu quantum dots have good monodispersity, excellent fluorescence property, water-soluble and biocompatible. The quantum yield of quantum dots increased from2.4%to4.3%after doped with Cu2+.