Determination Of Heavy Metal Ions Cd²⁺、Zn²⁺ And As（Ⅲ） By Water Soluble CdS、CdTe Quantum Dots Fluorescent Probe

Compared to conventional organic dyes, quantum dots are advantageous overfluorescent dyes because of their wider excitation spectra, narrower emission spectra,high quantum yield and the resistance to photo bleaching, have generated great researchinterest to people. Especially as a new type of fluorescent probe has a broad applicationprospect in biological assay, fluorescence imaging etc. In the present paper, theemphases of the studying rest with water-solubility quantum dots as luminescent sensorfor the determination of some small organic molecules and the photoluminescencebioimaging of intracellular zinc ion and cadmium ion in solanum nigrum endophytes.And the works such as quanium dots preparation and characterization were completed.The main tasks are as follows:Synthesis and performance study of Zinc-doped water-soluble CdS QDs. In anaqueous solution, using the water phase systhesis method when using GSH asmodification stabilizer under nitrogen atmosphere to synthetize the goodwater-solubility quantum, zinc-doped GSH-CdS QDs. Explore the effects of thedifferent Cd/Te mole ratio, the concentration of zinc ions and pH value on thefluorescence intensity of GSH-capped CdS QDs. It is suggested that CdS QDs showgood fluorescence performance at conditions when pH=7.5, CZn=0.022mmol andCd/S=2:1. This method is simple, the synthesis of quantum dots have goodwater-soluble and photochemical stability. The samples were characterized by scanningelectron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-rayspectroscopy (EDS) and fluorescence emission spectroscopy.We show the fabrication of silica-coated S2--enriched Zn-doped CdS quantum dots(SiO2-S-Zn-CdS QDs) by enriching S2-with a silica shell on the surface of Zn-dopedCdS QDs via a sol-gel process and the quantum dots also can be used as fluorescentprobe for selective detection Cd2+and Zn2+ions. A good linear relationship existsbetween fluorescence intensity and the concentration of Zn(II) in the3.5-23.2μMconcentration range and a detection limit at2.0μM. The probes also responds to Cd(II)in the0.3-26μM concentration range and with a0.1μM limit of detection. In addition,the silica-coating on the enriched S2-on the surface of Zn-doped CdS QDs effectivelyavoids the leakage of S2-, enhances the biocompatibility and stability, and provides a low fluorescence background signal. The SiO2-S-Zn-CdS QDs have successful forfluorescent imaging intracellular of solanum nigrum endophytes.In an aqueous solution, using the water phase systhesis method when using GSH asmodification stabilizer, Na2TeO3as stable Te source and NaBH4as reducing agent inthe100℃heating under reflux to synthetize the GSH-CdTe. By controlling thereaction time can get different size of CdTe QDs and exploring the effects of differentvalence states arsenic ions on the CdTe QDs. The quantum dots can be used asfluorescent probe for selective detection As3+ions and the fluorescent intensity ofquantum dots nearly quenching when As3+exist in solution. A good linear relationshipexists between fluorescence intensity and the concentration of As（Ⅲ）in the0.2-2.2μM concentration range and a detection limit at20nM.