Research On The Synthesis And Properties Of Tellurium Compounds Quantum Dots

Due to their unique physical and chemical properties, quantum dots （QDs） orsemiconductor nanocrystals showed their potential applications in varioustechnological fields, such as biological labels, photoelectric device, and solar cells.The organic dyes were used as fluorescence probe to investigate mental ions in thewater in the past few years. Compared with the organic dyes, QDs have higherluminescent intensity, better stability and longer fluorescent lifetime. Therefore, usingthe QDs as fluorescence probe to investigate mental ions have attracted enormousattention in recent years.CdTe is one of the most important II-VI QDs and the band gap of CdTe is1.5eV.The main kinds of preparation methods for CdTe QDs are organic method andaqueous method. CdTe QDs synthesized by aqueous method have goodwater-solubility so that they can be directly used in ion detection. Anothersemiconductor material can be coated on the surface of the CdTe quantum dots toform core-shell structure in order to enhance the fluorescence intensity and stability.The main work of this paper is listed as follows:a)3-Mercaptopropionic acid capped CdTe QDs were synthesized in aqueoussolution under nitrogen protection. The samples were characterized byphotoluminescence （PL） spectroscopy, Ultraviolet-Visible （UV-Vis） spectroscopy,transmission electron microscopy （TEM） and X-ray diffraction （XRD）, respectively.The XRD result showed that CdTe QDs had a cubic zinc-blende structure and theTEM result showed that CdTe QDs were spherical with good dispersibility. Theeffects of reflux time, reflux temperature and pH on the property of QDs were studied.Experimental results showed that reflux time, reflux temperature and pH hadinfluenced on particle size, size distribution and the rate of growth. b)3-Mercaptopropionic acid capped CdTe QDs were synthesized in aqueoussolution, then we successfully synthesized CdTe/CdS core-hell QDs by choosingNa₂S as sulfur source. The more Na₂S, Cd（CH₃COO）₂and MPA we added to thesolution, the thicker CdS hell we got. XRD results showed that the QDs we obtainedhad a cubic zinc-blende structure. TEM result showed that CdTe/CdS QDs werespherical with good dispersibility. As the shell thickness increases gradually, particlesize of CdTe/CdS quantum dots increased, the fluorescence emission peaks showedredshift. At the same time, the luminescence intensity of CdTe/CdS QDs increasedsharply originally and decreased later. The luminescence intensity of CdTe/CdS QDsreaches its maximum when the shell/core value is1.C) CdTe QDs were used as the fluorescence probe to investigate metal ions inthe water. The results are as follows:（1） It was found that the luminescence intensity of CdTe/CdS QDs changedwhen different metal ions were added and the Ni²⁺showed strong fluorescencequenching effect.（2） The results showed that Ni²⁺can be detected by CdTe QDs and establishedthe Stern-volmer equation.