Preparation And Luminescence Properties Of Zn:Cu Nanocrystals

Ⅱ-Ⅵ semiconductors are direct band gap semiconductors, with the energy covering theentire visible light range, so they are a kind of important photosensitive materials.semiconductor ZnS not only has strong broadband absorption, but also produces opticalnonlinear response, superior optical activity, so it is widely used as the light-emitting material,nonlinear optical material,photocatalytic material. ZnS is also a good matrix material, ZnSdoped with the activators can be a semiconductor nanophosphors which luminescentproperties is excellent. This paper focuses on synthesis and photoluminescent properties ofZnS:Cu nanomaterials and the detection of metal ions. then the shell coated for surfacemodification, which aimed at improving the luminescence efficiency by diminishing oreliminating the surface states.The main work of this paper is listed as follows:1. ZnS:Cu nanoparticles have been synthesised via a water-soluble route, studying theeffect of the amount of doped copper, the reaction temperature, the reaction time, pH and theratio of Zn/S on the ZnS:Cu nanoparticles photoluminescence properties. The opticalproperties of the nanoparticles are analyzed by fluorescence spectrophotometer(PL、PLE) andUV-visible spectrophotometer(UV-Vis),and its phase and morphology are characterized byX-ray diffraction (XRD) and transmission electron microscopy (TEM). The testing instumentssuggest that ZnS: Cu nanoparticles in this method are cubic sphalerite structure, gooddistribution, and its size is about2nm. The best experiment conditions have got by the singlefactor analysis, it is when Cu2+concentration is1%, the reaction temperature is80℃, thereaction time is4h, pH is11and the ratio of Zn/S is2:1.2. The ZnS shell and CdS shell have coated on the ZnS:Cu core, then the ZnS:Cu/ZnSand ZnS:Cu/CdS core/shell structure nanocrystals have been synthesised. The crystal structure,morphology and optical property of nanocrystals were characterized by X-ray diffraction,transmission electron microscopy, PL and UV-Vis absorption spectroscopy. The resultshowed the shell with appropriate thickness can enhance the photoluminescence intensity of ZnS:Cunanomaterials, at the same time, The photoluminescence property of different kinds of shellmaterials are different. The details are as follows:(1) The photoluminescence property of ZnS:Cu with different thickness ZnS shell hasbeen studied. The samples are characterized by XRD、PL、PLE�'�UV-vis. The PL showedThe PL intensity related with Cu2+increased at the beginning and decreased with furthergrowth of the ZnS shell. The intensity of emission peak achieved the maximum when ns/nc is2.5. The TEM and UV-vis proved that the ZnS shell growed on the ZnS:Cu quantum dotssurface and formed the ZnS:Cu/ZnS core/shell structure quantum dots.(2) The photoluminescence property of ZnS:Cu with different thickness CdS shell hasbeen studied. The samples are characterized by XRD、PL、PLE�'�UV-vis. The PL showedThe PL intensity increased at the beginning and decreased with further growth of the CdSshell. The intensity of emission peak achieved the maximum when ns/nc is1.0. The TEM andUV-vis proved that the CdS shell growed on the ZnS:Cu quantum dots surface and formed theZnS:Cu/CdS core/shell structure quantum dots.3. ZnS: Cu quantum dots as the ion microprobe for testing on a variety of common metalions and found that has a good select of Pb ion. The detection of different concentrations of Pbions was further studied and got a good linearity Stern-volmer equation. The ZnS: Cuquantum dots can be the ion microprobe for quantitative research of Pb ions.