Preparation And Properties Of The Doped ZnS Quantum Dots

As a wide band gap luminescent material, ZnS quantum dots have broad and continuous optical absorption spectra, narrow and symmetrical fluorescence emission spectra, long fluorescence lifetime and good photochemical stability. At the same time, due to the low toxicity of zinc-based quantum dots and the introduction of dopant ions, there are new electron energy levels, with new electrical, optical and magnetic properties. Because of these special properties, the doped quantum dots have a great application prospects in nano optoelectronic devices, fluorescent labeling, genomics and other research fields.In this paper, we adopt aqueous coprecipitation method and use ZnS as a substrate, the microstructure and optical properties of the quantum dots were studied by doping Mn2+, Co2+ into ZnS. The structure of the ZnS quantum dots is the cubic sphalerite structure, its particle size is about 4.8 nm with agglomerated. It is irregular ball, with uniform particles. Under 320 nm excitation, ZnS is single peak emission and shows the highest fluorescence emission intensity at 544 nm wavelength. The preparation of 1%～5%(mole fraction) ZnS:Mn2+ quantum dots is cubic sphalerite structure, indicating that trace Mn2+ doping on ZnS phase structure isn’t much affected, the particles size is about 8.8 nm with particles agglomeration, irregular ball type. Mn2+ doped ZnS quantum dots have two emission peaks, which are located in 660nm and 685 nm, respectively, and the maximum intensity of the luminescence intensity belongs to 4% Mn2+ doped ZnS quantum dots. The preparation of 1%-5%(mole fraction) ZnS:Co2+ quantum dots is cubic sphalerite structure, where appears miscellaneous peak at 2% and 4% of Co2+ doped ZnS quantum dots, indicating that there is formation of cobalt sulfide. When a trace amount of Co2+ doping, the phase structure of ZnS is not too much influence, the size is about 7.5 nm with particles agglomeration, irregular ball type. Co2+ doped ZnS quantum dots have two emission peaks where at 765 nm and 784 nm, and the 4% Co2+ doped ZnS quantum dots apprears the maximum luminance intensity.