The Synthesis And Photoluminescence Of ZnS,ZnS:Mn²⁺ Quantum Dots

ZnS quantum dots are the important part of luminescent material, its advantage is the broad and continuous absorption spectrum, narrow and symmetrical fluorescence emission spectrum, long fluorescence lifetime. The Mn2+-doped ZnS quantum dots possess excellent thermal stability and spectral stability. Both ZnS and ZnS:Mn2+quantum dots have great application prospects in the field of light-emitting devices, laser diode, semiconductor, photovoltaic devices, protein markers, cell biology, genomics and so on. In this paper, we synthesized ZnS and ZnS:Mn2+quantum dots with two methods and studied the effect experimental conditions on fluorescent properties. We compared the fluorescent characteristic of ZnS quantum dots with ZnS:Mn2+and combined ZnS quantum dots with ZnS:Mn2+quantum dots to study overall fluorescent properties.we synthesized ZnS quantum dots with ethylene glycol as solvent, triethanolamine as a complexing agent, Zinc acetate as a source of zinc, sodium sulfide as sulfur source at120℃,pH=10.TEM images showed that the average diameter of prepared ZnS quantum dots was7nm. The XRD result indicated that the prepared ZnS was sphalerite structure. When we examined the impact of time on the fluorescence, we discovered that the maximum emission intensity was obtained when the refluxing time was2h.When we made a study of PH effect on fluorescence intensity, we drew a conclusion that alkali had little effect on fluorescence, but acid could made fluorescence of ZnS quenchable and this effect was irreversible.We synthesized ZnS quantum dots with ethylene glycol as solvent, hydrogen sulfide as the sulfur source through gas-liquid two-phase reaction. The XRD result indicated that the prepared ZnS was sphalerite structure. TEM images showed that the average diameter of prepared ZnS:Mn2+quantum dots was about7nm.It was found that when Mn2+doped concentration was at1%mol, the maximum emission intensity was gained. We studied on the effect of reflux time and reflux temperature, the results showed that we obtained maximum emission at the condition of110℃,0.5h.We also examined the impact of mixed solvent of water and ethylene glycol on fluorescence, it was demonstrate that when we used pure ethylene glycol as solvent, the fluorescent intensity was relative stronger. It was found that the PL gradually reduced in air, which indicated that Mn2+:ZnS quantum dots can be preserved in air for long time.We compared fluorescence characteristic of ZnS with ZnS:Mn2+quantum dots, we knew that emission spectra of ZnS emitting at448nm was narrower than ZnS:Mn2+emitting at573nm.When we combined ZnS and ZnS:Mn2+in different volume ratio, we examined the results that the combined ZnS and ZnS:Mn2+could generated a new kind of light:white light which has potential application in QD-LED.