Bingji Wang

The effects of doping and shell thickness on the optical and magnetic properties of Mn/Cu/Fe-doped and Co-doped ZnS nanowires/ZnO quantum dots/SiO2 heterostructures

In this paper, we demonstrated the encapsulation of Mn/Cu/Fe-doped and co-doped ZnS nanowires (NWs) and ZnO quantum dots (QDs) with a layer of mesoporous SiO2 shell for the purpose of integrating dual emission and ferromagnetism property into one common nanostructure at room temperature. Within the ZnS:Mn2+Cu2+Fe2+/ZnO@SiO2 nanocomposites, ZnS:Mn2+Cu2+Fe2+ NWs and ZnO QDs provided color-tunable visible emission and UV emission, respectively. The color-tunable visible emission in the ZnS:Mn2+Cu2+Fe2+ NWs can be obtained by adjusting the concentrations of Mn2+, Cu2+, and Fe2+ ions. The ferromagnetism of the ZnS:Mn2+Cu2+Fe2+ NWs was observed around room temperature, the mechanism of which was explained by the super-exchange mechanism. The results of the effect of the ZnO QDs shell thickness on the optical properties of the ZnS:Mn2+/ZnO@SiO2 nanocomposites showed that the luminescence intensity of the yellow-orange emission and UV emission reached the highest value when the ratio of ZnS:Mn2+/ZnO equaled 1:5.

Effects of surface modification and SiO2 thickness on the optical and superparamagnetic properties of the water-soluble ZnS:Mn2+ nanowires/Fe3O4 quantum dots/SiO2 heterostructures

In this paper, one-dimensional ZnS:Mn2+ nanowires (NWs)/Fe3O4 quantum dots (QDs)/SiO2 heterostructures were successfully synthesized by the Stober method to form the water-soluble fluorescent/superparamagnetic nanocomposites. The average diameter of the ZnS:Mn2+ NWs, Fe3O4 QDs and ZnS:Mn2+ NWs/Fe3O4 QDs/SiO2 heterostructures was about 6–8 nm, 4–5 nm and 18 nm, respectively. The Fe3O4 QDs were covalently linked to the ZnS:Mn2+ NWs by the conjugation of the hydroxyl groups on the surface of the QDs and the carboxyl groups modified on the surface of the NWs. It was found that the covalent bonds between the NWs and QDs could effectively suppress the energy transfer from the ZnS:Mn2+ NWs to the Fe3O4 QDs. As the SiO2 shell thickness increased, the fluorescence intensity reached the highest value when the hydrolysis time of tetraethyl orthosilicate was 5 hours, which was comparable to that of the ZnS:Mn2+ NWs. The superparamagnetic properties of the heterostructures were observed at room temperature, which decreased as the SiO2 thickness increased.