Facile synthesis of magnetic-fluorescent and water-soluble ZnS:Mn~(2+)(-SH)/Fe_3O_4(-SH)/SiO_2 core/shell/shell nanocomposites with pure dopant emission

摘要

In this paper, we synthesized water-soluble ZnS:Mn~(2+)(-SH) nanowires (NWs)/Fe_3O_4(-SH) quantum dots (QDs)/SiO_2 core/shell/shell nanocomposites with pure dopant emission, room temperature superparamagnetic and excellent photostablility. The average diameter of the Fe_3O_4 QDs, ZnS:Mn~(2+) NWs, ZnS:Mn~(2+)(-SH)/Fe_3O_4(-SH) and ZnS:Mn~(2+)(-SH)/Fe_3O_4(-SH)/SiO_2 nanocomposites was about 3, 7, 8.5 and 10 nm, respectively. The dopant emission intensity of the functionalized ZnS:Mn~(2+) (-SH)/Fe_3O_4(-SH)/SiO_2 nanocomposites was much higher than that of the ZnS:Mn~(2+)/Fe_3O_4/SiO_2 nanocomposites due to MPA modification. The ZnS:Mn~(2+)(-SH)/ Fe_3O_4(-SH)/SiO_2 nanocomposites also exhibited excellent photostability under the intense UV irradiation because of the blocking of exciton migration and retarding exciton trapping at local defects by the SiO_2 shell. The superparamagnetic properties of the nanocomposites were also studied at room temperature, and the magnetic saturation value was decreased as the SiO_2 thickness increased.