Biocompatible ZnS:Mn(2+) quantum dots/SiO2 nanocomposites as fluorescent probe for imaging HeLa cell

ZnS:Mn(2+) quantum dots (QDs) were successfully embedded in SiO2 spheres by a reverse microemulsion method. The results showed that the monodispersed core/shell nanocomposites were uniform in size, with the majority of the SiO2 nanoparticles containing one QD in the center of the sphere. The shell thickness of SiO2 increased from 7 to 18 nm as the hydrolysis time of TEOS increased from 20 to 40 h. The quantum yield (QY) of the yellow-orange emission (coming from the Mn(2+) ions (4)T1-(6)A1 transition) for the ZnS:Mn(2+)(3 %) QDs and ZnS:Mn(2+)(3 %) QDs@SiO2 (when t = 40 h) nanocomposites was measured to be 34.5 and 22.4 %, respectively. All samples showed no significant cytotoxicity against the HeLa cells even at a high concentration of 500 μg/ml after incubation for 24 h. The red fluorescence can be observed in the cytoplasm of the HeLa cell, further proving its biolabeling applications.