Silica-Coated S2–-Enriched Manganese-Doped ZnS Quantum Dots as a Photoluminescence Probe for Imaging Intracellular Zn2+ Ions

Detection of intracellular Zn2+ has gained great attention because of its biological significances. Here we show the fabrication of silica-coated S2–-enriched Mn-doped ZnS quantum dots (SiO2–S–Mn–ZnS QDs) by enriching S2– with a silica shell on the surface of Mn-doped ZnS QDs via a sol–gel process for imaging intracellular Zn2+ ions. The developed probe gave a good linearity for the calibration plot (the recovered PL intensity of the SiO2–S–Mn–ZnS QDs against the concentration of Zn2+ from 0.3 to 15.0 μM), excellent reproducibility (1.2% relative standard deviation for 11 replicate measurements of Zn2+ at 3 μM), and low detection limit (3s; 80 nM Zn2+). The SiO2–S–Mn–ZnS QDs showed negligible cytotoxicity, good sensitivity, and selectivity for Zn2+ in a photoluminescence turn-on mode, being a promising probe for photoluminescence imaging of intracellular Zn2+.