Highly luminescent glutathione-capped ZnS : Mn/ZnS core/shell doped quantum dots for targeted mannosyl groups expression on the cell surface

High-quality glutathione (GSH) capped ZnS : Mn/ZnS core/shell doped quantum dots (d-dots) with pure dopant emission band and excellent stability have been synthesized directly in aqueous media. The influences of experimental variables on the luminescent properties of the ZnS : Mn/ZnS nanocrystals have been investigated. The quantum yield of the dopant Mn photoluminescence in the as-prepared ZnS : Mn/ZnS core/shell d-dots can be up to 27.4%. The value is the highest reported to date for ZnS : Mn d-dots via the direct aqueous synthetic method. Their optical features and structure have been characterized by UV-Visible spectroscopy, photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) in detail. Additionally, the stability study against UV irradiation indicated that the obtained d-dots possess excellent photostability. Furthermore, the MTT assay demonstrated that the ZnS : Mn QDs do not exhibit any cytotoxicity toward HeLa cells up to a concentration of 600 μg mL−1. Using the Con A-mannose recognition system as a model, Con A functionalized ZnS : Mn/ZnS nanocrystals were prepared and successfully used for targeted mannosyl groups expression on the HeLa cells surface. Our investigation clearly shows that the GSH capped ZnS : Mn QDs are promising candidates as biological fluorescent labels.