Aqueous Route to Biocompatible ZnSe:Mn/ZnO Core/Shell Quantum Dots Using 1-Thioglycerol As Stabilizer

Water-dispersible 1-thioglycerol-capped Mn-doped ZnSe quantum dots (QDs) were prepared in aqueous solution through the nucleation-doping method by using safe and low-cost inorganic salts as precursors. Influence of the Zn/Se ratio, precursors concentrations and reaction pH on the particle size, colloidal stability, and photoluminescence (PL) were investigated. Under optimal conditions, thioglycerol-capped ZnSe:Mn QDs with an average diameter of 3.5 nm and a PL quantum yield of 3.5% in water at neutral pH were produced. X-ray powder diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, UV-visible spectroscopy and spectrofluorometry have been used to characterize the crystal structure and the optical properties of the dots. Remarkable improvements of stability in biological medium and PL were achieved by introduction of a ZnO shell through basic hydrolysis of Zn(NO3)(2). ZnO was found to eliminate the surface-trap state from Mn2+-doped ZnSe cores and enhance their PL quantum yield to 12%. Growth inhibition tests showed that core/shell ZnSe:Mn/ZnO@TG QDs do not exhibit any cytotoxicity toward E. coli bacterial cells up to a concentration of 0.14 mg/mL, indicating that these nanocrystals can be considered as building blocks for the synthesis of bioprobes for cells and tissues imaging.