Water-soluble silica-coated ZnS : Mn nanoparticles as fluorescent sensors for the detection of ultratrace copper(ii) ions in seawater

Abstract

Quantum dots (QDs), semiconductor particles with all three dimensions confined to the nanometer length scale, are good choices for the detection of heavy metals in aqueous media. In this study, silica-coated ZnS : Mn nanoparticles (ZnS : Mn/SiO₂) were synthesized by coating hydrophobic ZnS : Mn nanoparticles with silica shells through a microemulsion method. The ZnS : Mn/SiO₂ QDs exhibited satisfying dispersibility and luminescence properties in seawater. After a series of experiments were conducted in real seawater, the ZnS : Mn/SiO₂ QDs were proven to be sensitive and selective for Cu²⁺ detection. The quenching of the fluorescence of the QDs with the addition of Cu²⁺ is well described by the Stern–Volmer pattern. The detection of Cu²⁺ concentrations in seawater can be achieved over a linear range from 8.16 × 10⁻⁸ to 4.96 × 10⁻⁴ mol L⁻¹. Studies show that ZnS : Mn/SiO₂ QDs have great potential to be used as sensors for Cu²⁺ analysis from low to high concentrations in seawater.