One-pot hydrothermal synthesis of water-dispersible ZnS quantum dots modified with mercaptoacetic acid

•A facile one-pot hydrothermal method to synthesize ZnS(MAA) QDs.•Synthesis and in situ modification of ZnS(MAA) QDs in a single process.•Controllable ZnS(MAA) QD size in the range 4–10nm by varying the reaction time.•Excellent dispersibility of ZnS(MAA) QDs in water.•50% of the fluorescence signal intensity retained after storage for 6months. ZnS quantum dots (QDs) were prepared and modified in situ with mercaptoacetic acid (MAA) via a facile and environmentally friendly one-pot hydrothermal method. The resulting MAA-modified ZnS QDs (ZnS(MAA) QDs) demonstrated a cubic β-sphalerite structure, spherical morphology and controllable crystal size in the range of 4–10nm depending on the reaction time, as characterized by X-ray diffraction, transmission electron microscopy and high-resolution transmission electron microscopy methods. The optical properties were investigated by photoluminescence spectroscopy, which showed that the fluorescence intensity increased with reaction time. After storing for 6months, the fluorescence intensity of ZnS(MAA) QDs retained about 50% of its initial value without any peak shift.