Preparation of poly(ethylene glycol) methacrylate coated CuInS ₂/ZnS quantum dots and their use in cell staining

A simple synthesis of poly(ethylene glycol) methacrylate (PEGMA) coated CuInS ₂/ZnS quantum dots (QDs) has been developed. X-ray diffraction, transmission electron microscopy, and atomic force microscopy observations demonstrated that uniform CuInS ₂/ZnS QDs were successfully prepared. Fourier transform infrared spectroscopy indicated no new peak after the coating process, indicating that only physical interactions occurred during coating and that PEGMA did not disturb the crystal structure of the CuInS ₂/ZnS QDs. After PEGMA coating, the photoluminescence spectra of the CuInS ₂/ZnS QDs red shifted (from 566 nm to 589 nm) and the QD particle size increased. The concentration and molecular weight of PEGMA play important roles in the water solubility and hydrodynamics of the particles. The PEGMA-coated CuInS ₂/ZnS QDs showed stable emissions for up to 3 weeks. As a demonstration of a potential biomedical application, PEGMA-coated CuInS ₂-ZnS QDs were used in labeling human liver carcinoma (HepG2) tumor cells.