Effects of Na+ ions on fluorescence properties of ZnSe quantum dots synthesized in an aqueous system

The ZnSe quantum dots (QDs) were synthesized in an aqueous system by introducing excess Na+ ions, which were characterized by Photoluminescence (PL), PL decay curves, UV-Vis absorption spectrum (ABs), X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). The results indicate that the particle size of ZnSe QDs were about 4 nm when Na+ ions were present in excess, which was bigger than that of ZnSe QDs (about 2 nm) synthesized in the solution without Na+ ions. An unexpected emission peak around 590 nm was observed when the concentration of Na+ ions was high enough in the reaction solution. This emission peak could be attributed to the selenium vacancies (SVs).