Formation of ZnS Cubes and Quantum Dots and Structural Feature for Improved Quantum Dot Emission

Zinc blende-phased zinc sulfide cubes with tunable sizes of 200-370 nm have been synthesized together with an extensive growth of 5-10 nm ZnS quantum nanostructures. Their band gaps red-shift slightly with increasing cube sizes. Lattice imperfection is commonly observed in quantum dots, but its relation to emission intensity is less explored. Thus, another interesting goal of this work is to investigate the structural feature for bright light emission from quantum dots. Using another condition to grow ZnS quantum dots in an icy water bath first, and heat the particles to 100-200 °C, possibly lattice defect- or trap state-related emission intensities increase considerably for the 150 and 200 °C samples. The heat-treated samples exhibit notable and progressive decreases in the lattice constant. Transmission electron microscopy-derived lattice point images reveal significant lattice deviations in these samples, verifying the link between heat-induced lattice perturbation and enhanced light emission from quantum dots.