Ultraviolet optical properties of ZnS quantum-dots synthesized in ethanol

We investigated the UV optical properties of 2.2 to 2.5 nm colloidal ZnS quantum dots (QDs) that were synthesized using a one-step solution-processed method. X-ray diffraction patterns and transmission electron microscopy images show clear cubic zinc-blende ZnS structure. Photoluminescence results show defect-related light emission with a peak wavelength that can be tuned from 400 to 389 nm by changing the particle size of the ZnS QDs. As judged from absorption spectroscopy, the optical bandgaps of the QD suspensions then change from 4.0 to 4.2 eV and for the QD films from 3.9 to 4.0 eV, showing clear quantum confinement. The excitation spectra show excitation maxima at the exciton energy, changing from 3.89 eV (319 nm) down to 4.07 eV (305 nm).