One-pot Synthesis of CdS Quantum Dots and Their Quantum Yields

CdS quantum dots(QDs) were synthesized via one-pot method, with Octadecene as the solvent and oleic acid as capping ligands. The influences of reaction time, reaction temperature and Cd/S molar ratio on optical properties of CdS QDs were studied. The zinc-blende, monodisperse and high-crystalline structures of CdS QDs were characterized by XRD and HRTEM. The good monodisperse size distribution and optical properties were also confirmed by UV-Vis and PL spectra. The PL spectra are symmetrical and their full-width at half-maximum(FWHM) is samll. The first absorption peak is very sharp. The growth temperature and the initial Cd/S molar ratio have important influences on the size and photoluminescence quantum yields(PLQY) of CdS QDs. It has been demonstrated that high photoluminescence quantum yields with nearly monodisperse CdS nanocrystals can be obtained by a judicious choice of the Cd/S molar ratio(3:1) and the growth temperature (240 degrees C), and the PLQY is about 30%.