Ripening Kinetics of CdSe/ZnSe Core/Shell Nanocrystals

Abstract

CdSe and CdSe/ZnSe core shell nanocrystals were prepared via the inverse micelle technology with TOP/TOPO/HDA surfactants, and their high crystallinity was confirmed by using X-ray diffraction (XRD) and\nhigh-resolution transmission electron microscopy (HRTEM) analyses. Ostwald ripening behavior of the\nnanocrystals was monitored by using the red-shift in UV−visible absorbance peaks, and their size variation\nwas estimated by employing a quantum confinement effect equation. Lifshitz−Slyozov−Wagner (LSW) kinetics\nanalyses were performed by using the size variation according to ripening temperature and time period.\nArrhenius-type plots were created by using the slopes of the LSW curves for the CdSe and CdSe/ZnSe\nnanocrystals, respectively, and the activation energy values for the ripening were evaluated for the nanocrystals.\nAt a low-temperature region, the CdSe and CdSe/ZnSe samples seem to show dissociation of Cd−Se and\nZn−Se surface atomic bonds, respectively, while at a high-temperature region above 266 °C, both samples\nseem to show active dissociation of both Cd−Se and Zn−Se lattice atomic bonds. The CdSe−ZnSe shows\nrelatively low activation energy for the ripening, compared to the bare CdSe possibly due to weak Zn−Se\natomic bonds. One can complete the Ostwald ripening kinetics equation by using two kinetics variables,\nderived in this study, for the estimation of the size of CdSe/ZnSe core/shell nanocrystals. Also, this approach\ncan be applied to ripening kinetics of other core/shell nanocrystal systems.