Ripening kinetics of CdSe/ZnSe core/shell nanocrystals

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 high-resolution transmission electron microscopy (HRTEM) analyses. Ostwald ripening behavior of the nanocrystals was monitored by using the red-shift in UV-visible absorbance peaks, and their size variation was estimated by employing a quantum confinement effect equation. Lifshitz-Slyozov-Wagner (LSW) kinetics analyses were performed by using the size variation according to ripening temperature and time period. Arrhenius-type plots were created by using the slopes of the LSW curves for the CdSe and CdSe/ZnSe nanocrystals, respectively, and the activation energy values for the ripening were evaluated for the nanocrystals. At a low-temperature region, the CdSe and CdSe/ZnSe samples seem to show dissociation of Cd-Se and Zn-Se surface atomic bonds, respectively, while at a high-temperature region above 266°C, both samples seem to show active dissociation of both Cd-Se and Zn-Se lattice atomic bonds. The CdSe-ZnSe shows relatively low activation energy for the ripening, compared to the bare CdSe possibly due to weak Zn-Se atomic bonds. One can complete the Ostwald ripening kinetics equation by using two kinetics variables, derived in this study, for the estimation of the size of CdSe/ZnSe core/shell nanocrystals. Also, this approach can be applied to ripening kinetics of other core/shell nanocrystal systems.