Multimodal Distribution of Quantum Confinement in Ripened CdSe Nanocrystals

We present three different prepn. methods for CdSe colloidal nanoparticles that, when carried out into the Ostwald ripening regime, lead to the development of complex spectral patterns resulting from the overlap of several distinct components corresponding to different kinds of nanoparticles coexisting in soln. Although several polyhedral shapes are present in the transmission electron microscopy images, the main spectral difference appears to be essentially due to different sizes. We explain the generation of different species with a mechanism implying a controlled etching of the initially spherical particles and their subsequent coalescence into larger particles. We suggest that the presence of water and oxygen in the chem. equil. may favor this process.