The Magic-Size Nanocluster (CdSe)_(34) as a Low-Temperature Nucleant for Cadmium Selenide Nanocrystals; Room-Temperature Growth of Crystalline Quantum Platelets

摘要

Reaction of Cd(OAc)2-2H2O and selenourea in primary-amine/secondary-amine cosolvent mixtures affords crystalline CdSe quantum platelets at room temperature. Their crystallinity is established by X-ray diffraction analysis (XRD), high-resolution transmission electron microscopy (TEM), and their sharp extinction and photoluminescence spectra. Reaction monitoring establishes the magic-size nanocluster (CdSe)_(34) to be a key intermediate in the growth process, which converts to CdSe quantum platelets by first-order kinetics with no induction period. The results are interpreted to indicate that the critical crystal-nucleus size for CdSe under these conditions is in the range of (CdSe)_(34) to (CdSe)_(68). The nanocluster is obtained in isolated form as [(CdSe)_(34)(n-octylamine)_(16)(di-w-pentylamine)2], which is proposed to function as crystal nuclei that may be stored in a bottle.