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

Abstract

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(<i>n</i>-octylamine)₁₆(di-<i>n</i>-pentylamine)₂], which is proposed to function as crystal nuclei that may be stored in a bottle.