Nanostructure of Cd_xZn_1-xSe heterogeneous nanorods

Growth of nanorods with a large bandgap core (zinc selenite or ZnSe) and a small bandgap shell (cadmium selenite or CdSe) was attempted. The resulting nanopowders were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), photoluminescence (PL) and UV-vis absorption. It was found that the ZnSe core was not uniformly covered by CdSe. Instead, the nanorods resulted from self-assembly of prolate nanospheres by aligned attachment. The PL from the pure ZnSe exhibited some small quantum confinement red shifting for short growth times, but the emission peak stabilized at 440 nm after growth for longer than 2 h at 280 C. When Cd precursors were added to grow CdSe, the PL emission peak red-shifted to wavelengths greater than 600 nm, and up to 660 nm. TEM data showed nonuniform diffraction along the nanorod and XRD showed formation of a ternary compound with an average stoichiometry of Cd _0.2Zn_0.8Se. These data are only consistent with inhomogeneous nanorods, and a schematic representation of inhomogeneities is presented.