Marty W. DeGroot

Molecular nanocluster analogues of CdSe/ZnSe and CdTe/ZnTe core/shell nanoparticles

The ternary II–II′–VI nanoclusters [(N,N′-tmeda)5Zn5Cd11E13(EPh)6(thf)n] (1, E = Se, n = 2; 2, E = Te, n = 1) have been synthesized by the reaction of bis(trimethylsilylchalcogenolate)zinc(II) complexes in the presence of PhESiMe3 and solubilizing phosphine ligands. Structural characterization of the complexes by X-ray crystallography revealed that the clusters consist of CdE cores whose surfaces are stabilized by [(N,N′-tmeda)5ZnE2] units, and hence can be described as molecular analogues of core/shell nanoparticles. The optical properties of the clusters exhibit the effects of quantum confinement and are luminescent at room temperature with emission occurring near the absorption edge. Solid-state thermal decomposition of 1 and 2 results in the formation of ternary ZnCdE materials with the same metal stoichiometry as the cluster precursors.

A molecular precursor approach for the synthesis of composition-controlled ZnxCd1−xS and ZnxCd1−xSe nanoparticles

Ternary ZnxCd1−xS and ZnxCd1−xSe nanoparticles have been synthesized using a low temperature molecular precursor approach. The co-injection of silylated metal chalcogenolate complexes [(N,N′-TMEDA)Zn(ESiMe3)2] (E = S, 1; E = Se, 2) and [(N,N′-TMEDA)Cd(ESiMe3)2] (E = S, 3; E = Se, 4) to solutions of (N,N′-TMEDA)M(OAc)2 (M = Zn, Cd) in THF resulted in the formation of nanocrystalline quantum dots with particle sizes in the 2–3 nm range. Nanoparticles with Zn mole fractions (x) ranging from 0.95 to 0.05 can be achieved via manipulation of the reaction stoichiometry of 1(2) and 3(4). The size uniformity of the ternary nanoparticles permits control of the absorption properties by changing the metal ion composition. UV-visible and NMR spectroscopy, thermogravimetric analysis as well as X-ray and electron diffraction studies provide substantial evidence that the Zn(II) and Cd(II) ions are homogeneously mixed both within the cores of the nanoparticles and at the particle surfaces. Further control of the optical properties of the ternary materials was achieved via the growth of the particles in hot hexadecylamine while maintaining the Zn/Cd ratio.

Polynuclear bismuth selenolates: rings en route to clusters

BiBr3 reacts with the silylated selenium reagent Se(Ph)SiMe3 in the presence of tertiary phosphines to yield polynuclear bismuth selenolate complexes that contain both terminal and bridging Se(Ph) ligands.