Bis(hexylmethyldithio-/diselenocarbamato)cadmium(II)/zinc(II) (M(E 2 CNMe n Hex) 2 [M ) Zn, Cd; E ) S, Se]) have been used as single-source precursors for the preparation of TOPOcapped CdS, CdSe, ZnS, and ZnSe nanoparticles. The precursors are stable for long periods of time and pyrolyse cleanly to give high yields of nanocrystals. The nanoparticles were of high quality, close to monodispersed, and showed quantum confinement with characteristic close to band edge luminescence in their emission spectra. The broad diffraction in the XRD pattern and diffuse diffraction rings of the SAED pattern are typical of nanometric size particles. The TEM micrographs showed well-defined, close to spherical particles and the lattice fringes in the HRTEM images confirmed the crystalline nature. The presence of a strong phosphorus peak in the EDAX spectra is indicative of TOPO or TOPE (E ) S or Se) bound to the surface.

In this work, we report the synthesis of CdSe/CdS, CdSe/ZnS, and CdSe/ZnSe core/shell and CdSe/CdS alloy nanoparticles using bis(hexyl(methyl)dithio-/-diselenocarbamato)cadmium(II)/zinc(II) compounds as single-source precursors. We compare the optical properties of the core/shell nanoparticles in relation to those of the parent organically capped binary nanoparticles. We also compare the properties of CdSe alloys to those of the CdSe particles and core/shell structures. The absorption spectra of CdSe/CdS, CdSe/ZnS, and CdSe/ ZnSe show red shifts of 0.020, 0.038, and 0.046 eV, respectively, with respect to the parent CdSe nanoparticles. Photoluminescence spectra (λ exc ) 400 nm) CdSe/CdS (622 nm), CdSe/ ZnS (620 nm), and CdSe/ZnSe (617 nm) show emissions close to the absorption band edge. The emission maximum of the core/shell materials shows red shifts in relation to the emission maximum of CdSe consistent with the red shifts in the absorption spectra. The intensity of the emission maximum is considerably increased in the core/shell structure as compared to the parent materials. The X-ray diffraction pattern of the CdSe-CdS composite are broad and poorly defined. The HRTEM micrographs of the core/shell nanoparticles show welldefined, spherical particles with larger diameters than the particles of the parent material.

these compressive forces/unit volume decrease until they are insufficient to maintain the RS structure, and a phase transition to a mixture of ZB and WZ occurs. ExperimentalFilms of gold±metal alloys (with cadmium or palladium) were evaporated onto glass substrates at room temperature in a vacuum of 10 ±6 torr at a rate of 0.10 nm/s. The films were 35 nm thick, as measured with a quartz crystal oscillator. The alloys were prepared by melting weighed quantities of gold and the second metal together in a tungsten evaporation boat. A small amount of the alloy was evaporated onto a shutter covering the glass substrates before evaporating onto them. The alloy films on the substrates were subsequently annealed in air at 250 C for 3 h. The evaporated atomic compositions are 3 % Cd±Au, and up to 26 % Pd±Au.CdSe nanocrystals were epitaxially grown on the gold-alloy film substrates by electrochemical deposition. A two-electrode electrochemical cell was used to carry out the electrochemical deposition with the alloy film substrate as the cathode and a graphite rod as the anode in a solution of 50 mM Cd(ClO 4 ) 2´H2 O saturated with elemental Se (ca. 5 mM) in dimethyl sulfoxide. The plating was carried out in the constant current (galvanostatic) mode [6,7]. Electrodeposition was carried out using a constant current density of 0.1 mA cm ±2 for 8 s at a temperature of 110 C. Amounts of deposit are given as nominal thickness: this is the theoretical CdSe thickness expected from the deposition charge passed (based on Faraday's law and a two-electron transfer) assuming 100 % current efficiency and a homogeneous coverage. Since the coverage is usually not homogeneous, the nominal thickness provides a reasonable guide to the average thickness.High resolution TEM imaging was performed with a JEOL 4000EXII microscope, operating at 400 kV. Conventional TEM bright field and dark field imaging and selected area diffraction were carried out on a Phillips EM-400T microscope operating at 120 kV.Powder XRD spectra were recorded on a Rigaku RU-200B Rotaflex diffractometer operating in the Bragg configuration using Cu Ka radiation. The accelerating voltage was set at 50 kV with a 150 mA flux. Scatter and diffraction slits of 0.3 mm and a 0.5 mm collection slit were used.Raman spectroscopy was carried out at room temperature using a Renishaw Raman spectrometer equipped with a 633 nm He/Ne laser. The measurements were performed in the back-scattered geometry with a laser power of 2.5 mW focused to a spot of ca. 1 mm in diameter.

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