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.