Deposition of zinc sulfide quantum dots from a single-source molecular precursor

Nanoparticles of ZnS capped with tri-n-octylphosphineoxide (TOPO) and close to monodispersed have been prepared by a single-source route using ethyl(d i-ethyldithiocarbamato)zinc(II) as a precursor. The nanoparticles obtained showed quantum size effects in their optical spectra, and the photoluminesc ence spectrum showed a broad emission that could be attributed to the surfa ce traps. A blue shift of 0.31 eV in relation to the bulk material was obse rved. The selected area electron diffraction, x-ray diffraction pattern and transmission electron microscopy showed the material to be of the zinc ble nd structure. The crystallinity of the material was also evident from high- resolution transmission electron microscopy, which gave well-defined images of nano-sized particles with clear lattice fringes and a spacing of approx imately 3 Angstrom, corresponding to the (111) planes of the cubic crystall ine ZnS phase and in the size range of 3.9-4.9 nm. The presence of strong p hosphorus peak in the energy dispersion analytical x-ray pattern, together with a shift in infrared band for P = O of TOPO showed that the particles w ere TOPO capped.