Facile One-Step Synthesis and Transformation of Cu(I)-Doped
Zinc Sulfide Nanocrystals
to Cu<sub>1.94</sub>S–ZnS Heterostructured Nanocrystals
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Abstract
A facile one-pot heating process
without any injection has been
developed to synthesize different Cu–Zn–S-based nanocrystals.
The composition of the products evolves from Cu(I)-doped ZnS (ZnS:Cu(I))
nanocrystals into heterostructured nanocrystals consisting of monoclinic
Cu<sub>1.94</sub>S and wurtzite ZnS just by controlling the molar
ratios of zinc acetylacetonate (Zn(acac)<sub>2</sub>) to copper acetylacetonate
(Cu(acac)<sub>2</sub>) in the mixture of <i>n</i>-dodecanethiol
(DDT) and 1-octadecene (ODE). Accompanying the composition transformation,
the crystal phase of ZnS is changed from cubic zinc blende to hexagonal
wurtzite. Depending on the synthetic parameters including the reaction
time, temperature, and the feeding ratios of Zn/Cu precursors, the
morphology of the as-obtained heterostructured nanocrystals can be
controlled in the forms of taper-like, matchstick-like, tadpole-like,
or rod-like. Interestingly, when the molar ratio of Cu(acac)<sub>2</sub> to Zn(acac)<sub>2</sub> is increased to 9:1, the crystal phase of
the products is transformed from monoclinic Cu<sub>1.94</sub>S to
the mixed phase composed of cubic Cu<sub>1.8</sub>S and tetragonal
Cu<sub>1.81</sub>S as the reaction time is further prolonged. The
crystal-phase transformation results in the morphological change from
quasi-spherical to rice shape due to the incorporation of Zn ions
into the Cu<sub>1.94</sub>S matrix. This method provides a simple
but highly reproducible approach for synthesis of Cu(I)-doped nanocrystals
and heterostructured nanocrystals, which are potentially useful in
the fabrication of optoelectronic devices
