Understanding the role of zinc dithiocarbamate complexes as single source precursors to ZnS nanomaterials.

Zinc sulfide is an important wide-band gap semi-conductor and dithiocarbamate complexes [Zn(SCNR)] find widespread use as single-source precursors for the controlled synthesis of ZnS nanoparticulate modifications. Decomposition of [Zn(SCNBu)] in oleylamine gives high aspect ratio wurtzite nanowires, the average length of which was increased upon addition of thiuram disulfide to the decomposition mixture. To provide further insight into the decomposition process, X-ray absorption spectroscopy (XAS) of [Zn(SCNMe)] was performed in the solid-state, in non-coordinating xylene and in oleylamine. In the solid-state, dimeric [Zn(SCNMe)] was characterised in accord with the single crystal X-ray structure, while in xylene this breaks down into tetrahedral monomers. XAS in oleylamine (RNH) shows that the coordination sphere is further modified, amine binding to give five-coordinate [Zn(SCNMe)(RNH)]. This species is stable to 70 °C, above which amine dissociates and at 90 °C decomposition occurs to generate ZnS. The relatively low temperature onset of nanoparticle formation is associated with amine-exchange leading to the formation of [Zn(SCNMe)(SCNHR)] which has a low temperature decomposition pathway. Combining these observations with the previous work of others allows us to propose a detailed mechanistic scheme for the overall process.