Colloidal Synthesis of Zirconium Disulphide Nanostructures and their Stability Against Oxidation

Abstract

The need to exploit the exotic properties of ZrS2 synthesized via colloidal means is imperative. For almost a decade now there has been no literature on the colloidal synthesis of ZrS2 nanomaterials. Meanwhile, several publications are available on other methods of synthesis mostly chemical vapour transport (CVT) and chemical vapour deposition (CVD). The synthesized bulk material from the CVT method is further subjected to exfoliation (mechanical or liquid) to obtain mono or few-layers of ZrS2. With the colloidal method, there is a possibility of the oxide being formed during the synthesis of ZrS2 and likely destabilization of the nanomaterial after synthesis on exposure to ambient environment. In this study, both the heat up and hot injection methods were employed to fabricate various morphologies of ZrS2 nanomaterials. The metal and sulphur precursors were dissolved in a mixture of octadecene (ODE) and oleic acid (OA); and refluxed at a temperature of 290 °C in the presence of nitrogen gas. ODE served the role of non-coordinating solvent, while OA served as the capping agent. Nanorods, nanospheres and nanosheets were obtained from the heat up method. Meanwhile, the hot injection approach produced nanosheets and nanospheres with well noticeable hollow centres. Powder X-ray diffractometer (PXRD) validated the formation of the ZrS2 hexagonal phase with traces of oxides of zirconium, ZrO2. The peak of S2p was conspicuously absent while the Zr3d peak was well noticeable in the XPS spectra. XPS and EDS measurements confirmed the replacement of the sulphur atom by the O atom on the surface of the nanomaterials. Only one exciton peak was observed for the absorption spectra from both the heat up and hot injection methods; and thermal thermogravimetry analysis (TGA) revealed three plateaux of decomposition of the nanomaterials.