An environmentally sensitive equilibrium morphology phase map of zinc sulphide nanoparticles

Zinc sulphide (ZnS) nanoparticles have promising applications in a diverse range of fields, including bio-technology; optoelectronics; catalysis; photovoltaics; gas, chemical and bio-sensors; field effect transistors; and field emitters. Like most modern nanomaterials, ZnS nanoparticles derive their utility from physical properties which can be ‘customised’ or ‘tuned’ for specific needs; however, there are considerable risks associated with the use of nanoscale ZnS, which exist as a direct consequence of the structure/property relationships from which their utility is derived. These risks include instability, adverse physical properties and elevated toxicity. In order to minimize exposure to these risks, ab inito calculations and a shape-dependent thermodynamic model were used to predict the equilibrium morphologies and phase transformations between the cubic, hexagonal and amorphous phases of ZnS as a function of size, temperature and pressure. The likelihood of a phase transformation occurring was fond to vary significantly, depending heavily on both size and shape. Further to this, thermodynamic conditions were identified which are expected to favour the formation of specific morphologies and encourage long-term stability in a broader environmental sense. These results show how tailoring the shape of a nanoparticle may ultimately determine its phase by encouraging or suppressing phase transformations, and provide insight into how experimental synthesis conditions can be modified to obtain synthesis objectives and maintain post-synthesis phase and morphological stability; outcomes which are critical for safe, stable and effective applications of this material.