Synthesis and anisotropic growth of metastable wurtzite cuins 2 nanostructures Aoife Kavanagh 1 , Finn Purcell Milton 2 , Yurii Gun’ko 1 Trinity College Dublin, Ireland, 2 Technological University Dublin, Ireland Colloidal semiconductor nanomaterials have become a topic of extensive scientific research in the last several decades, due to their unique size- and shape-dependent properties, with applications ranging from energy devices to biomedical imaging. Currently, semiconductor nanomaterial research is dominated by binary systems containing toxic heavy metals such as cadmium and lead. However, recently, ternary I-III-VI type systems have emerged as promising alternatives to these toxic heavy-metal containing systems. I-III-VI systems, such as CuInS 2 , offer a number of distinct advantages over the existing binary heavy-metal based systems, such as greater tunability, large Stokes shifts and enhanced stability. While the shape dependent properties of the existing binary systems have been established, with the synthesis of anisotropic Cd-based binary systems widely reported, anisotropic ternary systems have been much less explored in the literature, with reports of CuInS 2 dominated by small, spherical particles with the thermodynamically stable chalcopyrite phase. Herein we report the synthesis and anisotropic growth of metastable wurtzite CuInS 2 nanostructures with a unique tapered hexagonal prismatic structure, the morphology and aspect ratio of which can be tuned by varying the sulfur source and co-ligand. These structures exhibit a broad absorption range and quantum confined bandgap. Quaternary CuInZnS nanostructures with a blue-shifted band gap were also produced. Transmission Electron microscopy (TEM), X-Ray Diffraction (XRD) and Energy dispersive X-ray spectroscopy (EDX) were employed to study the morphology, crystal phase and composition of the nanostructures. By monitoring these over reaction time, it was found that uniform hexagonal rods form first, which then grow anisotropically, resulting in a unique tapered hexagonal prismatic structure. These broad absorption CuInS 2 nanostructures have potential application in photovoltaic cells, while the study of the anisotropic growth can contribute to further development of new anisotropic I-III-VI type colloidal semiconductor nanomaterials and their applications. References 1. Bai, X.; Purcell-Milton, F.; Gun’ko, Y. K. Nanomaterials 2019, 9 (1), 85. DOI:10.3390/nano9010085. 2. Ning, J.; Kershaw, S. V.; Rogach, A. L. Nanomaterials 2019, 9 (12), 1779, DOI:10.3390/nano9121779.
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