Investigating The Influence of Multivalent Transition Metal Dopants and Capping Ligands on The Lateral Growth of Photo-Optical Cu₂MoS₄ 2D Nanostructures Using a Colloidal Method

2D transition metal dichalcogenides (TMDs) is a class of emerging materials due to their unique and unconventional properties which allows them to have a cohort of applications such as for photovoltaics and photoelectrochemical conversion. Of these, ternary TMDs are underexplored and herein, for the first-time metal-doped layered tetragonal copper molybdenum sulfide (CMS) nanostructures using a facile, economically feasible and inexpensive colloidal hot injection method were grown at relatively low temperatures of 100 and 140^oC and short time of 1 hour. The morphology, structure, and optical properties of the nanostructures were analyzed by powder X-ray diffraction, high resolution transmission electron microscopy with energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, UV-VIS absorption, steady-state and time-resolved and photoluminescence spectroscopy. We demonstrate that colloidal conditions involving fractions of oleic acid in combination with the main capping ligand oleylamine enable lateral growth of highly crystalline 2D CMS nanostructures as hexagonal shaped nanosheets and layered nanorods of approximate dimensions 17 nm and 69 nm respectively. In particular, metal doped nanostructures exhibit a correlation of metal ion fraction and particle morphology implicating impurity ions in lateral growth of high energy facets into larger domain 2D nanostructures. Overall, the data shows a correlation of structure, morphology, and stoichiometry on the optical properties such as the influence of point defects such as sulphur vacancies and dopant (Zn²⁺, Ni ²⁺, Mn ²⁺) substitutions and interstitials. Collectively, this study provides an avenue for the synthesis of ternary TMD 2D nanostructures primarily with shorter growth time and lower growth temperature and offer the opportunity to simply tailor the reaction conditions to afford materials with tunable properties for photovoltaic applications. Additional elements of the work entail examination of the dynamics of the growth of the 2D nanostructures using <i>insitu</i> X-ray characterization such as pair distribution function, small and wide-angle x-ray scattering and x-ray absorption spectroscopy to determine the influence of precursors, capping ligands and growth conditions on preferred edge facets. Such insights will be useful towards pinpointing specific growth factors for more targeted growth of these types of 2D nanostructures.