The development of solution-phase routes to transition metal dichalcogenides is gaining attention due to the potential to realize scalable syntheses that require relatively mild conditions. Colloidal nanocrystal syntheses offer facile control of properties such as size, shape, phase and dopant/defect incorporation by tuning of easily modulated parameters such as time, temperature, ligand identity and precursor reactivity. Here, we show that control over that size and phase of colloidal WSe2 nanocrystals is achieved by careful choice of ligand, where increasing the coordinating strength of ligands present during synthesis favors larger nanocrystals with the 1T′ phase. Specifically, oleic acid is used to coordinate W in solution, slowing down the W reactivity and yielding large 1T′ WSe2 nanocrystals. We can further exploit this modulation of the reactivity to enable one-pot synthesis of colloidal core/shell heterostructured nanocrystals. The core nanocrystals can subsequently be removed by soaking in ethylene diamine and trioctylphosphine, allowing easy access to hollow WSe2 nanocrystals. Overall, these syntheses allow access to heterostructured or hollow nanostructures in just one or two steps and demonstrate a synthetic strategy to ultimately enable facile, solution-phase syntheses of exotic nanostructures.

Modulation of precursor reactivity in colloidal syntheses of WSe2-based nanostructures

2019 Fall National Meeting

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