Transition metal dichalcogenides (TMDs) exist in a multitude of phases, each with a unique electronic structure, making them attractive candidates for a variety of applications. The development of solution-phase routes to TMDs is gaining attention due to the potential to realize scalable syntheses that require relatively mild conditions. Colloidal chemistry relies on the modulation of time, temperature, ligand identity, and precursor reactivity to control the size, shape and phase of the nanocrystals. Using WSe2 as a model system, we find that the reactivity of the tungsten precursor can be tuned by changing the composition of ligands in the reaction. Specifically, the tungsten precursor (W(CO)6) was heated in either a strongly coordinating solvent (oleic acid) or a weakly coordinating solvent (oleyamine or trioctylphosphine oxide), followed by swift injection of Ph2Se2. We find that strongly coordinating solvents lead to large nanocrystals with the 1T’ phase, whereas weakly coordinating solvents yield small particles with mixed 2H/1T phase. This modulation of the reactivity of the tungsten precursor can be further exploited to synthesize one-pot heterostructures of Ni3Se4 or Cu2WSe4 core nanocrystals shelled with WSe2. Our results demonstrate the promise of colloidal synthesis to realize facile, scalable, solution-phase routes to tunable or multifunctional nanostructures.

Modulation of tungsten precursor reactivity for control over size and phase of WSe2 nanocrystals

2019 Fall National Meeting

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