Monodisperse ZnS nanocrystals (d = 1.7 – 10.0 nm) are synthesized from zinc carboxylates and N,N’-disubstituted, N,N’,N’-trisubstituted and N,N,N’N’-tetrasubstituted thioureas. The influence of precursor substitution, reaction temperature and initial Zn:S ratio on the final nanocrystal size were evaluated. By using saturated hydrocarbon solvents and saturated aliphatic carboxylate ligands, polymeric byproducts could be avoided and pure ZnS nanocrystals isolated. High temperatures, slower precursor conversion reactivity and branched zinc 2-hexyldecanoate yield the largest ZnS nanocrystals. Ensuring the purity of zinc carboxylate, and optimizing precursor selection and reaction times leads to the narrowest shape dispersity. Specifically, inclusion of small anions leads to the formation of anisotropic nanocrystals. Using X-ray scattering and scanning transmission electron microscopy, an empirical relationship between the nanocrystal size and the energy of the first exciton transition is extracted. Further, we demonstrate how these methods can be adapted to synthesize more complex II-VI and III-V heterostructures.

Synthesis and characterization of monodisperse ZnS nanocrystals

ACS Spring Meeting 2021

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