Synthetic control in bottom-up methods to control the crystalline phase is necessary to facilitate the next generations of nanocrystal-enabled technologies. The reactivity of the precursors is one method to control their kinetic conversion and trap metastable crystalline phases. In the synthesis of nanocrystalline iron sulfides, we tune the speed at which sulfur is released into the synthetic system using a library of substituted thioureas. Here we show that this approach can be employed to strategically seven different phases of iron sulfides, producing a comprehensive phase control diagram. The result is dependent on the specific solvent and ligand environments, and 1H NMR is used to identify any deleterious interactions with the sulfur precursors. Development of the precursor-reactivity approach to phase control will lead to phase-tunable bottom-up nanoparticle synthesis throughout the periodic table.

Substituted thioureas and the phase control of nanocrystalline iron sulfides

ACS Fall 2021

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