The iron sulfides are the most earth abundant naturally occurring metal sulfides with a wide range of properties and thereby applications. However, relative to other metal chalcogenides, the iron-sulfur system is poorly understood due to its complexity, as numerous phase variations arise from minimal changes in stoichiometry. We find that organosulfur precursor reactivity tunes the phase of iron sulfide nanocrystals phase between pyrite (FeS2), greigite (Fe3S4), and pyrrhotite (Fe1-XS) in a colloidal hot injection syntheses. DFT was used to show that sulfur rich phases were favored when the carbon-sulfur (C-S) bond strength was low in the dialkyl disulfides, alkyl thiols, and dialkyl disulfides (allyl, benzyl, t-butyl, and phenyl). FeS2 is of particular interest as a low-cost earth abundant semiconductor for photovoltaics. Of all the precursors used, only diallyl disulfide yielded FeS2, which is particularly noteworthy since as the crystal structure contains (S-S) 2- units. Raman spectroscopy indicated that FeS2 forms directly without an FeS intermediate, unlike most synthetic procedures to pyrite. Diallyl disulfide releases persulfide units due to the lower C-S bond strength over the S-S bond strengths and facile decomposition in the presence of amines in SN2’ mechanisms.

Phase-controlled synthesis of iron sulfide nanoparticles via sulfur precursor reactivity

254th National Meeting (2017)

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