Synthesis of tetragonal mackinawite-type FeS nanosheets by solvothermal crystallization

Mackinawite, a metastable 1:1 compound of iron and sulfur that adopts an anti-PbO-type structure, is of interest because of its relationship to known iron chalcogenide superconductors, as well as its biogeochemical relevance. Colloidal nanosheets of mackinawite-type FeS were synthesized by first generating an amorphous Fe–S precursor via the aqueous room-temperature co-precipitation of Fe2+ and S2−, then solvothermally crystallizing it in ethylene glycol at 200 °C in an autoclave. The product is highly crystalline, with lattice constants of a=3.674(3) Å and c=5.0354(3) Å. The nanosheets, with their surface normal oriented along the [0 0 1] direction, are irregularly faceted with edge lengths that range from 100 nm to over 1 μm and average thicknesses of approx. 30 nm. The samples showed a ferromagnetic background signal with no evidence of superconductivity.