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 [001] direction, are irregularly faceted with edge lengths that range from 100nm to over 1μm and average thicknesses of approx. 30nm. The samples showed a ferromagnetic background signal with no evidence of superconductivity. Single-crystal colloidal nanosheets of mackinawite-type FeS were synthesized by the solvothermal crystallization of an amorphous Fe–S precursor. [Display omitted] ► Aqueous co-precipitation yields an amorphous Fe–S precursor. ► The amorphous precursor solvothermally crystallizes to form metastable mackinawite. ► Mackinawite-type FeS forms as single crystal colloidal nanosheets. ► Samples are ferromagnetic with no evidence of superconductivity.