Synthesis of tetragonal mackinawite-type FeS nanosheets by solvothermal crystallization

► 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.