metaldisulfide

Metal disulfide refers to chemical compounds with the general formula MS2, where M is a metal. They are part of the broader family of transition metal dichalcogenides (TMDs). In these materials, each metal atom is coordinated to six sulfur atoms, forming X-M-X layers separated by weak van der Waals forces; the sulfur atoms often pair to form S-S units within the layer, giving the chemical motif S2^2− in the lattice.

Common M include Mo, W, Ti, Nb, and Fe; the most studied examples are MoS2 and WS2. MoS2 in particular exists in several polytypes, notably 2H (hexagonal, trigonal prismatic M coordination) and 1T (tetragonal, octahedral). The 2H form is a semiconductor with a thickness-dependent bandgap (roughly 1.2 eV indirect in bulk to about 1.8–1.9 eV direct in a monolayer); 1T is metallic and can transform back to 2H under certain conditions.

Properties: layered structure yields ease of exfoliation into nanosheets with high surface area; many MS2 are chemically stable and can withstand moderate temperatures; electronic properties depend on composition, structure, and thickness.

Synthesis and occurrence: MS2 can be prepared by direct reaction of the metal with sulfur at high temperature, through chemical vapor deposition, or via hydrothermal/solvothermal methods for nanostructures. Naturally occurring examples include pyrite (FeS2) and vaesite (NiS2).

Applications: widely used as solid lubricants because of low interlayer shear; catalysts for hydrodesulfurization and hydrogen evolution reaction; potential in electronics, optoelectronics, and energy storage as 2D materials.

Safety: sulfur compounds can be irritants; some metal disulfides can pose hazards if inhaled or ingested, and powders can be reactive with oxidizers.