metalchalcogen

Metal chalcogenides are compounds formed between a metal and a chalcogen, an element from group 16 of the periodic table (oxygen, sulfur, selenium, tellurium, or polonium). The term covers a broad range of materials, including binary sulfides, selenides, tellurides, and oxides, as well as more complex chalcogenides with mixed metals and multiple chalcogen atoms.

Structurally, metal chalcogenides show great diversity. Binary chalcogenides such as MX (M a metal; X a chalcogen) feature a variety of bonding regimes. The transition metal dichalcogenides, MX2 (for example MoS2, WS2), form layered, two‑dimensional sheets held together by van der Waals forces and can be exfoliated into few‑layer or monolayer crystals. Other structures include rock‑salt, zinc blende, pyrite, and various layered or three‑dimensional frameworks, depending on the specific metal and chalcogen.

Electronic properties span a wide range, from insulators and semiconductors to metals and, in some cases, superconductors. Layered chalcogenides often exhibit tunable electronic, optical, and catalytic properties that depend on composition, stoichiometry, and structural form.

Synthesis methods are varied and include solid‑state reactions at high temperature, direct combination of elements, chalcogenization of oxides, chemical vapor transport, hydrothermal or solvothermal routes, and electrodeposition. Exfoliation and chemical intercalation techniques can produce few‑layer or single‑layer forms.

Applications of metal chalcogenides are broad. They are used in electronics and optoelectronics (transistors, photodetectors), catalysis (hydrogen evolution and CO2 reduction), energy storage (batteries and supercapacitors), thermoelectrics, and sensing. Ongoing research seeks new compositions and two‑dimensional forms with tailored properties.

Safety considerations vary by composition; some chalcogenides can release toxic gases on decomposition, and certain elements (such as polonium) are highly radioactive, requiring proper handling and disposal.