Selenide

Selenide is a chemical compound that contains selenium in the -2 oxidation state with the formula Se^2-. It is an anion, making it a negatively charged ion, and is commonly found in various compounds, including those with metals where it forms metal selenides. These compounds are analogous to sulfides, which contain sulfur in place of selenium. Selenides are of significant interest in both the field of inorganic chemistry and various industrial applications, including the production of photovoltaic cells, semiconductors, and as catalysts in chemical reactions.

Properties

Selenides share many properties with sulfides, including their methods of preparation and their chemical behavior. However, selenides are generally more reactive than sulfides. They can be formed by the direct reaction of selenium with metals or by the reaction of selenium with metal salts in the presence of a reducing agent. In aqueous solution, selenides can hydrolyze, releasing hydrogen selenide (H₂Se), a highly toxic and unpleasant-smelling gas.

Preparation

The preparation of selenides typically involves the direct reaction of elemental selenium with a metal. For example, the reaction of selenium with aluminum can produce aluminum selenide:

\[ 2 \, \text{Al} + 3 \, \text{Se} \rightarrow \text{Al}_2\text{Se}_3 \]

Alternatively, selenides can be synthesized by reacting hydrogen selenide (H₂Se) with metal salts in solution. This method allows for the preparation of a wide range of selenide compounds.

Applications

Photovoltaics

Metal selenides, such as cadmium selenide (CdSe) and copper indium gallium selenide (CIGS), are used in the manufacture of thin-film solar cells. These materials have suitable band gaps and absorb sunlight efficiently, making them excellent choices for photovoltaic applications.

Semiconductors

Selenides are also used in the production of semiconductor materials. For example, zinc selenide (ZnSe) is used in the manufacture of light-emitting diodes (LEDs), laser diodes, and other optoelectronic devices.

Catalysis

Some selenide compounds serve as catalysts in organic synthesis, facilitating various chemical reactions. Their catalytic properties can be attributed to the unique electronic characteristics of selenium.

Health and Safety

Selenides, particularly hydrogen selenide (H₂Se), are toxic and require careful handling. Exposure to selenide compounds can lead to selenium poisoning, with symptoms including nausea, vomiting, and neurological effects. It is important to follow appropriate safety protocols when working with these substances to minimize exposure and prevent adverse health effects.

See Also

• Selenium
• Sulfide
• Photovoltaic cell
• Semiconductor
• Catalysis