A selenide is a chemical compound containing a
selenium
Selenium is a chemical element with the symbol Se and atomic number 34. It is a nonmetal (more rarely considered a metalloid) with properties that are intermediate between the elements above and below in the periodic table, sulfur and telluriu ...
anion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...
with
oxidation number
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. ...
of −2 (Se
2−), much as
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
does in a
sulfide
Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds l ...
. The chemistry of the selenides and sulfides is similar. Similar to
sulfide
Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds l ...
, in
aqueous solution
An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would ...
, the selenide ion, Se
2−, is prevalent only in very basic conditions. In neutral conditions, hydrogen selenide
ion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
, HSe
−, is most common. In acid conditions,
hydrogen selenide
Hydrogen selenide is an inorganic compound with the formula H2Se. This hydrogen chalcogenide is the simplest and most commonly encountered hydride of selenium. H2Se is a colorless, flammable gas under standard conditions. It is the most toxic sele ...
, H
2Se, is formed.
Some selenides are reactive to oxidation by air. Owing to the greater reducing power of selenide, metal selenides are more easily decomposed to the elements than are
sulfide
Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds l ...
s (
tellurides are even more labile). Selenides of electropositive metals: such as aluminium selenide readily hydrolyse, even in moist air, evolving toxic hydrogen selenide gas.
Pure
selenide minerals are rare, instead selenium tends to partially
substitute for sulfide in many
sulfide mineral
The sulfide minerals are a class of minerals containing sulfide (S2−) or disulfide (S22−) as the major anion. Some sulfide minerals are economically important as metal ores. The sulfide class also includes the selenides, the tellurides ...
s. The degree of substitution is only of commercial interest for copper sulfide ores, in which case selenium is recovered as a by-product of copper refining. Some selenide minerals include
ferroselite
Orthorhombic ferroselite and its isometric polymorph dzharkenite are iron selenides of general formula FeSe2 precipitated under reducing conditions in anoxic environments. They are a source of selenium in the Rocky Mountains where selenium occurr ...
and
umangite
Umangite is a copper selenide mineral, Cu3 Se2, discovered in 1891. It occurs only in small grains or fine granular aggregates with other copper minerals of the sulfide group. It has a hardness of 3. It is blue-black to red-violet in color with ...
.
[Bernd E. Langner "Selenium and Selenium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. .]
Reactions
Alkali metal selenides react with elemental selenium to give salts of
polyselenide.
Quantum dots
Metal selenide
quantum dot
Quantum dots (QDs) are semiconductor particles a few nanometres in size, having optical and electronic properties that differ from those of larger particles as a result of quantum mechanics. They are a central topic in nanotechnology. When the q ...
s and nanoparticles can be prepared by a variety of synthetic methods, many of which require high temperatures and hazardous precursor compounds.
The particles can be adapted for a variety of applications by varying the ligands coordinated to the positively-charged outer layer. Many ligand-exchange reactions are available for use, trading X, L, and Z-type ligands, the mechanism for which is still under study.
Applications
Quantum dots based on metal selenides have been extensively for their distinctive spectral properties. Core-shell alloys of cadmium sulfide and selenide are of interest in imaging and
phototherapy
Light therapy, also called phototherapy or bright light therapy is intentional daily exposure to direct sunlight or similar-intensity artificial light in order to treat medical disorders, especially seasonal affective disorder (SAD) and circadi ...
.
Examples
*
Gallium(II) selenide
Gallium(II) selenide ( Ga Se) is a chemical compound. It has a hexagonal layer structure, similar to that of GaS. It is a photoconductor, a second harmonic generation crystal in nonlinear optics, and has been used as a far-infrared conversion mat ...
*
Indium(III) selenide
Indium(III) selenide is a compound of indium and selenium. It has potential for use in photovoltaic devices and it has been the subject of extensive research. The two most common phases, α and β, have a layered structure, while γ is a "defect w ...
*
Sodium selenide
*
Cadmium selenide
Cadmium selenide is an inorganic compound with the formula Cd Se. It is a black to red-black solid that is classified as a II-VI semiconductor of the n-type. Much of the current research on this compound is focused on its nanoparticles.
Stru ...
*
Zinc selenide
Zinc selenide (ZnSe) is a light-yellow, solid compound comprising zinc (Zn) and selenium (Se). It is an intrinsic semiconductor with a band gap of about 2.70 eV at . ZnSe rarely occurs in nature, and is found in the mineral that was named af ...
*
Lead selenide
*
Copper selenide
Copper selenide is an inorganic binary compound consisting of copper and selenium. Its formula is sometimes described as CuSe or Cu2Se.
The crystalline structure and electronic behavior is determined by its elemental composition. Stoichiometric c ...
See also
*
Sulfoselenide
References
External links
Selenide Nanoparticles Used In Solar Energy Conversion
{{Selenides
Chalcogenides
Solar cells
Selenium(−II) compounds