|IUPAC name||Copper(I) oxide|
|Other names||Cuprous oxide|
Red copper oxide
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|Molar mass||143.09 g/mol|
|Density||6.0 g/cm3, solid|
|R/S statement||R: 22|
|Except where noted otherwise, data are given for|
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references
Copper(I) oxide or cuprous oxide (Cu2O) is an oxide of copper. It is insoluble in water and organic solvents. Copper(I) oxide dissolves in concentrated ammonia solution to form the colourless complex[Cu(NH3)2]+, which easily oxidizes in air to the blue[Cu(NH3)4(H2O)2]2+. It dissolves in hydrochloric acid to form HCuCl2 (a complex of CuCl), while dilute sulfuric acid and nitric acid produce copper(II) sulfate and copper(II) nitrate, respectively.
Copper(I) oxide is found as the mineral cuprite in some red-colored rocks. When it is exposed to oxygen, copper will naturally oxidize to copper(I) oxide, but this takes extensive periods of time. Artificial formation is usually accomplished at high temperature or at high oxygen pressure. With further heating, copper(I) oxide will form copper(II) oxide.
Applications as semiconductor
Copper(I) oxide shows four well understood series of excitons with resonance widths in the range of neV. The associated polaritons are also well understood; their group velocity turns out to be very low, almost down to the speed of sound. That means light moves almost as slow as sound in this medium. This results in high polariton densities, and effects like Bose-Einstein condensation, the dynamical Stark effect and phonoritons have been demonstrated.
Another extraordinary feature of the ground state excitons is that all primary scattering mechanisms are known quantitatively. Cu2O was the first substance where an entirely parameter-free model of absorption linewidth broadening by temperature could be established, allowing the corresponding absorption coefficient to be deduced. It can be shown using Cu2O that the Kramers-Krönig relations do not apply to polaritons.
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