Copper(I) oxide

Copper(I) oxide
IUPAC name

Copper(I) oxide
Other names

Cuprous oxide
Dicopper oxide
Cuprite
Red copper oxide
Identifiers
CAS number 1317-39-1 Y
PubChem 10313194
ChemSpider 8488659 Y
UNII T8BEA5064F Y
EC number 215-270-7
KEGG C18714 Y
RTECS number GL8050000
Jmol-3D images Image 1
Image 2
Properties
Molecular formula Cu2O
Molar mass 143.09 g/mol
Appearance brownish-red solid
Density 6.0 g/cm3
Melting point

1235 °C, 1508 K, 2255 °F
Boiling point

1800 °C, 2073 K, 3272 °F
Solubility in water Insoluble
Solubility in acid Soluble
Band gap 2.137 eV
Structure
Crystal structure cubic
Hazards
MSDS SIRI.org
EU Index 029-002-00-X
EU classification Harmful (Xn)
Dangerous for the environment (N)
R-phrases R22, R50/53
S-phrases (S2), S22, S60,
NFPA 704
0
2
1
Related compounds
Other anions Copper(I) sulfide
Copper(II) sulfide
Copper(I) selenide
Other cations Copper(II) oxide
Silver(I) oxide
Nickel(II) oxide
Zinc oxide
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Copper(I) oxide or cuprous oxide is the inorganic compound with the formula Cu2O. It is one of the principal oxides of copper. This red-coloured solid is a component of some antifouling paints. The compound can appear either yellow or red, depending on the size of the particles, but both forms degrade to copper(II) oxides in moist air.[1] Copper(I) oxide is found as the reddish mineral cuprite.

Contents

Preparation

Copper(I) oxide may be produced by several methods.[2] Most straightforwardly, it arises via the oxidation of copper metal:

4 Cu + O2 → 2 Cu2O

Additives such as water and acids affect the rate of this process as well as the further oxidation to copper(II) oxides. It is also produced commercially by reduction of copper(II) solutions with sulfur dioxide. Aqueous cuprous chloride solutions react with base to give the same material. In all cases, the color is highly sensitive to the procedural details.

Formation of copper(I) oxide is the basis of the Fehling's test and Benedict's test for reducing sugars. These sugars reduce an alkaline solution of a copper(II) salt, giving a bright red precipitate of Cu2O.

It forms on silver-plated copper parts exposed to moisture when the silver layer is porous or damaged. This kind of corrosion is known as red plague.

Properties

The solid is diamagnetic. In terms of their coordination spheres, copper centres are 2-coordinated and the oxides are tetrahedral. The structure thus resembles in some sense the main polymorphs of SiO2, and both structures feature interpenetrated lattices.

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 give solutions of CuCl2-. Dilute sulfuric acid and nitric acid produce copper(II) sulfate and copper(II) nitrate, respectively.[3]

Structure

Cu2O crystallizes in a cubic structure with a lattice constant al=4.2696 Å. The Cu atoms arrange in a fcc sublattice, the O atoms in a bcc sublattice. The unit cell contains 4 Cu atoms and 2 O atoms. One sublattice is shifted by a quarter of the body diagonal. The space group is \scriptstyle Pn\bar{3}m, which includes the point group with full octahedral symmetry.

Semiconducting properties

In the history of semiconductor physics, Cu2O is one of the most studied materials, and many experimental observations and semiconductor applications have been demonstrated first in this material:

Today, it is still under investigation in semiconductor optics. Particularly people are trying to create a Bose-Einstein condensate of excitons in Cu2O.[5]

The lowest excitons in Cu2O are extremely long living and show a neV resonance, which is the narrowest bulk exciton resonance ever observed.[8] The associated quadrupole polaritons have low group velocity approaching the speed of sound. Thus, light moves almost as slowly as sound in this medium, which results in high polariton densities.

Another unusual feature of the ground state excitons is that all primary scattering mechanisms are known quantitatively.[9] 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–Kronig relations do not apply to polaritons.[5]

Applications

Cuprous oxide is commonly used as a pigment, a fungicide, and an antifouling agent for marine paints. Rectifier diodes based on this material have been used industrially as early as 1924, long before silicon became the standard.

See also

References

  1. ^ N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed., Butterworth-Heinemann, Oxford, UK, 1997.
  2. ^ H. Wayne Richardson "Copper Compounds in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a07_567
  3. ^ D. Nicholls, Complexes and First-Row Transition Elements, Macmillan Press, London, 1973.
  4. ^ L. O. Grondahl, Unidirectional current carrying device, Patent, 1927
  5. ^ a b c d e C. F. Klingshirn, Semiconductor Optics, 3rd ed., Springer, 2006, Special:Booksources/354038345X
  6. ^ L. Hanke, D. Fröhlich, A.L. Ivanov, P.B. Littlewood, and H. Stolz "LA-Phonoritons in Cu2O" Phys. Rev. Lett. 83 (1999), 4365.
  7. ^ L. Brillouin: Wave Propagation and Group Velocity, Academic Press, New York, 1960.
  8. ^ J. Brandt, D. Fröhlich, C. Sandfort, M. Bayer, H. Stolz, and N. Naka, Ultranarrow absorption and two-phonon excitation spectroscopy of Cu2O paraexcitons in a high magnetic field, Phys. Rev. Lett. 99, 217403 (2007). doi:10.1103/PhysRevLett.99.217403
  9. ^ J.P. Wolfe and A. Mysyrowicz: Excitonic Matter, Scientific American 250 (1984), No. 3, 98.

External links