Cadmium sulfide

From Wikipedia, the free encyclopedia

Cadmium sulfide
3D model of the structure of hawleyite
3D model of the structure of greenockite
Other names Cadmium(II) sulfide
Identifiers
CAS number [1306-23-6]
EINECS number 215-147-8
RTECS number EV3150000
Properties
Molecular formula CdS
Molar mass 144.46 g/mol
Appearance Yellow-orange solid.
Density 4.82 g/cm3, solid.
Melting point

1750°C at 100 bar
Boiling point

980°C subl.
Solubility in water Insoluble
Structure
Crystal structure Hexagonal
Hazards
EU classification Toxic
Carc. Cat. 2
Muta. Cat. 3
Repr. Cat. 3
Dangerous for
the environment
Flash point non flammable
Related compounds
Other anions Cadmium oxide
Cadmium selenide
Other cations Zinc sulfide
Mercury sulfide
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Cadmium sulfide is a chemical compound with the formula CdS. Cadmium sulfide is yellow in colour and is a semiconductor.[1] It exists in nature as two different minerals, greenockite[1] and hawleyite.[2] Cadmium sulfide is a direct band gap semiconductor (gap 2.42 eV [3]) and has many applications for example in light detectors. It forms thermally stable pigments and with the addition of e.g CdTe, HgS colours ranging from deep red to yellow are formed.[4]

Contents

[edit] Preparation

Cadmium sulfide can be prepared by the precipitation from soluble cadmium(II) salts with sulfide ion and this has been used in the past for the gravimetric analysis of cadmium.[5]
Pigment production usually involves the precipitation of CdS, the washing of the precipitate to remove soluble cadmium salts followed by calcination(roasting) to convert it to the hexagonal form followed by milling to produce a powder. [6] When cadmium sulfide selenides are required the CdSe is co-precipitated with CdS and the cadmium sulfoselenide is created during the calcination step.[6]
Industrially the production of thin films of CdS is required in e.g. photoresistors and CBD, Chemical bath deposition, has been investigated using the hydrolysis of thiourea as the source of sulfide anions and an ammonium salt /ammonia buffer solution to control pH:[7]

Cd2+ + NH3 → [Cd(NH3)4]2+
NH2CS + OH− → SH− + H2O + H2CN2
SH− + OH− → S2− + CdS

Cadmium sulfide can be produced from volatile cadmium alkyls, an example is the reaction of dimethylcadmium with diethyl sulfide to produce a film of CdS using MOCVD techniques.[8]

The preparative route and the subsequent treatment of the product, affects the polymorphic form that is produced. It has been asserted in the past that chemical precipitation methods produce the cubic zincblende form [9] however there more recent examples where the hexagonal form is produced, e.g. see[10]

[edit] Chemical Properties

Cadmium sulfide is soluble in acids and this has been investigated as a method of extracting the pigment from waste polymers e.g. HDPE pipes [11]:

CdS + HCl → CdCl2 + H2S

When sulfide solutions containing dispersed CdS particles are irradiated with light hydrogen gas is generated: [12]

H2S → H2 + S ΔHf = +9.4 kcal/mol

The reaction mechanism proposed involves the electron/hole pairs created when incident light is absorbed by the cadmium sulfide[3] followed by these reacting with water and sulfide:[12]

Production of an electron hole pair
CdS + hν → e− + hole+
Reaction of electron
2e− + 2H2O → H2 + 2OH−
Reaction of hole
2hole+ + S2− → S

[edit] Structure and Physical Properties

Cadmium sulfide has, like zinc sulfide, two crystal forms; the more stable hexagonal wurtzite structure (found in the mineral Greenockite) and the cubic zinc blende (found in the mineral Hawleyite). In both of these forms the Cadmium and sulfur atoms are four coordinate.[13] There is also a high pressure form with the NaCl rock salt structure.[13]

Cadmium sulfide is a direct bandgap semiconductor with a bandgap of 2.42 eV at 300 K.[3]The magnitude of its band gap means that it appears coloured.[1]
As well as this obvious property others properties result:

[edit] Industrial Processes used to produce thin films

Thin films of CdS are required in components such as a photoresistor and solar cells. Various methods have been used to deposit these thin films, for example (note: there is a large body of research in this area and only representative references are given):

[edit] Pigment

CdS is known as Cadmium yellow [1] (CI pigment yellow 37[27]) By adding varying amounts of selenium as selenide it is possible to obtain a range of colors for example CI pigment orange 20 and CI pigment red 108.[27]
Synthetic cadmium pigments based on cadmium sulfide are valued for their good thermal stability, light and weather fastness, chemical resistance and high opacity.[6] The general commercial availability of cadmium sulfide from the 1840's lead to its adoption by artists notably Van Gogh, Monet(in his London series and other works) and Matisse (Bathers by a river 1916-1919)[28] the presence of cadmium in paints has been used to detect forgeries in paintings alleged to have been produced prior to the 19th century.[29] CdS is used as pigment in plastics[6]

[edit] Biological

Cadmium sulfide is produced by sulfate reducing bacteria.[30] This ability is being investigated as a means of producing nano- crystalline CdS [31]

[edit] References

  1. ^ a b c d Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0123526515
  2. ^ Hawleyite, isometric cadmium sulphide, a new mineral Traill R J, Boyle R W American Mineralogist 40 (1955) 555-559
  3. ^ a b c d Charles Kittel Introduction to Solid State Physics- 7th Edition (1995) Wiley-India ISBN 1081-265-1045-5
  4. ^ Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements, 2nd Edition, Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4. 
  5. ^ Fred Ibbotson (2007) The Chemical Analysis of Steel-Works' Materials READ BOOKS ISBN 1406781134
  6. ^ a b c d Hugh MacDonald Smith High Performance Pigments 2002 Wiley-VCH ISBN 3527302042
  7. ^ a b Optimization of Chemical Bath Deposited Cadmium Sulfide, I.O. Oladeji, L. Chow, J. Electrochem. Soc., 144, 7, (1997)
  8. ^ a b Thin CdS films prepared by metalorganic chemical vapor deposition, Hiroshi Uda , Hideo Yonezawa, Yoshikazu Ohtsubo, Manabu Kosaka and Hajimu Sonomura Solar Energy Materials and Solar Cells 75, 1-2, (2003), 219-226 doi:10.1016/S0927-0248(02)00163-0
  9. ^ Paul Klocek (1991) Handbook of Infrared Optical Materials CRC Press ISBN 0824784685
  10. ^ Optical characterization of vacuum evaporated cadmium sulfide films U. Pal, R. Silva-González, G. Martínez-Montes, M. Gracia-Jiménez, M.A. Vidal and Sh. Torres Thin Solid Films 305, 1-2, 1997, 345-350,doi:10.1016/S0040-6090(97)00124-7
  11. ^ Extraction of CdS pigment from waste polyethylene Wanrooij P. H. P., Agarwal U. S., Meuldijk J., van Kasteren J. M. N., Lemstra P. J., Journal of Applied Polymer Science 100, 2 , 1024 – 1031 doi:10.1002/app.22962
  12. ^ a b Mario Schiavello (1985 ) Photoelectrochemistry, Photocatalysis, and Photoreactors: Fundamentals and Developments Springer ISBN:9027719462
  13. ^ a b Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
  14. ^ Antonio Luque, Steven Hegedus, (2003), Handbook of Photovoltaic Science and Engineering John Wiley and Sons ISBN 0471491969
  15. ^ Photovoltaic Effect in Cadmium Sulfide D. C. Reynolds, G. Leies, L. L. Antes, R. E. Marburger, Phys. Rev. 96, 2, 533 - 534 (1954) doi:10.1103/PhysRev.96.533
  16. ^ C. Fouassier,(1994), Luminescence in Encyclopedia of Inorganic Chemistry, John Wiley & Sons ISBN 0471936200
  17. ^ A. K. Cheetham, P. Day 1992 Solid State Chemistry: Compounds Oxford University Press ISBN 0198551665
  18. ^ Temperature Dependence of the Pyroelectric Effect in Cadmium Sulfide W. J. Minkus Phys. Rev. 138, A1277 - A1287 (1965) doi:10.1103/PhysRev.138.A1277
  19. ^ Low-Field Electroluminescence in Insulating Crystals of Cadmium Sulfide, Roland W. Smith, Phys. Rev. 105, 900 - 904 (1957) doi:10.1103/PhysRev.105.900
  20. ^ KGP-2: an electron-beam-pumped cadmium sulfide laser, Yu A Akimov, A A Burov, Yu A Drozhbin, V A Kovalenko, S E Kozlov, I V Kryukova, G V Rodichenko, B M Stepanov , V A Yakovlev, Sov. J. Quantum Electron. 2 284-285 doi:10.1070/QE1972v002n03ABEH004443
  21. ^ Lasing in single cadmium sulfide nanowire optical cavities, Agarwal R, Barrelet CJ, Lieber CM.,Nano Lett. 2005 5(5):917-20. [1]
  22. ^ Nanosized semiconductor particles in glasses prepared by the sol–gel method: their optical properties and potential uses, Journal of Alloys and Compounds, 341, 1-2,(2002),56-61,doi:10.1016/S0925-8388(02)00059-2
  23. ^ Comparative studies of the properties of CdS films deposited on different substrates by R.F. sputtering, Byung-Sik Moon, Jae-Hyeong Lee, Hakkee Jung, Thin Solid Films,511-512,(2006),299-303,doi:10.1016/j.tsf.2005.11.080
  24. ^ Defect reduction in electrochemically deposited CdS thin films by annealing in 02 Fumitaka Goto, Katsunori Shirai, Masaya Ichimura, Solar Energy Materials and Solar Cells, 50, 1-4, (1998), 147-153, doi:10.1016/S0927-0248(97)00136-0
  25. ^ United States Patent 4,086,101, Photovoltaic cells, J.F Jordan, C.M Lampkin Issue date: April 25, 1978
  26. ^ US Patent 3208022, High performance photoresistor,Y . T. Sihvonen Issue date: Sep 21, 1965
  27. ^ a b Colour Chemistry R. M. Christie 2001 Royal Society of Chemistry ISBN:0854045732
  28. ^ Sidney Perkowitz 1998 Empire of Light: A History of Discovery in Science and Art, Joseph Henry Press, ISBN 0309065569
  29. ^ W. Stanley Taft, James W. Mayer, Richard Newman, Peter Kuniholm, Dusan Stulik (2000) The Science of Paintings, Springer, ISBN 0387987223
  30. ^ Larry L. Barton 1995 Sulfate reducing bacteria, Springer, ISBN 0306448572
  31. ^ Bacterial Biosynthesis of Cadmium Sulfide Nanocrystals. R. Sweeney , C. Mao , X. Gao , J. Burt , A. Belcher , G. Georgiou , B. Iverson, Chemistry & Biology , 11 , 11 , 1553 - 1559, doi:10.1016/j.chembiol.2004.08.022

[edit] External links

 This inorganic compound-related article is a stub. You can help Wikipedia by expanding it.