Cadmium sulfide

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Cadmium sulfide
Other names

Cadmium(II) sulfide,
Greenockite
Hawleyite

Identifiers
CAS number 1306-23-6 YesY
PubChem 14783
ChemSpider 7969586 YesY
UNII 057EZR4Z7Q YesY
EC number 215-147-8
UN number 2570
RTECS number EV3150000
Jmol-3D images {{#if:[S-2].[Cd+2]|Image 1
Properties
Molecular formula CdS
Molar mass 144.48 g mol−1
Appearance Yellow-orange to brown solid.
Density 4.826 g/cm3, solid.
Melting point 1,750 °C; 3,180 °F; 2,020 K (10 MPa)
Boiling point 980 °C; 1,800 °F; 1,250 K (subl.)
Solubility in water insoluble[1]
Solubility soluble in acid
very slightly soluble in ammonium hydroxide
Refractive index (nD) 2.529
Structure
Crystal structure Hexagonal, Cubic
Thermochemistry
Std enthalpy of
formation ΔfHo298		 −162 kJ·mol−1[2]
Standard molar
entropy So298		 65 J·mol−1·K−1[2]
Hazards
MSDS ICSC 0404
EU Index 048-010-00-4
EU classification Carc. Cat. 2
Muta. Cat. 3
Repr. Cat. 3
Toxic (T)
Dangerous for the environment (N)
R-phrases R45, R22, R48/23/25, R62, R63, R68, R50/53
S-phrases S53, S45, S61
NFPA 704
0
3
0
Flash point Non-flammable
LD50 7080 mg/kg (rat, oral)
Related compounds
Other anions Cadmium oxide
Cadmium selenide
Other cations Zinc sulfide
Mercury sulfide
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Cadmium sulfide is the inorganic compound with the formula CdS. Cadmium sulfide is a yellow solid.[3] It occurs in nature with two different crystal structures as the rare minerals greenockite and hawleyite, but is more prevalent as an impurity substituent in the similarly structured zinc ores sphalerite and wurtzite, which are the major economic sources of cadmium. As a compound that is easy to isolate and purify, it is the principal source of cadmium for all commercial applications.[3]

Production

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 gravimetric analysis and qualitative inorganic analysis.[4]
The preparative route and the subsequent treatment of the product, affects the polymorphic form that is produced (i.e., cubic vs hexagonal). It has been asserted that chemical precipitation methods result in the cubic zincblende form[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]

Routes to thin films of CdS

Thin films of CdS are components in some photoresistors and solar cells. In the chemical bath deposition method, thin films of CdS have been prepared using thiourea as the source of sulfide anions and an ammonium buffer solution to control pH:[7]

Cd2+ + H2O + (NH2)2CS + 2 NH3 → CdS + (NH2)2CO + 2 NH4+

Cadmium sulfide can be produced using metalorganic vapour phase epitaxy and MOCVD techniques.[8] This process requies volatile cadmium and sulfur precursors. A common example is the reaction of dimethylcadmium with diethyl sulfide:[8] Many other 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):

Cd(CH3)2 + Et2S → CdS + CH3CH3 + C4H10

Other methods include

Reactions

Cadmium sulfide is soluble in (actually degraded by) acids, and this conversion has been investigated as a method of extracting the pigment from waste polymers e.g. HDPE pipes:[14]

CdS + 2 HCl → CdCl2 + H2S

When sulfide solutions containing dispersed CdS particles are irradiated with light hydrogen gas is generated:[15]

H2S → H2 + S ΔHf = +9.4 kcal/mol

The proposed mechanism involves the electron/hole pairs created when incident light is absorbed by the cadmium sulfide[16] followed by these reacting with water and sulfide:[15]

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

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 structure (found in the mineral Hawleyite). In both of these forms the cadmium and sulfur atoms are four coordinate.[17] There is also a high pressure form with the NaCl rock salt structure.[17]

Cadmium sulfide is a direct band gap semiconductor (gap 2.42 eV[16]). The magnitude of its band gap means that it appears coloured.[3]
As well as this obvious property others properties result:

  • the conductivity increases when irradiated with light[16] (leading to uses as a photoresistor)
  • when combined with a p-type semiconductor it forms the core component of a photovoltaic (solar) cell and a CdS/Cu2S solar cell was one of the first efficient cells to be reported (1954)[18][19]
  • when doped with for example Cu+ ("activator") and Al3+ ("coactivator") CdS luminesces under electron beam excitation (cathodoluminescence) and is used as phosphor[20]
  • both polymorphs are piezoelectric and the hexagonal is also pyroelectric[21]
  • electroluminescence[22]
  • CdS crystal can act as a solid state laser[23][24]

Applications

CdS is predominantly used as a pigment. About 2000 tons are produced annually.[25]

CdS and cadmium selenide are used in manufacturing of photoresistors (light dependent resistors) sensitive to visible and near infrared light.

In thin-film form, CdS can be combined with other layers for use in certain types of solar cells.[26] CdS was also one of the first semiconductor materials to be used for thin-film transistors (TFTs).[27] However interest in compound semiconductors for TFTs largely waned after the emergence of amorphous silicon technology in the late 1970s. Thin films of Cadmium Sulfide can be piezoelectric and have been used as transducers which can operate at frequencies in the GHz region.

Pigment

CdS is known as cadmium yellow[3] (CI pigment yellow 37[28]). 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.[28]
Synthetic cadmium pigments based on cadmium sulfide are valued for their good thermal stability, light and weather fastness, chemical resistance and high opacity.[6] (but with problems of biocompatibility when used as colors in tattoos[29]). The general commercial availability of cadmium sulfide from the 1840s led to its adoption by artists, notably Van Gogh, Monet (in his London series and other works) and Matisse (Bathers by a river 1916–1919).[30] The presence of cadmium in paints has been used to detect forgeries in paintings alleged to have been produced prior to the 19th century.[31] CdS is used as pigment in plastics.[6]

Biological

Cadmium sulfide is sometimes associated with sulfate reducing bacteria.[32][33]

References

  1. ↑ Lide, David R. (1998). Handbook of Chemistry and Physics (87 ed.). Boca Raton, FL: CRC Press. pp. 4–67; 1363. ISBN 0-8493-0594-2. 
  2. ↑ 2.0 2.1 Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A21. ISBN 0-618-94690-X. 
  3. ↑ 3.0 3.1 3.2 3.3 Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier ISBN 0-12-352651-5
  4. ↑ Fred Ibbotson (2007), The Chemical Analysis of Steel-Works' Materials,Read Books, ISBN 1-4067-8113-4
  5. ↑ Paul Klocek (1991), Handbook of Infrared Optical Materials, CRC Press ISBN 0-8247-8468-5
  6. ↑ 6.0 6.1 6.2 6.3 Hugh MacDonald Smith (2002). High Performance Pigments. Wiley-VCH. ISBN 3-527-30204-2. 
  7. ↑ Optimization of Chemical Bath Deposited Cadmium Sulfide, I.O. Oladeji, L. Chow, 'J. Electrochem. Soc., 144, 7, (1997)
  8. ↑ 8.0 8.1 Uda, H; Yonezawa, H; Ohtsubo, Y; Kosaka, M; Sonomura, H (2003). "Thin CdS films prepared by metalorganic chemical vapor deposition". Solar Energy Materials and Solar Cells 75 (1-2): 219. doi:10.1016/S0927-0248(02)00163-0. 
  9. ↑ Reisfeld, R (2002). "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): 56. doi:10.1016/S0925-8388(02)00059-2. 
  10. ↑ Moon, B; Lee, J; Jung, H (2006). "Comparative studies of the properties of CdS films deposited on different substrates by R.F. sputtering". Thin Solid Films. 511-512: 299. doi:10.1016/j.tsf.2005.11.080. 
  11. ↑ Goto, F (1998). "Defect reduction in electrochemically deposited CdS thin films by annealing in O2". Solar Energy Materials and Solar Cells 50 (1-4): 147. doi:10.1016/S0927-0248(97)00136-0. 
  12. ↑ U.S. Patent 4,086,101 Photovoltaic cells, J.F. Jordan, C.M. Lampkin Issue date: April 25, 1978
  13. ↑ U.S. Patent 3,208,022, High performance photoresistor, Y.T. Sihvonen, issue date: September 21, 1965
  14. ↑ Wanrooij, P. H. P.; Agarwal, U. S.; Meuldijk, J.; Kasteren, J. M. N. van; Lemstra, P. J. (2006). "Extraction of CdS pigment from waste polyethylene". Journal of Applied Polymer Science 100 (2): 1024. doi:10.1002/app.22962. 
  15. ↑ 15.0 15.1 Mario Schiavello (1985) Photoelectrochemistry, Photocatalysis, and Photoreactors: Fundamentals and Developments Springer ISBN 90-277-1946-2
  16. ↑ 16.0 16.1 16.2 D. Lincot, Gary Hodes Chemical Solution Deposition of Semiconducting and Non-Metallic Films: Proceedings of the International Symposium The Electrochemical Society, 2006 ISBN 1-56677-433-0
  17. ↑ 17.0 17.1 Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
  18. ↑ Antonio Luque, Steven Hegedus, (2003), Handbook of Photovoltaic Science and Engineering John Wiley and Sons ISBN 0-471-49196-9
  19. ↑ Reynolds, D.; Leies, G.; Antes, L.; Marburger, R. (1954). "Photovoltaic Effect in Cadmium Sulfide". Physical Review 96 (2): 533. doi:10.1103/PhysRev.96.533. 
  20. ↑ C. Fouassier,(1994), Luminescence in Encyclopedia of Inorganic Chemistry, John Wiley & Sons ISBN 0-471-93620-0
  21. ↑ Minkus, Wilfred (1965). "Temperature Dependence of the Pyroelectric Effect in Cadmium Sulfide". Physical Review 138 (4A): A1277. doi:10.1103/PhysRev.138.A1277. 
  22. ↑ Smith, Roland (1957). "Low-Field Electroluminescence in Insulating Crystals of Cadmium Sulfide". Physical Review 105 (3): 900. doi:10.1103/PhysRev.105.900. 
  23. ↑ Akimov, Yu A; Burov, A A; Drozhbin, Yu A; Kovalenko, V A; Kozlov, S E; Kryukova, I V; Rodichenko, G V; Stepanov, B M et al. (1972). "KGP-2: AN ELECTRON-BEAM-PUMPED CADMIUM SULFIDE LASER". Soviet Journal of Quantum Electronics 2 (3): 284. doi:10.1070/QE1972v002n03ABEH004443. 
  24. ↑ Agarwal, Ritesh; Barrelet, Carl J.; Lieber, Charles M. (2005). "Lasing in Single Cadmium Sulfide Nanowire Optical Cavities". Nano Letters 5 (5): 917. doi:10.1021/nl050440u. PMID 15884894. 
  25. ↑ Karl-Heinz Schulte-Schrepping, Magnus Piscator "Cadmium and Cadmium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2007 Wiley-VCH, Weinheim. doi:10.1002/14356007.a04 499.
  26. ↑ H. Zhao et al, "The effect of impurities on the doping and VOC of CdTe/CdS thin film solar cells", Thin Solid Films, Vol. 517, No. 7 (2009) pp. 2365-2369, doi:10.1016/j.tsf.2008.11.041
  27. ↑ P.K. Weimar, "The TFT a new thin-film transistor", Proc. IRE, Vol. 50, No. 6 (1962) pp. 1462-1469, doi:10.1109/JRPROC.1962.288190
  28. ↑ 28.0 28.1 R. M. Christie 2001 Colour Chemistry, p. 155 Royal Society of Chemistry ISBN 0-85404-573-2
  29. ↑ Bjornberg A. (1963), Reactions to light in yellow tattoos from cadmium sulfide ; Arch Dermatol. 1963 Sep;88:267-71. PMID:14043617
  30. ↑ Sidney Perkowitz, 1998, Empire of Light: A History of Discovery in Science and Art Joseph Henry Press, ISBN 0-309-06556-9
  31. ↑ W. Stanley Taft, James W. Mayer, Richard Newman, Peter Kuniholm, Dusan Stulik (2000) The Science of Paintings, Springer, ISBN 0-387-98722-3
  32. ↑ Larry L. Barton 1995 Sulfate reducing bacteria, Springer, ISBN 0-306-44857-2
  33. ↑ Sweeney, Rozamond Y.; Mao, Chuanbin; Gao, Xiaoxia; Burt, Justin L.; Belcher, Angela M.; Georgiou, George; Iverson, Brent L. (2004). "Bacterial Biosynthesis of Cadmium Sulfide Nanocrystals". Chemistry & Biology 11 (11): 1553. doi:10.1016/j.chembiol.2004.08.022. PMID 15556006. 

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