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Cadmium selenide
IUPAC name Cadmium selenide
Other names Cadmium(II) selenide
Cadmoselite
Identifiers
CAS number [1306-24-7]
SMILES Cd=Se
Properties
Molecular formula CdSe
Molar mass 191. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 37 g/mol
Appearance Greenish-brown
or dark red solid powder
Density 5. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different 816 g/cm3, solid
Melting point

1268 °C (1541 K)
Solubility in water Insoluble
Structure
Crystal structure hexagonal (wurtzite)
Related compounds
Other anions Cadmium sulfide
Cadmium telluride
Other cations Zinc selenide
Mercury(II) selenide
Silver selenide
Indium selenide
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox disclaimer and references

Cadmium selenide (CdSe) is a solid, binary compound of cadmium and selenium. The melting point of a solid is the temperature range at which it changes state from solid to Liquid. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Water is a common Chemical substance that is essential for the survival of all known forms of Life. In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal. This article is about the mineral wurtzite For the wurtzite crystal structure see Wurtzite (crystal structure. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Cadmium sulfide is a chemical compound with the formula CdS. Cadmium sulfide is yellow in colour and is a semiconductor Cadmium telluride (CdTe is a Crystalline compound formed from Cadmium and Tellurium with a zinc blende (cubic crystal structure An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge Zinc selenide ( Zn[[Selenium Se]] is a light yellow binary solid compound Mercury selenide (HgSe is a chemical compound of mercury and Selenium. Heat of Fusion 569 J/g nowhere to put this in the new chembox structure--> Silver selenide (Ag2Se is a clear Hexagonal compound used in 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 In Chemistry, the standard state of a material is its state at 1 bar (100 Kilopascals exactly Cadmium (ˈkædmiəm is a Chemical element with the symbol Cd and Atomic number 48 Selenium (səˈliniəm is a Chemical element with the Atomic number 34 represented by the chemical symbol Se, an atomic mass of 78 Common names for this compound are cadmium (II) selenide, cadmium selenide, and cadmoselite.

Cadmium selenide is a semiconducting material, but has yet to find many applications in manufacturing. A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that This material is transparent to infra-red (IR) light, and has seen limited use in windows for instruments utilizing IR light.

Much current research on cadmium selenide has focused on nanoparticles. Researchers are concentrating on developing controlled syntheses of CdSe nanoparticles. In addition to synthesis, scientists are working to understand the properties of cadmium selenide, as well as apply these materials in useful ways.

Contents

Production

The production of cadmium selenide has been carried out in two different ways. The preparation of bulk crystalline CdSe is done by the High-Pressure Vertical Bridgman method or High-Pressure Vertical Zone Melting. [1]

However, cadmium selenide in the bulk form is not very interesting. The most interesting form of cadmium selenide is known as nanoparticles. In Nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties (see applications for explanation) Several methods for the production of CdSe nanoparticles have been developed: arrested precipitation in solution, synthesis in structured media, high temperature pyrolysis, sonochemical, and radiolytic methods are just a few. [2]

Production of cadmium selenide by arrested precipitation in solution is performed by introducing alkylcadmium and trioctylphosphine selenide (TOPSe) precursors into a heated solvent under controlled conditions. [3]

Me2Cd + TOPSe → CdSe + (byproducts).

Synthesis in structured environments refers to the production of cadmium selenide in liquid crystal or surfactant solutions. Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional Liquid, and those of a Solid Surfactants are wetting agents that lower the Surface tension of a liquid allowing easier spreading and lower the Interfacial tension between two liquids The addition to surfactants to solutions often results in a phase change in the solution leading to a liquid crystallinity. A liquid crystal is similar to a solid crystal in that the solution has long range translational order. Examples of this ordering are layered alternating sheets of solution and surfactant, micelles, or even a hexagonal arrangement of rods. A micelle (rarely micella, plural micelles) is an aggregate of Surfactant molecules dispersed in a liquid Colloid.

High temperature pyrolysis synthesis is usually carried out using an aerosol containing a mixture of volatile cadmium and selenium precursors. Technically an aerosol is a suspension of fine solid particles or liquid droplets in a gas The precursor aerosol is then carried through a furnace with an inert gas, such as hydrogen, nitrogen, or argon. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 This article pertains to the chemical element For other uses see Argon (disambiguation. In the furnace the precursors react to form CdSe as well as several by-products. [2]

Applications

Cadmium selenide in its wurtzite crystal structure is an important II-VI semiconductor. This article is about the mineral wurtzite For the wurtzite crystal structure see Wurtzite (crystal structure. As a semiconductor CdSe has a band gap of 1. In Solid state physics and related applied fields a band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states 74 eV at 300 K. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic It is an n-type semiconductor, which is difficult to dope p-type, however p-type doping has been achieved using nitrogen. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 [4] CdSe is also being developed for use in opto-electronic devices, laser diodes, nanosensing, and biomedical imaging. [5] They are also used being tested for use in high-efficiency solar cells[6][7][8]

Most of the usefulness of CdSe stems from nanoparticles. In Nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties Nanoparticles are just what the name implies, particles of CdSe that are 1–100 nm (1 nm = 10−9 m) in size. A nanometre ( American spelling: nanometer, symbol nm) ( Greek: νάνος nanos dwarf; μετρώ metrό count) is a CdSe particles of this size exhibit a property known as quantum confinement. A potential well is the region surrounding a Local minimum of Potential energy. Quantum confinement results when the electrons in a material are confined to a very small volume. Quantum confinement is size dependent, meaning the properties of CdSe nanoparticles are tunable based on their size. [9]

Since CdSe nanoparticles have a size dependent fluorescence spectrum, they are finding applications in optical devices such as laser diodes. Fluorescence is a Luminescence that is mostly found as an A laser diode is a Laser where the active medium is a Semiconductor similar to that found in a Light-emitting diode. Using these particles, engineers are able to manufacture laser diodes that cover a large part of the electromagnetic spectrum. The electromagnetic (EM spectrum is the range of all possible Electromagnetic radiation frequencies [10]

Along similar lines, doctors are developing these materials for use in biomedical imaging applications. Human tissue is permeable to far infra-red light. Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of By injecting appropriately prepared CdSe nanoparticles into injured tissue, it may be possible to image the tissue in those injured areas. [11]

Safety information

Cadmium is a toxic heavy metal and appropriate precautions should be taken when handling it and its compounds. Selenides are toxic in large amounts. See MSDS[12].

References

  1. ^ II-VI compound crystal growth, HPVB & HPVZM basics
  2. ^ a b Didenko, Y. Y. ; Suslick K. S. Chemical Aerosol Flow Synthesis of Semiconductor Nanoparticles. J. Am. Chem. Soc. ; (Communication); 2005; 127(35); 12196-12197
  3. ^ Bawendi et al. Synthesis of CdSe Semiconductor Nanocrystallites. J. Am. Chem. Soc. 1993, 115, 8706-8715
  4. ^ T Ohtsuka, J Kawamata, Z Zhu, T Yao, Applied Physics Letters, 65, 466-468, (1994)
  5. ^ Christopher Ma et al. Single-Crystal CdSe Nanosaws. J. Am. Chem. Soc. 2004, 126, 708-709
  6. ^ Direct carrier multiplication due to inverse Auger scattering in CdSe quantum dots. Appl. Phys. Lett. , Vol. 84, No. 13, 29 March 2004.
  7. ^ Effect of electronic structure on carrier multiplication efficiency: Comparative study of PbSe and CdSe nanocrystals. Appl. Phys. Lett. 87, 253102 (2005).
  8. ^ Direct Observation of Electron-to-Hole Energy Transfer in CdSe Quantum Dots. PRL 96, 057408 (2006).
  9. ^ Nanotechnology Structures - Quantum Confinement
  10. ^ Colvin, V. L. ; Schlamp, M. C. ; Alivisato, A. P. Nature 1994, 370, 354.
  11. ^ (a) Chan, W. C. ; Nie, S. M. Science 1998, 281, 2016. (b) Bruchez, M. ;Moronne, M. ; Gin, P. ; Weiss, S. ; Alivisatos, A. P. Science 1998, 281, 2013.
  12. ^ Additional safety information available at www. msdsonline. com, search 'cadmium selenide. '

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