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Encyclopedia > Cadmium selenide
Cadmium selenide
General
Systematic name Cadmium selenide
Other names Cadmium(II) selenide
Cadmoselite
Molecular formula CdSe
Molar mass 191.37 g/mol
Appearance Greenish-brown
or dark red solid powder
CAS number [[1306-24-7]]
SMILES Cd=Se
Properties
Density and phase 5.816 g/cm3, solid
Solubility in water Insoluble
Melting point 1268 °C (1541 K)
Structure
Coordination geometry  ?
Crystal structure hexagonal (wurtzite)
Hazards
MSDS External MSDS
Main hazards  ?
NFPA 704
R/S statement R: 20/21/22-50/53

S: 60-61 IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. ... This article does not cite any references or sources. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... The simplified molecular input line entry specification or SMILES is a specification for unambiguously describing the structure of chemical molecules using short ASCII strings. ... For other uses, see Density (disambiguation). ... In the physical sciences, a phase is a set of states of a macroscopic physical system that have relatively uniform chemical composition and physical properties (i. ... It has been suggested that this article or section be merged with Solution. ... H2O and HOH redirect here. ... The melting point of a crystalline solid is the temperature range at which it changes state from solid to liquid. ... The coordination geometry of an atom is the geometrical pattern formed by its neighbors in a molecule or a crystal. ... Enargite crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... Zinc sulfide is a chemical compound with the formula ZnS. Zinc sulfide is a white to yellow colored powder or crystal. ... An example MSDS in a US format provides guidance for handling a hazardous substance and information on its composition and properties. ... The examples and perspective in this article or section may not represent a worldwide view. ... NFPA 704 is a standard maintained by the U.S. National Fire Protection Association. ... Risk and Safety Statements, also known as R/S statements, R/S numbers, R/S phrases, and R/S sentences, is a system of hazard codes and phrases for labeling dangerous chemicals and compounds. ...

RTECS number  ?
Supplementary data page
Structure & properties n, εr, etc.
Thermodynamic data Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
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. Common names for this compound are cadmium (II) selenide, cadmium selenide, and cadmoselite. RTECS, also known as Registry of Toxic Effects of Chemical Substances, is a database of toxicity information compiled from the open scientific literature that is available for charge. ... The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. ... The relative dielectric constant of a material under given conditions is a measure of the extent to which it concentrates electrostatic lines of flux. ... Ultraviolet-Visible Spectroscopy or Ultraviolet-Visible Spectrophotometry (UV/ VIS) involves the spectroscopy of photons (spectrophotometry). ... Infrared spectroscopy (IR Spectroscopy) is the subset of spectroscopy that deals with the IR region of the EM spectrum. ... Nuclear magnetic resonance spectroscopy most commonly known as NMR spectroscopy is the name given to the technique which exploits the magnetic properties of certain nuclei. ... Mass spectrometry (also known as mass spectroscopy (deprecated)[1] or informally, mass-spec and MS) is an analytical technique used to measure the mass-to-charge ratio of ions. ... This article is about the electrically charged particle. ... Cadmium sulfide (UK English sulphide), the mineral greenockite, is an hexagonal, yellowish crystal with specific gravity of 4. ... This article is about the electrically charged particle. ... Zinc selenide (ZnSe), is a light yellow binary solid compound. ... Mercury selenide (HgSe) is a chemical compound of mercury and selenium. ... This article or section is in need of attention from an expert on the subject. ... Indium(III) selenide is a compound of indium and selenium. ... In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals) and 25 degrees Celsius (298. ... General Name, Symbol, Number cadmium, Cd, 48 Chemical series transition metals Group, Period, Block 12, 5, d Appearance silvery gray metallic Standard atomic weight 112. ... For other uses, see Selenium (disambiguation). ...


Cadmium selenide is a semiconducting material, but has yet to find many applications in manufacturing. This material is transparent to infra-red (IR) light, and has seen limited use in windows for instruments utilizing IR light. A semiconductor is a solid whose electrical conductivity is in between that of a conductor and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ...


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. (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] Very Basic Description A nanoparticle is a microscopic particle whose size is measured in nanometers. ...


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. 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. Schlieren texture of Liquid Crystal nematic phase Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional liquid, and those of a solid crystal. ... Surfactants are wetting agents that lower the surface tension of a liquid, allowing easier spreading, and lower the interfacial tension between two liquids. ... Schematic of a micelle. ...


High temperature pyrolysis synthesis is usually carried out using an aerosol containing a mixture of volatile cadmium and selenium precursors. The precursor aerosol is then carried through a furnace with an inert gas, such as hydrogen, nitrogen, or argon. In the furnace the precursors react to form CdSe as well as several by-products.[2] Aerosol, is a term derived from the fact that matter floating in air is a suspension (a mixture in which solid or liquid or combined solid-liquid particles are suspended in a fluid). ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18, 3, p Appearance colorless Standard atomic weight 39. ...


Applications

Cadmium selenide in its wurtzite crystal structure is an important II-VI semiconductor. As a semiconductor CdSe has a band gap of 1.74 eV at 300 K. It is an n-type semiconductor, which is difficult to dope p-type, however p-type doping has been achieved using nitrogen. [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] Zinc sulfide is a chemical compound with the formula ZnS. Zinc sulfide is a white to yellow colored powder or crystal. ... This article or section does not adequately cite its references or sources. ... For other uses, see Kelvin (disambiguation). ... General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ...


Most of the usefulness of CdSe stems from nanoparticles. Nanoparticles are just what the name implies, particles of CdSe that are 1–100 nm (1 nm = 10−9 m) in size. CdSe particles of this size exhibit a property known as quantum confinement. 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] Very Basic Description A nanoparticle is a microscopic particle whose size is measured in nanometers. ... A nanometre (American spelling: nanometer) is 1. ... A potential well is the region surrounding a local minimum of potential energy. ...


Since CdSe nanoparticles have a size dependent fluorescence spectrum, they are finding applications in optical devices such as laser diodes. Using these particles, engineers are able to manufacture laser diodes that cover a large part of the electromagnetic spectrum.[10] Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ... A packaged laser diode with penny for scale. ... Legend γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultra high frequency VHF = Very high frequency HF = High...


Along similar lines, doctors are developing these materials for use in biomedical imaging applications. Human tissue is permeable to far infra-red light. By injecting appropriately prepared CdSe nanoparticles into injured tissue, it may be possible to image the tissue in those injured areas.[11] Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ...


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. ^ http://www.sttic.com.ru/lpcbc/Basics.html
  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 CdE 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. ^ http://www.ringsurf.com/info/Technology_/Nanotechnology/Structures/
  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.'

Related materials

Cadmium sulfide (UK English sulphide), the mineral greenockite, is an hexagonal, yellowish crystal with specific gravity of 4. ... Cadmium telluride (CdTe) is a crystalline compound formed from cadmium and tellurium with a zinc blende (cubic) crystal structure (space group F43m). ... Zinc selenide (ZnSe), is a light yellow binary solid compound. ... Mercury selenide (HgSe) is a chemical compound of mercury and selenium. ...

External links

  • Quantum Dots in Solar Cells Science News Week of June 3, 2006; Vol. 169, No. 22 , p. 344.
  • National Pollutant Inventory - Cadmium and compounds
  • National Compound semiconductor roadmap at ONR.

  Results from FactBites:
 
High efficiency selenium heterojunction solar cells - Patent 4064522 (1588 words)
Cadmium selenide layers that are much thicker become opaque and render the cell less efficient inasmuch as most of the current carriers generated by the sunlight are generated in the selenium layer.
Cadmium selenide displays high carrier concentrations and carrier mobility, both of which are desirable properties in the vicinity of the heterojunction because these properties determine the current generating capabilities of the cell.
Cadmium selenide and cadmium oxide layers were formed in one process step by reactively sputtering cadmium metal in a 60/40 nitrogen/oxygen gas mixture at a pressure of ten microns of mercury for eighteen minutes at a radio frequency power density of 0.5 watt/cm.sup.2.
Cadmium (528 words)
Electrolytic cadmium is 99.95% pure and is obtained primarily as a by-product of the zinc industry by treating the flue dust and fumes from the roasting of the ores.
Cadmium is implemented as an alloying element in soft solders and in fusible alloys.
Cadmium is used as a white corrosion-resistant plating metal (as a anode).
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