Metal selenides

Cadmium selenide is of interest for photosensitized electron transfer reactions used for solar energy conversion and photocatalysis. Small ensembles of CdSe have been synthesized within the cages of zeolite Y by ion exchange with Cd(II) and subsequent treatment with H2Se. [235] The presence of CdSe clusters with Cd-Se bond lengths of 2.60 A was inferred from EXAFS data measured at both the Cd and Se absorption edges. 

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These closely resemble the corresponding sulphides. The alkali metal selenides and tellurides are colourless solids, and are powerful reducing agents in aqueous solution, being oxidised by air to the elements selenium and tellurium respeetively (cf. the reducing power of the hydrides). 

Bina Selenides. Most biaary selenides are formed by beating selenium ia the presence of the element, reduction of selenites or selenates with carbon or hydrogen, and double decomposition of heavy-metal salts ia aqueous solution or suspension with a soluble selenide salt, eg, Na2Se or (NH 2S [66455-76-3]. Atmospheric oxygen oxidizes the selenides more rapidly than the corresponding sulfides and more slowly than the teUurides. Selenides of the alkah, alkaline-earth metals, and lanthanum elements are water soluble and readily hydrolyzed. Heavy-metal selenides are iasoluble ia water. Polyselenides form when selenium reacts with alkah metals dissolved ia hquid ammonia. Metal (M) hydrogen selenides of the M HSe type are known. Some heavy-metal selenides show important and useful electric, photoelectric, photo-optical, and semiconductor properties. Ferroselenium and nickel selenide are made by sintering a mixture of selenium and metal powder. 

Selen-kupfer, n. copper selenide. -kupfer-silber, n. copper silver selenide (Min.) eucairite. -metall, n. metallic selenide. 

Among all semiconductor NPs, metal selenides have been the focus of great attention due to their importance in various applications such as thermoelectric cooling materials, optical filters and sensors, optical recording materials, solar cells, superionic materials, laser materials and biological labels. Many synthetic methods have been developed for the preparation of relatively monodispersed selenide nanopartides (Murray et al., 1993 Korgel... 

The induced co-deposition concept has been successfully exemplified in the formation of metal selenides and tellurides (sulfur has a different behavior) by a chalcogen ion diffusion-limited process, carried out typically in acidic aqueous solutions of oxochalcogenide species containing quadrivalent selenium or tellurium and metal salts with the metal normally in its highest valence state. This is rather the earliest and most studied method for electrodeposition of compound semiconductors [1]. For MX deposition, a simple (4H-2)e reduction process may be considered to describe the overall reaction at the cathode, as for example in... 

Rastogi AC, Balakiishnan KS, Garg A (1993) A new electrochemical selenization technique for preparation of metal-selenide semiconductor thin films. J Electrochem Soc 140 2373-2375... 

Fofanov GM, Kitaev GA (1969) Analysis of the conditions for the precipitation of metal selenides from aqueous solutions with sodium selenosulphate. Russ J Inorg Chem 14 322-324... 

Distorted square planar NiSe4 cores are observed in mixed-metal selenides, e.g., (402). The [Ni(WSe4)2]2 anion is analogous to [Ni(WS4)2]. Using slightly different reaction conditions,... 

A number of zinc selenium complexes have now been characterized, with particular interest in the formation of zinc selenide semiconductors and quantum dots. In many cases analogous structures to those observed with thiol or thiolates are recorded. 77Se NMR is frequently used in characterization, and comparison with the sulfur equivalent is relevant. Zinc selenium compounds are of particular interest as precursors for metal/selenide materials and their relevance as models for selenocysteine-containing metalloproteins. 

Selenate is the most mobile form of Se. Selenium becomes biologically unavailable by reduction to elemental Se or by formation of metal selenides or Se-sulfides. Inorganic Se compounds can be converted to volatile organic Se such as dimethyl selenide or dimethyl diselenide by... 

The retarding action of metal selenides on cyclohexene oxidation initiated by AIBN was proved in Ref. [11]. The addition of metal selenides decreases the oxidation rate (T 343 K, p02 = 98 kPa, [AIBN] = 2.5 x 1(T2 mol L-1). 

Dhingra, S. Kanatzidis, M. G. 1990. The use of soluble metal-polyselenide complexes as precursors to binary and ternary solid metal selenides. Mater. Res. Soc. Symp. Proc. 180 825-830. 

Used industrially for preparation of metallic selenides, organoselenium compounds, and preparation of semiconductor materials. 

Metal selenides, 22 87 Metal semiconductor FETs (MESFETs), 22 163. See also Field effect transistors (FETs)... 

Selenides, tellurides andpolonides. Se, Te and Po react easily with most metals and non-metals to form binary compounds (selenides and tellurides are common mineral forms of these elements). Non-stoichiometry is frequently observed in the compounds with the transition elements many of these compounds may be described as metallic alloys. The compounds of the metals of the first two groups may be considered the salts of the acids H2Se, H2Te, etc. The alkali metal selenides... 

Sources. Produced by reaction of acids or water with metal selenides... 

Hydrogen selenide is used in preparation of metal selenides and organosel-nium derivatives. It also is used in doping mix for semiconductor apphcations. 

Alternatively, the compound may be prepared by treating an alkali metal selenide with hydrochloric acid during mild heating ... 

Hydrogen selenide reacts with most metals forming metal selenides with the liberation of hydrogen ... 

Metal oxides are converted to metal selenides on heating ... 

Molten selenium combines with most metals forming selenides. Such metal selenides include Ag2Se, Cu2Se, HgSe, ZnSe, CdSe, PbSe, FeSe, FeSe2, and Sb2Se3. 

In contrast, the analogous diethyl-diselenocarbamates (dsc) have been shown to be poor sources for the deposition of ZnSe or CdSe films. Under similar reaction conditions (10 -10 Torr, 370-420° C) the diethyl dsc precursors give films of the metal selenide heavily contaminated with selenium [108]. However the mixed alkyl dsc complex Eq. 4 have been used successfully to deposit thin films of CdSe or ZnSe [109,110]. 

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