Carbon Selenide Telluride

Carbon selenide telluride is a thermally very unstable compound that cannot be sublimed in a high vacuum. The compound was claimed to have been obtained in 8% yield from carbon monoselenide, generated from carbon diselenide in a high frequency discharge, and gaseous tellurium. The infrared spectrum of carbon selenide telluride was recorded. No details about the reaction conditions were reported  

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Carbon Oxid Telluride/Sulfid Telluride/Selenid Telluride etc. 

Wohler (182812) thought he had prepared the selenide, telluride, arsenide and phosphide by fusing with the respective elements hut his observations have not been confirmed. Beryllium has probably never been obtained in combination with hydrogen although Winkler, (1891 3) thought he had produced a hydride. Beryllium unites directly with carbon, boron and silicon at the heat of the electric furnace (Ldieau, 1895 2, 1898 7, 1899 ii). It reduces SiCl when heated, (Rauter, 1892 2). 

Although both CdSe and CdS can be deposited in nanocrystaUine form by this nonaqueous deposition, the essentially total insolubility of Te in DMSO prevents the use of the method for deposition of nanocrystalline tellurides (a small amount ofTe can be codissolved with Se and mixed selenide-tellurides with small amounts of Te can be deposited see following section). However, a related method to deposit CdTe has been described by Cocivera and associates [23, 24]. They reacted elemental Te with tri-n-butyl phosphine (TBP), which reacts with Te to form TBP telluride. This compound, together with a Cd salt dissolved in propylene carbonate, allowed cathodic electrodeposition of CdTe. The as-deposited films were reported to be X-ray amorphous, a fact that suggested that they might in fact be nanocrystalline [26]. (Cd,Hg)Te films grown by the same... 

A range of oxides, phosphates, carbonates and elemental nanoparticles can be produced. Of special interest to nanotechnologists are the enzymatically controlled redox changes that result in biomineral formation which are linked to microbial respiration such as dissimilatory metal reduction. This latter process has been shown, for instance, to produce Ag(0) nanoparticles 5-40 pm in size ° (Fig. 2), selenium/selenide/telluride nanospheres and rods (Figs. 3 and 4), Au(0), Pd(0) " as well as Tc(IV) and U(IV) (see also for recent reviews). 

Carbonyl Telluride. Littie is known about carbonyl teUuride [65312-92-7] COTe. It is formed in poor yield by passing carbon monoxide over teUurium at a high temperature. It is less stable than the selenide. 

A process for the gravimetric determination of mixtures of selenium and tellurium is also described. Selenium and tellurium occur in practice either as the impure elements or as selenides or tellurides. They may be brought into solution by mixing intimately with 2 parts of sodium carbonate and 1 part of potassium nitrate in a nickel crucible, covering with a layer of the mixture, and then heating gradually to fusion. The cold melt is extracted with water, and filtered. The elements are then determined in the filtrate. 

One-electron oxidation of organoselenium and organotellurium compounds results in initial formation of a radical cation (equations (19) and (20)). The eventual fate of the radical cation depends on several variables, but is typically a Se(lV) or Te(lV) compound. The scope of this section will be the one-electron oxidation of selenides and tellurides that are not contained in a heteroaromatic compound, and ones in which the Se and Te are bonded to two carbons, rather than to other heteroatoms. Tellurium- and selenium-containing electron donor molecules have been reviewed. 

One of the first series of reports on ultrasonically-enhanced electrosynthesis was by Gautheron, Tainturier and Degrand [69] who used the technique to explore routes to organoselenium and tellurium derivatives. Instead of employing a sacrificial cathode of elemental selenium, their procedure allowed the direct use of selenium powder with carbon cloth as cathode to produce Se and Se. A further benefit was that this method also allowed production of the corresponding tellurium anions. These species could be employed in situ in aprotic solvents such as DMF, THF and MeCN for the synthesis of selenides and tellurides by nucleophilic displacement from haloalkanes. 

Binary Selenides. Most binary selenides are formed by heating selenium in the presence of the element, reduction of selenites or selenates with carbon or hydrogen, and double decomposition of heavy-metal salts in aqueous solution or suspension with a soluble selenide salt, eg, Na2Se or (NH Se [66455-76-3]. Atmospheric oxygen oxidizes the selenides more rapidly than the corresponding sulfides and more slowly than the tellurides. Selenides of the alkali, alkaline-earth metals, and lanthanum elements are water soluble and readily hydrolyzed. Heavy-metal selenides are insoluble in water. Polyselenides form when selenium reacts with alkali metals dissolved in liquid 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. 

Most of the compounds deposited by CD have been sulphides and selenides. Apart from a very few examples of tellurides (and some related teUuride experiments) and with a very few exceptions, discussed at the end of this chapter, what is left is confined to oxides (including hydrated oxides and hydroxides and two examples of basic carbonates.) This chapter deals mainly with these oxides. In addition, as noted in Chapter 3, there are a nnmber of slow precipitations that resnlt in precipitates, rather than films, of varions other componnds, not necessarily semiconductors in the conventional sense. These potential CD reactions, briefly discnssed in Chapter 3, will be somewhat expanded on in this chapter. 

Consequently, the bond is fully saturated for A sp = 0 with a bond order of 1, but it is only partially saturated by the time the gap closes for AEap/2 h = 1 (cf eqn (7.92)) when the bond order equals 0.76. This simple second moment model has been extended to include the compound semiconductors. The resultant values of the bond order are given in Table 7.2. We see that the bonds in tetrahedral carbon and silicon are almost fully saturated, but those in zinc selenide and cadmium telluride are only about 75% saturated due partly to the mismatch in the sp orbitals between chemically distinct atoms. 

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