Chalcogenide ion

InSCl, InSBr, InSeCl, and InSeBr are isotypic, and crystallize in the hexagonal CdCU lattice type. The halide and chalcogenide ions are statistically distributed among the Cl sites. As in CdClj, the bonding within the InYs Xa/a octahedra should be predominantly ionic 162). 

Claes P, Dewilde Y, Glibert J (1988) Chemical and electrochemical behaviour in molten alkali hydroxides Part II. Electrochemistry of chalcogenide ions in the molten NaOH + KOH (49 moI%) eutectic mixture. J Electroanal Chem 250 327-339... 

De Marco R, Pejcic B, Prince K, van Riessen A (2003) A multi-technique surface study of the mercury(ll) chalcogenide ion-selective electrode in saline media. Analyst 128 742-749 Pejcic B, De Marco R (2004) Characterization of an AgBr-Ag2S-As2S3-Hgl2ion-selective electrode membrane a X-ray photoelectron and impedance spectroscopy approach. Appl Surf Sci 228 378-400... 

CsFeo.72Agi.28Te2,1053 and Cs2Ag2ZrTe4. The latter has a structure that comprises 2D slabs of Ag- and Zr-centered tetrahedral separated by Cs+ cations.1054 Gas-phase silver chalcogenide ions of the type [Ag2 i E ] (E = S, Se, Te) with < 14 have been investigated by laser-ablation Fourier transform ion cyclotron resonance mass spectrometry.1055... 

However, for chalcogenide compounds (metal sulfides, selenides and tellurides etc.) the potential across the compact layer is determined by the concentration of hydrated chalcogenide ions so that the flat band potential does not necessarily depend on pH. 

This chapter deals with the methods of synthesis, characterization, and growth mechanisms of well-defined uniform particles of metal sufides and selenides formed by direct reaction of metal ions with the chalcogenide ions, released from thioacetamide or selenourea in dilute solutions, or supplied continuously from outside in the form of a high concentration of sulfide ions. 

The formation of the film, based on the formation of chalcogenide ions, can occur by two fundamentally different processes. We continue to use CdS as the example. 

The chalcogenide precursors possess many talents. Apart from forming the chalcogenide ions, they also form complexes with metal ions. As noted at the beginning of this section, and ignoring the distinction between ion-by-ion and hydroxide cluster mechanisms treated previonsly, CD processes can be divided according to two basic mechanisms participation of free snlphide ions (the... 

The rate-limiting step in CD for the first two mechanisms is almost always formation of the chalcogenide ion. This reaction should be slow otherwise fast, homogeneous precipitation of the metal chalcogenide will occur with little fihn formation. (Even rapid precipitation can lead to a film however, this film will be extremely thin and in most cases not visible.) Almost all the literature on CD is limited to sulfides (mostly), selenides, and oxides (including hydrated oxides and hydroxides). Anion-forming reactions are described in this section. 

All these results show that Cd(OH)2 colloids do adsorb on a substrate (either under conditions where Cd(OH)2 is present in solution or, according to the studies of Rieke and Bentjen and Ortega-Borges and Lincot [48], even when it is not present in solution but under solution conditions close to solid hydroxide formation). The induction period when no deposition is seen in the hydroxide-cluster deposition therefore is understood to mean that a fast and nongrowing Cd(OH)2 adsorption has occurred, which is too fast and/or too httle to measure by the experimental methods used to make the kinetic curves, and that only when the hydroxide starts to convert into the chalcogenide, by reaction of the slowly formed chalcogenide ion with the hydroxide, does real film formation proceed. 

Thiosulphate and sulphite are sufficiently reducing to reduce Cu to Cu. Therefore the Cu in solutions of Cu containing sufficient thiosulphate, seleno-sulphate, or sulphite should be predominantly in the monovalent form. This would lead to the expectation that the main product will be something close to Cu2S(e). While this is often the case, CuS(e) is deposited in some cases. However, it is arguable whether this reduction of Cu is, in fact, important in practice. The reason is based on an XPS study that showed that Cu in its compounds with S, Se, and Te is normally in the monovalent state it is the chalcogenide ion (or polyion) that is believed to change oxidation states in these compounds [41]. 

For the ion-by-ion reaction, nucleation is generally slower and the density of nuclei smaller. Additionally, growth occurs (ideally) only at a solid surface therefore nucleation is confined to two dimensions, in contrast to three dimensions for the cluster mechanism. The crystal growth may terminate when adjacent crystals touch each other or by some other termination mechanism, e.g., adsorption of a surface-active species. These factors should be valid regardless of whether the mechanism proceeds via free chalcogenide ions or by a complex-decomposition mechanism. 

One example is the tertiary bond found in the wurtzite structure of ZnO (67454). All members of the Zn chalcogenide series crystallize with structures based on the close packing of the chalcogenide ions, with Zn occupying half the tetrahedral cavities. The higher members, ZnSe and ZnTe (31840), crystallize with the cubic sphalerite structure while ZnO crystallizes with the hexagonal wurtzite structure. ZnS (60378, 67453) is known in both forms. 

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