Semiconducting Chalcogenides

4 The reaction between hydrogen peroxide and iodide ions Hydrogen peroxide can react as an oxidant or a reductant. In the titrimetric determination of hydrogen peroxide, it usually reacts as a reductant when a strong oxidant is used as a titrant. In the reaction with iodide, hydrogen peroxide reacts as an oxidant. The iodine produced in this reaction can be reduced by thiosulphate back to iodide. In presence of thiosulphate, the reaction is similar to the reaction in Sec.7.6.1. It was found that molybdates act as catalysts. This fact is the basis of a titrimetric method for determination of the latter ions. 

Prepare a solution of hydrogen peroxide by diluting 25.0 cm (100 volume) (measured by a burette) to 250 cm Use a burette to deliver 50.0 cm of the freshly diluted solution to a conical flask, acidify and titrate against standardised 0.02 M permanganate to the first permanent pink. Repeat and calculate, from the average titre, the concentration of hydrogen peroxide in mol dm .  

Follow the same procedure as in Sec.7.6.1 replacing persulphate by hydrogen peroxide, remembering to add ammonium sulphate to the initial solution to maintain die ionic strength constant. After studying the effects of the concentrations of the reactants and temperature on the rate of reaction, investigate the effect of adding different [molybdate]. 

Metal selenides and tellurides are formed by some metals especially those of group 12 (the zinc group) and these are generally semiconductors which have photocatalytic activity. Some are hydrolysed by water or dilute acids to give H2Se(or H2Te) and the metal hydroxide or salt. The two hydrides have acidic properties and unpleasant smells. 

Many metal sulphides, selenides and tellurides have been prepared either as powders or as thin films. Sulphides like CdS can be also formed in colloidal suspension, whose optical properties depend on their particle size. 

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Preparation of thin films of semiconducting chalcogenides (J.Chem.Educ.6S (1991)872 74(1997)1205). 

Semiconducting chalcogenide nanostructures have received a great deal of attention for application in optoelectronic devices, such as blue laser diodes, light-emitting diodes, solar cells, IR optical windows, optical limiting, and so on [12-17]. To synthesize them as a pure phase is a... 

Se-I 100, 185). These chalcogenide halide glasses belong to the so-called "semiconducting glasses that have attracted much attention in solid-state physics, because of their physical properties (see Section XII,B) they are, however, not treated in this review. 

Rare earth sulfides, selenides, and tellurides show semiconducting properties and have potential for application in thermoelectric generation. Thin film chalcogenides of various rare earths have been prepared by multisource evaporator systems [233]. 

Elhs AB, Kaiser SW, Bolts JM, Wrighton MS (1977) Study of n-type semiconducting cadmium chalcogenide-based photoelectrochemical cells employing polychalcogenide electrolytes. J Am Chem Soc 99 2839-2848... 

Solorza-Eeria O, EUmer K, Giersig M, Alonso-Vante N (1994) Novel low-temperature synthesis of semiconducting transition metal chalcogenide electrocatalyst for multielectron charge transfer Molecular oxygen reduction. Electrochim Acta 39 1647-1653... 

Alonso-Vante N, Tributsch H, Solorza-Eeria O (1995) Kinetics studies of oxygen reduction in acid medium on novel semiconducting transition metal chalcogenides. Electrochim Acta 40 567-576... 

Two extreme formulations can be considered for such metal chalcogenides ME3 with linear E chains (i) [M4+E2 (E )] implying E% dumbbells as structural fragments (d2 > > d ) and semiconducting behaviour or (ii) (M4+E2 Jo[E ]2, implying chains of equidistant E ions d = di) and metallic properties. The former description clearly applies to ZrSe3134 (d =... 

Bhattacharya, R. N. Pramanik, P. 1982. Semiconductor liquid junction solar cell based on chemically deposited Bi2S3 thin film and some semiconducting properties of bismuth chalcogenides. J. Electrochem. Soc. 129 332-335. 

Chain-transfer constants, 25 571t Chain-transfer rate constants, 19 832 Chain-transfer rates, 19 839 Chain transfer to solvent (CTS), 23 385 Chalcanthite, 7 772 Chalcogenide glasses, 12 575, 584 semiconductivity in, 12 587 Chalcogenides acidic, 12 190-191 gallium, 12 359 in photocatalysis, 19 75 plutonium, 19 691 zirconium, 26 641... 

Jaegermann, W., and H. Tributsch (1988), "Interfacial Properties of Semiconducting Transition Metal Chalcogenides", in S. G. Davison, Ed., Progress in Surface Science 29, Pergamon Press, New York. 

It is well known that amorphous chalcogenide semiconducting materials exhibit many kinds of photoinduced phenomena (photodarkening and photocrystalhzation, to mention only a few) for which extensive work is now being carried out because of their fundamental interest [34, 35]. Further, the phenomena have also received attention because of their potential application for optical memories [36]. While there are... 

Since pure mesoporous silica phases does not show any catalytic activity many successful attempts have been made to vary the inorganic composition towards transition metal oxides or metal chalcogenides [5-12], In particular the semiconducting properties of the latter offer a great range of possible applications in materials chemistry. 

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