Polychalcogenides polyselenides

We should point out that the temperature effects on emission intensity and photocurrent are completely reversible. Although this result suggests that electrode stability obtains over the duration of the experiments, the properties measured may not be very sensitive to variations in surface or near-surface composition. There is now considerable evidence, in fact, that surface reorganization processes do occur in CdS- and CdSe- based PECs in polychalcogenide electrolytes (17, 21-26). In particular, the occurrence of such an exchange reaction for CdS Te in polyselenide electrolyte would yield CdSe to whose lower band gap... 

The first polychalcogenide complex, K4USes, was obtained by a solid-state reaction. It has a molecular stmcture with a distorted dodecahedral anion, [11(802)4] , which is isostractural with the known peroxoanions [M(02)4]" , where M = V, Nb, Ta, Cr (n = 3) or Mo, W (n = 2). Recently, two additional uranium selenides have been synthesized, MU2Se6 (M = K+, Cs+), using a reactive flux method. The oxidation state of the uranium in these compounds was found to be tetravalent. The selenium has two distinct oxidation states, Se and one similar to a polyselenide network. 

Metal polychalcogenide polymers which have been crystallized directly out of the reaction mixture at room temperature are rare. Recently we published several silver polyselenide compounds which were synthesized according to eq. 1... 

Molten alkali-metal polyselenide fluxes also prove to be useful in the syntheses of unusual quaternaries, here illustrated by the synthesis of the onedimensional polyselenide K3CuNb2Sei2-Both of these polychalcogenides are synthesized at 870° or above. The use of low temperatures (< 450°) is not a necessary condition for the synthesis of metal polychalcogenides, as has been implied. ... 

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