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Ozin, Geoffrey A. and Malek, Andrzij and Prokopowicz, Richard and Macdonald, Peter M. and Oezkar, Saim and Moller, Karin and Bein, Thomas (1991): Doping and band-gap engineering of an intrazeolite tungsten(VI) oxide supralattice. In: Materials Research Society Symposium Proceedings, Vol. 233: pp. 109-118




New results are presented concerning the topotactic self-assembly, n-type doping and band-gap engineering of an intrazeolite tungsten(VI) oxide supralattice n(W03)-Na56Y, where 0 < η < 32, built-up of single size and shape (W03)2 dimers. In particular it has been found that the oxygen content of these dimers can be quantitatively adjusted by means of a thermal vacuum induced reversible reductive-elimination oxidative-addition of dioxygen. This provides access to new n(W03.x)-Na56Y materials (0 < χ ^ 1.0) in which the oxygen content, structural properties and electronic architecture of the dimers are changed. In this way one can precisely control the oxidation state, degree of η-doping and band-filling of a tungsten(VI) oxide supralattice through an approach which can be considered akin to, but distinct in detail to, that found in the Magneli crystallographic shear phases of non-stoichiometric bulk W03.x . Another discovery concerns the ability to alter local electrostatic fields experienced by the tungsten(VI) oxide moieties housed in the 13Ä supercages of 16(W03)-M36Y, by varying the ionic potential of the constituent supercage M + cations across the alkali metal series. This method provides the first opportunity to fine-tune the band-gap of a tungsten(VI) oxide supralattice. Α miniband electronic description is advanced as a qualitative first attempt to understand the origin of the above effects. The implications of these discoveries are that cluster size, composition and intrinsic electrostatic field effects can be used to "chemically manipulate" (engineer) the doping and band architecture of intrazeolite supralattices of possible interest in quantum electronics and nonlinear optics.