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Recrystallization of the solid [[Cd.sub.10][S.sub.4][([SC.sub.6][H.sub5]).sub.12] from a solution of pyridine and N, N-dimethylformamide (DMF) results in the formation of the cluster [Cd.sub.32][S.sub.14] [([SC.sub.16][H.sub.5]).sub.36][center dot][DMF.sub.4] as pale yellow cubes. The structure consists of an 82-atom CdS core that is a roughly spherical piece of the cubic sphalerite lattice 12 angstroms in diameter. The four corners of the lattice are capped by hexagonal wurtzite-like CdS units, which results in an overall tetrahedral cluster 15 angstroms in diameter. This cluster dissolves intact in tetrahydrofuran where its absorption spectrum reveals a sharp peak at 358 nanometers at room temperature and its emission spectra show a strong broad band at 500 nanometers., The use of very small molecular clusters as synthetic precursors to bulk, extended solids interests both the physics[1] and chemistry [2] communities. In the particular case of semiconductor materials, the [...]

Reports on the single-crystal structure and optical properties of a large, well-characterized semiconductor molecular cluster. Transport and optical behaviors varying as a function of crystallitic size; Formation of the cluster Cd32S14(SC6H5)36...DMF4; Examining the intrinsic optical properties of a single-sized, 15 angstrom quantum dot without ambiguities from size dispersion or poorly defined surfaces; More.

Maleic anhydride, a precursor to polyester resins, is made by oxidation of n-butane over vanadium phosphate catalysts. This system is of general interest because it is the only heterogeneously catalyzed, alkane-selective oxidation reaction in commercial use. Time-resolved in situ x-ray absorption spectroscopy shows that when either alphaI-VOPO4/SiO2 or (VO)2P2O7/SiO2 catalysts are exposed to n-butane, the rate of maleic anhydride formation is proportional to the rate of decay of V5+ species in the catalyst. Thus V5+ species are kinetically significant for the production of maleic anhydride and not just for the production of by-products. The results also suggest that V5+ species may play a role in the initial hydrogen abstraction from n-butane, the rate-determining step in the reaction sequence. V4+ sites appear to be responsible for by-product formation.

The successful development of digital radiography depends, to a large extent, on the availability of suitable x-ray photoconductors. The x-ray photoconductive nanocomposites reported here combine the advantages of both inorganic and organic compounds. An inorganic compound was finely dispersed in an organic polymer. The inorganic compound, with its large x-ray absorption efficiency, functioned as the x-ray absorber, and the polymer provided good dielectric properties and ease of thin-film preparation. The preparation procedures and the x-ray photoconductive properties of a specific example, a 50 percent by weight nanocomposite of bismuth triiodide and nylon-11, are discussed in detail.

C(60) and liquid bromine react to form C(60)Br(24), a crystalline compound isolated as a bromine solvate, C(60)Br(24)(Br(2))(x), The x-ray crystal structure defines a new pattern of addition to the carbon skeleton that imparts a rare high symmetry. The parent C(60) framework is recognizable in C(60)Br(24), but sp(3) carbons at sites of bromination distort the surface, affecting conformations of all of the hexagonal and pentagonal rings. Twenty-four bromine atoms envelop the carbon core, shielding the 18 remaining double bonds from addition. At 150 degrees to 200 degrees C there is effectively quantitative reversion of C(60)Br(24) to C(60) and Br(2).