Electrospinning provides a simple approach to fabricating nanofibers and assemblies with controllable hierarchical structures. In this communication, we demonstrate that electrospinning can be combined with calcination to further maneuver the morphology and phase structure of nanofibers. More specifically, single-crystal V2O5 nanorods could be grown on rutile nanofibers by carefully calcining composite nanofibers consisting of amorphous V2O5, amorphous TiO2, and poly(vinylpyrrolidone). The size of the resulting V2O5 nanorods could be conveniently controlled by varying the composition of the nanofibers and/or the calcination temperature. In addition to the nanorod-on-nanofiber hierarchical structure, we believe this approach can also be extended to fabricate other more complex architectures.

Herein, we report the synthesis and photocatalytic properties of novel Bi2O3 nanomaterials. Cubic mesoporous films were produced by coassembly of hydrated bismuth nitrate with a poly(ethylene-co-butylene)-block-poly(ethylene oxide) diblock copolymer, referred to as KLE, while nanofiber mats were produced via electrospinning. We establish that all materials employed in this work are highly crystalline after thermal treatment and that the nanoscale order of the self-assembled samples is further retained. KLE-templated films can readily produce phase-pure β-Bi2O3 with an optical band gap of about 3.4 eV. Calcination of nanofibers, by contrast, leads to the formation of a composite consisting of β-Bi2O3 and trace amounts of the thermodynamically stable α-Bi2O3 phase. We further show the benefits of a mesoporous morphology in heterogeneous semiconductor photocatalysis. KLE-templated β-Bi2O3 films exhibit much greater photocatalytic activity than nanofiber mats and nontemplated Bi2O3 films (prepared under otherwise identical conditions) as well as than KLE-templated anatase TiO2 films on a mass normalized basis. We associate this exceptional activity with (1) the comparatively high BET surface area, which provides for a large number of adsorption sites, and (2) the high phase purity of the more catalytically active β-Bi2O3.

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The new dinuclear nickel-ruthenium complexes [Ni(xbsms)RuCp(L)][PF(6)] (H(2)xbsms = 1,2-bis(4-mercapto-3,3-dimethyl-2-thiabutyl)benzene; Cp(-) = cyclopentadienyl; L = DMSO, CO, PPh(3), and PCy(3)) are reported and are bioinspired mimics of NiFe hydrogenases. These compounds were characterized by X-ray diffraction techniques and display novel structural motifs. Interestingly, [Ni(xbsms)RuCpCO][PF(6)] is stereochemically nonrigid in solution and an isomerization mechanism was derived with the help of density functional theory (DFT) calculations. Because of an increased electron density on the metal centers [Eur. J. Inorg. Chem. 2007, 18, 2613-2626] with respect to the previously described [Ni(xbsms)Ru(CO)(2)Cl(2)] and [Ni(xbsms)Ru(p-cymene)Cl](+) complexes, [Ni(xbsms)RuCp(dmso)][PF(6)] catalyzes hydrogen evolution from Et(3)NH(+) in DMF with an overpotential reduced by 180 mV and thus represents the most efficient NiFe hydrogenase functional mimic. DFT calculations were carried out with several methods to investigate the catalytic cycle and, coupled with electrochemical measurements, allowed a mechanism to be proposed. A terminal or bridging hydride derivative was identified as the active intermediate, with the structure of the bridging form similar to that of the Ni-C active state of NiFe hydrogenases.