Photoelectrochemical behavior of n-type Si(111) electrodes coated with a single layer of graphene.

The behavior of graphene-coated n-type Si(111) photoanodes was compared to the behavior of H-terminated n-type Si(111) photoanodes in contact with aqueous K3[Fe(CN)6]/K4[Fe(CN)6] as well as in contact with a series of outer-sphere, one-electron redox couples in nonaqueous electrolytes. The n-Si/Graphene electrodes exhibited stable short-circuit photocurrent densities of over 10 mA cm(-2) for >1000 s of continuous operation in aqueous electrolytes, whereas n-Si-H electrodes yielded a nearly complete decay of the current density within ~100 s. The values of the open-circuit photovoltages and the flat-band potentials of the Si were a function of both the Fermi level of the graphene and the electrochemical potential of the electrolyte solution, indicating that the n-Si/Graphene did not form a buried junction with respect to the solution contact.

Resolution of enantiomers of a series of chiral alkoxy-modified phthalocyaninato nickel(II) complexes by enantioselective HPLC.

We have resolved the enantiomers of a series of chiral modified metallophthalocyaninato complexes of nickel bearing alkoxy groups at the 14 and 28 positions on what would otherwise be a normal phthalocyaninato ligand and conforming to the general formula [14,28-(RO)(2)Pc]Ni(ii), where R = Me, Et, or n-Pr. The complex for which R = n-Pr is reported here for the first time. Resolution of the enantiomers of these complexes was accomplished via HPLC utilizing an immobilized carbohydrate-based stationary phase, resulting in baseline resolution of peaks corresponding to enantiomers of the complexes, with R(s) values in excess of five.

Screw dislocation-driven growth of two-dimensional nanoplates.

We report the dislocation-driven growth of two-dimensional (2D) nanoplates. They are another type of dislocation-driven nanostructure and could find application in energy storage, catalysis, and nanoelectronics. We first focus on nanoplates of zinc hydroxy sulfate (3Zn(OH)(2)·ZnSO(4)·0.

Mechanism and kinetics of spontaneous nanotube growth driven by screw dislocations.

Single-crystal nanotubes are commonly observed, but their formation is often not understood. We show that nanotube growth can be driven by axial screw dislocations: Self-perpetuating growth spirals enable anisotropic growth, and the dislocation strain energy overcomes the surface energy required for creating a new inner surface forming hollow tubes spontaneously. This was demonstrated through solution-grown zinc oxide nanotubes and nanowires by controlling supersaturation using a flow reactor and confirmed using microstructural characterization.

Element-specific magnetometry of EuS nanocrystals.

A soft x-ray absorption and x-ray magnetic circular dichroism (XMCD) study of the ferromagnetism in solution-grown EuS nanocrystals (NCs) is reported. The absorption edges of Eu M(5) and M(4), S K, O K, and P K were probed to determine elementally specific contributions to the magnetism of EuS NCs. Differential spin absorption was observed by XMCD at the Eu M(5,4) edges confirming the presence of a magnetic moment on the Eu(2+) 4f shell.

Formation of PbS nanowire pine trees driven by screw dislocations.

The basic characteristics of nanowire growth driven by screw dislocations were investigated by synthesizing hierarchical lead sulfide (PbS) nanowire "pine trees" using chemical vapor deposition of PbCl(2) and S precursors and systematically observing the effects of various growth parameters, such as hydrogen flow, temperature, pressure, and the growth substrates employed. Statistical surveys showed that the growth rate of the dislocation-driven trunk is about 6 mum/min and that of the vapor-liquid-solid (VLS) driven branch nanowire is about 1.2 mum/min under the typical reaction conditions at 600 degrees C, 900 Torr, and a hydrogen flow rate of 1.

Engineered nanomaterial transformation under oxidative environmental conditions: development of an in vitro biomimetic assay.

Once released into the environment, engineered nanomaterials may be transformed by microbially mediated redox processes altering their toxicity and fate. Little information currently exists on engineered nanomaterial transformation under environmentally relevant conditions. Here, we report the development of an in vitro biomimetic assay for investigation of nanomaterial transformation under simulated oxidative environmental conditions.

Dislocation-driven nanowire growth and Eshelby twist.

Hierarchical nanostructures of lead sulfide nanowires resembling pine trees were synthesized by chemical vapor deposition. Structural characterization revealed a screwlike dislocation in the nanowire trunks with helically rotating epitaxial branch nanowires. It is suggested that the screw component of an axial dislocation provides the self-perpetuating steps to enable one-dimensional crystal growth, in contrast to mechanisms that require metal catalysts.

Hyperbranched PbS and PbSe nanowires and the effect of hydrogen gas on their synthesis.

We report a chemical vapor deposition (CVD) synthesis of hyperbranched single-crystal nanowires of both PbS and PbSe using PbCl2 and S/Se as precursors under hydrogen flow. Multiple generations of nanowires grow perpendicularly from the previous generation of nanowires in an epitaxial fashion to produce dense clusters of a complex nanowire network structure. The flow rate and duration of the hydrogen co-flow in the argon carrier gas during the CVD reactions are found to have a significant effect on the morphology of the PbS/PbSe grown, from hyperbranched nanowires to micrometer-sized cubes.

Synthesis and properties of single-crystal FeSi nanowires.

We report for the first time the chemical synthesis of free-standing single-crystal nanowires (NWs) of FeSi, the only transition-metal Kondo insulator and the host structure for ferromagnetic semiconductor Fe(x)Co(1-x)Si. Straight and smooth FeSi nanowires are produced on silicon substrates covered with a thin layer of silicon oxide through the decomposition of the single-source organometallic precursor trans-Fe(SiCl3)2(CO)4 in a simple chemical vapor deposition process. Unlike typical vapor-liquid-solid (VLS) NW growth, FeSi NWs form without the addition of metal catalysts, have no catalyst tips, and depend strongly on the surface employed.

Racemic iron(III) and cobalt(III) complexes containing a new pentadentate "helmet" phthalocyaninato ligand.

Solvothermal reactions of iron(II) acetate tetrahydrate and cobalt(II) acetate tetrahydrate with 1,2-dicyanobenzene in methanol solution result in the formation of racemic six-coordinate iron(III) and cobalt(III) complexes, respectively, with a new bicyclic pentadentate 14,28-[1,3-diiminoisoindolinato]phthalocyaninato ligand.