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Based on a W 18O 49nanowire template, iron-substituted W 18O 49nanowires and FeWO 4ferberite flowers have been generated by using mixed FeCl 3and WCl 6at different ratios in a simple solvo-thermal process employing cyclohexanol as the solvent. Detailed characterization by electron microscopy and spectroscopy has shown that increasing the FeCl 3concentration during solvo-thermal synthesis promotes a morphological evolution from the long one-dimensional nanowires of the precursor through short Fe-containing W 18O 49nanowires and two-dimensional platelets to three-dimensional flowers with sixfold symmetry. The driving force for these transformations is attributed to Fe inclusion in the W 18O 49template at low Fe concentrations, which introduces internal stresses to the W 18O 49nanowires. At high Fe concentrations, close to the stoichiometric composition of FeWO 4, the formation of the flower is triggered by the intrinsic sixfold symmetry of crystalline ferberite, via a combination of initial nanoblade nucleation and the competing self-assembly of neighboring parallel nanoblades. A similar solvo-thermal process has also been successful in the synthesis of MnNb 2O 6bronze flowers, which exhibit structures with a morphology resembling a purposely carved microgear. Photoluminescent and magnetic properties of the products are also investigated. [ABSTRACT FROM AUTHOR]

Low-temperature magnetic properties of hematite nanorods, prepared by both iron−water vapor reactions (sample 1) and hydrothermal methods (sample 2), were studied by superconducting quantum interference device (SQUID) magnetometry. The Morin transition temperature was found to be 122 K in hematite nanorod sample 1, and an unexpected phenomenon was found under an applied field of 10 Oe. These nanorods (sample 1) show an abrupt decreaseof the magnetic susceptibility at ca. 122 K, contrary to the abrupt increasenormally attributed to the Morin transition in bulk hematite. The origin of this phenomenon can be traced to the probable coherence of the one-dimensional shape anisotropy with the magnetocrystalline anisotropy. In contrast, no obvious Morin transition was found in hematite nanorod sample 2. [ABSTRACT FROM AUTHOR]

A novel class of chiral melamine derivatives has been designed and synthesized. The ability of these compounds to perform chiral recognition toward 19 natural chiral α-amino acids has been investigated by electrospray ionization tandem mass spectrometry for the first time. The enantioselectivities of these new chiral selectors are encouraging. To elucidate some mechanism and regularity in the chiral recognition process using chiral melamine derivatives as chiral selectors, the effect of different noncovalent interactions caused by various chiral or achiral moieties in melamine derivatives on the chiral recognition in the gas phase has been studied at the same time. The result shows that electrostatic, hydrogen bond, π-π stacking, and steric interaction between selector and analyte play important roles in the association and enantioselective recognition of amino acids with the chiral melamine derivatives as chiral selectors. Enantiodiscrimination for analytes with different structures and properties could be improved by modifying substituents in melamine derivatives on purpose. [ABSTRACT FROM AUTHOR]