Electrochemical fabrication and characterization of lepidocrocite (γ-FeOOH) nanowire arrays

We report on the fabrication of γ-phase iron oxyhydroxide (γ-FeOOH, lepidocrocite) nanowire (nw) arrays within the alumina pores by electrodeposition. An aqueous solution, friendly to alumina matrix, was generated and applied in this study for uniform deposition of γ-FeOOH nw arrays directly through the alumina barrier layer using an alternating current (ac) mode. As-deposited nanowired products were characterized using ⁵⁷Fe Mössbauer spectroscopy (MS), atomic absorption spectrophotometry analysis, field-emission scanning electron microscopy, UV-vis transmission spectroscopy, transmission electron microscopy and X-ray diffraction. The formation of pure lepidocrocite nw arrays in the alumina pores with the average Ø_pore of 45 and 150 nm was verified by transmission MS at cryogenic temperatures.     

Studies of oxidation of iron nanowires encased in porous aluminium oxide template

The transformations of phase composition of iron nanowires deposited into porous alumina template when annealing in the air were studied. The samples of iron nanowires of different diameter (8, 13, 15, 30 nm) were annealed for 1.5 h at temperature up to 600°C. In addition, for nanowires of 15 nm diameter the dependence of phase composition on annealing time was investigated. The phases were determined by applying Mössbauer spectroscopy. New Fe(II) and Fe(III) contributions to Mössbauer spectra were found and those were indentified as caused by the formation of hercynite FeAl₂O₄ and (Fe _x Al_1???x )₂O₃ with small x values (x?≤?0.15). It has been found that though initially the Fe(II) compound forms rapidly, afterwards its formation rate becomes lower than that of Fe(III) and after longer annealing time the Fe(III) content exceeds Fe(II) one.     

Fabrication and phase variation in annealed Cu3Se2 nanowire arrays

We have found for the first time that Cu₃Se₂ nanowired products encased inside the alumina pores by electrodeposition demonstrate the promising nonlinear optical properties in UV-vis-NIR spectra region. Furthermore, the annealing of these products results in the formation of Cu_2−xSe with x depending on the annealing temperature. Optical nonlinearities of as-grown and thermally treated copper selenide nanowire arrays were evidenced using the standard open-aperture Z-scan and laser pump-probe techniques.