Haohua Li

Synthesis of Indium Nanowires by Galvanic Displacement and Their Optical Properties

Single crystalline indium nanowires were prepared on Zn substrate which had been treated in concentrated sulphuric acid by galvanic displacement in the 0.002 mol L−1In2(SO4)3-0.002 mol L−1SeO2-0.02 mol L−1SDS-0.01 mol L−1citric acid aqueous solution. The typical diameter of indium nanowires is 30 nm and most of the nanowires are over 30 μm in length. XRD, HRTEM, SAED and structural simulation clearly demonstrate that indium nanowires are single-crystalline with the tetragonal structure, the growth direction of the nanowires is along [100] facet. The UV-Vis absorption spectra showed that indium nanowires display typical transverse resonance of SPR properties. The surfactant (SDS) and the pretreatment of Zn substrate play an important role in the growth process. The mechanism of indium nanowires growth is the synergic effect of treated Zn substrate (hard template) and SDS (soft template).

The Modulation of Optical Property and its Correlation with Microstructures of ZnO Nanowires

ZnO nanowires with both good crystallinity and oxygen vacancies defects were synthesized by thermal oxidation of Zn substrate pretreated in concentrated sulfuric acid under the air atmosphere, Ar- and air-mixed gas stream. The photoluminescence spectra reveal that only near-band-edge (NBE) emission peak was observed for the sample grown in the air atmosphere; the broad blue–green and the red-shifted NBE emission peaks were observed for the sample grown in the mixed gas stream, indicating that the sample grown in the mixed gas stream has a defective structure and its optical properties can be modulated by controlling its structure. The high-resolution transmission electron microscope and the corresponding structural simulation confirm that the oxygen vacancies exist in the crystal of the nanowires grown in the mixed gas stream. The ZnO nanowires with oxygen vacancies defects exhibit better photocatalytic activity than the nanowires with good crystallinity. The photocatalytic process obeys the rules of first-order kinetic reaction, and the rate constants were calculated.

Electrochemical Deposition of Nanoparticulate Materials

The reaction of selenous acid with template grown indium nanowires generates a poorly structured indium (I) selenide tubular product. The electron diffraction pattern from the sample exhibited no crystallinity. The Raman spectrum of the deposit is a broad band centred on 160 cm-1 that is not consistent with the known Raman spectra for indium selenides or elemental selenium. Annealing of the deposit yielded a polycrystalline tube structure where the tubes are similar in size to the as-deposited material. SAED of the grains that form these tubes revealed them to be individual indium (I) selenide crystals.