Effect of the Chemical Nature of the Anions on the Electrodeposition of ZnO Nanowire Arrays

Abstract

An investigation of the electrodeposition of ZnO nanowire arrays from the reduction of dissolved molecular oxygen in solutions containing different anions (Cl-, SO4 2-, and CH3COO-) is reported. A significant variation of the diameter (65−110 nm) and length (1.0−3.4 μm) of the nanowires was obtained by changing only the nature of the anions in the solution. Nanowires exhibiting the lowest and highest aspect ratios were obtained in chloride and acetate solutions, respectively. The diffusion of Zn2+ to the cathode and the OH- generation rate were analyzed by cyclic voltammetry. The difference in adsorption behaviors of the different anions on the ZnO surface is proposed as one of the main reasons for the observed differences in the OH- production rate. The ratio between the OH- generation rate and the Zn2+ diffusion to the cathode is proposed as a major parameter in the electrodeposition of ZnO nanowires. Obtained samples were analyzed by X-ray diffraction, and no spurious phases were observed. Thus, changing the chemical nature of the anions in solution allows for the dimensions and the deposition rate of electrodeposited ZnO nanowire arrays to be controlled.

Localized versus delocalized states: Photoluminescence from electrochemically synthesized ZnO nanowires

“…The mean value of the nanowire diameter was estimated from a statistical evaluation of the SEM micrographs. 9 Figure 3͑a͒ compares the low-temperature NBE spectra between 3.30 and 3.34 eV for three arrays of as-deposited ZnO nanowires with different mean diameters. The spectra are normalized to the maximum of the DB peak.…”

“…The error bar on each spectrum indicates the variation of the intensity at various excitation positions on the ensemble, obtained due to dispersion in nanowire diameter in each sample. 9 The average diameter d of the nanowires on each array is given in the figure. For smaller diameters, we observe an increasing contribution of the D emission band to the PL spectrum.…”

“…The electrochemical deposition ͑ECD͒ of ZnO at temperatures below 100°C, based on the reduction of dissolved molecular oxygen in aqueous solutions containing Zn 2+ ions, 5 has recently shown promising results in obtaining arrays of single crystalline ZnO nanowires with tailored dimensions. [6][7][8][9] Because of the aqueous environment, the limited purity of the involved chemicals and the low growth temperatures ͑especially when compared to typical growth temperatures used for vapor-phase epitaxial methods͒ is not a priori clear how the nanowire material compares to that of nanowires synthesized by, e.g., high-temperature vaporliquid-solid processes. 10 However, a detailed knowledge of the microscopic processes governing the optical and electronic properties of chemically synthesized nanowires is mandatory to understand, tailor, and optimize any optoelectronic device based on such nanowires.…”

(Research Award of the Energy and Technology Division) (Photo)Electrochemistry in the Service of Solar Energy Conversion

“…Our work in this area has spanned over several years, with focus on different types of materials pertinent to solar energy conversion. Thus, early work in II-VI films [33][34][35][36] led to studies of related compounds such as copper containing compounds such as CuSe, related compounds and their phase transitions [37], MoS 2 [38][39][40] and finally to development of new phases of semiconductors such as δ-SnS and Bi 2 S 3 [41,42] or new morphologies of zinc oxide including vertically aligned nanowires [43][44][45][46], nanotubes [47] and arrays of urchin-like by combining electrochemistry and sphere lithography [48].…”

“…ZnO nanostructures with 1D and 3D morphologies are obtained using electrochemical deposition. Adjusting various deposition parameters enable the formation of arrays of vertically aligned ZnO nanowires with controlled dimensions, density and electrical properties [44][45][46]. The concentrations of zinc or chloride ions in the solution are found to be key parameters.…”