Synthesis and Characterization of Zinc Oxide (ZnO) Nanowire

Abstract

Nanowires are structures that have a lateral size constraint to tens of nanometers or less and an unconstrained longitudinal size. The syntheses and characterization of ZnO nanowire with hexagonal structure was successfully achieved using chemical bath deposition technique. The nanowires obtained were further characterized by scan electron microscope (SEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and spectrophotometer. The SEM micrographs revealed the morphology of ZnO nanowires with diameter 170.3 nm and 481 nm. This revealed that the pH 8.1 of the bath solution and the optimized value form ZnO nanowires with hexagonal shape at top surface. The XRD pattern of the samples revealed ZnO nanowire have hexagonal crystallite structure. Where upon the crystallite size supported increased annealing temperature (0.536 nm, 0.541 nm and 0.557 nm at 100°C, 150°C and 200°C respectively). The EDX analysis revealed the elemental compositions of samples and confirmed the presence of Zn and O2. The results of the optical analysis showed that ZnO nanowire have high absorbance in the ultraviolet and infrared regions with high transmittance in the visible region. The absorbance of the nanowire increases with increasing annealing temperature. Its high absorbance in the ultraviolet region suggest it applicability as solar harvester for trapping solar energy, used for photovoltaic panel with capacity to converting sunlight radiation directly to electricity for commercial or industrial purposes.

Facile growth of high transmittance ZnO micro-rod clusters on indium tin oxide by a wet-chemical synthesis method

“…40 It is well known that supersaturation is a prerequisite for crystal growth in solution and is intimately connected with growth processes involved in the evolution of crystal morphology. 41 In general, Zn (II) ions are solvated by water and exist as monomeric hydroxyl species, such as Zn(OH À ) (aq), Zn(OH) 2 (aq) and Zn(OH) 2 -(aq). 41 The ZnO formation mechanism involves two steps: (1) nucleation, resulting from the decomposition of clusters of molecules with increasing temperature, and (2) particle growth, resulting from heterogeneous reactions, wherein particles combine to form nuclei on the substrate.…”

“…41 In general, Zn (II) ions are solvated by water and exist as monomeric hydroxyl species, such as Zn(OH À ) (aq), Zn(OH) 2 (aq) and Zn(OH) 2 -(aq). 41 The ZnO formation mechanism involves two steps: (1) nucleation, resulting from the decomposition of clusters of molecules with increasing temperature, and (2) particle growth, resulting from heterogeneous reactions, wherein particles combine to form nuclei on the substrate. 42 However, because no seed layer is formed on the substrate before synthesis, the rods are deposited on the ITO surface as clusters.…”

“…40 It is well known that supersaturation is a prerequisite for crystal growth in solution and is intimately connected with growth processes involved in the evolution of crystal morphology. 41…”

ZnO nanowires growth direction and parameters affecting their surface morphology

“…Igori Wallace [30] confirmed the ZnO nanowire shape changing with pH raising from 8.1 to 9 and 10 from hexagonal shape to tapered flower-like shape, respectively. They referred this change to the competition between growth and erosion.…”

“…) complexion in alkaline medium. The reaction that occurs in the bath is shown in the chemical equations [30]: Decomposition reaction:…”