In this work, tungsten oxide nanowires were grown directly on a tungsten substrate in 800 °C using thermal evaporation method in a horizontal tube furnace. The effect of growth time on structural, morphological, elemental composition and electrical properties of the tungsten oxide nanostructures was investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS) technique and KIETHLEY 2361 system. Our experimental results show that tungsten oxide nanowires crystalline phase, electrical conductance and density on the substrate surface depend on the growth time. The XRD results showed that tungsten oxide nanowires are synthesized with a cubic WO 3 structure. Moreover, the lattice strain, grain size and dislocation density were obtained in three different growth time. It is noteworthy that by increasing the growth time the crystallinity increases. The FESEM images at different growth times showed that the nanowires on grains begin to germinate when the growth time increases to 6 h. At this time, nanowire structures with 1 µm in diameter and 40 µm in length were formed and continued to grow which caused a change in the morphology. In addition, the XPS results showed that the sample that has grown at longer growth time exhibit two asymmetric W4d5/2 and W4d3/2 peak at 252 and 263 eV which can be assigned to W5+ and W4+ species, respectively. Moreover, the linear I-V curves are obtained and it is found that by increasing the growth time, the conductivity of the sample increases due to increasing number of wires on the sample surface. Finally, the conditions and mechanism of WO 3 nanowire growth are discussed. The results can be used to guide a better understanding about the growth behavior of WO 3 nanowires and can contribute towards the development of novel nanodevices.

Using a direct oxidation method in a horizontal quartz tube, copper oxide nanowires are grown on a Cu substrate. In order to investigate the growth temperature effects on the structural, morphological, electrical, and photocatalytic properties of the copper oxide nanowires, X-ray diffraction, scanning electron microscopy, a KEITHLEY 2361 system, and a homemade photoreactor are used. The X-ray diffraction results show that both CuO and Cu2O phases are formed, and while increasing the growth temperature, the crystallinity is improved and the intensity of most of the diffraction peaks increases. The scanning electron microscopy images at different growth temperatures show that the number, density, and length of the copper oxide nanowires on pre-formed micro-scaled grains increase, when the growth temperature increases to 700°C and sharper nanowires with average diameters of 1–3 µm grow on the surface. Also I–V curves show that by raising the growth temperature, the conductivity of the samples increases. In addition, the photocatalytic activities are studied by photocatalytic degradation of Congo red dye, and based on these results, the sample grown at 700°C with the highest number and density of the nanowires showed the best photocatalytic performance and electrical conductivity. The results can be used to guide better understanding of the growth behavior of copper oxide nanowires and can be useful for the development of novel photocatalytic nanodevices.

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