Papers by Keyword: Nanowires

Abstract: Recently, copper (Cu) and silver (Ag) nanowires have been widely employed as conductive fillers in flexible electronic devices due to their high aspect ratios leading to the formation of conductive networks in a polymeric substrate. This study combined Cu and Ag as a 1-dimensional nanostructures through galvanic replacement with a core-shell configuration. The effects of the galvanic replacement factors on the Cu-Ag core-shell nanostructures morphology was studied by varying the reaction time, temperature, and Ag concentration. SEM images show a more extensive Cu dealloying and Kirkendall voiding with longer reaction times, resulting in the Cu core dissolution. Homogenous nucleation of Ag occurs at higher reaction temperatures and Ag concentrations, producing separate Ag particles.

Abstract: Using a facile hydrothermal method, ZnO nanomaterials with various morphological structures (nanowires, nanodiscs, and nanostars) were produced. An investigation was conducted into the relationships between the exposed polar facets and the photocatalytic activities. Based on XPS, Pl, and structural analysis, it was discovered that the exposed facets’ chemsorption ability of the different ZnO nanomaterials with different morphologies plays a vital role in their photocatalytic properties. Zinc-terminated surfaces had the highest chemsorption ability and consequently the ZnO nanodiscs with the highest fraction of exposed Zinc-terminated facets were the ideal photocatalysts from the tested morphologies. This work emphasises the important influence of rational control over the nanomaterial morphology on its physical and chemical properties and therefore on its performance in various practical applications.

Abstract: Preparation of boride by chemical vapor deposition (CVD) is sensitive to oxygen, subtle changes in oxygen concentration during the deposition of ZrB₂ can induce the formation of Zirconium dioxide (ZrO₂) with a novel nanoplate-stacked structure and nanowire structure. The ZrO₂ nanostructure changed with - oxygen concentration. Nanowires with uniform size of 50-100 nm in diameter and over 100 μm in length were obtained at high oxygen concentration, while highly-ordered nanoplate arrays were obtained at low oxygen concentration. Both of these nanostructures were grown in situ on the surface of ZrB₂-coating. In this paper, the preparation method of novelty ZrO₂ nano-structures grown in situ was provided, the morphologies and compositions of the nano-structural ZrO₂ were characterized and the formation mechanism was proposed, which also provides experimental basis for the industrial morphology control of ZrB₂ deposited by CVD method.

Abstract: A well-controlled multistage hydrothermal technique was developed to synthesise hierarchical zinc oxide (ZnO) nanomaterials with a high surface-to-volume ratio. Hierarchical ZnO nanomaterials, hierarchical nanowires (HNWs) and hierarchical nanodiscs (HNDs), assembled from initial mono-morphological nanomaterials, ZnO nanowires, and ZnO nanodiscs respectively were prepared by sequential nucleation and growth following a hydrothermal course. The hierarchical nanomaterials composed of one-dimensional nanowire building blocks were obtained by introducing zinc nitrate as a source of zinc ions during the second growth phase. In comparison to their initial monomorphological counterparts, the prepared HNWs and HNDs showed superior photocatalytic performances. The improvement in the photocatalytic performance was ascribed to the reduction in dimensionality, the ultrahigh surface-to-volume ratio, the expanded proportion of the exposed polar area, and the creation of nanojunctions between the secondary nanowires and initial ZnO nanowires or nanodiscs. This work paves the way for the low-cost, large-scale, and low-temperature production of ZnO nanomaterials with superior photocatalytic properties.

Abstract: In this research work, brass (Cu - 37.2 wt% Zn) and Cu (99.9 wt%) wires having diameters of 200 μm were thermally oxidized in N₂ containing 5% O₂, at a flow rate of 200 sccm and in the ambient atmosphere respectively, to support the growth of nanowires. The oxidation temperature was varied from 300 to 600 °C and the as-grown nanowires were characterized by field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDX) spectroscope, and transmission electron microscope (TEM). Results show that ZnO and CuO nanowires are formed on brass and Cu wires, respectively. The ZnO nanowires are branched and CuO nanowires are straight with tapered morphology. ZnO nanowires having hexagonal wurtzite structure grow along the <1 1 0> directions whereas, CuO nanowires have monoclinic structure. A diffusion based stress induced model is proposed to explain the growth mechanism of the nanowires. Thermal oxidation process is a suitable platform for synthesizing ZnO and CuO nanowires, which can be used in in-situ device fabrication.

Abstract: ZnO nanorods and ZnO nanowires were obtained using solutions of zinc chloride and zinc acetate dihydrate, respectively, as precursors. The thin films were deposited by ultrasonic spray pyrolysis onto glass substrates at 350 °C and their morphological, structural, and optical properties were investigated. ZnO nanostructures morphologies were observed by SEM and images showed that a large amount of ZnO nanorods and nanowires were deposited onto the full substrates surfaces. The films have polycrystalline nature and hexagonal wurtzite structure with (002) and (101) preferential orientations for ZnO nanorods and nanowires, respectively. The crystallite size was found to be in the range of 30 nm. The films exhibit an optical transparency in the visible region of about 60 % for ZnO nanowires and 30 % for ZnO nanorods. The different ZnO films were used as photocatalysts to study the photodegradation of methyl green dye induced by UV light. ZnO nanorods exhibited higher photodegradation efficiency and a larger rate constant than ZnO nanowires leading to an improvement from 60 % to 80 % of the degradability of the dye.

Abstract: Technical analysis of the performance optimization of nanospintronics devices based on carbonaceous materials has been presented in this paper. Mathematical formulation of the nanospintronics devices and a brief theory of these devices have been briefly discussed. A qualitative review of some of important nanospintronics based devices has also been given. The paper is expected to be useful to the new entrants in this exciting field, and also for the designers of some novel devices based on use of carbonaceous materials in nanospintronics.

Abstract: With the development of flexible optoelectronic devices, transparent conductive films (TCFs) based on nanowires provide wide concern. The low preparation cost and high-efficiency assembly characteristics make them occupy a very important position in scientific research and industrial application. In practical applications, TCFs in optoelectronic devices often do not need to cover the whole device, but only need to be prepared in part areas. At this time, patterned TCFs need to be prepared. In this paper, four kinds of patterning methods of TCFs are introduced, and the advantages and disadvantages of each method are analyzed.

Abstract: Gallium oxide (Ga₂O₃) nanowires were grown on fused quartz and Si substrates by a vapor transport method of heating gallium metal at 750−1100 °C in a tube of the horizontal furnace. The obtained white colored product has shown to be the Ga₂O₃ nanowires with average diameters ranging from 30 to 80 nm. The optical transmittance spectra indicated that the bandgap energy of Ga₂O₃ nanowire increases as the diameter of nanowire decreases.

Abstract: In this work, germanium nanowires (GeNWs) were fabricated by galvanostatic electrodeposition using In nanoparticles from water solutions at different temperatures. It was found that in the temperature range from 10°C to 60°C there was no significant change in the structure of GeNWs, and the average diameter was about 40 nm. The growth time of GeNWs increases linearly with increasing temperature of the electrolyte solution. However, the structure of GeNW obtained at a solution temperature of 90°C has changed. It was shown that these GeNWs have a core-shell structure: the core is a crystalline Ge phase containing In atoms, and the shell is Ge oxides (hydroxides).