1D metal-oxide nanostructures have attracted much attention because metal oxides are the most fascinating functional materials. The 1D morphologies can easily enhance the unique properties of the metal-oxide nanostructures, which make them suitable for a wide variety of applications, including gas sensors, electrochromic devices, light-emitting diodes, fi eld emitters, supercapacitors, nanoelectronics, and nanogenerators. Therefore, much effort has been made to synthesize and characterize 1D metal-oxide nanostructures in the forms of nanorods, nanowires, nanotubes, nanobelts, etc. Various physical and chemical deposition techniques and growth mechanisms are exploited and developed to control the morphology, identical shape, uniform size, perfect crystalline structure, defects, and homogenous stoichiometry of the 1D metal-oxide nanostructures. Here a comprehensive review of recent developments in novel synthesis, exceptional characteristics, and prominent applications of one-dimensional nanostructures of tungsten oxides, molybdenum oxides, tantalum oxides, vanadium oxides, niobium oxides, titanium oxides, nickel oxides, zinc oxides, bismuth oxides, and tin oxides is provided. FEATURE ARTICLEpoint lower but the resistivity higher, so the thermal and chemical stability of the 1D metal-oxide nanostructures may be weakened. In other words, overheating caused by the passage of high currents through the nanodevices or nanoelectronics can easily burn the 1D metal-oxide nanostructures causing them to break. Ideally the 1D metal-oxide nanostructures used for the nanodevices or nanoelectronics are expected to be identical in shape, uniform in size, perfect in crystalline structure, and easy in taking apart, and have no morphological defects and a consistent chemical composition. However, control of the morphology, shape, size, crystalline structure, and chemical composition of the 1D metal-oxide nanostructures remains a challenge in the development of 1D controllable synthesis methods.A number of physical and chemical methods have been use to achieve the goals of identical shape, uniform size, perfect crystals, no defects, and homogenous stoichiometry in the synthesis of ideal 1D metal-oxide nanostructures. In Section 2, we introduce some of the synthesis techniques for the production of various 1D metal-oxide nanostructures, covering the theoretical and experimental aspects of recent developments, such as 1D nanostructure design, processing, modeling, and fabrication. In Section 3, we present several growth mechanisms for the growth of 1D metal-oxide nanostructures. Since such 1D nanostructures possess a highly anisotropic morphology, they preferentially grow along one particular crystalline direction to form the 1D morphology. This anisotropic growth is strongly dominated by internal and external stresses, such as easy-growth lattice-planes and template confi nement, respectively. In Section 4, we provide a comprehensive review of a variety of 1D metal-oxide nanostructures, including tungsten oxides, molybdenum oxides, ta...

One-dimensional (1D) MoO2 nanorods in the form of a large-area array and nanobranched structure were prepared by hot-filament metal–oxide vapour deposition at low and high pressures in atmospheric argon flows respectively. The x-ray diffraction (XRD) patterns of both as-synthesized samples show that the 1D MoO2 nanorods are monoclinic crystals in space group P 21/c. The Raman spectrum of the large-area array of 1D MoO2 nanorods appears to be the same as that of a two-dimensional (2D) MoO2 thin film. The Raman spectrum of the nanobranched structure of 1D MoO2 nanorods showed a downshift and asymmetric broadening of the Raman first-order TO peak when compared with the bulk (q = 0) mode. The Raman shift and broadening were attributed to phonon confinement effect in the 1D nanorods. The in situ Raman spectra of laser-induced oxidation of the nanobranched structure of 1D MoO2 nanorods demonstrate that they can be oxidized easily and more strongly than the 3D bulk MoO2 powder.

Bismuth (Bi) thin films of various microstructures were synthesized by thermal evaporation at varying substrate temperatures. The substrate temperature strongly affects the surface morphology and crystalline orientation of the Bi thin films. Peak shift and broadening of the Raman bands (Eg and A1g modes) observed with an increase in substrate temperature can be attributed to the phonon confinement and compressive stress effects. The Bi thin film depicts a laser-induced oxidation and phase transition as a function of varying laser power. Photoluminescence spectra show visible–near infrared broadband emission for polycrystalline Bi thin film prepared at high substrate temperature. This result indicates that polycrystalline Bi thin film can be a promising candidate for broadband optical fibre amplifiers and tunable lasers.

We report the synthesis of one-dimensional (1D) Bi(2)O(3) nanohooks by the oxidative metal vapor phase deposition technique. Surface morphology observations confirm the formation of 1D nanohooks with nanoparticles at their tips. Structural analysis by x-ray diffraction (XRD) and transmission electron microscopy (TEM) reveals the crystalline nature of the 1D nanostructure. Elemental analysis confirms that the 1D nanohooks consist of only elements Bi and O. The XRD study suggests that the synthesized product is of two phases (α- and β-Bi(2)O(3)) with monoclinic and tetragonal crystal structures respectively. The phonon vibration modes corresponding to Bi(2)O(3) are determined by Raman scattering. A broadband visible photoluminescence (PL) is observed in the wavelength region 500-900 nm, also indicating the extension of luminescence into the near-infrared region. The existence of broadband visible emission can be attributed to the existence of defect/impurity states induced by oxygen vacancies.

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