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...

In this work, a highly ordered mesoporous carbon nitride nanorods with 971–1124 m2 g–1 of superhigh specific surface area, 1.31–1.79 cm3 g–1 of ultralarge pore volume, bimodal mesostructure, and 9.3–23 wt % of high N content was prepared via a facile nanocasting approach using SBA-15 as template and hexamethylenetetramine as carbon nitride precursor, and the specific surface area and pore volume as well as N content are strongly dependent on the chosen precursor and pyrolysis temperature. The as-prepared materials were well characterized by HRTEM, FESEM, XRD, BET, Raman, FT-IR, XPS, and the textural structure and morphology were confirmed. The finding breaks through the bottleneck problems for fabricating mesoporous carbon nitride with both ultrahigh surface area and super large pore volume by employing an unexplored hexamethylenetetramine as carbon nitride precursor. The current synthetic strategy can be extended to the preparation of various mesoporous carbon nitride with different textural characteristics by using diverse templates under changeable preparation conditions. The developed mesoporous carbon nitride material with 750 °C of pyrolysis temperature exhibits high superior catalytic performance, ascribed to the promoting effect of nitrogen within the carbon matrix, the rich CO group and defect/edge feature on the surface, small size of graphitic crystallite, as well as the ultrahigh surface area and pore volume. It can also be concluded that the microstructures including bulk and surface structure features and surface chemical properties of the carbon-based materials have a decisive influence on their catalytic performance. The developed material can be employed in various organic transformations such as the base-catalyzed reactions, selective oxidation, dehydrogenation, photocatalysis, and electrocatalysis as well as acting as a novel and efficient candidate for CO2 capture, supercapacitor, purification of contaminated water, and future drug-delivery systems.

Predicting and understanding the cation distribution in spinels has been one of the most interesting problems in materials science. The present work investigates the effect of cation redistribution on the structural, electrical, optical and magnetic properties of mixed-valent inverse spinel NiCo2O4(NCO) thin films. It is observed that the films grown at low temperatures (T < 400 °C) exhibit metallic behavior while that grown at higher temperatures (T > 400 °C) are insulators with lower ferrimagnetic-paramagnetic phase transition temperature. So far, n-type Fe3O4 has been used as a conducting layer for the spinel thin films based devices and the search for a p-type counterpart still remains elusive. The inherent coexistence and coupling of ferrimagnetic order and the metallic nature in p-type NCO makes it a promising candidate for spintronic devices. Detailed X-ray Absorption and X–ray Magnetic Circular Dichroism studies revealed a strong correlation between the mixed-valent cation distribution and the resulting ferrimagnetic-metallic/insulating behavior. Our study clearly demonstrates that it is the concentration of Ni3+ions and the Ni3+–O2−Ni2+ double exchange interaction that is crucial in dictating the metallic behavior in NCO ferrimagnet. The metal-insulator and the associated magnetic order-disorder transitions can be tuned by the degree of cation site disorder via growth conditions.

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.

Vanadium dioxide (VO2) is a compelling candidate for next-generation electronics beyond conventional silicon-based devices due to the exhibition of a sharp metal–insulator transition. In this study, in order to realize functional VO2 film for flexible electronics, the growth of VO2 film directly on a transparent and flexible muscovite via van der Waals epitaxy is established. The heteroepitaxy and structural transition of VO2 films on muscovite are examined by a combination of high-resolution X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. The unique metal–insulator transition of VO2 is further revealed with a change in electrical resistance over 103 and a more than 50% variation of optical transmittance. Furthermore, due to the nature of muscovite, the VO2/muscovite heterostructure possesses superior flexibility and optical transparence. The approach developed in this study paves an intriguing way to fabricate functional VO2 film for the applications in flexible electronics.

Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details.

The metallic interface between insulating LaAlO3 and SrTiO3 opens up the field of oxide electronics. With more than a decade of researches on this heterostructure, the origin of the interfacial conductivity, however, remains unsettled. Here we resolve this long-standing puzzle by atomic-scale observation of electron-gas formation for screening hidden lattice instabilities, rejuvenated near the interface by epitaxial strain. Using atomic-resolution imaging and electron spectroscopy, the generally accepted notions of polar catastrophe and cation intermixing for the metallic interface are discounted. Instead, the conductivity onset at the critical thickness of 4-unit cell LaAlO3 on SrTiO3 substrate is accompanied with head-to-head ferroelectric-like polarizations across the interface due to strain-rejuvenated ferroelectric-like instabilities in the materials. The divergent depolarization fields of the head-to-head polarizations cast the interface into an electron reservoir, forming screening electron gas in SrTiO3 with LaAlO3 hosting complementary localized holes. The ferroelectric-like polarizations and electron–hole juxtaposition reveal the cooperative nature of metallic LaAlO3/SrTiO3.