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Vertically aligned iron oxide nanobelt and nanowire arrays have been synthesized on a large-area surface by direct thermal oxidation of iron substrates under the flow of O(2). The effects of reactive gas pressure, composition, and temperature have been systematically studied. It was found that nanobelts (width, tens of nanometers; thickness, a few nanometers) are produced in the low-temperature region (approximately 700 degrees C) whereas cylindrical nanowires tens of nanometers thick are formed at relatively higher temperatures (approximately 800 degrees C). Both nanobelts and nanowires are mostly bicrystallites with a length of tens of micrometers which grow uniquely along the [110] direction. The growth habits of the nanobelts and nanowires in the two temperature regions indicate the role of growth rate anisotropy and surface energy in dictating the ultimate nanomorphologies.

Films of aligned crystalline copper sulphide (Cu[sub 2]S) nanowire arrays were grown by using a gas-solid reaction method. By controlling the preparation condition, copper sulphide nanowire arrays with different structural parameters were fabricated. Their field emission characteristics including the total current-applied field characteristics and the distribution of field emission sites are studied and compared using the transparent anode technique. It is found that the turn-on field of the copper sulphide nanowire film relates to the structural parameters of copper sulphide nanowire arrays. Nonlinearity in Fowler-Nordheim plot was observed from film consisting of sparse nanowire arrays with varied field enhancement factor. The physical mechanism accounting for the nonlinearity is discussed. [ABSTRACT FROM AUTHOR]

A novel in situ N and low-valence-state Mo dual doping strategy was employed to significantly improve the conductivity, active-site accessibility, and electrochemical stability of MoO3, drastically boosting its electrochemical properties. Consequently, our optimized N-MoO3− x nanowires exhibited exceptional performances as a bifunctional anode material for both fiber-shaped asymmetric supercapacitors (ASCs) and microbial fuel cells (MFCs). The flexible fiber-shaped ASC and MFC device based on the N-MoO3− x anode could deliver an unprecedentedly high energy density of 2.29 mWh cm−3 and a remarkable power density of 0.76 μW cm−1, respectively. Such a bifunctional fiber-shaped N-MoO3− x electrode opens the way to integrate the electricity generation and storage for self-powered sources. [ABSTRACT FROM AUTHOR]

The porous CoO nanowires have been successfully synthesized via modified template method. A possible growth mechanism governing the formation of such 1D nanowires is proposed. The as-prepared products have been characterized by X-ray Powder Diffraction (XRD), Extended X-ray Absorption Fine-structure (EXAFS), High-resolution Transmission Electron Microscopy (HRTEM) and N adsorption/desorption analysis. Our systematic studies have revealed that the porous CoO nanowires show excellent gas sensing performances, which demonstrate the potential application of the 1D nanostructured CoO in the detection of the ethanol gas as a sensor material. The improved performances are owing to its large specific surface area and porous morphology. [ABSTRACT FROM AUTHOR]

Nanotechnology can be defined as the science and engineering involved in the design, synthesis and application of materials and devices on the nanometer scale. It is not in itself a single emerging discipline, but rather a meeting of several traditional sciences such as chemistry, physics, materials science, biology and engineering to bring together the required expertise needed to develop these new technologies. The unique properties of nanoscale materials provide benefits in remediation, pollution prevention, and efficient use of resources; however, the greatest contribution to green chemistry is likely to be the new manufacturing strategies available through nanoscience. So, the present review mainly focuses on the synthesis of semiconductor CuO nanomaterials from different starting materials by adopting various routes such as vapor-solid, vapor-liquid-solid, solid-liquid, etc. to reveal the morphological features of the precursor. [ABSTRACT FROM AUTHOR]

A morphology-conserved transformation yields Sn@C nanowires (UTP@CW, ∼21 wt% carbon and ∼77 wt% tin) with a high encapsulation density of ultrafine tin nanoparticles in porous carbon nanowires, which exhibit excellent reversible capacities and cycling performance for lithium ion batteries, especially at high current rates. [ABSTRACT FROM AUTHOR]

Films of aligned cupric oxide nanobelts have been prepared in an aqueous solution at room temperature. Field-emission characteristics, including emission-current–applied-field plot and emission site distribution, have been studied using the transparent anode technique. In addition, the temperature dependence of the field-emission characteristics has been studied from room temperature to 750 K. The threshold field for obtaining a current density of 10 µA/cm⊃2 is ∼ 11 MV/m. This decreases with increasing temperature, and at 700 K it is ∼6 MV/m. At a fixed field of 10 MV/m, about a three-orders-of-magnitude increase of the emission current level has been observed. The results show that the cupric oxide nanobelt is a promising candidate for cathode material in a thermoelectric conversion device based on field emission. [ABSTRACT FROM AUTHOR]

Straight crystalline copper sulphide (Cu[sub 2]S) nanowire arrays have been grown by using a simple gas–solid reaction at room temperature. These were demonstrated to exhibit semiconductor properties. Field emission was observed at a field of ∼6 MV/m, and its current-field characteristics deviate from Fowler–Nordheim theory, i.e., showing a nonlinear Fowler–Nordheim plot. The uniform emission from the whole arrays was observed using transparent anode technique, and their variation with applied field was recorded. The emission from individual nanowires was also studied using a field emission microscope, and was found to consist of a number of spatially resolved diffuse spots. Finally, stable emission current at different levels and over time was recorded. These findings indicate that semiconductor nanowires as cold cathode have a potential future, worthy of further comprehensive investigation. The technical importance of using semiconductor nanowires as cold cathode emitter is given. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Creating atomically coherent interfaces can sharpen the physiochemical properties and functionalities of nanomaterials for efficient energy conversion via manipulating the charge flow. While coherent interfaces can be built between transition metal dichalcogenides with structural similarities and weak interlayer van der Waals interactions, it remains challenging to realize interfacial coherency with more generic transition metal chalcogenides via cost-effective wet chemical routes. Here we establish a coherent CdS(010)|CoS(010) interface via in-situ heteroepitaxial growth of CoS nanoflakes onto CdS nanowires. The uniform and oriented distribution of CoS nanoflakes on the CdS nanowires features an interesting "leaves-on-a-branch" nano-architecture with coherent interface and well-aligned energy levels, allowing efficient separation of photoexcited charge carriers. Combined with the outstanding proton reduction kinetics of the CoS "nanoleaves", striking photochemical solar-to-hydrogen conversion performance can be obtained. Our findings provide a viable design strategy of nanojunctions with atomic level coherency and great application prospect in catalysis, nanoelectronics and many others. [Display omitted] ● Atomically coherent CdS(010)|CoS(010) interface was built via heteroepitaxial growth. ● The growth of CoS on the CdS features an interesting "leaves-on-a-branch" structure. ● Unique coherently interfaced junction leads to effective photochemical conversion. ● This work provides a strategy of cost-efficiently constructing coherent interface. [ABSTRACT FROM AUTHOR]

Geometrical light trapping is a simple and promising strategy to largely improve the optical absorption and efficiency of solar cell. Nonetheless, implementation of geometrical light trapping in organic photovoltaic is challenging due to the fact that uniform organic active layer can rarely be achieved on textured substrate. In this work, squarely ordered nanobowl array (SONA) is reported for the first time and [6,6]-phenyl-C-butyric acid methyl ester (PCBM):poly(3-hexylthiophene) (P3HT)-based organic photovoltaic (OPV) device on SONA demonstrated over 28 % enhancement in power conversion efficiency over the planar counterpart. Interestingly, finite-difference time-domain (FDTD) optical simulation revealed that the superior light trapping by SONA originated from optical concentrator effect by nanobowl. Furthermore, aiming at low-cost, solution processible, and resource sustainable flexible solar cells, we employed Ag nanowires for the top transparent conducting electrode. This work not only revealed the in-depth understanding of light trapping by nanobowl optical concentrator, but also demonstrated the feasibility of implementing geometrical light trapping in OPV. [ABSTRACT FROM AUTHOR]

Phase transitions in the Cu2S nanowires have been studied as a function of temperature and pressure. Differential scanning calorimetry (DSC) shows an endothermic process at 101.8 °C upon heating, corresponding to the phase transition from γ-Cu2S (monoclinic) to β-Cu2S (hexagonal) in the bulk (103.5 °C). However, the reverse phase transition was found to be much lower (74.8 °C). X-ray diffraction (XRD) demonstrates that the c-axis of γ-Cu2S is transformed to the c-axis of β-Cu2S owing to the positional disorder of the Cu atoms. Two high-pressure phases of Cu2S have been identified using a diamond anvil cell and the energy-dispersive XRD technique. [Copyright &y& Elsevier]

Abstract: The transition temperatures for the α or β to δ and the δ to liquid phase for α- and β-Bi2O3 nanowires were investigated. We found that there is a size effect for the δ to liquid phase transition but not the α or β to δ phase transition. This is because the δ to liquid phase transition involves bond rupture as well as surface area reduction, whereas the α or β to δ is only solid–solid phase transition, which requires only the reorganization of the bonds. This is the first time the phase transitions of the Bi2O3 nanowires have been investigated and their size effect revealed. [Copyright &y& Elsevier]