This paper describes a vapor-phase approach to the facial synthesis of cupric oxide (CuO) nanowires supported on the surfaces of various copper substrates that include grids, foils, and wires. A typical procedure simply involved the thermal oxidation of these substrates in air and within the temperature range from 400 to 700 °C. Electron microscopic studies indicated that these nanowires had a controllable diameter in the range of 30−100 nm with lengths of up to 15 μm by varying the temperature and growth time. Electron diffraction and high-resolution TEM studies implied that each CuO nanowire was a bicrystal divided by a (111) twin plane in its middle along the longitudinal axis. A possible mechanism was also proposed to account for the growth of these CuO nanowires.

CuO Nanowires Can Be Synthesized by Heating Copper Substrates in Air

Recently, great attention has been focused on hydrogen as a potential energy vector and on the use of water-splitting technology as a clean and renewable means to generate hydrogen using solar energy. Numerous attempts have been made to develop photo-catalysts that work not only under UV light but also under visible-light illumination to efficiently utilize solar energy. One of the most well-known photo-catalysts used in the past forty years is TiO 2 . Despite having excellent characteristics as a photo-catalyst, TiO 2 also has some limitations. This paper presents modification techniques that can be used to improve the drawbacks of TiO 2 , such as the addition of sacrificial agents into the solution. The role of sacrificial agents, such as methanol and several recent achievements by previous researchers have also been included.

Hydrogen from photo-catalytic water splitting process: A review

Uniform and monodisperse CuO nanorods have been synthesized by directional aggregation and crystallization of tiny CuO nanoparticles generated from a solid−liquid arc discharge process under ambient conditions in the absence of any surfactants. Uniform CuO nanorods with sharp ends are formed from tiny nanoparticles via a process that involves the rapid oxidation of Cu nanoclusters, the spontaneous aggregation of CuO nanoparticles, and the Ostawald ripening process. The spontaneous aggregation and oriented attachment of tiny CuO nanoparticles contributed obviously to the formation of these kinds of nanostructures. By choice of suitable reducing agent to prevent the oxidation of Cu nanoclusters, Cu and Cu2O nanoparticles can be selectively synthesized.

Formation of Uniform CuO Nanorods by Spontaneous Aggregation: Selective Synthesis of CuO, Cu2O, and Cu Nanoparticles by a Solid−Liquid Phase Arc Discharge Process

A simple aqueous solution route was introduced for the fabrication of CuO pricky microspheres (CPMs) using CuCl2·2H2O, Na2(C4H4O6)·3H2O and NaOH as starting materials. The CPMs were composed of compressed nanothorns exhibiting tapering feature with tip size of less than 10 nm, and the size of CPMs could be tuned from 100−200 nm to 4−6 μm. The effects of the molar ratios of tartrate anions and NaOH to Cu2+ cations, reagent concentration, and reaction temperature on the products were investigated, showing that the morphology of CPMs was determined by the molar ratio of tartrate to Cu2+ cations and the size was greatly affected by reagent concentration and the molar ratio of NaOH to Cu2+ cations in the precursor solution. The fabrication of CPMs went through rapid nucleation of Cu(OH)2, aggregation and in situ dehydration of Cu(OH)2, oriented-aggregation-based growth, and normal crystal growth of CuO nanothorns. The nucleation and crystal growth were successfully separated by controlled releasing of Cu2+ and...

Fabrication of CuO pricky microspheres with tunable size by a simple solution route

We report the synthesis of different Cu(OH)2 and CuO nanostructures (nanowires, rectangles, seedlike, beltlike, and sheetlike) in a solution phase with high yield at low cost by simple reduction of aqueous solution of copper nitrate (Cu(NO3)2 = 0.2 M) with different alkaline solutions of sodium hydroxide (NaOH = 0.1, 0.25, 0.50, 0.75, and 1.0 M). The morphology of the synthesized nanostructures is significantly influenced by the feeding concentration of alkaline NaOH solution. Cu(OH)2 rectangles and nanowires can be readily obtained by the reduction of Cu(NO3)2 solution with different molar concentrations of NaOH solution and the synthesized nanomaterials get transformed into different nanostructures of CuO by subsequent heat treatment at 80 °C for half an hour. Well-defined rectangle-like structures of hydrated copper hydroxide Cu(OH)2·H2O and different CuO nanostructures, such as seedlike, beltlike, and sheetlike, were synthesized by thermal dehydration of corresponding different shaped and sized Cu(OH)...

Synthesis of Different Cu(OH)2 and CuO (Nanowires, Rectangles, Seed-, Belt-, and Sheetlike) Nanostructures by Simple Wet Chemical Route

We present an investigation of the influence of four dopant lithium concentrations on the electrical properties of CuO. X-ray measurements have revealed a single phase formed up to 4.2 at. % of Li, and a second phase formed, Li2CuO2, in the case of 10.5 at. % of Li concentration. The log(ρ/T) vs 1/T data are better represented by two straight lines than by one and show an initial strong decrease of the conduction activation energies for small contents of Li (<1.7 at. %), which becomes weak for larger contents. The change in slope observed in the resistivity measurements as a function of temperature has also been investigated by calorimetric measurements, revealing a specific heat anomaly which can be associated with the antiferromagnetic order transition.

F. Lanza

Papers

Effects of lithium oxide on the electrical properties of CuO at low temperatures