Chemically activated growth of CuO nanostructures for flexible cold cathode emission (original) (raw)
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Room temperature growth and field emission characteristics of CuO nanostructures
Vacuum, 2017
A variety of CuO nanostructures have been synthesized directly on copper foils by room temperature oxidation of copper through wet chemical method. Alkaline condition necessary for the growth process was maintained by the application of NaOH and NH 3 precursors. pH of the solution and reaction time were selected as the process variables. Formation of CuO was confirmed by X-ray diffraction pattern analysis. Evolution of morphologies of the phases formed was characterized by field emission scanning electron microscopy, leading to elucidation of the growth mechanism. Different types of CuO nanostructures were observed to be formed at different process parameters, selected for the present study. Field emission characteristics of CuO nanorods and CuO nanoflakes were also investigated. Emission current density of CuO nanorods and CuO nanoflakes were determined to be 0.90 mA/cm 2 and 0.48 mA/ cm 2 , respectively. Huge difference in the emission current density indicates that field emission properties of CuO nanostructures are strongly affected by their morphology.
Materials Science in Semiconductor Processing, 2019
Cu 2 O-CuO layers were prepared in situ on copper foam substrates by thermal oxidation at 400°C in air using different pretreatments with acetone, HCl and NaOH. The effect of the pretreatment in the shape and physicochemical properties of the Cu 2 O-CuO layers, as well as in the growth or inhibition of the copper oxide nanostructures was studied, and a growth mechanism is proposed. It was found that the pretreatment modulates the nucleation and growth of the copper oxide nanostructures, being the process with NaOH the most suitable to promote the formation of well-defined nanoneedles, while in the case of the samples pretreated with acetone and HCl, copper oxide layers with irregular shape microstructures were obtained. The composition, structural, morphological and optical properties of the copper oxide structures were determined by X-ray diffraction, scanning electron microscopy, UV-vis diffuse reflectance and photoluminescence spectroscopy. The results showed that in all cases, the presence of both copper oxides, Cu 2 O and CuO was observed, with an optical band gap of 1.0 and 1.3 eV. The copper oxide structures exhibited photoluminescence emission centered at 551 nm, related to the recombination of the electron-hole pairs in the samples. The materials prepared with a NaOH pretreatment showed the lower emission and recombination rate. Moreover, the 3D Cu-Cu 2 O-CuO based materials were evaluated as photocathodes in a 0.5 M Na 2 SO 4 solution and under Xe lamp illumination. The photoelectrode where 1D nanostructures were grown, exhibited the lower resistance to the charge transference in the Nyquist plots, the highest current density in the linear voltammetry and the highest photoresponse in the on-off light experiments. The improved electrical and physicochemical properties of the samples pretreated with NaOH was related to the particular 1D nanoneedle morphology, which promoted higher conductivity and photoresponse, lower resistance to the charge transference and lower recombination of free charge carriers, demonstrating the potential use of these electrodes for photoelectrochemical applications. Finally, this work proved that it is possible to grow well-defined and highly crystalline CuO nanoneedles on copper foam porous substrates through a simple, fast and clean method.
RSC Advances, 2012
Different nanoscale objects of CuO have been synthesized by a simple chemical route where the Cu(OH) 2 nanostructures were first synthesized by the alkaline hydrolysis of Cu(NO 3) 2 ?3H 2 O using NaOH as a base and the synthesized precipitate was subsequently annealed at a temperature of 130 uC. The alkaline content (pH) of the solutions during the hydrolysis process was varied to tailor the morphologies and dimensions of the nanostructures, consequently a series of fascinatingly shaped nanostructures, e.g. seeds, ellipsoidal, rods and leaves were obtained. Topographical characteristics along with the mechanism behind the structural variation have been rationalized by XRD, FTIR, SEM and HRTEM investigations. Optical performance of these samples provided simultaneous emission in the visible bands of blue, green, yellow and red, which were correlated to the size, shape and structural defects of these nano-scaled objects. The toxicity of these nanostructured materials were also put into perspective and it was found that the leaf shaped particles were the most toxic among the various shapes of nano-CuO. Finally the synthesized particles, when applied as nanofluids (water medium) showed their ability to enhance the thermal conductivity of water to a noticeable degree (above 40%) at high temperatures, even at very small concentrations, bespeaking their applicability in cooling fluids.
Plasma-enhanced thermal growth of copper oxide nanostructures on anode of glow discharge setup
Aerospace technic and technology, 2021
Plasma-enhanced growth of copper oxide nanostructures is widely explored in science and manufacturing, since it provides the flexibility, productivity, and cost-effectiveness necessary to meet the growing demands of customers. However, in the field of growth of metal oxide nanostructures, thermal methods still prevail in plasma methods in spite of long production time up to ten hours. Radiofrequency and microwave plasma sources were applied to grow CuO nanostructures, which are of high interest in various branches of industry, and allowed obtaining a large variety of the nanostructures, and nanowires in particular. At that, high price of the equipment limits the implementation of the results and urges to find cheaper plasma-enhanced method of growth. For this purpose, a common glow discharge plasma setup was engaged to grow the nanostructures in an oxygen atmosphere on surfaces of samples installed on the anode of the electric circuit designed to sustain the glow discharge. An addit...
CuO nanostructures on copper foil by a simple wet chemical route at room temperature
Uniform CuO nanostructures have been synthesized on copper foil substrates by oxidation of Cu in alkaline condition by a simple wet chemical route at room temperature. By controlling the alkaline condition (pH value) different CuO nanostructures like nanoneedles, self-assembled nanoflowers and staking of flake-like structures were achieved. The phase formation and the composition of the films were characterized by X-ray diffraction and energy dispersive analysis of X-ray studies. X-ray photoelectron spectroscopic studies indicated that the samples were composed of CuO. The morphologies of the films were investigated by scanning electron microscopy. A possible growth mechanism is also proposed here. Band gap energies of the nanostructures were determined from the optical reflectance spectra. The different CuO nanostructures showed good electron field emission properties with turn-on fields in the range 6–11.3 Vmm1 . The field emission current was significantly affected by the morphologies of the CuO films
Growth of Flower-like Copper Oxide Nanostructures by Glow Discharge in Water
In this work, synthesis of flower-like copper oxide nanostructures via a plasma-assisted technique based on glow discharge in liquids has been reported for the first time. The preparation process was carried out in a reactor containing a glass discharge chamber with two copper electrodes immersed in distilled water. The effect of distance between electrodes on the rate of nanopowder production and the structural and morphological properties was investigated by XRD and FESEM. From the XRD patterns of as-grown samples, besides the CuO monoclinic structure, reflection peaks corresponding to Cu2O phase were also observed. It was found that Cu2O phase could be easily eliminated by annealing at 400 °C. FESEM images showed that the flower-like copper oxide nanostructures were composed of nanorods in size of a few hundreds of nanometers in length and 50-80 nm in diameter. In addition, the possible formation mechanism of flower-like copper oxide nanostructures was discussed.
International Journal of Nanomaterials and Biostructures, 2016
Copper oxide (CuO) nanoparticles were synthesized by aqueous solution method using copper acetate as a precursor and NaOH as a stabilizing agent. This gives a large scale production of CuO nanoparticles easily. Characterization of synthesized CuO nanoparticles done by various instrumental techniques such as UV-Vis absorption spectra confirms the thermodynamically stable CuO layers. The fuctional groups identified through the Fouriour Transform Infrared spectroscopy (FTIR) confirms the CuO was capped with Poly Ethylene Glycol (PEG). X-ray diffraction pattern (XRD) reveals single phase monoclinic structure. The average crystalline size of the paerticles found to be 15 nm with debey-Scherrer's formulae. Scanning electron microscopy (SEM) showed the nanocrystals of small sized particles morphology of as prepared CuO nanoparticles. Elemental analysis of CuO nanoparticles done by EDS, which confirms the presence of Cu and oxizen molecules as atomic % is 36.37 and 60.21 respectively. Photoluminescence (PL) showed band edge emission at 398 nm and green emission at 527 nm. The band edge-absorption peak is found to be at 355 nm.