Template-assisted electrochemical synthesis of cuprous oxide nanowires

Nanowires of Cu₂O as well as Cu were synthesized within the anodic aluminum oxide templates in an aqueous acidic electrochemical cell. The content of Cu₂O in the copper nanowires was controlled by varying the anodic potential of the pulse-reverse electrolysis and the pH of the electrolyte within a range of 2.0–3.9. For the pH of 2.0, pure Cu nanowires were deposited regardless of the anodic potential. When the anodic potential became higher than the cathodic one, pure Cu₂O nanowires were produced at a pH of 3.9. The growth of Cu₂O nanowires in the acidic electrolyte was ascribed to the local increase of the pH at the pore base, as well as the capacitive barrier layer of the template.     

Surface texture in electrodeposited films of cuprous oxide

The polycrystalline films of Cu₂O, prepared by electrodeposition, consist of grains with well-defined geometrical shapes. The size and the orientation of grains which define the surface texture can be controlled by controlling the deposition parameters. Grains with a size ranging from a few tenths of a micrometer to about 10m and with a preferential orientation of the (1 0 0) or (1 1 1) planes parallel to substrates can be obtained under certain deposition conditions. The effect of pH, bath temperature and the rate of deposition on the orientation and the size of grains is discussed.     

Solution-phase synthesis of smaller cuprous oxide nanocubes

Smaller cuprous oxides (Cu₂O) nanocubes were synthesized by solution-phase method at 160 °C, using ethylene glycol reducing Cu(NO₃)₂·3H₂O with poly(vinylypyrrolidone) (pvp) as capping agent. The Cu₂O nanocubes were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and X-ray powder diffraction (XRD). SEM showed that most of Cu₂O nanocubes were uniform and monodisperse, with the average edge length about 130 nm. The TEM results were consistent with the SEM results. Selected area electron diffraction (SAED) suggested that as-prepared Cu₂O nanocubes were single crystalline. The geometric shape and size of Cu₂O nanoparticles were greatly affected by the presence of PVP and its molar ratio (in repeating unit) relative to copper nitrate, temperature and the concentration of Cu(NO₃)₂·3H₂O. The mechanism of Cu₂O nanocubes formation was also discussed.     

Hydrothermal synthesis of vanadium oxide nanotubes from oxide precursors

Vanadium oxide nanotubes were synthesized as the main product by a direct hydrothermal treatment of oxide precursors and long chain amines as structure-directing templates. The morphology and structure of nanotubes was characterized by powder X-ray diffraction, electron microscopy, and thermal analysis. Nanotubes of high aspect ratio with layered structures were found to grow together in the form of bundles. The paper also discusses the chemistry issues involved in synthesizing nanostructured vanadium oxides.     

Morphology and growth of electrodeposited cuprous oxide under different values of direct current density

The growth of Cu₂O thin films electrodeposited by a two-electrode system with acid and alkaline electrolytes under different values of direct current (DC) densities was investigated. The microstructure of Cu₂O thin films produced in the acid electrolyte changes from a ring shape to a cubic shape with increasing DC density, and the microstructure of Cu₂O thin films produced in the alkaline electrolyte has a typical pyramid shape. The X-ray diffraction results show that Cu₂O thin films can be electrodeposited over a larger current domain than those deposited by a three-electrode system. The growth of Cu₂O thin films is examined under this domain, and the electrocrystallization process of such films is discussed taking into consideration the effect of current density on nucleation, cluster growth, and crystal growth.     

Electrochemical synthesis and photocatalytic property of cuprous oxide nanoparticles

Cuprous oxide (Cu₂O) nanoparticles of 35 nm in crystal size have been successfully synthesized via electrochemical method in alkali NaCl solutions with copper as electrodes and K₂Cr₂O₇ as additive. Photocatalytic degradation of methyl orange (MeO) in aqueous Cu₂O solution was investigated under either ultraviolet (UV) light or sunlight. X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transformation infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–vis) and X-ray photoelectron spectroscopy (XPS) were introduced to characterize the samples. The results indicate that electric current shows no obvious effect on the growth of Cu₂O nanocrystals and that 97% of MeO can be decolorized under UV irradiation for 2 h or under sunlight for 3 h when amount of Cu₂O is 2 g/L. Recycling use of the catalyst revealed that Cu₂O still has a high photocatalytic efficiency when repeatedly used for four times. Cu₂O nanoparticles still kept its cubic crystal phase, but fractionally oxidized to be CuO after the photocatalysis. Compared with the original Cu₂O nanoparticles, there has 1 eV shift of Cu 2p electron and 1.6 eV shift of Cu Auger signals for the Cu₂O powders after four times photocatalysis. Some new peaks can also be observed at 401.1, 237.4 and 170.2 eV in the Cu₂O powders after photocatalysis.     

Cold densification rolling of porous copper strip obtained directly from cuprous oxide perform

Abstract

The densification of porous copper strips obtained from the combined reduction and sintering of cuprous oxide preforms by cold rolling has been discussed. It has been shown that such strips, although containing a relatively large amount of porosity, exhibit no problems during cold rolling and, in general, have good workability. Although it is possible to subject the strip to cold rolling thickness deformations of the order of 75%, without any intermediate annealing, rolling with annealing after every 35–40% cold rolling reduction yields better results. The efficiency of densification and changes in the pore morphology during the cold rolling of the porous strip have also been discussed.

MST/670     

A simple solvothermal reduction route to copper and cuprous oxide

Pure copper nanocrystallites and cuprous oxide nanorods have been synthesized via solvothermal treatment of CuSO₄ or CuSO₄·5H₂O and NaOH in pure ethanol and mixed solution of ethanol and deionized water at 140 °C for 10 h, respectively. Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) were used to investigate the different morphologies of the as-synthesized products. X-ray powder diffraction (XRD) and selected area electron diffraction (SAED) were applied to characterize the composition and crystal phases of the products. It was proposed that the reducibility of ethanol was influenced by temperature and the addition of deionized water in the formation of different phases, which were realized by carefully controlling the experimental conditions.     

Carbon nanotubes grafted on silicon oxide nanowires

In this article, we report the grafting of multi-walled carbon nanotubes on silica nanowires by directly growing nanotubes on the surfaces of the nanowires via chemical vapor deposition (CVD) using ferrocene and xylene as Fe catalyst precursor and carbon source, respectively. The grafted carbon nanotubes are a few micrometers long with diameters of 10 to approximately 30 nm, and grow uniformly along the lengths of the nanowires. The distribution density of the grafted carbon nanotubes on the silica nanowires can be tuned by simply adjusting the CVD growth temperature. Our method provides a simple approach for synthesizing nanometer scale grafted heterostructures between nanotubes and nanowires, which could be used to design and construct high-performance filters, chemical sensors and reinforced composites.     

Green chemistry synthesis of nano‐cuprous oxide

Green chemistry and a central composite design, to evaluate the effect of reducing agent, temperature and pH of the reaction, were employed to produce controlled cuprous oxide (Cu₂ O) nanoparticles. Response surface method of the ultraviolet–visible spectroscopy is allowed to determine the most relevant factors for the size distribution of the nanoCu₂ O. X‐ray diffraction reflections correspond to a cubic structure, with sizes from 31.9 to 104.3 nm. High‐resolution transmission electron microscopy reveals that the different shapes depend strongly on the conditions of the green synthesis.Inspec keywords: nanostructured materials, copper compounds, nanofabrication, pH, response surface methodology, ultraviolet spectra, X‐ray diffraction, transmission electron microscopyOther keywords: green chemistry synthesis, nanocuprous oxide, reducing agent, reaction pH, response surface method, ultraviolet‐visible spectroscopy, size distribution, cubic structure, high‐resolution transmission electron microscopy, X‐ray diffraction reflection, central composite design, Cu₂ O     

The effect of complexing agents on the oriented growth of electrodeposited microcrystalline cuprous oxide film

Three conventional complexing agents, including lactic acid, citric acid and EDTA, are applied in the electrodeposition of microcrystalline cuprous oxide (Cu₂O) film on indium tin oxide glass substrate. Both scanning electron microscopy and X-ray diffraction have been performed to characterize the morphology and texture of microcrystalline Cu₂O film. It is found that the stability constant of copper-based complex compound can obviously influence the deposition overpotential of Cu₂O, and the overpotential can significantly alter the growth priority of different planes, which results in oriented growth of Cu₂O grains. The quantitative relationships between the stability constant and the deposition overpotential of different complexing agents, as well as the relationship between the overpotential and the formation energy of microcrystalline cuprous oxide's (1 1 0), (1 1 1) and (2 0 0) planes are calculated, respectively.     

Template-mediated synthesis and bio-functionalization of flexible lignin-based nanotubes and nanowires

Limitations of cylindrical carbon nanotubes based on the buckminsterfullerene structure as delivery vehicles for therapeutic agents include their chemical inertness, sharp edges and toxicological concerns. As an alternative, we have developed lignin-based nanotubes synthesized in a sacrificial template of commercially available alumina membranes. Lignin is a complex phenolic plant cell wall polymer that is generated as a waste product from paper mills and biorefineries that process lignocellulosic biomass into fuels and chemicals. We covalently linked isolated lignin to the inner walls of activated alumina membranes and then added layers of dehydrogenation polymer onto this base layer via a peroxidase-catalyzed reaction. By using phenolic monomers displaying different reactivities, we were able to change the thickness of the polymer layer deposited within the pores, resulting in the synthesis of nanotubes with a wall thickness of approximately 15?nm or nanowires with a nominal diameter of 200?nm. These novel nanotubes are flexible and can be bio-functionalized easily and specifically, as shown by in vitro assays with biotin and Concanavalin A. Together with their intrinsic optical properties, which can also be varied as a function of their chemical composition, these lignin-based nanotubes are expected to enable a variety of new applications including as delivery systems that can be easily localized and imaged after uptake by living cells.     

Rapid synthesis of aligned zinc oxide nanowires

A solution growth approach for zinc oxide (ZnO) nanowires is highly appealing because of the low growth temperature and possibility for large area synthesis. Reported reaction times for ZnO nanowire synthesis, however, are long, spanning from several hours to days. In this work, we report on the rapid synthesis of ZnO nanowires on various substrates (such as poly(ethylene terephthalate) (PET), silicon and glass) using a commercially available microwave oven. The average growth rate of our nanowires is determined to be as high as 100?nm?min(-1), depending on the microwave power. Transmission electron microscopy analysis revealed a defect-free single-crystalline lattice of the nanowires. A detailed analysis of the growth characteristics of ZnO nanowires as functions of growth time and microwave power is reported. Our work demonstrates the possibility of a fast synthesis route using microwave heating for nanomaterials synthesis.     

Structural transformation of partially confined copper nanowires inside defected carbon nanotubes

The encapsulated copper atoms inside a defected single-walled carbon nanotube escape from the tube through the defect hole as the temperature increases. This causes the partially confined copper nanowires (CNWs) to undergo special structural transformations from a solid to a distinguishable helical layered structure and finally to the liquid state. The defect has a vital function in automatically adjusting the internal pressure and copper atom density. The critical structural transformation temperature of the CNW is significantly influenced by the confinement conditions of the carbon nanotube.     

Structural analysis of electrodeposited copper microstructures fabricated through template synthesis

The electrochemical template synthesis of high aspect ratio copper microcylinders in the track-etch membranes of polycarbonate having nominal pore size of 800, 600 and 200 nm is considered. The morphological and structural analyses have been carried out through scanning electron microscopy and X-ray diffraction, respectively. The X-ray diffraction studies reveal that the material has FCC lattice structure with a high texture coefficient for (200) planes. Regardless of the nominal pore-size of the template membrane, the texturing has been found to decrease significantly when the electrolyte temperature during fabrication is increased from 30 to 60 °C.     

Formation of copper oxide films on fiberglass by adsorption and reaction of cuprous ions

We have used chemical deposition of copper complex solution to prepare CuO thin films on commercial fiberglass. The deposition of copper oxides was done in a beaker using a solution of thiosulfatocuprate (I) as precursor and NaOH as a film conditioner. In order to establish a correlation between experimental conditions and the produced copper species, as well as the film quality, the as deposited and annealed samples were characterized using X-ray diffraction, visible spectrophotometry and atomic force microscopy. The most important result is that a Cu₂O 80-nm film can be obtained directly with a short immersion of fiberglass into the copper solution. The film growth of this copper phase occurred in [111] and [200] directions. Moreover, this phase is converted to CuO by annealing at 375 °C.     

Field emission from copper phthalocyanine and copper hexadecafluorophthalocyanine nanowires

Copper phthalocyanine (CuPc) and copper hexadecafluorophthalocyanine (F₁₆CuPc) nanowires were fabricated by vapor deposition. The nanowires were studied by scanning electron microscopy and transmission electron microscopy. Field emission properties of these nanowires were studied. The field emission properties were strongly dependent on the substrate temperature and the material used, and the best results are obtained for β-phase CuPc nanoribbons. Different dependences of field emission properties on the substrate temperature were obtained for the two materials investigated. The obtained results are discussed.     

Bacterial synthesis of copper/copper oxide nanoparticles

A bacterial mediated synthesis of copper/copper oxide nanoparticle composite is reported. A Gram-negative bacterium belonging to the genus Serratia was isolated from the midgut of Stibara sp., an insect of the Cerambycidae family of beetles found in the Northwestern Ghats of India. This is a unique bacterium that is quite specific for the synthesis of copper oxide nanoparticles as several other strains isolated from the same insect and common Indian mosquitoes did not result in nanoparticle formation. By following the reaction systematically, we could delineate that the nanoparticle formation occurs intracellularly. However, the process results in the killing of bacterial cells. Subsequently the nanoparticles leak out as the cell wall disintegrates. The nanoparticles formed are thoroughly characterized by UV-Vis, TEM, XRD, XPS and FTIR studies.