Colloidal Copper Research Articles

Surface-enhanced Raman scattering from ferrocyanide and ferricyanide ions adsorbed on silver and copper colloids

Surface-enhanced Raman scattering has been observed from the adsorption of ferrocyanide (hexacyanoferrate(II)) and ferricyanide (hexacyanoferrate(III)) ions on Ag and Cu colloids and electrodes. Both ferrocyanide and ferricyanide ions interact strongly with Ag and Cu surfaces, and are bonded to surfaces via the end-on bridging CN σ-bondings. Chemisorption lowers site symmetry of the adsorbed states, resulting in the activation of Raman forbidden modes in the low-frequency as well as the nitrile-stretching regions.

Formation of Cu Nanoparticles from CuO Powder by Laser Ablation in 2-Propanol

Abstract Laser ablation technique has been employed to generate Cu nanoparticles from CuO powder in 2-propanol. The resulting copper colloids are conspicuously stable under aerobic and protective agent-free conditions. Larger particles have also been produced through the photoinduced aggregation.

Sol-gel SiO2 films containing colloidal copper particles for surface-enhanced raman scattering of graphite

Sol-gel SiO2 films containing colloidal copper particles for surface-enhanced raman scattering of graphite

Sol–gel SiO2 films containing colloidal copper particles for surface‐enhanced raman scattering of graphite

Sol–gel SiO2 films containing colloidal copper particles for surface‐enhanced raman scattering of graphite

Surface-enhanced Raman spectra of the reduction product of 4-cyanopyridine on copper colloids

Surface-enhanced Raman spectra of 4-cyanopyridine in a copper colloid solution were collected and showed no signal due to the C≡:N stretching normal mode. [15N]-4-Cyanopyridine was prepared and similar results were obtained. The spectra of these molecules on gold colloids contain a signal attributed to this mode. These data were interpreted as being due to a transition metal-assisted reduction of the nitrile group with the product 4-aminomethylpyridine being adsorbed on the copper surface. The surface-enhanced Raman spectrum of 4-aminomethylpyridine on a copper colloid is nearly identical with the spectrum collected for 4-cyanopyridine with the copper colloid. © 1998 John Wiley & Sons Ltd.

Optical Properties of Coatings with Cu and Copper Oxide Colloidal Particles in a SiO<sub>2</sub> Matrix

SiO 2 coatings prepared by the sol-gel method containing various amounts of copper have been annealed under two different atmospheres to produce colloidal copper based particles embedded in a SiO 2 matrix. The particle composition depended on: the amount of copper added to the stating solutions, the atmosphere in which the samples were annealed and the annealing temperature. The optical properties of the colloidal coatings were determined using the model proposed by Mie, using effective values for the optical constants of the colloidal particles.

In Situ X-ray Absorption Spectroscopy Investigation during the Formation of Colloidal Copper

The reduction of [N(octyl)4]2[CuCl2Br2] in organic solution (toluene) using Li[BEt3H] leads to colloidal Cu protected by cationic surfactants (NR4+). According to HRTEM (high-resolution transmission electron microscopy) and UV/vis data, the organosol is composed of relatively large Cu particles with diameters of between 5 and 10 nm. An in situ XANES (X-ray absorption near edge structure) investigation was performed for the first time during the colloid synthesis. Our measurements revealed the formation of an intermediate Cu+ state prior to the nucleation of the particles, thus giving direct insight into the mechanism of the colloid formation. The significant differences between the near edge structures of the bulk sample and the colloidal Cu have to be traced back to structural disorder in the lattice of this nanosized material.

Synthesis and Magnetic Properties of Elongated Fe−Cu Alloys

Colloidal copper (Fe−Cu) alloy was prepared in aqueous solution via sodium borohydride reduction of Cu and Fe dodecyl sulfate [Cu(DS)2 and Fe(DS)2]. The synthesis performed at the critical micellar...

Strong red-light scattering from colloidal copper in ZBLAN fluoride glass

Following extended thermal processing under reducing conditions, fluoride glasses with a composition close to the standard 53% ZrF 4-20% BaF 2-4% LaF 3-3% AlF 3-20% NaF (ZBLAN) formulation scatter red light in a band centred at around 600 nm, together with an associated extinction band centred at around 570 nm. Some samples show a dichroic effect of appearing red in back-scattered light but blue in transmitted light. The spectra are attributed to a dilute colloidal precipitate of copper, present as a residual impurity in the starting material with a concentration of around 1 ppm by volume. Calculations of the extinction and scattering spectra for copper colloidal particles show that the light scattering efficiency peaks at around 600 nm, but is insignificant compared with absorption for particle radii less than about 30 nm. For particle radii between about 30 and 50 nm, the scattering dominates the beam-particle interaction and is still peaked in the red region. For larger radii, the peak in the scattering efficiency becomes invariant and broadens. Fittings based on the calculations suggest that the copper particles responsible for the observed spectra in ZBLAN glass have radii in the range of 16 to 45 nm.

Application of XAFS in Archaeology

X-ray fluorescence XAFS technique was successfully applied to the archaeological study to find colorant elements in old glass samples and to characterize the chemical states of iron in the ceramic sherds excavated from an archaeological site in Turkey. The origin of red color of the mosaic glass is found to be due to the colloidal copper particles in the glass. Blue color is attributed to divalent cobalt. Fe K-XANES spectra revealed that the color of the sherds changes from black, gray, brown, to orange with increasing the absorption edge energy. The gray ceramics typical for Phrygia age were produced in a reducing condition. The cream color of the central Anatolian Iron Age could not be related with the oxidation state of iron.

Metal colloids employed in the SERS of biomolecules: activation when exciting in the visible and near-infrared regions

Silver, gold and copper colloids have been employed in the study of the nucleic bases cytosine, guanine, their alkyl derivatives 1-methylcytosine, 5-methylcytosine, 1,5-dimethylcytosine, 7-methylcytosine and 9-ethylguanosine. Cytidine, 5′-cytidinemonophosphate and 5′-adenosinemonophosphate have been also studied using silver and copper colloids. The interaction and orientation of these compounds on the metal colloids are interpreted on the basis of the SER spectra obtained, and further compared with interactions with the corresponding metallic ions in aqueous solution. Transmission electronic microscopy and ultraviolet-visible absorption spectroscopy were also employed to characterize the silver and copper colloids before and after aggregation by 1,5-dimethylcytosine. Information on the aggregation process is presented. The activation effect of chloride, perchlorate and nitrate anions on the silver colloids employed is studied for both the visible and near-infrared regions. An assessment of the effectiveness of each colloid is made at different excitation lines. Finally, an explanation of the mechanism through which these anions exert their activation effect is given on the basis of the morphologies of the particles contained in the colloid.

Preparation and Growth Mechanism of Uniform Colloidal Copper Oxide by the Controlled Double-Jet Precipitation

Monodispersed crystalline CuO particles of different morphologies were synthesized by the controlled double-jet precipitation (CDJP) technique using NaOH and Cu(NO3)2as the reactants. The effects of temperature, reaction time, pH, and the concentrations of chemicals on the characteristics of final products were investigated. With lower [NaOH]/[Cu(NO3)2] molar ratios and temperatures, colloidal gerhardtite Cu2(OH)3NO3precipitated, while tenorite CuO particles of various morphologies were obtained at higher temperatures and [NaOH]/[Cu(NO3)2] ratios. Time resolved electron microscopy indicated that nanosized primary particles formed immediately after mixing the reactants, followed by aggregation into larger uniform particles of submicrometer size.

Synthesis of Copper Nanoparticles in Nonionic Water-in-Oil Microemulsions

Synthesis of well-dispersed copper nanoparticles was achieved by reduction of aqueous copper chloride solution using NaBH4in the nonionic water-in-oil (w/o) microemulsions formed by Triton X-100,n-hexanol, cyclohexane, and water. It has been shown that instead of copper oxide produced in aqueous solution, metallic copper particles are formed in w/o microemulsions because of the high local copper concentration in water pools of the microemulsions, indicating the advantage offered by w/o microemulsions over aqueous phases. The absorption spectrum of the colloidal copper particles obtained in microemulsions does not exhibit the plasmon peak characteristic of the Cu surface. It is conceivable that the lack of the plasmon absorption band is attributed to the formation of a CuCl monolayer on the copper particles.

Kinetic investigations into the copper(II)-catalysed peroxosulfate oxidation of Calmagite dye in alkaline media

Addition of CuII catalysed the peroxosulfate (KHSO5) oxidation of Calmagite dye (D) in alkaline media and it was observed that the dye decomposition profiles exhibit extremely complex kinetic behaviour, with typical induction periods associated with rapid autocatalysis. A comprehensive kinetic model has been derived which not only can predict changes in speciation of reactants with time, but can also satisfactorily explain all the kinetic profiles. Much higher catalyst concentrations are required for copper(II) catalysis than for manganese(II) catalysis ([KHSO5] > [CuII] > [D] as opposed to [KHSO5] > [D] > [MnII]), i.e. there needs to be excess CuII over D. This arises for two main reasons; first, binding of CuII to the dye inhibits its reaction with peroxosulfate, protecting the dye against oxidation, and secondly the active catalyst is a heterogeneous copper hydroxide species which arises when there is an excess of CuII in alkaline media. The unusual decomposition profiles are attributed to release of CuII into alkaline media via direct oxidation of the [CuD] complex by peroxosulfate. This oxidation is relatively slow, but when sufficient CuII is released ‘true’ autocatalysis is exhibited. The best simulated fits were obtained when the catalytic step was assumed to be first order in [SO52–] (i.e. peracid primarily acting as a nucleophile) and zero order in [CuD] as it is adsorbed onto the colloidal copper hydroxide.

Synthesis, Characterization, and Nonlinear Optical Properties of Copper Nanoparticles

In this paper, copper nanoparticles were prepared by the reduction of copper(II) acetate in water and 2-ethoxyethanol using hydrazine under reflux. The synthesized nanoparticles exhibit a distinct absorption peak in the region 572−582 nm. The average size variation from 6.6 to 22.7 nm in ethoxyethanol and from 15.5 to 30.2 nm in water was achieved by the addition of various amounts of a protective polymer (poly(N-vinylpyrrolidone)). The nonlinear optical properties of the copper colloids were first measured using the Z-scan technique. The χ(3)/α0 values obtained were found to be of the magnitude of 10-11−10-12 esu cm, which are in good agreement with the reported values obtained for copper nanoparticles embedded in glass.

Prepration of Copper Colloid and it's Absorption Spectrum

Prepration of Copper Colloid and it's Absorption Spectrum

SERS of Guanine and its Alkyl Derivatives on Gold Sols

Surface-enhanced Raman spectroscopy (SERS) has proved to be an increasingly important technique in studies of biomolecules adsorbed on metal surfaces [1]. Guanine and its derivatives are known to play a role as inductors of mutagenesis and carcinogenesis [2] and some of their SERS spectra on silver colloids were published some years ago [3–5]. In a more recent work [6] we carried out a SERS study of these species using silver and copper colloids as supports which provided very interesting results regarding their electrodynamic behaviour on these metal surfaces.

Formation of Fractal Clusters of Colloidal Copper Hydrous Oxides

AbstractThe fractal dimensions of colloidal particles of copper hydrous oxides in the presence of natural occurring anionic exopolymers are reported from measurements using both small‐angle X‐ray‐ and static light scattering techniques. The power law decay of the structure factor [S(k) ∼ k −D] of colloidal copper hydrous oxides dispersions can be explained in terms of fractal geometry. D is found to be 2.15 ± 0.05 for Cu(OH)2, and for colloidal Cu2O·x H2O aggregates a value of 1.75 ± 0.07 was determined.

Control of the Shape and the Size of Copper Metallic Particles

Colloidal copper particles were prepared in aqueous solution via the reduction of copper dodecyl sulfate, Cu(DS)2, by sodium borohydrate. Below the critical micellar concentration (cmc), it has bee...

Coating of Uniform Inorganic Particles with Polymers: II. Polyaniline on Copper Oxide

Uniform spherical colloidal copper oxide particles were coated with polyaniline in the reaction mixtures containing CuO, aniline, water, ethanol, and polyvinyl alcohol (PVA) without the use of a soluble oxidant. The final dispersion consisted of a mixture of CuO with a polymer shell and independent polyaniline (latex) particles. The reaction between aniline and CuO follows the well-known mechanism by which the metal oxide undergoes reductive dissolution while the organic monomer is oxidized. Oxygen and PVA are essential to the polymerization of aniline in the system. Oxygen may function as an oxidant to promote the polymerization, while PVA forms micelles that enhance the reaction rate through emulsion polymerization and protect polyaniline from hydrolysis. A temperature higher than 90°C is necessary for the reaction to achieve a coating of more than 10% by weight in 48 h. The thickness of the polymer shell can be adjusted by changing the reaction time and the concentrations of aniline, copper oxide, and ethanol. The structure of the produced polymer corresponds to that of polyleucoemeraldine.