Resonance Of Copper Research Articles

Nickel coating on plasmonic copper nanoparticles lowers cytotoxicity and enables colorimetric pH readout for antibacterial wound dressing application.

Wound infection poses a significant challenge to the natural healing process. It can impede various stages of wound healing, thereby hindering tissue regeneration and increasing the risk of systemic complications. Wound dressings emerged as a crucial option in the management of infections. Herein, we investigate fabrics coated with copper-based nanoparticles for potential wound dressing application. We synthesized copper and copper-nickel (Cu-Ni) core-shell nanoparticles via a polyol synthesis and investigated their particle growth dynamics and chemical stability. The nickel coating stabilized the nanoparticles against oxidation and dissolution, while dampening the localized surface plasmon resonance of copper. When coated on the fabrics, we found that Cu-Ni NPs were slightly less effective as an antibacterial agent than Cu NPs, however the cytotoxicity of Cu-Ni NPs was significantly reduced compared to pure Cu. Additionally, we show that the discoloration of nanoparticle-coated fabrics depended on pH, thus enabling the visualization of pH levels of simulated wound fluids which can provide information on the inflammatory state of the wound. Our work contributes to the understanding of copper-based nanoparticles and their potential applications in healthcare.

Effects of High Pressure on the Surface Plasmon Resonance of Copper and Silver Nanocrystals

Effects of High Pressure on the Surface Plasmon Resonance of Copper and Silver Nanocrystals

Surface Plasmon Photodetectors Based on Noble Metals

In this work, high sensitivity noble metals used in the Kretschmann configuration based photodetectors applied to detect the presence of biological and chemical species in solutions are investigated. The angle of incidence and film thickness dependencies of the surface plasmon polariton resonance (SPPR) of gold, silver and copper by the attenuated total reflection (ATR) method are studied to monitor and evaluate the SPR reflectance angle and reflectivity change. The analysis of the electric field of the surface plasmon wave which appears at the interface between the metallic layer and the air is carried out by the finite element method (FEM). The simulation is performed using COMSOL Multiphysics software which supports FEM. The aim of the present study is to find the most suitable noble metal and its optimum thickness to improve the performance of the SPR photodetector. Keywords: Attenuated total reflection method, FEM based COMSOL multiphysics software, Kretschmann configuration, noble metals, reflectivity.

Vis-Responsive Copper-Modified Titania for Decomposition of Organic Compounds and Microorganisms

Seven commercial titania (titanium(IV) oxide; TiO2) powders with different structural properties and crystalline compositions (anatase/rutile) were modified with copper by two variants of a photodeposition method, i.e., methanol dehydrogenation and water oxidation. The samples were characterized by diffuse reflectance spectroscopy (DRS), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Although zero-valent copper was deposited on the surface of titania, oxidized forms of copper, post-formed in ambient conditions, were also detected in dried samples. All samples could absorb visible light (vis), due to localized surface plasmon resonance (LSPR) of zero-valent copper and by other copper species, including Cu2O, CuO and CuxO (x:1-2). The photocatalytic activities of samples were investigated under both ultraviolet (UV) and visible light irradiation (>450 nm) for oxidative decomposition of acetic acid. It was found that titania modification with copper significantly enhanced the photocatalytic activity, especially for anatase samples. The prolonged irradiation (from 1 to 5 h) during samples’ preparation resulted in aggregation of copper deposits, thus being detrimental for vis activity. It is proposed that oxidized forms of copper are more active under vis irradiation than plasmonic one. Antimicrobial properties against bacteria (Escherichia coli) and fungi (Aspergillus niger) under vis irradiation and in the dark confirmed that Cu/TiO2 exhibits a high antibacterial effect, mainly due to the intrinsic activity of copper species.

Precise Control of Copper-Localized Surface Plasmon Resonance in the Near Infrared Region for Enhancement of Up-Conversion Luminescence

The surface plasmon resonance of copper in the near infrared region provides a novel method for enhancement of up-conversion luminescence compared to using gold and silver, as the former grants significant cost savings. In this study, we made a flat Cu film covered TiO2 to enhance the up-conversion fluorescence intensity. The results show that the deposition of copper/TiO2 dioxide nanocomposite film prepared via spin-coating has no effect on the structure of NaGdF4:Er3+, Yb3+. The absorption wavelength of the copper film moved from the original visible wavelength (~600 nm) range to the infrared wavelength after covering TiO2, and most obviously, the copper film covered two layers of TiO2 by about 16 nm; the peak of the absorption appeared at 835 nm due to the enhanced excitation field. The behavior of the nanocomposite film with NaGdF4:Er3+ and Yb3+ under 980 nm excitation was investigated; it provides a novel way for studying mental-enhanced fluorescence. Besides, the peaks of the fluorescence spectrum show different emissions at 542 nm and 660 nm, respectively. The copper nanoparticles-covered TiO2 layer can obviously enhance the fluorescence intensity, and the maximum enhancement factors of emission of NaGdF4:Er3+ and Yb3+ nanoparticles are 3.1 and 1.9 on the nanocomposite film, respectively.

Surface Plasmon Polariton Resonance of Gold, Silver, and Copper Studied in the Kretschmann Geometry: Dependence on Wavelength, Angle of Incidence, and Film Thickness

Surface plasmon polariton (SPP) resonance spectra for noble metals (Au, Ag, and Cu) were comprehensively studied in the Kretschmann attenuated total reflection (ATR) geometry, in the wavelength (λ) range from 300 to 1000 nm with the angle of incidence (θ) ranging from 45 to 60° and the film thickness (d) ranging from 41 to 76 nm. The experimental plasmon resonance spectra were reproduced by a calculation that included the broadening effects as follows: (1) the imaginary part of the bulk dielectric constant, (2) the thickness-dependent radiative coupling of the SPP at the metal–air interface to the prism, (3) the lack of conservation of the wavevector parallel to the interface kx(k||) caused by the surface roughness, (4) scanning λ at a fixed θ (changing both energy and kx at the same time) over the SPP dispersion relation. For Au and Ag, the experimental results were in good agreement with the calculated results using the bulk dielectric constants, showing no film thickness dependence of the plasmon resonance energy. A method to extract the true width of the plasmon resonance from raw ATR spectra is proposed and the results are rigorously compared with those expected from the bulk dielectric function given in the literature. For Au and Ag, the width increases with energy, in agreement with that expected from the relaxation of bulk free electrons including the electron–electron interaction, but there is clear evidence of extra broadening, which is more significant for thinner films, possibly due to relaxation pathways intrinsic to plasmons near the interface. For Cu, the visibility of the plasmon resonance critically depends on the evaporation conditions, and low pressures and fast deposition rates are required. Otherwise, scattering from the surface roughness causes considerable broadening of the plasmon resonance, resulting in an apparently fixed resonance energy without clear incident angle dependence. For Cu, the observed plasmon dispersion agrees well with that expected from the bulk dielectric function even with nominal oxidation of the surface, but the widths at long wavelengths are much larger than those theoretically expected.

Rapid photocatalytic debromination on TiO2 with in-situ formed copper co-catalyst: Enhanced adsorption and visible light activity

The cheap metal Cu particles in-situ loaded on TiO2 surface is able to co-catalyze the photocatalytic debromination of polybrominated pollutants. Over 15 times of enhancement for the reductive debromination of deca-brominated diphenyl ether (BDE209) over Cu/TiO2 is achieved, relative to that on the bare TiO2. Moreover, the presence of metal copper markedly changes the distribution of the formed intermediates, indicating the change in the debromination mechanism because of the co-catalysis of metal Cu. The detailed ex-situ and in-situ characterizations of the Cu/TiO2 photocatalyst indicate that the copper remains its Cu0 valence state in photocatalytic turnover. The mechanistic investigation suggests that the presence of metal copper nanoparticles greatly enhance the adsorption of hydrophobic BDE209 on the photocatalyst, which facilitates the electron transfer from the conduction band of TiO2 to the pollutants. Our experimental results also implies that the interaction of BDE209 with metal copper co-catalyst would position-specifically activate the C-Br bonds during the dissociative electron transfer. We further show that the surface plasmon resonance of metal copper can contribute to the enhancement of photocatalytic activity by utilizing the visible-light part of the irradiation. The present study provides a simple and economic method for elimination of organobromide pollutants, and would be promising in reductive dehalogenation by other techniques.

Metal-Enhanced Fluorescence Platforms Based on Plasmonic Ordered Copper Arrays: Wavelength Dependence of Quenching and Enhancement Effects

Ordered arrays of copper nanostructures were fabricated and modified with porphyrin molecules in order to evaluate fluorescence enhancement due to the localized surface plasmon resonance. The nanostructures were prepared by thermally depositing copper on the upper hemispheres of two-dimensional silica colloidal crystals. The wavelength at which the surface plasmon resonance of the nanostructures was generated was tuned to a longer wavelength than the interband transition region of copper (>590 nm) by controlling the diameter of the underlying silica particles. Immobilization of porphyrin monolayers onto the nanostructures was achieved via self-assembly of 16-mercaptohexadecanoic acid, which also suppressed the oxidation of the copper surface. The maximum fluorescence enhancement of porphyrin by a factor of 89.2 was achieved as compared with that on a planar Cu plate (CuP) due to the generation of the surface plasmon resonance. Furthermore, it was found that while the fluorescence from the porphyrin was quenched within the interband transition region, it was efficiently enhanced at longer wavelengths. It was demonstrated that the enhancement induced by the proximity of the fluorophore to the nanostructures was enough to overcome the highly efficient quenching effects of the metal. From these results, it is speculated that the surface plasmon resonance of copper has tremendous potential for practical use as high functional plasmonic sensor and devices.

Characterization of silver or copper nanoparticles embedded in Soda-lime glass after a staining process

Yellow and red colored glass is usually obtained by a staining process, in the fields of art and craft. It consists in the application at the glass surface of either red ochre mixed with silver sulfate to obtain the color yellow or copper sulfate to obtain the color red, both applications being followed by an annealing treatment. These treatments lead to noble metal nanoparticle formation. The determination of the nanoparticle properties is of great interest in order to correlate the nanoparticles size, shape, distance to the color dot. Noble metal nanoparticles are mainly investigated for their easy incorporation and their well known optical response in the visible region. In this study, we highlight the Surface Plasmon Resonance of copper and silver nanoparticles embedded in a classical silicate glass. We want to demonstrate that this effect can be evaluated by the help of several characterization methods. In this way, we have obtained information by SEM, XRD, TEM and infrared measurement about the metal concentration profile, its structure, the nanoparticles size, their shape and the evolution of the glass structure correlated to the particles growth. We also discuss the correlation by a fitting procedure of optical experimental spectra with an optical model. We highlight the effect of the glass tin face on particle precipitation.

Theoretical Analysis of Electron Paramagnetic Resonance and Optical Spectra of Copper(II) Doped Bis(L-asparaginato)Zn(II)

ABSTRACT In this paper, a complete diagonalization (of energy matrix) procedure (CDP) is proposed to calculate the spin-Hamiltonian parameters [g-factors g∥, g⊥ and hyperfine structure constants A∥, A⊥, which can be obtained from electron spin resonance (ESR) spectra] and d-d transitions (optical spectra) for d9 ions in an orthorhombic field with D2h symmetry. The calculated spin-Hamiltonian parameters and d-d transitions of ZnC8H14N4O6: Cu2+ crystal from the CDP are in reasonable agreement with the experimental values. This suggests that the method is effective for the theoretical analysis of ESR and optical spectral data for 3d9 ions with ground state 2B2() in a D2h symmetry.

Electron Spin Resonance of Manganese (II) and Copper (II) Adsorbed on Clay Minerals and Silica-alumina

Electron Spin Resonance of Manganese (II) and Copper (II) Adsorbed on Clay Minerals and Silica-alumina

Synthesis, X-ray Structure, Magnetic Resonance, and DFT Analysis of a Soluble Copper(II) Phthalocyanine Lacking C−H Bonds

The synthesis, crystal structure, and electronic properties of perfluoro-isopropyl-substituted perfluorophthalocyanine bearing a copper atom in the central cavity (F(64)PcCu) are reported. While most halogenated phthalocyanines do not exhibit long-term order sufficient to form large single crystals, this is not the case for F(64)PcCu. Its crystal structure was determined by X-ray analysis and linked to the electronic properties determined by electron paramagnetic resonance (EPR). The findings are corroborated by density functional theory (DFT) computations, which agree well with the experiment. X-band continuous-wave EPR spectra of undiluted F(64)PcCu powder, indicate the existence of isolated metal centers. The electron-withdrawing effect of the perfluoroalkyl (R(f)) groups significantly enhances the complexes solubility in organic solvents like alcohols, including via their axial coordination. This coordination is confirmed by X-band (1)H HYSCORE experiments and is also seen in the solid state via the X-ray structure. Detailed X-band CW-EPR, X-band Davies and Mims ENDOR, and W-band electron spin-echo-detected EPR studies of F(64)PcCu in ethanol allow the determination of the principal g values and the hyperfine couplings of the metal, nitrogen, and fluorine nuclei. Comparison of the g and metal hyperfine values of F(64)PcCu and other PcCu complexes in different matrices reveals a dominant effect of the matrix on these EPR parameters, while variations in the ring substituents have only a secondary effect. The relatively strong axial coordination occurs despite the diminished covalency of the C-N bonds and potentially weakening Jahn-Teller effects. Surprisingly, natural abundance (13)C HYSCORE signals could be observed for a frozen ethanol solution of F(64)PcCu. The (13)C nuclei contributing to the HYSCORE spectra could be identified as the pyrrole carbons by means of DFT. Finally, (19)F ENDOR and easily observable paramagnetic NMR were found to relate well to the DFT computations, revealing negligible isotropic hyperfine (Fermi contact) contributions. The single-site isolation in solution and solid state and the relatively strong coordination of axial ligands, both attributed to the introduction of R(f) groups, are features important for materials and catalyst design.

Raman spectroscopy of copper nanoparticle‐containing glass matrices: ancient red stained‐glass windows

AbstractA selection of red‐flashed and red‐coated medieval potash lime and 19th century soda lime stained glass pieces were studied in the laboratory using different instruments and laser wavelengths, both at lower and higher than the surface plasmon resonance (SPR) of copper. The Raman signatures of the transparent glass matrix and the red glass layers are discussed and compared with those recorded on model glasses containing a dispersion of Cu0 nanoparticles. Evidence is given that the conformation of the silica network in the vicinity of the metal nanoparticles differs from that of the glass matrix. Hematite and carbon traces are evidenced in the Cu0‐rich layers, which is consistent with the use of a combination of a reducing atmosphere and redox couples to control the growth of metallic copper particles. Copyright © 2009 John Wiley & Sons, Ltd.

Irradiation induced dissolution of Cu and growth of Ag nanoclusters in Cu/Ag ion-exchanged soda-lime glass

Complex metal nanoclusters of Cu/Ag are formed in a soda-lime glass matrix by sequential copper and silver ion-exchange followed by ion irradiation. Optical absorption measurements showed signature of copper clusters alone in the Cu/Ag ion-exchanged sample. Irradiation of the ion-exchanged sample with He + ions of energy 100 keV of different fluences resulted in the growth of the silver clusters with, the optical absorption spectrum exhibiting two peaks corresponding to the surface plasmon resonance of copper and silver in the same matrix. It was found that with increase in fluence the silver clusters begin to grow while the already formed copper clusters segregate, which can be visualized from the absorption spectra, where the copper band disappears while the silver band grows with the increase in dose. Vacuum annealing of the Cu/Ag ion-exchanged samples resulted in complete disappearance of copper clusters while the silver clusters grew till they attained saturation. The glancing incidence X-ray diffraction study of the Cu/Ag ion-exchanged and irradiated sample showed silver peaks alone with no information of alloying between the two species.

EPR and optical studies on transition metal doped LiRbB 4O 7 glasses

Electron paramagnetic resonance and optical investigations of copper and chromium doped LiRbB 4O 7 glasses are carried out. From the results and discussions, it is predicted that both the transition metal ions exhibit octahedral environment. In the case of Cr 3+, the site symmetry is near octahedral, whereas in the case of Cu 2+, it is tetragonally distorted octahedral environment. Crystal field, spin-Hamiltonian and bonding parameters are evaluated. The bonding parameters are suggesting ionic.

Electron spin resonance of copper(II) as a tool for the determination of asparagine concentration in Bacillus subtilis cultures

A procedure is presented that is based on the detection of Cu(II)–asparagine complexes by quantitative ESR, and allows in a very simple and rapid manner to evaluate the changes of asparagine concentration during the entire time range of the growth of Bacillus subtilis in a typical growth medium. The analysis is carried out in terms of the decrease of the intensity of the ESR-active mono- and di-asparagine–copper(II) complexes. It is resulted that at the end of the exponential growth the asparagine concentration was reduced to values as low as 2% of the initial value. The procedure here reported may be the basis of similar methods to be used for other amino acids and prokaryote systems.

63Cu Nuclear Magnetic Resonance and Viscosity Studies of Copper (I) Perchlorate in Mixed Solvents Containing Acetonitrile

Abstract 63Cu nuclear magnetic resonance and viscosity studies of 0.064 M copper (I) Perchlorate solutions have been made at 298 K in binary mixtures of acetonitrile (AN) with dimethylsulphoxide (DMSO), hexamethylphosphotriamide (HMPA), N,N-dimethylacetamide (DMA), nitromethane (NM), propylene carbonate (PC) and 3-hydroxypropionitrile (3 HPN) at several compositions of the mixtures using a 500 MHz NMR Spectrometer and Ubbelohde viscometer, respectively. The chemical shift (δ), linewidth (Δ) and line intensity (I) of the 63Cu NMR signal in these mixed solvents have been measured relative to the 63Cu signal in 0.064 M copper (I) Perchlorate (CuClO4) solution in pure AN. The quadrupolar re-laxation rates (1/T2)Q, reorientational correlation times (τR) and quadrupolar coupling constants (QCC) of the copper (I) solvates have also been estimated from the data. The QCC values show a big variation in all solvent systems with the change of solvent composition, indicating the formation of mixed com-plexes. The variation of all NMR parameters with solvent composition shows strong effects of DMSO, HMPA, and DMA on the solvation behaviour of Cu + in the first three mixtures, and relatively much weaker effects of PC, NM and 3HPN in the other three mixtures.

Paramagnetic resonance and magnetism of copper(II) complexes with N, N′, N″, N‴-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane

EPR (X- and Q-band) and magnetic susceptibility over the temperature range 4.2–300 K are reported for a number of dinuclear Cu(II) complexes derived from N, N′, N″, N‴-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane (tpmc). [Cu 2X(tpmc)](ClO 4) 3· n (X=N 3, F ( n=2CH 3CN), Cl ( n=H 2O), Br, I ( n=H 2O), NO 2), where the X anions bridge two copper ions and the tpmc ligand has the boat coordination mode, [Cu 2tpmc](ClO 4) 4 and [Cu 2X 2tpmc](ClO 4) 2 (X=N 3, NCS), where the X anions occupy apical positions and the tpmc ligand has the chair coordination mode. It is established that the properties of the complexes are determined by intramolecular exchange interactions occurring through both the bridging anion X and the tpmc ligand as well as by magnetic dipole–dipole interactions. In the majority of the compounds the exchange is weak, e.g. it corresponds to J equals 2.0 cm −1 for [Cu 2N 3(tpmc)](ClO 4) 3 and 3.4 cm −1 for [Cu 2(N 3) 2(tpmc)](ClO 4) 2. [Cu 2OH(tpmc)](ClO 4) 3·2H 2O is an exception in which antiferromagnetic (AF) exchange of about several tens of wave numbers is operating. The EPR spectrum of this complex is described by the following spin Hamiltonian parameters: g z =2.25, g y =2.05, g x =2.04, D=0.06 cm −1, E=0.005 cm −1. Moreover, an extremely strong influence of lattice perturbations on the exchange interactions is recognized for this compound: a partial loss of the H 2O molecules (coordinated at a greater distance) by a small amount of dinuclear fragments results in a transformation of an AF exchange into a ferromagnetic or a weak AF one with different values of the anisotropic spin–spin interaction parameters (for example, D=0.172 cm −1, E=0.015 cm −1). The EPR spectra of frozen solutions of all the complexes in NMF are typical for the triplet state, with a distinctly resolved hyperfine structure for the Δ M S=1 and Δ M S=2 signals, and show very similar values of g factors, hyperfine and fine structure parameters ( g z =2.255, A z =0.0087 cm −1, g x, y =2.052, D=0.025 cm −1), implying the same molecular structure for dinuclear complexes formed in solution as a result of the loss of one bridging X by dimers with the boat configuration or two X anions by dimers with the chair configuration.

Optical properties of anhydrous copper(II) formate single crystal

Infrared (IR) (450–4500 cm −1) spectroscopy, electron paramagnetic resonance (EPR) and optical absorption (52 631-3225 cm −1) studies of anhydrous copper(II) formate single crystal have been carried out at 300 K. The IR spectrum of Cu(COOH) 2 single crystal shows four strong absorption bands at 3199, 1569, 1363 and 833 cm −1 which are attributed to the stretching and bending vibrations between the formate ion atoms. Analysis of EPR spectra using crystal field theory reveals that the Jahn-Teller active copper(II) ion is present in a tetragonally elongated square pyramidal site. The optical absorption in the UV and visible region is characterized by a charge transfer band, and a cubic field splitting of 3 d energy level of Cu 2+ ion. In addition, in the near infrared region eight absorption peaks are recorded. These transitions in the near infrared are assigned variously to the d- d transitions of copper(II) ion between the admixtured quantized energy levels of copper and oxygen orbitals, to the transitions arising out of the Hubbard energy gap of the crystal, and to the Fermi energy gap of the crystal, respectively. Finally the weak absorptions that are recorded are attributed to the linear combinations of the IR bands.

Electron paramagnetic resonance and relaxation study of copper (II) and silver (II) in CsCdF3 single crystals

Copper and silver, respectively, were introduced into single crystals of CsCdF3. Our detailed electron paramagnetic resonance (EPR) study showed that both elements enter the Cd lattice site—copper as Cu2+, silver as Ag+, which then was converted into Ag2+ by x raying the corresponding samples. Cu2+ and Ag2+ were shown to present in their ground state a pseudostatic Jahn–Teller effect. Motional effects were observed in the respective EPR spectra and studied in some detail for Cu2+ as they are seen over a wide temperature range. Predictions of a stochastic Kubo model [J. Phys. Soc. Jpn. 9, 935 (1954)] were compared with the temperature dependent linewidths of the motionally averaged EPR spectrum. A power law (Tn with n≂1.9) was determined for the temperature dependence of the reorientation frequency between 30 and 90 K.