Formation Of Cu Nanoparticles Research Articles

Metallic copper incorporated ionic liquids toward maximizing CO2 separation properties

We report the facilitated CO2 transport membrane by in situ preparation of copper nanoparticles by ionic liquid, such as HmimNO3. The dissociation mechanism of micro-sized copper flakes into surface activated copper nanoparticles in terms of the interface dipole at the organic/metal was suggested. Firstly, HmimNO3 adsorbed onto pristine micro-sized copper flakes consisted of clusters, and then the concentration of electrons in the NO3- lead to the positive charging of the vacuum side. The built-in potential at the interface of HmimNO3/Cu clusters was able to bring out the repulsive force among the positive charged Cu clusters, resulting in the formation of CuNPs. Furthermore, the fabricated Cu nanoparticles (CuNPs) could be utilized as not only CO2 carriers, but also barriers regarding N2 and CH4 transport. The ideal CO2/CH4 and CO2/N2 separation factor of HmimNO3 membranes with a polysulfone asymmetric support was 2.3 and 2.6, respectively. The HmimNO3/CuNPs nanocomposite showed selectivity for CO2/CH4 and CO2/N2 was found to be 6.2 and 7.4, respectively. This implied the surface positive polarized CuNPs addition could be one of the effective strategies toward maximizing CO2 separation.

Formation of Cu Nanoparticles in SBA-15 Functionalized with Carboxylic Acid Groups and Their Application in the Water–Gas Shift Reaction

SBA-15 functionalized with carboxylic acid groups has been used to synthesize Cu nanoparticles 2–6 nm in average size with 7.6–25.2 wt % Cu. In this study, the formation mechanism and characterization of Cu nanoparticles at various Cu concentrations are described. For samples with 7.6 and 11.9 wt % Cu, linear [Cuδ+···Oδ−···Cuδ+]n chains generated through calcination are possibly located inside the SBA-15 channels. When the concentration of Cu is increased to 18.3 wt %, the Cu2(OH)3NO3 species becomes the dominant intermediate before bulky CuO is formed. It is found that the average 2-nm Cu particles provided a significantly higher turnover rate for water–gas shift (WGS) reaction than did higher Cu contents on SBA-15. We propose that the highly dispersed Cu particles or isolated Cu atoms on Cu/SBA-15 catalysts can serve as major active sites for the WGS reaction. The 7.6 and 11.9 wt % Cu/SBA-15 catalysts provide abundant sites on highly dispersed Cu particles or isolated Cu atoms, which lead to a highly ef...

Synthesis of Monodisperse Copper Nanoparticles by Utilizing 1-Butyl-3-methylimidazolium Nitrate and Its Role as Counteranion in Ionic Liquid in the Formation of Nanoparticles

We successfully fabricated Cu nanoparticles from Cu flakes by utilizing the ionic liquid BMIM+NO3–. When BMIM+NO3– existing mostly in the free ion state was used for dissociation of Cu flakes, Cu nanoparticles were rapidly prepared in a relatively short amount of time compared to other ionic liquids. The favorable interaction between free NO3– of BMIM+NO3– and the Cu metal surface caused the flakes to dissociate in the ionic liquid, forming nanoparticles. The formation of Cu nanoparticles was confirmed by UV–vis spectral analysis and transmission electron microscopy (TEM) imaging, and the interaction of BMIM+NO3– with the Cu metal was confirmed by X-ray photoelectron spectroscopy (XPS).

Gas-Induced Formation of Cu Nanoparticle as Catalyst for High-Purity Straight and Helical Carbon Nanofibers

The facile preparation of high-purity carbon nanofibers (CNFs) remains challenging due to the high complexity and low controllability in reaction. A novel approach using gas-induced formation of Cu crystals to control the growth of CNFs is developed in this study. By adjusting the atmospheric composition, controllable preparation of Cu nanoparticles (NPs) with specific size and shape is achieved, and they are further used as a catalyst for the growth of straight or helical CNFs with good selectivity and high yield. The preparation of Cu NPs and the formation of CNFs are completed by a one-step process. The inducing effect of N(2), Ar, H(2), and C(2)H(2) on the formation of Cu NPs is systematically investigated through a combined experimental and computational approach. The morphology of CNFs obtained under different conditions is rationalized in terms of Cu NP and CNF growth models. The results suggest that the shapes of CNFs, namely, straight or helical, depend closely on the size, shape, and facet activity of Cu NPs, while such a gas-inducing method offers a simple way to control the formation of Cu NPs.

Chemical synthesis of Co/Cu core/shell nanocomposites and evaluation of their magnetic properties

Abstract Co/Cu core/shell nanocomposites (CSNCs) with varying shell thickness were synthesized through a modified polyol process in conjunction with a transmetallation reaction. Tuning of shell thickness was achieved by subtle change in concentration of copper acetate infused in different experiments against a fixed cobalt precursor concentration. Formation of Cu nanoparticles (NPs) was observed from UV–vis spectra, which showed a typical surface plasmon resonance peak at 560 nm. Precise control over particle size was obtained by the use of PVP as stabilizer, which was confirmed by a red shift of 20 cm −1 in the C O stretching frequency of various PVP coated Co/Cu CSNCs. Powder X-ray diffraction patterns elucidate the co-existence of distinctive fundamental peaks for both Co and Cu indicating that they have not formed an alloy during the reaction. TEM images corroborate with the above result by revealing the existence of lighter shaded Cu shells coated over dark inner cores of Co. Coalescence of adjacent Cu shells gives a matrix like appearance in case of Co 21.2 Cu 78.8 NPs; whereas Co 90.7 Cu 9.3 NPs were distinctly separated from each other. Magnetic hysteresis loops of all the Co/Cu CSNCs showed ferromagnetic behavior and an increase in magnetization value with decrease in shell thickness was observed.

Cu nanoparticles induced structural, optical and electrical modification in PVA

Cu nanoparticles were synthesized in PVA matrix by chemical reduction of cupric nitrate with hydrazine hydrate. Structural characterization of synthesized Cu–PVA nanocomposite was carried out using UV–Visible Spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Appearance of characteristic surface plasmon resonance peak of Cu nanoparticles at 591 nm in absorption spectra of Cu–PVA colloidal solution confirms the formation of Cu nanoparticles. TEM investigation indicates that Cu nanoparticles of size 16 nm are formed in PVA matrix which are in agreement with the size obtained using X-ray diffraction. Morphology of Cu–PVA nanocomposite was further confirmed using SEM. Analysis of UV–Visible absorption and reflection data indicates towards the reduction in optical band gap and increase in refractive index of the resulting nanocomposite. The synthesized Cu–PVA nanocomposite has been found to be more conducting than PVA as ascertained using I–V studies. The decrease in band gap and increase in conductivity can be correlated due to the formation of localized electronic states in PVA matrix due to insertion of Cu nanoparticles. Photoluminescence measurements showed strong blue visible emission peak at 450 nm at different excitation wavelengths in the range of 220–245 nm.

Effect of ambient gas species on the formation of Cu nanoparticles in wire explosion process

In this paper, the effect of ambient gas species on the characteristics of the produced nanoparticles in wire explosion process is reported. Cu wires with a diameter of 125 μm and length of 6.1 cm were exploded in different ambiances of Ar and admixtures of Ar and N2 at 500 mbar pressure. Immediate formation of arc plasma is observed for Ar ambiance. On the other hand, considerable delay in formation of arc plasma is observed for the admixtures of Ar and N2. The arc plasma formation time is found to increase with increasing N2 concentration in the admixture. Transmission electron microscope and X-ray diffraction were used to characterize the produced nanoparticles. Among the nanoparticles produced in different ambient gas species, the nanoparticles produced in Ar ambiance have higher particle size compared to admixtures of Ar and N2. The particle size is found to reduce with increasing N2 concentration in the ambiance. Difference in arc plasma formation time is probably the factor that gives rise to the difference in the particle sizes.

Fabrication of Copper Nanoparticles in a Thick Polyimide Film Cured by Rapid Thermal Annealing

We investigated the imidization of a polyimide (PI) and the formation of Cu nanoparticles in a PI film by curinga precursor of PI (polyamic acid (PAA) dissolved in n-methyl-2-pyrrolidinone) in a reducing atmosphere in the rapid thermal annealing (RTA) system. A Cu film was deposited onto the SiO2/Si substrate, and the PAA was spin-coated onto the Cu film. After the PAA reacted with the Cu film, soft-baking was performed to evaporate the solvent. Finally, the PAA was imidized to PI at 450 degrees C by curing in a reducing atmosphere with the RTA. Fourier transform infrared spectroscopy showed that the PAA was successfully imidized by the RTA. X-ray diffraction patterns revealed that Cu nanoparticles formed by RTA curing at 450 degrees C for 5 minutes in a reducing atmosphere, and transmission electron microscopy showed that Cu nanoparticles about 6.5 nm in size were uniformly dispersed in the PI film. Curing by RTA is an attractive method because it takes only a few minutes.

Preparation of Cu nanoparticles with NaBH4 by aqueous reduction method

Cu nanoparticles were prepared by reducing Cu2+ ions with NaBH4 in alkaline solution. The effects of NaBH4 concentration and dripping rate on the formation of Cu nanoparticles were studied. The optimum conditions are found to be 0.2 mol/L Cu2+, solution with pH=12, temperature of 313 K and 1% gelatin as dispersant, to which 0.4 mol/L NaBH4 is added at a dripping rate of 50 mL/min. NH3·H2O is found to be the optimal complexant to form the Cu precursor. A series experiments were conducted to study the reaction process at different time points.

Sacrificial seed mediated synthesis of copper nanopots by a modified polyol process

A novel modified polyol process has been developed for the synthesis of hollow copper nanopots. Cobalt hydrazine complex was employed for the preparation of cobalt nanoparticles (NPs), which in turn acted as sacrificial seeds for the production of Cu nanopots and nanocups. The reduction of Cu2+ to Cu0 was observed by the colour change from bluish green to dark brownish red. The reaction was followed with the help of a UV–Vis spectrometer. A surface plasmon band at 558 nm indicated the formation of Cu NPs. Chemical characterisation was carried out using inductively coupled plasma optical emission spectrometer and Leco gas analysers, CS-444 and TC-600. Crystal structure was obtained by carrying out X-ray diffraction studies and it showed a face centred cubic structure. Particle size and morphology were obtained from scanning electron microscope. On average, copper nanopots of size 72 nm could be obtained using this method.

Formation of Cu nanoparticles in layered Bi2Te3 and their effect on ZT enhancement

Compounds of CuxBi2Te3 (0 ≤ x ≤ 0.1) were studied to measure the effect of Cu intercalation on their thermoelectric properties. HR-TEM images of freshly fractured surfaces of Cu0.07Bi2Te3 showed that Cu nanoparticles formed in the van der Waals gaps between Te layers in Bi2Te3. Such nanoparticles acted as electron donors, changing the native p-type character of Bi2Te3 to n-type. They also acted as phonon scatters, reducing thermal conductivity. Cu0.07Bi2Te3 had high electrical conductivity of 681 S cm−1 and Seebeck coefficient of −236 μV K−1 with low thermal conductivity of 1.0 W m−1 K−1, thus enhancing the figure of merit, ZT, to 1.15 at approximately 300 K. The intercalation of metal nanoparticles between Te layers in Bi2Te3 is a promising strategy for the preparation of highly efficient n-type thermoelectric materials.

The annealing behavior of Cu nanoparticles in Ar-ion implanted spinel

Abstract Magnesium aluminate spinel crystals (MgAl 2 O 4 (1 1 0)) deposited with 30 nm Cu film on surface were implanted with 110 keV Ar-ions to a fluence of 1.0 × 10 17 ions/cm 2 at 350 °C, and then annealed in vacuum condition at the temperature of 500, 600, 700, 800 and 900 °C for 1 h, respectively. Ultraviolet–visible spectrometry (UV–VIS), scanning electron microscopy (SEM), Rutherford backscattering (RBS) and transmission electron microscopy (TEM) were adopted to analyze the specimens. After implantation, the appearance of surface plasmon resonance (SPR) absorbance peak in the UV–VIS spectrum indicated the formation of Cu nanoparticles, and the TEM results for 500 °C also confirmed the formation of Cu nanoparticles at near-surface region. In annealing process, The SPR absorbance intensity increased at 500 and 700 °C, decreased with a blue shift of the peak position at 600 and 800 °C, and the peak disappeared at 900 °C. The SPR absorbance intensity evolution with temperature was discussed combined with other measurement results (RBS, SEM and TEM).

A MEMS Reactor for Atomic-Scale Microscopy of Nanomaterials Under Industrially Relevant Conditions

We present a microelectromechanical systems (MEMS) nanoreactor that enables high-resolution transmission electron microscopy (TEM) (HRTEM) of nanostructured materials with atomic-scale resolution during exposure to reactive gases at 1 atm of pressure. This pressure exceeds that of existing HRTEM systems by a factor of 100, thereby entering a pressure range that is relevant to industrial purposes. The nanoreactor integrates a shallow flow channel (35 ?m high) with a microheater and with an array of electron transparent windows of silicon nitride. The windows are only 10 nm thick but are mechanically robust. The heater has the geometry of a microhotplate and is made of Pt embedded in a silicon nitride membrane. To interface the nanoreactor, a dedicated TEM specimen holder has been developed. The performance is demonstrated by the live formation of Cu nanoparticles in a catalyst for the production of methanol. At 120 kPa and for temperatures of up to 500°C , the formation of these nanoparticles can be observed clearly and with an exceptionally low thermal drift. HRTEM images of the nanoparticles show atomic lattice fringes with spacings down to 0.18 nm.

Photolysis, photochromism, and formation of Cu nanoparticles in CuCl films with the help of hydrogen photosensitization

Employment of a CuCl-WO3 double-layer structure makes it possible to carry out photolysis in CuCl films. First hydrogen atoms are detached under illumination from hydrogen containing molecules (hydrogen donors), previously adsorbed on the WO3 surface; hydrogen atoms migrate then to the CuCl surface providing hydrogen sensitization simultaneous to the illumination, which yields the photolysis, formation of Cu nanoparticles, and photochromism in the CuCl films.

CuOx−TiO2 Photocatalysts for H2 Production from Ethanol and Glycerol Solutions

Hydrogen production by photocatalytic reforming of aqueous solutions of ethanol and glycerol was studied with the use of impregnated and embedded CuO(x)/TiO(2) photocatalysts. Embedded CuO(x)@TiO(2) was prepared by a water-in-oil microemulsion method, which consists in the formation of Cu nanoparticles in the microemulsion followed by controlled hydrolysis and condensation of tetraisopropyl orthotitanate with the aim of covering the protected metal particles with a surrounding layer of porous titanium oxyhydroxide. Mild calcination leads to the complete removal of the organic residues, the crystallization of TiO(2), and an unavoidable oxidation of copper. Two reference samples were prepared by classical wet impregnation of preformed TiO(2) with different ratios of anatase, rutile, and brookite polymorphs. The two supports were prepared by sol-gel (TiO(2)-SG) and microemulsion (TiO(2)-ME) methods. Superior performances have been observed for the embedded system, which shows higher hydrogen production rates with respect to the impregnated systems using either ethanol or glycerol as sacrificial molecules. Deep structural characterization of the materials has been performed by coupling high resolution transmission electron microscopy (HRTEM), high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM), X-ray absorption fine structure (XAFS), and electron paramagnetic resonance (EPR) techniques. Correlation between copper oxidation state and its dispersion and reactivity has been attempted. Finally, the stability of the CuO(x)/TiO(2) catalysts was also studied with respect to carbonaceous deposits and copper leaching.

Hyperbranched Polyamine/Cu Nanoparticles for Epoxy Thermoset

Copper nanoparticles have been synthesized in a colloidal solution of hyperbranched polyamine by a reductive technique. The formation of Cu nanoparticles was confirmed from UV, FT-IR, XRD and TEM studies. This colloidal solution of hyperbranched polyamine/Cu nanoparticles as well as hyperbranched polyamine alone have been used to cure commercially available bisphenol-A based epoxy resin at different dose levels (10–30 phr) with and without commercial poly(amido amine) hardener. The drying time, hardness, impact and chemical resistance of the cured epoxy resin have been investigated. The studies on morphology, thermostability and flame retardancy of cured films indicate the uniform distribution of different phases, high thermostability (up to 250°C) and self extinguishing characteristics respectively. Effective antifungal activity of the pure colloidal solution of hyperbranched polyamine/Cu-nanoparticles against Candida albicans fungus was observed.

Study of surface plasmon resonance of Cu@Cu2O core–shell nanoparticles by Mie theory

Cu@Cu2O core–shell nanoparticles on a-C : H thin films are prepared by co-deposition of RF-sputtering and RF-PECVD. Samples with different copper concentrations are grown. The copper content of films increases with reduction in initial pressure and rises with increasing RF power. When the Cu/C ratio reaches 0.5, the surface plasmon resonance (SPR) peak that is a signature of the formation of Cu nanoparticles appears in visible spectra of these films. X-ray photoelectron spectroscopy (XPS) characterization indicates that the surface of the copper nanoparticles oxidizes when they are exposed to air. The results are indicative that the shell of the nanoparticle is mainly the Cu2O phase that is stabilized with CuO covering a thin layer on the Cu2O shell. Using Mie theory for the SPR peak in visible spectra, the size of the copper cores and copper oxide shell, the dielectric constant of shells and the plasma frequency are estimated. The Mie theory estimation indicates that the SPR peak is damped by decreasing the size of copper cores. The SPR peak appears in visible spectra for a copper core with a diameter larger than 2 nm. This empirical result confirms the reported calculation result. The shift in the energy of the SPR peak follows the shift in the plasma frequency with respect to the reported value for copper bulk. The dielectric constant of the combined Cu2O shells and the CuO cover layer is larger than the reported value for Cu2O nanoparticles and increases with increasing CuO/Cu2O ratio.

Formation of Cu Nanoparticles by Electroless Deposition Using Aqueous CuO Suspension

nanoparticles approximately in diameter were electrochemically formed by liquid-phase reduction (i.e., electroless deposition) using hydrazine as a reducing agent and dispersing barely soluble particles in aqueous solution at . The addition of gelatin into the reaction suspension prevented the coagulation of nanoparticles and also sufficiently suppressed particle growth. Direct reduction of particles did not occur due to the adhesion of gelatin on the surface of particles, and nanoparticles were deposited by the reduction of ions dissolved in solution from particles. The solubility of particles was extremely small (of the order of at ) in aqueous solution of 12, which regulated the size of particles. nanoparticles approximately in diameter were obtained at , while nanoparticles of two different sizes (less than and about ) were obtained at . The proportion of the smaller particles increased with increasing reaction temperature, and the smaller particles were easily separated by centrifugal classification without aggregation. The formation mechanism of nanoparticles was discussed from the viewpoint of thermodynamics with in situ monitoring of deposition and immersion potential.

Strain Sensitivity in Ion-implanted Polymers

AbstractIon implantation process was used to fabricate ultra-thin conducting films in inert polymers and to tailor the surface electrical properties for strain gauge applications. To this aim, polycarbonate substrates were irradiated at room temperature with low energy Cu+ ions of 60 keV at 1 μA/cm2 and with doses ranging from 1×1016 to 1×1017 ions/cm2. XRD and TEM measurements on the nanocomposite surfaces demonstrated the spontaneous precipitation of Cu nanocrystals at 1×1016 ions/cm2 fluence. These nanocrystals were located at about 50 nm - 80 nm below the polymer surface in accordance with TRIM calculations. Optical absorption spectra exhibited a surface plasmon resonance (SPR) at 2 eV, in accordance with the formation of Cu nanoparticles. For doses of 5×1016 ions/cm2 the formation of a continuous nanocrystalline Cu subsurface film occurred and a well pronounced SPR peak was observed. Otherwise, for higher doses (1×1017 ions/cm2) a damaged and structurally disordered film was obtained and the SPR peak was smeared out. Electrical conductivity measurements clearly indicated a reduced electrical resistance for the samples implanted with a doses up to 5×1016 ions/cm2, whereas higher doses (1×1017 ions/cm2) resulted detrimental for the electrical properties, probably due to the radiation induced damage. The dependence of electrical resistance from surface load was evaluated during compression tests up to 3 MPa. A significant linear variation of the electrical resistance with the surface load was found and could be related to the changes in the spatial distribution of nanoparticles inside the copper film.

Synthesis of well-defined copper nanocubes by a one-pot solution process

A simple one-pot solution-phase method was developed to synthesizewell-defined copper nanocubes with an edge length in the range of100 ± 25 nm. Copper nanocubes were produced by using ascorbic acid as a reducing agent andpoly(vinylpyrrolidone) (PVP) as a capping agent. X-ray diffraction (XRD), UV–visspectroscopy (UV–vis), scanning electron microscopy (SEM) and transmission electronmicroscopy (TEM) as well as selected-area electron diffraction (SAED) were used tocharacterize the resulting nanoparticles. The influence of concentration, temperature andadditives on the formation of Cu nanoparticles was investigated. Some nano-polyhedra andnanospheres were also fabricated. Shape-controlled synthesis of copper nanoparticles waspartially achieved.