Attachment Of Cu Research Articles

Biocomposite based on N-maleated chitosan immobilized in amino-carbamated alginate matrix for effective biosorption of Cu(II)

Abstract Synthesis of a biocomposite based on N-maleated chitosan immobilized in amino-carbamated alginate matrix (NMC-PSC) was carried out. Facile chemical modifications of sodium alginate and chitosan were executed using maleic anhydride and 4-phenylsemicarbazide as chemical modifiers, respectively. NMC-PSC hydrogel beads were employed for Cu(II) biosorption from aqueous media. Study of surface characterization, morphology and chemical structure of the sorbent indicated the successful surface functionalization and attachment of Cu(II) ions. Sorption parameters like pH, time of contact, sorbent dosage and adsorbate content significantly influenced the sorption capacity. Kinetic results demonstrated that copper sorption on NMC-PSC was governed by chemisorption and ion-exchange rather than merely mass transfer. Equilibrium sorption data closely fitted with Langmuir model and maximum Langmuir monolayer binding capacity (q m ) was determined as 207 mg/g. The negative ΔG o values indicated the spontaneity of Cu(II) sorption process while ΔH o and ΔS o parameters indicated the exothermic nature of sorption which proceeds with rise in entropy.

Directional growth of quasi-2D Cu2O monocrystals on rGO membranes in aqueous environments.

The preparation technology of unconventional low-dimensional Cu2O monocrystals, which exhibit specific crystal planes and present significantly unique interfacial and physicochemical properties, is attracting increasing attention and interest. Herein, by integrating a high-temperature oxidation process under vacuum and a pure-water incubation process under ambient conditions, we propose the self-assembled growth and synthesis of quasi-two-dimensional Cu2O monocrystals on reduced graphene oxide (rGO) membranes. The prepared Cu2O crystals have a single (110) crystal plane, regular rectangular morphology, and potentially well conductivity. Experimental and theoretical results suggest that this assembly is attributed to the pre-nucleation clusters aggregation and directional attachment of Cu and O on the rGO membranes in aqueous environment and cation-π interactions between the (110) crystal plane of Cu2O and rGO surface. Our findings offer a potential avenue for the discovery and design of advanced low-dimensional single-crystal materials with specific interfacial properties in a pure aqueous environment.

Characterization, conductivity studies, dielectric properties, and gas sensing performance of in situ polymerized polyindole/copper alumina nanocomposites

AbstractConducting polymer composites of polyindole (PIN) and copper–alumina (Cu–Al2O3) nanocomposites were synthesized by in situ polymerization of indole with different contents of Cu–Al2O3 nanoparticles. The polymer nanocomposites were characterized by Fourier transform infrared (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X‐ray (EDX), transmission electron microscope (TEM), differential scanning calorimetry, thermogravimetric analysis, and ammonia gas sensing performance was also analyzed. FTIR and XRD studies revealed the attachment of Cu–Al2O3 in the molecular chain of PIN. The presence of bright trapezoid channels and variation in morphology for different loading of nanoparticles were confirmed by SEM and TEM. The attachment of Cu–Al2O3 nanoparticles in the PIN matrix was confirmed through EDX spectroscopy. The glass transition temperature and thermal stability of the composites were greatly enhanced with the loading of Cu–Al2O3. Enhancement in alternating current conductivity, dielectric constant and the current–voltage characteristics of the prepared composite revealed the semiconducting nature of the system with an increase in the loading of nanoparticles. Also, nanocomposite exhibited an excellent sensitivity and fast response to ammonia gas. The evaluated result of the present study suggested that Cu–Al2O3 reinforced PIN hybrid is a good candidate for the fabrication of electrochemical devices.

Side‐chain glycylglycine‐based polymer for simultaneous sensing and removal of copper(II) from aqueous medium

ABSTRACTSince glycylglycine (Gly‐Gly) residue in the N‐terminal region of human prion protein, a copper binding protein, binds with Cu(II), N‐terminus Gly‐Gly side‐chain containing water soluble block copolymer was synthesized and used for simultaneous sensing and removal of Cu(II) ion from aqueous medium. The polymer has amide nitrogen atom and ester carbonyl group as potential binding sites in the side‐chain Gly‐Gly pendants. Job's plot experiment confirms 2:1 binding stoichiometry of polymer with Cu(II). This polymer is able to sense parts per billion level of Cu(II) very selectively in an aqueous medium and remove Cu(II) ions quantitatively by precipitating out the Cu(II) via complex formation in the pH range 7–9. The binding mode of polymer with Cu(II) in polymer‐Cu(II) complex was characterized by 1H NMR, FTIR, and UV–vis spectroscopy. The attachment of Cu(II) in the polymer‐Cu(II) complex was confirmed by cyclic voltammetry experiment. Cu(II) release from the complex was achieved at pH 5 due to the protonation of amide nitrogen atoms in the Gly‐Gly moiety. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 914–921

Development and validation of an ecofriendly chemiluminescence method for the determination of citalopram in pharmaceutical preparations using Cu2+-grafted Oxidized multiwall carbon nanotubes

Anovel and sensitive chemiluminescence (CL) method was developed and validated for the determination of citalopram in bulk dosage form and in pharmaceutical preparations. The method is based on the use of Cu 2+ -grafted oxidized multiwall carbon nanotubes (Cu/ox-MWCNTs). The weak CL signal arising fromthe reaction of an alkaline luminol-H 2 O 2 system was significantly enhanced by the addition of citalopram in the presence of ox-MWCNTs/Cu 2+ . Furthermore, ox-MWCNTs/Cu 2+ exhibited exceptional catalytic activity towards the oxidation of luminol in the luminol-H 2 O 2 CL reaction. Multiwalled carbon nanotubes (MWCNTs) were characterized by scanning electron microscopy (SEM), which also showed the attachment of Cu 2+ toMWCNTs. Various factors affecting CL intensity were carefully investigated and optimized for citalopram quantitation. The CL intensity was proportional to citalopram concentration in the range 0.2–8.0 μ g mL –1 , with a correlation coefficient of 0.996. The limit of detection (LOD) and limit of quantification were 2.29 × 10 –5 μ g mL –1 and 7.64 × 10 –5 μ g mL –1 , respectively, and its reproducibility was satisfactory with a relative standard deviation (RSD) of 2.59 % (n = 5). The interference effects of common excipients were studied, and the developed method was effectively applied for the determination of citalopram in pure formand in pharmaceutical preparations. Percentage recoveries were calculated and ranged from 98.67 to 101.46 % for the pure form and from 97.38 to 101.72 % for pharmaceutical preparations. Keywords: Chemiluminescence, Citalopram, Luminol, oxidized multiwall carbon nanotubes

Wear Behavior of Lubricant-Conditioned Copper Rails and Armatures in a Railgun

A solid lubricating interfacial compound (SLIC) has been used to condition the rails and armature of the NRL decoy launcher, a low-speed (100-140 m/s) railgun. The study tested the hypothesis that a very thin film would protect the sliding electrical contacts against damage by friction, wear, and arcing. The film, obtained by rubbing the rail and armature staples with a PTFE-based composite, dramatically improved launch reliability, increased projectile speed, and reduced armature damage and armature/rail arcing. High-speed (68 kfps) videos taken down the bore showed that the SLIC treatment could suppress light emissions from start of launch until the muzzle flash. The treatment also reduced or completely suppressed the spikes in the muzzle-voltage traces. Optical microscopy identified the damage mechanisms responsible for both rail and armature wear. The SLIC treatment reduced or eliminated arc damage in the breech, attachment of Cu shards to the rail, and both melting and abrasive wear of the staples. The effect of the rubbed film on wear behavior is discussed.

Structural analogues of the bimetallic reaction center in acetyl CoA synthase: a Ni--Ni model with bound CO.

Models for the active site of the acetyl CoA synthase (ACS) were synthesized by attachment of Cu+ and Ni(0) to nickel diaminodithiolate (S2N2) and diamidodithiolate (S2N2') complexes. The Ni-Ni species form stable CO adducts, i.e., [{(CO)2Ni}{NiS2N2'}]2-, whereas the Cu-NiS2N2 and Cu-NiS2N2' models do not. These results provide supporting evidence for a biological role for reduced nickel in ACS.

Reactions between Glycolic Acid and Cu+in the Gas Phase. An Experimental and Theoretical Study

The gas-phase reactions between glycolic acid and Cu+ have been investigated by means of mass spectrometry techniques. The mass-analyzed ion kinetic energy (MIKE) spectrum reveals that the adduct ions [HOCH2COOH−Cu+] decompose spontaneously by losing CH2O2, CO, and H2O. A minor fragmentation corresponding to the loss of H2 is also observed. The structures and bonding characteristics of the different complexes involved in the glycolic acid−Cu+ potential energy surface (PES) have been theoretically studied by density functional theory (DFT) calculations carried out at the B3LYP/6-311+G(2df,2p)//B3LYP/6-31G* level. The attachment of Cu+ to glycolic acid gives rise to two energetically degenerated structures: a chelated form in which Cu+ interacts with the carbonyl oxygen and the hydroxyl oxygen atoms and another one in which the attachment of Cu+ takes place exclusively at the carbonyl oxygen atom. The estimated glycolic acid−Cu+ binding energy is 222 kJ/mol. Different mechanisms for the spontaneous fragmentations observed experimentally are proposed. The main conclusion is that the loss of 46 u should correspond dominantly to the loss of formic acid and in a lower proportion to the loss of CO + H2O.

Gas-Phase Chemistry of Ethyl and Vinyl Amines, Phosphines, and Arsines: A DFT Study of the Structure and Stability of Their Cu+Complexes

The B3LYP density functional approach has been used to calculate the Cu+ binding energies of ethyl and vinyl amines, phosphines, and arsines. Geometries were fully optimized at the B3LYP/6-311G(d,p) level, and the final energies were obtained in B3LYP/6-311+G(2df,2p) single-point calculations. Significant differences between nitrogen-, phosphorus-, and arsenic-containing compounds have been found. For ethyl derivatives, the global minimum corresponds to the attachment of Cu+ to the heteroatom. However, whereas for P and As derivatives of agostic complexes in which the metal cation interacts with the hydrogen atoms of the XH2 or the CH2 groups are found to be stable, they are not for ethylamine. For vinylamine, attachment to Cβ is favored with respect to attachment to the heteroatom, whereas vinylphosphine and vinylarsine behave as P and As bases, respectively. The Cu+ basicity trends also differ from those found for the corresponding proton affinities. Thus, although ethylamine is more basic than ethylphosphine and ethylarsine when the reference acid is H+, ethylphosphine is the most basic compound when the reference acid is Cu+. For the vinyl derivatives, the Cu+ binding energies follow the trend P > As > N when only attachment to the heteroatom is considered, whereas the proton affinities follow the sequence N > P > As.

Interaction of porphyrin and sapphyrin macrocycles with nucleobases and nucleosides: Spectroscopic, quantum chemical and chromatographic investigation

Novel oligopyrrole macrocycle-based sorbents were prepared via amide covalent bonding of carboxylic acids of porphyrin and sapphyrin derivatives to 3-aminopropyl silica. Covalent attachment of Cu(II)-tetraphenylporphyrin formyl-derivative was performed by amine linkage. Prepared sorbents were characterized by Raman spectroscopy and elemental analysis. Retention behavior of nucleobases and nucleosides was investigated by HPLC. UV–VIS and 1 H NMR titrations were used to study the role of oligopyrrol macrocyclic receptors for selective recognition of adenine, cytosine, thymine and uracil and their nucleoside forms. The spectroscopic results were compared with quantum chemical calculations at semiempirical level and with the data obtained by HPLC measurements. Obtained data suggest that an aromatic π–π stacking interactions govern the HPLC separation. A different behavior was found for purine and pyrimidine bases. An introduction of Cu(II) into porphyrin macrocycle led to a dramatic increase of separation efficiency, probably due to an increase of interaction energy.

Reactions of Urea with Cu+in the Gas Phase: An Experimental and Theoretical Study

The gas-phase reactions between Cu+ and urea have been investigated by means of mass spectrometry techniques. The primary products formed in the ion source correspond to [urea−Cu]+, [(urea)2−Cu]+, and [Cu+,C,N2,H2] complexes. The MIKE spectrum of [urea−Cu]+ complex shows several spontaneous losses, namely, NH3 and HNCO. A very weak peak corresponding to the loss of H2O is also observed, as well as a minor fragmentation of the adduct ion to yield Cu+. The structures and bonding characteristics of the different complexes involved in the urea−Cu+ potential energy surface (PES) were investigated using density functional theory (DFT) at the B3LYP level of theory and a valence triple-ζ. Attachment of Cu+ takes place preferentially at the carbonyl oxygen atom, while attachment at the amino group is 12.4 kcal/mol less exothermic. Insertion of the metal cation into the C−N bonds of the neutral is predicted to be slightly exothermic, in contrast with what was found for formamide and guanidine. The estimated urea−Cu+ binding energy (62.3 kcal/mol) is 6.0 kcal/mol greater than that of formamide. The exploration of the PES indicates that there are several reaction paths leading to the loss of ammonia yielding as product ions HNCOCu+ complexes where the metal cation is attached either to the oxygen or the nitrogen of the HNCO species. Also several reaction paths can be envisaged for the loss of HNCO, in which bisligated [HNCO−Cu−NH3]+ and [OC(NH)−Cu−NH3]+ complexes play an important role.

Structure and Bonding of Cu(II)–Glutamate Complexes at the γ-Al2O3–Water Interface

Thecomposition and mode of attachment of Cu(II) complexes at the γ-Al2O3–water interface in suspensions containing a simple amino acid (glutamate) were characterized with EXAFS and FTIR spectroscopies. The spectroscopic results indicate that two types of Cu(II)–glutamate–alumina interactions are primarily responsible for Cu(II) and glutamate uptake between pH 4 and 9. In acidic suspensions of alumina, glutamate forms a bridge between Cu(II) ions and the (hydr)oxide surface (Type B complex). In this Type B surface complex, Cu(II) is bonded to amino acid headgroups (i.e., +H3NCHRCOO−) of two glutamate molecules. Spectroscopic and ionic strength dependent uptake results are combined to propose that the nonbonded side chain carboxylate groups of this complex are attracted to the oxide surface through long-range forces, leading to enhanced Cu(II) uptake relative to the glutamate-free system. In alkaline suspensions the relative amount of surface-bound Cu(II) complexed by glutamate decreases, and a direct Cu(II)–surface bond becomes the dominant mode of attachment (Type A complex). These surface complexes differ markedly from the species found in the alumina-free Cu(II)–glutamate aqueous system under similar solution conditions, where Cu(H2O)2+6 and Cu(glutamate)2−2 are the dominant species in acidic and alkaline solutions, respectively. Based on these spectroscopic results, surface complexation reactions are proposed for the Cu(II) and glutamate ternary interactions with the alumina surface in this system. Similarities between the results of this study and Cu(II) uptake behavior and complexation in the presence of natural organic material (NOM) indicate that Cu(II)–glutamate interactions mimic those in more complex Cu(II)–NOM–mineral–water systems.

Reactions between Guanidine and Cu+in the Gas Phase. An Experimental and Theoretical Study

Mass spectrometry measurements reveal that the reactions between guanidine and Cu+ in the gas phase leads predominantly to the loss of ammonia. The corresponding mechanisms were investigated by means of DFT calculations at the B3LYP/6-311+G(2df,2p)//B3LYP/6-311G(d,p) level. The attachment of Cu+ takes place preferentially at the imino nitrogen, while attachment at the amino leads to a local minimum which lies almost 26 kcal/mol higher in energy. The estimated guanidine−Cu+ binding energy is 77.9 kcal/mol. Hence, guanidine is predicted to be a stronger base than ammonia when the reference acid is Cu+, although this basicity difference is about 11 kcal/mol smaller than that found when the reference acid is H+. Two possible reaction channels, with almost equal activation barriers, lead to the loss of NH3. One of them yields the H2N−CN−Cu+ complex while the other yields the HNCNHCu+ complex. The structures and bonding characteristics of both products are discussed. Their estimated heats of formation are 225 ± 2 and 237 ± 2 kcal/mol, respectively. The structures and the relative stabilities of the complexes which can be formed by the solvation of these two products by ammonia have been also investigated since they are essential to explain the unimolecular NH3-loss processes observed.

The sorption of copper(II), manganese(II), zinc(II) and arsenic(III) onto human hair, and their desorption

Human hair has been studied in relation to sorption from aqueous solutions of Cu 2+, Mn 2+, Zn 2+ and AsO 3 3−. At an equilibrium concentration of 0.3 μg ml −1 the sorptions are relatively low for Mn (1.1 μg g −1) and As (0.1 μg g −1), and higher for Zn (10 μg g −1) and Cu (35 μg g −1). But only in the case of copper is the sorption significant relative to the indigenous levels of the elements in the hair. The greater sorption of Cu 2+ may be correlated with better binding to the hair fibre, probably both electrostatically and to the sulphur in the keratin. There appears to be at least three modes of attachment, or three mechanisms of attachment of Cu 2+ to the hair. An inter-element effect was observed, where Cu 2+ severely inhibits the sorption of Zn 2+ and Mn 2+. Also the total sorption of Cu 2+ is reduced on zinc or manganese-treated hair. Some comments are made regarding the results and the problems of exogenous contamination of human hair.