Copper Atoms Research Articles

Hidden Impurities Generate False Positives in Single Atom Catalyst Imaging.

Single-atom catalysts (SACs) are an emerging class of materials, leveraging maximum atom utilization and distinctive structural and electronic properties to bridge heterogeneous and homogeneous catalysis. Direct imaging methods, such as aberration-corrected high-angle annular dark-field scanning transmission electron microscopy, are commonly applied to confirm the atomic dispersion of active sites. However, interpretations of data from these techniques can be challenging due to simultaneous contributions to intensity from impurities introduced during synthesis processes, as well as any variation in position relative to the focal plane of the electron beam. To address this matter, this paper presents a comprehensive study on two representative SACs containing isolated nickel or copper atoms. Spectroscopic techniques, including X-ray absorption spectroscopy, were employed to prove the high metal dispersion of the catalytic atoms. Employing scanning transmission electron microscopy imaging combined with single-atom-sensitive electron energy loss spectroscopy, we scrutinized thin specimens of the catalysts to provide an unambiguous chemical identification of the observed single-atom species and thereby distinguish impurities from active sites at the single-atom level. Overall, the study underscores the complexity of SACs characterization and establishes the importance of the use of spectroscopy in tandem with imaging at atomic resolution to fully and reliably characterize single-atom catalysts.

Production of Cu/Zn Nanoparticles by Pulsed Laser Ablation in Liquids and Sintered Cu/Zn Alloy

As a preliminary step to establish technology for fabricating High-Entropy Alloys (HEAs) that can make a large-scale HEA using a pulse laser with high peak intensity and high-repetition in the future, we fabricated alloys in which two types of metal atom are mixed close together in the order of nanometers. For the method to produce the alloy, metal alloy nanoparticles were prepared by irradiating the material in liquid with focused high-repetition Q-switched laser pulses using an in-liquid laser ablation method. When brass powder was used as an original material, analysis results by TEM showed that numerous nanoparticles mixed with copper and zinc atoms could be produced. Furthermore, it was clarified by SEM EDS that copper and zinc atoms in the nanoalloy were maintained at a ratio of 3:1 in sintered alloy, and that the atoms were spatially uniformly distributed over a wide range in sintered metal.

Substituent Modulated Electronic Properties of Cu(I) Active Site in Metal–Organic Halides for Boosting Hydrogen Evolution Reaction†

Comprehensive SummaryDevelopment of heterogeneous molecular photocatalysts for promising light‐driven hydrogen evolution reaction (HER) is highly demanding but still challenging. Here, we report the blue‐greenish emitting dinuclear metal–organic halides as photocatalyst by incorporating site‐specific single copper(I) atoms that exhibit an efficient carbon‐negative H2 production. Interestingly, the electronic properties, including the spin and charge density of central Cu(I) active site, can be triggered by substituent modulation in metal–organic halides, which greatly affect the exciton dissociation kinetics and thus the HER reactivity. The optimized spin density in these heterogeneous photocatalysts drastically boosts the hydrogen production rate from 1250 to 3130 μmol·g–1·h–1. Our molecular strategy provides a platform that rationally facilitates electronic modulation of copper(I) atoms, tunes the macroscopic optoelectronic properties of photocatalysts and boosts carbon‐negative HER activity, extending the boundaries of conventional molecular‐based photocatalysts.

Tungsten, copper and cobalt-single metal atom oxides embedded CeO2-MnO2-rGO nanorods as electrocatalysts for efficient oxygen evolution reaction

BackgroundAn important aspect of energy conversion and storage technology is primarily based on the electrocatalytic oxygen evolution process (OER). MethodHere, we present the newly designed synthesis of an improved variety of WCuCo-CeO2-MnO2-R-3 nanocomposites, to enhance OER by incorporating the reduced graphene oxide (rGO), and SMAO of W, Cu, and Co with the nanorods of CeO2-MnO2 materials. Interestingly, the higher density of SMAO (W, Cu, and Co), atomic utilization and electron transfer layer of rGO influenced the CeO2-MnO2 nanorods with remarkably superior electrocatalytic OER activity. Significant findingsThis makes WCuCo-CeO2-MnO2-R-3 achieve 10 mA cm-2 with an overpotential of 275 mV and a lower Tafel slop of 64.46 mV dec‑1. The higher number of SMAO (W, Cu, and Co) species close to the catalyst surface served as potential active sites assembly to enhance the OER activity by improving the chemical and electrochemical steps during the OER process. The chronoamperometry test revealed that the WCuCo-CeO2-MnO2-R-3 nanocomposite is not degrade in a 1 M KOH solution for 24 h, and it is stable up to 2000 CV cycles. In order to create very effective catalysts for OER, the DFT theoretical results shed light on the connection between the catalytic characteristics of metal oxide structures and their inherent electronic configuration.

Simulation of the Diffusion of Copper Atom on Graphene by Molecular Dynamics

The results of studying the effect of geometric and thermodynamic parameters of thermal evaporation and copper deposition on graphene lying on the Cu(111) surface on the adsorption of copper atoms, as well as their surface diffusion, are presented. The simulation was carried out by classical molecular dynamics using chains of Nose–Hoover thermostats. Interatomic interactions were determined by the Tersoff–Brenner, Rosato–Gillop–Legrand, and modified Morse potentials. A simple criterion for the thermalization of adatoms on graphene lying on a Cu(111) surface was formulated and tested. The average length and mean time of free path of a copper atom before and after thermalization at low (7 K) and room temperatures were studied for two evaporation temperatures. The probability of adsorption of a copper atom was found. The distributions along the directions of motion of adatoms during equilibrium diffusion were constructed. The distributions of the free path length and time were shown to have an exponential form. The influence of the Cu(111) substrate on the diffusion of the Cu atom on graphene was studied. The results obtained can be used to simulate the growth of copper nanoclusters on graphene by the kinetic Monte Carlo method.

Hydrogen adsorption, desorption, sensor and storage properties of Cu doped / decorated boron nitride nanocone materials: A density functional theory and molecular dynamic study

The hydrogen storage and sensor properties of Cu-modified boron nitride nanocone (BNNC) structure were comprehensively investigated using the density functional theory method (DFT). By replacing nitrogen atoms with copper atoms on the BNNC structure, the hydrogen molecule's adsorption enthalpy and Gibbs free energy values were calculated as −48.6 and −16.9 kJ/mol, respectively. 4 Cu-doped BNNC structure achieved a notable hydrogen storage capacity of 5.38 wt%. The molecular dynamics calculations demonstrate that the structure modified with four Cu atoms maintains its dynamic stability. Furthermore, this study reveals that the desorption temperatures tend to rise with an increase in the number of adsorbed hydrogen molecules, and the average desorption temperature under 1 atm pressure is determined to be 332 K. The changes of work function values after hydrogen adsorption point out that the Cu-modified BNNC has Φ-sensor feature. Overall, Cu-modified BNNC structures show promising potential as hydrogen storage materials in ambient conditions.

Atomic sawtooth-like metal films for vdW-layered single-crystal growth

Atomic sawtooth surfaces have emerged as a versatile platform for growth of single-crystal van der Waals layered materials. However, the mechanism governing the formation of single-crystal atomic sawtooth metal (copper or gold) films on hard substrates (tungsten or molybdenum) remains a puzzle. In this study, we aim to elucidate the formation mechanism of atomic sawtooth metal films during melting–solidification process. Utilizing molecular dynamics, we unveil that the solidification of the liquid copper initiates at a high-index tungsten facet with higher interfacial energy. Subsequent tungsten facets follow energetically favourable pathways of forming single-crystal atomic sawtooth copper film during the solidification process near melting temperature. Formation of atomic sawtooth copper film is guaranteed with a film thickness exceeding the grain size of polycrystalline tungsten substrate. We further demonstrate the successful growth of centimeter-scale single-crystal monolayer hexagonal boron nitride films on atomic sawtooth copper films and explore their potential as efficient oxygen barrier.

Highly Selective Electrocatalytic CO2 Conversion to Tailored Products through Precise Regulation of Hydrogenation and C-C Coupling.

The electrochemical reduction reaction of carbon dioxide (CO2RR) into valuable products offers notable economic benefits and contributes to environmental sustainability. However, precisely controlling the reaction pathways and selectively converting key intermediates pose considerable challenges. In this study, our theoretical calculations reveal that the active sites with different states of copper atoms (1-3-5-7-9) play a pivotal role in the adsorption behavior of the *CHO critical intermediate. This behavior dictates the subsequent hydrogenation and coupling steps, ultimately influencing the formation of the desired products. Consequently, we designed two model electrocatalysts comprising Cu single atoms and particles supported on CeO2. This design enables controlled *CHO intermediate transformation through either hydrogenation with *H or coupling with *CO, leading to a highly selective CO2RR. Notably, our selective control strategy tunes the Faradaic efficiency from 61.1% for ethylene (C2H4) to 61.2% for methane (CH4). Additionally, the catalyst demonstrated a high current density and remarkable stability, exceeding 500 h of operation. This work not only provides efficient catalysts for selective CO2RR but also offers valuable insights into tailoring surface chemistry and designing catalysts for precise control over catalytic processes to achieve targeted product generation in CO2RR technology.

Microstructural and antibacterial properties of copper oxide deposited on polypropylene fabric by magnetron sputtering

In this study, antibacterial coatings composed of copper and its oxides were deposited on polypropylene (PP) fabrics using magnetron sputtering. The coatings were deposited under varying oxygen partial pressures to facilitate the formation of cupric and cuprous oxides in different quantities. The formation of these oxides was confirmed by the surface morphology (Scanning Electron Microscopy [SEM]) and X-Ray Diffraction (XRD) analysis. Additionally, the antibacterial properties of the coated fabrics were evaluated. The results show that both copper and copper oxides achieved a 4-log reduction in gram-positive bacteria. Inductively Coupled Plasma Mass Spectroscopy (ICPMS) results indicated that the release of copper atoms into water from the coated fabrics was minimal, even after 30 days of immersion.

Structural and computational insights into two completely unanticipated Cu(II) and Ni(II) complexes derived from a bifunctional salamo-type bis(pyridine)-arm ligand

A bifunctional Salamo-type bis(pyridine)-arm ligand H2L (4,4′-Methyl-6,6′-pyridinenitrilomethylidyne-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol) was designed and synthesized, which can react with Cu(II) and Ni(II) nitrates to hydrolyze & break the C = N double bonds of new ligand H2L′ (4,4′-Methyl-6,6′-formal-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol). The ligand reacted with Cu(II) and Ni(II) salts to form respectively complexes [Cu(L′)] (1) and [Ni2(L′)(H2O)2](NO3)2 (2). They were elucidated by single crystal X-ray method. Many important noncovalent interactions, such as intramolecular hydrogen bonding, intermolecular hydrogen bonding and π···π stacking interactions, can be observed in the crystal structures of the two complexes. IR & UV–Vis absorbent spectroscopic analysis showed that the ligand unit is involved in the coordination with copper(II) and nickel(II) atoms, and ultraviolet titration and fluorescence titration spectra verified that the coordinating radios of the two complexes formed in liquid phase are in accordance with those of single-crystal X-ray diffraction. Through DFT theoretical calculations and electrostatic potential analyses (MESP) of the ligand and its complexes, the configuration of the ligand at the lowest energy were deeply understood, and it was demonstrated that the coordination reaction at salamo sites requires a great torsional force, and the weak intermolecular interaction force and the energy gaps of HOMO-LUMO orbitals were profoundly discussed, and the Cu(II) and Ni(II) complexes exhibit anomalous fluorescence enhancement behaviors.

Copper (II) and cobalt (II) bis(hexafluoroacetylacetonate) coordination complexes with N-styrylbenzimidazole

The study considers metal complexes based on N-styrylbenzimidazole as compounds having significant pharmacological properties The work is aimed at examining the crystal structure and electronic structure of transition metal bis(hexafluoroacetylacetonate) complexes (copper (II) (complex A) and cobalt (II) (complex B)) with N-styrylbenzimidazole using X-ray diffraction analysis and ultraviolet spectroscopy. The X-ray diffraction analysis was used to prove bipyramidal coordination in copper (II) and cobalt (II) bis(hexafluoroacetylacetonate) complexes with N-styrylbenzimidazole. The atoms of copper (II) and cobalt (II) in the complexes exhibit an unusual for β-diketonate complexes distorted square-planar coordination, while the chelate cycles in M(hfacac)2L are characterized by anomalously large kink angles. Thus, for the copper (II) bis(hexafluoroacetylacetonate) complex, the kink angle of the O3∙∙∙O4 interaction for the equatorially positioned ligand is 29.47°, while for the axially positioned ligand, the kink angle of the O1∙∙∙O2 interaction is 19.13°. For the cobalt (II) bis(hexafluoroacetylacetonate) complex, these angles are 22.10 and 19.50°, respectively. Electron spectroscopy was used to examine the electronic structure of the specified complexes. The following types of electronic transitions were identified: π→π*-transitions primarily localized on ligands, as well as transitions caused by electron transfer from the p-orbital of the hetero nitrogen atom of the styrylbenzimidazole cycle to the d-orbital of metal ions, and n→π transition localized on the imidazole ring. For each of the complexes, d-d* transitions between the molecular orbitals of the corresponding metal ion were localized in the long wavelength part of the spectrum.

A (2-(Pyrrolidin-1-yl)ethan-1-olate)(1-oxo-3-phenyl-1,4-dihydronaphthalen-2-olate) μ-Oxo-Bridged Dicopper(II) Dimeric Complex

The reaction of 2-(1H-pyrrol-1-yl)ethanol with 3-hydroxyflavone in the presence of copper(II) bromide yielded a dimeric copper(II) complex, [μ-O-(κ2-O,O-flav)(κ2-N,O-2PEO)Cu]2 (1) (flav = 3-hydroxyflavonolate; 2PEO = 2-(1H-pyrrol-1-yl)ethanolate) with both the flav and 2PEO ligands bound to the copper(II) atom in a κ2-bonding mode. The dimer is held electrostatically by bridging oxygen atoms between two copper atoms. Complex 1 was characterized by single-crystal X-ray diffraction, infrared, and UV-Vis spectroscopy, elemental analysis, and melting point determination. The complex crystallizes in the monoclinic space group P21/n (14) with cell values of a = 11.85340(10) Å, b = 8.51480(10) Å, c = 23.8453(2) Å; β = 99.3920(10)°.

Understanding the Adsorption Mechanism of BTPA, DEPA, and DPPA in the Separation of Malachite from Calcite and Quartz: DFT and Experimental Studies

The relationship between the structure of bis (2,4,4-trimethylpentyl) phosphinic acid (BTPA), diethyl phosphinic acid (DEPA), and diphenyl phosphinic acid (DPPA) on the flotation performance of malachite was investigated. Through a series of flotation experiments, density functional theory (DFT) calculations, and surface analysis methods, we aimed to deeply understand the microscopic mechanism of the interactions between these collectors and the malachite surface. The experimental results showed that BTPA exhibited excellent selectivity and flotation performance for malachite in the pH range of 5.0–11.0, significantly better than DEPA and DPPA. Surface analysis evidence from X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR) further confirmed the chemical adsorption characteristics of BTPA on the malachite surface. DFT calculations revealed that the adsorption capacity of BTPA on the malachite surface exceeds that of DEPA and DPPA. Electron transfer analysis, especially through frontier molecular orbital theory, differential charge density, PDOS, and COHP analysis, indicated that the charge transfer process from the s orbitals of oxygen atoms in the collectors to the d orbitals of copper atoms on the mineral surface is the decisive factor for the adsorption strength.

Critical Role of Cu Nanoparticle-Loaded Cu(100) Surface Structures on Structured Copper-Based Catalysts in Boosting Ethanol Generation in CO2 Electroreduction.

Presently, realizing high ethanol selectivity in CO2 electroreduction remains challenging due to difficult C-C coupling and fierce product competition. In this work, we report an innovative approach for improving the efficiency of Cu-based electrocatalysts in ethanol generation from electrocatalytic CO2 reduction using a crystal plane modification strategy. These novel Cu-based electrocatalysts were fabricated by electrochemically activating three-dimensional (3D) flower-like CuO micro/nanostructures grown in situ on copper foils and modifying with surfactants. It was demonstrated that the fabricated Cu-based electrocatalyst featured a predominantly exposed Cu(100) surface loaded with high-density Cu nanoparticles (NPs). The optimal Cu-based electrocatalyst displayed considerably improved CO2 electroreduction performance, with a Faraday efficiency of 37.9% for ethanol and a maximum Faraday efficiency of 68.0% for C2+ products at -1.4 V vs RHE in an H-cell, accompanied by a high current density of 69.9 mA·cm-2, much better than the particulate Cu-based electrocatalyst. It was unveiled that the Cu(100)-rich surface of nanoscale petals with abundant under-coordinated copper atoms from CuNPs was conducive to the formation and stabilization of key *CH3CHO and *OC2H5 intermediates, thereby promoting ethanol generation. This study highlighted the critical role of CuNP-loaded Cu(100) surface structures on structured Cu-based electrocatalysts in enhancing ethanol production for the CO2 electroreduction process.

Crystal structure, theoretical calculations, mechanoluminescence feature and antimicrobial activity based on a double-armed Salamo-type ligand and its trinuclear Cu(Ⅱ) complex

A double-armed salamo-type ligand H4L and its Cu(Ⅱ) complex have been designed and synthesized. The stoichiometric ratios of the prepared H4L and its Cu(Ⅱ) complex were structurally characterized by a variety of analytical and spectroscopic techniques, including elemental analysis, FT-IR, UV–visible, fluorescence spectroscopy, and X-ray crystal diffraction. The results showed that H4L is a linear molecule, while the Cu(Ⅱ) complex is a trinuclear structure with three copper atoms exhibiting different coordination modes due to varying coordination cavities and bridging atoms. The quantum chemical parameters and molecular structures of the H4L and the Cu(Ⅱ) complex have been theoretically calculated and studied. Using molecular electrostatic potential (MEP) and density functional theory (DFT) calculations to understand the selectivity of the H4L and the Cu(Ⅱ) complex chemistry and related reactions. Detailed energy level transitions of the H4L and the Cu(Ⅱ) complex can be determined through time-dependent density functional theory (TD-DFT) calculations. In studying the fluorescence properties of liquid and solid states, it was observed that increasing water content leads to the formation of excimer in both the H4L and its Cu(Ⅱ) complex, the ligand H4L shown good mechanoluminescence, but the Cu(Ⅱ) complex did not. We studied the antimicrobial effectiveness of the H4L and the Cu(Ⅱ) complex against E. coli., the Cu(Ⅱ) complex showed higher inhibition of the pathogenic microorganisms.

Microsolvation of cobalt, nickel, and copper atoms with ammonia: a theoretical study of the solvated electron precursors.

The s-block metals dissolved in ammonia form metal-ammonia complexes with diffuse electrons which could be used for redox catalysis. In this theoretical paper, we investigated the possibility of the d-bloc transition metals (Mn, Fe, Co, Ni, and Cu) solvated by ammonia. It has been demonstrated that both Mn and Fe atoms undergo into an oxidative reaction with NH3 forming an inserted species, HMNH2. On the contrary, the Co, Ni, and Cu atoms can accommodate four NH3, via the coordination bond, to form the first solvation sphere within C2v, D2d, and Td point groups, respectively. Addition of a fifth NH3 constitute the second solvation shell by forming hydrogen bond with the other NH3s. Interestingly, M(NH3)4 (M = Co, Ni, and Cu) is a so-called solvated electron precursor and should be considered as a monocation M(NH3)4+ kernel in tight contact with one electron distributed over its periphery. This nearly free electron could be used to capture a CO2 molecule and engages in a reduction reaction. Geometry optimization of the stationary points on the potential energy surface was performed using density functional theory - CAM-B3LYP functional including the GD3BJ dispersion contribution - in combination with the 6-311 + + G(2d, 2p) basis set for all the atoms. All first-principles calculations were performed using the Gaussian 09 quantum chemical packages. The natural electron configuration of transition atom engaged in the compounds has been found using the natural bond orbital (NBO) method. We used the EDR (electron delocalization range) approach to analyze the structure of solvated electrons in real space. We also used the electron localization function (ELF) to measure the degree of electronic localization within a chemical compound. The EDR and ELF analyses are done using the TopMod and Multiwfn packages, respectively.

Direct formation of copper nanoparticles from atoms at graphitic step edges lowers overpotential and improves selectivity of electrocatalytic CO2 reduction

A key strategy for minimizing our reliance on precious metals is to increase the fraction of surface atoms and improve the metal-support interface. In this work, we employ a solvent/ligand/counterion-free method to deposit copper in the atomic form directly onto a nanotextured surface of graphitized carbon nanofibers (GNFs). Our results demonstrate that under these conditions, copper atoms coalesce into nanoparticles securely anchored to the graphitic step edges, limiting their growth to 2–5 nm. The resultant hybrid Cu/GNF material displays high selectivity in the CO2 reduction reaction (CO2RR) for formate production with a faradaic efficiency of ~94% at -0.38 V vs RHE and a high turnover frequency of 2.78 × 106 h-1. The Cu nanoparticles adhered to the graphitic step edges significantly enhance electron transfer to CO2. Long-term CO2RR tests coupled with atomic-scale elucidation of changes in Cu/GNF reveal nanoparticles coarsening, and a simultaneous increase in the fraction of single Cu atoms. These changes in the catalyst structure make the onset of the CO2 reduction potential more negative, leading to less formate production at -0.38 V vs RHE, correlating with a less efficient competition of CO2 with H2O for adsorption on single Cu atoms on the graphitic surfaces, revealed by density functional theory calculations.

Application, structure, salts and complexes of lidocaine: a review. Part V. structure of bis(lidocaine) tetrachloridocuprate(II)

The review focuses on lidocaine (2-(diethylamino)-N-(2,6-dimethylphenyl)acetamide): in the first part, its use in various branches of medicine, as well as the structure of lidocaine, its salts and molecular complexes was discussed; in the second part the use of lidocaine in the composition of deep-eutectic solvents (DES), DES-microemulsions and complexes of lidocaine with zinc, copper, cobalt, platinum and iron was considered; in the 3rd the structure of bis(lidocaine) tetrachlorido-zincate(II) was considered, in the 4th part the structure of bis(lidocaine) tetrachloridoferrate(III) chloride was discussed, this part reports on the synthesis and structure of bis(lidocaine) tetra-chloridocuprate(II), (LidH)2[CuCl4], which crystallizes in the monoclinic space group P21/c with a = 15.7831(2), b = 24.2992(2), c = 17.8748(2) Å, β = 104.874(1)°, V = 6625.58(13) Å3, Z = 8, and Dc = 1.355 Mg/m3. The coordination of the Cu2+ ions with chlorine atoms generates two differently distorted tetrahedral anions [CuCl4]2–, while four protonated cations LidH+ remain in an outer coordination sphere. Anions and cations are associated by hydrogen bonds of the N–H···Cl type to form the 2{(LidH)2[CuCl4]} dimer, in which the distance between two copper atoms is 8.95 Å (c/2). With the help of hydrogen bonds of the type N–H···O and N–H·Cl, each dimer is connected with four neighboring dimers, resulting in a three-dimensional structure in which dimers lie at an angle of 28.39° to the a crystallographic axis in the ab planes located at a distance of 10.67 Å from each other.

The mechanism of recrystallization of binary aluminum and tin bronzes

A nanostructural mechanism for recrystallization of binary aluminum and tin bronzes has been developed. First, structure-forming nanocrystals of α-phases, β-phases and γ-phases are formed from elementary nanocrystals of copper, aluminum, tin and their free atoms. The crystallization centers of microcrystals of phases are formed from them. From these centers, structure-forming nanocrystals of phases, free atoms of copper, aluminum, tin, microcrystals of α-phases, β-phases and γ-phases of binary aluminum and tin bronzes are formed.

A comparative DFT study of CO and NO capture by copper- and titanium-functionalized SiC and GeC monolayers

In this work, the interactions of NO and CO molecules with silicon carbide (SiC) and germanium carbide (GeC) graphene-like nanosheets, functionalized with titanium and copper atoms, are comparatively studied through density-functional calculations. The results indicate that NO and CO molecules are only slightly adsorbed on the pristine carbide nanosheets. Also, the copper and titanium adatoms are chemisorbed on the monolayers, leading to stable functionalized carbide nanosheets. These adatoms greatly enhance the binding energies of CO and NO. In particular, the titanium-functionalized GeC monolayers display the highest adsorption energies for CO and NO and also the largest changes in their work functions upon molecule adsorption, indicating that they could be useful for trapping or detecting these molecules.