Order Of Cu Research Articles

Anomalous Hall effect in the noncollinear antiferromagnetic antiperovskite Mn3Ni1−xCuxN

We report the anomalous Hall effect (AHE) in antiperovskite Mn$_{3}$NiN with substantial doping of Cu on the Ni site (i.e. Mn$_{3}$Ni$_{1-x}$Cu$_{x}$N), which stabilizes a noncollinear antiferromagnetic (AFM) order compatible with the AHE. Observed on both sintered polycrystalline pieces and single crystalline films, the AHE does not scale with the net magnetization, contrary to the conventional ferromagnetic case. The existence of the AHE is explained through symmetry analysis based on the $\Gamma_{\rm 4g}$ AFM order in Cu doped Mn$_{3}$NiN. DFT calculations of the intrinsic contribution to the AHE reveal the non-vanishing Berry curvature in momentum space due to the noncollinear magnetic order. Combined with other attractive properties, antiperovskite Mn$_{3}$AN system offers great potential in AFM spintronics.

Environmental assessment and historic erosion calculation of abandoned mine tailings from a semi-arid zone of northwestern Mexico: insights from geochemistry and unmanned aerial vehicles.

Mining is known as one of the primary economic activities where exploitation of minerals and other materials have become essential for human development. However, this activity may represent a risk to the environment, starting from deforestation and ending with production of residues that might contain potentially toxic elements. Tailing deposits from historical mining are an example of waste that may represent an environmental concern when abandoned and exposed to environmental conditions. The town of Nacozari de Garcia, in northwestern Mexico, has three abandoned mine tailings (locally known as tailings I, II, and III) located around the urban area that represent important sources of dust and pollution. Images obtained using unmanned aerial vehicles (UAV) in conjunction with geochemical data are used to assess historic erosion calculation and pollution considering contamination and hazard indexes in tailings II and III. Digital elevation models of abandoned tailings were obtained using photogrammetry with UAV. A total of 37 surficial samples were collected from mine tailings to determine elemental concentrations (As, Cu, Pb, W, Zn) using portable X-ray fluorescence. Higher concentrations were found on samples from mine tailing II. Average concentrations followed the decreasing order of Cu > Zn > W > Pb > As for tailing II, whereas decreasing order of Cu > Zn > W > As > Pb was found for tailing III. Contamination Index (CI) values obtained from tailings II and III represent a low potential of pollution, whereas efflorescent crusts from these tailings represent a high potential of polluting soils and sediments by dust generation. Hazard Average Quotient (HAQ) values on both tailings suggest a very high potential of contamination if fluids infiltrate tailings and interact with surficial water and/or groundwater. Obtained surfaces of mine tailings II and III are 146,216 and 216,689m2, respectively, which represent around 11% of the urbanized area. A loss mass of 321,675 tons was determined for mine tailing II, whereas 634,062tons for tailing III, accounting for 0.96 milliontons of total eroded mass. Since abandonment, calculated erosion rates of 493tha-1year-1 (tailing II) and 232tha-1year-1 (tailing III) are in agreement with those determined in other mining areas. CI and HAQ indexes provide good estimates of pollution associated with abandoned mine tailings from Nacozari de García. Historic erosion determined in these tailings is an environmental concern since eroded material and polluted water have been incorporated into the Moctezuma River, which feeds several villages, whose major activities include agriculture and livestock raising.

Recycling of incinerated sewage sludge ash as an adsorbent for heavy metals removal from aqueous solutions

The management of large quantities of incinerated sewage sludge ash (ISSA) is problematic. Environmental and economic benefits can be achieved by using ISSA as an adsorbent for heavy metals removal due to its exceptionally porous structure and active components. In this study, the feasibility of using ISSA to treat heavy metals (Cd(II), Cu(II) and Zn(II)) contaminated waters from both single- and binary-metal systems were investigated. The results showed that the pH of the solution played a pivotal role in the adsorption of heavy metals by ISSA and the optimal pH for the adsorption of these metals was around 6.00. The adsorption process of Cu(II), Cd(II), and Zn(II) in a single-metal system was similar and fast. The equilibrium data followed the Freundlich isotherm model and the corresponding adsorption capacity was 0.13, 0.11 and 0.06 mmol/g, respectively. However, the presence of other competitive metal ions had adverse effects on both the adsorption rate and the adsorption capacity for the target metal ions. The affinity of ISSA towards the metals followed the order of Cu(II) > Cd(II) > Zn(II). The difference in pH value and Ca or Na concentration of the solution after adsorption revealed that cation exchange played a fundamental role in the adsorption of the target metals, while electrostatic attraction and precipitation were insignificant. Over all, the application of ISSA as an adsorbent would be a promising option to both relieve the waste disposal pressure and mitigate the complex heavy metals pollution.

EXAFS Study of the Local Order in Cu2ZnSn(SxSe1–x)4 Alloys

Local structure in Cu2ZnSn(SxSe1–x)4 alloys is studied by the extended X‐ray absorption fine structure (EXAFS) method. K edge absorption spectra of four elements: Cu, Zn, Sn, and Se have been measured. The EXAFS analysis of the nearest neighbor shell is performed using simultaneous fitting of the data for all four K edges. This provides value of structural parameters in the most consistent way. The cation–anion interatomic distances exhibit the bimodal behavior, i.e., the Me–S and Me–Se distances (Me = Cu, Zn, and Sn) are practically constant over the whole composition range of Cu2ZnSn(SxSe1–x)4 alloys. They are compared to the X‐ray diffraction (XRD) values for these alloys. The analysis of the EXAFS Debye‐Waller factors indicates differences in the static disorder around different cations with the lowest disorder observed in the first coordination shell of Sn atoms.

Studies on the interaction of antibiotic drug rifampin with DNA and influence of bivalent metal ions on binding affinity.

In this paper, the interaction between rifampin, a known antibiotic used against tuberculosis, and DNA helix is investigated by applying multiple biophysical and molecular modelling approaches in an aqueous solution at pH 7.4 and 5. It was proved that the fluorescence quenching of labeled probe DNA by rifampin is a result of the complex formation of rifampin in groove of DNA. Binding parameters were calculated using the logarithmic Hill equation to provide a quantitative term of the binding affinity between rifampin and DNA sites. The resulting ΔH0 = -122.76 ± 0.07 kJ/mol and ΔS0 = -308.19 ± 238.78 J/mol K confirms the role of the Van der Waals' forces and hydrogen bonding in the rifampin-DNA complexation. Furthermore, the influence of bivalent metal ions on the binding affinity was resulted in order of Cu(II) > Ca(II) > Co(II) > Zn(II).

Influence of Body Weight and Gender on the Accumulation of Heavy Metals in Ligia cinerascens Based on Field Investigation and Cd Exposure Experiment.

Isopods of the genus Ligia are deemed as excellent pollution monitoring organisms for coastal zones. A species of Ligia cinerascens was chosen to be tested, which was collected from three coastal zones in Dalian, China. The concentrations of metals followed the order of Cu>As ≈ Cd>Pb. Ligia collected from a municipal sewage outlet in Heishijiao showed the highest level of metals. Ligia from a natural bathing beach in Changshan Island showed the lowest level of metals as expected. Ligia grown in the same site could accumulate different levels of metals due to their different body weight. Both males and females conformably accumulated heavy metals in bodies. Taken together, this work suggests that L. cinerascens can serve as a biomonitor species. Within the range of 0.3-0.9g body weights, body weight rather than gender should be taken into account as a factor in the process of environmental biomonitoring.

Concentration Levels, Biological Enrichment Capacities and Potential Health Risk Assessment of Trace Elements in Eichhornia crassipes from Honghu Lake, China

This study investigated the concentrations of Zn, Cu, Cr, Pb, As and Cd in different tissues of E. crassipes from Honghu Lake. The total concentrations of trace elements in E. crassipes were observed in descending order: Zn (111.6162) > Cu (15.7494) > Cr (7.0466) > Pb (5.6251) > As (3.6831) > Cd (0.1941) mg/kg. The order of the bioconcentration factor (BCF) measured in E. crassipes was Zn > As > Cr > Cu > Pb > Cd > 1, indicating that E. crassipes possessed a strong biological enrichment ability to accumulate a variety of trace elements. The translocation factor (TF) values decreased in the order of Cu > Zn > Cr > As > Pb > Cd, all of which were lower than 1, which showed that the absorption of the trace elements by E. crassipes was mainly accomplished in the roots. Moreover, the health risk assessments showed that the carcinogenic and noncarcinogenic risks of the edible parts of E. crassipes were 26.1 and 4.6 times higher than the maximum acceptable value recommended by the USEPA for adults and children of approximately 39.2- and 6.9-fold, respectively. Children were more sensitive than adults. The main trace elements that led to noncarcinogenic risks were As, Cr and Cu, while Cr and As led to carcinogenic risks. The results of the Pearson correlation showed positive correlations with the concentrations of Zn, Cr and As between E. crassipes and the water as well as negative correlations of the contents of all six trace elements between E. crassipes and the sediment.

Electrocatalytic property of water oxidation reaction depends on charging state of intermediates on Ag-M (M = Fe, co, Ni, Cu) in alkaline media

DFT calculations are performed to investigate the water oxidation reaction intermediates on Ag2M (M = Fe, Co, Ni, Cu), and Pt3 clusters in alkaline media both in the gas and solution (water) phases in the neutral and charged states. The calculated results revealed that the neutral and anionic clusters were found to be more suitable catalysts than cationic clusters because of weakly bonded water oxidation reaction intermediates. In addition, the calculated structural parameters of the water oxidation intermediates with Ag2M (M = Fe, Co, Ni, Cu) clusters revealed that M-OH bond strengths are found to be in the order of Cu < Ni < Co < Fe. Conclusively, Ag2Cu cluster was determined to be the best electrocatalyst regarding oxygen evolution reaction via 4e transfer, which is consistent with results on larger Ag2M clusters (13 atoms) and periodic Ag-M nanoalloys due to weaker binding energies of the water oxidation intermediates.

The combination of novel airlift magnetic separation loop system and an efficient biosorbent for the removal of Pb(II) from aqueous solution.

An efficient biosorbent containing magnetic nanoparticles, walnut shell powder, foam, and alginate (AMWSF) was prepared and used in Pb(II) removal. The adsorption process was performed in an airlift magnetic separation loop system. Optimum adsorption conditions were tested at pH 3-7, biomass dose of 0.03-0.4 g, temperature of 15-35 °C, initial Pb(II) ion concentration of 50-400 mg·L-1, and contact time of 10-480 min. The equilibrium adsorption capacity reached up to 69.45 mg·g-1. The physicochemical properties of AMWSF were analyzed by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. The experimental data were in agreement with the pseudo-second-order kinetic and Langmuir isotherm models. The influences of Cu(II), Cd(II), and Zn(II) on Pb(II) adsorption showed antagonistic effect strength in the order of Cu(II) > Cd(II) > Zn(II). AMWSF was reused seven times and separated rapidly by magnetic field. The results demonstrated the potential of AMWSF in practical applications involving Pb(II).

A luminescence study of Cu2ZnSnSe4/Mo/glass films and solar cells with near stoichiometric copper content

Cu2ZnSnSe4 (CZTSe) is one of the leading candidates for the absorber layer in sustainable solar cells. Thin films of CZTSe with a near stoichiometric [Cu]/[Zn + Sn] were used to produce solar cells with conversion efficiency η = 6.4% by a standard solar cell processing including KCN etching and the deposition of CdS and ZnO. Both CZTSe films and solar cells were examined using photoluminescence (PL) to analyse the nature of radiative recombination and photoluminescence excitation (PLE) at 4.2 K to determine the bandgap (Eg). Low temperature PL spectra of the films reveal an intense band P1 at 0.81 eV and a low intensity band P2 at 0.93 eV. Their temperature and excitation intensity dependencies suggest that they both involve recombinations of free electrons with holes localised at acceptors with the energy level influenced by potential fluctuations in the valence band. We associate P1 and P2 with different fractions of CZTSe: with a lower and higher degree of order of Cu and Zn on the cation sub-lattice, respectively. Device processing reduced the intensity of P1 by 2.5 whereas the intensity of P2 increased by a 1.5. We assign this to a low temperature annealing due to CdS and ZnO deposition which increased the fraction of CZTSe with high degree of Cu/Zn order and decreased the fraction with low degree of Cu/Zn order. Device processing increased Eg, blue shifted P1, decreased its width, j-shift and the mean depth of potential fluctuations. These can also be related to the annealing and/or KCN etching and the chemical effect of Cd, due to CdS replacing copper at the CdS-CZTSe interface layer. Processing induced a new broad band P3 at 1.3 eV (quenching with Ea = 200 meV) which we attributed to defects in the CdS layer.

Heavy metal bioavailability and accumulation in winter wheat (Triticum aestivum L.) irrigated with treated wastewater in calcareous soils

Irrigation with raw or diluted wastewater increases in many developing countries, but the increasing availability and use of wastewater generates challenges for public agencies charged with minimizing potential impacts on public health and the environment. In this study, the available (DTPA-extractable) concentration of Zn, Cu, Cd, Pb, and Ni in the surface soil was measured in five sites irrigated with treated wastewater as compared with a site irrigated with freshwater (control). The major sources of wastewater were municipal wastewater, household, commercial, and industrial effluents, which were treated to settle and remove solids prior its use for irrigation. In addition, the concentration of the above five heavy metals and their accumulation and mobilization characteristics were determined in the roots, shoots, and grains of winter wheat (Triticum aestivum L.) grown in treated wastewater-irrigated soils. Irrigation with treated wastewater resulted in a remarkable build-up of metal concentrations in the soil (averaged over five sites) in the order of Cd (178.2%) > Ni (105.1%) > Cu (66.4%) > Zn (66.0%) > Pb (40.9%) compared with control. However, only Cd concentration exceeded the permissible range. The concentration of heavy metals was significantly greater (P < 0.05) in wheat roots than in shoots and grains (root ≫ shoot > grain). The highest concentrations were found in the roots in the order of Cu > Zn > Pb > Cd > Ni. The maximum concentrations of Zn, Cu, Ni, Cd, and Pb in wheat grains were 3.20, 1.20, 0.52, 0.31, and 0.21 mg kg−1, respectively. The bioconcentration and translocation factors of wheat showed that heavy metals quantitatively accumulated in the roots and were poorly translocated to the grains. The potential health risks, calculated as hazard quotients (HQ), were less than unity for most heavy metals, indicating that local people are within the safe limit regarding non-carcinogenic risks. However, the HQ value of Cd exceeded 1 for both children and adults, indicating a high health hazard for the whole exposed population by this metal.

Magnetic structure and field-dependent magnetic phase diagram of Ni2In-type PrCuSi

The magnetic structure of the ternary equiatomic intermetallic compound PrCuSi is investigated using neutron powder diffraction experiments in 0 T as well as in external magnetic fields up to 2 T. The PrCuSi compound crystallizes in the hexagonal Ni2In-type structure, in the space group P63/mmc. In this structure, cationic ordering of Cu and Si takes place. The antiferromagnetic phase transition in the Pr sublattice takes place at K in 0 T. Under an external magnetic field of 2 T, a field-induced ferromagnetic phase is observed. Magnetoelastic coupling is evidenced by an increase in the unit cell volume. Clear signatures of a mixed antiferromagnetic and ferromagnetic phase in weak, intermediate fields, 0.4–0.8 T, are obtained from the present study. Using the present set of experimental data, we construct the H − T phase diagram of PrCuSi.

Atomic Ordering of Two Neighboring Transition Metals-Cu and Zn from Binary CuZn to Ternary Cu3ZnSb.

A new ternary compound Cu3ZnSb was synthesized by high temperature solid state synthesis and characterized by single crystal X-ray diffraction and energy dispersive X-ray analysis. The ternary Cu3ZnSb crystallizes in the tetragonal crystal system with the space group P4/ nmm (129), and its unit cell contains 10 atoms which are distributed over 4 independent crystallographic positions. The structure is built up with [Cu3Sb] slabs that correspond to the unit cells of Cu2Sb and planar 44 nets of Zn atoms. The planar nets of Zn atoms are interspersed between two adjacent [Cu3Sb] slabs. The structure can be viewed as alternating units of Cu2Sb and CsCl type β'-brass (CuZn) structures in the [001]. An unusual atomic ordering of two neighboring transition metals Cu and Zn is observed and is confirmed by first principle calculations. The atomic ordering of Cu and Zn is retained from binary β'-brass structure (CuZn) to ternary Cu3ZnSb. Total energy calculations confirmed the experimental model of Cu/Zn ordering to be the most stable in the structure of Cu3ZnSb. The calculated density of states (DOS) and crystal orbital Hamiltonian population (COHP) explain the stability and bonding characteristics in the structure of Cu3ZnSb. The implication of the persistent Cu/Zn ordering in ternary phases for materials design is emphasized.

Catalytic graphitization of kraft lignin to graphene-based structures with four different transitional metals

Catalytic graphitization of kraft lignin to nano-materials was investigated over four transitional metal catalysts (Ni, Cu, Fe, and Mo) through a thermal treatment process under an argon flow at 1000 °C. The catalytic thermal process was examined using thermal gravimetric analysis (TGA) and temperature-programmed decomposition (TPD) experiments. The crystal structure and morphology of the thermal-treated metal-lignin samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. Catalytic graphitization of kraft lignin to nano-materials was investigated over four transitional metal catalysts (Ni, Cu, Fe, and Mo) through a catalytic thermal treatment process. It was observed that multi-layer graphene-encapsulated metal nanoparticles were the main products, beside along with some graphene sheets/flakes. The particle sizes and graphene shell layers were significantly affected by the promoted metals. BET surface areas of samples obtained from different metal precursors were in the range of 88–115 m2/g within the order of Ni- > Fe- > Mo- > Cu-. Thermal gravimetric analysis (TGA) and temperature-programmed decomposition (TPD) experimental results showed that adding transitional metals could promote the decomposition and carbonization of kraft lignin. The catalytic activity increased with an order of Mo≅Cu < Ni≅Fe. XRD results show that face-centered cubic (fcc) Cu crystals is formed in the thermal-treated Cu-lignin sample, fcc nickel phase for the Ni-lignin sample, β-Mo2C hexagonal phase for the Mo-lignin sample and α-Fe, γ-iron, and cementite(Fe3C) for the Fe-lignin sample. Average particle sizes of these crystal phases calculated using the Scherrer formula are 52.4 nm, 56.2 nm, 21.0 nm, 23.3 nm, 11.3 nm, and 32.8 nm for Ni, Cu, β-Mo2C, α-Fe, γ-iron, and Fe3C, respectively. Raman results prove that the graphitization activity of these four metals is in the order of Cu < Mo < Ni < Fe. Metal properties such as catalytic activity, carbon solubility, and tendency of metal carbide formation were related to the graphene-based structure formation during catalytic graphitization of kraft lignin process.

Integration of chemical and toxicological tools to assess the bioavailability of copper derived from different copper-based fungicides in soil

Because the extensive use of Cu-based fungicides, the accumulation of Cu in agricultural soil has been widely reported. However, little information is known about the bioavailability of Cu deriving from different fungicides in soil. This paper investigated both the distribution behaviors of Cu from two commonly used fungicides (Bordeaux mixture and copper oxychloride) during the aging process and the toxicological effects of Cu on earthworms. Copper nitrate was selected as a comparison during the aging process. The distribution process of exogenous Cu into different soil fractions involved an initial rapid retention (the first 8 weeks) and a following slow continuous retention. Moreover, Cu mainly moved from exchangeable and carbonate fractions to Fe-Mn oxides-combined fraction during the aging process. The Elovich model fit well with the available Cu aging process, and the transformation rate was in the order of Cu(NO3)2 > Bordeaux mixture > copper oxychloride. On the other hand, the biological responses of earthworms showed that catalase activities and malondialdehyde contents of the copper oxychloride treated earthworms were significantly higher than those of Bordeaux mixture treated earthworms. Also, body Cu loads of earthworms from different Cu compounds spiked soils were in the following order: copper oxychloride > Bordeaux mixture. Thus, the bioavailability of Cu from copper oxychloride in soil was significantly higher than that of Bordeaux mixture, and different Cu compounds should be taken into consideration when studying the bioavailability of Cu-based fungicides in the soil.

Low-Temperature Reactions of HCl with Metal-Doped Carbon

A model carbon prepared from phenolic resin was activated with O2 and then impregnated with Ca, Cu, or Zn to examine the relationship between the amount of HCl desorbed from carbon samples containing various metals in this lower temperature range (100 and 300 °C) and clarified the effect of active sites on HCl adsorption. The results showed that interactions between HCl and carbon were enhanced at temperatures in the range of 100–300 °C and that the amount of HCl reacted was increased by doping with these metals. The different HCl concentration profiles at 100 and 300 °C were obtained with a greater overall decrease in HCl at the lower temperature (100 °C). Those are attributed to increased physical adsorption of HCl at 100 °C. The mass of HCl reacted increased in the order of Cu < Ca < Zn at 300 °C and Ca < Cu < Zn at 100 °C, and HCl reacted at 300 °C was evidently more stable than that reacted at 100 °C. Organochlorine compounds, chemisorbed HCl, and inorganic chlorides were all identified on the carbon...

Heavy metal and δ13C value variations and characterization of dissolved organic matter (DOM) during vermicomposting of pig manure amended with 13C-labeled rice straw.

In this work, a mixture of pig manure and 13C-labeled rice straw was vermicomposted with Eisenia fetida for 40days. The results showed that after they acclimated to the vermicomposting environment, the earthworms helped to degrade the substrate residues. After 40days, the vermicomposting led to much higher pH, EC, C/N, available K, available P, available Zn, and CEC values but much lower available N and available Cu values in the substrate residues compared to the initial values. The earthworms accumulated 13C, Cu, and Zn with a heavy metal enrichment capacity in the order of Cu > Zn. Furthermore, the correlation analysis showed that the Cu and Zn content in the DOM was mainly controlled by the Cu and Zn content in the pig manure. The earthworms accumulated Cu and Zn by feeding on the substrate residues, but the DOM from the 13C-labeled rice straw helped to extract Zn from the substrate residues and promoted the migration of Zn into the earthworm tissues and/or DOM. Moreover, the characterization of the DOM extracted from the substrate residues revealed a decrease in the content of the aliphatic alcohols or polysaccharide-like substances and an increase in the aromatic compounds and fulvic or humic acid-like substances in the DOM as the vermicomposting time increased. This indicated that the higher humification degree in the DOM caused by vermicomposting contributed to the increased mobility of Zn in the substrate residues and helped Zn migrate into the earthworms or DOM.

Perforation conditions and almost algebraic order in Cuntz semigroups

For a C*-algebra A, determining the Cuntz semigroup Cu(A ⊗) in terms of Cu(A) is an important problem, which we approach from the point of view of semigroup tensor products in the category of abstract Cuntz semigroups by analysing the passage of significant properties from Cu(A) to Cu(A)⊗Cu Cu(). We describe the effect of the natural map Cu(A) → Cu(A)⊗Cu Cu() in the order of Cu(A), and show that if A has real rank 0 and no elementary subquotients, Cu(A)⊗Cu Cu() enjoys the corresponding property of having a dense set of (equivalence classes of) projections. In the simple, non-elementary, real rank 0 and stable rank 1 situation, our investigations lead us to identify almost unperforation for projections with the fact that tensoring with is inert at the level of the Cuntz semigroup.

Dynamic adsorption of mixtures of Rhodamine B, Pb (II), Cu (II) and Zn(II) ions on composites chitosan-silica-polyethylene glycol membrane

The adsorption of a solution mixture of Rhodamine B, Pb (II), Cu (II) and Zn(II) was studied using dynamic methods employing chitosan-silica-polyethylene glycol (Ch/Si/P) composite membrane as an adsorptive membrane. The composite Ch/Si/P membrane was prepared by mixing a chitosan-based membrane with silica isolated from rice husk ash (ASP) and polyethylene glycol (PEG) as a plasticizer. The resultant composite membrane was a stronger and more flexible membrane than the original chitosan-based membrane as indicated by the maximum percentage of elongation (20.5 %) and minimum Young’s Modulus (80.5 MPa). The composite membrane also showed increased mechanical and hydrophilic properties compared to the chitosan membranes. The membrane was used as adsorption membrane for Pb (II), Cu (II), Cd (II) ions and Rhodamine B dyes in a dynamic system where the permeation and selectivity were determined. The permeation of the components was observed to be in the following order: Rhodamine B > Cd (II) > Pb (II) > Cu (II) whereas the selectivity was shown to decrease the order of Cu (II) > Pb (II) > Cd (II) > Rhodamine B.

Origin of the Thickness-Dependent Oxidation of Ultrathin Cu Films on Au(111)

Ultrathin Cu films deposited on a metal substrate have been used as a model system to understand the structure–function relationship in electrocatalysis, heterogeneous catalysis, and microelectronics. The stability of ultrathin Cu films against oxidation has been of particular interest, but there is a lack of microscopic understanding. We report here an atomic-level study on the thickness-dependent oxidation kinetics of Cu layers on Au(111), from ultrahigh vacuum to near ambient conditions. Ultrathin Cu films on Au(111) were found to exhibit a superior oxidation resistance over Cu(111), and their oxidation resistances increase in the order of Cu(111) < 2.4 ML Cu < 0.4 ML Cu. For 0.4 ML Cu, the spontaneous subsurface diffusion of Cu at 300 K and the formation of a Au-rich surface alloy inhibit the formation of copper oxides at the O2 pressure below 10–4 mbar. However, at near ambient conditions, 0.4 ML Cu would be partially oxidized to the CuO phase directly. In contrast, multilayer Cu or bulk Cu(111), tho...