Search

Multicomponent supramolecular self-assembled systems can potentially harness the properties of multiple systems simultaneously. However, creating multicomponent supramolecular nanostructures with narrow size distributions is challenging due to the dynamic nature of noncovalent interactions. In this article, we report the coassembly of a tris-Ni-(II)-salphen and a tris-Cu-(II)-salphen complex. Co-assembly of the complexes afforded nanofibers with low dispersity, with the metal complexes homogeneously distributed throughout the nanofibers. The length of the nanofibers could also be tuned by varying the ratio of the metal complexes. Density functional theory (DFT) calculations indicate that the dimerization of the copper-(II) complex is unfavorable, unlike the dimerization of the nickel-(II) complex. Co-assembly with the copper-(II) complex inhibits the self-assembly of the nickel-(II) complex, enabling length control of the bimetallic nanofibers. These results could pave the way for designing multicomponent supramolecular systems with applications in catalysis and magnetic devices. [ABSTRACT FROM AUTHOR]

We studied the shear deformation of a laminar Al-Cu composite with (100) and (110) interfaces with a shear perpendicular to the lamellae in comparison with pure single crystal Al and Cu at strain rates of 109 s−1 and 108 s−1 and different initial pressures in the range from −3 GPa to +50 GPa. The results of molecular dynamics (MD) for the plasticity initiation are generalized by means of an artificial neural network (ANN) trained by MD data for the (100) interface, and a rate sensitivity parameter identified using MD data for different strain rates. The ANN-based approach allows us to extrapolate MD data to much lower strain rates, which are more relevant for typical dynamic loadings. The considered problem is of interest as an example of the application of the developed ANN-based approach to bimetallic systems, whereas previously it was tested only for pure metals; in addition, Al-Cu composites are of practical interest for technology. The interface between metals reduces the shear strength of the composite in comparison with both pure metals. At an initial pressure below 10 GPa, the plasticity begins in the aluminum part of the composite, while at higher pressures, the plasticity of the copper part starts first. At a pressure above 40 GPa, a phase transition in the aluminum part governs the plasticity development. All this leads to a nonmonotonic pressure dependence of the critical shear stress of the Al-Cu composite in the case of (100) and (110) interfaces without misorientation. Misorientation decreases the critical stress of the nucleation of lattice dislocation and makes the pressure dependence of this stress monotonic. Deformation modes, with a defect-free copper part and a strain-accommodating aluminum part are observed in the MD and can be useful for technological applications related to deformable conducting materials. [ABSTRACT FROM AUTHOR]

Bimetallic single–atom catalysts (b–SACs) have recently gained prominence by virtue of the unique catalytic cooperative interactions they can exhibit, intertwining electronic and geometric effects. To date, research efforts have exclusively focused on direct mechanisms such as electron density transfer or sequential reactivity. Herein, the first study on indirect, coordination–induced catalytic synergies in carbon‐supported RuPt SACs is conducted. To this end, a holistic approach is developed, combining i) precision synthesis, ii) advanced characterization, iii) exploration of single–site adsorption properties via the hydrogen evolution reaction, and iv) modeling through density functional theory. Despite the lack of both intermetallic coordination in the first or second shell and charge redistribution effects, the RuPt SACs exhibit a H2 formation rate enhanced up to 15–fold compared with their monometallic counterparts. To unfold the origin of the intermetallic cooperativity, modifications of the structural and catalytic properties induced by the integration of a second metal species are investigated. Thus, Pt atoms are found to selectively occupy the most energeticallyfavorable cavities in the support, prompting Ru atoms to assume a distinct, more active, configuration. This contribution unveils a novel principle of bimetallic cooperativity, demonstrating the key role of integrative experimental and computational analyses in studying b–SACs. [ABSTRACT FROM AUTHOR]

X‐ray absorption spectroscopy (XAS) is an element‐selective technique that provides electronic and structural information of materials and reveals the essential mechanisms of the reactions involved. However, the technique is typically conducted at synchrotrons and usually only probes one element at a time. In this paper, a simultaneous two‐color XAS setup at a laboratory‐scale synchrotron facility is proposed based on inverse Compton scattering (ICS) at the Munich Compact Light Source (MuCLS), which is based on inverse Compton scattering (ICS). The setup utilizes two silicon crystals in a Laue geometry. A proof‐of‐principle experiment is presented where both silver (Ag) and palladium (Pd) K‐edge X‐ray absorption near‐edge structure spectra were simultaneously measured. The simplicity of the setup facilitates its migration to other ICS facilities or maybe to other X‐ray sources (e.g. a bending‐magnet beamline). Such a setup has the potential to study reaction mechanisms and synergistic effects of chemical systems containing multiple elements of interest, such as a bimetallic catalyst system. [ABSTRACT FROM AUTHOR]

We studied the shear deformation of a laminar Al-Cu composite with (100) and (110) interfaces with a shear perpendicular to the lamellae in comparison with pure single crystal Al and Cu at strain rates of 109 s−1 and 108 s−1 and different initial pressures in the range from −3 GPa to +50 GPa. The results of molecular dynamics (MD) for the plasticity initiation are generalized by means of an artificial neural network (ANN) trained by MD data for the (100) interface, and a rate sensitivity parameter identified using MD data for different strain rates. The ANN-based approach allows us to extrapolate MD data to much lower strain rates, which are more relevant for typical dynamic loadings. The considered problem is of interest as an example of the application of the developed ANN-based approach to bimetallic systems, whereas previously it was tested only for pure metals; in addition, Al-Cu composites are of practical interest for technology. The interface between metals reduces the shear strength of the composite in comparison with both pure metals. At an initial pressure below 10 GPa, the plasticity begins in the aluminum part of the composite, while at higher pressures, the plasticity of the copper part starts first. At a pressure above 40 GPa, a phase transition in the aluminum part governs the plasticity development. All this leads to a nonmonotonic pressure dependence of the critical shear stress of the Al-Cu composite in the case of (100) and (110) interfaces without misorientation. Misorientation decreases the critical stress of the nucleation of lattice dislocation and makes the pressure dependence of this stress monotonic. Deformation modes, with a defect-free copper part and a strain-accommodating aluminum part are observed in the MD and can be useful for technological applications related to deformable conducting materials.

A study was made of the thermal interaction in the system [Pt(NH3)4]Cl2–(NH4)10[H2W12O42] (Pt : W = 1 : 2) in an argon atmosphere, which begins at a temperature above 200°C, occurs through a number of successive steps, and ends at 450°C. The intermediate products formed in the solid and gas phases were investigated by thermogravimetric analysis, differential thermal analysis, mass spectrometry, X-ray powder diffraction analysis, X-ray photoelectron spectroscopy, and elemental analysis. The end solid products obtained at 542 and 550°C were platinum-based solid solutions Pt1 – xWx with the unit cell parameters a = 3.9261(6) and 3.9262(3) Å, respectively, and also the tungsten oxide phases: hexagonal h-WO3 and monoclinic m-WO3. A reaction was proposed to describe the interaction of the components in the considered system. The obtained results can form the basis of methods for producing catalysts based on platinum and tungsten for various chemical processes. [ABSTRACT FROM AUTHOR]

The energy profile and electronic structure in the [Cu2O2]2+ core have been studied through the peroxo to bis-μ-oxo isomerization process, using multiconfigurational methods. Different strategies were performed to obtain the absolute energies of the singlet ground state using the accuracy potential of the Difference Dedicated Configuration Interaction (DDCI) method. For each structure, the DDCI energies for the ground states were obtained. The results indicate that the minimum bis-μ-oxo is approximately 8 kcal/mol more stable than the peroxo. The analysis of the electronic structure of the peroxo and bis-μ-oxo forms reveals the existence of different extents of charge transfer between the O2 molecule and the Cu, leading to different oxidation states in the Cu and O2 molecule. [ABSTRACT FROM AUTHOR]

Plasmonic metal structure that can host size-tunable optical properties and tailored catalytic surface active sites elicits peculiar functionalities upon integrating with semiconductors. In the case of metal–semiconductor composites, formation of Schottky barrier height and surface plasmon resonance (SPR) effect stimulated by the metallic dispersion cooperatively separates the charge carriers and alters the optical response to longer wavelength region, respectively, which are of paramount importance in the light-induced redox reactions. From the view point of attaining maximum synergy, bimetallic deposition over the titania support has impelled interest due to the supportive interactions arising from metal–metal and metal–TiO2 heterojunctions. In this review article, bimetallic systems constituting mainly Cu, Ni, Au, Ag, Pd and Pt over the titania surface are discussed under the light of preparative methods, their distribution, electronic interactions between the metals and with the titania support, charge carrier transfer pathways, structural stability and optimized content towards achieving maximum efficiency in various applications such as pollutant degradation, CO2 reduction, H2 evolution reaction (HER) and in the functional group conversion of few organic compounds. The role of each metal in the bimetallic system and the effects arising from structure–morphology features of titania are considered to furnish insightful discussion into this exquisite heterojunction. The bimetallic deposition over the other emerged semiconductors are briefly surmised to attest the versatility of this strategy and its reliability from several prospects are brought to the fore to provide the room for developing efficient bimetallic–semiconductor heterostructures. [ABSTRACT FROM AUTHOR]

Thermal transformations of 3[Pt(NH)]Cl-(NH)CrO (I) and 3[Pt(NH)]Cl-2(NH)CrO (II) mixtures in a solid state have been studied by thermal analysis and mass spectrometry in an inert (Ar) atmosphere and air at temperatures from 40 to 550°C. The chemical and phase compositions of the thermolysis products obtained in argon have been determined: Pt and CrO in mixture I and Pt, a platinum-based PtCr solid solution, and CrO in mixture II. The thermal transformation products of mixtures I and II in air consist of two phases: Pt and CrO. It has been shown that interactions in the mixtures proceed through the formation of a metallic chromium phase. The materials obtained in this study can find application as catalysts for low-temperature fuel cells, as well as for organic synthesis processes. [ABSTRACT FROM AUTHOR]

Redox non-innocent ligands have recently emerged as interesting tools to obtain new reactivity with a wide variety of metals. However, gold has almost been neglected in this respect. Here, we report mechanistic investigations related to a rare example of ligand-based redox chemistry in the coordination sphere of gold. The dinuclear metal-centered mixed-valent AuI-AuIII complex 1, supported by monoanionic diarylamido-diphosphine ligand PNPPr and with three chlorido ligands overall, undergoes a complex series of reactions upon halide abstraction by silver salt or Lewis acids such as gallium trichloride. Formation of the ultimate AuI-AuI complex 2 requires the intermediacy of AuI-AuI dimers 5 and 7 as well as the unique AuIII-AuIII complex 6, both of which are interconverted in a feedback loop. Finally, unprecedented ortho-selective C−H activation of the redox-active PNP ligand results in the carbazolyldiphosphine derivative PN*PPr via ligand-to-metal two-electron transfer. This work demonstrates that the redox-chemistry of gold may be significantly expanded and modified when using a reactive ligand scaffold. [ABSTRACT FROM AUTHOR]

Nanocomposite materials, consisting of two or more phases, at least one of which has a nanoscale dimension, play a distinctive role in materials science because of the multiple possibilities for tailoring their structural properties and, consequently, their functionalities. In addition to the challenges of controlling the size, size distribution, and volume fraction of nanometer phases, thermodynamic stability conditions limit the choice of constituent materials. This study goes beyond this limitation by showing the possibility of achieving nanocomposites from a bimetallic system, which exhibits complete miscibility under equilibrium conditions. A series of nanocomposite samples with different compositions are synthesized by the co-deposition of 2000-atom Ni-clusters and a flux of Cu-atoms using a novel cluster ion beam deposition system. The retention of the metastable nanostructure is ascertained from atom probe tomography (APT), magnetometry, and magnetotransport studies. APT confirms the presence of nanoscale regions with ≈100 at% Ni. Magnetometry and magnetotransport studies reveal superparamagnetic behavior and magnetoresistance stemming from the single-domain ferromagnetic Ni-clusters embedded in the Cu-matrix. Essentially, the magnetic properties of the nanocomposites can be tailored by the precise control of the Ni concentration. The initial results offer a promising direction for future research on nanocomposites consisting of fully miscible elements., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

We have studied the electrochemical deposition of Rh on polycrystalline Ag substrates from electrolytes containing chloride and sulphate anions. Chronoamperometry and cyclic voltammetry have been employed in order to elucidate the growth mechanism. Anions play a key role in the growth mechanism and the resulting structures. In the presence of sulphate anions Rh deposition follows a 3D nucleation—growth mechanism, while a 2D nucleation—growth is obeyed in the case of electrolytes containing chloride anions. Ab initio thermodynamics studies support the hypothesis that chloride anions stabilize the Rh deposition favouring a 2D mechanism at low overpotentials in good agreements with the experimental data. [ABSTRACT FROM AUTHOR]

This paper describes two efficient strategies to suppress β-H elimination during the palladium/copper bimetallic system-mediated cross-coupling between alkynamides and alkenes. Remote donor groups with the terminal olefins, such as toluenesulfonamide, phosphate, sulfone, etc., cooperate with the amide of alkynamides and chelate the palladium active center, to promote C( sp3)O bond formation by suppressing the β-H elimination. Another strategy uses the rigid structure of norbornene to make an intermediate without a syn-β-hydrogen to achieve reductive elimination of the CCl bond. [ABSTRACT FROM AUTHOR]

Trivalent chromium and iron are the products of the traditional reduction of hexavalent chromium by ferrous salts in industrial wastewater. Although there have been a few studies of Cr(III) adsorption, none have considered the effect of Fe(III) on Cr(III) adsorption in a binary system representing expected products of hexavalent chromium in industrial wastewater. The biosorption of Cr(III) and Fe(III) ions onto pretreated ground orange peel in single and binary systems was studied in batch experiments using a variety of techniques. The kinetic results showed a rapid rate of biosorption of Cr(III) and Fe(III) in single and binary systems and mutual interference effects in the competitive binary Cr(III)–Fe(III) system. Second order kinetic models showed the best fit for all systems. The behavior of competitive Cr(III)–Fe(III) biosorption were successfully described by the multicomponent Langmuir model, obtaining maximum capacities for Cr(III) and Fe(III) of 9.43 and 18.19 mg/g respectively. SEM/EDS results confirmed that the metals adsorb on the surface and FTIR identified the hydroxyl groups on the carboxylic acids as the active binding sites. [Copyright &y& Elsevier]

The hydrogenation reaction of carbon dioxide and a mixture of carbon oxides on bimetallic catalytic systems containing nanoparticles of Fe, Ni, Co, and Mn supported on an inert carrier is studied. It is found that the ratio of saturated and unsaturated hydrocarbons in the hydrogenation products and the synergistic effect are determined mainly by the number of hydrogen atoms that are capable of migrating from one active center to another and by composition of those centers. Differences in the catalytic activity and selectivity of the bimetallic samples are explained by different rates of the spillover of weakly bound hydrogen (H) and the different rates of the jumpover of CH radicals from one center to another at which their further hydrogenation takes place. [ABSTRACT FROM AUTHOR]

Modified zero valent iron (MZVI) was used to study the transformation of a chlorothalonil (CLT) solution and the variation of the observed degradation rate of the reduction reactions. This was carried out when transition metals e.g. Pd, Cu and Co plated on the surface of micrometric iron particles (<150μm) were used as reducing catalytic agents for pesticide removal. Reactions were undertaken under both oxic and anoxic conditions in the presence and the absence of a phosphate buffer solution (PBS). Results of batch studies in nitrogen sparged solutions revealed that incomplete slow dechlorination merely occurred with zero valent iron (ZVI), however, complete rapid dechlorination reactions took place with MZVI especially Fe/Pd. Dechlorination was depicted by studying UV absorbance and MS spectra of CLT and all corresponding by-products. Typical blue shifts (Δλ =4–6nm/chlorine atom) were observed at the same time as chlorine cluster isotopes disappeared. After the plating process, metal loading was controlled by analyzing the remaining metal in the solution by atomic absorption spectroscopy. Experiments showed that CLT degradation mechanism is faster in nitrogen sparged solutions in the absence of PBS. Time needed for complete removal of 2.08±0.19μM CLT solution was about 2h when experiments were conducted with ZVI (t 1/2 =15.0min) and about 10min when the reaction was carried out under the same conditions with Fe/Pd 1% (t 1/2 =1.0min). Degradation rates for all bimetallic systems were determined showing that Pd is the more exciting catalytic transition metal followed by Cu and Co. Furthermore, MZVI method showed obvious advantage to traditional CLT treatment methods. [Copyright &y& Elsevier]

Abstract: Recent studies of electronic and structural properties of small doped metal clusters are reviewed. Both theoretical and experimental investigations of size and composition dependent cluster properties have emphasized the importance of the interplay between geometry and electronic structure. The conceptually simple phenomenological shell models, which have been used extensively to describe bare simple metal clusters, are extended towards different types of doped cluster species by choosing appropriate ad hoc potentials. More detailed fundamental understanding is gained by investigating the delocalized molecular orbitals as computed with ab initio density functional theory. [Copyright &y& Elsevier]

This review summarizes recent applications of nickel as a nonprecious metal catalyst in hydrodehalogenation (HDH) reactions of halogenated aromatic compounds (Ar–Xs). Nickel-based HDH catalysts were developed for reductive treatment of both waste containing concentrated Ar–Xs (mainly polychlorinated benzenes) and for wastewater contaminated with Ar–Xs. Ni-catalyzed HDH enables the production of corresponding nonhalogenated aromatic products (Ar–Hs), which are principally further applicable/recyclable and/or Ar–Hs, which are much more biodegradable and can be mineralized during aerobic wastewater treatment. Developed HDH methods enable the utilization of both gaseous hydrogen via the direct HDH process or other chemical reductants as a source of hydrogen utilized in the transfer of the hydrodehalogenation process. This review highlights recent and major developments in Ni-catalyzed hydrodehalogenation topic since 1990. [ABSTRACT FROM AUTHOR]

The reactivity of Co deposited on Cu(111) is determined using the dissociation of CH4 as a test reaction. The CH4 molecules are produced in a supersonic molecular beam expansion and dissociate on Co but not on Cu under the experimental conditions used here. It is found that the dissociation probability of CH4 on a few layers of pseudomorphic Co adsorbed on noble Cu(111) is larger than that of pure Co. The apparent CO binding energy is, however, not shifted as measured using thermal desorption. A model of this surprising behavior is presented using information on the structure and theoretical calculations on the shift of the d-band of Co adsorbed on Cu(111). [ABSTRACT FROM AUTHOR]