Lamellar Copper Research Articles

Lamellar copper molybdate as a novel photocatalyst for the degradation of Rhodamine B

Water containing organic pollutants poses increasingly severe challenges to the clean water resources that humans rely on for survival. Photocatalysis is one of the technologies for removing organic pollutants from wastewater, which is green and has no secondary pollution. Here layered HCu1.5MoO5 photocatalyst is synthesized by wet chemistry. It is assembled from multiple stacked thin nanosheets with a thickness of ∼12.5 nm. The thin-layer structure of two-dimensional photocatalysts considerably reduces the migration distance of photo-generated charge carriers, thereby promoting efficient charge separation. In addition, it exhibits near-ultraviolet light response with the remarkable local surface plasmon resonance (LSPR) effect in the visible light region. The specific surface area and mesoporous structure of HCu1.5MoO5 are particularly advantageous for the mass transfer process of photocatalytic degradation. These characteristics enable it to effectively degrade Rhodamine B, achieving a degradation rate of 78.4 % after 120 min. The work provides a new perspective for the development of layered photocatalysts for photocatalytic degradation.

Genesis of Xinzhai Sandstone-Type Copper Deposit in Northern Laos: Geological and Geochemical Evidences

Xinzhai sandstone-type copper deposit located in northern Laos lies in the Jiangcheng-Phongsaly-Phrae Mesozoic basin (JPMB), which is regarded as southern extension of the Lanping-Simao Mesozoic basin in China. The copper deposit belt is bounded by the Ailaoshan-Heishui River fault and the Dian Bien Phu-Luang Prabang fault at the east and Lancang River-Bannankan faults at the west. Two types of orebodies are identified in the Xinzhai area based on geological investigation. One is lamellar copper orebody hosted by the fine lithic feldspar sandstones and feldspar lithic sandstones; another is vein-type orebody. The sulfur isotopic compositions of the chalcopyrite and tetrahedrite are from -11.6‰ to -1.8‰, indicating that sulfur is derived from bacterial sulfate reduction (BSR). δD values of fluid inclusions in ore-bearing quartz samples are from -99‰ to -78‰. The calculated δ18OH2O values of ore-forming fluid vary from -2.3‰ to 0.4‰ using the quartz-water fractionation equations and the mineralization temperature. Oxygen and hydrogen isotopic compositions show that the ore-forming fluid was derived from basin fluid. Rock-mineral identifications show that both of the mineral grain maturity and the structural maturity are high in the Jurassic Huakaizuo Formation, reflecting a far-source accumulation and lake facies sedimentatary environment. Based on tectonic determination diagram of the Al2O3/SiO2-TFe+MgO, the sandstone samples collected from the Huakaizuo Formation were plotted in the passive continental margin. The collision of the Indian and Eurasian blocks during the Cenozoic formed large-scale strike-slips and thrust nappe structures in margin of the basin. With the tectonic movement, Cu-rich basin fluid from the basement of basin migrated upward along the contemporaneous fault and into the high porosity strata. At the same time, in organic matter-riched condition, bacterial sulfate reduction (BSR) has been triggered, forming a large number of S2- ions, and then precipitation of sulfide started. This mechanism describes the process of copper mineral deposition in the Xinzhai deposit.

In Situ Probing of Stack-Templated Growth of Ultrathin Cu2–xS Nanosheets

Ultrathin two-dimensional (2D) nanomaterials have attracted intense research efforts due to their extraordinary optoelectronic properties. However, the nucleation and growth mechanisms of 2D colloidal nanosheets are still poorly understood. Here, we follow the formation of ultrathin colloidal Cu2–xS nanosheets by in situ small-angle X-ray scattering. While thermal decomposition of copper–dodecanethiolates produces spheroidal Cu2–xS nanocrystals, the addition of chloride to the reaction mixture results in 2 nm thick Cu2–xS nanosheets with well-defined shape and size. Our results show that chloride stabilizes stacks of lamellar copper–thiolate supramolecular complexes, so that they remain intact beyond the onset of Cu2–xS nucleation at 230 °C, leading to 2D-constrained stack-templated nucleation and growth. The face-to-face stacking of the nanosheets reinforces the 2D constraints imposed by the lamellar soft template, since it prevents internanosheet mass transport and nanosheet coalescence, thereby inhibit...

Particle generation by cosolvent spray pyrolysis: Effects of ethanol and ethylene glycol

Abstract

Nanoscale Twinned Copper Nanowire Formation by Direct Electrodeposition

Lamellar copper nanowires with a high density of traverse twins (twin spacing even less than one nm) are synthesized (see image). These wires spontaneously grow from a pure electrolyte of CuSO4 by electrodeposition. Micromechanical testing and electrical four-probe measurements impressively demonstrate that the highly twinned nanowires show a remarkably high mechanical strength while at the same time maintaining a high electrical conductivity.

Characterization of Chain Molecular Assemblies in Long-Chain, Lamellar Copper Alkylsulfonates: Self-Assembled Monolayer vs Bilayer Structure

Direct characterization of chain molecular structures in a series of layered organic/inorganic long-chain alkylsulfonates, Cu(C n H 2n+1 SO 3 ) 2 ·yH 2 O (CuSO 3 -n, where n=10, 12 and y = 4 for group I; n = 14, 16, 18 and y = 2 for group II), using combined application of Fourier transform infrared (FTIR) spectroscopy and powder X-ray diffraction (XRD) is reported. These compounds show a layered structure, as determined by XRD, consisting of alternating organic alkylsulfonate layers and inorganic copper(Il) hydrate layers, with interlayer distances of up to 3.82 nm. It is worth noting that the layer-to-layer distance can be easily and rationally metered by choosing alkylsulfonates of different lengths: Shorter alkylsulfonates, group I, yield an interdigitated monolayer structure with shorter periodicity, whereas longer alkylsulfonates, group II, yield a noninterdigitated bilayer structure with longer periodicity. The goal was to correlate the structural changes by increasing the chain length, monitored by XRD, with the alkyl chain structure detected by FTIR spectroscopy. From the FTIR spectra, the distinguishable features between the two groups appear in two different wavenumber regions, i.e., the hydrogen-bonding region (2900-3500 cm -1 ) and the sulfonate-stretching region (1000-1250 cm -1 ), indicating that the hydrophilic layers of the two groups are completely different. Furthermore, a detailed investigation of the C-H modes, including the stretching, scissoring, and rocking modes, reveals that the chain-packing modes of the two groups are different, even though the alkyl chains in the CuSO 3 -n series are all in an all-trans conformational state. The change in the monolayer to bilayer packing with the alkyl chain length, arising from the intermolecular interaction between the alkyl chains, is explained by the rearrangement of the alkyl chains from orthorhombic to hexagonal subcells with decreasing packing density.

Diaza Crown Ethers and Cryptants as Bridging Ligands in Lamellar Copper(I) Coordination Polymers

AbstractCuX‐based coordination polymers (X = I, CN, SCN) with diazacrown ethers or cryptands as bridging ligands have been prepared by reaction of CuX with appropriate macrocycle in acetonnitrile/hexane solution at 100 °C. Whereas [CuI (1, 7‐DA12C4)] (1) and [CuI(1, 10‐DA18C6)] (2) (1, 7‐DA12C4 = 1, 7‐diaza‐12‐crown‐4, 1, 10‐DA18C6 = 1, 10‐diaza‐18‐crown‐6) are both monomeric, [(CuI)2(1, 10‐DA18C6)] (3) contains infinite chains in which (CuI)2 rings are linked in a μ‐N1, N10 manner by thiacrown ether moieties. The distorted tetrahedral coordination of the CuI atoms in 3 is completed by a weak Cu…O interaction (2.393(7)Å) to a 1, 10‐DA18C6 oxygen atom. [(Cu4I4)(1, 10‐DAcrypt)2] (4), (1, 10DAcrypt = 1, 10‐diaza‐cryptand [2.2.2]), [{(CuCN)6(1, 7‐DA12C4)4]·2CH3CN (5) and [(CuSCN)2 (1, 10‐DA18C6] (6) all exhibit lamellar networks with respectively Cu4I4 cubes, (CuCN)6 hexagons and [(CuSCN)2] double chains as their CuX substructures. 4 can imbibe up to 0.64 mol KNO3/mol cryptand and 6 up to 0.35 mol KNO3/mol 1, 10‐DA18C6 as a guest lattice. Crystal structures are reported for 1‐6, thermal analysis data (TG/DTA) for complexes 2, 3 and 5.

Lamellar Copper(I) Thiocyanate-Based Coordination Polymers containing the Alkali Cation ligating Thiacrown Ether 1,10-Dithia-18-crown-6

The lamellar coordination polymer [(CuSCN)2(μ-1,10DT18C6)] (1,10DT18C6 = 1,10-dithia-18-crown-6), in which staircase-like CuSCN double chains are bridged by thiacrown ether ligands, may be prepared in two triclinic modifications 1 a and 1 b by reaction of CuSCN with 1,10DT18C6 in respectively benzonitrile or water. Performing the reaction in acetonitrile in the presence of an equimolar quantity of KSCN leads, in contrast, to formation of the K+ ligating 2-dimensional thiocyanatocuprate(I) net [{Cu2(SCN)3}–] of 2, half of whose Cu(I) atoms are connected by 1,10DT18C6 macrocycles. The potassium cations in [{K(CH3CN)}{Cu2(SCN)3(μ-1,10DT18C6)}] (2) are coordinated by all six potential donor atoms of a single thiacrown ether in addition to a thiocyanate S and an acetonitrile N atom. Under similar conditions, reaction of CuI, NaSCN and 1,10DT18C6 affords [{Na(CH3CN)2}{Cu4I4(SCN)(μ-1,10DT18C6)}] (3), which contains distorted Cu4I4 cubes as characteristic molecular building units. These are bridged by thiocyanate and thiacrown ether ligands into corrugated Na+ ligating sheets. In the presence of divalent Ba2+ cations, charge compensation requirements lead to formation of discrete [Cu(SCN)3(1,10DT18C6-κS)]2– anions in [Ba{Cu(SCN)3(1,10DT18C6-κS)}] (4). Schichtartige CuSCN-haltige Koordinationspolymere mit dem Alkalikationen koordinierenden Thiakronenether 1,10-Dithia-18-Krone-6 Das schichtartige Koordinationspolymer [(CuSCN)2(μ-1,10DT18C6)] (1,10DT18C6 = 1,10-Ditha-18Krone-6) enthalt treppenartige CuSCN-Doppelketten, die durch 1,10DT18C6-Liganden verbruckt sind. Zwei trikline Modifikationen 1 a und 1 b lassen sich durch die Umsetzung von CuSCN und 1,10DT18C6 in Benzonitril bzw. Wasser darstellen. Im Beisein einer aquimolaren Menge von KSCN fuhrt die Reaktion in Acetonitril dagegen zur Bildung des zweidimensionalen Thiocyanatocuprat (I)-Netzes [{Cu2(SCN)3}–] von 2. Die Halfte der hierin beteiligten Cu(I)-Atome werden durch 1,10DT18C6-Makrozyklen verbunden, die die K+-Gegenionen koordinieren. Diese werden in [{K(CH3CN)}Cu2(SCN)3(μ-1,10DT18C6)}] (2) von allen 6 potentiellen Donoratomen eines Thiakronenethers sowie von einem Thiocyanat-S- und einem Acetonitril-N-Atom umgeben. Unter analogen Bedingungen liefert die Umsetzung zwischen CuI, NaSCN und 1,10DT18C6 das Polymer [{Na(CH3CN)2}{Cu4I4(SCN)(μ-1,10DT18C6)}] (3), das verzerrte Cu4I4-Wurfel als charakteristische molekulare Baueinheiten enthalt. Diese werden durch Thiocyanat- sowie Thiakronenether-Liganden zu wellenartigen anionischen Schichten verbunden, die Na+-Kationen koordinieren. Im Beisein von Ba2+-Kationen bedingt der notwendige Ladungsausgleich die Bildung von diskreten Anionen [Cu2(SCN)3(1,10DT18C6-κS)]2– in [Ba{Cu(SCN)3(1,10DT18C6κS)}] (4).

Midinfrared optical excitations in undoped lamellar copper oxides

The weakly electric-dipole-allowed midinfrared excitations are studied in insulating single crystals of ${\mathrm{La}}_{2}{\mathrm{CuO}}_{4},$ ${\mathrm{Sr}}_{2}{\mathrm{CuO}}_{2}{\mathrm{Cl}}_{2},$ and ${\mathrm{Nd}}_{2}{\mathrm{CuO}}_{4}.$ These intrinsic excitations of the undoped ${\mathrm{CuO}}_{2}$ layers are lower in energy than the charge-transfer excitation. Temperature-dependent optical-absorption measurements are presented from 10 to 450 K. Photoinduced absorption measurements on single-crystal ${\mathrm{La}}_{2}{\mathrm{CuO}}_{4}$ are also presented. Recent theoretical work and optical-absorption experiments on ${\mathrm{La}}_{2}{\mathrm{NiO}}_{4},$ as well as the copper oxides, provide strong evidence that a sharp absorption peak seen in all the copper oxides at photon energy \ensuremath{\sim}0.4 eV and a related peak near 0.25 eV in ${\mathrm{La}}_{2}{\mathrm{NiO}}_{4}$ arise from phonon-assisted creation of a quasibound two-magnon state. A comparison between the intrinsic absorption in ${\mathrm{La}}_{2}{\mathrm{NiO}}_{4}$ and that in the copper oxides suggests that the broad midinfrared absorption bands observed between 0.4 and 1.2 eV in the undoped copper oxides have a different electronic origin. We discuss our measurements in regards to two proposed origins (phonon-multimagnon and exciton sidebands) for these broad higher-energy bands. We find that multimagnon and phonon sidebands associated with a Cu ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}\ensuremath{\rightarrow}{d}_{{3z}^{2}\ensuremath{-}{r}^{2}}$ crystal-field exciton at \ensuremath{\sim}0.5 eV plausibly explain the structure, strength, and polarization dependence of these broadbands. Direct observation of this exciton would unambiguously confirm or refute this model.

Charge and spin excitations of insulating lamellar copper oxides

A consistent description of low-energy charge and spin responses of the insulating ${\mathrm{Sr}}_{2}$${\mathrm{CuO}}_{2}$${\mathrm{Cl}}_{2}$ lamellar system is found in the framework of a one-band Hubbard model which besides U includes hoppings up to third nearest neighbors. By combining mean-field calculations, exact diagonalization results, and quantum Monte Carlo simulations, we analyze both charge and spin degrees of freedom responses as observed by optical conductivity, angular-resolved photoemission spectroscopy Raman and inelastic neutron-scattering experiments. Within this effective model, long-range hopping processes flatten the quasiparticle band around (0,\ensuremath{\pi}). We calculate also the nonresonant ${\mathrm{A}}_{1\mathrm{g}}$ and ${\mathrm{B}}_{1\mathrm{g}}$ Raman profiles and show that the latter is composed by two main features, which are attributed to two- and four-magnon scattering.

Ferromagnetic Moment and Spin Rotation Transitions in Tetragonal AntiferromagneticSr2Cu3O4Cl2

${\mathrm{Sr}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{4}{\mathrm{Cl}}_{2}$ is a variant of the lamellar copper oxides, containing an extra ${\mathrm{Cu}}^{2+}$ ion in the center of every second plaquette of the square ${\mathrm{CuO}}_{2}$ lattice. The two types of Cu form interpenetrating Heisenberg antiferromagnets, which order at 380 and 40 K. Magnetization measurements yield a small spontaneous ferromagnetic moment below 380 K and two spin rotation transitions. The results are explained in detail by a pseudodipolar coupling between the two Cu lattices. A quantitative analysis of the data yields several previously unknown microscopic coupling constants, relevant to other lamellar, chain, and ladder copper oxides.

Polyoxyethylene intercalation in lamellar copper iron sulfide

The insertion of polyethyleneoxide in a lamellar copper iron sulfide of formula CuFeS 2 by an exchange reaction of potassium from KCuFeS 2 with an aqueous solution of the polymer was performed. The characterization of the new compound by X-ray diffraction and IR absorption spectroscopy shows that the layer structure of the precursor has been retained and that the polymer adopts a zigzag configuration between the layers.

Magnetic fluctuations in lamellar copper oxides

Magnetic fluctuations in lamellar copper oxides

Phonon assisted multimagnon optical absorption and long lived two-magnon states in undoped lamellar copper oxides.

We calculate the effective charge for multimagnon infrared (IR) absorption assisted by phonons in the parent insulating compounds of cuprate superconductors and the spectra for two-magnon absorption using interacting spin-wave theory. Recent measured bands in the mid-IR [Perkins et al., Phys. Rev. Lett. 71, 1621 (1993)] are interpreted as involving one phonon plus a two-magnon virtual bound state, and one phonon plus higher multimagnon absorption processes. The virtual bound state consists of a narrow resonance occurring when the magnon pair has total momentum close to $(\ensuremath{\pi},0)$.

Spin structures of tetragonal lamellar copper oxides.

The spin Hamiltonian of tetragonal lamellar antiferromagnets is shown to contain several novel anisotropies. Symmetry allows bond-dependent anisotropic exchange interactions, which lead to (a) interplane mean-field coupling and (b) an in-plane anisotropy which vanishes classically but arises from quantum zero point energy (QZPE). A similar QZPE involving the interplane isotropic interaction prefers collinear spins. Adding also diploar anisotropy, the competition between all these effects explains for the first time the spin structures of many cuprates.

Spin fluctuations in insulating, weakly metallic and superconducting La 2− xSr xCuO 4

We review the results of a comprehensive set of neutron scattering experiments on the spin fluctuations in La 2− x Sr x CuO 4 with x varying between 0 and 0.15. For 0< x⪕0.0175 the materials exhibit 3D Néel order; for x=0 the spin correlations above T N are accurately described by recent theory for the 2D S=1/2 Heisenberg antiferromagnet. For 0.02⪕ x⪕0.04 the spin fluctuations are purely 2D with a spin correlation length which is independent of temperature below ≈250K. Remarkably, in this concentration range the spin correlation length follows the simple form ξ -1( x, T)=ξ -1( x,0+ξ -1(0. T). Further, the generalized susceptibility integrated around the (π, π) antiferromagnetic position follows a simple scaling function in the variable ω/ T thus providing a natural explanation for various normal state properties of the lamellar copper oxides. For x≳0.06 the spin fluctuations are incommensurate; we find in a sample with x=0.15 and T c=33 K that the spin fluctuations at low energies for T⪕100 K are quite sharp in momentum space. Further, for energies as low as 1.5 meV the spin fluctuations persist into the superconducting state with no significant change in the incommensurate geometry down to 2 K.

Mid-infrared optical absorption in undoped lamellar copper oxides.

Common optical absorption features are observed near 0.5 eV in four undoped single-crystal copper oxides: ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$, ${\mathrm{Nd}}_{2}$${\mathrm{CuO}}_{4}$, ${\mathrm{Pr}}_{2}$${\mathrm{CuO}}_{4}$, and ${\mathrm{Sr}}_{2}$${\mathrm{CuO}}_{2}$${\mathrm{Cl}}_{2}$. These absorption bands are shown to be weakly electric dipole allowed excitations of the ${\mathrm{CuO}}_{2}$ layers. The features are ascribed to an exciton near 0.4 eV, probably of crystal field origin, with strong multimagnon sidebands. Our observations provide an important basis for understanding the doped materials.

Four-band model for oxygen holes in copper oxide superconductors. II. Phase diagram.

Transport in the doped lamellar copper oxides is carried by quasiparticles, composed of holes which move on the oxygen ions on the CuO{sub 2} planes, with strong magnetic coupling to the neighboring Cu spins. In the preceding paper, we calculated the bands of these quasiparticles. In the present paper, we use the lowest of these bands to obtain the critical temperature {ital T}{sub {ital c}} as a function of the concentration of holes in these planes, using simple BCS equations. We find that the pairing interaction induced by the magnetic frustration model of Aharony {ital et} {ital al}. yields a phase diagram which is quite similar to the one observed experimentally, provided that one allows hopping between the planes, of order 0.03 eV. We discuss the variation of the phase diagram with the different hopping and interaction parameters. Some features should apply beyond the scope of our specific model.

Néel transition and sublattice magnetization of pure and doped La2CuO4.

We have measured the sublattice magnetization of stoichiometric ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$ (${\mathit{T}}_{\mathit{N}}$=325 K) and ${\mathrm{La}}_{2}$${\mathrm{Cu}}_{0.95}$${\mathrm{Zn}}_{0.05}$${\mathrm{O}}_{4}$ (${\mathit{T}}_{\mathit{N}}$=157 K). We discuss the data for ${\mathrm{La}}_{2}$${\mathrm{CuO}}_{4}$ and other lamellar copper oxides in terms of the quantum Heisenberg model including weak XY anisotropy and interlayer coupling. Spin-wave theory and a generalized Schwinger-boson mean-field theory are used to predict the ordered moment as a function of temperature without adjustable parameters. We also discuss the influence of different dopants on the N\'eel temperature and sublattice magnetization.

Novel magnetic phenomena in lamellar copper oxide superconductors (invited) (abstract)

In the lamellar copper oxide superconductors, magnetic phenomena play a fundamental role. Pure La2CuO4 is a nearly ideal realization of the two-dimensional, S= 1/2 Heisenberg model, a system of basic interest in statistical physics. Doping with holes has a dramatic effect on the Cu2+-Cu2+ spin correlations. A hole concentration of 2% is sufficient to destroy the Néel state and to produce a novel spin-glass phase. In this talk we will review the results of a series of neutron-scattering studies of the static and dynamic spin fluctuations in the antiferromagnetic, spin-glass, and superconducting regions of the La2−xSrxCuO4 phase diagram. Emphasis will be placed on recent results in the pure material La2CuO4 (Ref. 1) and in the superconductor La1.85Sr0.15CuO4.2 For a general review see Ref. 3.