Crystalline Cu2 Research Articles

Engineering the Au-Cu2 O Crystalline Interfaces for Structural and Catalytic Integration.

Precise structural control has attracted tremendous interest in pursuit of the tailoring of physical properties. Here, this work shows that through strong ligand-mediated interfacial energy control, Au-Cu2 O dumbbell structures where both the Au nanorod (AuNR)and the partially encapsulating Cu2 O domains are highly crystalline. The synthetic advance allows physical separation of the Au and Cu2 O domains, in addition to the use of long nanorods with tunable absorption wavelength, and the crystalline Cu2 O domain with well-defined facets. The interplay of plasmon and Schottky effects boosts the photocatalytic performance in the model photodegradation of methyl orange, showing superior catalytic efficiency than the AuNR@Cu2 O core-shell structures. In addition, compared to the typical core-shell structures, the AuNR-Cu2 O dumbbells can effectively electrochemically catalyze the CO2 to C2+ products (ethanol and ethylene) via a cascade reaction pathway. The excellent dual function of both photo- and electrocatalysis can be attributed to the fine physical separation of the crystalline Au and Cu2 O domains.

Transport and thermoelectric properties of crystalline Cu2−xAgxSe alloys prepared by facile method

Crystalline alloys of Cu2−Se containing a transition metal, Earth-abundant and eco-friendly element, are studied in this article as promising eco-friendly thermoelectric materials. Thermoelectric and transport properties of Cu2−xAgxSe (x = 0.00, 0.01, 0.03, 0.05, 0.07) bulk alloys were studied in the temperature range 273–473 K. Crystal structure and surface morphology were tested by X-ray diffraction analysis and scanning electron microscope. Electrical conductivity measurements showed metallic conduction behaviour besides a tremendous decrease in its values with increasing Ag content (x). In contrast, Ag-doping increased the Seebeck coefficient to a large extent. Calculations of the electronic thermal conductivity showed that phonon scattering is increased due to the Ag-doping. The incorporation of Ag-atoms resulted in existence of point defects, introduced secondary phases which significantly reduced the thermal conductivity. Such effects resulted in enhanced ZT, specially at higher Ag-content. The largest ZT value was recorded at 0.25, achieved for Cu1.93Ag0.07Se at 473 K, which is about two times of that observed for the pristine Cu2Se sample. The overall findings of the current study clearly demonstrates that the increasing of the Ag content helps to obtain good TE properties of the cubic Cu2−xAgxSe system, specially at higher temperatures.

From micro to macro: Freestanding electrode based on low crystalline Cu2−xSe for sodium storage

The development of electrode materials is a crucial parameter in improving sodium storage’s electrochemical performance. In this study, Cu2−xSe obtained from Cu-based metal–organic frameworks embedded in nanofibers (Cu2−xSe@C@NCNFs) shows excellent electrochemical performance as a freestanding anode for sodium storage. The “macro” aspects of 1D nanofibers as the skeleton not only inhibit Cu2−xSe agglomeration and structural collapse during the charge–discharge process, but also enhance the electrical conductivity. In this “from micro to macro” unique structure, on the “micro” aspect, Cu2−xSe nanoparticles with low crystallinity enhance the specific capacity and electrochemical reaction kinetics further. Moreover, the initial Coulombic efficiency can be as high as 66.3%. Furthermore, after 1000 cycles at 2 A g−1, Cu2−xSe@C@NCNFs demonstrated a specific capacity of 74 mAh g−1. The outstanding electrochemical performance shows that “from micro to macro” Cu2−xSe@C@NCNFs is a potential electrode material for effective sodium storage.

Atomic-level insights into the activation of nitrogen via hydrogen-bond interaction toward nitrogen photofixation

Summary As the activation of N2 molecules is generally regarded as the bottleneck in N2 reduction, it is of significant importance to develop promising strategies to efficiently activate N2 molecules. Herein, we discovered an innovative approach to activate N2 molecules via hydrogen-bond interaction in N2 photofixation. Porous Cu with surface modification of S atoms (3%-S/Cu) exhibited remarkable catalytic activity and stability in N2 photofixation. Further mechanistic studies revealed that surface S atoms directly participated in the catalytic process by accepting and donating H atoms. In addition, the forming S–H bond significantly promoted the activation of N2 molecules via hydrogen-bond interaction, contributing to the enhanced catalytic activity.

Development of Crystalline Cu2S Nanowires via a Direct Synthesis Process and Its Potential Applications.

Large-scale and uniform copper(I) sulfide (Cu2S) nanowires have been successfully synthesized via a cheap, fast, easily handled, and environmentally friendly approach. In addition to the reductive properties of the biomolecule-assisted method, they also have a strong shape- or size-directing functionality in the reaction process. The field-emission properties of the Cu2S nanowires in a vacuum were studied by the Folwer–Nordheim (F–N) theory. The Cu2S nanowires have a low turn-on field at 1.19 V/μm and a high enhancement factor (β) of 19,381. The photocatalytic degradation of Cu2S nanowires was investigated by the change in the concentrations of rhodamine B (RhB) under UV illumination. These outstanding results of Cu2S nanowires indicate that they will be developed as good candidates as electron field emitters and chemical photocatalysts in future nanoelectronic devices.

Chalcogenide solution-mediated activation protocol for scalable and ultrafast synthesis of single-crystalline 1-D copper sulfide for supercapacitors

One-dimensional Cu2S nanostructuresviaa facile and room-temperature sulfur activation for supercapacitors.

One‐Pot Synthesis of Crystalline Ag2S Nanoparticles Embedded inside Amorphous Cu2S Matrix for High Electrical Conductivity

AbstractAmorphous materials exhibit distinct physical and chemical properties compared to crystalline or quasi‐crystalline phases, because of their unique atomic arrangements of short‐range order but long‐range disorder. Designing a nanocomposite that contains both crystalline and amorphous phases is a valid approach to fully exploit the effects of each component. In this work, a nanocomposite consisting of crystalline Ag2S nanoparticles embedded in an amorphous Cu2S matrix (Ag2S/a‐Cu2S) is synthesized by a facile one‐pot solvothermal method. This process is achieved by diffusing silver into crystalline Cu2S. The silver is able to diffuse into Cu2S and form crystalline Ag2S nanoparticles inside them, while the crystalline Cu2S is converted into an amorphous phase owing to the silver diffusion. Furthermore, the introduction of nanoscale Ag2S particles into Cu2S improve electrical conductivity. This design of amorphous matrix containing nanocrystalline particles may open up new strategies for the transition from crystalline to amorphous phases of semiconductors.

Studies on the developing of Nano-Structured Cu2S film for photovoltaic application

Current efforts have been given to develop new photovoltaic materials to improve the efficiency with reducing cost. The factors that have been taken into account in developing new photovoltaic materials include: a suitable energy band gap, the possibility of depositing the material using low cost deposition methods, abundance of the elements and low environmental costs with respect to the synthesis of the elements, production, operation and disposal of modules. It’s been a long time that continuous efforts has been given to find out the most appropriate material to be employed as absorber material for solar cell and some advanced material has been proposed too as potential solar cell material. Here in our present study we have taken Cu2-xS as a suitable p-type absorber layer material but the formation of stable Cu2-xS film was being difficult task. Different researchers proposed different methods among them we have found the elemental stacked layer deposition method is one of the promising technique. But this technique requires further optimization on thickness and layer no’s to get the best result with required stoichiometry. With this context we have tried to optimize the thickness and layer no’s for developing multilayer Cu2-xS thin film on the glass substrate by physical vapour deposition technique. The results obtained in this method shows that the optimum numbers of layer is 10 ensures formation of crystalline Cu2S structure with optical band gap is around 1.65 eV to 1.85 eV by different characterization technique like XRD, EDX, SEM, Spectrophotometry and PL. The I-V characteristic of Schotkey junction using silver and bulk resistance (ρb) with the sample shows semiconductor behaviour of the same. To the best of our knowledge this is the first time such type of nano-structured Cu2S film fabrication is reported.

High figure-of-merit p-type transparent conductor, Cu alloyed ZnS via radio frequency magnetron sputtering

p-type transparent conducting Cu alloyed ZnS thin films from CuZnS targets (, 0.2, 0.3, 0.4, and 0.5) were deposited on glass substrates via radio frequency sputtering. x-ray diffraction and TEM–SAED analysis show that all the films have sphalerite ZnS as the majority crystalline phase. In addition, films with 30% and 40% Cu show the presence of increasing amounts of crystalline Cu2S phase. Conductivity values ⩾400 S were obtained for the films having 30% and 40% Cu, with the maximum conductivity of 752 S obtained for the film with 40% Cu. Temperature dependent electrical transport measurements indicate metallic as well as degenerate hole conductivity in the deposited films. The reflection-corrected transmittance of this Cu alloyed ZnS (40% Cu) film was determined to be ⩾75% at 550 nm. The transparent conductor figure of merit () of the Cu alloyed ZnS (40% Cu), calculated with the average value of transmittance between 1.5 to 2.5 eV, was ≈276 .

Effects of Carrier Density and Shape on the Localized Surface Plasmon Resonances of Cu2–xS Nanodisks

A major challenge in the synthesis of plasmonic semiconductor nanocrystals is the ability to control localized surface plasmon resonance (LSPR) properties by varying the size, shape, and carrier density of the nanocrystal. For example, copper sulfide (Cu2–xS) nanodisks possess two distinct LSPR modes that occur in the infrared range. Here, we demonstrate that the wavelengths of these LSPR modes can be modulated by independently varying the aspect ratio of the disk and the overall carrier density of Cu2–xS. These variables can be controlled during nanocrystal growth by carrying out thermolysis of a copper-thiolate precursor under a specific gas environment. Our results show that during thermolysis, the presence of oxygen enhances the growth rate of crystalline Cu2–xS nanodisks and the formation of Cu vacancies that contribute to free carrier concentration. By carrying out thermolysis under a nitrogen environment, we are able to tune the aspect ratio of nanodisks independent of Cu vacancy formation. Using these methods to carefully control nanodisk size and carrier density, we demonstrate that nanodisks achieve a critical carrier density beyond which the nanocrystals undergo an irreversible phase change, placing a limit on LSPR wavelength tuning in these doped semiconductor nanocrystals.

Comprehensive studies of non-covalent interactions within four new Cu(ii) supramolecules

This work investigates the supramolecular aggregation of Cu(II) complexes based on a combination of the heterocyclic N-donor ligand 2-aminopyrimidine (2-apym) and a variety of different carboxylate ligands, like salicylic acid (H2SAL), maleic acid (H2MAL), and glycine (HGLY). Four new Cu(II) complexes [Cu(HSAL)2(2-apym)2] (I), [Cu(HSAL)2(2-apym)2]·(H2SAL)2(2-apym) (I′), {(H2-apym)[Cu(GLY)(μ-Cl)2Cl]}n (II) and [Cu(μ-MAL)(2-apym)]n (III) have been synthesized and characterized by elemental analyses, FT-IR spectra, and X-ray structural analyses. I and I′ appear as molecular clusters whereas II is a 1-D coordination polymer with weak axial Cu–Cl interactions. However the last one shows a 2-D coordination polymer with trigonal bipyramidal geometry for Cu(II) ion. The two last cases have no molecular fragments packed with non-covalent interactions. In these new supramolecular compounds, existent species join together with the cooperation of multiple inter/intra-molecular classical O–H⋯O/N, N–H⋯O/N, and non-classical N–H⋯Cl hydrogen bonds (H-bonds), offset face to face π⋯π, edge to face C/N–H⋯π, and lp⋯π stacking interactions in the form of various homo/hetero-synthons leading to architecturally different structures. DFT calculations were used to estimate the binding energy of the involved non-covalent interactions and whole stabilization energy of related network of I, I′, and II. Theoretical calculations facilitate the comparison of intermolecular interactions, which demonstrate that for all of I–II, N–H⋯N and N–H⋯O H-bonds govern the network formation. The equilibrium constants for the three proton-transfer systems including SAL/2-apym, GLY/2-apym, MAL/2-apym, the stoichiometry and stability of complexation of these systems with Cu2+ ion in aqueous solution were investigated by potentiometric pH titration method. The stoichiometries of the most complex species in solution was compared to the crystalline Cu2+ ion complexes with the cited proton-transfer systems.

Synthesis and Thermoelectric Property of Cu2−xSe Nanowires

Single crystalline Cu2−xSe nanowires with lengths up to 50 μm are synthesized via a modified composite hydroxide mediated method. Experiments reveal that both quantity and species of hydroxides or amount of water used in the preparation would affect final morphology of Cu2−xSe crystals, from nanoplates to nanorods to nanowires. The UV−visible−near-infrared reflection spectrum demonstrates the absorption edges of the Cu2−xSe nanowires in the ultraviolet and near-infrared region, which could be interpreted in terms of direct transitions from a band gap of 2.38 eV and indirect transitions from a band gap of 1.12 eV. The band-to-band transition model has been proposed. In addition, Seebeck effect based on the Cu2−xSe nanowire film is investigated, demonstrating the Seebeck coefficient of 180 μV/K.

Design and growth of dendritic Cu2−xSe and bunchy CuSe hierarchical crystalline aggregations

Dendritic nanocrystals of copper selenide were fabricated in situ for the first time by using alcohol as the solvent. Cu2−xSe films composed of hierarchically ordered dendritic nanostructures were prepared on Cu substrates at a rather moderate temperature of 190–200 °C for just 1–3 h, while bunchy CuSe nanostructures could be further constructed above the Cu2−xSe dendrites by prolonging the reaction time of solvothermal growth with ethanol as the solvent. The resulting Cu2−xSe nanodendrites display highly symmetric corolitic morphology while the bunchy CuSe aggregations show particular nanostructures with a pronounced trunk and actinomorphic multi-branches. It is also found that the dendritic structures of crystalline Cu2−xSe could never be obtained when the reaction temperature is less than 190 °C, while the temperature needed is 160 °C for Ag2Se nanodendrites and higher than 220 °C for CdSe nanodendrites. These copper selenide nanostructures with hierarchically ordered 3-dimensional (3D) framework exhibited good absorbance and photoluminescence (PL) property and could bear potential applications in solar cell devices in the future.

Synthesis and characterization of Cu x S nanoparticles. Nature of the infrared band and charge-carrier dynamics

Abstract CuxS (x = 1,2) nanoparticles have been synthesized utilizing different capping molecules including polyethyleneglycol (PEG), polyvinylpyrrolidone (PVP), casein hydrolysate-enzymatic (CAS), and bovine serum albumin (BSA). The ground-state electronic absorption spectra of the CuxS nanoparticles show three distinct types of CuxS formed: a green type assigned as crystalline CuS, and two brown types assigned as crystalline Cu2S and amorphous Cu2S. The brown types exhibit a steady increase in absorption toward shorter wavelengths starting at around 650 nm, while the green type shows the same steady increase in absorption, but with an additional absorption band in the infrared (IR). The IR band is attributed to an electron-acceptor state lying within the bandgap. ESR measurements of free Cu(II) ions in solution for all samples show the presence of Cu(II) in the brown amorphous samples, but not in the green or brown crystalline samples. Ultrafast dynamics of photoinduced electrons have been measured for all samples using femtosecond-transient absorption/bleach spectroscopy. In all brown Cu2S samples studied, the early time-transient profiles feature a pulse-width-limited (<150 fs) rise followed by a fast decay (1.1 ps) and a slow decay (>80 ps). These decay dynamics were found to be independent of pump power and stabilizing agent. The fast 1.1 ps decay is attributed to charge carrier trapping, while the long decay may be due to either recombination or deep trapping of the charge carriers. The green CuxS samples studied showed interesting power-dependent behavior. At low excitation intensities, the green CuxS samples showed a transient bleach signal, while at high intensities, a transient absorption signal has been observed. The increased transient absorption over bleach at high intensities is attributed to trap-state saturation. A kinetic model has been developed to account for the main features of the electronic relaxation dynamics.

Convenient, room-temperature, amine-assisted routes to metal sulfides, selenides and tellurides †

The reaction of elemental powders of Ag, Pb and Hg with S, Se or Te in n-butylamine for 12–72 h produced crystalline metal chalcogenides ME (M = Pb or Hg; E = S, Se or Te) and Ag2E in good yield (>90%). The reactions of Cu with Se or Te in n-butylamine gave crystalline Cu2–xSe and Cu0.64Te0.36, whilst the reaction of Cu or Ni with sulfur under similar conditions produced an amorphous material that on heating to 250–300 °C for 2 h yielded crystalline NiS and Cu2S. Products were analysed by Fourier-transform IR, Raman spectroscopy, scanning electron microscopy with energy dispersive analysis by X-rays, powder X-ray diffraction and X-ray photoelectron spectroscopy. The elemental reactions were also investigated in n-hexylamine, ethane-1,2-diamine, cyclohexane and aqueous ammonia solution.

Phase transformation study of Cu2S

The phase transformations of crystalline Cu2S in the temperature range 50‡C to 600‡C have been studied through electric quadrupole interactions of111Cd impurities observed by time-differential perturbed angular correlations. The Cd is subject to no discernable quadrupolar interaction in the cubic phase above 430‡C. In the hexagonal phase between approximately 103‡C and 430‡C, a single-site, weakly temperature dependent, axially symmetric quadrupolar interaction is found. At lower temperature, the structure is complex with a number of different sites. These data were taken with a microcomputer-controlled TDPAC spectrometer with logical steering that allows a standard 4-detector spectrometer to collect simultaneously 12 channels of data.

Theory of natural optical activity in crystalline Cu2+:ZnSeO4.6H2O

The chiroptical properties associated with the d-d transitions of Cu2+ ions in crystalline Cu2+:ZnSeO4.6H2O are examined on a theoretical model which is based on a crystal-field representation of the Cu2+ d-d states, and which includes explicit consideration of pseudo Jahn-Teller distortions within the manifold of Cu2+ ligand field states. In Cu2+:ZnSeO4.6H2O, the Cu2+ ions are located at sites of C 2 symmetry. However, the six oxygen atoms (from H2O) coordinated directly to Cu2+ form a near perfect octahedron so that the ‘crystal field’ as felt by the Cu2+ 3d electrons deviates only slightly from cubic (Oh ) symmetry. This results in a ‘nearly degenerate’ electronic ground state which is subject to pseudo Jahn-Teller distortion. Calculations are carried out which incorporate both the crystal field and vibronic coupling (pseudo Jahn-Teller interactions) aspects of the fundamental theoretical model. The signs and magnitudes of the computed rotatory strengths are in qualitative agreement with experimental o...