Copper Iron Sulfide Research Articles

Copper Iron Sulfide Nanocrystal‐Bulk Silicon Heterojunctions for Broadband Photodetection

AbstractThis study describes the optoelectronic characteristics of CuFeS2/Si nanocrystal/bulk heterojunctions. These heterojunctions show a strong photocurrent response under ambient conditions upon excitation from a wide optical spectrum, from 460 to 2200 nm. The devices comprise of a heterojunction formed between heavily doped n‐type silicon (1–100 Ω cm) and copper iron sulfide (CuFeS2) nanocrystal films. Over the spectral range 460–2200 nm the device shows a fast response (20 µs at NIR wavelengths), along with responsivity and detectivity of 4.68 mA W−1 and 5.29 × 109 Jones at 1900 nm wavelength. The photocurrent is further observed to be a nonlinear function of power. These properties of the devices are discussed in terms of a defect filling mechanism. Besides their regular photoresponse described above, the devices also exhibit a slower photothermal response, allowing these to also sense hot objects (450 K; excess 6 mW incident onto the device) within the focal plane, thereby extending the useful sensing range of the devices deeper into the infrared.

Structural, morphological and optical properties of iron sulfide, cobalt sulfide, copper sulfide, zinc sulfide and copper-iron sulfide nanoparticles synthesized from single source precursors

Iron sulfide (1), cobalt sulfide (2), copper sulfide (3), zinc sulfide (4), and copper-iron sulfide (5) nanoparticles were prepared from [Fe(dbzdtc)3], [Co(dbzdtc)3], [Cu(dbzdtc)2], [Zn(dbzdtc)2] and [Cu(dbzdtc)3][FeCl4] (where dbzdtc = N,N-dibenzyldithiocarbamate), respectively. The synthesized samples 1–5 were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), UV–Vis, photoluminescence and Fourier transform infrared (FT-IR) spectroscopy techniques. In the X-ray diffraction patterns of samples 1, 3–5, sharp peaks are observed which indicates that the as-prepared metal sulfide nanoparticles, 1,3–5 are crystalline. EDAX spectra confirm the composition of the metal sulfides. The SAED spots of as-prepared copper sulfide and zinc sulfide supports the crystalline nature of the nanoparticles. UV–Vis absorption and photoluminescence spectra of the synthesized nanoparticles 1–5 show a significant blue shift compared to that of the respective bulk metal sulfide. Infrared spectral studies on metal sulfides (Samples 1,2,4 and 5) confirm the presence of capping agent ethylenediamine (en).

Electrochemical Selectivity for Metals in Molten Sulfides

Molten sulfides show promise as an alternative electrolyte for production of metals such as copper and silver. They provide a means to sidestep the current emissions- and waste- heavy processes used both in primary (e.g. from ore) and secondary (e.g. recycled product) streams by direct reduction of a metal's sulfide form, such as Cu2S, to produce metal and sulfur. Experiments with molten sulfide electrolytes have shown high efficiency in the reduction of copper sulfides and iron sulfides to their metals. Data have also demonstrated high solubility of precious metals silver and gold, and stable electrochemical signals during reduction, evidence for a viable and streamlined method of precious metal refining and recycling. The current work focuses on predicting which metal, and of what purity, is reduced from the electrolyte. Because the standard-state reduction potentials of copper and iron sulfides are very close to each other (less than 100mv), and because the reduction potentials of silver and gold sulfides are also hypothesized to be close in value with each other, there is a possibility of co-deposition occurring, compromising the purity of the final metal product. By carefully tailoring the activities of the electrolyte species and cathode products, it is possible to bias the reduction reaction towards one species over another. Therefore, the thermodynamics of both the electrolyte and metal product should be very well defined. This talk will discuss experiments in determining metal/sulfide equilibria and how that equilibrium relates to efforts in modeling the cathode product.

Synthesis and characterization of copper(II) dithiocarbamate complexes involving pyrrole and ferrocenyl moieties and their utility for sensing anions and preparation of copper sulfide and copper–iron sulfide nanoparticles

Bis(N‐(pyrrol‐2‐ylmethyl)‐N‐butyldithiocarbamato‐S,S′)copper(II) (1), bis(N‐(pyrrol‐2‐ylmethyl)‐N‐(2‐phenylethyl)dithiocarbamato‐S,S′)copper(II) (2), bis(N‐methylferrocenyl‐N‐(2‐phenylethyl)dithiocarbamato‐S,S′)copper(II) (3) and bis(N‐furfuryl‐N‐methylferrocenyldithiocarbamato‐S,S′)copper(II) (4) were prepared and characterized using elemental analysis and infrared and UV–visible spectroscopies. X‐ray diffraction (XRD) studies on 3 show that each copper centre adopts the square planar geometry by the coordination of four sulfur atoms of the metalloligand N‐methylferrocenyl‐N‐(2‐phenylethyl)dithiocarbamate. The CuS distances are symmetrical and are in the range 2.293–2.305 Å. The supramolecular architecture in complex 3 is sustained in the solid state by CH⋅⋅⋅π, CH⋅⋅⋅S, Fe⋅⋅⋅Fe and H⋅⋅⋅H interactions. Density functional theory calculations were carried out for 3. Anion (F−, Cl−, Br− and I−) binding studies with complex 1 were performed using cyclic voltammetry. Copper sulfide, copper–iron sulfide‐1 and copper–iron sulfide‐2 nanoparticles were prepared from complexes 2, 3 and 4, respectively, and they were characterized using powder XRD, transmission electron microscopy (TEM) and energy‐dispersive X‐ray, UV–visible, photoluminescence and infrared spectroscopies. TEM images of copper–iron sulfide‐1 and copper–iron sulfide‐2 reveal that the particles are spherical and oval shaped, respectively. Photocatalytic activities of as‐prepared nanoparticles were studied by decolourization of methylene blue and rhodamine‐B under UV light. It was found that copper–iron sulfide degrades methylene blue and rhodamine‐B much better than does copper sulfide.

Effect of complexing agents: investigations on structural, morphological, topographical and optical analysis of copper iron sulphide thin films deposited by chemical bath deposition method

Copper iron sulphide (FeCuS2) thin films deposited by chemical bath deposition method using ferrous sulphate and copper sulphate as cationic sources and sodium sulphide as anionic source with complexing agents, EDTA and Leishman stain were reported. The structural, optical and morphological studies were carried out using X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV–Visible spectroscopy techniques. The X-ray spectrum reveals that the films are polycrystalline nature and also showed the deposition of cubic phases at room temperature. The SEM images for prepared films have clear morphology influenced by the complexing agents used in deposition process. The result of AFM studies shown that the particles in the film have grain size around ~ 60–70 nm and also have almost similar thickness. Based on the optical absorbance spectra the FeCuS2 film exhibited a high absorbance in the visible region. The absorption edge shifted toward lower wavelength with varying complexing agents. The band gap value obtained was found to be 3.57–3.85 eV. From these results, it is indicated that the prepared films are suitable candidate for solar cell applications.

Mechanism of Selenium Loss in Copper Slag

During smelting of copper sulfide concentrate, selenium is distributed between silica-saturated iron-silicate slag and copper-iron sulfide matte. The recovery coefficients of selenium between slag and matte were determined as a function of the initial concentration of selenium at 1523 K (1250 °C) under an inert atmosphere in a vertical tubular furnace. The initial concentration of selenium was varied by the addition of metallic selenium as well as selenium dioxide to the mixture of slag and matte. Analysis of the results indicated high affinity of selenium for matte. The apparent loss of selenium with the slag was attributed to the presence of selenium-enriched matte particles entrapped in the slag, rather than dissolved SeO2. The mechanisms proposed by previous investigators were discussed and also compared with the results of the present investigation.

The application of nanostructured transition metal sulfides as anodes for lithium ion batteries

With wide application of electric vehicles and large-scale in energy storage systems, the requirement of secondary batteries with higher power density and better safety gets urgent. Owing to the merits of high theoretical capacity, relatively low cost and suitable discharge voltage, much attention has been paid to the transition metal sulfides. Recently, a large amount of research papers have reported about the application of transition metal sulfides in lithium ion batteries. However, the practical application of transition metal sulfides is still impeded by their fast capacity fading and poor rate performance. More well-focused researches should be operated towards the commercialization of transition metal sulfides in lithium ion batteries. In this review, recent development of using transition metal sulfides such as copper sulfides, molybdenum sulfides, cobalt sulfides, and iron sulfides as electrode materials for lithium ion batteries is presented. In addition, the electrochemical reaction mechanisms and synthetic strategy of transition metal sulfides are briefly summarized. The critical issues, challenges, and perspectives providing a further understanding of the associated electrochemical processes are also discussed.

Spray pyrolysis synthesis of CuxFe1−xS2 and their structural, electronic and optical properties: Experimental and first-principles study

Iron pyrite, FeS2 (FS) and the chalcopyrite copper iron sulphide CuxFe1−xS2 (CFS) thin films were synthesized using chemical spray pyrolysis (CSP) deposition technique. The effect of different Cu concentration (1, 3, 5 and 7at.%) on growth of these films was investigated. The as-synthesized CFS thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and ultraviolet–visible (UV–Vis) spectroscopy. The XRD pattern of FS show a structured cubic phase with preferential orientation along (200) plane, and CFS crystallized in chalcopyrite (tetragonal) with preferential orientations along (112) plane with crystallite size 142–91Å. Optical absorption data show that the band gap of spray deposited FS and CFS films is 0.920–0.558eV and the absorption coefficients significantly modified with the increase of Cu concentration from 3.619×105cm−1 to 4.231×105cm−1. Furthermore, these results have been adopted in accordance with the first principles calculations of electronic structure.

XPS and XANES study of layered mineral valleriite

Mineral valleriite of the Talnakh deposit, which consists of alternating copper-iron sulfide layers and brucite-like layers of magnesium-aluminium hydroxide is studied for the first time by XPS at photon excitation energies ranging from 1.253 keV to 6 keV and CuL FeL, SL, AlL, MgK, and OK edge TEY XANES using synchrotron radiation. The comparison of the XPS and XANES spectra of valleriite and chalcopyrite, in particular, demonstrates that in the sulfide layers of valleriite, Cu+ and Fe3+ are in a tetrahedral coordination, however, a local positive charge on both cations is slightly lower than that in chalcopyrite, apparently, due to a structure disorder. The concentration of oxygen-bound iron decreases with an increase in the depth of the analyzed layer even after ion etching; probably, Fe does not enter into the brucite-like layer, but mainly forms its own surface structures.

Fluid-Enhanced Coarsening of Mineral Microstructures in Hydrothermally Synthesized Bornite–Digenite Solid Solution

Symplectic microstructures are abundant in copper–iron–sulfide minerals and are conventionally considered to form by solid-state diffusion processes. Here we experimentally demonstrate that coarsening of exsolution lamellae occurs ∼1000 times faster in the presence of a fluid compared to the equivalent dry system. Bornite–digenite solid solutions (Cu5FeS4–Cu8.52Fe0.11S4.88) were synthesized hydrothermally via the replacement of chalcopyrite, and we compared the microtextures in the product subjected to different cooling histories: (i) dry annealing after synthesis; (ii) cooling to an annealing temperature immediately following hydrothermal synthesis; and (iii) annealing in a hydrothermal fluid following quenching to room temperature and then reheating. We interpret the rapid coarsening of the exsolution lamellae in the presence of a fluid phase to result from recrystallization associated with healing of the open porous microstructure in the parent phase. The porosity is a consequence of the synthesis of t...

Development of partial extraction methods to estimate abundance of copper-iron sulphide minerals in the Escondida Norte porphyry copper deposit, Chile

Studies were conducted by Minera Escondida, Ltda. (MEL) between 1995 and 2003 to support an investment decision to open Escondida Norte, an enriched porphyry copper deposit adjacent to the Escondida mine and processing facilities. Due to the importance of copper-iron sulphide minerals in predicting metallurgical performance in both process alternatives, a quantitative spatial model of copper-iron sulphide mineral abundances was determined to be a critical study component. A suite of total and partial copper analyses already in common use was chosen to maximize relative selectivity among the major copper sulphide minerals in the mineral deposit. These analyses were merged with partial and total sulphur analysis and combined with a novel approach to interpret the analytical results as normative mineral estimates of chalcocite, covellite, chalcopyrite and pyrite content. Development and validation of the normative mineral estimates included verification on the analytical stability and reproducibility of the chemical analyses, determination of extraction rates on synthetic mineral standards, and comparison with modal mineral abundance on natural ore samples. Uncertainty of individual normative copper sulphide minerals is estimated at ±5% (95% confidence interval), while uncertainty on pyrite content is ±12%. The uncertainty of the normative mineral estimates are comparable to uncertainty of corresponding modal mineral estimates, and differences between modal and normative estimates are largely within the estimation uncertainty. While the methods were originally developed for a simple association based on supergene chalcocite ± covellite replacing and overprinting hypogene chalcopyrite + pyrite, subsequent work developed normative mineral models for bornite + chalcopyrite hypogene and mixed copper oxide-sulphide supergene mineralization.

System dynamics and discrete event simulation of copper smelters

Discrete event simulation (DES) is an appropriate framework for the plant-wide analysis of copper smelters. These smelters apply a common set of chemical reactions: copper-iron sulfides are blasted with oxygen-enriched air, sending the iron into a slag phase and the sulfur into the offgas. Moreover, conventional copper smelters exhibit similar operational dynamics: a smelting furnace operates continually, feeding into an alternating set of converters that produce batches of blister copper. The thermochemical and operational commonalities of copper smelters are integrated within the DES framework. This serves as a common basis to begin evaluating the system dynamics of individual smelters. For complex problems, the simulation framework should be developed in phases, incorporating feedback from different personnel who have complementary perspectives. Sample computations are provided in this paper based on the Hernan Videla Lira smelter, whose production is constrained by meteorological conditions.

Combined DFT and XPS investigation of iodine anions adsorption on the sulfur terminated (001) chalcopyrite surface

The adsorption of iodine anions (iodide and iodate) on the sulfur terminated (001) chalcopyrite surface has been systematically investigated combining first-principles calculations based on density functional theory (DFT) with X-ray photoelectron spectroscopy (XPS) measurements. Based on the total energy calculations and geometric optimization, the thermodynamically preferred site was copper atom for iodide adsorption and iron atom for iodate adsorption, respectively. In the case of Cu site mode, the iodate underwent a dissociative adsorption, where one IO bond of iodate ion was broken and the dissociative oxygen atom adsorbed on the adjacent sulphur site. Projected density of states (PDOS) analysis further clarified the interaction mechanism between active sites of chalcopyrite surface and adsorbates. In addition, full-range XPS spectra qualitatively revealed the presence of iodine on chalcopyrite surface. High resolution XPS spectra of the I 3d peaks after adsorption verified the chemical environment of iodine. The binding energies of 618.8eV and 623.5eV for I 3d5/2 peaks unveiled that the adsorption of iodide and iodate ions on copper-iron sulfide minerals was the result of formation of low solubility metal iodides precipitate. Also two I 3d peaks with low intensity around 618eV and 630eV might be related to the inorganic reduction of iodate to iodide by reducing S2− ion of chalcopyrite.

CuFeS2 Quantum Dots and Highly Luminescent CuFeS2 Based Core/Shell Structures: Synthesis, Tunability, and Photophysics.

We report the synthesis of copper iron sulfide (CuFeS2) quantum dots (QDs). These materials exhibit a tunable band gap that spans the range 0.5-2 eV (600-2500 nm). Although the as-prepared material is nonemissive, CuFeS2/CdS core/shell structures are shown to exhibit quantum yields that exceed 80%. Like other members of the I-III-VI2 family QDs, CuFeS2 based nanoparticles exhibit a long-lived emission that is significantly red-shifted compared to the band gap. CuFeS2 QDs are unique in terms of their composition. In particular, these QDs are the only band-gap-tunable infrared chromophore composed entirely of elements with atomic numbers less than 30.

Xanthate-Functional Temperature-Responsive Polymers: Effect on Lower Critical Solution Temperature Behavior and Affinity toward Sulfide Surfaces.

Xanthate-functional polymers represent an exciting opportunity to provide temperature-responsive materials with the ability to selectively attach to specific metals, while also modifying the lower critical solution temperature (LCST) behavior. To investigate this, random copolymers of poly(N-isopropylacrylamide) (PNIPAM) with xanthate incorporations ranging from 2 to 32% were prepared via free radical polymerization. Functionalization with 2% xanthate increased the LCST by 5 °C relative to the same polymer without xanthate. With increasing xanthate composition, the transition temperature increased and the transition range broadened until a critical composition of the hydrophilic xanthate groups (≥18%) where the transition disappeared completely. The adsorption of the polymers at room temperature onto chalcopyrite (CuFeS2) surfaces increased with xanthate composition, while adsorption onto quartz (SiO2) was negligible. These findings demonstrate the affinity of these functional smart polymers toward copper iron sulfide relative to quartz surfaces, presumably due to the interactions between xanthate and specific metal centers.

Two Ages of Copper Mineralization in the Mwombezhi Dome, Northwestern Zambia: Metallogenic Implications for the Central African Copperbelt

Approximately 10% of copper resources in the Central African Copperbelt, the world’s largest, sediment-hosted stratiform copper province, occur in the Domes region of northwestern Zambia. The copper deposits and prospects are commonly hosted by amphibolite-facies metamorphic rocks and lie within or adjacent to several basement inliers. Minor molybdenite accompanies the copper-iron sulfide minerals in two deposits and four prospects within the Mwombezhi dome as well as in deposits elsewhere in the Domes region. The results of Re-Os dating of 11 molybdenite samples reveal the existence of two discrete copper-mineralizing epochs, separated by >500 m.y. Most of the mineralization, including that in the Chimiwungu orebody at Lumwana, the largest deposit in the Mwombezhi dome, formed within a maximum interval of ~42 m.y. (538.9–497.1 Ma), which spans the peak of the Lufilian collisional orogeny. In contrast, three samples (four determinations) from the Nyungu prospect returned Mesoproterozoic ages of 1084 to 1059 ± 5 Ma, coincident with the Irumide collisional orogeny. Although several investigators have speculated that the copper in the Central African Copperbelt deposits was extracted from the basement, this is the first unambiguous evidence for an appreciable copper concentration of pre-Katangan (pre-Neoproterozoic) age. Based on this evidence, additional Mesoproterozoic and possibly even older copper concentrations seem likely to exist elsewhere beneath and/or alongside the Copperbelt in both Zambia and the Democratic Republic of Congo. Such preenrichment of the basement in copper may have contributed to the enormous metal endowment of the Central African Copperbelt.

Chalcopyrite Nanoparticles as a Sustainable Thermoelectric Material.

In this report, copper iron sulfide nanoparticles with various composition were synthesized by a thermolysis based wet chemical method. These inherently sustainable nanoparticles were then fully characterized in terms of composition, structure, and morphology, as well as for suitability as a thermoelectric material. The merits of the material preparation include a straightforward bulk material formation where particles do not require any specialized treatment, such as spark plasma sintering or thermal heating. The Seebeck coefficient of the materials reveals P-type conductivity with a maximum value of 203 µV/K. The results give insight into how to design and create a new class of sustainable nanoparticle material for thermoelectric applications.

High-quality draft genome sequence of Kocuria marina SO9-6, an actinobacterium isolated from a copper mine.

An actinobacterial strain, designated SO9-6, was isolated from a copper iron sulfide mineral. The organism is Gram-positive, facultatively anaerobic, and coccoid. Chemotaxonomic and phylogenetic properties were consistent with its classification in the genus Kocuria. Here, we report the first draft genome sequence of Kocuria marina SO9-6 under accession JROM00000000 (http://www.ncbi.nlm.nih.gov/nuccore/725823918), which provides insights for heavy metal bioremediation and production of compounds of biotechnological interest.

Methane origin and oxygen-fugacity evolution of the Baogutu reduced porphyry Cu deposit in the West Junggar terrain, China

Most porphyry copper deposits worldwide contain magnetite, hematite, and anhydrite in equilibrium with hypogene copper-iron sulfides (chalcopyrite, bornite) and have fluid inclusions with CO2 >> CH4 that are indicative of high fO2. In contrast, the Baogutu porphyry Cu deposit in the West Junggar terrain (Xinjiang, China) lacks hematite and anhydrite, contains abundant pyrrhotite and ilmenite in equilibrium with copper-iron sulfides (chalcopyrite), and has fluid inclusions with CH4 >> CO2 that are indicative of low fO2. The mineralized intrusive phases at Baogutu include the main-stage diorite stock and minor late-stage diorite porphyry dikes. The main-stage stock underwent fractional crystallization and country-rock assimilation-contamination, and consists of dominant diorite and minor gabbro and tonalite porphyry. The country rocks contain organic carbons (0.21–0.79 wt.%). The δ13CvPDB values of the whole rocks (−23.1 to −25.8 ‰) in the wall rocks suggest a sedimentary organic carbon source. The δ13CvPDB values of CH4 (−28.2 to −36.0 ‰) and CO2 (−6.8 to −20.0 ‰) in fluid inclusions require an organic source of external carbon and equilibration of their Δ13CCO2-CH4 values (8.2–25.0 ‰) at elevated temperatures (294–830 °C) suggesting a significant contribution of thermogenic CH4. Mineral composition data on the main-stage intrusions, such as clinopyroxene, hornblende, biotite, magnetite, ilmenite, sphene, apatite, and pyrrhotite, suggest that the primary magma at Baogutu was oxidized and became reduced after emplacement by contamination with country rocks. Mineral compositions and fluid inclusion gas compositions suggest that the redox state of the system evolved from logfO2 > FMQ + 1 in the magma stage, to logfO2 FMQ in the hydrothermal stage. Though oxidized magma was emplaced initially, assimilation-contamination of carbonaceous country rocks decreased its fO2 such that exsolved fluids contained abundant CH4 and deposited a reduced assemblage of minerals.

In situ observation of divergent phase transformations in individual sulfide nanocrystals.

Inorganic nanocrystals have attracted widespread attention both for their size-dependent properties and for their potential use as building blocks in an array of applications. A complete understanding of chemical transformations in nanocrystals is important for controlling structure, composition, and electronic properties. Here, we utilize in situ high-resolution transmission electron microscopy to study structural and morphological transformations in individual sulfide nanocrystals (copper sulfide, iron sulfide, and cobalt sulfide) as they react with lithium. The experiments reveal the influence of structure and composition on the transformation pathway (conversion versus displacement reactions), and they provide a high-resolution view of the unique displacement reaction mechanism in copper sulfide in which copper metal is extruded from the crystal. The structural similarity between the initial and final phases, as well as the mobility of ions within the crystal, are seen to exert a controlling influence on the reaction pathway.