Covellite CuS Research Articles

Ternary CuZnS Nanocrystals: Synthesis, Characterization, and Interfacial Application in Perovskite Solar Cells.

Ternary CuZnS nanocrystals (NCs) are synthesized via a facile, scalable, noninjection method at low temperatures for the first time, wherein sodium ascorbate plays the dual roles of reducing agent and capping ligand in the preparation process. These NCs can be dispersed well in a polar solvent like dimethyl sulfoxide, and the average size is ∼4 nm as measured by transmission electron microscopy. The results of X-ray diffraction and X-ray photoelectron spectroscopy indicate that the crystal structure of CuZnS NCs displays covellite CuS-like structure and the Zn element partly occupies the Cu position. Also, the crystal structure of CuZnS NCs is completely converted from a covellite CuS structure into a digenite Cu9S5 structure when the NCs are treated above 350 °C. Moreover, CuZnS NCs demonstrate favorable hole transport properties. When it is employed in MAPbI3-based perovskite solar cells as a hole transport layer, a peak power conversion efficiency of 18.3% is achieved. Simultaneously, the devices based on CuZnS exhibit a remarkably reduced J-V hysteresis. The results indicate that CuZnS is a promising hole transport layer for enhancing perovskite solar cell performance and presents great potential for optoelectronic applications, as well.

CuS nanoflowers/semipermeable collodion membrane composite for high-efficiency solar vapor generation

The ever-dwindling freshwater sources and ever-increasing need for freshwater resources are regarded as two important concerns for current society. Solar vapor generation has proven to be an effective and reliable solar-driven technology to overcome these concerns. However, it is a big challenge to prepare low-cost and high-efficiency solar absorber for solar vapor generation. Herein, we report a novel structurally integrated solar absorber composed of CuS nanoflowers and semipermeable collodion membrane (SCM). Three-dimensional (3D) covellite CuS nanoflowers composed of nanosheets have been synthesized with a facile hydrothermal route and their morphology and structure are investigated with various analytical techniques. High solar vapor generation efficiencies of 68.6% and 81.2% were achieved with CuS/SCM under 1 and 4 sun irradiation, respectively, much higher than that of the CuS nanofluid. A stable solar vapor generation performance has been demonstrated over 20 cycles. These results display a promising potential of CuS/SCM as a solar-absorber for efficient solar vapor generation.

Morphology controlled synthesis and photocatalytic study of novel CuS-Bi2O2CO3 heterojunction system for chlorpyrifos degradation under visible light illumination

In this study, Bi2O2CO3 (BSC) nanoplates with high aspect ratio and hierarchical nanostructures were prepared by hydrothermal technique using urea/hexamethylenetetramine as hydrolysing agent and KCl as additive in different solvent systems. The relative molar proportion of urea and KCl was crucial for phase purity as well as thickness and planar dimension of the BSC plates. The BSC nanoplates were used as substrates to prepare CuS-Bi2O2CO3 (CuS/BSC) direct z-scheme heterojunction systems. The heterojunction materials were characterized by FESEM, HRTEM, XRD, PL, FTIR and UV–Vis-DRS techniques. The presence of crystalline tetragonal BSC and hexagonal covellite CuS phase was inferred from XRD study. Morphologically, the CuS/BSC material contained CuS nanorods and BSC nanoplates. HRTEM study suggested microscopic close contact between the CuS nanorods and BSC nanoplates. Optical property study revealed improvement in visible light absorption and enhanced separation of excitons. The CuS/BSC materials were used as photocatalyst for chlorpyrifos pesticide degradation under visible light irradiation. The heterojunction materials were highly active achieving >95% degradation within 3 h of reaction. The pathway and mechanism of CP degradation was elucidated using GCMS and radical scavenger experiments.

Valence Selectivity of Cation Incorporation into Covellite CuS Nanoplatelets

Synthesis of copper sulfide-based nanomaterials by cation incorporation into copper deficient copper sulfide (Cu2–xS) is of interest as a powerful means to obtain nanostructures with otherwise inaccessible combinations of size, shape, composition, and crystal phase. Incorporation of a heterocation (M) may produce heterogeneous Cu2–xS-MS nanocrystals (NCs) or homogeneous Cu-M-S alloys. However, the factors determining whether heterogeneous NCs or homogeneous alloy NCs are produced have not been fully elucidated. In this report, we incorporate diverse cations into covellite CuS nanoplatelet (NPl) templates in the presence of dodecanethiol (DDT). These cations are categorized by their valencies. We demonstrate that trivalent and tetravalent cations can be incorporated into reduced CuS NPls to produce homogeneous ternary alloy NPls, while the divalent cations cannot coexist with Cu+ ions in the Cu2–xS phase. In turn, the incorporation of divalent cations leads to formation of heterogeneous NPls and finally pr...

The effect of the Cu+/Cu2+ ratio on the redox reactions by nanoflower CuNiOS catalysts

CuNiOS bimetal oxysulfide catalysts with catalytic activity in the dark were synthesized by a feasible solution method below 100 °C. It has a hexagonal CuS covellite structure with the Cu+/(Cu++Cu2+) molar ratio above 0.6. S6+ was formed to balance the deficiency in positive charge due to a high Cu+ content. The effect of hydrazine (N2H4) amount added during the CuNiOS synthesis on the redox reactions was evaluated. The N2H4-free CuNiOS showed the fast methylene blue (MB) degradation capability and the [N2H4]-high CuNiOS had the high Cr(VI) reduction capability all in the dark condition. The adjustable redox reactions by the CuNiOS catalyst system are demonstrated and explained. The catalytic reaction mechanism is elucidated, depending upon the Cu+/Cu2+ ratio for different charge transports. CuNiOS also exhibited relatively good stability and durability during its reusability tests. The catalytic reactions under the mild conditions without heat and electrical and thermal energies are encouraging for green synthesis.

Generating plasmonic heterostructures by cation exchange and redox reactions of covellite CuS nanocrystals with Au3+ ions.

We demonstrate the fabrication of various types of heterostructures, including core-shells and dimers. This is achieved by reacting platelet-shaped covellite (CuS) nanocrystals (NCs) with Au3+ ions under various reaction conditions: the exposure of CuS NCs to Au3+ ions, in the presence or in the absence of ascorbic acid (AA), leads to the formation of CuS@Au core-shell nanostructures; the reaction of CuS NCs with Au3+ ions in the presence of oleylamine (OM) leads to the formation of CuS@Au2S; the presence of both OM and AA leads to the formation of Au/CuS dimers. Depending on which condition is chosen, either cation exchange (CE) between gold and copper ions is predominant (leading to amorphous Au2S) or the reduction of Au3+ leads to the nucleation of metallic Au domains (which are operated by the AA). In the heterostructures achieved by CE, the Au2S shell is almost entirely amorphous, and can be converted to polycrystalline upon electron beam irradiation. Finally, when both oleylamine and AA are present in the reaction environment, Au/CuS dimers are formed due to the reduction of Au3+ to metallic Au domains which nucleate on top of the CuS seeds. The experimental dual plasmonic bands of the CuS@Au core-shells and Au/CuS dimers are in agreement with the theoretical optical simulations. The procedures described here enable the synthesis of core-shell nanostructures with tunable localized surface plasmon resonances (LSPRs) in the near-infrared (NIR) region, and of plasmonic metal/semiconductor heterostructures with LSPRs in both the NIR and the visible regions.

Thermoelectric properties of Ag-doped CuS nanocomposites synthesized by a facile polyol method.

We report the first thermoelectric properties of Cu1-xAgxS, x = 0-0.75 nanocomposites, synthesized by using a facile polyol method. Systematic characterizations using powder XRD, Rietveld refinement of XRD, EDAX, XPS and Raman spectroscopy confirmed their single phase, hexagonal crystal structure with the space group P63/mmc, nominal elemental composition, valence states of the constituent elements and stoichiometric nature. The TEM images showing the CuS formation of nearly perfect hexagonal disk-like particles of average thickness 26.7 nm and breadth ranging in a few hundreds of nanometers with nanorods stacked from these hexagonal nanodisks (NDs) elongated along the c axis corroborate the FESEM images. Attributed to structural phase transition, an anomaly at 55 K is clearly observed in both the thermopower and Hall resistivity data. By increasing x, a systematic reduction in thermal conductivity was observed near 300 K. Consequently, a 50% enhancement in figure of merit was observed for Cu0.9Ag0.1S as compared to pure CuS at 300 K. These results therefore are expected to provide a new direction in improving ZT near 300 K.

Room temperature synthesis of aqueous soluble covellite CuS nanocrystals with high photothermal conversion

Generating aqueous soluble covellite CuS nanocrystals with well-defined NIR plasmon absorbance by reacting Cu2+ with S2− ions via a facile and scalable protocol at room temperature, in the presence of various ligands.

Chemical spray pyrolysis synthesis of covellite copper sulphide (CuS) thin films for economical counter electrode for DSSCs

Thin films of covellite copper sulphide (CuS) were deposited on FTO substrates using chemical spray pyrolysis technique. Influence of Cu-to-S molar ratio on structural, surface morphological, optical and electrical properties were systematically investigated using variety of characterization techniques. Formation of covellite CuS films was confirmed by low angle-XRD and Raman spectroscopy. The field emission scanning electron microscopy analysis revealed the formation of faceted CuS particles without secondary growth. Optical studies exhibited decrease in optical band gap (from 2.21 to 1.69 eV) with increase in Cu-to-S molar ratio. Electrical properties were investigated using Van der Pauw four point probe method and Hall measurements revealed that as-synthesized CuS films have low sheet resistance (1.47–2.45 Ω/□), high carrier mobility (8.90–54.89 cm2/Vs) and high sheet concentration (1016–1018/cm2). The CuS films deposited at optimized Cu-to-S molar ratio (1:2.5) were then further studied for electrochemical impedance spectroscopy and photovoltaic characteristics. A quantum-dot sensitized solar cell incorporating optimized CuS film as counter electrode showed power conversion efficiency of ~ 1.05% with Voc ~ 0.46 V, Isc ~ 1.01 mA/cm2 and fill factor ~ 0.34%. Although the cell is not fully optimized and better results can be anticipated.

Switching between Plasmonic and Fluorescent Copper Sulfide Nanocrystals.

Control over the doping density in copper sulfide nanocrystals is of great importance and determines its use in optoelectronic applications such as NIR optical switches and photovoltaic devices. Here, we demonstrate that we can reversibly control the hole carrier density (varying from >1022 cm–3 to intrinsic) in copper sulfide nanocrystals by electrochemical methods. We can control the type of charge injection, i.e., capacitive charging or ion intercalation, via the choice of the charge compensating cation (e.g., ammonium salts vs Li+). Further, the type of intercalating ion determines whether the charge injection is fully reversible (for Li+) or leads to permanent changes in doping density (for Cu+). Using fully reversible lithium intercalation allows us to switch between thin films of covellite CuS NCs (Eg = 2.0 eV, hole density 1022 cm–3, strong localized surface plasmon resonance) and low-chalcocite CuLiS NCs (Eg = 1.2 eV, intrinsic, no localized surface plasmon resonance), and back. Electrochemical Cu+ ion intercalation leads to a permanent phase transition to intrinsic low-chalcocite Cu2S nanocrystals that display air stable fluorescence, centered around 1050 nm (fwhm ∼145 meV, PLQY ca. 1.8%), which is the first observation of narrow near-infrared fluorescence for copper sulfide nanocrystals. The dynamic control over the hole doping density and fluorescence of copper sulfide nanocrystals presented in this work and the ability to switch between plasmonic and fluorescent semiconductor nanocrystals might lead to their successful implementation into photovoltaic devices, NIR optical switches and smart windows.

An experimental and theoretical study on soft chemically grown CuS thin film for photosensor application

Herein we report, the photosensitivity of in-situ chemical bath deposition (CBD) grown CuS thin film for the first time, also comparatively very short deposition time of 40min and much lower bath temperature i.e. 45°C are reported. The structural, surface topographical, optical, electronic and electrical properties of as-grown CuS thin film have been investigated. The XRD analysis revealed the formation of Orthorhombic (Covellite) structure with preferential growth along [113] direction having ~14nm average crystallite size. Raman spectrum indicating a sharp peak at 474cm−1 confirms the formation of CuS covellite structure. Polycrystalline nature of the film has been confirmed from the concentric ring pattern obtained from TEM–SAED and AFM revealed the rough surface topography with RMS roughness of ~27nm. The bond lengths of Cu(1)-S(1) and S(1)-S(1) were obtained from the DFT calculations based on GGA approximation, suggest S-S bond is much stronger as compared to Cu-S bond; these results are in good agreement with the Raman result. The film shows higher absorbance in the visible region with a band gap of 2.2eV. The electrical properties show a drastic increase in current after light illumination of 50 W which increases with increasing light intensity and tends to attain a saturation state around 200 W. The highest photosensitivity of ~66% has been calculated for 200 W with fast response time of ~34s and a complete recovery. These results represent CuS thin films promising candidature for photosensor application.

Electrochemical performance of 2D polyaniline anchored CuS/Graphene nano-active composite as anode material for lithium-ion battery

Lithium-ion battery (LIB) is a revolutionary step in the electric energy storage technology for making green environment. In the present communication, a LIB anode material was constructed by using graphene/polyaniline/CuS nanocomposite (GR/PANI/CuS NC) as a high-performance electrode. Initially, pure covellite CuS nanoplates (NPs) of the hexagonal structure were synthesized by hydrothermal route and then GR/PANI/CuS NC was fabricated by in-situ polymerization of aniline in the presence of CuS NPs and graphene nanosheets (GR NSs) as host matrix. GR/PANI/CuS NC-based LIB has shown the superior reversible current capacity of 1255mAhg−1, a high cycling stability with more than 99% coulombic efficiency over 250 cycles even at a high current density of 5Ag−1, low volume expansion, and excellent power capabilities. Galvanostatic charge/discharge tests and cyclic voltammetry analysis were used to investigate electrochemical properties. The electrochemical test proves that GR/PANI/CuS NC is promising anode material for LIB. The crystal phases and purity of the GR/PANI/CuS NC were confirmed by X-ray diffraction (XRD). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) were employed to examine the morphology, size, chemical composition, and phase structure of the synthesized GR/PANI/CuS NC.

Influences of substrate type on the pH sensitivity of CuS thin films EGFET prepared by spray pyrolysis deposition

Copper sulphide (CuS) thin films were deposited by spray pyrolysis using CuCl2·2H2O and Na2S2O3·5H2O precursors as sources of Cu2+ and S2- respectively, with deionized water as a solvent. Three types of substrates were used for films deposition; glass, tungsten and Si. X-ray measurements of the structural characteristics of the deposited films indicated single phase CuS covellite phase with orientations in the z-axis (001). The presence of oxygen suggested improved pH sensing characteristics. Morphological characterization showed differences in shape and size of CuS crystal structure, which affect the surface-to-volume ratio and surface site density of the substrates. The as-deposited films were used as extended gates of field effect transistor to measure the pH sensitivity for buffer solutions in the set of 2-to-12 step 2; the optimum pH sensitivity was 23.3mV/pH for CuS/glass membrane. The hysteresis was measured for buffer solutions prepared at pH7-pH4-pH7-pH10-pH7 in order to find its pH response delay; the minimum value was 0.48mV for glass substrate. Also, the repeatability, stability and reliability of the (CuS) thin films were measured in terms of coefficient of variation (C.V.) with the same setup used for measuring pH sensitivity. Repeatability values of 0.04%, 0.02% and 0.38% were recorded for glass, tungsten and Si, respectively, while stability and reliability values of 0.15%, 0.15% and 0.10% were recorded at pH4, pH7 and pH10, respectively, for glass substrate.

A novel CuS thin film deposition method by laser-assisted spray photolysis deposition and its application to EGFET

Several studies have deposited copper sulphide (CuS) thin films via spray pyrolysis using a heater. In this study, the spray pyrolysis deposition of CuS thin films was carried out using two processes; the first process called pyrolytic process to deposit CuS thin film on glass, ITO, Si and tungsten substrates using CW CO2 laser beam (10.6μm, 40W) as the heat source rather than a heater, while the second process called photolytic process to deposit CuS thin film on glass substrate by apply the laser directly on the droplet after leaving the nozzle. Copper chloride and sodium thiosulfate were used as precursor materials for the preparation of CuS. Deionized water was used to dissolve 0.4M concentration of copper chloride and sodium thiosulfate, separately. In pyrolytic process, the glass, ITO, Si and tungsten substrates were placed on a rotator fan to provide large surface area coating, and to ensure uniform distribution of laser beam heat and the sprayed solution through deposition. Hence, homogenous films of CuS nanocrystallites with covellite phase with good structural and morphological characteristics were obtained. In photolytic process, the glass substrate was placed on the heater and the laser was guided toward the droplet exactly after leaving the nozzle, to achieve resonant absorption of the laser by aerosols. The structure of this film was differ from the previous films, it contains S element in addition to the pure CuS covellite phase. The membrane surface parameters (number of ions, crystallite size, surface-to-volume ratio of these crystallites and contact angle) were investigated to determine the pH sensor applicability of the CuS membranes deposited by CO2 laser beam. The CuS membrane deposited onto glass substrate showed the optimum pH sensing performance: 31.7mV/pH with linearity of 99.56% & hysteresis 1.65mV (pyrolytic process), and 40mV/pH with 97.78% & hysteresis 0.53mV (photolytic process), respectively.

Using Deionized Water with Ethanol as a Solvent of CuS EGFET as pH Sensor

In this research work, copper sulphide was deposited on glass substrate using spray pyrolysis deposition. The precursors were dissolved in deionized water (DIW) and ethanol, mixed at a ratio of 7:3. The distance between nozzle and substrate was 30 cm and the substrate temperature was maintained at 200 °C. XRD spectra analysis showed four distinctive peaks of high intensity, which indicate pure CuS covellite phase with average crystallite size of 28.3 nm. FESEM characterization of the thin film structure showed a mixture of very small nanoplates and larger square-and triangular-shaped particles. The application of the film as pH sensor showed it has exceptional qualities that include sensitivity and linearity of 22.9 mV/pH and 93.8%, hysteresis of 23.75 mV, repeatability (C.V.) of 0.11% for pH7, stability and reliability (C.V.) of 0.13%, 0.12% and 0.08% for pH 4, 7 and 10, respectively. This research work confirms the feasibility of using CuS thin film as extended membrane in pH sensor and biosensor applications.

Effects of Concentration and Substrate Type on Structure and Conductivity of p-Type CuS Thin Films Grown by Spray Pyrolysis Deposition

Copper sulphide (CuS) thin films were grown upon Ti, indium tin oxide (ITO), and glass substrates by using spray pyrolysis deposition at 200°C. The films exhibited good adhesion compared to chemical bath deposition. CuCl2·2H2O and Na2S2O3·5H2O precursors were used as Cu2+ and S2− sources, respectively. Two concentrations (i.e., 0.2 M and 0.4 M) were selected in this study. X-ray diffraction analysis reveals that the films with 0.2 M showed only the formation of a covellite CuS phase having a hexagonal crystal structure with diffraction peaks of low intensity. For 0.4 M concentration, in addition to the covellite CuS phase, chalcocite Cu2S phase having a hexagonal crystal structure also appeared with relatively higher intensity peaks for all thin films. Field-emission scanning electron microscopy observations showed the formation of small grains for 0.2 M, whereas a mixture of grains with square-like shape and nanoplates were formed for 0.4 M. Depending on the 0.2 M and 0.4 M thin films thicknesses (3.2 μm and 4 μm, respectively), the band gap energy was obtained from optical measurements to be approximately 2.64 eV for 0.2 M (pure CuS phase), which slightly decreased up to 2.56 eV for 0.4 M concentration. Hall effect measurements showed that all grown films are p-type. The 0.2 M film exhibited much lower sheet resistance (R sh = 33.96 Ω/Sq–55.70 Ω/Sq) compared to 0.4 M film (R sh = 104.33 Ω/Sq–466.6 Ω/Sq). Moreover, for both concentrations, the films deposited onto ITO substrate showed the lowest sheet resistance (R sh = 33.96 Ω/Sq–104.33 Ω/Sq).

Covellite CuS as a matrix for “invisible” gold: X-ray spectroscopic study of the chemical state of Cu and Au in synthetic minerals

Geological processes leading to formation of sulfide ores often result in precipitation of gold-bearing sulfides which can contain high concentrations of this metal in “invisible” (or “refractory”) state. Covellite (CuS) is ubiquitous mineral in many types of the ore deposits, and numerous studies of the natural ores show that covellite can contain high concentrations of Au. At the same time, Au-bearing covellite withstands cooling in contrast to other minerals of the Cu–Fe–S system (chalcocite, bornite, chalcopyrite), where Au exsolves at low temperatures. This makes covellite a convenient model system for investigation of the chemical state (local environment and valence) of the “invisible” Au in copper-sulfide ores (copper-porphyry, epithermal, volcanogenic massive sulfide, SEDEX deposits). Therefore, it is necessary to determine the location of Au in the covellite matrix as it will have important implications for the methods employed by mineral processing industry to extract Au from sulfide ores. Here we investigate the chemical state of Cu and Au in synthetic covellite containing up to 0.3wt.% of Au in the “invisible” state. The covellite crystals were synthesized by hydrothermal and salt flux methods. Formation of the chemically bound Au is indicated by strong dependence of the concentration of Au in covellite on the sulfur fugacity in the experimental system (d(log C(Au))/d(log f(S2))∼0.65). The Au concentration of covellite grows with increasing temperature from 400 to 450°C, whereas further temperature increase to 500°C has only minor effect. The synthesized minerals were studied using X-ray absorption fine structure spectroscopy (XAFS) in high energy resolution fluorescence detection (HERFD) mode. Ab initio simulations of Cu K edge XANES spectra show that the Cu oxidation state in two structural positions in covellite (tetrahedral and triangular coordination with S atoms) is identical: the total loss of electronic charge for the 3d shell is ∼0.3 for both positions of Cu. This result is confirmed by theoretical analysis of electron density performed using quantum theory of atoms in molecules (QTAIM). Modeling of the Au L3 edge EXAFS/XANES spectra showed that Au in covellite exists in the form of the isomorphous solid solution formed by substitution for Cu atoms in triangular coordination with the Me–S distance in the first coordination shell increased by 0.18Å relative to the pure CuS structure. The “formal” oxidation state of Au in covellite is +1. The Bader partial atomic charge for Au in covellite is lower than the charge of Cu (+0.2e vs. +0.5e) indicating that the degree of covalency for the Au-bearing covellite is higher than that of pure CuS. The analysis of electronic density of states shows that this structural position of Au results in strong interactions between hybridized Au s,p,d, S p, and Cu p,d orbitals. Such chemical bonding of Au to S and Cu can result in the formation of Au-bearing solid solution with other minerals in the Cu–Fe–S system.

Effect of copper concentration on the physical properties of ZnS:Cu alloys prepared by chemical bath deposition

ZnS:Cu thin films were deposited on glass substrates by chemical bath deposition technique. The structural, morphological, optical and electrical properties of the grown films were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectrometry, scanning electron microscopy, spectrophotometry, spectrofluorimetry and Hall effect measurements. Both XRD and Raman analysis indicated the coexistence of both sphalerite ZnS and covellite CuS with cubic and hexagonal structures, respectively. The optical band gap of the films increased from 3.70 to 3.75 eV with Cu concentration increment. Photoluminescence studies revealed that the incorporation of Cu2+ ions in ZnS matrix blue shifted and quenched the emission bands. Electric resistivity, volume carrier concentration, surface carrier concentration and Hall mobility were determined from Hall effect measurements. Indeed, for pure sample, the obtained values were about 7.586 × 104 Ω cm, 1.472 × 1011 cm−3, 2.944 × 106 cm−2 and 5.590 × 102 cm2 V−1 s−1, respectively. However, after Cu incorporation, these values varied in the range of (2.273 × 104–13.80 × 104) Ω cm, (2.334 × 1011–9.094 × 1013) cm−3, (4.668 × 106–1.819 × 109) cm−2 and (3.092 × 10−1–1.937 × 102) cm2 V−1 s−1, respectively.

Structural, optical, magnetic and photocatalytic properties of Co doped CuS diluted magnetic semiconductor nanoparticles

Pristine and Co doped covellite CuS nanoparticles were synthesized in aqueous solution by facile chemical co-precipitation method with Ethylene Diamine Tetra Acetic Acid (EDTA) as a stabilizing agent. EDAX measurements confirmed the presence of Co in the CuS host lattice. Hexagonal crystal structure of pure and Co doped CuS nanoparticles were authenticated by XRD patterns. TEM images indicated that sphere-shape of nanoparticles through a size ranging from 5 to 8nm. The optical absorption edge moved to higher energies with increase in Co concentration as indicated by UV–vis spectroscopy. Magnetic measurements revealed that bare CuS sample show sign of diamagnetic character where as in Co doped nanoparticles augmentation of room temperature ferromagnetism was observed with increasing doping precursor concentrations. Photocatalytic performance of the pure and Co doped CuS nanoparticles were assessed by evaluating the degradation rate of rhodamine B solution under sun light irradiation. The 5% Co doped CuS nanoparticles provide evidence for high-quality photocatalytic activity.

Synthesis and characterization of ZnO/ZnS/CuS ternary nanocomposites as high efficient photocatalyst in visible light

The ZnO/ZnS/CuS ternary nanocomposites have been successfully synthesized by a simple and cost-efficient three-step synthetic route, namely homogeneous precipitation, chemical conversion and cation exchange. The structures, morphologies and optical properties of the prepared samples were characterized by powder X-ray diffraction, Field emission scanning electron microscopy and Ultraviolet–visible spectroscopy. The X-ray diffraction result demonstrates that the ternary material is the composite of hexagonal wurtzite ZnO, hexagonal wurtzite ZnS and hexagonal covellite CuS. The FESEM images of the ternary nanocomposites with thickness about 15 nm show they are nonuniform lamellas. Compared with ZnO and ZnO/ZnS, the ternary nanocomposites exhibit enhanced optical absorption property in visible-light region. Moreover, the visible-light photocatalysis of ZnO/ZnS/CuS ternary nanocomposites has remarkably improved and we attribute it to its excellent utilization efficiency of visible-light and gradient energy level structure.