Revealing the Dynamic Lithiation Process of Copper Disulfide by in Situ TEM.

Transition metal oxides, fluorides, and sulfides are extensively studied as candidate electrode materials for lithium-ion batteries driven by the urgency of developing next-generation higher energy density lithium batteries. These conversion-type electrode materials often require nanosized active materials to enable a "smooth" lithiation and de-lithiation process during charge/discharge cycles, determined by their size, structure, and phase. Herein, the structural and chemical changes of Copper Disulfide (CuS2) hollow nanoparticles during the lithiation process through an in situ transmission electron microscopy (TEM) method are investigated. The study finds the hollow structure of CuS2 facilitates the quick formation of fluidic Li2S "drops," accompanied by a de-sulfurization to the Cu7S4 phase. Meanwhile, the metallic Cu phase emerges as fine nanoparticles and grows into nano-strips, which are embedded in the Li2S/Cu7S4 matrix. These complex nanostructured phases and their spatial distribution can lead to a low de-lithiation barrier, enabling fast reaction kinetics.

Eco-friendly cubic-ZnS coupled Cu7S4 spines on chitosan matrix: Unravelling defect-engineered nanoplatform for the photodegradation of p-chlorophenol.

Novel ZnS-Cu7S4 nanohybrid supported on chitosan matrix, as an ideal photocatalyst, was fabricated by the sonochemical method wherein high-resolution transmission electron microscopy (HRTEM) and X-ray powder diffraction (XRD) analysis confirmed the co-existence of both ZnS and Cu7S4; presence of vacancy sites in ZnS was verified by electron paramagnetic resonance (EPR) analysis and their introduction could promote two-photon excitation facilitated visible light response and charge transport/separation. The type II interface is formed in the ZnS-Cu7S4/Chitosan heterojunction owing to interstitial states that promote charge separation. The ZnS-Cu7S4/Chitosan was used for the photodegradation of a pharmaceutical pollutant, p-chlorophenol (PCP); over 98.8% of PCP photodegradation was achieved under visible-light irradiation where the ensued ·O2- and ·OH serve a key role in the photodegradation of PCP. In vitro cytotoxicity studies substantiated that the ZnS-Cu7S4/Chitosan is nontoxic to the ecosystem and human beings and endowed with promising photodegradation properties and accessibility via an environmentally friendly design, bodes well for its potential remediation applications.

Shape-Controlled Synthesis of High-Quality Cu7 S4 Nanocrystals for Efficient Light-Induced Water Evaporation.

Copper sulfides (Cu2-x S), are a novel kind of photothermal material exhibiting significant photothermal conversion efficiency, making them very attractive in various energy conversion related devices. Preparing high quality uniform Cu2-x S nanocrystals (NCs) is a top priority for further energy-and sustainability relevant nanodevices. Here, a shape-controlled high quality Cu7 S4 NCs synthesis strategy is reported using sulfur in 1-octadecene as precursor by varying the heating temperature, as well as its forming mechanism. The performance of the Cu7 S4 NCs is further explored for light-driven water evaporation without the need of heating the bulk liquid to the boiling point, and the results suggest that as-synthesized highly monodisperse NCs perform higher evaporation rate than polydisperse NCs under the identical morphology. Furthermore, disk-like NCs exhibit higher water evaporation rate than spherical NCs. The water evaporation rate can be further enhanced by assembling the organic phase Cu7 S4 NCs into a dense film on the aqueous solution surface. The maximum photothermal conversion efficiency is as high as 77.1%.

Effective CuO/Cu7S4 nanospheres heterostructures for advanced "rocking-chair" zinc-ion battery.

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted considerable attention for energy storage owing to their environmental friendliness and high safety. However, the adverse side reactions and unsatisfactory cycle life brought by Zn-metal anodes limit their large applications. Herein, CuO/Cu7S4 (CSO) heterostructured hollow nanospheres is proposed as an attractive conversion-type Zn-metal-free anode for "rocking-chair" ZIBs. The CSO/graphite self-supporting electrode delivers a high capacity of 271 mAh/g at current density of 0.1 A/g and a superior cyclic stability of 1200 cycles. Based on the excellent electrochemical performance of CSO/graphite electrode, we have constructed a self-powered pressure sensor integrated system using the "rocking-chair" zinc ion battery as the power source, demonstrating significant practicality. This work provides a high-performance conversion type anode material for aqueous multivalent metal ion batteries.

Copper sulfides (Cu7S4) nanowires with Ag anchored in N-doped carbon layers optimize interfacial charge transfer for rapid water sterilization.

There are many methods of water disinfection, and how to realize low energy consumption, high efficiency and safety sterilization has always been a research hotspot. In this work, Cu7S4 nanowires were grown on copper foam, and coated with N-doped carbon layer and Ag particles, which not only improved the conductivity and local field enhancement regions of the material, but also improved the durability and mechanical stability of Cu7S4. DFT (Density functional theory) calculation shows that different kinds of N doping make the electron difference density and work function of the surrounding C different, which leads to high carrier transport capacity at the interface, and Ag anchored in N-doped carbon films can adsorb O2. The band gap of the material is 2.12 eV, and the material has the potential to generate superoxide anion under energy excitation. Under the condition of 6 V voltage and 1000 mL min-1 water flow rate, the long-term water filtration sterilization of high-concentration bacteria can be realized, and the removal efficiency can still reach 99% after 8 h continuous treatment. This work has great application prospects for the purification of highly polluted water in the future.

Efficient photothermal and photodynamic synergistic antibacterial therapy of Cu7S4 nanosheets regulated by facet engineering.

The surface arrangements of nanomaterials can regulate their electronic structure, which will tune physicochemical properties of materials to various applications. In this study, two Cu7S4 nanosheets with (304) and (224) exposed facets were synthesized, respectively, and their antibacterial activity of different facets for replacing antibiotics to solve seriously drug-resistant bacteria were further measured. Experimental and theoretical computation results unveiled that Cu7S4 with (224) exposed facet exhibited excellent antibacterial activity through synergetic photodynamic and photothermal therapy against Gram-positive Bacillus subtilis, Gram-negative Escherichia coli and drug-resistant Pseudomonas aeruginosa under near-infrared light (808 nm) irradiation. Furthermore, the antibacterial agents strongly inhibit mouse skin infection by drug-resistant Pseudomonas aeruginosa cells. The findings provide an efficient antibacterial strategy and might advance the method of designing and producing highly effective antibacterial nanomaterials through facet engineering.

Nanotwinned Structure-Dependent Photocatalytic Performances of the Multipod Frameworks of Cu7S4 Hollow Microcages.

The 14-pods Cu7S4 hollow microcages wholly exposed with nanotwinned building blocks were successfully prepared by an ethanol-assisted sacrificial Cu2O template approach. Its photocatalytic activity for the degradation of methylene blue (MB) was determined. The results suggest that the Cu7S4 microcages with nanotwinned building blocks possess higher catalytic activity than the Cu7S4 microcages without the nanotwinned structures, suggesting that the special nanotwinned components can improve the catalytic performance of the multipod framework. Further investigate reveals that the nanotwins inside the Cu7S4 microcages can facilite the transport of free charges, decrease the recombination of photoinduced electrons and holes, and elongate the lifetime of the electron-hole pairs. Our work will provide powerful evidence that the nanotwinned building blocks of the synthesized Cu7S4 microcages play a crucial role for the high catalytic activity.

Dual-Mode Electrochemical Immunoassay for Insulin Based on Cu7S4-Au as a Double Signal Indicator.

The detection of insulin by electrochemical (EC) immunoassay is desirable but highly challenged due to the obstacle of improving its accuracy, especially in a single-response system. In this work, based on Cu7S4-Au as a dual signal indicator, we fabricated a dual-mode electrochemical immunoassay for insulin. Especially, Cu7S4 presents a strong differential pulse voltammetry (DPV) signal for the electron transfer between Cu2+ and Cu+, without the addition of K3[Fe(CN)6] or other electron transfer mediators. Furthermore, Cu7S4 displays high sensitivity and high electrocatalytic activity toward the reduction of H2O2 through chronoamperometry (CA). The introduction of Au nanoparticles can not only link on the surface of Cu7S4 by the chemical bond of Au-SH, but also connect the second antibody (Ab2) by the chemical bond of Au-N. Due to the superior electroconductivity of Au nanoparticles and the synergistic effect between the Au nanoparticles and Cu7S4, a high sensitivity is achieved by means of DPV and CA. To improve the loading capacity of antibodies, nanofiber polyaniline covalently grafted graphene (GS-PANI) linked with Au nanoparticles (GS-PANI-Au) as the matrix material was prepared. Based on Cu7S4-Au as a double signal indicator, the developed EC immunoassay for insulin exhibits a wide linear response for insulin detection in the range from 0.1 pg/mL to 50 ng/mL, with a low detection limit of 35.8 and 12.4 fg/mL through DPV and CA modes, respectively. Furthermore, the immunosensor displays an excellent analytical capability for insulin and promises application in quantitative detection of other disease markers in clinical diagnosis.

Morphology-dependent electrochemical behavior of 18-facet Cu7S4 nanocrystals based electrochemical sensing platform for hydrogen peroxide and prostate specific antigen.

18-facet polyhedron Cu7S4 nanocrystal and CuS sphere were prepared from Cu2O precursor, and CuS flower was synthesized through a simple solvothermal approach. Their electrochemical performances were investigated towards H2O2 and it was interesting to discover that Cu7S4 nanocrystal had the best electrochemical catalysis compared with CuS sphere and CuS flower. It can deduce that the special structure of Cu7S4 nanocrystal endowed it more exposed active points, higher surface area and higher Cu/S ratio. Therefore, Cu7S4 nanocrystal was firstly employed to prepare a nonenzymatic biosensor for H2O2. Satisfactory results were obtained. In addition, a label-free sensing platform for prostate specific antigen (PSA) was constructed based on electrochemical catalysis towards H2O2 of Cu7S4 nanocrystal. The label-free immunosenosr offered accurate PSA in the range of 0.001-15 ng/mL with the detection limit of 0.001 ng/mL. Besides, the immunosensor possessed good sensitivity, selectivity and stability and could detect PSA in real sample. More importantly, this work demonstrated that Cu7S4 nanocrystal hold great promising application in electrochemical sensors.

Highly Efficient Visible-Light-Driven Photocatalytic Hydrogen Production on CdS/Cu7S4/g-C3N4 Ternary Heterostructures.

Hydrogen production through photocatalytic water splitting has attracted much attention because of its potential to solve the issues of environmental pollution and energy shortage. In this work, CdS/Cu7S4/g-C3N4 ternary heterostructures are fabricated by ion exchange between CdS and Cu+ and subsequent ultrasonication-assisted self-assembly of CdS/Cu7S4 and g-C3N4, which provide excellent visible-light photocatalytic activity for hydrogen evolution without any noble metal cocatalyst. With the presence of p-n junction, tuned band gap alignments, and higher charge carrier density in the CdS/Cu7S4/g-C3N4 ternary heterostructures that can effectively promote the spatial separation and prolong the lifetime of photogenerated electrons, a high hydrogen evolution rate of 3570 µmol g-1 h-1, an apparent quantum yield of 4.4% at 420 nm, and remarkable recycling stability are achieved. We believe that the as-synthesized CdS/Cu7S4/g-C3N4 ternary heterostructures can be promising noble metal-free catalysts for enhanced hydrogen production from photocatalytic water splitting.