Cuprous Oxide Research Articles

Semitransparent Cu2O films based on CuO Back Layer for Photoelelctrochemical Water Splitting and Photovoltaic Applications.

Cuprous oxide (Cu2O) as an intrinsic p-type semiconductor is promising for solar energy conversion. The major challenge in fabricating Cu2O lies in achieving both high transparency and high performance in a tandem device. The Cu2O photocathodes often employ gold as the back contact layer. However, it is not an optimal choice in tandem device due to its poor transmission, scarcity, and electron-hole recombination at the interface of Au and Cu2O. Here, we presented a facile method that utilizes the earth-abundant material copper oxide (CuO) to fabricate highly transparent Cu2O devices. The maximum transmittance of the Cu2O film on CuO (FTO/CuO/Cu2O) increased from 42% to 58% compared with Cu2O film on Au (FTO/Au/Cu2O) in 550-800 nm. After coating atomic layer deposition (ALD) layers and hydrogen evolution reaction (HER) catalyst, the photocurrent density at 0 V (versus RHE) of the semitransparent Cu2O photocathode with CuO as the back layer for photoelectrochemical (PEC) water splitting reached -4.9 mA·cm-2, which showed a 24.5% improvement compared with FTO/Au/Cu2O photocathode. Moreover, expanding the CuO layer strategy to the field of solar cells enables Cu2O solar cells to achieve a PCE of 2.37%.

Eco-Friendly and Low-Cost Synthesis of Transparent Antiviral- and Antibacterial-Coated Films Based on Cu2O and MIL-53(Al).

This research presents the development of an innovative antimicrobial coating consisting of cuprous oxide (Cu2O) integrated with the metal-organic framework MIL-53(Al) through an eco-friendly and low-cost synthesis method that employs glucose as a reducing agent under mild conditions. The microstructural properties of the composite materials were characterized by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The antibacterial efficacy of the Cu2O-MIL-53(Al) (CuM) composite was assessed against Escherichia coli and Staphylococcus aureus, achieving a reduction efficacy of 99.99% with 5% copper incorporated into the MIL-53(Al) framework within a contact time of 24 h. The incorporation of CuM into a macromolecular host matrix of polyurethane-carboxymethylcellulose (CuM/PUD-CMC), applied as a coating on a low-cost plastic film, produced a transparent film with 87.10% transparency. This coating demonstrated a 99.99% reduction in E. coli and S. aureus populations within a contact time of 24 h. The CuM/PUD-CMC coating demonstrated substantial antiviral efficacy, achieving inactivation rates of 99.35% for Human Coronavirus 229E, 99.40% for Influenza A virus, and 97.76% for Enterovirus 71 within a contact time of 5 min. The CuM nanoparticles exhibited low toxicity toward zebrafish while effectively eradicating bacteria and inactivating viruses. The proposed low-cost material and coating method demonstrate significant potential as a broad-spectrum antimicrobial and antiviral agent, highlighting its suitability for various applications in biomedical and healthcare formulations.

White-light driven sterilization based on chlorine-doped cuprous oxide for antibacterial food packaging

Microbial spoilage and pathogen contamination present significant challenges to food quality and safety. Incorporating photodynamic sterilization (PDT) into active packaging films, especially using white light-driven methods, is recognized as one of the most effective strategies to combat microbial contamination and extend shelf-life. Cuprous oxide (Cu2O) shows promise due to its suitable band gap for absorbing visible light, although its photocatalytic effectiveness is hindered by electron-hole recombination. In this study, a chlorine (Cl) doping strategy was investigated to enhance Cu2O’s PDT capabilities under visible light. This approach aimed to improve Cu2O’s band structure for generating reactive oxygen species (ROS) and to enhance charge carrier separation efficiency, thereby inhibiting recombination. The resulting Cl-doped Cu2O (Cl-Cu2O) exhibited enhanced antibacterial activity, which was integrated into a gelatin (Gel) and carboxymethylcellulose (CMC)-based food packaging film, referred to as the GC/Cl-Cu2O film. This innovative film provides a white light-driven active packaging solution designed to extend the shelf life of fruits by suppressing microbial growth. This approach not only addresses food safety concerns but also mitigates economic losses associated with food waste, offering a sustainable solution to enhance the quality and safety of perishable goods.

Novel antifouling paint formulation based on Ca2​Cr2O5​ and CaMnO3​ NPs as a protective pigment

This work focused on the preparation of novel antifouling paint based on Ca2Cr2O5 and CaMnO3 NPs as a safe protective pigment which were replaced with cuprous oxide. Three paint formulations were prepared for comparison, a blank formula without an antifouling agent (F1), a commercial antifouling formula based on 100% cuprous oxide as an antifouling agent (F2), and AF formula based on 75% Ca2Cr2O5 and CaMnO3 NPs and 25% Cu2O. The high performance and durability of the paints based on the prepared pigments were evident from their impact resistance, adhesion, pending, hardness, and chemical resistance, which were compared to the blank formula (F1). The corrosion resistance of the painted films was also investigated using the salt spray test method, and the results were promising compared to the blank and standard formulations. All painted steel plates were exposed to seawater through field tests in the Suez Canal at Port Said for up to 6 months. The results showed that the paints based on F2 and F3a, b enhanced the antifouling activity through six months of exposure. The obtained results demonstrated greater efficiency of the painted steel-based F3a than F1 and F3b, and being comparable to the standard formula (F2).

Enhancement of turbulent heat transfer by using CuO nano-particle and twisted tape

AbstractA computational model is developed to investigate the convective heat transfer properties and the fluid flow characteristics of cupric oxide - water nano-fluid in a horizontal circular pipe aiming to provide insights into optimizing heat transfer in such systems. A twisted tape with varied twist ratios is inserted. This quantitative investigation used five Reynolds number from 4,000 to 12,000 under a uniform heat flux scenario of 25,000 W m−2. All experiments were performed as a single-phase fluid with cupric oxide values of 0, 0.4, 1, and 2% by volume. By reducing the twist ratio and increasing volume concentration, the average heat transfer coefficient of cupric oxide-water nano-fluid was improved. For a twist ratio of 4D, the maximum heat transfer improvement was 228% greater than the plain pipe. The presence of twisted tape with modest step ratios causes the friction factor to grow.

Near-Ideal Copper Oxide Heterostructure Design for Photoelectrochemical Water Splitting.

In recent years, photoelectrochemical (PEC) hydrogen generation through water splitting has gained significant attention as a carbon-free solar-to-energy conversion strategy. Among various materials, copper oxides, specifically cupric oxide (CuO) and cuprous oxide (Cu2O), have been extensively investigated for their suitable band positions and prominent performance, particularly in heterostructures. However, previously reported heterostructures, such as CuO layers on Cu2O, are not ideal configurations in terms of photoelectrical properties. In this study, we introduce the fabrication approach for an ideal heterostructure consisting of Cu2O nanowires on a CuO/Cu2O mixed-phase film, fabricated by a straightforward electrochemical/thermal method. The Cu2O nanowire with Cr layer (CNwC) shows potential for solar energy harvesting due to its suitable band positions and narrow bandgap, enabling enhanced photoabsorption across the entire visible spectrum. A thin chromium (Cr) layer underlying the nanostructure contributes to the formation of the ideal copper oxide heterostructure, acting as an adhesive and protective layer. The Cr layer is oxidized during the fabrication process of the CNwC and supports the hydrogen evolution reaction for water splitting. Moreover, the anodization time critically influences the phase composition, size, and density of the nanowires. Under optimal conditions, collective and slanted Cu2O nanowires can absorb incident light, maximizing both photon absorption and photon-to-energy conversion efficiency.

Ultra‐Low BER Encrypted Communication Based on Self‐Powered Bipolar Photoresponse Ultraviolet Photodetector

AbstractUnderwater visible light communication often faces risks such as susceptibility to external light source interference, signal distortion, and information leakage. The cuprous oxide modified gallium oxide nanorod arrays detector prepared in this study can generate bipolar photocurrents under dual‐wavelength ultraviolet light without external bias voltage. Based on it, the constructed self‐powered ultraviolet ASCII code communication system not only reduce power consumption but also significantly enhance anti‐interference capability. Furthermore, the developed solar‐blind ultraviolet AMI and HDB3 ternary code communication systems can realize non‐visible light secure communication and automatic error correction. Notably, the encrypted communication system assembled using the additive property of bipolar photocurrents can also significantly improve communication security and reliability, whose bit error rate is only 0.26‰. This achievement contributes to technical advancements in underwater channel encryption and provides valuable insights for the further application of encrypted communication coding techniques.

Investigating the effect of Cu underlayer and FTO etching towards photoelectrochemical performance enhancement of Cu2O photoelectrode

Cuprous oxide (Cu2O) exhibits potential as a photoactive material for photoelectrochemical water splitting, owing to its appropriate bandgap, efficient charge carrier separation, and ability to enhance solar-driven hydrogen production. This study investigates the influence of substrate etching, Cu underlayer and Cu2O electrodeposition time, and annealing time on enhancing the photoelectrochemical (PEC) performance. Electrodeposition and thermal oxidation techniques were used to fabricate the Cu2O/Cu/FTOe-A photocathode. It has been observed that FTO etching improves adhesion, light transmission, and efficiency. A Cu underlayer also impacts the PEC performance, wherein an ideal thickness of Cu leads to enhanced PEC performance. This study also focuses on the annealing time that leads to CuO layers and nanowires forming on the Cu2O surface. The structural and chemical changes before and after annealing are confirmed via XRD, XPS, AFM and FESEM analyses. UV–Vis analysis also reveals that the presence of Cu underlayer, FTO etching, and the annealing process affect the electrical properties and light absorption capacities of the Cu2O photoelectrode. Electrochemical impedance analysis (EIS) and Mott-Schottky analysis have provided insights into the enhanced charge transfer properties and band bending in the Cu2O/Cu/FTOe-A, resulting in enhanced PEC performance. Overall, this study provides significant insights into the understanding and enhancement of Cu2O/Cu/FTOe-A photocathodes for potential use in PEC water splitting applications.

Efficient electrocatalytic CO2 reduction to ethylene using cuprous oxide derivatives.

Copper-based materials play a vital role in the electrochemical transformation of CO2 into C2/C2+ compounds. In this study, cross-sectional octahedral Cu2O microcrystals were prepared in situ on carbon paper electrodes via electrochemical deposition. The morphology and integrity of the exposed crystal surface (111) were meticulously controlled by adjusting the deposition potential, time, and temperature. These cross-sectional octahedral Cu2O microcrystals exhibited high electrocatalytic activity for ethylene (C2H4) production through CO2 reduction. In a 0.1M KHCO3 electrolyte, the Faradaic efficiency for C2H4 reached 42.0% at a potential of -1.376V vs. RHE. During continuous electrolysis over 10h, the FE (C2H4) remained stable around 40%. During electrolysis, the fully exposed (111) crystal faces of Cu2O microcrystals are reduced to Cu0, which enhances C-C coupling and could serve as the main active sites for catalyzing the conversion of CO2 to C2H4.

Nitrogen doping of cuprous oxide films: A surface science perspective

Nitrogen doping of Cu2O films grown on Au(111) and Pt(111) supports was explored by a variety of surface-science techniques, including electron-diffraction, X-ray photoelectron-spectroscopy (XPS), scanning tunneling microscopy and photoluminescence spectroscopy (PL). The films were prepared by Cu vapor deposition and high-pressure oxidation at 50 mbar O2. Nitrogen was inserted by adding N2 to the reactive gas or via sputter doping. Only the latter resulted in a clear N1s signal in XPS, compatible with the insertion of N-atoms at O substitutional sites. The N-doping caused an overall degradation of the oxide lattice and suppressed the formation of the (√3×√3)R30° surface reconstruction observed on pristine Cu2O(111). Moreover, the oxide Fermi level shifted from the valence-band top into the band gap, indicative for a reduced p-type conductivity of the sample upon doping. The N-dopants featured low thermal stability and largely desorbed at around 500 K, leaving behind a pronounced 850 nm PL peak due to O vacancy emission. Our findings indicate that the N-atoms initially occupy O substitutional sites but get removed easily at moderate temperature, casting doubts whether N-doping is a suitable pathway to improve the conductance and luminescence behavior of Cu2O.

Unveiling the Dual Role of Oxophilic Cr4+ in Cr-Cu2O Nanosheet Arrays for Enhanced Nitrate Electroreduction to Ammonia.

Cuprous oxide (Cu2O)-based catalysts present a promising activity for the electrochemical nitrate (NO3-) reduction to ammonia (eNO3RA), but the electrochemical instability of Cu+ species may lead to an unsatisfactory durability, hindering the exploration of the structure-performance relationship. Herein, we propose an efficient strategy to stabilize Cu+ through the incorporation of Cr4+ into the Cu2O matrix to construct a Cr4+-O-Cu+ network structure. In situ and quasi-in situ characterizations reveal that the Cu+ species are well maintained via the strong Cr4+-O-Cu+ interaction that inhibits the leaching of lattice oxygen. Importantly, in situ generated Cr3+-O-Cu+ from Cr4+-O-Cu+ is identified as a dual-active site for eNO3RA, wherein the Cu+ sites are responsible for the activation of N-containing intermediates, while the assisting Cr3+ centers serve as the electron-proton mediators for rapid water dissociation. Theoretical investigations further demonstrated that the metastable state Cr3+-O-Cu+ favors the conversion from the endoergic hydrogenation of the key *ON intermediate to an exoergic reaction in an ONH pathway, and facilitates the subsequent NH3 desorption with a low energy barrier. The superior eNO3RA with a maximum 91.6% Faradaic efficiency could also be coupled with anodic sulfion oxidation to achieve concurrent NH3 production and sulfur recovery with reduced energy input.

Unveiling the Dual Role of Oxophilic Cr4+ in Cr‐Cu2O Nanosheet Arrays for Enhanced Nitrate Electroreduction to Ammonia

Cuprous oxide (Cu2O)‐based catalysts present a promising activity for the electrochemical nitrate (NO3‐) reduction to ammonia (eNO3RA), but the electrochemical instability of Cu+ species may lead to an unsatisfactory durability, hindering the exploration of the structure‐performance relationship. Herein, we propose an efficient strategy to stabilize Cu+ through the incorporation of Cr4+ into the Cu2O matrix to construct a Cr4+‐O‐Cu+ network structure. In situ and quasi‐in situ characterizations reveal that the Cu+ species are well maintained via the strong Cr4+‐O‐Cu+ interaction that inhibits the leaching of lattice oxygen. Importantly, in situ generated Cr3+‐O‐Cu+ from Cr4+‐O‐Cu+ is identified as a dual‐active site for eNO3RA, wherein the Cu+ sites are responsible for the activation of N‐containing intermediates, while the assisting Cr3+ centers serve as the electron‐proton mediators for rapid water dissociation. Theoretical investigations further demonstrated that the metastable state Cr3+‐O‐Cu+ favors the conversion from the endoergic hydrogenation of the key *ON intermediate to an exoergic reaction in an ONH pathway, and facilitates the subsequent NH3 desorption with a low energy barrier. The superior eNO3RA with a maximum 91.6% Faradaic efficiency could also be coupled with anodic sulfion oxidation to achieve concurrent NH3 production and sulfur recovery with reduced energy input.

Reaction Dynamics between Formamidinium Lead Iodide and Copper Oxide.

Copper oxide (CuOx) has been announced as a very promising hole-transporting layer for perovskite solar cells. However, in our previous work, we have shown that once a formamidinium lead triiodide (FAPI) perovskite is spin-coated on a spray-coated cuprous oxide (Cu2O) substrate, the Cu2O diffuses into and reacts with the FAPI film. In order to verify if the degradation products are related to the oxidation state of CuOx and/or its preparation method, in this work, we first prepared CuOx films by thermal oxidation at temperatures ranging from 120 to 300 °C. While increasing the process temperature, a transformation from copper I (Cu2O) to copper II (CuO) oxidation states was observed. For both oxidation states of copper, FAPI perovskite degradation was found; however, some alterations in the reaction products were noticed. In contrast to our expectations, the introduction of an ultrathin plasma-enhanced atomic layer deposited Al2O3 layer in between both films only partially blocked the CuOx migration into the FAPI film. It can be concluded that regardless of the chemical composition and/or preparation method of CuOx, the overlayered FAPI film gets decomposed. In order to use CuOx as a hole-transporting layer in solar cells, new strategies must be developed to limit these unwanted chemical reactions.

In situ generation of cuprous oxide in metal-organic framework for significantly enhanced room-temperature ammonia sensing: Synergy enabling excellent sensitivity and selectivity

Development of effective strategies to improve the response sensitivity of metal-organic frameworks (MOFs) to target gases is imperative to further enhancing their application potential in gas sensing. In this work, series of CuHHTP/Cu2O (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) composites are successfully constructed by in-situ electrochemical reduction treatment of CuHHTP, and the changing trend of first increasing and then decreasing with increase of CuHHTP electrochemical reduction degree for their sensitivity to NH3 detection is revealed. When the average size of Cu2O nanoparticles generated in CuHHTP is 3.6 nm, the corresponding CuHHTP/Cu2O-A composite exhibits the best NH3 sensing performance compared to pristine CuHHTP, including significantly enhanced response sensitivity, ultralow experimental detection limit of 10 ppb, superior selectivity, good reproducibility, and excellent response stability even after placed for 90 days. More impressively, thanks to integration and synergy of the uniformly-dispersed small-sized Cu2O nanoparticles with significantly enhanced adsorption activity and capacity for NH3, the released large amount of uncoordinated hydroxyl groups that can interact with NH3, as well as the active sites of the CuHHTP substrate itself, the 10 ppb experimental detection limit for the CuHHTP/Cu2O-A-based sensors is not only the lowest one reported in the past 10 years for NH3 sensors based on copper-containing MOF and oxide materials, but also superior to that of 0.1–1 ppm for the existing commercial NH3 sensors. This work opens the avenue for design and development of novel MOF-based sensing materials.

Rydberg excitons in cuprous oxide: A two-particle system with classical chaos.

When an electron in a semiconductor gets excited to the conduction band, the missing electron can be viewed as a positively charged particle, the hole. Due to the Coulomb interaction, electrons and holes can form a hydrogen-like bound state called the exciton. For cuprous oxide, a Rydberg series up to high principle quantum numbers has been observed by Kazimierczuk et al. [Nature 514, 343 (2014)] with the extension of excitons up to the μm-range. In this region, the correspondence principle should hold and quantum mechanics turn into classical dynamics. Due to the complex valence band structure of Cu2O, classical dynamics deviates from a purely hydrogen-like behavior. The uppermost valence band in cuprous oxide splits into various bands resulting in yellow and green exciton series. Since the system exhibits no spherical symmetry, the angular momentum is not conserved. Thus, the classical dynamics becomes non-integrable, resulting in the possibility of chaotic motion. Here, we investigate the classical dynamics of the yellow and green exciton series in cuprous oxide for two-dimensional orbits in the symmetry planes as well as fully three-dimensional orbits. Our analysis reveals substantial differences between the dynamics of the yellow and green exciton series. While it is mostly regular for the yellow series, large regions in phase space with classical chaos do exist for the green exciton series.

Tuning Electrochemical Performance of Polymer Electrolyte Films through Metal Oxide Incorporation

AbstractWith the escalating global energy demand, the exploration of alternative, easily accessible, and cost‐effective energy sources has become imperative. The diminishing reserves of conventional energy resources underscore the urgency to transition towards renewable energy. Solid polymer electrolytes (SPEs) have gained prominence for energy storage electrochemical devices due to their high flexibility and favorable electrode–electrolyte interactions. This study focuses on synthesizing nano cuprous oxide (CuO) semiconductors via the precipitation method. The prepared CuO nanofiller is homogeneously dispersed into a polymer electrolyte solution. Utilizing the solution cast method, free‐standing polymer electrolyte films are fabricated, exhibiting commendable mechanical stability. Polyvinyl alcohol (PVA) serves as the host material, with potassium iodide (KI) salt, forming the basis for the polymer electrolyte. The resultant electrolyte films underwent comprehensive characterization for their electrical and optical properties. The investigation aims to identify the optimal composition of the electrolyte film with superior conductivity. The selected composition will be employed in the fabrication of various electrochemical devices, demonstrating the potential for enhanced energy storage applications. This work not only contributes to the synthesis of advanced solid polymer electrolyte films but also paves the way for the development of efficient and sustainable energy storage solutions in the realm of renewable energy technologies.

The surface chemistry of cuprous oxide

The chemical and electronic properties of copper combined with its large natural abundance lend this material to impact a wide range of technological applications, including heterogeneous catalysis. The reactivity of copper in its Cu1+oxidation state makes this specific configuration relevant in various chemical reactions, but the facile redox properties of copper make the isolation of individual states for fundamental studies difficult. Here we review three Cu2O model systems used to study the interaction of Cu1+ with small molecules making use of surface science techniques: Cu2O/Cu(111), thin polycrystalline Cu2O films on Cu foil, and bulk Cu2O crystals. Advantages and disadvantages of each system are discussed and exemplified through case studies of chemical adsorption and reactivity studies.

Effect of surface corrosion on the zeta potential of copper in acidic solutions

The comprehensive investigation was conducted to analyze the corrosion behavior and surface potential of pure copper surfaces in various acidic solutions. We carried out Zeta potential measurement, electrochemical measurement and in situ Raman spectroscopy to investigate the corrosion process and surface potential of copper in acidic solutions with different pH. It was found that the variation in zeta potential with pH corresponds to the corrosion behavior of copper during this process. In 1mmol / L aqueous chloride media, when the pH is greater than 3.5, unalloyed copper is oxidized to monovalent copper. At this stage, as the pH decreases, the zeta potential gradually increases. When the pH reaches 3.5, the Zeta potential reaches the highest, and the rate of cuprous oxide formation reaches the maximum. When the pH continues decrease, unalloyed copper begins to be oxidized to divalent copper, and the zeta potential will also decrease, the surface charge state shifts to the positive direction. Furthermore, our experimental findings are complemented by Density Functional Theory (DFT) calculations.

Enhanced charge separation at the interface of Cu2O/CuSCN composite thin films synthesized by electrodeposition technique

This study focuses on the synthesis and characterization of hole transport layers (HTLs) for solar cells, par- ticularly copper(I) thiocyanate (CuSCN) and cuprous oxide (Cu2O), synthesized via electrodeposition tech- niques. CuSCN and Cu2O offer promising properties for efficient charge transport in photovoltaic devices. The synthesis processes involve precise control of deposition parameters to achieve desired film morpholo- gies and properties. Characterization techniques including scanning electron microscopy (SEM), atomic force microscopy (AFM), and ultraviolet-visible (UV-Vis) spectroscopy provide insights into film morphology and optical properties. Optimization of synthesis parameters for Cu2O films is explored to enhance their electrical properties. Photoelectric response measurements indicate improved charge separation at the interface of Cu2O/CuSCN composite films. These findings can contribute to the advancement of solar cell technology. Furthermore, the study extends its exploration to the fabrication of Cu2O by electrodeposition at different pH levels. SEM and X-ray diffraction (XRD) analyses reveal the impact of deposition parameters on film mor- phology and crystal structure, providing valuable insights for tailored synthesis approaches. Overall, this comprehensive study not only advances the understanding of HTL materials synthesis and optimization but also provides valuable guidance for the development of high-efficiency and stable solar cell devices.

500 μm heavy micro-alloyed Cu wire for IGBT application: The study on microstructure characteristics, electrical fatigue fracture mechanism and bonding reliability

In this study, we introduced trace amounts of silver and nickel into 500 μm diameter copper wires to form micro-alloyed copper wires used in insulated gate bipolar transistors (IGBT). The addition of silver and nickel enhanced the mechanical properties of the conductors and suppressed the work hardening effect, significantly improving the power cyclic lifetime. Additionally, this study conducted chlorination and high-temperature oxidation test to compare the application characteristics of the heavy micro-alloyed copper wires with pure copper wires, through tensile and bending test, as well as electrical property comparisons. Finally, Cu50Ni (50 ppm Ni) wires were selected and nickel ceramic substrates for wire bonding to evaluate module electrical properties and bonding reliability.In the chloride test, there was no significant pitting corrosion observed in copper wire, and the micro-alloyed copper wire outperformed the pure copper wires in terms of bending lifetime and power cycling performance. In the high-temperature oxidation test, an oxide layer of cuprous oxide formed on the surface of all wires. The pure copper wire exhibited a significant increase in resistance. Notably, the micro-alloyed copper wires had better resistance to oxidation. Regarding wire bonding, the use of Cu50Ni wires and nickel ceramic substrates reduced the diffusion rate of nickel atoms from the substrate to the copper wire, forming a thinner alloy diffusion layer. This prevented electrical degradation and achieved high bonding reliability, especially under higher bonding forces. These findings confirm that micro-alloyed copper wires are suitable for high-power applications.