Copper Nanowire Networks Research Articles

Smart Green Cotton Textiles with Hierarchically Responsive Conductive Network for Personal Healthcare and Thermal Management.

Whereas cotton as an abundant natural cellulose has been widely used for sustainable and skin-friendly textiles and clothes, developing cotton fabrics with smart functions that could respond to various stimuli is still eagerly desired while remaining a great challenge. Herein, smart multiresponsive cotton fabric with hierarchically copper nanowire interwoven MXene conductive networks that are seamlessly assembled along a 3D woven fabric template for efficient personal healthcare and thermal comfort regulation is successfully developed. The robust hierarchically interwoven conductive network was "glued" and protected by organic conductive polymer poly(3,4-ethylenedioxythiophene) along a 3D interconnected fabric template to enhance interfacial adherent and environmental stability. Benefiting from the robust multiresponsive hierarchically interwoven conductive network, smart cotton fabric exhibits real-time response to various external stimuli (light/electrical/heat/temperature/stress), and the details of human activities can be accurately recognized and monitored. Furthermore, the porous structure of 3D smart fabric induced strong capillary force and confinement to phase change materials PEG, which exhibits a wide range of phase transition temperatures for efficient thermal comfort regulation. After further encapsulation with transparent fluorosilicone resin, the smart cotton fabric exhibits excellent self-cleaning performance with water/oil repellent. The smart multiresponsive cotton fabrics hold great promise in next-generation wearable systems for efficient personal healthcare and thermal management.

Fine-Tune the Electronic Structure of Copper Nanowire Networks by Heteroatom Doping Toward Enhanced Fenton-like Reaction

To fine-tune the configuration of electrons around metal centers is critical to enhancing the activation of peroxymonosulfate (PMS) for organic decontamination in a manner similar to the Fenton-like reaction. Herein, we systematically explored the inclusion of different heteroatoms to manipulate the electronic configuration of copper nanowire (CuNW) networks toward PMS activation. Both experimental results and theoretical simulations unveiled that doping the CuNW with boron (B) to generate CuNW-B adjusted the d orbital of CuNW, optimized the electronic density of Cu active sites and endowed a proper adsorption energy of PMS, which provided the most active oxidation capacity of the materials studied. Conversely, doping with phosphorus (P) to generate CuNW-P caused evident performance decay in terms of the activation of PMS, as strong adsorption energy hindered the effective desorption of key intermediates. Accordingly, the CuNW-B boosts the Fenton-like reaction and is nearly triple and twice as effectively at degrading bisphenol A (92.5%) as CuNW-P (36.0%) and CuNW (50.5%). Thus, it was reasonably hypothesized that electronic reconstruction played an important role in improving the Fenton-like reaction. During this process, an applied potential (AP) facilitated the catalytic process by reducing Cu2+ to Cu+, which was followed by the formation of primary active species (Cu3+). Additionally, the use of a recirculating fluid flow in the reactor provided convective mass transfer, which led to more charge transfer to the structure of electrode relative to a conventional diffusion-limited batch reactor. Moreover, tests in a variety of challenging conditions demonstrated the robustness and stability of the combined CuNW-B/PMS/AP approach. This study provides an approach to finely control the electronic structure of Cu sites and is expected to guide the design of advanced Fenton-like catalysts, which could further provide a promising technology for the treatment of actual organic wastewater in a sustainable manner.

Copper Nanowire Networks: An Effective Electrochemical Peroxymonosulfate Activator toward Nitrogenous Pollutant Abatement.

Herein, we developed an electrochemical filtration system for effective and selective abatement of nitrogenous organic pollutants via peroxymonosulfate (PMS) activation. Highly conductive and porous copper nanowire (CuNW) networks were constructed to serve simultaneously as catalyst, electrode, and filtration media. In one demonstration of the CuNW network's capability, a single pass through a CuNW filter (τ < 2 s) degraded 94.8% of sulfamethoxazole (SMX) at an applied potential of -0.4 V vs SHE. The exposed {111} crystal plane of CuNW triggered atomic hydrogen (H*) generation on sites, which contributed to effective PMS reduction. Meanwhile, with the involvement of SMX, a Cu-N bond was formed by the interactions between the -NH2 group of SMX and the Cu sites of CuNW, accompanied by the redox cycling of Cu2+/Cu+, which was facilitated by the applied potential. The different charges of the active Cu sites made it easier to withdraw electrons and promote PMS oxidation. Theoretical calculations and experimental results were combined to suggest a mechanism for pollution abatement with CuNW networks. The results showed that system efficacy for the degradation of a wide array of nitrogenous pollutants was robust across a broad range of solution pH and complex aqueous matrices. The flow-through operation of the CuNW filter outperformed conventional batch electrochemistry due to convection-enhanced mass transport. This study provides a new strategy for environmental remediation by integrating state-of-the-art material science, advanced oxidation processes, and microfiltration technology.

Self-assembled Growth of SnO2 Nanoshells on Copper Nanowires for Stable and Transparent Conductors

Despite a century of research, the inability to design flexible transparent electrodes with low cost and high stability has been the greatest obstacle in realizing flexible electronics. Herein, we report the growth of self-assembled SnO2 nanoshells on thin copper nanowire (Cu NW) networks using a simple and effective solution method. In addition, the SnO2–Cu NW flexible films exhibit an extremely low sheet resistance of ∼13.6 Ω/sq, with ∼83.5% optical transparency. In harsh environments (such as strong oxidation, heat, and humidity conditions), the films demonstrate excellent resistance stability, which can compete with the resistance stability of noble silver nanowire films. Particularly, the films are robust and able to withstand a high temperature of 210 °C without any deterioration of performance. Employing the outstanding stability of SnO2–Cu NWs, we also demonstrate the macroscopic use of a transparent conductor in a flexible transparent heater.

Cu Nanowire Networks with Well-Defined Geometrical Parameters for Catalytic Electrochemical CO2 Reduction

Three-dimensional, highly interconnected copper nanowire networks are designed and fabricated by electrodeposition in etched ion track polymer templates with interconnected nanochannels and subsequently applied as a catalyst for the electrochemical CO2 reduction toward hydrocarbons and alcohols in an aqueous electrolyte. The specific surface area expressed by the nanowire networks can be adjusted by tailoring the wire length, wire diameter, and nanowire number density to values between 70 cm2 and 300 cm2 per cm2 geometrical sample area. The conversion efficiency and selectivity of CO2 reduction toward liquid- and gas-phase products are studied as a function of the applied potential. Before and after the CO2 reduction reaction, the nanowire networks are characterized by scanning and transmission electron microscopy and by X-ray diffraction, evidencing their stability during CO2 reduction in a potential region between −0.5 V and −0.93 V versus RHE.

High Surface Area 3D Copper Nanowire Networks for High-Throughput Electrochemical CO2 Reduction

An attractive solution towards net-zero carbon emission is the electrocatalytic CO2 reduction with its ability to convert the greenhouse gas CO2 with renewable electricity and appropriate catalytic materials to useful chemicals and fuels to store energy. Depending on the number of electrons transferred a variety of oxygenates and hydrocarbons can be obtained. Among used catalytic materials, such as metals, alloys or composites, copper has shown the unique property to electrocatalytically convert CO2 into a wide variety of valuable C2+ products such as ethylene or alcohols.Apart from the high potential to reshape our carbon economy the electrocatalytic CO2 reduction is still in its early development stage compared to the more mature water electrolysis, with high-throughput operation at practical current densities as well as long-term stability of the catalysts being only scarcely demonstrated. Additionally, selectivity towards high-value (beyond C1) products using copper catalysts has proven to be challenging and many research efforts are directed towards improving product selectivity. For this purpose, mainly nanostructured porous Cu electrodes either based on randomly ordered nanoparticles loaded on porous (carbon-based) supports or low-surface area metal foams, meshes or felts with high porosity are commonly used. While the former electrode architecture typically shows poor long-term stability with often weak adhesion between the nanoparticles and the porous support, the latter electrodes have a low electrochemical surface area and hence are not suitable for high-throughput CO2 reduction at high current densities.In this work we present novel high-surface area porous copper electrodes, so-called copper nanomeshes, that are regular 3D-networks of interconnected Cu nanowires. These unique few µm-thin electrodes show a large surface area enhancement (compared to planar Cu) by a factor of ~80, while providing a high porosity of ~70% together with sufficient mechanical stability, an important aspect towards their practical implementation in electrocatalytic flow cells. Cu nanomesh electrodes with a thickness of 4µm were fabricated through electrochemically plating in 3D-porous anodic aluminum oxide templates and show a mixed surface texture of (111), (100) and (110) Cu. We demonstrate the high potential toward high-throughput CO2 electrolysis of these novel electrodes in comparison to planar copper electrodes in various CO2-containing electrolyte solutions. The CO2 reduction product analysis showed a significant difference in selectivity between planar (polycrystalline or with preferential 111 or 200 texture) and the polycrystalline Cu nanomesh electrodes with CO or C2H4 as major reduction products depending on the potential applied. The beneficial effect of the high electrochemical surface area was demonstrated by a significant increase in the current density on the nanostructured Cu electrodes. Additionally, we characterized the copper nanomesh electrodes before, during and after CO2 reduction with complementary techniques to gain insights on the reaction mechanism and on the electrode stability. Figure 1

Epidermis-Inspired Wearable Piezoresistive Pressure Sensors Using Reduced Graphene Oxide Self-Wrapped Copper Nanowire Networks.

Wearable piezoresistive sensors are being developed as electronic skins (E-skin) for broad applications in human physiological monitoring and soft robotics. Tactile sensors with sufficient sensitivities, durability, and large dynamic ranges are required to replicate this critical component of the somatosensory system. Multiple micro/nanostructures, materials, and sensing modalities have been reported to address this need. However, a trade-off arises between device performance and device complexity. Inspired by the microstructure of the spinosum at the dermo epidermal junction in skin, a low-cost, scalable, and high-performance piezoresistive sensor is developed with high sensitivity (0.144kPa-1 ), extensive sensing range ( 0.1-15 kPa), fast response time (less than 150ms), and excellent long-term stability (over 1000 cycles). Furthermore, the piezoresistive functionality of the device is realized via a flexible transparent electrode (FTE) using a highly stable reduced graphene oxide self-wrapped copper nanowire network. The developed nanowire-based spinosum microstructured FTEs are amenable to wearable electronics applications.

All-Solution-Processed, Oxidation-Resistant Copper Nanowire Networks for Optoelectronic Applications with Year-Long Stability.

Copper nanowires (Cu NWs) hold promise as they possess equivalent intrinsic electrical conductivity and optical transparency to silver nanowires (Ag NWs) and cost substantially less. However, poor resistance to oxidation is the historical challenge that has prevented the large-scale industrial utilization of Cu NWs. Here, we use benzotriazole (BTA), an organic corrosion inhibitor, to passivate Cu NW networks. The stability of BTA-passivated networks under various environmental conditions was monitored and compared to that of bare Cu NW control samples. BTA passivation greatly enhanced the stability of networks without deteriorating their optoelectronic performance. Moreover, to demonstrate their potential, BTA-passivated networks were successfully utilized in the fabrication of a flexible capacitive tactile sensor. This passivation strategy has a strong potential to pave the way for large-scale utilization of Cu NW networks in optoelectronic devices.

Synchronously improved reliability, figure of merit and adhesion of flexible copper nanowire networks by chitosan transition

Copper nanowires (CuNWs) are remarkable components that can replace indium tin oxide as transparent electrodes due to their low cost, high conductivity and acceptable transmittance. However, a common coating method can cause poor electrical, optical and adhesive properties because of the creation of loosely connected junctions. In addition, the unsatisfactory thermal and environmental stabilities limit the practical applications. These problems should be overcome in CuNW-based films for reliable transparent electrodes through material and engineering approaches. In this work, a novel transparent composite electrode composed of chitosan and CuNWs on a flexible polyethylene terephthalate (PET) substrate, with synchronously strengthened adhesion, as well as heightened transmittance, reduced resistivity, improved flexibility, enhanced thermal stability and increased environmental stability, was prepared without vacuum processing and high-temperature annealing. The effects of the number of CuNW network layers and chitosan concentration on the performance of chitosan/CuNW composite transparent electrodes were studied. The resulting electrodes exhibitan excellent conductivity (sheet resistance: 15.6 Ω sq−1) and a superior optical transmittance (∼87%) at 550 nm. Calculation of the figure of merit displays a high value of 168, which is the highest among all the reported CuNW-based transparent electrodes. Meanwhile, the sheet resistance did not show great change after 10 tape tests and 10 000 bending cycles, suggesting good adhesion to the PET substrate and outstanding mechanical flexibility. Moreover, the composite transparent electrodes show good stability to resist long-term storage and temperature variation in thermal environment.

Cu Nanowires Passivated with Hexagonal Boron Nitride: An Ultrastable, Selectively Transparent Conductor.

The copper nanowire (Cu NW) network is considered a promising alternative to indium tin oxide as transparent conductors for advanced optoelectronic devices. However, the fast degradation of copper in ambient conditions largely overshadows its practical applications. Here we demonstrate a facile method for epitaxial growth of hexagonal boron nitride (h-BN) of a few atomic layers on interlaced Cu NWs by low-pressure chemical vapor deposition, which exhibit excellent thermal and chemical stability under high temperature (900 °C in vacuum), high humidity (95% RH), and strong base/oxidizer solution (NaOH/H2O2). Meanwhile, their optical and electrical performances remain similar to those of the original Cu NWs (e.g., high optical transmittance (∼93%) and high conductivity (60.9 Ω/□)). A smart privacy glass is successfully fabricated based on a Cu@h-BN NW network and liquid crytal, which could rapidly control the visibility from transparent to opaque (0.26 s) and, at the same time, strongly block the mid-infrared light for energy saving by screening radiative heat. This precise engineering of epitaxial Cu@h-BN core-shell nanostructure offers broad applications in high-performance electronic and optoelectronic devices.

Superstable copper nanowire network electrodes by single-crystal graphene covering and their applications in flexible nanogenerator and light-emitting diode

Copper nanowires (CuNWs), with excellent electronic properties and high cost-effectiveness, have tremendous potential in the field of transparent conductive electrodes for flexible electronics, large touch screen display and triboelectric energy harvesters, while their vulnerability to oxidation in air has impeded possible practical applications. Fortunately, it has been recognized that graphene encapsulation of CuNWs is capable of protecting CuNWs. However, neither self-assembled reduced graphene oxide nor chemical vapor deposition-grown polycrystalline graphene coatings can guarantee full protection to CuNWs, due to their ubiquitous voids, grain boundaries and wrinkles that allow water and oxygen molecules to pass through and result in the accelerated electrochemical corrosion at the graphene-copper interface, especially under folding conditions. Herein, we demonstrate a sandwich-structured single-crystal graphene/copper nanowire network/UV-curable resin (SCG/CuNW/UVR) composite film with ultrahigh electronic performance stability. The SCG/CuNW/UVR electrode exhibits a good optical and electrical performance (~19 Ω sq−1 under 84.3% transmittance), excellent mechanical robust and remarkably high oxidation resistance (ΔR/R0 < 0.2 within 180 days), in sharp contrast with the bare CuNWs (ΔR/R0 > 1 after 1 day) and polycrystalline graphene-covered CuNWs counterparts (ΔR/R0 > 1 after 7 days). Furthermore, the SCG/CuNW/UVR electrodes can replace indium tin oxide (ITO) electrodes to construct the triboelectric nanogenerators (TENG) and quantum dot light emitting diodes (QLED), comparable to the flexible commercial ITO counterparts. The fabrication of such high-performance SCG/CuNW/UVR electrode is facile to be scaled-up with low cost, providing the feasibility for industrial applications of flexible ITO-free electronic and optoelectronic devices.

Fast and simple fabrication of flexible and transparent electrode based on patterned copper nanowires by mechanical lithography transfer

Although copper nanowire is potentially promising candidate for replacing indium tin oxide, critical issues including small-scale and a complex and expensive fabrication and patterning have to be addressed before widely applying copper nanowire networks in flexible devices. Here, we demonstrate a fast and scalable fabrication and a patterning method for copper nanowires (Cu NWs)-based flexible transparent electrodes. By adding ethanol-dipping step together with acid treatment during the cleaning process, Cu NWs electrodes on glass substrates exhibited high conductivity and the film former was completely removed. After a simple one-step transfer and patterning, the patterned Cu NWs channels strongly adher to the flexible substrates, resulting in excellent properties of the electrodes. Finally, the patterned flexible electrodes were used to make a 4 × 2 touch screen to confirm our method to be useful in commercial manufacturing.

Core/shell copper nanowire networks for transparent thin film heaters

Copper nanowires (Cu NWs) appear as the strongest alternative to silver nanowires (Ag NWs) in transparent conductors. Cu NWs; however, are more prone to oxidation compared to Ag NWs even at room temperature. This problem becomes more severe when Cu NWs are used as transparent thin film heaters (TTFHs). In this work, we have utilized ALD deposited zinc oxide (ZnO) shell layers, and provide a comparison with typically used aluminum oxide (Al2O3) shell layers to improve the TTFH performance. While Cu NW network TTFHs barely withstood temperatures around 100 °C, critical thickness of ALD deposited Al2O3 and ZnO layers were determined to find out TTFH limits. Maximum stable and reproducible temperatures of 273 °C and 204 °C were obtained for Al2O3 and ZnO deposited Cu NW network TTFHs, respectively. An extensive parametric study on the NW density and oxide type in conjunction with the electrical conductivity and optical transmittance was conducted. A remarkably high heating rate of 14 °C s−1 was obtained from the fabricated core/shell networks with improved oxidation stability under ambient and high humidity conditions. Finally, these high performance core/shell Cu NW network TTFHs were utilized as efficient defrosters.

Study on the oxidation of copper nanowire network electrodes for skin mountable flexible, stretchable and wearable electronics applications

Copper nanowires (Cu NWs) are suitable material as an electrode for flexible, stretchable and wearable devices due to their excellent mechanical properties, high transparency, good conductivity, and low cost, but oxidation problem limits their practical use and application. In order to use Cu NWs as an electrode for advanced flexible, stretchable and wearable devices attached directly to the skin, the influence of the body temperature on the oxidation of Cu NWs needs to be investigated. In this paper, the oxidation behavior of Cu NWs at high temperature (more than 80 °C) as well as body temperature is studied which has been remained largely questionable to date, and an effective encapsulation method is proposed to prevent the oxidation of Cu NWs electrode in the range of body temperatures.

Dictating anisotropic electric conductivity of a transparent copper nanowire coating by the surface structure of wood.

In this article, a robust, air-stable, flexible and transparent copper (Cu) nanowire (NW) network coating on the surface of the wood is presented, based on a fusion welding of the Cu NWs by photonic curing. Thereby, an anisotropic conductivity can be achieved, which is originating from the structural organization of the wood body and its surface. Furthermore, the Cu NWs are protected from oxidation or wear by a commercially available paraffin wax-polyolefin, which also results in surface water repellency. The developed processing steps present a facile and flexible routine for applying Cu NW transparent conductors to abundant biomaterials and solve current manufacturing obstacles for corrosion-resistant circuits while keeping the natural appearance of the substrate. It may open a venue for more extensive utilization of materials from renewable resources such as wood for electronic devices in smart buildings or mobility applications.

Three-Dimensional Superhydrophobic Nanowire Networks for Enhancing Condensation Heat Transfer

Summary Spontaneous droplet jumping on nanostructured surfaces can potentially enhance condensation heat transfer by accelerating droplet removal. However, uncontrolled nucleation in the micro-defects of nanostructured superhydrophobic surfaces could lead to the formation of large pinned droplets, which greatly degrades the performance. Here, we experimentally demonstrate for the first time stable and efficient jumping droplet condensation on a superhydrophobic surface with three-dimensional (3D) copper nanowire networks. Due to the formation of interconnections among nanowires, the micro-defects are eliminated while the spacing between nanowires is reduced, which results in the formation of highly mobile droplets. By preventing flooding on 3D nanowire networks, we experimentally demonstrate a 100% higher heat flux compared with that on the state-of-the-art hydrophobic surface over a wide range of subcooling (up to 28 K). The remarkable water repellency of 3D nanowire networks can be applied to a broad range of water-harvesting and phase-change heat transfer applications.

Synthesis of carbon nanotube (CNT)-entangled CuO nanotube networks via CNT-catalytic growth and in situ thermal oxidation as additive-free anodes for lithium ion batteries

We demonstrated the utility of carbon nanotubes (CNTs) as a catalyst and conductive agent to synthesize CNT-entangled copper nanowire (CuNW-CNT) networks within a melted mixture of hexadecylamine and cetyltrimethy ammounium bromide. The CuNW-CNT networks were further in situ thermally oxidized into CuO nanotube-CNT (CuONT-CNT) with the high retention of network structure. The binder- and conducting-additive-free anodes constructed using the CuONT-CNT networks exhibited high performance, such as high capability (557.7 mAh g−1 at 0.2 °C after 200 cycles), high Coulombic efficiency (near 100%), good rate performance (385.5 mAh g−1 at 5 °C and 310.3 mAh g−1 at 10 °C), and long cycling life.

Large-Scale Stretchable Semiembedded Copper Nanowire Transparent Conductive Films by an Electrospinning Template.

With recent emergence of wearable electronic devices, flexible and stretchable transparent electrodes are the core components to realize innovative devices. The copper nanowire (CuNW) network is commonly chosen because of its high conductivity and transparency. However, the junction resistances and low aspect ratios still limit its further stretchable performance. Herein, a large-scale stretchable semiembedded CuNW transparent conductive film (TCF) was fabricated by electrolessly depositing Cu on the electrospun poly(4-vinylpyridine) polymer template semiembedded in polydimethylsiloxane. Compared with traditional CuNWs, which are as-coated on the flexible substrate, the semiembedded CuNW TCFs showed low sheet resistance (15.6 Ω·sq-1 at ∼82% transmittance) as well as outstanding stretchability and mechanical stability. The light-emitting diode connected the stretchable semiembedded CuNW TCFs in the electric circuit still lighted up even after stretching with 25% strain. Moreover, this semiembedded CuNW TCF was successfully applied in polymer solar cells as a stretchable conductive electrode, which yielded a power conversion efficiency of 4.6% with 0.1 cm2 effective area. The large-scale stretchable CuNW TCFs show potential for the development of wearable electronic devices.

Copper Nanowire‐Filled Soft Elastomer Composites for Applications as Thermal Interface Materials

Efficient heat dissipation is a critical requirement for sustained performance and failure prevention of microelectronic components. Thermal interface materials are used to fill the voids at the solid interface between the device and the heat sink to create a thermally conducting pathway for heat dissipation. This work reports flexible elastomer composite embedded copper nanowires with high aspect ratios (2500–5000), leading to a thermal percolation network at very low volume filler loading fractions of ≈0.009Φ. In order to achieve a high thermal conductivity at ultralow filler fractions, the copper nanowires are freeze‐casted into a monolithic sponge, to create an interconnected network. The composites formed by subsequently embedding the nanowire sponge in elastomer matrix exhibit a thermal conductivity of 3.1 ± 0.2 W mK−1, a 19‐fold enhancement over the pristine matrix, in a temperature range between 20 and 80 °C. The effect of thermal contact resistance at nanowire junctions is substantially reduced by in situ microwave welding of the nanowires. The use of Ecoflex, an ultrasoft silicone elastomer as the matrix, along with very low filler loadings of copper nanowire networks, keeps the elastic modulus &lt;250 kPa, retaining the high compliance of the composites.

Control of copper nanowire network properties and application to transparent conducting layer in LED

We report the control of structural, optical, and electrical properties of solution processed copper (Cu) nanowires (NWs) by varying the capping agent concentration and demonstrating the enhanced light extraction of GaN-based light-emitting diodes (LEDs) using Cu NWs. Cu NWs were prepared by a simple solvothermal method, and the capping agent concentration effects on the growth of Cu NWs were systematically investigated. The different diameters of Cu NWs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible absorption, and conductivity measurements. All characterization results showed high aspect ratio nanowires with efficient transmittance and conductivity properties. When the synthesized Cu NWs were adopted as a transparent conducting layer, the electroluminescence intensity was improved by its spreading effects. This work will elucidate the influence of capping agents on the physical properties, optical properties, and electrical conductivity of Cu NWs for use as a transparent conductor in optoelectronic devices.