Nanowire Networks Research Articles

Large scale fabrication of recyclable and multifunctional sandwich-structured electromagnetic interference shielding films based on waste Nylon-6 silk

Modern wearable electronics are being miniaturized with high integration and frequency, leading to excess electromagnetic radiation, heat storage, and fire risk. Besides overcoming these safety issues, realizing large-scale, low-cost and recyclable preparation of multifunctional films are urgently required for practical applications of electromagnetic interference (EMI) shielding. Herein, sandwich-structured films have been prepared using commercial nylon mesh (CNM) with a waste nylon-6 silk/ammonium polyphosphate (PA6/APP) porous flame-retardant outer layer and inner conductive ultra-long silver nanowires (AgNWs) network. Only 0.2 mg/cm2 of the conductive inner layer endows the films with excellent EMI shielding performance (53.7 dB), thermal diffusivity (5.206 ± 0.087 mm2/s) and antibacterial properties. In addition, the unique honeycomb structure of the PA6/APP outer layer produced during water bath treatment endows the films with superior printability. And such modified porous outer layer of the sandwich-structured films realizes a V0 rating during the UL-94 test. Even when these films are scrapped, they can still be recycled and reused. In summary, the methods described herein can be extended to realize the large-scale production of sandwich-structured films.

Enhancing the memristive effects in SnO2 nanowire networks

We present a study of SnO2 nanowire network acting as a resistive memory device. Charge transport features in these devices were controlled by modulating the behavior of the energy barriers of nanowire-nanowire interfaces and the Schottky barrier under the electrodes. Both barriers were found to be affected by the distribution and availability of charges along the nanowires mesh and in the surrounding atmosphere. The consequent memristive effect was dependent of the environment conditions but also controllable by managing the availability of charges for the transport properties. Using a polymeric barrier layer to avoid the direct contact of nanowires with the surrounding atmosphere proved to be an effective method to obtain reliable/better results after many memristive cycles. This simple procedure of polymeric coating offers some benefits such a more stable gain and a ON/OFF ratio improvement (from 1.55 to 3.60). Furthermore, coated devices showed potential features for use in synaptic learning applications.

Advanced Printing Transfer of Assembled Silver Nanowire Network into Elastomer for Constructing Stretchable Conductors

Excellent electrical performance of assemblies of 1D silver nanowires (AgNWs) has been demonstrated in the past years. Up to now, however, there are limited approaches to realize simultaneously deterministic assembly with dense arrangement of AgNWs and desired functional layouts. Herein, an assembly strategy from compressed air‐modulated alignment of AgNWs to heterogeneous integration of stretchable sensing devices through printing transfer is proposed. In this process, a convective flow induced by compressed air brings the AgNWs to the air–droplet interface, where the AgNWs are assembled with excellent alignment and packing due to the surface flow, van der Waals, and capillary interactions. Compared with those random AgNWs networks, the oriented, densely packed AgNWs exhibit a lower and uniform electrical sheet resistance. To incorporate the AgNWs to an elastomer substrate, direct ink writing is employed to transfer the assembled AgNW network to the printed silicone elastomer with desirable patterns. Excellent electrical property is demonstrated including a wide electrical response range from 10% to 120% strain, and high electrical repeatability. An antibacterial property is confirmed, notifying additional benefit as wearable sensors. The printing transfer of preassembled AgNW networks to the printed elastomer patterns provides a facile strategy to construct stretchable electronic devices.

Photoelectrochemical UV Detector Based on High-Temperature Resistant ITO Nanowire Network Transparent Conductive Electrodes: Both the Response Range and Responsivity Are Improved.

UV transparent conductive electrodes based on transferable ITO nanowire networks were prepared to solve the problem of low UV light utilization in conventional photoelectrochemical UV detectors. The mutually cross-linked ITO nanowire network achieved good electrical conductivity and light transmission, and the novel electrode had a transmission rate of more than 80% throughout the near-UV and visible regions. Compared to Ag nanowire electrodes with similar functionality, the chemical stability of the ITO nanowire transparent conductive electrode ensured that the device worked stably in iodine-based electrolytes. More importantly, ITO electrodes composed of oxides could withstand temperatures above 800 °C, which is extremely critical for photoelectrochemical devices. After the deposition of a TiO2 active layer using the high-temperature method, the response range of the photoelectrochemical UV detector was extended from a peak-like response between 300-400 nm to a plateau-like response between 200-400 nm. The responsivity was significantly increased to 56.1 mA/W. The relationship between ITO nanowire properties and device performance, as well as the reasons for device performance enhancement, were intensively investigated.

Three-Dimensional WCoFe Ternary Metal Oxide Nanowire Network as a Carbon-Free Cathode Catalyst for High-Performance Li–O2 Batteries

Three-Dimensional WCoFe Ternary Metal Oxide Nanowire Network as a Carbon-Free Cathode Catalyst for High-Performance Li–O₂ Batteries

Bubble-Mediated Large-Scale Hierarchical Assembly of Ultrathin Pt Nanowire Network Monolayer at Gas/Liquid Interfaces.

Extensive macroscale two-dimensional (2-D) platinum (Pt) nanowire network (NWN) sheets are created through a hierarchical self-assembly process with the aid of biomolecular ligands. The Pt NWN sheet is assembled from the attachment growth of 1.9 nm-sized 0-D nanocrystals into 1-D nanowires featuring a high density of grain boundaries, which then interconnect to form monolayer network structures extending into centimeter-scale size. Further investigation into the formation mechanism reveals that the initial emergence of NWN sheets occurs at the gas/liquid interfaces of the bubbles produced by sodium borohydride (NaBH4) during the synthesis process. Upon the rupture of these bubbles, an exocytosis-like process releases the Pt NWN sheets at the gas/liquid surface, which subsequently merge into a continuous monolayer Pt NWN sheet. The Pt NWN sheets exhibit outstanding oxygen reduction reaction (ORR) activities, with specific and mass activities 12.0 times and 21.2 times greater, respectively, than those of current state-of-the-art commercial Pt/C electrocatalysts.

Virus-templated redox nanowire network for enzyme electrode

Viruses have unique coat proteins that are genetically modifiable. Their surface can serve as a nano-template on which electroactive molecules are immobilized. In this study, we report filamentous bacteriophage as a backbone to which redox mediators are covalently and densely tethered, constructing redox nanowire, i.e. an electron conducting biomaterial. The highly ordered coat proteins of a filamentous bacteriophage provide flexible and biocompatible platform to constitute a biohybrid redox nanowire. Incorporating bacteriophage and redox molecules form an entangled assembly of nanowires enabling facile electron transfer. Electron transfer among the molecular mediators in the entangled assembly originates apparent electron diffusion of which the electron transfer rate is comparable to that observed in conventional redox polymers. Programming peptide terminals suggests further enhancement in electron mediation by increasing redox species mobility. In addition, the redox nanowire film functions as a favorable matrix for enzyme encapsulation. The stability of the enzymes entrapped in this unique matrix is substantially improved.

Synthesis of SnO2 nanowires using thermal chemical vapor deposition with SnO powder and their application as self-powered ultraviolet photodetectors

We report on the performance of self-powered ultraviolet (UV) photodetectors composed of SnO2 nanowire (NW) networks. SnO2 NWs with a length of several hundred micrometers can be synthesized by thermal chemical vapor deposition (CVD) using SnO powder as the raw material, which has the advantages of a low process temperature and no requirement for a reducing agent. Based on the characterization results obtained through synchrotron X-ray diffraction (XRD), scanning electron microscopy, and transmission electron microscopy (TEM), we determined the growth behavior of SnO2 NWs via a vapor-liquid-solid mechanism with Au nanoparticles. The NW growth switched from an initial in-plane growth to subsequent vertical growth, forming NW cotton. This was started at a process temperature of 600 ℃ and optimized at 800 ℃. Moreover, the XRD and TEM results indicate that the NWs mainly grew in the form of SnO2, although the formation of SnO NWs was also possible. Metal−SnO2 NW−metal type photodetectors were fabricated, and their photoresponsivity to UV light in the range from 200 to 400 nm was investigated. The device exhibited a photo-to-dark current ratio of ∼2.17 × 106 at an applied bias of 10 V and 254 nm UV exposure. A maximum responsivity of about 1100 A/W was estimated at a wavelength of 270 nm, and the cutoff edge wavelength appeared around 350 nm. In particular, the self-powered photoresponse at nominal zero bias was ∼1.23 nA. The results of this study support the idea that SnO2 NWs are promising candidates for self-powered deep-UV photodetectors and that thermal CVD using SnO powder is suitable for synthesizing SnO2 NWs at temperatures as low as 700 °C.

Trapping Layers Prevent Dopant Segregation and Enable Remote Doping of Templated Self-Assembled InGaAs Nanowires.

Selective area epitaxy is a promising approach to define nanowire networks for topological quantum computing. However, it is challenging to concurrently engineer nanowire morphology, for carrier confinement, and precision doping, to tune carrier density. We report a strategy to promote Si dopant incorporation and suppress dopant diffusion in remote doped InGaAs nanowires templated by GaAs nanomembrane networks. Growth of a dilute AlGaAs layer following doping of the GaAs nanomembrane induces incorporation of Si that otherwise segregates to the growth surface, enabling precise control of the spacing between the Si donors and the undoped InGaAs channel; a simple model captures the influence of Al on the Si incorporation rate. Finite element modeling confirms that a high electron density is produced in the channel.

Tunable Magnetic Properties of Interconnected Permalloy Nanowire Networks

In this study, we investigate the magnetic properties of interconnected permalloy nanowire networks using micromagnetic simulations. The effects of interconnectivity on the hysteresis curves, coercivity, and remanence of the nanowire networks are analyzed. Our results reveal intriguing characteristics of the hysteresis curves, including nonmonotonic behaviors of coercivity as a function of the position of horizontal nanowires relative to vertical nanowires. By introducing horizontal nanowires at specific positions, the coercivity of the nanowire networks can be enhanced without altering the material composition. The normalized remanence remains relatively constant regardless of the position of the horizontal wires, although it is lower in the interconnected nanowire arrays compared to nonconnected arrays. These findings provide valuable insights into the design and optimization of nanowire networks for applications requiring tailored magnetic properties.

A mesh network of MnO nanowires and CNTs reinforced by molecularly imprinted structures for the selective detection of para-nitrophenol

A mesh network of MnO nanowires and CNTs reinforced by molecularly imprinted structures for the selective detection of para-nitrophenol

Gate-switchable SQUID based on Dirac semimetal Cd3As2 nanowires

Topological semimetal nanowires in proximity with $s$-wave superconductors are promising for Majorana-based topological quantum computers. To braid the Majorana modes, an interconnected nanowire network coupled to superconductor islands is required. Here, we have fabricated the nanostructures based on two Dirac semimetal ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$ nanowires connected in parallel to form a symmetric superconducting quantum interference device (SQUID). A proximity-induced superconducting state is achieved in the SQUID, and its gate voltage and magnetic field dependence are investigated. It is found that the supercurrent can be switched on/off by modulating the gate voltage, behaving as a supercurrent field-effect transistor. Under an out-of-plane magnetic field, the SQUID shows an anomalous magnetic field -enhanced superconductivity behavior near the Dirac point. An in-plane magnetic field experiment shows a typical $\ensuremath{\pi}$ periodicity of a critical current with the rotation angle. Our work realizes the implementation and characterization of nanowire SQUID structures, which is a significant step toward integrating Dirac semimetal nanowires into scalable superconducting networks for braiding non-Abelian quantum states.

Ultrahigh-Temperature-Tolerant NiO@Ag NW-Based Transparent Heater with High Stability, Durability, Ultraflexibility, and Quick Thermal Response

High-performance electrical heaters with high transmittance, fast response speed, superior heat resistance, ultraflexibility, high working temperature, and sufficient stabilities are highly desirable for application in heating systems in areas such as healthcare and aerospace. Herein, we demonstrate an ultrahigh-temperature-tolerant flexible transparent heater (FTH) consisting of a NiO@Ag core–shell nanowire (NiO@Ag NW) network and a colorless polyimide (cPI) film. NiO nanoshells are formed uniformly on the surface of Ag NWs through the solution process, which enhances the stability of Ag NWs. The heating behaviors and transmittance can be controlled by the NiO@Ag NW spin-coating cycle. The NiO@Ag NW-based FTHs show a fast thermal response of ∼15 s, a high transmittance of 86.2% in the visible region, and a large thermal figure of merit of 30.7 m2·°C/W under optimal preparation conditions. The saturation temperature of FTHs has barely changed after 20 taping tests and 1000 bending cycles at a bending radius of 0.5 mm. Particularly, the heating temperature of FTHs can reach 266 °C in the air under an applied voltage of 9 V. Moreover, the FTHs possess sufficient heating reliability, stability, and repeatability during the long-term and repeated heating cycles. In addition, the FTHs are resistant to a number of harsh environments.

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.

Improved Stability of Copper Nanowires with Solution-Grown NiO Shells as Protective Coating

The fast degradation of copper in ambient conditions hinders the practical application of copper nanowires (Cu NWs) in flexible electronics. Here, we describe a simple yet effective solution method for growing NiO shells on the surface of Cu NWs, which enables the protection of the Cu NW network against oxidation without degrading the optical and electrical properties. The corresponding values (for example, before coating: 13.6 Ω/sq at 84.4%, after coating: 14.9 Ω/sq at 84.8%) show that the deposition of NiO shell enables the preservation of high transparency and conductivity of Cu. In contrast to the massive degradation of Cu NW networks including a significant reduction in conductivity in a range of harsh environments (strong oxidation, high temperature, heat and humidity conditions), the Cu NW@NiO networks can survive structurally and maintain conductivity. Finally, a flexible alternating current electroluminescent device employing the Cu NW@NiO networks as the transparent electrodes is realized to demonstrate the availability of Cu NW@NiO networks.

Boosting electrochemical property of carbon cloth for supercapacitors with electrodeposited aniline-based copolymers

As a kind of promising electrode in flexible supercapacitors, carbon cloth (CC) has been functionalized to boost its electrochemical performance. Here, facile electrochemical copolymerization was used to boost the electrochemical property of CC by adjusting the structure and morphology of electrodeposited aniline-based copolymers. With the optimized feeding ratio of triphenylamine (TPA), the aniline-based copolymer (PANI-T) was obtained on the functionalized CC (FCC) with a unique morphology as network of nanowires, showing the higher areal specific capacitance of 2489 mF cm−2 than the one with polyaniline (PANI) nanorods (FCC@PANI) of 2125 mF cm−2 and the one with copolymer nanoparticles of aniline and diphenylamine (DPA) (FCC@PANI-D) of 1693 mF cm−2 at 1 mA cm−2. Compared with the FCC@PANI electrode, the boosting ratio was 126% and 147% for the FCC@PANI-D and FCC@PANI-T, respectively. The electrochemical performance of the flexible solid-state symmetrical supercapacitor (FSSC) indicated the promising potential of the FCC@PANI-T for practical application.

Interplay between diffusion and magnon-drag thermopower in pure iron and dilute iron alloy nanowire networks

Results of measurements on the thermoelectric power of 45 nm diameter interconnected nanowire networks consisting of pure Fe, dilute FeCu and FeCr alloys and Fe/Cu multilayers are presented. The thermopower values of Fe nanowires are very close to those found in bulk materials, at all temperatures studied between 70 and 320 K. For pure Fe, the diffusion thermopower at room temperature, estimated to be around − 15 upmuV/K from our data, is largely supplanted by the estimated positive magnon-drag contribution, close to 30 upmuV/K. In dilute FeCu and FeCr alloys, the magnon-drag thermopower is found to decrease with increasing impurity concentration to about 10 upmuV/K at 10% impurity content. While the diffusion thermopower is almost unchanged in FeCu nanowire networks compared to pure Fe, it is strongly reduced in FeCr nanowires due to pronounced changes in the density of states of the majority spin electrons. Measurements performed on Fe(7 nm)/Cu(10 nm) multilayer nanowires indicate a dominant contribution of charge carrier diffusion to the thermopower, as previously found in other magnetic multilayers, and a cancellation of the magnon-drag effect. The magneto-resistance and magneto-Seebeck effects measured on Fe/Cu multilayer nanowires allow the estimation of the spin-dependent Seebeck coefficient in Fe, which is about − 7.6 upmuV/K at ambient temperature.

Mean Field Theory of Self‐Organizing Memristive Connectomes

AbstractBiological neuronal networks are characterized by nonlinear interactions and complex connectivity. Given the growing impetus to build neuromorphic computers, understanding physical devices that exhibit structures and functionalities similar to biological neural networks is an important step toward this goal. Self‐organizing circuits of nanodevices are at the forefront of the research in neuromorphic computing, as their behavior mimics synaptic plasticity features of biological neuronal circuits. However, an effective theory to describe their behavior is lacking. This study provides for the first time an effective mean field theory for the emergent voltage‐induced polymorphism of circuits of a nanowire connectome, showing that the behavior of these circuits can be explained by a low‐dimensional dynamical equation. The equation can be derived from the microscopic dynamics of a single memristive junction in analytical form. The effective model is tested on experiments of nanowire networks and show that it fits both the potentiation and depression of these synapse‐mimicking circuits. It is shown that this theory applies beyond the case of nanowire networks by formulating a general mean‐field theory of conductance transitions in self‐organizing memristive connectomes.

InGaO3 Nanowire Networks for Deep Ultraviolet Photodetectors

Wide band gap semiconductor nanomaterials have great research prospects in power semiconductor devices, radio frequency devices, optoelectronic sensor devices, and so on. Among them, gallium oxide is considered as the representative material of wide band gap semiconductor nanomaterials as a deep ultraviolet (UV) photoelectric sensing device because of its 4.9 eV band gap width. However, the traditional synthesis of this kind of metal oxide semiconductor nanomaterials by the chemical vapor deposition (CVD) method still has some problems. The experimental process is not easy to achieve due to the high temperature of 960 °C, and the lower photocurrent makes it difficult to read the photoelectric signal for subsequent devices because of the optical response current of the order of nanoampere. In this work, gallium antimonide and indium antimonide were selected as the nutrition reaction materials, while oxygen is used as the oxide materials. InGaO3 nanowire network materials were prepared at a lower temperature of 700 °C and a lower working pressure of 0.2 kPa, the deep UV photoelectric response of the optoelectronic devices was measured, and high performance was obtained at 5 V bias, like at a power of 0.64 μW/cm2, the response is 80.1 A/W, detection is 1.03 × 1014, and the external quantum efficiency is 3.9 × 104. Especially, the photoelectric current 34.1 μA is far larger than that of the level of several nanoampere traditional gallium oxide devices. Its reaction principle is that In and Ga metal nucleate and oxidize on the substrate to form InGaO3 nanowires after antimonide decomposition at 700 °C temperature, which is lower than 960 °C of the traditional CVD reaction method. This mechanism is different from that of traditional graphite and oxide powder reduction, which can save energy. In a word, this research has invented a method for preparing indium doping gallium oxide nanomaterials, which provides a reference for rapid preparation of response materials and low-energy consumption for deep UV photoelectric devices.

Humidity-dependent electrical performance of CuO nanowire networks studied by electrochemical impedance spectroscopy.

Electrochemical impedance spectroscopy was applied for studying copper oxide (CuO) nanowire networks assembled between metallic microelectrodes by dielectrophoresis. The influence of relative humidity (RH) on electrical characteristics of the CuO nanowire-based system was assessed by measurements of the impedance Z. A slight increase of Z with increasing RH at low humidity was followed by a three orders of magnitude decrease of Z at RH above 50-60%. The two opposite trends observed across the range of the examined RH of 5-97% can be caused by water chemisorption and physisorption at the nanowire interface, which suppress electronic transport inside the p-type semiconductor nanowire but enhance ionic transport in the water layers adsorbed on the nanowire surface. Possible physicochemical processes at the nanowire surface are discussed in line with equivalent circuit parameters obtained by fitting impedance spectra. The new investigation data can be useful to predict the behavior of nanostructured CuO in humid environments, which is favorable for advancing technology of nanowire-based systems suitable for sensor applications.