Protecting the Nanoscale Properties of Ag Nanowires with a Solution-Grown SnO2 Monolayer as Corrosion Inhibitor

Conductive Textile Embedded with Bioinspired Wettability for Prolonged and Energy Efficient Thermal Management

The design of electrically conductive textiles appears to be a promising approach to combat the existing challenge of deaths caused by severe cold climates around the globe. However, reports on the scalable fabrication of tolerant conductive textiles maintaining a low electrical resistance with an ability for unperturbed and prolonged performance are scarce. Here, a breathable and wrappable water-repellent conductive textile (water-repellent CT) with electrothermal and photothermal conversion abilities at low external voltage and in weak solar light is introduced, respectively. In the current approach, less carbon-containing silver nanowires (AgNWs) are selected to spray deposit on a commercially available woven textile to attend a uniform and highly conductive network over a large dimension. The subsequent spray deposition of a reaction mixture of selected small molecules prevents aerial oxidation of deposited AgNWs even at elevated temperatures and provides bioinspired extreme water-repellence. Thus, it maintains an unperturbed performance even when exposed to different aqueous environment. Using the scalability of current approach and durability of prepared water-repellent CT, relevant wearable devices are derived to demonstrate personal heat management ability with rechargeable and portable battery for prolonged duration in severely cold conditions. Thus, the prepared water-repellent CT enabled an energy-efficient and "wrappable" heating, providing a basis for various potential applications.

Integrated Manipulation and Addressing of Spin Defect in Diamond

Scalable and addressable integrated manipulation of qubits is crucial for practical quantum information applications. Different waveguides have been used to transport the optical and electrical driving pulses, which are usually required for qubit manipulation. However, the separated multifields may limit the compactness and efficiency of manipulation and introduce unwanted perturbation. Here, we develop a tapered fiber-nanowire-electrode hybrid structure to realize integrated optical and microwave manipulation of solid-state spins at nanoscale. Visible light and microwave driving pulses are simultaneously transported and concentrated along an Ag nanowire. Studied with spin defects in diamond, the results show that the different driving fields are aligned with high accuracy. The spatially selective spin manipulation is realized. And the frequency-scanning optically detected magnetic resonance (ODMR) of spin qubits is measured, illustrating the potential for portable quantum sensing. Our work provides a new scheme for developing compact, miniaturized quantum sensors and quantum information processing devices.

Exploring the degradation of silver nanowire networks under thermal stress by coupling in situ X-ray diffraction and electrical resistance measurements

The thermal instability of silver nanowires (AgNWs) leads to a significant increase of the electrical resistance of AgNW networks. A better understanding of the relationship between the structural and electrical properties of AgNW networks is primordial for their efficient integration as transparent electrodes (TEs) for next-generation flexible optoelectronics. Herein, we investigate the in situ evolution of the main crystallographic parameters (i.e. integrated intensity, interplanar spacing and peak broadening) of two Ag-specific Bragg peaks, (111) and (200), during a thermal ramp up to 400 °C through in situ X-ray diffraction (XRD) measurements, coupled with in situ electrical resistance measurements on the same AgNW network. First, we assign the (111) and (200) peaks of χ-scans to each five crystallites within AgNWs using a rotation matrix model. Then, we show that the thermal transition of bare AgNW networks occurs within a temperature range of about 25 °C for the electrical properties, while the structural transition spans over 200 °C. The effect of a protective tin oxide coating (SnO2) on AgNW networks is also investigated through this original in situ coupling approach. For SnO2-coated AgNW networks, the key XRD signatures from AgNWs remain constant, since the SnO2 coating prevents Ag atomic surface diffusion, and thus morphological instability (i.e. spheroidization). Moreover, the SnO2 coating does not affect the strain of both (111) and (200) planes. The thermal expansion for bare and SnO2-coated AgNW networks appears very similar to the thermal expansion of bulk Ag. Our findings provide insights into the underlying failure mechanisms of AgNW networks subjected to thermal stress, helping researchers to develop more robust and durable TEs based on metallic nanowire networks.

Influence of tin oxide decoration on the junction conductivity of silver nanowires

Flexible electrodes using nanowires (NWs) suffer from challenges of long-term stability and high junction resistance which limit their fields of applications. Welding via thermal annealing is a common strategy to enhance the conductivity of percolated NW networks, however, it affects the structural and mechanical integrity of the NWs. In this study we show that the decoration of NWs with an ultrathin metal oxide is a potential alternative procedure which not only enhances the thermal and chemical stability but, moreover, provides a totally different mechanism to reduce the junction resistance upon heat treatment. Here, we analyze the effect of SnO_xdecoration on the conductance of silver NWs and NW junctions by using a four-probe measurement setup inside a scanning electron microscope. Dedicated transmission electron microscopy analysis in plan-view and cross-section geometry are carried out to characterize the nanowires and the microstructure of the junctions. Upon heat treatment the junction resistance of both plain silver NWs and SnO_x-decorated NWs is reduced by around 80%. While plain silver NWs show characteristic junction welding during annealing, the SnO_x-decoration reduces junction resistance by a solder-like process which does not affect the mechanical integrity of the NW junction and is therefore expected to be superior for applications.

Heterojunction MnO2-nanosheet-decorated Ag nanowires with enhanced oxidase-like activity for the sensitive dual-mode detection of glutathione

The biocatalytic design of nanomaterials with enzyme-like activity is considered a reliable and promising toolkit for the generation of diagnostic agents in complex biological microenvironments. However, the preparation of nanomaterials while maintaining a high catalytic activity in tumor cells (pH 6.0-6.5) poses a prominent challenge. Herein, we constructed a biomimetic enzyme-trigged dual-mode system with colorimetry at 652 nm and photothermal biosensors to detect glutathione based on hollow MnO₂-nanosheet-decorated Ag nanowires (Ag@MnO₂) as an oxidase-like nanozyme. As expected, Ag@MnO₂ catalyzed the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the absence of H₂O₂, leading to a blue-colored oxidized TMB (oxTMB) that displayed oxidase-like activity in pH 6.0. Interestingly, the portable dual-mode colorimetry and photothermal method for GSH was developed based on the redox reaction between GSH and oxTMB. This detection method exhibited a wide linear range of 0.1-55 μM for GSH with a low detection limit of 0.08 μM. This work highlights a new insight into nanotechnology by taking advantage of biomimetic design in biological analysis.

Embedding SnO2 Thin Shell Protected Ag Nanowires in SnO2 ETL to Enhance the Performance of Perovskite Solar Cells

The energy level mismatching between SnO₂ and perovskite and the nonradiative recombination at SnO₂-perovskite interface severely degrade the extraction of carriers, reducing the power conversion efficiency (PCE) and stability of planar perovskite solar cells (PSCs) based on SnO₂ electron transfer layer (ETL). In the present work, a reinforced SnO₂ ETL was successfully developed by embedding SnO₂ thin shell protected Ag nanowires (Ag/SnO₂ NWs) in traditional planar SnO₂ film, which was proved to not only lower the conduction band of SnO₂ to adjust the energy level matching, but also significantly reduce the interfacial carrier recombination. Moreover, Ag/SnO₂ NWs improved the electrical conductivity of SnO₂ ETL, and effectively promoted carrier transport. Benefiting from the use of Ag/SnO₂ NWs, our newly designed PSC achieved a significantly increased champion PCE of 19.78%, which is 7% higher than the traditional PSC without Ag/SnO₂ NWs embedding, indicating its great application potential in PSCs.

Scalable Fabrication of Metallic Conductive Fibers from Rheological Tunable Semi-Liquid Metals

Conductive polymer fibers/wires (CPFs) are important materials in modern technologies due to their unique one-dimension geometry, electrical conductivity, and flexibility. However, the advanced applications of current CPFs are limited by their low electrical conductivities (<500 S/m) and poor interfacial interactions between conductive fillers (e.g., graphite) and polymers. Therefore, in current electrical applications, metal wires/foils like copper and aluminum are the most frequently utilized conductive fibers/wires instead of the inferior conductive CPFs. This work successfully addresses the heavy phase segregation between polymers and conductive inorganic materials to obtain semiliquid metal polymer fibers (SLMPFs) which exhibit an ultrahigh electrical conductivity (over 10⁶ S/m), remarkable thermal processability, and considerable mechanical performance (Young's modulus: ~300 MPa). Semiliquid metal (gallium-tin alloy) with tunable viscosities is the key to achieve the excellent miscibility between metals and polymers. Both the rheological results and numerical simulations demonstrate the critical viscosity matching for the successful preparation of the fibers. More importantly, the fibers are adapted with classic polymer melt-processing like melt injection, which indicates the scalable production of the highly conductive fibers. The SLMPFs are highly promising substitutes for metal wires/fibers in modern electrical applications such as electricity transmission, data communication, and underwater works.

Focusing the electromagnetic field to 10-6λ for ultra-high enhancement of field-matter interaction

Focusing electromagnetic field to enhance the interaction with matter has been promoting researches and applications of nano electronics and photonics. Usually, the evanescent-wave coupling is adopted in various nano structures and materials to confine the electromagnetic field into a subwavelength space. Here, based on the direct coupling with confined electron oscillations in a nanowire, we demonstrate a tight localization of microwave field down to 10⁻⁶λ. A hybrid nanowire-bowtie antenna is further designed to focus the free-space microwave to this deep-subwavelength space. Detected by the nitrogen vacancy center in diamond, the field intensity and microwave-spin interaction strength are enhanced by 2.0 × 10⁸ and 1.4 × 10⁴ times, respectively. Such a high concentration of microwave field will further promote integrated quantum information processing, sensing and microwave photonics in a nanoscale system.

Subwavelength focusing of electromagnetic fields often uses evanescent waves and nanostructures to aid confinement. Here, the authors localize a microwave field to 6 orders of magnitude smaller than the wavelength, by coupling to confined electron oscillations in a hybrid nanowire-bowtie antenna.

Silver Nanowire Networks: Ways to Enhance Their Physical Properties and Stability

Silver nanowire (AgNW) networks have been intensively investigated in recent years. Thanks to their attractive physical properties in terms of optical transparency and electrical conductivity, as well as their mechanical performance, AgNW networks are promising transparent electrodes (TE) for several devices, such as solar cells, transparent heaters, touch screens or light-emitting devices. However, morphological instabilities, low adhesion to the substrate, surface roughness and ageing issues may limit their broader use and need to be tackled for a successful performance and long working lifetime. The aim of the present work is to highlight efficient strategies to optimize the physical properties of AgNW networks. In order to situate our work in relation to existing literature, we briefly reported recent studies which investigated physical properties of AgNW networks. First, we investigated the optimization of optical transparency and electrical conductivity by comparing two types of AgNWs with different morphologies, including PVP layer and AgNW dimensions. In addition, their response to thermal treatment was deeply investigated. Then, zinc oxide (ZnO) and tin oxide (SnO2) protective films deposited by Atmospheric Pressure Spatial Atomic Layer Deposition (AP-SALD) were compared for one type of AgNW. We clearly demonstrated that coating AgNW networks with these thin oxide layers is an efficient approach to enhance the morphological stability of AgNWs when subjected to thermal stress. Finally, we discussed the main future challenges linked with AgNW networks optimization processes.

Atomic, Molecular and Hybrid Oxygen Structures on Silver

Interactions between oxygen and silver are important in many areas of science and technology, including materials science, medical, biomedical and environmental applications, spectroscopy, photonics, and physics. In the chemical industry, identification of oxygen structures on Ag catalysts is important in the development of environmentally friendly and sustainable technologies that utilize gas-phase oxygen as the oxidizing reagent without generating byproducts. Gas-phase oxygen adsorbs on Ag atomically by breaking the O-O bond and molecularly by preserving the O-O bond. Atomic O structures have Ag-O vibrations at 240-500 cm^-1. Molecular O₂ structures have O-O vibrations at significantly higher values of 870-1150 cm^-1. In this work, we identify hybrid atomic-molecular oxygen structures, which form when one adsorbed O atom reacts with one lattice O atom on the surface or in the subsurface of Ag. Thus, these hybrid structures require dissociation of adsorbed molecular oxygen into O atoms but still possess the O-O bond. The hybrid structures have O-O vibrations at 600-810 cm^-1, intermediate between the Ag-O vibrations of atomic oxygen and the O-O vibrations of molecular oxygen. The hybrid O-O structures do not form by a recombination of two adsorbed O atoms because one of the O atoms in the hybrid structure must be embedded into the Ag lattice. The hybrid oxygen structures are metastable and, therefore, serve as active species in selective oxidation reactions on Ag catalysts.

Flexible and transparent silver nanowires/biopolymer film for high-efficient electromagnetic interference shielding

Flexible and transparent conductive films are highly desirable in some optoelectronic devices, such as smart windows, touch panels, as well as displays and electromagnetic protection field. Silver nanowire (Ag NW) has been considered as the best material to replace indium tin oxide (ITO) to fabricate flexible transparent electromagnetic interference (EMI) shielding films due to its superior comprehensive performance. However, the common substrates supporting Ag NWs require surface modification to enhance the adhesion with Ag NWs. In this work, a flexible and transparent Ag NWs EMI shielding film with sandwich structure through a facile rod-coating method, wherein Ag NWs network were embedded between biodegradable gelatin-based substrate and cover layer. The interfacial adhesion between Ag NWs and gelatin-based layers was enhanced by hydrogen-bonding interaction and swelling effect without any pretreatment. The shielding effectiveness (SE) of the G/Ag NW/G (G represents gelatin-based layer) film reaches 37.74 dB at X band with an optical transmittance of 72.0 %. What's more, the flexible gelatin-based layer and encapsulated structure endow the resultant G/Ag NW/G film integrating excellent mechanical properties, reliable durability, antioxidation, as well as anti-freezing performance. This work paves a new way for fabricating flexible transparent EMI shielding films.

One-dimensional Ag-CoNi nanocomposites modified with amorphous Sn(OH)2/SnO2 shells for broadband microwave absorption

High-performance microwave absorption absorbers play important roles in the fields of radar stealth, electromagnetic protection, and antenna technology. In this work, high aspect-ratio Ag nanowires were decorated with magnetic CoNi nanoparticles via a PVP-induced solvothermal method, and then amorphous Sn(OH)₂/SnO₂ shells were introduced through an in-situ oxidative hydrolysis method, successfully preparing Ag-CoNi@Sn(OH)₂/SnO₂ composites. The morphology and ingredient of composites were ascertained by SEM, TEM, XRD, EDX, and XPS. As Ag-CoNi nanocomposites are coated by Sn(OH)₂/SnO₂ shells, the minimum reflection loss value is decreased from -31.7 dB (10.1 GHz) to -37.8 dB (6.4 GHz), and the maximum effective absorption bandwidth is extended from 3.9 GHz (10.3-14.2 GHz) to 5.8 GHz (10.7-16.5 GHz). Analyses of electromagnetic parameters reveal the possible mechanisms, involving surface plasma resonance, conductive loss, interfacial polarization, dipole polarization, exchange resonance, eddy current effect, multiple reflection and scattering. Thus, Ag nanowires modified with CoNi nanoparticles and amorphous Sn(OH)₂/SnO₂ shells can effectively balance the impedance matching and attenuation capability. It is a new strategy to achieve broadband microwave absorbers.

Fabrication of antireflective silver-capped tin oxide nano-obelisk arrays as high sensitive SERS substrate

Hybrid noble metal-semiconductor oxide nanostructures often provide unique and synergetic functionalities that are highly desirable in various practical applications. However, the fabrication of such systems with desired functionalities using cost-effective techniques is still a great challenge. In this work, we report a facile route for the preparation of novel Ag/SnO₂ nano-obelisk arrayed thin films on silicon substrates by spray pyrolysis and thermal evaporation techniques. The prepared samples exhibited broadband antireflectance in both UV and visible regions attributed to the refractive index gradient and scattering provided by the nano-obelisk arrays. The localised surface plasmon resonance of silver nanocaps further enhanced the light absorption contributing to the antireflective property of the hybrid system. Ag/SnO₂ nano-obelisk arrayed thin film exhibited excellent SERS performance with an enhancement factor of 1.13 × 10⁸ with a limit of detection value of 10^-12 M for the trace detection of R6G dye. In addition, Ag/SnO₂ nano-obelisk arrayed thin film based SERS substrate exhibited good homogeneity across the measured spots and outstanding stability which are essential for quantitative field analysis. The results indicate that the Ag/SnO₂ nano-obelisk arrayed thin films are efficient SERS substrates with the merits of having the ease of production, high sensitivity and stability for various practical sensing applications.

A SnO2 shell for high environmental stability of Ag nanowires applied for thermal management

Since silver nanowires (AgNWs) show high infrared reflectance many studies present their applicability as thermal management products for various wearable textiles. However, their use for practical purposes is only partially evaluated, without focusing on improving their low atmospheric and liquid stability. This report describes a new approach for the topic and proposes a facile method of Ag nanowire passivation with a SnO2 layer for high environmental stability and retention of high infrared reflectance. The one-step passivation process of AgNWs was carried out in the presence of sodium stannate in an aqueous solution at 100 °C, and resulted in the formation of core/shell Ag/SnO2 nanowires. This study presents the morphological, chemical, and structural properties of Ag/SnO2NWs formed with a 14 nm thick SnO2 shell, consisting of 7 nm rutile-type crystals, covering the silver metallic core. The optical properties of the AgNWs changed significantly after shell formation, and the longitudinal and transverse modes in the surface plasmon resonance spectrum were red shifted as a result of the surrounding media dielectric constant changes. The passivation process protected the AgNWs from decomposition in air for over 4 months, and from dissolution in a KCN solution at concentrations up to 0.1 wt%. Moreover, the report shows the microwave irradiation effect on the shell synthesis and previously synthesised Ag/SnO2NWs. The post-synthesis irradiation, as well as the SnO2 shell obtained by microwave assistance, did not allow long-term stability to be achieved. The microwave-assisted synthesis process was also not fast enough to inhibit the formation of prismatic silver structures from the nanowires. The Ag/SnO2NWs with a shell obtained by a simple hydrolysis process, apart from showing high infra-red reflectance on the para-aramid fabric, are highly environmentally stable. The presented SnO2 shell preparation method can protect the AgNW's surface from dissolution or decomposition and facilitate the designing of durable smart wearable thermal materials for various conditions.

Embedding Silver Nanowires into a Hydroxypropyl Methyl Cellulose Film for Flexible Electrochromic Devices with High Electromechanical Stability

Transparent conductive films (TCFs) based on silver nanowires (AgNWs) are becoming one of the best candidates in realizing flexible optoelectronic devices. The AgNW-based TCF is usually prepared by coating AgNWs on a transparent polymer film; however, the coated AgNWs easily detach from the polymer underneath because of the weak adhesion between them. Herein, a network of AgNWs is embedded in the transparent hydroxypropyl methyl cellulose film, which has a strong adhesion with the AgNWs. The obtained TCF shows high optical transmittance (>85%), low roughness (rms = 4.8 ± 0.5 nm), and low haze (<0.2%). More importantly, owing to the embedding structure and strong adhesion, this TCF also shows excellent electromechanical stability, which is superior to the reported ones. Employing this TCF in a flexible electrochromic device, the obtained device exhibits excellent cyclic electromechanical stability and high coloring efficiency. Our work demonstrates a promising TCF with superior electromechanical stability for future applications in flexible optoelectronics.

A laser metallurgy route for the batch preparation of mm-scale 3D silver/graphite heteronanoclusters in air

We report a batch preparation of mm-scale 3D Ag hetero-nanoclusters which exhibit an excellent surface plasmon resonance ability via facile laser metallurgy. Under laser irradiation, the porous AgI-based coordination network crystals were instantly converted into 3D graphite-encapsulated Ag hetero-nanoclusters with uniform sizes and gaps in several seconds. The obtained hetero-nanoclusters exhibited superior 3D confocal laser energy utilization compared with the other 0D, 1D and 2D SERS substrates, solving the bottleneck caused by laser focusing deviation in the SERS active depth. The mass-produced SERS devices were ultra-sensitive for the detection of life and industrial organic pollutants in terms of low detection and enriched capacity.

Electric Dipole Descriptor for Machine Learning Prediction of Catalyst Surface-Molecular Adsorbate Interactions

The challenge of evaluating catalyst surface-molecular adsorbate interactions holds the key for rational design of catalysts. Finding an experimentally measurable and theoretically computable descriptor for evaluating surface-adsorbate interactions is a significant step toward achieving this goal. Here we show that the electric dipole moment can serve as a convenient yet accurate descriptor for establishing structure-property relationships for molecular adsorbates on metal catalyst surfaces. By training a machine learning neural network with a large data set of first-principles calculations, we achieve quick and accurate predictions of molecular adsorption energy and transferred charge. The training model using NO/CO@Au(111) can be extended to study additional substrates such as Au(001) or Ag(111), thus exhibiting extraordinary transferability. These findings validate the effectiveness of the electric dipole descriptor, providing an efficient modality for future catalyst design.

Facile synthesis of SnO2shell followed by microwave treatment for high environmental stability of Ag nanoparticles

This study describes a new method for passivating Ag nanoparticles (AgNPs) with SnO₂ layer and their further treatment by microwave irradiation. The one-step process of SnO₂ layer formation was carried out by adding sodium stannate to the boiling aqueous AgNPs solution, which resulted in the formation of core@shell Ag@SnO₂ nanoparticles. The coating formation was a tunable process, making it possible to obtain an SnO₂ layer thickness in the range from 2 to 13 nm. The morphology, size, zeta-potential, and optical properties of the Ag@SnO₂NPs were studied. The microwave irradiation significantly improved the environmental resistance of Ag@SnO₂NPs, which remained stable in different biological solutions such as NaCl at 150 mM and 0.1 M, Tris-buffered saline buffer at 0.1 M, and phosphate buffer at pH 5.6, 7.0, and 8.0. Ag@SnO₂NPs after microwave irradiation were also stable at biologically relevant pH values, both highly acidic (1.4) and alkaline (13.2). Moreover, AgNPs covered with a 13 nm-thick SnO₂ layer were resistant to cyanide up to 0.1 wt%. The microwave-treated SnO₂ shell can facilitate the introduction of AgNPs in various solutions and extend their potential application in biological environments by protecting the metal nanostructures from dissolution and aggregation.

This study describes a new method for passivating Ag nanoparticles (AgNPs) with SnO₂ layer and their further treatment by microwave irradiation.