Optimizing silver nanowire dimensions by the modification of polyol synthesis for the fabrication of transparent conducting films

Transparent conducting films (TCFs) made by the assembly/deposition of silver nanowires (Ag NWs) are widely used to manufacture flexible electronics such as touch screens, heaters, displays, and organic light-emitting diodes. Controlling the dimensions (length and diameter) of the nanowires is key in obtaining TCFs with the desired optoelectronic properties, namely sheet resistance and optical transparency. This work describes a combined experimental and theoretical investigation on the optimization of the NW dimensions to fabricate high-quality TCFs. Ag NWs of different dimensions are synthesized by the modified polyol method and the average diameter and length of the wires are tailored over a wide range, 35-150 nm and 12-130μm respectively, by controlling the synthesis parameters such as reaction conditions, stabilizing agents, and growth promoters. The synthesized NWs are spin coated on glass substrates to form TCFs. Comparing the films with different lengths, but identical diameters, enabled the quantification of the effect of length on the optoelectronic properties of the TCFs. Similarly, the effect of NW diameter is also studied. A non-uniformity factor is defined to evaluate the uniformity of the TCF and the transmittance of the NW network is shown to be inversely proportional to its area coverage. The sheet conductance versus the normalized number density is plotted for the different concentrations of NWs to extract a conductivity exponent that agrees well with the theoretical predictions. For thin film networks, the relation between the transmittance and sheet resistance provides the percolative figure of merit (FoM) as a fitting parameter. A large FoM is desirable for a good-performing TCF and the synthesis conditions to achieve this are optimized.

Transparent Electronics for Wearable Electronics Application

Recent advancements in wearable electronics offer seamless integration with the human body for extracting various biophysical and biochemical information for real-time health monitoring, clinical diagnostics, and augmented reality. Enormous efforts have been dedicated to imparting stretchability/flexibility and softness to electronic devices through materials science and structural modifications that enable stable and comfortable integration of these devices with the curvilinear and soft human body. However, the optical properties of these devices are still in the early stages of consideration. By incorporating transparency, visual information from interfacing biological systems can be preserved and utilized for comprehensive clinical diagnosis with image analysis techniques. Additionally, transparency provides optical imperceptibility, alleviating reluctance to wear the device on exposed skin. This review discusses the recent advancement of transparent wearable electronics in a comprehensive way that includes materials, processing, devices, and applications. Materials for transparent wearable electronics are discussed regarding their characteristics, synthesis, and engineering strategies for property enhancements. We also examine bridging techniques for stable integration with the soft human body. Building blocks for wearable electronic systems, including sensors, energy devices, actuators, and displays, are discussed with their mechanisms and performances. Lastly, we summarize the potential applications and conclude with the remaining challenges and prospects.

Tailoring Food Biopolymers into Biogels for Regenerative Wound Healing and Versatile Skin Bioelectronics

An increasing utilization of wound-related therapeutic materials and skin bioelectronics urges the development of multifunctional biogels for personal therapy and health management. Nevertheless, conventional dressings and skin bioelectronics with single function, mechanical mismatches, and impracticality severely limit their widespread applications in clinical. Herein, we explore a gelling mechanism, fabrication method, and functionalization for broadly applicable food biopolymers-based biogels that unite the challenging needs of elastic yet injectable wound dressing and skin bioelectronics in a single system. We combine our biogels with functional nanomaterials, such as cuttlefish ink nanoparticles and silver nanowires, to endow the biogels with reactive oxygen species scavenging capacity and electrical conductivity, and finally realized the improvement in diabetic wound microenvironment and the monitoring of electrophysiological signals on skin. This line of research work sheds light on preparing food biopolymers-based biogels with multifunctional integration of wound treatment and smart medical treatment.

Copper and silver nanowires for CO2 electroreduction

Copper and silver nanowires have been extensively investigated as the next generation of transparent conductive electrodes (TCEs) due to their ability to form percolating networks. Recently, they have been exploited as electrocatalysts for CO2 reduction. In this review, we present the most recent advances in this field summarizing different strategies used for the synthesis and functionalization/activation of copper and silver nanowires, as well as, the state of the art of their electrochemical performance with particular emphasis on the effect of the nanowire morphology. Novel perspectives for the development of highly efficient, selective, and stable electrocatalysts for CO2 reduction arise from the translation of NW-based TCEs in this challenging field.

Stretchable and Directly Patternable Double-Layer Structure Electrodes with Complete Coverage

Stretchable electrodes are widely used in next-generation wearable electronics. Recent studies incorporated designs that help rigid electrodes attain stretchability. However, these structures exhibited unsatisfactory charge/signal extraction efficiency because of their low areal fill factor. Additionally, they cannot be photolithographically patterned on polymer substrates because of their low adhesion, requiring additional complicated fabrication steps. We developed photolithographically patternable stretchable electrodes with complete coverage and enhanced charge-extraction efficiency. The electrodes, comprising double layers, included a chemically treated Ag nanowire mesh and Au thin film. The interfacial linker role of polyvinylpyrrolidone chemically strengthened the interfacial bonds, and the reinforced concrete structure of nanowire-embedded metal thin films enhanced the mechanical properties. Therefore, the electrodes provided superior efficiency and stability in capturing physical, electromagnetic, and electrophysiological signals while exceeding the existing stretchable electrode limits. A broad range of applications are foreseen, such as electrocardiogram sensing electrodes, strain sensors, temperature sensors, and antennas.

Advances and challenges in metallic nanomaterial synthesis and antibacterial applications

Multi-drug resistant bacterial infection has become one of the most serious threats to global public health. The preparation and application of new antibacterial materials are of great significance for solving the infection problem of bacteria, especially multi-drug resistant bacteria. The exceptional antibacterial effects of metal nanoparticles based on their unique physical and chemical properties make such systems ideal for application as antibacterial drug carriers or self-modified therapeutic agents both in vitro and in vivo. Metal nanoparticles also have admirable clinical application prospects due to their broad antibacterial spectrum, various antibacterial mechanisms and excellent biocompatibility. Nevertheless, the in vivo structural stability, long-term safety and cytotoxicity of the surface modification of metal nanoparticles have yet to be further explored and improved in subsequent studies. Herein, we summarized the research progress concerning the mechanism of metal nanomaterials in terms of antibacterial activity together with the preparation of metal nanostructures. Based on these observations, we also give a brief discussion on the current problems and future developments of metal nanoparticles for antibacterial applications.

Silver Nanowire Synthesis and Strategies for Fabricating Transparent Conducting Electrodes

One-dimensional metal nanowires, with novel functionalities like electrical conductivity, optical transparency and high mechanical stiffness, have attracted widespread interest for use in applications such as transparent electrodes in optoelectronic devices and active components in nanoelectronics and nanophotonics. In particular, silver nanowires (AgNWs) have been widely researched owing to the superlative thermal and electrical conductivity of bulk silver. Herein, we present a detailed review of the synthesis of AgNWs and their utilization in fabricating improved transparent conducting electrodes (TCE). We discuss a range of AgNW synthesis protocols, including template assisted and wet chemical techniques, and their ability to control the morphology of the synthesized nanowires. Furthermore, the use of scalable and cost-effective solution deposition methods to fabricate AgNW based TCE, along with the numerous treatments used for enhancing their optoelectronic properties, are also discussed.

Effect of nanofiller morphology on the electrical conductivity of polymer nanocomposites

Conductive polymers and nanocomposites have attracted great attention in industry and academia for their tremendous potential applications. Most of the research was focused on the type and amount of nano-additives used and fewer on their morphology which is critical in forming the conductive network. In this paper, a detailed investigation of the effect nanomaterial’s morphology was carried out to study their electrical conductivity properties. Silver nanowire (AgNW) nanocomposite and silver nanoparticle (AgNP) nanocomposite were fabricated. The morphology, crystallinity, and orientation of various silver nanofillers were characterized. AgNW based nanocomposites have shown a lower percolation threshold. A conductive unit based model was established to explain the evolution of the conductive network and aggregation. The aggregation geometry of nanofiller appeared as a dominant factor in altering the percolation behavior.

Silver Nanowires as Electron Transfer Mediators in Electrochemical Catechol Biosensors

The integration of nanomaterials as electron mediators in electrochemical biosensors is taking on an essential role. Due to their high surface-to-volume ratio and high conductivity, metallic nanowires are an interesting option. In this paper, silver nanowires (AgNWs) were exploited to design a novel catechol electrochemical biosensor, and the benefits of increasing the aspect ratio of the electron mediator (nanowires vs. nanoparticles) were analyzed. Atomic force microscopy (AFM) studies have shown a homogeneous distribution of the enzyme along the silver nanowires, maximizing the contact surface. The large contact area promotes electron transfer between the enzyme and the electrode surface, resulting in a Limit of Detection (LOD) of 2.7 × 10⁻⁶ M for tyrosinase immobilized onto AgNWs (AgNWs-Tyr), which is one order of magnitude lower than the LOD of 3.2 × 10⁻⁵ M) obtained using tyrosinase immobilized onto silver nanoparticles (AgNPs-Tyr). The calculated K_M constant was 122 mM. The simultaneous use of electrochemistry and AFM has demonstrated a limited electrochemical fouling that facilitates stable and reproducible detection. Finally, the biosensor showed excellent anti-interference characteristics toward the main phenols present in wines including vanillin, pyrogallol, quercetin and catechin. The biosensor was able to successfully detect the presence of catechol in real wine samples. These results make AgNWs promising elements in nanowired biosensors for the sensitive, stable and rapid voltammetric detection of phenols in real applications.

The surface plasmonic welding of silver nanowires via intense pulsed light irradiation combined with NIR for flexible transparent conductive films

In this work, surface plasmonic welding of silver nanowires (AgNWs) by intense pulse light (IPL) combined with NIR was investigated. AgNWs were coated on a flexible PET (polyethylene terephthalate) substrate using a bar-coater. The coated AgNW films were welded at room temperature and under ambient conditions by white IPL from a xenon lamp, assisted with light from a UV-C (ultraviolet C) and NIR (near infra-red) lamp using an in-house multi-wavelength IPL welding system. In order to investigate the welding mechanism, in situ monitoring with a Wheatstone bridge electrical circuit was performed. The sheet resistance changes of AgNW films during the welding process were monitored under various IPL conditions (e.g. light energy and on-time) with and without UV-C and NIR light irradiation. The microstructure of the welded AgNW film and the interface between the AgNW film and the PET substrate were observed using a scanning electron microscope (SEM) and transmission electron microscope (TEM). COMSOL multi-physics simulations were conducted and compared with the in situ monitoring results to discuss the in-depth mechanism of the IPL welding of AgNWs and its dependence on the wavelength of light. From this study, the optimal IPL welding conditions and appropriate wavelength were suggested, and the optimized IPL welding process could produce AgNW film with a lower sheet resistance (45.2 Ω sq^-1) and high transparency (96.65%) without damaging the PET substrate.

A one-step-assembled three-dimensional network of silver/polyvinylpyrrolidone (PVP) nanowires and its application in energy storage

Creating ultralight monolithic metal foams remains an outstanding challenge despite their important applications, e.g., in electronics, sensors and energy storage. Herein, a facile methodology is developed for one-step fabrication of silver/polyvinylpyrrolidone (PVP) nanowire (AgPNW) hydrogel and high-quality robust ultralight AgPNW aerogel (AgPNWA) on a large scale. The hydrogel is directly formed by in situ assembling hydrothermally-synthesized AgPNWs. The resultant ultralight AgPNWA exhibits very high electrical conductivity. The application of this one-step fabricated AgPNWA to enhance phase change materials (PCMs) for high-efficiency thermal energy storage is investigated. The AgPNWA-paraffin composite (APC) shows ∼350% thermal-efficiency enhancement, ∼463% mechanical hardening, and strong reliability against thermal cycling due to the potentially strong AgPNW-paraffin interfacial interaction. It is also observed that the thickness of the APC shrinks significantly but there is no change in its diameter during thermal cycles. Analytical models of liquid capillary filling of deformable fiber-based 3D networks are derived for the first time and are applied to analyze the thermal-cycling-induced-shape-stabilization behavior of the APC and the vaporization-induced collapse behavior of the AgPNW network. This work provides important insights into designing a facile 3D assembly of nanomaterials, and thermal energy storage materials with high performance and reliability.

Ultra-Uniform and Very Thin Ag Nanowires Synthesized via the Synergy of Cl-, Br- and Fe3+ for Transparent Conductive Films

The properties and applications of Ag nanowires (AgNWs) are closely related to their morphology and composition. Therefore, controlling the growth process of AgNWs is of great significance for technological applications and fundamental research. Here, silver nanowires (AgNWs) were synthesized via a typical polyol method with the synergistic effect of Cl⁻, Br⁻, and Fe³⁺ mediated agents. The synergistic impact of these mediated agents was investigated intensively, revealing that trace Fe³⁺ ions provided selective etching and hindered the strong etching effect from Cl⁻ and Br⁻ ions. Controlling this synergy allowed the obtainment of highly uniform AgNWs with sub-30 nm diameter and an aspect ratio of over 3000. Transparent conductive films (TCFs) based on these AgNWs without any post-treatment showed a very low sheet resistance of 4.7 Ω sq⁻¹, a low haze of 1.08% at a high optical transmittance of 95.2% (at 550 nm), and a high figure of merit (FOM) of 1210. TCFs exhibited a robust electrical performance with almost unchanged resistance after 2500 bending cycles. These excellent high-performance characteristics demonstrate the enormous potential of our AgNWs in the field of flexible and transparent materials.

Synthesis of corrugated surface AgNWs and their applications in surface enhanced Raman spectroscopy

Among metals, AgNWs are considered to be excellent materials for use in surface enhancement Raman spectroscopic (SERS) sensing due to their superior electrical properties, strong electromagnetic field generation and strong enhancement intensity.

Understanding the Effects of NaCl, NaBr and Their Mixtures on Silver Nanowire Nucleation and Growth in Terms of the Distribution of Electron Traps in Silver Halide Crystals

In recent years, many research groups have synthesized ultra-thin silver nanowires (AgNWs) with diameters below 30 nm by employing Cl⁻ and Br⁻ simultaneously in the polyol process. However, the yield of AgNWs in this method was low, due to the production of Ag nanoparticles (AgNPs) as an unwanted byproduct, especially in the case of high Br⁻ concentration. Here, we investigated the roles of Cl⁻ and Br⁻ in the preparation of AgNWs and then synthesized high aspect ratio (up to 2100) AgNWs in high yield (>85% AgNWs) using a Cl⁻ and Br⁻ co-mediated method. We found that multiply-twinned particles (MTPs) with different critical sizes were formed and grew into AgNWs, accompanied by a small and large amount of AgNPs for the NaCl and NaBr additives, respectively. For the first time, we propose that the growth of AgNWs of different diameters and yields can be understood based on the electron trap distribution (ETD) of the silver halide crystals. For the case of Cl⁻ and Br⁻ co-additives, a mixed silver halide crystal of AgBr_1−xCl_x was formed, rather than the AgBr/AgCl mixture reported previously. In this type of crystal, the ETD is uniform, which is beneficial for the synthesis of AgNWs with small diameter (30~40 nm) and high aspect ratio. AgNW transparent electrodes were prepared in air by rod coating. A sheet resistance of 48 Ω/sq and transmittance of 95% at 550 nm were obtained without any post-treatment.

Practical mediated-assembly synthesis of silver nanowires using commercial Camellia sinensis extracts and their antibacterial properties

Camellia sinensis is a well-known plant used for health purposes due to its high phenolic compound content and antioxidant properties.

Easily fabricated and lightweight PPy/PDA/AgNW composites for excellent electromagnetic interference shielding

Conductive polymer composites (CPCs) containing nanoscale conductive fillers have been widely studied for their potential use in various applications. In this paper, polypyrrole (PPy)/polydopamine (PDA)/silver nanowire (AgNW) composites with high electromagnetic interference (EMI) shielding performance, good adhesion ability and light weight are successfully fabricated via a simple in situ polymerization method followed by a mixture process. Benefiting from the intrinsic adhesion properties of PDA, the adhesion ability and mechanical properties of the PPy/PDA/AgNW composites are significantly improved. The incorporation of AgNWs endows the functionalized PPy with tunable electrical conductivity and enhanced EMI shielding effectiveness (SE). By adjusting the AgNW loading degree in the PPy/PDA/AgNW composites from 0 to 50 wt%, the electrical conductivity of the composites greatly increases from 0.01 to 1206.72 S cm^-1, and the EMI SE of the composites changes from 6.5 to 48.4 dB accordingly (8.0-12.0 GHz, X-band). Moreover, due to the extremely low density of PPy, the PPy/PDA/AgNW (20 wt%) composites show a superior light weight of 0.28 g cm^-3. In general, it can be concluded that the PPy/PDA/AgNW composites with tunable electrical conductivity, good adhesion properties and light weight can be used as excellent EMI shielding materials.

Fabrication of Nanostructures with Bottom-up Approach and Their Utility in Diagnostics, Therapeutics, and Others

Nanofabrication has been a critical area of research in the last two decades and has found wide-ranging application in improvising material properties, sensitive clinical diagnostics, and detection, improving the efficiency of electron transport processes within materials, generating high energy densities leading to pulse power, novel therapeutic mechanisms, environmental remediation and control. The continued improvements in the various fabrication technologies have led to realization of highly sensitive nanostructure-based devices. The fabrication of nanostructures is in principle carried out primarily using top-down or bottom-up approaches. This chapter summarizes the important bottom-up nanofabrication processes for realizing nanostructures and also highlights the recent research conducted in the domain of therapeutics and diagnostics.

Template-Free Electroless Plating of Gold Nanowires: Direct Surface Functionalization with Shape-Selective Nanostructures for Electrochemical Applications

Metal nanowires (NWs) represent a prominent nanomaterial class, the interest in which is fueled by their tunable properties as well as their excellent performance in, for example, sensing, catalysis, and plasmonics. Synthetic approaches to obtain metal NWs mostly produce colloids or rely on templates. Integrating such nanowires into devices necessitates additional fabrication steps, such as template removal, nanostructure purification, or attachment. Here, we describe the development of a facile electroless plating protocol for the direct deposition of gold nanowire films, requiring neither templates nor complex instrumentation. The method is general, producing three-dimensional nanowire structures on substrates of varying shape and composition, with different seed types. The aqueous plating bath is prepared by ligand exchange and partial reduction of tetrachloroauric acid in the presence of 4-dimethylaminopyridine and formaldehyde. Gold deposition proceeds by nucleation of new grains on existing nanostructure tips and thus selectively produces curvy, polycrystalline nanowires of high aspect ratio. The nanofabrication potential of this method is demonstrated by producing a sensor electrode, whose performance is comparable to that of known nanostructures and discussed in terms of the catalyst architecture. Due to its flexibility and simplicity, shape-selective electroless plating is a promising new tool for functionalizing surfaces with anisotropic metal nanostructures.

One-Pot Synthesis and Purification of Ultralong Silver Nanowires for Flexible Transparent Conductive Electrodes

Metal nanowires (NWs) have become the most promising candidates for the next generation of flexible transparent conductive electrodes (FTCEs), with high transmittance and low sheet resistance. In this work, ultralong silver NWs (Ag NWs), ∼220 μm (even larger than 400 μm) in length and ∼55 nm in diameter (aspect ratio: ∼4000), were synthesized via a one-pot polyol process using high molecular weight poly(vinylpyrrolidone) (M_w = 1 300 000) and an appropriate concentration of FeCl₃ (12.5 μM) through hydrothermal reaction. The prepared Ag NWs were purified by a filter cloth (pore size: about 30 × 50 μm²) to remove the Ag nanoparticles and short-length Ag NWs. The FTCE based on the ultralong Ag NWs without any post-treatments exhibits low sheet resistance of 155.0 Ω sq^-1 and transmittance of 97.70% at 550 nm. The outstanding performance of FTECs demonstrated that the ultralong Ag NWs are ideal materials for applications in flexible transparent optical devices.

Synthesis and highly effective purification of silver nanowires to enhance transmittance at low sheet resistance with simple polyol and scalable selective precipitation method

The high quality transparent conducting film (TCF) at a low sheet resistance of uniform and purified silver nanowires (AgNWs) have been successfully produced, the optoelectronic performance, which exceeds that of indium tin oxide (ITO).

One-pot stirring-free synthesis of silver nanowires with tunable lengths and diameters via a Fe3+ & Cl- co-mediated polyol method and their application as transparent conductive films

The properties of nanomaterials are highly dependent on their size, shape and composition. Compared with zero-dimensional nanoparticles, the increased dimension of a one-dimensional silver nanowire (AgNW/Ag NW) leads to extra challenges on synthesizing it with controllable sizes. Here, a convenient way for the synthesis of AgNWs with tunable sizes has been developed simply by adjusting the amount of salt additives, i.e., ferric chloride (FeCl₃), or Fe(NO₃)₃ & KCl. The average diameter and length of nanowires are readily tailored within 45-220 nm and 10-230 μm, respectively. The distinctive roles of Fe³⁺ and Cl^- played during the growth stages of Ag NWs were revealed by comparative experiments and a heterogeneous nucleation model with the assistance of oxidative etching was proposed to elucidate the growth mechanism. Afterwards, transformations in XRD patterns from nanometer-size effects and quantitative relation for size-dependent peak wavelength of surface plasmon resonances (SPRs) in UV-vis spectroscopy of these nanowires were studied. In addition, as transparent conductive materials (TCMs), these metal nanowires were utilized to fabricate transparent conductive films (TCFs), and the effects of their diameters and lengths were elucidated. Very/ultra-long nanowires with a high aspect ratio up to 1600 achieved impressive properties of R = 12.4 ohm sq^-1 at T% = 90.1% without any post treatment. This facile method for the size-tunable growth of uniform AgNWs with high yield is attractive and ready to be home-made, which is believed to promote research in their potential applications, especially in optoelectronic devices and flexible electronics.

Highly Effective Electromagnetic Interference Shielding Materials based on Silver Nanowire/Cellulose Papers

We fabricated silver nanowire (AgNW)-coated cellulose papers with a hierarchical structure by an efficient and facile dip-coating process, and investigated their microstructures, electrical conductivity and electromagnetic interference (EMI) shielding effectiveness. SEM images confirm that AgNWs are coated dominantly on the paper surfaces, although they exist partially in the inner parts of the cellulose papers, which demonstrates that the AgNW density gradually decreases in thickness direction of the AgNW/cellulose papers. This result is supported by the anisotropic apparent electrical conductivity of the AgNW/cellulose papers depending on in-plane or thickness direction. Even for a AgNW/cellulose paper obtained by a single dip-coating cycle, the apparent electrical conductivity in the in-plane direction of 0.34 S/cm is achieved, which is far higher than the neat cellulose paper with ∼10(-11) S/cm. In addition, the apparent electrical conductivity of the papers in the in-plane direction increases significantly from 0.34 to 67.51 S/cm with increasing the number of dip-coating cycle. Moreover, although the AgNW/cellulose paper with 67.51 S/cm possesses 0.53 vol % AgNW only, it exhibits high EMI shielding performance of ∼48.6 dB at 1 GHz. This indicates that the cellulose paper structure is highly effective to form a conductive AgNW network. Overall, it can be concluded that the AgNW/cellulose papers with high flexibility and low density can be used as electrically conductive components and EMI shielding elements in advanced application areas.

Solvothermal fabrication of thin Ag nanowires assisted with AAO

Silver nanowires were synthesized using solvothermal method assisted with AAO. AAO here is playing a role as a heterogeneous medium that can promote PVP molecules to form into one dimensional template and thus guiding the growth of Ag nanowires.

Large scale preparation of silver nanowires with different diameters by a one-pot method and their application in transparent conducting films

Silver nanowires (AgNWs) with varied diameters were synthesized by a facile and efficient one-pot polyol method. Each run of the reaction with this method can provide more than 10 g of AgNWs.

Growth Mechanism and Electrical and Magnetic Properties of Ag-Fe₃O₄ Core-Shell Nanowires

One-dimensional Ag-Fe3O4 core-shell heteronanowires have been synthesized by a facile and effective coprecipitation method, in which silver nanowires (AgNWs) were used as the nucleation site for growth of Fe3O4 in aqueous solution. The size and morphology control of the core-shell nanowires were achieved by simple adjustments of reaction conditions including FeCl3/FeCl2 concentration, poly(vinylpyrrolidone) (PVP) concentration, reaction temperature, and time. It was found that the Fe3O4 shell thickness could be tuned from 6 to 76 nm with the morphology variation between nanopheres and nanorods. A possible growth mechanism of Ag-Fe3O4 core-shell nanowires was proposed. First, the C═O derived from PVP on the surface of AgNWs provided nucleation points and in situ oxidation reaction between AgNWs and FeCl3/FeCl2 solution promoted the accumulation of Fe(3+) and Fe(2+) on the AgNWs surface. Second, Fe3O4 nanoparticles nucleated on the AgNWs surface. Lastly, Fe3O4 nanoparticles grew on the AgNWs surface by using up the reagents. Higher FeCl3/FeCl2 concentration or higher temperature led to faster nucleation and growth, resulting in the formation of Fe3O4 nanorods, whereas lower concentration or lower temperature resulted in slower nucleation and growth, leading to the formation of Fe3O4 nanospheres. Furthermore, the Ag-Fe3O4 core-shell nanowires exhibited good electrical properties and ferromagnetic properties at room temperature. Particularly, the magnetic saturation values (Ms) increased from 5.7 to 26.4 emu g(-1) with increasing Fe3O4 shell thickness from 9 to 76 nm. This growth of magnetic nanoparticles on 1D metal nanowires is meaningful from both fundamental and applied perspectives.

Ultralightweight silver nanowires hybrid polyimide composite foams for high-performance electromagnetic interference shielding

Ultralightweight silver nanowires (AgNWs) hybrid polyimide (PI) composite foams with microcellular structure and low density of 0.014-0.022 g/cm(3) have been fabricated by a facile and effective one-pot liquid foaming process. The tension flow generated during the cell growth induced the uniform dispersion of AgNWs throughout the cell walls. The interconnected AgNWs network in the cell walls combined with the large 3D AgNWs network caused by 3D structure of foams provided fast electron transport channels inside foams. The electromagnetic interference (EMI) shielding effectiveness (SE) of these foams increased with increasing AgNWs loading as well as the nanowire aspect ratio due to the increasing connections of the conduction AgNWs network. Appropriate surface treatment like etching or spraying facilitated the construction of the seamlessly interconnected 2D AgNWs network on the surface, which could effectively reflect electromagnetic waves. Maximum specific EMI SE of values of 1210 dB·g(-1)·cm(3) at 200 MHz, 957 dB·g(-1)·cm(3) at 600 MHz, and 772 dB·g(-1)·cm(3) at 800-1500 MHz were achieved in sprayed composite foams containing <0.044 vol % AgNWs loading, which far surpasses the best values of other composite materials. The reflections of interconnected AgNWs networks on the surface and inside foams combined with the multiple reflections at interfaces contributed to the shielding effect.

A comparative study of structure and electromagnetic interference shielding performance for silver nanostructure hybrid polyimide foams

Comparison of structure and electromagnetic interference shielding performance for silver nanostructures hybrid polyimide foams.