Silver Nanowires Research Articles

Heterogeneous nucleation optimization from AgCl and reduction control in ethylene glycol for fast and reproducible synthesis of silver nanowires

Silver nanowires synthesized by the most commonly used polyol method are typically accompanied by nanoparticles and nanorods, which have a negative impact on the performance of silver nanowire-based devices. Herein, we report a reproducible and easy method for preparing silver nanowires with yields exceeding 70% by optimizing the heterogeneous nucleation of silver from silver chloride precursors and regulating the reduction in ethylene glycol. The yield of silver nanowires depended on the morphology and concentration of silver chloride and the decomposition time of ethylene glycol. The Raman spectra were used to study the effect of the decomposition time of ethylene glycol on the concentration of acetaldehyde in solution, which influenced the reduction rate of silver ions. Then, the reaction time of silver nanowires was further reduced from 24 min to 10 min by increasing the reaction temperature from 160 °C to 170 °C. On the basis, the silver nanowire based capacitive screen with a good capacitive response and anti-aging performance was further fabricated. This method provides a new way for the macro preparation of silver nanowires with high yields.

Ecofriendly cellulose substrate based flexible transparent electrode for flexible organic solar cells with efficiency over 18%

Flexibility is a key advantage of organic solar cells (OSCs), and the power conversion efficiencies (PCEs) of flexible OSCs (FOSCs) are primarily constrained by flexible transparent electrodes (FTEs). While much attention has been devoted to the study of conductive layers on FTEs, the importance of flexible substrates in influencing the properties of FTEs and the performance of FOSCs is often overlooked. In this study, we have developed an FTE using an eco‐friendly ethyl cellulose (EC) substrate and silver nanowires (AgNWs) as the conductive electrode. The FTE exhibits a high transmittance of up to 88% at 550 nm and a low sheet resistance of 17.65 Ω/□. Consequently, FOSCs based on the EC/PI FTEs achieved a remarkable PCE of 18.05%, comparable to that on the rigid ITO substrate. The flexible devices also demonstrated excellent bending and peeling durability even under extreme bending conditions.This article is protected by copyright. All rights reserved.

Fabrication of Flexible and Conductive Microneedle Array Electrodes from Silk Fibroin by Mesoscopic Engineering

AbstractConventional electrodes are of significant challenges in acquiring bioelectric signals concerning a high signal‐to‐noise ratio (SNR), long‐term and comfortable wear, low motional noise, etc. To resolve these issues, silk fibroin (SF) materials are adopted to create flexible microneedle array electrodes (FMNA‐electrode) based on meso‐engineering. The research approaches involve constructing flexible conductive electrodes from non‐conductive and bristle‐regenerated SF. By controlling the molecular interchain nucleation in the refolding process of unfolded regenerated SF molecules, this goal can be achieved. In this process, silver nanowires (Ag NWs) are adopted as meso‐dopants to reconstruct the meso‐electronic structure of SF films at the surface, while polyurethane (PU) is selected as molecular templates to facilitate the molecular nucleation in the refolding of SF molecules. This leads to the occurrence of SF‐PU meso‐hybridization, giving rise to more flexible meso‐hybridized SF. The SF‐PU FMNA‐electrode demonstrates biocompatibility, comfort wearing, long‐term monitoring capability, low motional noise, and a high SNR in the application of collecting ECG, EMG, and EOG signals. The outperformance of SF‐PU FMNA‐electrode is superior to both conventional wet and commercially available dry electrodes, paving the way for the next generation of flexible, skin‐friendly, durable, and high‐performance health monitoring devices and brain‐machine interfaces.

Nanocellulose-Enhanced, Easily Processable Cellulose-Based Flexible Pressure Sensor for Wearable Epidermal Sensing.

Flexible pressure sensors (FPSs) based on biomass materials have gained considerable attention for their potential in wearable electronics, human-machine interaction, and environmental protection. Herein, flexible silver nanowire-dual-cellulose paper (SNdCP) containing common cellulose fibers, cellulose nanofibers (CNFs), and silver nanowires (AgNWs) for FPSs was assembled by a facile papermaking strategy. Compared with bacterial cellulose (BC) and cellulose nanocrystals (CNCs), CNFs possess better dimensions and reinforcement, which enables the composite paper to exhibit better mechanical properties (tensile stress of 164.65 MPa) and electrical conductivity (11600 S·m-1), providing more possibilities for FPSs. Benefiting from these advantages, we construct an easily processable and sensitive human-interactive FPS based on a composite paper with high sensitivity (0.050 kPa-1), fast response/recovery time (158/95 ms), and exceptional stability (>1000 bending cycles), capable of responding to finger motions, voice recognition, and human pulses; through further employment as the array unit and a control circuit, the observed highly adaptive mechano-electric transformability and functions are well maintained. Overall, a facile and versatile strategy with the potential to provide clues for the fabrication of cellulose-based FPSs with outstanding performance was introduced.

Highly Transparent and Flexible Multi‐Walled Carbon Nanotubes‐Polyimide Films with Enhanced Electrical Performance as Promising Electrodes

AbstractTransparent and light films with high electrical conductivity are preferred for flexible electronic applications. In this work, a film exhibiting high transparency, electrical conductivity, and flexibility is produced using a polyimide (PI) substrate and multi‐walled carbon nanotubes (MWCNTs) through spray coating. Cost‐effective MWCNTs are used instead of other electrically conductive materials, including silver nanowire (AgNW) ink, SWCNTs, and other carbon materials. The average sheet resistance of the prepared MWCNT‐PI film is 520.2 Ω/□ (infinite for the bare PI film), which is lower than the sheet resistances of the SWCNT‐PI film reported by another group. This could be attributed to the increase in electrical conductivity of the highly transparent PI film due to the use of MWCNTs. The transparency of the MWCNT‐PI film is 71.834% at 550 nm. When MWCNTs and PI are combined, MWCNTs protrude from the surface of the PI film, creating networks and increasing electrical conductivity. Atomic force microscopy analysis revealed that MWCNT networks formed on the surface of the MWCNT‐PI film. This study suggests the possibility that MWCNTs can also be used as carbon materials for flexible and highly transparent films. Ω/□This article is protected by copyright. All rights reserved

Stretchable Electrodes with Interfacial Percolation Network.

Stretchable electrodes are an essential component that determines the functionality and reliability of stretchable electronics, but face the challenge of balancing conductivity and stretchability. Here, we propose a new conducting concept called the interfacial percolation network (PN) that results in stretchable electrodes with high conductivity, large stretchability, and high stability. The interfacial PN was composed of a two-dimensional (2D) PN and a protruding PN embedded on the surface and in the near-surface region of an elastic polymer matrix, respectively. The protruding PN was the key design to intimately link the 2D conducting channels on the surface of the elastomer with the 3D conducting channels in the bulk of the elastomer. The protruded PN was obtained by changing the arrangements of silver nanowires (AgNWs) from horizontal to quasi-vertical through introducing foreign polymer domains in the near-surface region of the polymer matrix. The resulting electrode achieved a conductivity of 13,500 S cm-1 and a stretchability of up to 660%. Its resistance changes (i.e., R/R0) under stretched conditions were orders of magnitude lower than those of conventional 2D PN and 2D + 3D PN. This electrode performed stability in various physicochemical conditions, including being soaked in acid and alkaline solutions for 20 days, heated at 80°C for 10 days, stretched to 80% for 10000 cycles, and scratched by a sharp needle. The concept of interfacial PN was broadly applicable to common conductors used in stretchable electronics, such as graphene, gold film, Ag film, and liquid metal. The conductivity of the interfacial PN electrode made from liquid metal remained at 46,750 S cm-1 after the electrode underwent multiple stretch-release cycles with a deformation of >600%. The concept of interfacial PN provides fruitful implications for the design of stretchable electronics. This article is protected by copyright. All rights reserved.

Robust ZTO reinforced AgNW hybrid transparent conductive thin films with absorption-enhanced EMI shielding property.

Evolving technology advancements has accelerated the pursuit of transparent conducting thin films (TCF) with superior mechanical properties, durability, efficient opto-electrical performance and substrate compatibility as a pivotal focus in the realm of flexible transparent electronics. With this concern, this work delves the fabrication of multilayer silver nanowire (AgNW) thin films reinforced by zinc tin oxide (ZTO) thin film encapsulation on polycarbonate substrates by the combination of sputtering and spin-coating techniques. Investigation on the influence of AgNW percolation networks on the opto-electrical properties of ZTO/AgNW/ZTO hybrid thin films was carried out. The impact of ZTO protective layers on the enhancement of electrical properties, adhesivity, flexibility and environmental stability of the multilayer TCF was elucidated. Additionally, to explore the compatibility of the fabricated TCF in integrated device and stealth applications, its electromagnetic interference (EMI) shielding property was investigated. The hybrid TCF showed 99.47% EMI shielding efficiency with absorption-dominant EMI shielding effectiveness of 22.7 dB in the x-band region.&#xD.

Flexible Sandwich-Shaped Cellulose Nanocrystals/Silver Nanowires/MXene Films Exhibit Efficient Electromagnetic-Shielding Interference Performance.

The electromagnetic pollution problem is becoming increasingly serious due to the speedy advance of electronic communication devices. There are broad application prospects for the development of flexible, wearable composite films with high electromagnetic interference (EMI)-shielding performance. The MX@AC composite films were prepared from MXene, silver nanowires (AgNWs) and cellulose nanocrystals (CNCs) with a sandwich structure. Benefiting from the upper and lower frame structure formed by winding 1D AgNWs and CNC, the tensile strength of the MX@AC was improved to 35 MPa (12.5 wt% CNC content) from 4 MPa (0 wt% CNC content). The high conductivity of MXene and AgNWs resulted in the MX@AC composite film conductivity up to 90,670 S/m, EMI SE for 90 dB, as well as SSE/t up to 7797 dB cm2 g-1. And the MX@AC composite film was tested for practical application, showing that it can effectively isolate electromagnetic waves in practical application.

Lightweight 3D Lithiophilic Graphene Aerogel Current Collectors for Lithium Metal Anodes.

Constructing three-dimensional (3D) current collectors is an effective strategy to solve the hindrance of the development of lithium metal anodes (LMAs). However, the excessive mass of the metallic scaffold structure leads to a decrease in energy density. Herein, lithiophilic graphene aerogels comprising reduced graphene oxide aerogels and silver nanowires (rGO-AgNW) are synthesized through chemical reduction and freeze-drying techniques. The rGO aerogels with large specific surface areas effectively mitigate local current density and delay the formation of lithium dendrites, and the lithiophilic silver nanowires can provide sites for the uniform deposition of lithium. The rGO-AgNW/Li symmetric cell presents a stable cycle of about 2000 h at 1 mA cm-2. When coupled with the LiFePO4 cathode, the assembled full cells exhibit outstanding cycle stability and rate performance. Lightweight rGO-AgNW aerogels, as the host for lithium metal, can significantly improve the energy density of lithium metal anodes.

Preparation and characterization of electrospun silver nanowires/ZnO/PVP composite transparent conductive film

In this study, a silver nanowires (AgNWs)/nano-zinc oxide (ZnO)/polyvinylpyrrolidone (PVP) film is fabricated as an alternative to indium tin oxide transparent conductive films (TCFs). AgNWs are prepared by the polyol method with PVP as a dispersant to prevent Ag nanoparticles agglomeration during AgNWs formation. Nano-ZnO is synthesized using sol–gel method. AgNWs/ZnO/PVP TCFs are prepared using the electrostatic spinning and spin coating methods for comparison. It is found that the best PVP/AgNO3 molar ratio is 3.5:1. FTIR and XRD analyses show that 500°C calcination leads to better crystallinity and purity of nano-ZnO. Four-point prober analysis indicates that the higher the AgNWs content, the lower the TCF sheet resistance. The best sheet resistance of AgNWs/ZnO/PVP TCF by the electrostatic spinning method is obtained as 81 [Formula: see text]/sq, and the light transmittance is 85.3%. Moreover, in the 5-week stability test, the sheet resistance of the electrospun TCF increases by 6.17%, much lower than 24.9% of the spin coated TCF. It is verified that the elecrospun AgNWs/ZnO/PVP composite TCF is a promising alternative to the traditional ITO TCFs.

Seed-Mediated Electrodeposition of Silver Nanowires and Nanorods.

Here, we compare the amount and morphology of silver (Ag) nanostructures electrodeposited at varied potentials and times in the presence of cetyltrimethylammonium bromide (CTAB) onto glass/indium tin oxide (glass/ITO) electrodes functionalized with mercaptopropyltrimethoxysilane (MPTMS) and coated or not coated with 4 nm average diameter Au nanoparticle (Au NP) seeds. There is a significantly larger amount of Ag deposited on the seeded electrode surface compared to that in the nonseeded electrode at potentials of -150 to -300 mV (vs Ag/AgCl) since the Au NP seeds act as catalysts for Ag deposition. At more negative overpotentials of -400 to -500 mV, the amount of Ag deposited on both electrodes is similar because the deposition kinetics are fast enough on glass/ITO that the Au seed catalyst does not make as big of a difference. Ag nanorods (NRs) and nanowires (NWs) form on the seeded surfaces, especially at more positive potentials, where deposition primarily occurs on the Au seed catalysts. Deposition of Ag onto the Au seeds appears as a separate peak in the voltammetry. This procedure mimics the seed-mediated growth of Ag NRs observed in solution in the presence of CTAB using ascorbic acid as a reducing agent. The yield, length, and aspect ratio of the Ag NRs/NWs depend on the deposition time and potential with the average length ranging from 300 nm to 3 μm for times of 30-120 min and potentials of -150 to -200 mV. The electrochemical seed-mediated growth of Ag NRs/NWs across electrode gaps could find use for resistive and surface-enhanced Raman-based sensing and molecular electronic applications.

Silver nanowire bridged graphene framework for encapsulating phase change materials with high thermal conductivity and solar-to-heat conversion ability

To construct a high-efficiency thermally conductive graphene nanoplate (GNP) framework, ball-milling technique and silver nanowires (AgNW) bridging strategy were employed to improve the compatibility of GNP and the interfacial thermal resistance (ITR) in GNP skeletons, respectively. By using unidirectionally freeze casting technique, long range ordered GNP frameworks containing a small amount of AgNW as “bridge” were obtained, which were used to encapsulation phase change material (PCM). As a result, the honeycomb-like micropores of the framework with strong capillary effect give PCM anti-leakage and shape stability. The vertically aligned and AgNW bridged GNP skeletons form high-speed heat transfer paths endowith low ITR, thus significantly improve thermal conductivity to 7.24 W/mK. More importantly, GNP framework with strong light absorption ability endows PCM with well solar-to-heat conversion and storage ability. Therefore, AgNW bridged GNP framework endowing PCM with comprehensive thermal management ability exhibits a high potential in addressing the thermal problems of electronics.

Optimizing Silver Nanowire Synthesis for In-Body Applications

Optimizing Silver Nanowire Synthesis for In-Body Applications

Synthesis and Reduction Processes of Silver Nanowires in a Silver(I) Sulfamate-Poly (Vinylpyrrolidone) Hydrothermal System.

Silver (Ag) nanowires, as an important one-dimensional (1D) nanomaterial, have garnered wide attention, owing to their applications in electronics, optoelectronics, sensors, and other fields. In this study, an alternative hydrothermal route was developed to synthesize Ag nanowires via modified reduction of Ag+. Silver sulfamate plays an important role in the formation of Ag nanowires via controlled release of free Ag+. Results of controlled experiments and characterizations such as UV-vis spectroscopy, FTIR, XPS, and 1H NMR revealed that sulfamic acid does not function as a reductant, supporting by the generation of free Ag+ instead of Ag nanostructures in hydrothermally treated silver sulfamate solution. The initial reduction of Ag+ was induced by the combination of poly (vinylpyrrolidone) (PVP) end group and degradation products. This phenomenon was supported by abundant free Ag+ in the mixed preheated silver sulfamatic and preheated PVP aqueous solutions, indicating a second and distinct Ag+ autocatalytic reduction. Thus, the roles of different reagents and Ag+ reduction must be studied for nanomaterial syntheses.

Stretchable Multifunctional Polydimethylsiloxane Composites with Cage‐Like Conductive Architecture for Integrated Thermosensitive and Electromagnetic Interference Shielding Performance

AbstractHigh‐performance sensors with outstanding sensitivity, wide working range, and multifunctional properties are highly desirable in modern integrated smart wearable electronics. Herein, polydimethylsiloxane (PDMS)‐based stretchable pyroresistive sensors composed of tightly‐assembled silver nanowires (Ag NWs)‐encapsulated PDMS microspheres (PM) and expandable microspheres (EM) are fabricated. The synergistic cage‐like conductive network and EM endow the temperature sensor with tunable sensitivity (Max TCR: 27.4% °C−1), broad sensing range (25–85 °C), low perception limit (0.1 °C), and excellent anti‐interference ability. Interestingly, at elevated temperature field (> 90 °C), a remarkable conduction‐insulation transition is observed, which is employed to facilitate an early fire alarm system. In addition, the selectively distributed Ag NWs constructs segregated conductive pathways at an ultralow content (Pc = 0.014 vol%), leading to efficient electromagnetic interference shielding (40.0 dB). The underlying mechanism responsible for the observed superior thermosensation and EMI shielding performance is elucidated, and possible applications are demonstrated. Consequently, this work offers a novel strategy for the design of flexible, multifunctional pyroresistive sensors toward artificial intelligence and emerging wearable electronics.

Layer-stacked polyaniline/silver nanowire composite film for multicolor electrochromic smart windows with dual-band optical modulation

Dual-band electrochromic smart windows (DESWs) have attracted widely concern for their potential in significantly reducing building energy consumption by selectively controlling near-infrared (NIR) and visible light (VIS) transmittance. However, its monotonous color changes limit its large-scale application. In this study, we designed a DESW based on the layer-stacked polyaniline (PANI)/silver Nanowires (Ag NWs) composite films. When PANI films is stacked layer by layer with Ag NWs, it not only performs dual band regulation, but also exhibits impressive electrochromic performance with rich color conversions (light yellow, yellow-green and blue-black). The four-layer PANI/Ag NWs composite film outperformed the pure single-layer PANI film because of the faster electron transfer, its coloring time and bleaching time at 525 nm were shortened to 6.7 s and 18.0 s, respectively, and the coloring efficiency was increased to 45.5 cm2 C-1. After 2500 cycles, the PANI/Ag NWs films tend to have better cycle stability. Therefore, the incorporation of Ag NWs enhances the electrochromic performance of PANI films, providing valuable insights for advancing single-component organic electrochromic materials.

Polyethyleneimine Controlled Impregnation of Silver Nanowires on Electrospun Ceramic Sponges

AbstractElectrospun sponges with electrical conductivity are promising materials for electrodes with applications in pressure sensors, flexible wearable sensors, and supercapacitors. However, electrospun sponges display poor electric conductivity, which can be increased by the addition of silver nanowire (AgNW). The resulting electric conductivity may depend strongly on the distribution of the AgNW in and on the sponges. A straightforward assembly method for an elastic conductive sponge, composed of 3D structures and metal nanowires, using a synergistic strategy which involves modified impregnation and deposition processes assisted by polyethyleneimine (PEI) impregnation, is presented. The resulting changes in the material properties are also explored, and it is under specific conditions, that percolation, leading to significantly enhanced electrical conductivity in the sponges, is achieved.

Highly Sensitive and Breathability Flexible Piezoresistive Pressure Sensor Based on Xylon

AbstractIn recent years, the prevalence of cervical spondylosis has been increasing, which is associated with unhealthy posture in daily life, flexible pressure sensors are beneficial in preventing cervical spine disorders. This work is dedicated to developing a flexible, high‐performance, and breathable device to monitor the health of the neck. Here, a flexible pressure sensor with a “sandwich” structure is presented, which incorporates patterned xylon fabric as the substrate and MXene as the sensitive layer. Furthermore, the application of silver nanowires (AgNWs) as the electrode material improves the piezoresistive performance. Combined with an internal elastic encapsulation method (IEEM), the sensor exhibits high sensitivity (1417.9 kPa−1 under pressure below 100 kPa) and a fast response time (30.77 ms). Compared with traditional flexible pressure sensors, the breathability of devices with an all‐fiber structure is nearly seven times higher, which better satisfies the monitoring requirements of long‐term wear. Finally, a wireless system is established by integrating a Bluetooth module and a terminal app. It enables monitoring and sensing of various physiological signals of the neck, as well as identification and alerting of long‐term poor posture such as prolonged neck flexion, showing a potential candidate for the applications of the next‐generation wearable device.

High-performance composite transparent electrode composed of ultra-long silver nanowires and antimony-doped tin oxide nanoparticles

Abstract Composite transparent conductive electrodes (TCEs) consisting of silver nanowires (AgNWs) and conductive metal oxides are very promising for flexible optoelectronic devices due to their smooth surface morphology and high chemical stability. However, it is still challenging to ensure high optoelectronic performance and long-term stability in practical applications. Here, we solved these problems by coating antimony-doped tin oxide (ATO) nanoparticles dispersion on ultra-long AgNWs network using waterborne polyurethane (WPU) binder. Ultra-long nanowires occupy less wire-wire junctions and space than short nanowires, thus increasing the optoelectronic performance and flexibility of the composite TCE. WPU improves the adhesion and stability of ATO nanoparticles to the substrate and AgNWs network. The fabricated composite TCE showed a low sheet resistance of 11.9 Ω/sq, good optical transmittance of 83% at 550 nm and a figure of merit (FOM) of 162 compared to PET/ITO electrode. It also showed excellent mechanical flexibility, adhesion to the substrate and solvent stability. Furthermore, the long-term conductivity was maintained under ambient conditions for 60 days.

Deformable Joule Heating Electrode Based on Hybrid Layers of Silver Nanowires and Carbon Nanotubes and its Application in a Refreshable Multi‐Cell Braille Display

AbstractJoule heating electrodes (JHEs) are required for thermal actuation systems. A highly stretchable, patternable, and low‐voltage operating JHE based on hybrid layers of silver nanowires and carbon nanotubes are reported. The conductive layers are applied on a locally pre‐strained bistable electroactive polymer (BSEP) membrane to form a wrinkled conductive surface with a low resistance of 300 Ω/sq, and subsequently patterned to a serpentine trace by laser engraving. The resistance of the resulting JHE electrode remains nearly unchanged up to 80−90% area strain. By applying a voltage of 7 − 9 V to the electrode, the temperature of the BSEP membrane increased to ~60 °C, well above the polymer's phase transition temperature of 46 °C, thereby lowering its modulus by a factor of 103. An electronic Braille device based on the JHEs on a BSEP membrane is assembled with a diaphragm chamber. The electrode is patterned into 3 × 2 individually addressable pixels. Through Joule heating of the pixels and local expansion of the BSEP membrane using a pneumatic pressure, the pixels deformed out of the plane by over 0.5 mm to display Braille letters. The Braille content can be refreshed for 20 000 cycles at the same operating voltage.