Ultra-long Silver Research Articles

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

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−1, 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.

Room temperature high-efficiency welding of an ultra-long silver nanowire network for flexible transparent electrodes.

In the preparation of flexible electronic devices, obtaining a transparent conductive electrode with high electrical conductivity, high transparency, and mechanical flexibility is a significant challenge. This study developed a simple method for preparing ultra-long silver nanowires (ul-AgNWs), obtaining high-purity ul-AgNWs with an average length of 317.66 ± 98.60 μm, an average diameter of 78.06 ± 13.87 nm, and an aspect ratio exceeding 4000. Integrating these ul-AgNWs with a polyethylene terephthalate (PET) film, a flexible transparent electrode (FTE) with Rs = 561 Ω and T = 97% was obtained. The ul-AgNWs were welded by driving the welding liquid to the intersection points through surface tension, resulting in a decrease of Rs to 61 Ω, T = 98.2%, and achieving a FTE with excellent mechanical properties. Furthermore, this FTE was applied in the preparation of OLED devices, showing a turn-on voltage of 2.7 V, and the maximum current efficiency and power efficiency reached 58.6 mA cm-2 and 64.7 lm W-1, respectively, demonstrating its significant potential in flexible optoelectronic devices.

Highly Selective Welding of Ultralong Silver Nanowire Transparent Conductive Electrodes by Electroplating

Highly Selective Welding of Ultralong Silver Nanowire Transparent Conductive Electrodes by Electroplating

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.

Facile macro fabrication of ultra-fine, ultra-long silver nanowire and growth mechanism

Silver nanowire (AgNWs) with a fine diameter (< 20 nm) and large aspect ratio (>1000) is one of the requirements for good optoelectronic properties of a transparent conductive film. Herein we report a facile and high yield modified polyol synthesis of AgNWs with average diameters of ∼ 17 nm, aspect ratios up to 2600. And the synthesized AgNWs were applied in flexible transparent conductive films (TCF). Some crucial factors, such as illumination, solvent, and stirring impacting the diameter, and yield of AgNWs were discussed in detail. Illumination is the main factor that impact the yield of AgNWs. The probable growth mechanism of AgNWs was proposed. The sheet resistance of the AgNWs was 92 Ω/sq and the transmittance and haze were 90 % and 1.74 %, respectively.

Centrifugal Spinning Enables the Formation of Silver Microfibers with Nanostructures.

Silver nanowires (AgNWs) have received much attention and application in transparent electrodes, wearable electronic devices, and sensors. The hope is for these nanowires to eventually replace the most commonly used transparent electrode material—indium tin oxide (ITO). However, electrospinning used for the preparation of AgNWs on a large scale is limited by its low productivity and high electric field, while the alcohol-thermal method is limited to mixing by-product silver nanoparticles in silver nanowires. We demonstrate a novel and simple centrifugal spinning approach in order to successfully fabricate ultra-long silver microfibers based on AgNO3 and polyvinyl pyrrolidone (PVP). The centrifugal-spun precursor fiber and silver fiber can be prepared to as thin as 390 and 310 nm, respectively. Annealed fibers show typical nanostructures with grains down to a minimum size of 51 nm. Combinations of different parameters, including concentrations of PVP, needle size, and annealing temperature are also investigated, in order to optimize the spinning process of ultra-long silver microfibers. The feasibility of preparing silver microfibers by centrifugal spinning is preliminarily verified, examining prospects for mass production. Furthermore, numerous strategies related to assisting the creation of silver nanofibers using centrifugal spinning are presented as possibilities in future development.

Highly Selective Welding of Ultralong Silver Nanowire Transparent Conductive Electrodes by Electroplating

Highly Selective Welding of Ultralong Silver Nanowire Transparent Conductive Electrodes by Electroplating

Ultra-long silver nanowires prepared via hydrothermal synthesis enable efficient transparent heaters.

Ultra-long silver nanowires (AgNWs) with an aspect ratio of >2000 were prepared by the hydrothermal synthesis method. The influence of reaction time (4-32 h), reaction temperature (150-180 °C), polyvinylpyrrolidone (PVP) molecular weight (10 000-1 300 000 g mol-1), PVP concentration (50-125 mM), glucose concentration (5.6-22.4 mM) and CuCl2 concentration (2-20 μM) on the AgNW length was investigated systematically. The optimum conditions provided nanowires with an average diameter of 207 nm, an average length of 234 μm and a maximum length of 397 μm. Finally, a AgNW electrode was prepared on a glass substrate and used in transparent heater application. The transparent heater enabled outstanding heat-generating properties, reaching >200 °C within 70 s with an applied voltage of 5 V. Our results demonstrate how increasing the aspect ratio of ultra-long AgNWs is beneficial for both optical and electronic applications in terms of increased transmission and a more efficient Joule effect in the heater application. In addition, our results show that AgNWs with different lengths can be simply obtained by tuning synthesis parameters.

Highly conductive thermoresponsive silver nanowire PNIPAM nanocomposite for reversible electrical switch.

Highly conductive nanocomposite hydrogels have been challenging to produce due to their high water volumes inhibiting the incorporation of an essential amount of conductive nanofillers. Furthermore, the most common fillers used, typically for easy integration, display small aspect ratios. Thus, the formation of interparticle pathways for electronic travel is limited, resulting in low conductivities. Here, we introduce ultralong silver nanowires (ULAgNWs) into a thermoresponsive, volume changing PNIPAM gel to form a nanocomposite that shows switchable electronic performance. The produced nanocomposite surpasses other PNIPAM nanocomposites by expressing the largest electrical switch ratio and the highest peak conductivity. The PNIPAM matrix possesses an interconnected microporous structure that offers a spacious network for the dispersion of nanowires while still maintaining a high volume switch ratio and excellent elastic behavior under extreme compression cycles (98% compression). The ULAgNWs significantly enhance the probability of more numerous connections forming during shrinking cycles. The high swellability displayed by the PNIPAM gel provides the ability to separate the embedded nanowires by many lengths. Together, they form a nanocomposite that can thermo-modulate its electrical properties. Moreover, the conductive PNIPAM maintains the electrical switch of 4.3-4.4 orders of magnitude with thermo-responsive cycles. Because of their high electrical conductivity and outstanding elastic behavior, these stimuli-responsive nanocomposite hydrogels may expand the prospects for conductive hydrogel applications and provide greater performance in their applications.

Strained Ultralong Silver Nanowires for Enhanced Electrocatalytic Oxygen Reduction Reaction in Alkaline Medium.

Many noble metals are efficient catalysts for oxygen reduction reaction (ORR), including silver (Ag). Among all these noble metals, Ag is the most affordable because of its relative abundance. Surface energy has been proven to play a crucial role in the catalytic process, and straining is an effective operation to raise the surface energy over electrocatalysts. In this work, sonication was utilized to induce strain in Ag nanowires (NWs) through lattice deformation. A 0.18 J/m2 improvement of the surface energy around the stacking faults area has been calculated via density functional theory. The diffusion-limiting current density was evaluated and increases by >20% (from -4.98 to -6.00 mA/cm2) after sonication straining. Meanwhile, the onset potential remains almost constant (i.e., 0.95 V vs RHE). The results show that induction of strain has a strong impact on the diffusion-limiting current density and significantly improves the ORR catalytic performance of Ag NWs.

A Silk Fibroin and Ultra-Long Silver Nanowires Based Transparent Conductive Composite Film for Nanosensor Devices

In addition to flexible touch screens, organic flexible photoelectric films have broad application prospects. In this paper, a transparent and conductive composite film was prepared by embedding a conductive network of ultra-long silver nanowires with silk fibroin as the substrate material. The ultra-long length can help minimize the number of junctions between the nanowires on the conductive grid, which can reduce greatly the resistance and optical shielding effect of the conductive layer. To tune the flexibility of the film, an appropriate amount of calcium ions (Ca2+) could be added to the silk fibroin solution. The conductivity, light transmittance, and temperature, stress and humidity sensitivity of the composite films were characterized and proved satisfactory. Its capability of self-healing was also demonstrated. With the natural biocompatibility and self-healing ability, this silk fibroin film may be applied in biomedical science, such as an electronic skin that can detect multiple human health indicators.

A one-step synthesis of ultra-long silver nanowires with ultra-high aspect ratio above 2000 and its application in flexible transparent conductive electrodes

Silver nanowires (AgNWs), appear as an extremely promising candidate for the next generation of flexible transparent conductive electrodes (FTCEs). However, the performance of AgNWs-FTCEs was severely limited by the aspect ratio of AgNWs, while it was still a big challenge to fabricate AgNWs with high aspect ratio nowadays. To improve the aspect ratio of AgNWs, bromide ion (Br−), cupric ion (Cu2+) and polyvinylpyrrolidone (PVP, Mw ≈ 1300 000) which are beneficial for the synthesis of high aspect ratio AgNWs, were introduced in this article. The high quality and uniform AgNWs with the average diameter of 77.6 nm and the aspect ratio above 2000 were fabricated via a one-step solvothermal method. The effects of reaction time, molar ratio of AgNO3 to PVP and the concentration of CuBr2 on the aspect ratio of AgNWs were discussed. The mechanism of the synthesis of high aspect ratio AgNWs was explored. After that, the prepared AgNWs were spin-coated on the surface of PET film, the FTCEs based on the ultra-high aspect ratio AgNWs without any post-treatments exhibits relatively high transmittance, low haze and low sheet resistance, and the AgNWs have little effect on the optical performance of pristine PET film. The outstanding performance of the prepared FTCEs indicated that the ultra-high aspect ratio AgNWs are ideal materials in the application of FTCEs, and the method of fabricating AgNWs could provide a direction to the high aspect ratio AgNWs.

Surfactant-free synthesis of ultralong silver nanowires for durable transparent conducting electrodes

The present study employed the surfactant-free growth of ultralong (∼50 μm) silver nanowires (AgNWs) with a high aspect ratio (more than 1000) by galvanic replacement. AgNW conducting films were fabricated as electrodes using drop-casting. The AgNW film had 90% transmittance to 550 nm light with a sheet resistance of 232 Ω sq-1. Further, the flexibility test of the transparent flexible AgNW/MoS2 device array indicated that the variation of the current was within 5% when a strain of 0.5% was applied to the device; additionally, the device showed a 13% decrease in current after experiencing 50 000 bending cycles. This study indicated that the ultralong AgNWs synthesized using galvanic replacement have potential for applications as transparent and flexible electrodes.

Morphology-controlled silver nanowire synthesis using a cocamidopropyl betaine-based polyol process for flexible and stretchable electronics.

Silver nanowire (AgNW) based transparent conductive films (TCFs) are promising building blocks for flexible and stretchable electronics to replace brittle metal oxides. Ultra-long AgNWs are preferred for enabling TCFs with excellent photoelectric properties and mechanical flexibility. Herein, a novel polyol process is proposed for the synthesis of ultra-long AgNWs, with the new finding that the addition cocamidopropyl betaine (CAB) to polyol synthesis allows the rapid production of AgNWs with an average length of ∼120 μm in a high yield of ∼90%. Also, a cocamidopropyl betaine assisted polyol method for the synthesis of ultra-long AgNWs is demonstrated with a possible mechanistic explanation. The prepared AgNWs are coated on a polyethylene glycol terephthalate (PET) substrate to fabricate a flexible transparent conductive film, which exhibits a low sheet resistance of ∼200 Ω sq−1 at 88.74% transmittance with a negligible change of sheet resistance after bending. In addition, flexible TCFs based on the resulting AgNWs reveal excellent mechanical flexibility and high cyclic stability after 300 cycles of bending. The new polyol process in this work will provide a greater possibility for the practical application of long AgNWs towards flexible and wearable optoelectronic devices.

Rapid synthesis of ultra-long silver nanowires for high performance transparent electrodes.

By using 1,2-propanediol instead of the classic polyol solvent, ethylene glycol, ultra-long silver nanowires are obtained in only 1 h. These nanowires lead to transparent electrodes with a sheet resistance of 5 Ohms per sq at a transparency of 94%, one of the highest figures of merit for nanowire electrodes ever reported.

Introduction of copper ions to regulate silver nanostructures by galvanic displacement reaction

Although the regulation of silver nanostructures has been reported a lot, there are few reports on the simple green preparation method of ultra-long silver nanobelts and the formation mechanism of silver nanostructures is not uniform. In this paper, ultra-long silver nanobelts and dendrite silver were synthesized through a galvanic displacement and the growth mechanism of the silver nanosturture were investigated in detail. In the primary battery reaction, the introduction of copper ions could change the electric double layer and then affected the growth of silver nanosturcture. Different concentration of copper ion lead to different silver nanostructures. The greater the concentration of copper ions, the more the silver nanostructures grow in three dimensions.

One step synthesis of silver nanowires using fructose as a reducing agent and its antibacterial and antioxidant analysis

Silver nanowires were synthesised using hydrothermal method by reducing silver nitrate (AgNO3) using fructose in the presence of poly-vinylpyrrolidone (PVP). The parameters such as the effect of process temperature, AgNO3 molarity, PVP and fructose (C6H12O6) concentration influencing the synthesis of silver nanowires (Ag NWs) were investigated. The scanning electron microscope (SEM) images showed that ultra-long, uniform and thin silver nanowires were obtained under optimized conditions; 0.02 M AgNO3, 0.016 g ml−1 of fructose, 0.16 g ml−1 of PVP at 160 °C within 22 h. The dynamic light scattering (DLS) analysis revealed that the silver nanowires obtained have an average diameter of 77 nm possessing high level of crystallinity with face centered cubic (fcc) phase that is evident from the x-ray diffraction (XRD) patterns peaked at (111), (200), (220), (311) and (222) planes. FT-IR (Fourier transform infrared spectroscopy) results suggested that there is adsorption of PVP molecules on the silver atoms. Ag NWs exhibited better antibacterial activity against Escherichia coli and high antioxidant activity against 2,2-diphenyl-1- picrylhydrazyl (DPPH) free radical scavenger. This work gives a green approach to the hydrothermal synthesis of Ag NWs using fructose with a promising antibacterial and antioxidant properties.

Ultra-long silver nanowires induced mitotic abnormalities and cytokinetic failure in A549 cells

Asbestos fiber has been associated with mesothelioma and lung cancer. However, the carcinogenic risks of other fiber nanomaterials with morphological similarities to asbestos have not been fully studied. Ultra-long silver nanowires (AgNWs) are increasingly used fiber-shaped nanomaterials with a high aspect ratio, but very few studies have investigated their health risks. Here, proliferation abnormalities of lung epithelial cells induced by ultra-long AgNWs were investigated. Ultra-long AgNW treatment induced dose- and diameter-dependent increase in the ratio of multinucleated cells. Further, proteins involved in mitosis and cytokinesis, including Aurora A, p-Histone 3 (ser10), RhoA, p-MLC, and myosin IIb, were significantly upregulated after an ultra-long AgNW treatment, leading to mitotic abnormalities and cytokinetic failure. Meanwhile, exposure to ultra-long AgNWs induced cell cycle arrest. Interestingly, a series of experiments demonstrated that ROS generation and Ag+ release were not responsible for the multinucleation induced by ultra-long AgNWs, but ultra-long AgNWs in the intercellular bridge might obstruct the contractile ring and inhibit abscission of the cytokinetic furrow by direct physical contact. Altogether, our findings indicate that ultra-long AgNWs can induce chromosomal instability, which has important consequences for the safety of ultra-long AgNWs to human health.

Silk fibroin and ultra-long silver nanowire based transparent, flexible and conductive composite film and its Temperature-Dependent resistance

A transparent, conductive, smooth, and temperature sensitive thin films was fabricated and characterized in this paper. Silk fibroin could be processed into transparent thin films, which can act as ideal opto-electronic substrates. As pure silk fibroin film is nonconductive, ultra-long silver nanowires coating and platinum sputtering were used to strengthen its conductivity. Ultra-long nanowires were used to reduce the junctions between wires, and platinum was to improve the conductivity of the film. The new nanowire-metal-organic composite film possesses excellent conductivity and good transmittance. The composite films containing different silver nanowires exhibit conductivities of as low as 6.9 Ω/sq, and transmittance of 60–80% in the visible light range. The films also showed potentials in practical applications as their resistance is almost linearly temperature-dependent. It also can transfer power to electrical devices. The new composite films could be expected to function in wearable electronics or implantable devices and sensors.

Highly Transparent and Flexible All-Solid-State Supercapacitors Based on Ultralong Silver Nanowire Conductive Networks.

Ultralong silver nanowires (Ag NWs) are preferred for enabling transparent conductive networks with low sheet resistance, high transparency, and excellent mechanical flexibility, which offer great merits in achieving high-performance and flexible energy storage devices. Herein, a new type of polyol process was proposed for the synthesis of ultralong Ag NWs. Uniform Ag NWs with the average length of 75 μm were obtained. Transparent conductive films (TCFs) based on the as-prepared Ag NWs exhibited low sheet resistance of 15.2 Ω/sq at 84% transmittance with a negligible change in sheet resistance after bending. Flexible all-solid-state supercapacitors based on the resulting Ag NW TCFs showed high transparency (>50%), good mechanical flexibility, and high cyclic stability with only slight areal capacitance decays after 100 times of bending (∼25%) and 5000 charge-discharge cycles (∼15%). The results manifest great potentials of the resulting TCFs based on ultralong Ag NWs for flexible and wearable energy-storage applications.