A robust electrochemical sensor based on AgNWs@MoS2 for highly sensitive detection of thiabendazole residues in food samples

Thiabendazole (TBZ), a highly toxic phosphorothioate insecticide commonly used in postharvest fruit management, has the potential to cause detrimental effects on human health as an endocrine disruptor. In this study, an electrochemical sensor was developed to detect TBZ by modifying MoS2 on silver nanowires (Ag NWs@MoS2) and integrating them onto a glassy carbon surface. Cyclic voltammetry revealed that TBZ underwent an irreversible, diffusion-controlled process on Ag NWs@MoS2, leading to a two-fold increase in peak current compared to unmodified MoS2. Square wave voltammetry facilitated TBZ detection, and the sensor exhibited a linear range of 0.05-10 μM with a high coefficient of determination (R2 = 0.9958) and a limit of detection (LOD) of 1.75 nM (signal-to-noise ratio = 3). The sensor's applicability for food safety monitoring was verified through TBZ analysis in pear and apple samples, achieving recoveries of 95.5-103.6% with RSDs in the range of 1.98-3.25%.

Semitransparent Organic Photovoltaic Devices: Interface/Bulk Properties and Stability Issues

In the present work, an insight on the morpho/structural properties of semitransparent organic devices for buildings' integrated photovoltaics is presented, and issues related to interface and bulk stability are addressed. The organic photovoltaic (OPV) cells under investigation are characterized by a blend of PM6:Y6 as a photo-active layer, a ZnO ETL (electron transporting layer), a HTL (hole transporting layer) of HTL-X and a transparent electrode composed by Ag nanowires (AgNWs). The devices' active nanomaterials, processed as thin films, and their mutual nanoscale interfaces are investigated by a combination of in situ Energy Dispersive X-ray Reflectometry (EDXR) and ex situ Atomic Force Microscopy (AFM), X-ray Diffraction (XRD) and micro-Raman spectroscopy. In order to discriminate among diverse concomitant aging pathways potentially occurring upon working conditions, the effects of different stress factors were investigated: light and temperature. Evidence is gained of an essential structural stability, although an increased roughness at the ZnO/PM6:Y6 interface is deduced by EDXR measurements. On the contrary, an overall stability of the system subjected to thermal stress in the dark was observed, which is a clear indication of the photo-induced origin of the observed degradation phenomenon. Micro-Raman spectroscopy brings light on the origin of such effect, evidencing a photo-oxidation process of the active material in the device, using hygroscopic organic HTL, during continuous illumination in ambient moisture conditions. The process may be also triggered by a photocatalytic role of the ZnO layer. Therefore, an alternative configuration is proposed, where the hygroscopic HTL-X is replaced by the inorganic compound MoOx. The results show that such alternative configuration is stable under light stress (solar simulator), suggesting that the use of Molybdenum Oxide, limiting the photo-oxidation of the bulk PM6:Y6 active material, can prevent the cell from degradation.

Liquid-Film Rupture for Web-like Ag Nanowires toward High-Performance Organic Schottky Barrier Transistors

Organic vertical transistors are promising device with benefits such as high operation speed, high saturation current density, and low-voltage operation owing to their short channel length. However, a short channel length leads to a high off-current, which is undesirable because it affects the on-off ratio and power consumption. This study presents a breakthrough in the development of high-performance organic Schottky barrier transistors (OSBTs) with a low off-current by utilizing a near-ideal source electrode with a web-like Ag nanowire (AgNW) morphology. This is achieved by employing a humidity- and surface-tension-mediated liquid-film rupture technique, which facilitates the formation of well-connected AgNW networks with large pores between them. Therefore, the gate electric field is effectively transmitted to the semiconductor layer. Also, the minimized surface area of the AgNWs causes complete suppression of the off-current and induces ideal saturation of the OSBT output characteristics. p- and n-type OSBTs exhibit off-currents in the picoampere range with on/off ratios exceeding 106 and 105, respectively. Furthermore, complementary inverters are prepared using an aryl azide cross-linker for patterning, with a gain of >16. This study represents a significant milestone in the development of high-performance organic vertical transistors and verifies their applicability in organic electronic circuitry.

Laser speckle reduction using polymer-stabilized liquid crystals doped with Ag nanowires

Miniaturized and pure static devices are expected to be used in laser-imaging systems for speckle reduction. In this study, a pure static device based on polymer-stabilized liquid crystal (PSLC) doped with Ag nanowires was developed to effectively suppress laser speckles. The concentrations of the polymer and Ag nanowires in the PSLC were optimized, and then the PSLC devices were fabricated. A measurement system was set up to characterize the electro-optical properties of the fabricated PSLC devices. Subsequently, a laser projection system was built to demonstrate the speckle-reduction performance. Moreover, the degree of scattering and response time of the developed PSLC devices were investigated and discussed. A PSLC doped with 0.02 wt% Ag nanowires and 3 wt% polymer having a device size of 2 × 2 × 0.1 cm3 was demonstrated to produce a speckle-reduction efficiency of 51.4 % under very low driving voltages. The experimental results verified effectiveness and superiority of the developed speckle reduction method based on PSLC doped with Ag nanowires.

Construction of 1D Heterogeneous Co/C@Ag Nws With Tunable Electromagnetic Wave Absorption And Shielding Performance

In this study, silver nanowires (Ag NWs) are synthesized at first, and then the 1D heterogeneous Co/C@Ag NWs with a kebab- and popsicle-like microstructures are constructed by in situ growth ZIF-67 on Ag NWs combined with calcination. Results show that the EM wave prevention performance of composites depends on the loading of Co/C particles threaded on the Ag NWs. The popsicle-like structure with high Co/C loading gives Co/C@Ag NWs excellent EM wave absorption performance, which achieved a minimum reflection loss (RLmin ) of -44.5 dB with a low filling of 30 wt.% in paraffin; while the kebab-like structure with low Co/C loading shows good electromagnetic interference (EMI) shielding effectiveness (SET ) of 30.2 dB at the same filler ratio. The enhanced EM wave absorption performance is attributed to the synergy of multiple energy dissipation mechanisms including dielectric loss, magnetic loss, polarization loss, eddy-current loss, multiple reflection loss, as well as proper impedance matching; the good EMI shielding performance is mainly due to the conduction loss brought by the Ag NWs with ultrahigh conductivity. This work provides a reference for the design of electromagnetic wave prevention material with tuned absorption and shielding performance.

Antimicrobial Activity and Crystallization Features in Bio-Based Composites of PLLA and MCM-41 Particles Either Pristine or Functionalized with Confined Ag Nanowires

Composites based on an L-rich poly(lactic acid) (PLLA) and MCM-41, either neat or modified with a silver (MCM-41@Ag), are achieved by solvent casting, being next processed by compression molding. Ag is mainly embedded as nanowires within the hybrid MCM-41@Ag particles, enabling its antimicrobial character. In these composites, the PLLA thermal stability, nucleation efficiency, and mechanical response are dependent on the MCM-41 nature and, to a lesser extent, on its content. Thus, differences in transitions of the PLLA matrix are noticed during cooling at 10 °C/min and in the subsequent heating when composites with neat or modified MCM-41 are compared. A very remarkable nucleation effect is played by pristine MCM-41, being inferior when MCM-41@Ag is incorporated into the PLLA. Wide angle X-ray scattering (WAXS) measurements using synchrotron radiation and performed under variable-temperature conditions in the composites containing MCM-41@Ag indicate that during cold crystallization, the disordered α' polymorph is initially formed, but it rapidly transforms into ordered α crystals. A long spacing peak, clearly seen in pure PLLA, appears as a small shoulder in PLLAMCM@Ag4 and is undetectable in PLLAMCM@Ag9 and PLLAMCM@Ag20. Furthermore, an increase in MH with the silica content is found in the two sets of composites, the higher MH values being observed in the family of PLLA and MCM-41@Ag. Finally, remarkable antimicrobial features are noticeable in the composites with MCM-41@Ag since this modified silica transfers its biocidal characteristics into the PLLA composites.

A Hierarchically Structured Graphene/Ag Nanowires Paper as Thermal Interface Material

With the increase in heat power density in modern integrating electronics, thermal interface materials (TIM) that can efficiently fill the gaps between the heat source and heat sinks and enhance heat dissipation are urgently needed owing to their high thermal conductivity and excellent mechanical durability. Among all the emerged TIMs, graphene-based TIMs have attracted increasing attention because of the ultrahigh intrinsic thermal conductivity of graphene nanosheets. Despite extensive efforts, developing high-performance graphene-based papers with high through-plane thermal conductivity remains challenging despite their high in-plane thermal conductivity. In this study, a novel strategy for enhancing the through-plane thermal conductivity of graphene papers by in situ depositing AgNWs on graphene sheets (IGAP) was proposed, which could boost the through-plane thermal conductivity of the graphene paper up to 7.48 W m^-1 K^-1 under packaging conditions. In the TIM performance test under actual and simulated operating conditions, our IGAP exhibits strongly enhanced heat dissipation performance compared to the commercial thermal pads. We envision that our IGAP as a TIM has great potential for boosting the development of next-generation integrating circuit electronics.

High Temperature-Resistant Transparent Conductive Films for Photoelectrochemical Devices Based on W/Ag Composite Nanonetworks

The traditional Ag nanowire preparation means that it cannot meet the demanding requirements of photoelectrochemical devices due to the undesirable conductivity, difficulty in compounding, and poor heat resistance. Here, we prepared an Ag nanonetwork with superior properties using a special template method based on electrospinning technology. The transparent conductive films based on Ag nanonetworks have good transmittance in a wide range from ultraviolet to visible. It is important that the films have high operability and are easy to be compounded with other materials. After compounding with high-melting-point W metal, the heat-resistance temperature of the W/Ag composite transparent conductive films is increased by 100 °C to 460 °C, and the light transmission and electrical conductivity of the films are not significantly affected. All experimental phenomena in the study are analyzed theoretically. This research can provide an important idea for the metal nanowire electrode, which is difficult to be applied to the photoelectrochemical devices.

High-Wettability Poly(dimethylsiloxane) Substrate for Ultrastable Conductive Three-Dimensional Woven Ag Nanowire Grids

Three-dimensional (3D) woven Ag nanowire (AgNW) grids have great potential for enhancing the mechanical stabilities, conductivity, and transmittance of flexible transparent electrodes (FTEs). However, it is a great challenge to control the formation of 3D woven AgNW grids on various substrates, especially the poly(dimethylsiloxane) (PDMS) substrate. This work presents a microtransfer-printing method for preparing a high-wettability poly(dimethylsiloxane) (PDMS) substrate to control the formation of 3D woven AgNW grids. The as-prepared PDMS substrate shows a high wettability performance. The surface structures of the PDMS substrate can control the sharp shrinkage of the ink membrane to give rise to a uniform liquid membrane evaporation behavior, which is the key factor for preparing a uniform 3D woven nanowire network. A thin uniform 3D woven AgNW network with a low sheet resistance of 24.3 Ω/□ and high transmittance of 92% was coated on the PDMS substrate. The networks directly coated the surface of the replicated PDMS, which simplified the peeling process and protected the networks from peeling strain and mechanical deformations. Moreover, the increment of resistance retained a small value (∼5%) when bending cycles reached 9,000. An alternating current electroluminescent (ACEL) device was prepared, and the uniform electroluminescence implies that a defect-free electrode has been fabricated. These results indicate that the as-prepared FTEs have excellent mechanical performance and great potential for flexible optoelectronic applications.

Comparative Study on Preparation Methods for Transparent Conductive Films Based on Silver Nanowires

Silver nanowires, which have high optoelectronic properties, have the potential to supersede indium tin oxide in the field of electrocatalysis, stretchable electronic, and solar cells. Herein, four mainstream experimental methods, including Mayer-rod coating, spin coating, spray coating, and vacuum filtration methods, are employed to fabricate transparent conductive films based on the same silver nanowires to clarify the significance of preparation methods on the performance of the films. The surface morphology, conductive property, uniformity, and flexible stability of these four Ag NW-based films, are analyzed and compared to explore the advantages of these methods. The transparent conductive films produced by the vacuum filtration method have the most outstanding performance in terms of surface roughness and uniformity, benefitting from the stronger welding of NW-NW junctions after the press procedure. However, limited by the size of the membrane and the vacuum degree of the equipment, the small-size Ag films used in precious devices are appropriate to obtain through this method. Similarly, the spin coating method is suited to prepare Ag NWs films with small sizes, which shows excellent stability after the bending test. In comparison, much larger-size films could be obtained through Mayer-rod coating and spray coating methods. The pull-down speed and force among the Mayer-rod coating process, as well as the spray distance and traveling speed among the spray coating process, are essential to the uniformity of Ag NW films. After being treated with NaBH₄ and polymethyl methacrylate (PMMA), the obtained Ag NW/PMMA films show great potential in the field of film defogging due to the Joule heating effect. Taken together, based on the advantages of each preparation method, the Ag NW-based films with desired size and performances are easier to prepare, meeting the requirements of different application fields.

Preparation of Low Volatile Organic Compounds Silver Paste Containing Ternary Conductive Fillers and Optimization of Their Performances

Conductive silver paste is a key material in the fields of printed circuits and printed electronic devices. However, the preparation of conductive silver paste with low-cost and volatile organic compounds (VOCs) is still a challenge. In this work, conductive silver pastes with excellent comprehensive performances were developed by using water-borne polyurethane (WPU) as the bonding phase and using the ternary mixture of Ag microflakes (Ag MFs), Ag nanowires (Ag NWs), and Ag nanoparticles (Ag NPs) as the conductive phase. WPU endowed conductive silver pastes with the adhesion along with releasing a few VOCs during the curing. Results showed that a small amount of Ag NPs or Ag NWs dramatically enhanced the electrical conductivity of silver paste paint film filled only with Ag MFs. The electrical resistivity for optimal ternary mixture conductive silver paste was 0.2 × 10^-3 Ω∙cm, and the conductive phase was composed of 20.0 wt% Ag MFs, 7.5 wt% Ag NWs, and 2.5 wt% Ag NPs. Meanwhile, the adhesive strength and hardness of silver paste paint film were effectively improved by increasing the curing temperature. The optimal overall performance of the conductive silver pastes was achieved at the curing temperature of 160 °C. Therefore, this work can provide a new route for preparing conductive silver pastes with high performances.

Complete Solution-Processed Semitransparent and Flexible Organic Solar Cells: A Success of Polyimide/Ag-Nanowires- and PH1000-Based Electrodes with Plasmonic Enhanced Light Absorption

Organic solar cells (OSCs) have been widely studied due to the advantages of easy fabrication, low cost, light weight, good flexibility and sufficient transparency. In this work, flexible and semitransparent OSCs were successfully fabricated with the adoption of both polyimide/silver nanowires (PI/AgNW) and a conducting polymer PEDOT:PSS named PH1000 as the transparent conductive electrodes (TCEs). It is demonstrated that PI/AgNW is more suitable as a cathode rather than an anode in the viewpoint of its work function, photovoltaic performance, and simulations of optical properties. It is also found that the light incidence from PH1000 TCE can produce more plasmonic-enhanced photon absorption than the PI/AgNW electrode does, resulting in more high power conversion efficiency. Moreover, a high light transmittance of 33.8% and a decent efficiency of 3.88% are achieved for the whole all-flexible semitransparent device with only 9% decrease of resistance in PI/AgNW after 3000 bending cycles. This work illustrates that PI/AgNW has great potential and bright prospect in large-area OSC applications in the future.

Aluminum sheet induced flower-like carbon nitride anchored with silver nanowires for highly efficient SERS detection of trace malachite green

The sensitive detection of malachite green (MG) in aquaculture wastewater is necessary for its residual poses a great threat to the living systems. Herein, the flower-like C₃N₄ (f-C₃N₄) nanostructure induced by Al sheet in the hydrothermal process is constructed. Subsequently, Ag nanowires (AgNWs) supported on Al/f-C₃N₄ and the strong interaction between AgNWs and Al/f-C₃N₄ are confirmed by XPS, Raman spectroscopy, UV-vis diffuse reflectance and fluorescence spectroscopy. Importantly, the portable Al/f-C₃N₄/AgNWs substrate shows the outstanding SERS response for MG, which is attributed to enhanced electromagnetic effect of AgNWs on large amount of corrugated and creviced regions in the flower-like Al/f-C₃N₄ and the charge transfer among the components. Also, the prepared Al/f-C₃N₄ nanostructure provides large specific surface area and abundant "N" active sites for AgNWs, and the high enrichment ability of Al/f-C₃N₄ towards MG molecules by the strong π-π stacking interaction. The detection limit of Al/f-C₃N₄/AgNWs for MG is as low as 8.38 × 10^-12 mol L^-1. The substrate can be reproduced and reused for at least 7 cycles, and the activity can still be kept after laid up for 49 days. Importantly, it unfolds a good sensitivity and selectivity for MG in actual water sample. Results indicate that the Al/f-C₃N₄/AgNWs substrate has a promising potential in practical application for trace detection of MG.

Continuous Wave Laser Nanowelding Process of Ag Nanowires on Flexible Polymer Substrates

In this paper we present the laser nanowelding process of silver nanowires (AgNWs) deposited on flexible polymer substrates by continuous wave (CW) lasers. CW lasers are cost-effective and can provide moderate power density, somewhere between nanosecond pulsed lasers and flash lamps, which is just enough to perform the nanowelding process efficiently and does not damage the nanowires on the polymer substrates. Here, an Nd:YAG CW laser (wavelength 532 nm) was used to perform the nanowelding of AgNWs on polyethylene terephthalate (PET) substrates. Key process parameters such as laser power, scan speed, and number of scans were studied and optimized, and mechanisms of observed phenomena are discussed. Our best result demonstrates a sheet resistance of 12 ohm/squ with a transmittance at λ = 550 nm of 92% for AgNW films on PET substrates. A transparent resistive heater was made, and IR pictures were taken to show the high uniformity of the CW laser nanowelded AgNW film. Our findings show that highly effective and efficient nanowelding can be achieved without the need of expensive pulse lasers or light sources, which may contribute to lower the cost of mass producing AgNWs on flexible substrates.

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.

Study of Microwave-Induced Ag Nanowire Welding for Soft Electrode Conductivity Enhancement

Silver nanowire (AgNW)-coated thin films are widely proposed for soft electronics application due to their good conductivity, transparency and flexibility. Here, we studied the microwave welding of AgNW-based soft electrodes for conductivity enhancement. The thermal effect of the microwave to AgNWs was analyzed by dispersing the nanowires in a nonpolar solution, the temperature of which was found to be proportional with the nanowire diameters. AgNWs were then coated on a thin film and welded under microwave heating, which achieved a film conductivity enhancement of as much as 79%. A microwave overheating of AgNWs, however, fused and broke the nanowires, which increased the film resistance significantly. A soft electrode was finally demonstrated using the microwave-welded AgNW thin film, and a 1.13 µA/mM sensitivity was obtained for glucose sensing. Above all, we analyzed the microwave thermal effect on AgNWs to provide a guidance to control the nanowire welding effect, which can be used for film conductivity enhancement and applied for soft and bio-compatible electrodes.

Ag Nanowire-Plasmonic-Assisted Charge Separation in Hybrid Heterojunctions of Ppy-PEDOT:PSS/GaN Nanorods for Enhanced UV Photodetection

The surface states, poor carrier life, and other native defects in GaN nanorods (NRs) limit their utilization in high-speed and large-gain ultraviolet (UV) photodetection applications. Making a hybrid structure is one of the finest strategies to overcome such impediments. In this work, a polypyrrole (Ppy)-poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/GaN NRs hybrid structure is introduced for self-powered UV photodetection applications. This hybrid structure yields high photodetection performance, while pristine GaN NRs showed negligible photodetection properties. The ability of the photodetector is further boosted by functionalizing the hybrid structure with Ag nanowires (NWs). The Ag NWs-functionalized hybrid structure exhibited a responsivity of 3.1 × 10³ (A/W), detectivity of 3.19 × 10¹⁴ Jones, and external quantum efficiency of 1.0⁶ × 10⁶ (%) under a UV illumination of λ = 382 nm. This high photoresponse is due to the huge photon absorption rising from the localized surface plasmonic effect of a Ag NWs network. Also, the Ag NWs significantly improved the rising and falling times, which were noted to be 0.20 and 0.21 s, respectively. The model band diagram was proposed with the assistance of X-ray photoelectron spectroscopy to explore the origin of the superior performance of the Ag NWs-decorated Ppy-PEDOT:PSS/GaN NRs photodetector. The proposed hybrid structure seems to be a promising candidate for the development of high-performance UV photodetectors.

Facile Approach to Fabricating Stretchable Organic Transistors with Laser-Patterned Ag Nanowire Electrodes

Stretchable electronics are poised to revolutionize personal healthcare and robotics, where they enable distributed and conformal sensors. Transistors are fundamental building blocks of electronics, and there is a need to produce stretchable transistors using low-cost and scalable fabrication techniques. Here, we introduce a facile fabrication approach using laser patterning and transfer printing to achieve high-performance, solution-processed intrinsically stretchable organic thin-film transistors (OTFTs). The device consists of Ag nanowire (NW) electrodes, where the source and drain electrodes are patterned using laser ablation. The Ag NWs are then partially embedded in a poly(dimethylsiloxane) (PDMS) matrix. The electrodes are combined with a PDMS dielectric and polymer semiconductor, where the layers are individually transfer printed to complete the OTFT. Two polymer semiconductors, DPP-DTT and DPP-4T, are considered and show stable operation under the cyclic strain of 20 and 40%, respectively. The OTFTs maintain electrical performance by adopting a buckled structure after the first stretch-release cycle. The conformability and stretchability of the OTFT is also demonstrated by operating the transistor while adhered to a finger being flexed. The ability to pattern highly conductive Ag NW networks using laser ablation to pattern electrodes as well as interconnects provides a simple strategy to produce complex stretchable OTFT-based circuits.

Ultra-Flexible Organic Photovoltaics with Nanograting Patterns Based on CYTOP/Ag Nanowires Substrate

In this study, we developed a method for fabricating ultrathin polymer substrates that can be used in ultra-flexible organic photovoltaics (OPVs) via a non-vacuum process using cyclic transparent optical polymer. In addition, a Ag nanowire network layer was used as a transparent electrode in a solution process. All processes were conducted on large area via spin coating. The power conversion efficiency (PCE) of the ultra-flexible OPV improved by 6.4% compared to the PCE of the ITO/Glass-based OPV. In addition, the PCE of the OPV increased to 10.12% after introducing nanostructures in the ZnO and photoactive layers. We performed 1000 cycles of compression/relaxation tests to evaluate the mechanical properties of the ultra-flexible OPV, after which, the PCE remained at 67% of the initial value. Therefore, the developed OPV system is suitable as a power source for portable devices.

Hybridization of Defective Tin Disulfide Nanosheets and Silver Nanowires Enables Efficient Electrochemical Reduction of CO2 into Formate and Syngas

Integrating the defect engineering and conductivity promotion represents a promising way to improve the performance of CO₂ electrochemical reduction. Herein, the hybridized composite of defective SnS₂ nanosheets and Ag nanowires is developed as an efficient catalyst for the production of formate and syngas toward CO₂ electrochemical reduction. The Schottky barrier in Ag-SnS₂ hybrid nanosheets is negligible due to the similar Fermi level of SnS₂ nanosheets and Ag nanowires. Accordingly, the free electrons of Ag nanowires participate in the electronic transport of SnS₂ nanosheets, and thus give rise to a 5.5-fold larger carrier density of Ag-SnS₂ hybrid nanosheets than that of SnS₂ nanosheets. In CO₂ electrochemical reduction, the Ag-SnS₂ hybrid nanosheets display 38.8 mA cm^-2 of geometrical current density at -1.0 V vs reversible hydrogen electrode, including 23.3 mA cm^-2 for formate and 15.5 mA cm^-2 for syngas with the CO/H₂ ratio of 1:1. A mechanistic study reveals that the abundant defect sites and carrier density not only promote the conductivity of the electrocatalyst, but also increase the binding strength for CO₂ , which account for the efficient CO₂ reduction.

Improving Performance of Nonfullerene Organic Solar Cells over 13% by Employing Silver Nanowires-Doped PEDOT:PSS Composite Interface

Ag nanowires (NWs)/PEDOT:PSS composite was prepared by a facile solution-processing method and employed as anode interface in nonfullerene organic solar cells (OSCs). In the presence of a Ag NWs (5%, v/v%)/PEDOT:PSS interfacial layer, a high-power conversion efficiency up to 13.53% was achieved based on a PBDB-T-2Cl:IT-4F photoactive layer system, much higher than the efficiency of the controlled counterpart device with pristine PEDOT:PSS as anode modifier. Simultaneous enhancements in short-circuit current and fill factor were observed, in comparison to the case of the pristine PEDOT:PSS interface, due to the improved electrical conductivity of Ag NWs/PEDOT:PSS composites accompanied by the increased work function for a better matching with the indium tin oxide counter electrode, which facilitated increased charge transfer and reduced charge recombination at the anode/photoactive interface for improved device performance. The results clearly revealed that the Ag NWs/PEDOT:PSS composite interface is beneficial to improve the charge extraction and favor the realization of highly efficient nonfullerene OSCs.

In Situ Observation of Dynamic Galvanic Replacement Reactions in Twinned Metallic Nanowires by Liquid Cell Transmission Electron Microscopy

Galvanic replacement is a versatile approach to prepare hollow nanostructures with controllable morphology and elemental composition. The primary issue is to identify its fundamental mechanism. In this study, in situ liquid cell transmission electron microscopy was employed to monitor the dynamic reaction process and to explore the mechanism of galvanic replacement. The detailed reaction process was revealed based on in situ experiments in which small Au particles first appeared around Ag nanowires; they coalesced, grew, and adhered to Ag nanowires. After that, small pits grew from the edge of Ag nanowires to form tubular structures, and then extended along the Ag nanowires to obtain hollowed structures. All of our experimental observations from the viewpoint of electron microscopy, combined with DFT calculations, contribute towards an in-depth understanding of the galvanic replacement reaction process and the design of new materials with hollow structures.

Printing the Ultra-Long Ag Nanowires Inks onto the Flexible Textile Substrate for Stretchable Electronics

: Printing technology offers a simple and cost-effective opportunity to develop all-printed stretchable circuits and electronic devices, possibly providing ubiquitous, low-cost, and flexible devices. To successfully prepare high-aspect-ratio Ag nanowires (NWs), we used water and anhydrous ethanol as the solvent and polyvinylpyrrolidone (PVP) as the viscosity regulator to obtain a water-soluble Ag NWs conductive ink with good printability. Flexible and stretchable fabric electrodes were directly fabricated through screen printing. After curing at room temperature, the sheet resistance of the Ag NW fabric electrode was 1.5 Ω/sq. Under a tensile strain of 0-80% and with 20% strains applied for 200 cycles, good conductivity was maintained, which was attributed to the inherent flexibility of the Ag NWs and the intrinsic structure of the interlocked texture.

Ultrasonic Modification of Ag Nanowires and Their Applications in Flexible Transparent Film Heaters and SERS Detectors

Ultrasonic morphology modification of silver (Ag) nanowires and their applications in transparent film heaters for defogging in electric vehicles and surface-enhanced Raman scattering (SERS) detectors have been studied. With 10 min ultrasonic treatment of Ag nanowires, the electro-thermal conversion capability of Ag nanowire based transparent film heaters is efficiently improved (about 50% increase in temperature rise), which can be mainly attributed to the cross-section area reduction and the serious agglomerations of the ultrasonic modified Ag nanowire films. Furthermore, the bending or fracture caused by deformation of Ag nanowires after ultrasonic treatment provides more hot spots for SERS, and therefore lead to a significant SERS signal enhancement. This work not only greatly improves the performance of Ag nanowire based transparent film heaters and SERS detectors, but provides a new way for the functional modification of Ag nanowires.

Enhanced Silver Nanowire Composite Window Electrode Protected by Large Size Graphene Oxide Sheets for Perovskite Solar Cells

Despite the outstanding features of high transmittance and low sheet resistance from silver nanowire (Ag NW) based transparent electrodes, their applications in perovskite solar cells (PVSCs) as window electrodes encounter significant obstacles due to the stability issue brought by the corrosion of halogen species from perovskite layer. In this study, we used large size graphene oxide (LGO) sheets as the protective barrier for bottom Ag NW nano-network. Contributed by the LGO with average size of 60 μm, less GO sheet was necessary for forming the fully covered protective barrier with fewer cracks, which consequently improved the optical transparency and anticorrosive ability of the composite electrode compared to the one from relatively small size GO. Our experiments demonstrated the composite electrode of Ag NW/LGO. The glass substrate exhibited transmittance of 83.8% and 81.8% at 550 nm before and after partial reduction, which maintained 98.4% and 95.1% average transmittance (AVT) of the pristine Ag NW electrode. Meanwhile, we utilized the steady hot airflow to assist the fast solvent evaporation and the uniform GO film formation on Ag NW electrode. Before the application of composite electrode in organic-inorganic hybrid perovskite solar cells, the operational stability of composite electrodes from different sizes of GO with perovskite film fabricated on top were characterized under continuing external bias and light irradiation. Experimental results indicate that the Ag NW electrode protected by LGO could maintain original resistance for more than 45 h. Finally, the PVSC fabricated on Ag NW/LGO based composite electrode yielded a power conversion efficiency (PCE) of 9.62%, i.e., nearly 85% of that of the reference device fabricated on the commercial indium-tin oxide (ITO) glass. Our proposed low temperature and solution processed bottom electrode with improved optical transparency and operational stability can serve as the very beginning layer of optoelectronic devices, to promote the development of low cost and large area fabrication perovskite solar cells.

Fabrication and Characterization of a Capacitive Photodetector Comprising a ZnS/Cu Particle/Poly(vinyl butyral) Composite

Most photodetectors developed to date essentially measure photocurrents induced by the generation and separation of electron-hole pairs in semiconductors during irradiation. Although the above light detection method is well established, highly sensitive, and applicable to a broad range of semiconductor materials, it requires the presence of a stable and direct contact between the semiconductor and the electrode for accurate photocurrent measurements. In turn, this prerequisite necessitates the use of various costly processes for device fabrication (e.g., photolithography and vacuum deposition of semiconductors/metals) and complicates the development of flexible devices. Herein, inspired by the fact that the dielectric properties of certain materials can be changed by light irradiation, we dispersed ZnS/Cu semiconducting particles in poly(vinyl butyral) to prepare a free-standing composite film and formed two layers of Ag nanowire electrodes on both sides of the cured composite to fabricate a photodetector of a completely new type. The developed device exhibited a capacitance very sensitive to irradiation with light of a specific wavelength and additionally featured the advantages of simple structure/operation mechanism, mechanical flexibility, and transparency, not showing any signs of performance deterioration even after severe damage.

Catalytic Application and Mechanism Studies of Argentic Chloride Coupled Ag/Au Hollow Heterostructures: Considering the Interface Between Ag/Au Bimetals

For an economical use of solar energy, photocatalysts that are sufficiently efficient, stable, and capable of harvesting light are required. Composite heterostructures composed of noble metals and semiconductors exhibited the excellent in catalytic application. Here, 1D Ag/Au/AgCl hollow heterostructures are synthesized by galvanic replacement reaction (GRR) from Ag nanowires (NWs). The catalytic properties of these as-obtained Ag/Au/AgCl hollow heterostructures with different ratios are investigated by reducing 4-nitrophenol (Nip) into 4-aminophenol (Amp) in the presence of NaBH₄, and the influence of AgCl semiconductor to the catalytic performances of Ag/Au bimetals is also investigated. These hollow heterostructures show the higher catalytic properties than pure Ag NWs, and the AgCl not only act as supporting materials, but the excess AgCl is also the obstacle for contact of Ag/Au bimetals with reactive species. Moreover, the photocatalytic performances of these hollow heterostructures are carried out by degradation of acid orange 7 (AO7) under UV and visible light. These Ag/Au/AgCl hollow heterostructures present the higher photocatalytic activities than pure Ag NWs and commercial TiO₂ (P25), and the Ag/Au bimetals enhance the photocatalytic activity of AgCl semiconductor via the localized surface plasmon resonance (LSPR) and plasmon resonance energy transfer (PRET) mechanisms. The as-synthesized 1D Ag/Au/AgCl hollow heterostructures with multifunction could apply in practical environmental remedy by catalytic manners.

Rapid Tartrazine Determination in Large Yellow Croaker with Ag Nanowires Using Surface-Enhanced Raman Spectroscopy

In this work, surface-enhanced Raman spectroscopy (SERS) technology coupled with Ag nanowires was shown to be a promising tool in the detection of tartrazine in large yellow croaker for the first time. Ag nanowires with a uniform diameter were fabricated by an efficient and manageable polyol method. The partial least square model was established for the quantitative analysis of tartrazine, which showed a relatively high linear correlation between actual and predicted concentrations of standard tartrazine solutions. An optimal sample preparation method was also selected and used to extract tartrazine from large yellow croaker within 20 min. The lowest concentration detected was 20.38 ng/cm², which fully meets the requirements of tartrazine testing in aquatic products. This study indicated that SERS technology combined with the as-prepared Ag nanowires could detect tartrazine sensitively and provide an easily operable and time-saving way to monitor tartrazine in large yellow croaker.

Glass-Fabric Reinforced Ag Nanowire/Siloxane Composite Heater Substrate: Sub-10 nm Metal@Metal Oxide Nanosheet for Sensitive Flexible Sensing Platform

The development of flexible chemiresistors is imperative for real-time monitoring of air quality and/or human physical conditions without space constraints. However, critical challenges such as poor sensing characteristics, vulnerability under toxic chemicals, and weak reliability hinder their practical use. In this work, for the first time, an ultrasensitive flexible sensing platform is reported by assembling Pt loaded thin-layered (≈10 nm) SnO₂ nanosheets (Pt-SnO₂ NSs) based 2D sensing layers on Ag nanowires embedded glass-fabric reinforced vinyl-phenyl siloxane hybrid composite substrate (AgNW-GFRVPH film) as a heater. The thermally stable AgNW-GFRVPH film based heater is fabricated by free radical polymerization of vinyl groups in vinyl-phenyl oligosiloxane and phenyltris(dimethylvinylsiloxy)silane with Ag NW and glass-fabric, showing outstanding heat generation (≈200 °C), high dimensional stability (13 ppm °C^-1), and good thermal stability (≈350 °C). The Pt-SnO₂ NSs, which are synthesized by calcination of Sn precursor coated graphene oxide (GO) sheets and subsequent Pt functionalization, exhibit high mechanical flexibility and superior response (R_air/R_gas = 4.84) to 1 ppm level dimethyl sulfide. Taking these advantages, GO-templated oxide NSs combined with a highly stable AgNW-GFRVPH film heater exhibits the best dimethyl sulfide sensing performance compared to state-of-the-art flexible chemiresistors, enabling them as a superior flexible gas sensing platform.

Novel Patterning Method for Nanomaterials and Its Application to Flexible Organic Light-Emitting Diodes

We present a simple, low-cost, and scalable method to form various patterns of nanomaterials with different dimensions and shapes using capillary and centrifugal forces. The desired patterns were formed on the surfaces of poly(dimethylsiloxane) (PDMS) stamps, and the PDMS stamps were conformally contacted with the surfaces of flexible polymer substrates. Solutions of nanomaterials, such as metal nanowires and nanoparticles, were then drop-casted at one open end of the microchannels formed at the interface of the polymer substrate and PDMS stamp. The nanomaterial solutions penetrated the microchannels due to capillary force interactions between the surfaces and the fluid. The solvents of the nanomaterial solutions exfiltrated from the entrance of microchannels because of the coffee ring effect. Then, the solvent remaining in the microchannels was discharged by applying a centrifugal force by spinning the polymer substrate/PDMS stamp system. Because of the synergistic effect of the capillary force, coffee ring effect, and centrifugal force, uniform patterns of the nanomaterials with clearly defined edges were formed for a variety of pattern shapes and substrates. Furthermore, the direct patterning approach resulted in a significant reduction in the amount of wasted materials. Finally, flexible organic light-emitting diodes were successfully fabricated on the finely patterned nanowire electrodes.

Polyimide Aerogels Cross-Linked with Aminated Ag Nanowires: Mechanically Strong and Tough

In this study, polyimide (PI)/Ag nanowire (AgNW) nanocomposite aerogels with extremely high mechanical performance have been fabricated utilizing amine-modified AgNWs as mechanical nanoreinforcement particulates and crosslinking agents. Initially, AgNWs were fabricated and surface modified by p-aminothiophenol (PATP), then the aminated AgNWs were dispersed into polyamide acid solution and aerogels were prepared by supercritical CO₂ drying. Raman and X-ray photoelectron spectroscopy (XPS) spectrometry were carried out on A-AgNWs (aminated Ag nanowires) to prove the successful modification. This functional nanoparticle greatly enhanced the strength and toughness of aerogels without evident increase in densities. Comparing to pure PI aerogels, samples with 2.0 wt % of A-AgNWs had a 148% increase in compression strength and 223% increase in Young's modulus, which equates to 2.41 and 27.66 MPa, respectively. Simultaneously, the tensile test indicated that aerogels with 2.0 wt % of A-AgNWs had a breaking energy of 40.18 J/m³, which is 112% higher than pure PI aerogels. The results presented herein demonstrate that aminated AgNWs are an innovative cross-linker for PI aerogels and can improve their strength and toughness. These aerogels have excellent potential as high-duty, lightweight porous materials in many areas of application.

Simple and Reliable Lift-Off Patterning Approach for Graphene and Graphene-Ag Nanowire Hybrid Films

We present a simple, ultrasonic vibration-assisted lift-off-based patterning approach for graphene and graphene-Ag nanowire (NW) hybrid films. A 20 μm width pattern with uniform and smooth pattern edges was neatly defined on various rigid and flexible substrates. The patterned graphene-Ag NW electrodes showed a low sheet resistance of 19 Ω/sq with a high transmittance of 93% at 550 nm, a robust stability against oxidation, and a high reliability under a bending test. The electrodes also exhibited markedly higher performance than that of commercial fluorine-doped tin oxide electrodes for dye-sensitized solar cells. Given its low-cost, high throughput, and nondamaging effect, this simple and reliable patterning approach stimulates the practical applications of graphene-based flexible transparent electrodes in soft electronic and optoelectronic devices.

Growth of Silver Nanowires from Controlled Silver Chloride Seeds and Their Application for Fluorescence Enhancement Based on Localized Surface Plasmon Resonance

A "Polyol" method has granted low-cost and facile process-controllability for silver-nanowire (Ag-NW) synthesis. Although homogenous and heterogeneous nucleation and growth during Ag-NW synthesis are possible using polyol methods, heterogeneous nucleation and growth of Ag NW guarantees highly selective growth of nanostructures using silver chloride (AgCl) seeds, which provides a stable source of chloride ions (Cl-) and thermodynamic reversibility. In this paper, a microdroplet has been adopted to synthesize uniform AgCl seeds with different diameter that are used for seed-mediated Ag-NW synthesis. The concentration of two precursors (AgNO₃ and NaCl) in the droplets is modulated to produce different sizes of AgCl seeds, which determines the diameter and length of Ag NWs. The process of the seed-mediated growth of Ag NWs has been monitored by observing the peak shift in the time-resolved UV-vis extinction spectrum. Furthermore, the distinct plasmonic property of Ag NWs for transverse and longitudinal localized-surface-plasmon-resonance (LSPR)-mediated fluorescence enhancement is utilized. The high aspect ratio and sharp tips work as simple antennas that induce the enhanced fluorescence emission intensity of a fluorophore, which can be applied in the fields of biological tissue imaging and therapy.

Silver Nanowire Embedded Colorless Polyimide Heater for Wearable Chemical Sensors: Improved Reversible Reaction Kinetics of Optically Reduced Graphene Oxide

Optically reduced graphene oxide (ORGO) sheets are successfully integrated on silver nanowire (Ag NW)-embedded transparent and flexible substrate. As a heating element, Ag NWs are embedded in a colorless polyimide (CPI) film by covering Ag NW networks using polyamic acid and subsequent imidization. Graphene oxide dispersed aqueous solution is drop-coated on the Ag NW-embedded CPI (Ag NW-CPI) film and directly irradiated by intense pulsed light to obtain ORGO sheets. The heat generation property of Ag NW-CPI film is investigated by applying DC voltage, which demonstrates unprecedentedly reliable and stable characteristics even in dynamic bending condition. To demonstrate the potential application in wearable chemical sensors, NO₂ sensing characteristic of ORGO is investigated with respect to the different heating temperature (22.7-71.7 °C) of Ag NW-CPI film. The result reveals that the ORGO sheets exhibit high sensitivity of 2.69% with reversible response/recovery sensing properties and minimal deviation of baseline resistance of around 1% toward NO₂ molecules when the temperature of Ag NW-CPI film is 71.7 °C. This work first demonstrates the improved reversible NO₂ sensing properties of ORGO sheets on flexible and transparent Ag NW-CPI film assisted by Ag NW heating networks.

All-Nonvacuum-Processed CIGS Solar Cells Using Scalable Ag NWs/AZO-Based Transparent Electrodes

With record cell efficiency of 21.7%, CIGS solar cells have demonstrated to be a very promising photovoltaic (PV) technology. However, their market penetration has been limited due to the inherent high cost of the cells. In this work, to lower the cost of CIGS solar cells, all nonvacuum-processed CIGS solar cells were designed and developed. CIGS absorber was prepared by the annealing of electrodeposited metallic layers in a chalcogen atmosphere. Nonvacuum-deposited Ag nanowires (NWs)/AZO transparent electrodes (TEs) with good transmittance (92.0% at 550 nm) and high conductivity (sheet resistance of 20 Ω/□) were used to replace the vacuum-sputtered window layer. Additional thermal treatment after device preparation was conducted at 220 °C for a few of minutes to improve both the value and the uniformity of the efficiency of CIGS pixel cell on 5 × 5 cm substrate. The best performance of the all-nonvacuum-fabricated CIGS solar cells showed an efficiency of 14.05% with Jsc of 34.82 mA/cm(2), Voc of 0.58 V, and FF of 69.60%, respectively, which is comparable with the efficiency of 14.45% of a reference cell using a sputtered window layer.

Silver Nanowires Binding with Sputtered ZnO to Fabricate Highly Conductive and Thermally Stable Transparent Electrode for Solar Cell Applications

Silver nanowire (AgNW) film has been demonstrated as excellent and low cost transparent electrode in organic solar cells as an alternative to replace scarce and expensive indium tin oxide (ITO). However, the low contact area and weak adhesion with low-lying surface as well as junction resistance between nanowires have limited the applications of AgNW film to thin film solar cells. To resolve this problem, we fabricated AgNW film as transparent conductive electrode (TCE) by binding with a thin layer of sputtered ZnO (40 nm) which not only increased contact area with low-lying surface in thin film solar cell but also improved conductivity by connecting AgNWs at the junction. The TCE thus fabricated exhibited transparency and sheet resistance of 92% and 20Ω/□, respectively. Conductive atomic force microscopy (C-AFM) study revealed the enhancement of current collection vertically and laterally through AgNWs after coating with ZnO thin film. The CuInGaSe2 solar cell with TCE of our AgNW(ZnO) demonstrated the maximum power conversion efficiency of 13.5% with improved parameters in comparison to solar cell fabricated with conventional ITO as TCE.

Conductive Fabric-Based Stretchable Hybridized Nanogenerator for Scavenging Biomechanical Energy

We demonstrate a stretchable hybridized nanogenerator based on a highly conductive fabric of glass fibers/silver nanowires/polydimethylsiloxane. Including a triboelectric nanogenerator and an electromagnetic generator, the hybridized nanogenerator can deliver output voltage/current signals from stretchable movements by both triboelectrification and electromagnetic induction, maximizing the efficiency of energy scavenging from one motion. Compared to the individual energy-harvesting units, the hybridized nanogenerator has a better charging performance, where a 47 μF capacitor can be charged to 2.8 V in only 16 s. The hybridized nanogenerator can be integrated with a bus grip for scavenging wasted biomechanical energy from human body movements to solve the power source issue of some electric devices in the pure electric bus.

Fast Photoconductive Responses in Organometal Halide Perovskite Photodetectors

Inorganic semiconductor-based photodetectors have been suffering from slow response speeds, which are caused by the persistent photoconductivity of semiconductor materials. For realizing high speed optoelectronic devices, the organometal halide perovskite thin films were applied onto the interdigitated (IDT) patterned Au electrodes, and symmetrical structured photoconductive detectors were achieved. The detectors were sensitive to the incident light signals, and the photocurrents of the devices were 2-3 orders of magnitude higher than dark currents. The responsivities of the devices could reach up to 55 mA W(1-). Most importantly, the detectors have a fast response time of less than 20 μs. The light and bias induced dipole rearrangement in organometal perovskite thin films has resulted in the instability of photocurrents, and Ag nanowires could quicken the process of dipole alignment and stabilize the photocurrents of the devices.

Foldable Transparent Substrates with Embedded Electrodes for Flexible Electronics

We present highly flexible transparent electrodes composed of silver nanowire (AgNW) networks and silica aerogels embedded into UV-curable adhesive photopolymers (APPs). Because the aerogels have an extremely high surface-to-volume ratio, the enhanced van der Waals forces of the aerogel surfaces result in more AgNWs being uniformly coated onto a release substrate and embedded into the APP when mixed with an AgNW solution at a fixed concentration. The uniform distribution of the embedded composite electrodes of AgNWs and aerogels was verified by the Joule heating test. The APP with the composite electrodes has a lower sheet resistance (Rs) and a better mechanical stability compared with APP without aerogels. The APP with the embedded electrodes is a freestanding flexible substrate and can be used as an electrode coating on a polymer substrate, such as polydimethylsiloxane and polyethylene terephthalate. On the basis of the bending test results, the APPs with composite electrodes were sufficiently flexible to withstand a 1 mm bending radius (rb) and could be foldable with a slight change in Rs. Organic light emitting diodes were successfully fabricated on the APP with the composite electrodes, indicating the strong potential of the proposed flexible TEs for application as highly flexible transparent conductive substrates.

Synthesis of silver nanowires as a SERS substrate for the detection of pesticide thiram

Silver nanowires with uniform diameters have been synthesized via the rapid sulfide mediated polyol method. The morphology, structure, and properties of as-prepared samples are characterized by UV-Visible spectroscopy, field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD), respectively. The mechanism of as-prepared Ag nanowires is provided and discussed. Moreover, as-prepared Ag nanowires are used as a Surface-Enhanced Raman Scattering (SERS) substrate to detect thiram pesticide. The results show that this substrate based on Ag nanowires exhibits high sensitivity and reproducibility for the thiram detection.

Thin-film copper indium gallium selenide solar cell based on low-temperature all-printing process

In the solar cell field, development of simple, low-cost, and low-temperature fabrication processes has become an important trend for energy-saving and environmental issues. Copper indium gallium selenide (CIGS) solar cells have attracted much attention due to the high absorption coefficient, tunable band gap energy, and high efficiency. However, vacuum and high-temperature processing in fabrication of solar cells have limited the applications. There is a strong need to develop simple and scalable methods. In this work, a CIGS solar cell based on all printing steps and low-temperature annealing is developed. CIGS absorber thin film is deposited by using dodecylamine-stabilized CIGS nanoparticle ink followed by printing buffer layer. Silver nanowire (AgNW) ink and sol-gel-derived ZnO precursor solution are used to prepare a highly conductive window layer ZnO/[AgNW/ZnO] electrode with a printing method that achieves 16 Ω/sq sheet resistance and 94% transparency. A CIGS solar cell based on all printing processes exhibits efficiency of 1.6% with open circuit voltage of 0.48 V, short circuit current density of 9.7 mA/cm(2), and fill factor of 0.34 for 200 nm thick CIGS film, fabricated under ambient conditions and annealed at 250 °C.

Highly reliable ag nanowire flexible transparent electrode with mechanically welded junctions

Deformation behavior of the Ag nanowire flexible transparent electrode under bending strain is studied and results in a novel approach for highly reliable Ag nanowire network with mechanically welded junctions. Bending fatigue tests up to 500,000 cycles are used to evaluate the in situ resistance change while imposing fixed, uniform bending strain. In the initial stages of bending cycles, the thermally annealed Ag nanowire networks show a reduction in fractional resistance followed by a transient and steady-state increase at later stages of cycling. SEM analysis reveals that the initial reduction in resistance is caused by mechanical welding as a result of applied bending strain, and the increase in resistance at later stages of cycling is determined to be due to the failure at the thermally locked-in junctions. Based on the observations from this study, a new methodology for highly reliable Ag nanowire network is proposed: formation of Ag nanowire networks with no prior thermal annealing but localized junction formation through simple application of mechanical bending strain. The non-annealed, mechanically welded Ag nanowire network shows significantly enhanced cyclic reliability with essentially 0% increase in resistance due to effective formation of localized wire-to-wire contact.

Silver nanowire-based electrochemical immunoassay for sensing immunoglobulin G with signal amplification using strawberry-like ZnO nanostructures as labels

The quick development of nanoscience and nanotechnology has paved the way for ultrasensitive biosensing and analysis. In this work, an ultrasensitive electrochemical immunosensor was developed for the detection of human immunoglobulin G (IgG) by combining with a newly designed trace tag on a disposable immunosensor array. The array was prepared by immobilizing captured antibodies on ultralong Ag nanowires, whilst the trace tag was prepared by loading horseradish peroxidase (HRP)-labeled goat anti-human IgG (HRP-anti-IgG) on thionine (TH)-doped mesoporous ZnO nanostrawberries (MP-ZnO). With a sandwich-type immunoassay format, mainly due to crystalline framework and high surface area of the mesoporous (MP) materials, as well as the superconductivity of silver nanowires, the electrochemical signal was significantly amplified. The linear range of the developed immunosensor is 0.01-200 ng mL(-1) and the detection limit is 4 pg mL(-1) IgG, which make the hierarchically nanostructured composites very promising candidates for the next-generation sandwich-type electrochemical immunoassays.