Ag Nanowires Research Articles

Ultrahighly Sensitive Surface-Enhanced Raman Spectroscopy Film of Silver Nanoparticles Dispersed in Three Dimensions on a Thin Alumina Nanowire Framework.

To develop highly sensitive surface-enhanced Raman spectroscopy (SERS) films, various types of aggregated Ag nanowire (NW) and nanoparticle (NP) complex structures were fabricated using anodic aluminum oxide (AAO) templates and thermal evaporation. Aggregated AgNW structures with numerous tapered nanogaps were fabricated via Ag deposition on aggregated thin alumina nanowires of different lengths. AgNP complex structures were obtained by collapsing vertically aligned thin alumina nanowires 1 μm in length and depositing AgNPs on their tops and sides using surface tension during ethanol drying after functionalization. The Raman signal enhancement factors (EFs) of the samples were evaluated by comparing the SERS signal of the thiophenol (TP) self-assembled monolayer (SAM) on the nanostructures with the Raman signal of neat TP. EFs as high as ~2.3 × 107 were obtained for the optimized aggregated AgNW structure (NW length of 1 μm) and ~3.5 × 107 for the optimized AgNP complex structure. The large EF of the AgNP complex film is attributed mainly to the AgNPs dispersed in three dimensions on the sides of the thin alumina nanowires, strongly implying some important, relevant physics yet to be discovered and also a very promising nanostructure scheme for developing ultrahighly sensitive SERS films with EF > 108.

Versatile optical manipulation of trions, dark excitons and biexcitons through contrasting exciton-photon coupling

Various exciton species in transition metal dichalcogenides (TMDs), such as neutral excitons, trions (charged excitons), dark excitons, and biexcitons, have been individually discovered with distinct light-matter interactions. In terms of valley-spin locked band structures and electron-hole configurations, these exciton species demonstrate flexible control of emission light with degrees of freedom (DOFs) such as intensity, polarization, frequency, and dynamics. However, it remains elusive to fully manipulate different exciton species on demand for practical photonic applications. Here, we investigate the contrasting light-matter interactions to control multiple DOFs of emission light in a hybrid monolayer WSe2-Ag nanowire (NW) structure by taking advantage of various exciton species. These excitons, including trions, dark excitons, and biexcitons, are found to couple independently with propagating surface plasmon polaritons (SPPs) of Ag NW in quite different ways, thanks to the orientations of transition dipoles. Consistent with the simulations, the dark excitons and dark trions show extremely high coupling efficiency with SPPs, while the trions demonstrate directional chiral-coupling features. This study presents a crucial step towards the ultimate goal of exploiting the comprehensive spectrum of TMD excitons for optical information processing and quantum optics.

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.

Autonomous Self-Healable, Ag Nanowire-Polymer Composite Flexible Electrode for Underwater Sensors

The development of self-healing electrodes tailored for underwater wearable sensors is paramount to broaden their applications in aquatic environments. However, autonomous self-healing of flexible electrodes, which encompasses both mechanical and electrical performance, remains a formidable challenge. Here, we present the development of a self-healing flexible electrode (AgNW–FPU), incorporating Ag nanowires (AgNWs) and a fluorine functionalized polyurethane (FPU) substrate. The FPU polymer was designed by systematically adjusting the dynamic bonds and chain mobility to achieve fast self-healing speed and efficiency. Higher dynamic bond content and good chain mobility led to the highest self-healing speed, both in air and underwater. The introduction of a fluorinated side chain enhanced hydrophobicity, further improving underwater self-healing. The AgNW–FPU electrode demonstrated fast underwater self-healing, driven by capillary bridges and enhanced contact between fractured nanowires. The AgNW-FPU electrodes were employed in a capacitive pressure sensor, showcasing its potential for underwater sensing applications.

One-step synthesis of ultrathin Ag nanowires with high aspect ratio and their application in transparent conductive films

One-step synthesis of ultrathin Ag nanowires with high aspect ratio and their application in transparent conductive films

Deposition of Transparent Ag Nanowires‐Based Top Electrode for the Development of Double‐Side Green Light Hybrid Photodetector

Herein, various silver nanowires (AgNWs) deposition techniques, i.e., spin coating, Mayer rod coating, and spray coating are used to fabricate ZnO/P3HT‐based double‐side hybrid photodetectors and their photoresponse for 520 nm green light has been compared. The electrodes are coated over the polyethylene terephthalate sheet separately and laminated over the indium tin oxide (ITO)/ZnO/P3HT. Mayer rod‐coated electrodes are found to have a sheet resistance (Rsh) of 24 Ω Sq.−1 and a light transmission of 91%. Additionally, spin‐ and spray‐coated AgNW electrodes exhibit Rsh of 20 and 23 Ω Sq.−1, respectively, along with 80% and 85% transparencies. As the device consists of transparent electrodes on both sides, it can detect light from both the top and bottom sides. Mayer rod‐coated AgNW electrode‐based device has produced better photosensitivity of 1500 (for ITO side illumination) and 630 (for AgNWs side illumination) at λ = 525 nm. Further, the device has demonstrated the responsivity of 124 mAW−1 and specific detectivity of 3 × 1011 Jones.

AgNWs/Fe3O4@NC Conductive Network Hierarchical Assembly to Prepare Flexible EMI Shielding Textile.

With the rapid development of high-power electronic instruments and communication technology, efficient electromagnetic shielding materials with strong absorption of electromagnetic waves and low reflection characteristics have become the focus of the world's attention. This study designs and synthesizes N-doped carbon-coated hollow Fe3O4 nanospheres (Fe3O4@NC) by spraying Ag nanowires (AgNWs) on textiles as conductive networks. Because of the high permeability and hollow structure Fe3O4@NC, electromagnetic wave goes through a unique process of "absorption, reflection, and reabsorption" when it passes through the surface of the composite textile. In X-band (≈8.2-12.4GHz), the average electromagnetic interference shielding effectiveness (EMI SE) reaches 50.1dB, while the reflectance shielding efficiency (SER) is only 2.6dB, and the average reflectance power coefficient (R) is as low as 0.45. The composite fabric has excellent properties and provides an effective strategy for electromagnetic interference shielding based on absorption.

Hierarchical metal-dielectric-metal nanostructures as SERS sensors for sensitive detection of polycyclic aromatic hydrocarbons

Due to the wide variety, inaccessible self-degradation, high mutagenicity and carcinogenicity of polycyclic aromatic hydrocarbons (PAHs), it still remains challenging to efficiently identify them, especially in real environment. Herein, we develop a bottom-up self-assembly strategy to construct a sandwich-like hierarchical metal-dielectric-metal system composed of mercaptan-modified Au nanospheres-graphene oxide (GO)-Ag nanowires as surface-enhanced Raman spectroscopy (SERS) sensors for sensitive detection of PAHs. The synergistic integration of metallic layers and the organic mercaptan and GO layer not only provides localized enhanced electromagnetic field region which is induced by the nanogap between the top Au nanospheres and the bottom Ag nanowires, but also effectively traps PAHs in the middle layer through hydrophobic interaction of mercaptan and π-π stacking interaction of GO. By rationally optimizing the SERS substrates, the lowest detection concentrations of pyrene, anthracene, phenanthrene and benzo[a]pyrene could be reached, respectively, at 10−8 M, 10−8 M, 10−8 M and 10−7 M. The hierarchical system shows excellent uniformity, reproducibility and is able to identify various types of PAHs in multi-component mixtures as well as in real water environment. This strategy can provide a general platform to identify hazardous pollutants that are hydrophobic or contain benzene rings, such as pesticides, dyes and polychlorinated biphenyls.

Polyol synthesis of one-dimensional Ag nanowires for the photocatalytic degradation of textile dye and effective removal of microbes.

Due to the excess release of hazardous pollutants to the environment, the quest for the synthesis of effective nanomaterials for wastewater treatment is never-ending. Present study reports the polyol synthesis of Ag NWs of ~ 85nm diameter and average length of 4.08µm using PVP and ethylene glycol. The experimental data on the methylene blue dye degradation substantiated the photocatalytic efficiency of Ag NWs (88% degradation in 120min). Furthermore, the Ag NWs exhibited microbial load reducing property in air conditioner condensate water (ACW) within a time period of 60min. Also, the anti-bacterial effect of Ag NWs was estimated using two human pathogenic bacterial strains, namely Staphylococcus aureus and Bacillus cereus. The antibacterial potential of Ag NWs against Staphylococcus aureus and Bacillus cereus was revealed significant with an inhibition zone size of 14 ± 0.1mm and 9 ± 0.1mm, respectively. Hence, the present work validates the potential efficiency of Ag NWs in the degradation of textile dyes and reduction of microbial population.

Highly Monochromatic Ultraviolet LED Based on the SnO2 Microwire Heterojunction Beyond Dipole-Forbidden Band-Gap Transition.

SnO2 has been extensively applied in the fields of optoelectronic devices because of its large band gap, high exciton binding energy, and outstanding optical/electrical properties. However, its applications in ultraviolet light-emitting diodes (LEDs) are still hindered by the dipole-forbidden rule. Herein, the dipole-forbidden rule can be conquered by synthesizing Sb-incorporated SnO2 microwires (SnO2:Sb MWs), which are examined by ultraviolet photoluminescence emitting at 363.2 nm and a line width of 11.3 nm. Subsequently, a highly monochromatic ultraviolet light-emitting diode (LED) based on a SnO2:Sb MW heterojunction was constructed with a p-GaN film serving as the hole supplier. In the LED, the presence of a MgO intermediate layer can modulate carrier transport and recombination path, thus achieving band-edge optical transition in the SnO2:Sb MW. As the LED is modified using Ag nanowires, electrical properties, especially for the hole injection efficiency, were dramatically boosted, contributing significantly to the device high brightness. The LED emits at 365.9 nm and a line width of 12.4 nm. Therefore, we have realized a high-brightness and narrow-band ultraviolet LED with the shortest peak wavelength never seen in previously reported SnO2 LEDs. This work will promote the potential applications of low-dimensional SnO2 optoelectronic devices and provide an effective exemplification to overcome the dipole-forbidden rule in metal-oxide materials with "forbidden" energy gaps.

High‐Resolution Intaglio Transfer Printing of Silver Nanowires for Wearable Electrophysiological Sensors

Silver nanowires (NWs) are promising materials for flexible electronics, such as electronic skins due to their excellent electrical, thermal, and mechanical properties. Achieving precise patterning of Ag NWs is essential for the successful integration and miniaturization of the electronic device system, but the high aspect ratio (AR) of NWs and the high porosity of NW networks pose challenges in forming high‐resolution patterns. Herein, the intaglio transfer printing technique to create high‐resolution patterning of ultralong Ag NWs (AR≈1000) is presented. During the pattern formation process, the external force becomes concentrated specifically at the edge of the intaglio trench, resulting in the breaking of the entangled Ag NW network in the corresponding region. This simple yet effective technique enables precise high‐resolution (minimum line width: 7 µm) and complicated Ag NW patterns on flexible substrates. The patterned Ag NWs are conformally attached to the various curvilinear surfaces and show high mechanical stability under continuous bending conditions. Wearable electrophysiological sensors are demonstrated to monitor electromyography and electrocardiogram signals in real‐time for continuous healthcare monitoring. This patterning strategy offers an effective approach for achieving high‐resolution patterns of highly anisotropic nanomaterials and highlights the potential of patterned Ag NWs in wearable electronics.

Universal interface-confined strategy for trough-like AgPtM (M=Ru, Ir, Sn) nanostructures for methanol electro-oxidation

AgPt-based tri-metallic electrocatalyst as an emerging electrocatalyst is demonstrated to have superior catalytic performance. However, it still lacks a universal synthesis strategy currently because of the participation of multiple precursors with different electrical reduction potentials, which is greatly limited to developing high-performance electrocatalysts. Here, a universal interface-confined strategy method is developed to transform the starting Ag nanowires into a series of novel AgPtM (M=Ru, Ir, Sn) alloy nanotroughs at water/air interface. Moreover, owing to their unique trough-like structure, rough surface and the electronic synergistic effect between oxyphilic metals and Pt component, the AgPtM (M=Ru, Ir, Sn) alloy nanotroughs all show enhanced electrocatalytic performance for methanol electro-oxidation. Notably, among all the prepared AgPtM (M=Ru, Ir, Sn) catalysts, the AgPtRu exhibits the best mass activity, ∼ 3.7 and ∼1.65 times higher than that of Pt/C and AgPt nanotroughs counterpart, respectively. This study not only develops a new promising electrocatalyst for methanol oxidation, also provides method guidance for the construction of advanced Pt-based tri-metallic electrocatalysts in practical direct alcohol fuel cell.

Bio-inspired flexible versatile textiles for excellent absorption-dominated electromagnetic interference shielding, thermal management, and strain sensing

Multifunctional flexible textiles are urgently required for wearable electronics and military equipment. However, it remains a big challenge for them to achieve absorption-dominated electromagnetic interference (EMI) shielding and maintain excellent multifunctionalities. Herein, inspired by hierarchical structure of muscle, a novel multilayer self-assembly strategy was proposed to conformally deposit conductive substances and absorption fillers on flexible textiles to realize superior versatility in EMI shielding, thermal management, and strain sensing. The formed muscle-like nanostructure was composed of Ag nanoparticles, Ag nanowires, MXene, and FeCo-C. Benefiting from the 3D cross-linked stable networks with high conductivity (14075.3 S·m−1), durable EMI shielding (85 dB after stretching and bending), and excellent electrical heating (116.3 °C under 1.8 V) were achieved. Based on robust electrostatic interaction between FeCo-C and MXene, strong EMW absorption was realized with a low reflection coefficient (0.168). The textile also demonstrated excellent strain sensing performance in a linear range of 5–60 % with a fast response time (121 ms) for complex motion detection. Besides, the textiles had good gas permeability, ensuring long-term wearable comfortability. This work offers a significant paradigm to construct multifunctional flexible textiles for next-generation integrated flexible electronic devices and military equipment with practical applications.

Synthesis of Ag nanowires with an aspect ratio higher than 2000 for the fabrication of transparent conductive film

Synthesis of Ag nanowires with an aspect ratio higher than 2000 for the fabrication of transparent conductive film

Interface-confined precise processing of Ag nanowire into AgPd-nanoparticle-sealed AgAu nanotroughs for boosting ethanol electrooxidation

The functions of nanomaterials are closely linked with their fine structures and compositions. Precisely processing nanoparticles into morphology- and composition-varied nanostructures can a cutting-edge technology for producing complex nanostructures. Herein, we develop an interface-confined precise processing strategy towards toluene/water-interfacial Ag nanowires. Interfacial Ag nanowires are transformed into AgPd-nanoparticle-sealed AgAu nanotroughs with abundant AgPd/AgAu hetero-junctions (i.e., AgPdAu hetero-junction nanostructures). By adjusting the reaction conditions, composition-varied AgPdAu hetero-junction nanostructures can be obtained. The formation of AgPdAu hetero-junction nanostructures can be attributed to interface-confined precise etching towards Ag nanowires separately from the two subphases of the water and the toluene. Composition-optimized Ag13Pd67Au20 hetero-junction nanostructure shows satisfactory catalytic performance towards ethanol electrooxidation: ∼4 and 2 times in electrochemical-activity-surface-area-normalized activities; ∼6 and 5 times in mass-normalized activities higher than commercial Pd/C and Pt/C, respectively. The outstanding catalytic capability of Ag13Pd67Au20 may be attributed to optimized composition, porous nanostructures as well as abundant AgPd/AgAu hetero-junctions. This work demonstrates the feasibility of precisely processing interfacial nanoparticles, opening the way for creating morphology-well-defined composition-varied complex nanostructures.

Plasmon-induced hot-electron injection effect: mechanism of performance enhancement for ZnO MSM hybrid photodetector by introducing Ag NWs and MXene

In this paper, a performance-enhanced hybrid ultraviolet metal–semiconductor–metal photodetector (UVPD) has been produced. This device incorporates a mixed photosensitive layer consisting of MXene nanoflakes that are covered on a thin film formed by Ag nanowires (NWs) wrapped in ZnO nanoparticles. This configuration, referred to as ZnO@Ag NWs/Mxene, capitalizes on the hot electrons generated by the localized surface plasmon resonance phenomenon occurring in the Ag NWs and MXene. These hot electrons possess sufficient energy to traverse the interface depletion layer and reach the ZnO layer. Therefore, the injected hot electrons serve as additional photo carriers in the ZnO layer, thereby increasing the number of photo-generated carriers and improving the carrier concentration in ZnO. The improved UVPD device exhibits an amplified photocurrent of ∼2499.35 nA at 5 V, under a light intensity of 6.52 mW cm−2 and a wavelength of 365 nm. Simultaneously, it achieves enhanced performance indices, including an On/Off ratio of ∼984.19, a responsivity (R p) of ∼66.87 mA W−1, and a detectivity (D *) of ∼1.82 × 1011 jones. These values represent a significant improvement compared to devices based solely on the ZnO configuration, with enhancements of ∼24.90, 3.93, 23.38, and 9.33 times, respectively. Based on the obtained results, it can be inferred that employing the hot electron injection effect to design and enhance the performance of optoelectronic devices based on wide band gap semiconductors is a reasonable and effective strategy.

Influence of bimodal copper grain size distribution on electrical resistivity and tensile strength of silver - copper composite wires

In order to obtain the best compromise between high strength and low resistivity it was decided to introduce a controlled content of copper (Cu) large grains in copper-silver (Ag-Cu) composite wires. Composite powders are prepared by mixing of 1 vol% Ag nanowires and bimodal Cu powder. The so-obtained composites powders are consolidated into cylinders (8 mm in diameter and 30 mm long) by Spark Plasma Sintering (SPS) at only 450 °C. The cylinders served as starting materials for room temperature wire-drawing (WD) for the preparation of fine wires (1–0.2 mm diameter). The microstructure of the cylinders and the wires was investigated by scanning electron microscopy imaging and electron backscattered diffraction analysis. The electrical resistivity and the tensile strength were measured at 293 K and 77 K. The electrical resistivity of the wires is the lowest when the large Cu grain content is the highest. Cu large grains greatly limit the electronic scattering, forming areas with few grain boundaries and no Ag/Cu interfaces and therefore can be considered as fast conduction channels. Conversely, the addition of Cu large grains leads to a moderate decrease in mechanical strength. By presenting a 12 % lower electrical resistivity and an equivalent ultimate tensile strength (UTS) wires with bimodal Cu matrix show a better compromise between low electrical resistivity and high UTS (0.45 μΩ cm, 1082 MPa at 77 K) compared to wires with a fine-grained Cu matrix (0.51 μΩ cm, 1138 MPa at 77 K).

Chemically-stable flexible transparent electrode: gold-electrodeposited on embedded silver nanowires

Silver nanowires (AgNWs) with a low diameter, high aspect ratio, stable suspension, and easy synthesis have recently attracted the optoelectronic industry as a low-cost alternative to indium tin oxide transparent conductive films. However, silver nanowires are not chemically stable, and their conductivity diminishes over time due to reactions with atmospheric components. This is a bottleneck for their wide industrial applications. In this study, we aim to address this issue by synthesizing silver nanowires with an average diameter of approximately 65 nm and a length of approximately 13 µm. The prepared Ag nanowires are then applied to fabricate transparent, flexible, and chemically stable conductive films. The fabrication includes spraying of silver nanowires suspension on a glass substrate followed by Dr. blade coating of polystyrene (PS) solution and delamination of the PS-AgNWs film. The resulting film exhibits an optimum sheet resistance of 24 Ω/□ and transmittance of 84%. To further enhance the stability of the transparent conductive film, the facial and scalable double pulse electrodeposition method is used for coating of gold on the exposed surface of the AgNWs embedded in PS. The final transparent film with gold coating demonstrates a remarkable stability under harsh conditions including long exposure to UV light and nitric acid solution. After 100 min of UV/Ozone treatment, the increase in sheet resistance of the optimal PS-AgNW@Au sample is 15.6 times lower than the samples without gold coating. In addition, the change in sheet resistance after 2000 bending cycles in the optimal PS-AgNW@Au electrode is measured and it showed an increase of only 22% of its initial sheet resistance indicating its good flexibility. The proposed electrode performs an excellent chemical stability, good conductivity, transparency, and flexibility that makes it a potential candidate for various optoelectronic devices.

Tunable random laser based on hybrid plasmonic enhancement.

This research investigates the hybridized plasmonic response of silver film combined with dispersed silver (Ag) nanowires (NWs) to random laser emission. The mixture of Rhodamine B (RhB) dye and polyvinyl alcohol (PVA) matrix is taken as the gain medium for random lasing, and the silver combination provides feedback mechanisms for light trapping. Importantly, film roughness and the coupling between localized and extended (delocalized) surface plasmons play a vital role in RL performance evaluation. The laser threshold is strongly influenced by film thickness attributed to surface roughness. Furthermore, the variation in film thickness also supports the wavelength modulation of 9 nm (597 nm to 606 nm), which results from the reabsorption of RhB. Additionally, the intriguing capability of emission wavelength tuning under the variation of temperature facilitates exciting prospects for precise wavelength control in plasmonic devices.

Creating tunable lateral optical forces through multipolar interplay in single nanowires

The concept of lateral optical force (LOF) is of general interest in optical manipulation as it releases the constraint of intensity gradient in tightly focused light, yet such a force is normally limited to exotic materials and/or complex light fields. Here, we report a general and controllable LOF in a nonchiral elongated nanoparticle illuminated by an obliquely incident plane wave. Through computational analysis, we reveal that the sign and magnitude of LOF can be tuned by multiple parameters of the particle (aspect ratio, material) and light (incident angle, direction of linear polarization, wavelength). The underlying physics is attributed to the multipolar interplay in the particle, leading to a reduction in symmetry. Direct experimental evidence of switchable LOF is captured by polarization-angle-controlled manipulation of single Ag nanowires using holographic optical tweezers. This work provides a minimalist paradigm to achieve interface-free LOF for optomechanical applications, such as optical sorting and light-driven micro/nanomotors.