Metallic Nanowires Research Articles

Insight into the morphological instability of metallic nanowires under thermal stress

HypothesisMetallic nanowires, particularly polyol-grown silver nanowires, exhibit a morphological instability at temperatures significantly lower than their bulk melting point. This instability is commonly named after Rayleigh's description of the morphological instability of liquid jets, even though it has been shown that its quantitative predictions are not consistent with experimental measurements. In 1996, McCallum et al. proposed a description of the phenomenon assuming a solid wire lying on a substrate. It is assumed that the latter description depicts more accurately the reality. ExperimentsNanowires with varying diameters have been deposited on silicon wafers. Statistical analysis of their radius and the wavelength of their periodical instability have been performed. FindingsMcCallum et al.'s model better aligns with experimental observations compared to Rayleigh's description. This validation provides a robust theoretical framework for enhancing the stability of nanowires, addressing a crucial aspect of their development.

Dielectric pocket engineered, gate induced drain leakages (GIDL) and analog performance analysis of dual metal nanowire ferroelectric MOSFET (DPE-DM-NW-Fe FET) as an inverter

Dielectric pocket engineered, gate induced drain leakages (GIDL) and analog performance analysis of dual metal nanowire ferroelectric MOSFET (DPE-DM-NW-Fe FET) as an inverter

Construction of biodegradable superhydrophilic/underwater superoleophobic materials with CNF (cellulose nanofiber) fence-like attached on the surface for efficient oil/water emulsion separation

Superhydrophilic/underwater superoleophobic materials for the separation of oil-water emulsions by filtration have received much attention in order to solve the pollution problem of oil-water emulsion. In this paper, a fence-like structure on the surface of CNF/KGM (Konjac Glucomannan) materials by a simple method using CNF instead of metal nanowires was successfully developed based on the hydrogen bonding of KGM and CNF. The resulted organic CNF/KGM materials surface has outstanding superhydrophilic (WCA = 0°) in air and superoleophobicity (OCA≥151°) in water, which could separate oil-water mixtures with high separation efficiency above 99.14 % under the pressure of the emulsion itself. The material shows good mechanical properties because of the addition of CNF and has outstanding anti-fouling property and reusability. More importantly, the material can be completely biodegraded after buried in soil for 4 weeks since both of KGM and CNF are organic substances. Therefore, it may have a broad application prospect in the separation of oil-water emulsion because of its outstanding separation properties, simply preparation method and biodegradability.

Induced-charge electrophoresis of a tilted metal nanowire near an insulating wall.

Electric fields are commonly used to control the orientation and motion of microscopic metal particles in aqueous suspensions. For example, metallodielectric Janus spheres are propelled by the induced-charge electro-osmotic flow occurring on their metallic side, the most common case in electrokinetics of exploiting symmetry breaking of surface properties for achieving net particle motion. In this work, we demonstrate that a homogeneous metal rod can translate parallel to a dielectric wall as a result of the hydrodynamic wall-particle interaction arising from the induced-charge electro-osmosis on the rod surface. The applied electric field could be either dc or low-frequency ac. The only requirement for a nonvanishing particle velocity is that the axis of the rod be inclined with respect to the wall, i.e., it cannot be neither parallel nor perpendicular. We show numerical results of the rod velocity as a function of rod orientation and distance to the wall. The maximum particle velocity is found for an orientation of between ∼30^{∘} and ∼50^{∘}, depending on the position and aspect ratio of the cylinder. Particle velocities of up to tens of µm/s are predicted for typical conditions in electrokinetic experiments.

Heat-induced morphological changes in silver nanowires deposited on a patterned silicon substrate.

Metallic nanowires (NWs) are sensitive to heat treatment and can split into shorter fragments within minutes at temperatures far below the melting point. This process can hinder the functioning of NW-based devices that are subject to relatively mild temperatures. Commonly, heat-induced fragmentation of NWs is attributed to the interplay between heat-enhanced diffusion and Rayleigh instability. In this work, we demonstrated that contact with the substrate plays an important role in the fragmentation process and can strongly affect the outcome of the heat treatment. We deposited silver NWs onto specially patterned silicon wafers so that some NWs were partially suspended over the holes in the substrate. Then, we performed a series of heat-treatment experiments and found that adhered and suspended parts of NWs behave differently under the heat treatment. Moreover, depending on the heat-treatment process, fragmentation in either adhered or suspended parts can dominate. Experiments were supported by finite element method and molecular dynamics simulations.

Correction: Improved analog and AC performance for high frequency linearity based applications using gate-stack dual metal (DM) nanowire (NW) FET (4 H-SiC)

Correction: Improved analog and AC performance for high frequency linearity based applications using gate-stack dual metal (DM) nanowire (NW) FET (4 H-SiC)

Tuning the Structure of Pd@Ni-Co Nanowires and Their Electrochemical Properties.

One-dimensional transition metal materials are promising supports for precious metals used in energy production processes. Due to their electrochemical properties, 3d-group metals (such as Ni, Co, and Fe) can actively interact with catalysts by a strong metal-support interaction. This study shows that changing the Ni:Co ratio makes it possible to modulate the structure of the catalyst supports, which, in turn, provides a tool for designing their electrical and electrochemical properties. For example, Ni1-Co9 shows the highest electrical conductivity (5.8-10-4 S/cm) among all of the materials examined. On the contrary, the Pd@Ni7-Co3 system presents the highest mass activity (>2000 mA mg-1) at 0.7 V, exceeding by several times that of commercial Pt/C (>300 mA mg-1) at the same potential. Our study opens the gateway for applications of bimetallic transition metal nanowires in catalytic conversion and energy production processes.

7.4 nm linewidth Pt nanowires by electron-beam lithography using non-chemically amplified positive-tone resist and post-exposure bake

Abstract 7.4 nm linewidth Pt nanowires were demonstrated on SiO2/Si substrates via electron-beam lithography using a non-chemically amplified positive resist ZEP520A and post-exposure bake (PEB) treatment. The effect of the PEB treatment conditions on the nanowires’ characteristics was investigated. As the PEB temperature and time increased, a decrease in the mean linewidth and an improvement of the line-width (line-edge) roughness of the nanowires were observed. Pt nanowires with an ultrafine linewidth of 7.4 nm were successfully fabricated using the optimal condition of 100 °C for 2 min, verifying the effectiveness of PEB for fabricating sub-10 nm linewidth robust metal nanowires.

Polyethyleneimine Controlled Impregnation of Silver Nanowires on Electrospun Ceramic Sponges

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

Mid-infrared deep subwavelength confinement in graphene plasmonic waveguides

Strong optical field intensity is greatly desired in mid-infrared (MIR) photonics to confine light on miniaturized compact-size chips. However, due to a fundamental trade-off between energy confinement and propagation loss, it has been a challenging task to obtain further deep subwavelength confinement. In this study, we present a simple graphene waveguide that generates image plasmons assisted by metallic cylindrical nanowires operating at a wavelength of 15 μm. Due to high-mobility graphene encapsulated by hexagonal boron nitride (hBN) and ultra-confined image plasmonic mode, the resulting waveguide has two orders of magnitude smaller mode area than the strongest confinement waveguides to date (up to an order of 10−8), in conjunction with comparable loss (a few micrometers of propagation distance). Furthermore, by the tunable graphene locations in the gap, we implement an efficient manipulation of the mode area across an order of magnitude. Such high-performance waveguides may be exploited for deep subwavelength field-enhanced devices, which promise to be unprecedented pathways for nanoscale transmission and manipulation of MIR light.

Broadband-tunable quarter wave plates based on paired metal nanowire grids

Ultrathin wave plates based on metallic and dielectric metasurfaces have attracted much attention for independently controlling the phase, amplitude, and polarization of incident light. However, the issues of narrow bandwidth and low polarization conversion need to be improved for their optical applications. In this study, we show that an array of paired metal nanowire grids (PMNG) covered with a dielectric layer controls the polarization state in a broadband of visible to mid-infrared wavelengths. By analyzing the phase difference and amplitude ratio of orthogonal electric-field components passing through the SiO2-covered PMNGs, it is observed that the wavelengths operating as a circular polarizer appear regularly in the range from 450 nm to 4.0 μm with a stable phase difference of π/2. Also, the array of PMNG continuously converts linear polarization into circular or elliptical polarization by rotating the polarization angle of the incident light. Then, we demonstrate experimentally accessible polarization control by investigating the change in polarization ellipse between input and output light for this PMNG structure. Moreover, the PMNG can play an effective role as a wire grid polarizer in the IR region. Therefore, the suggested PMNG platform can be variously applied to emerging fields requiring ultrathin, multifunctional, and high-performance planar polarization components.

Rational design of MoS2@M (M=Sn, Cu, Ni, Co) hybrid nanostructures for enhanced electrocatalytic hydrogen evolution reaction

MoS2 has attracted attraction in electrocatalytic hydrogen evolution reaction (HER). The low electrical conductivity and limited exposure of active sites hindered the electrocatalytic efficiency of MoS2. In this paper, we design MoS2@M (M = Sn, Cu, Ni, Co) hybrid nanostructures by growing MoS2 nanosheets on the surface of M (M = Sn, Cu, Ni, Co) nanowires. Due to the high conductivity of metal nanowires and the increased HER active sites, the MoS2@M (M = Sn, Cu, Ni, Co) hybrid nanostructures show a superior HER efficiency. In alkaline media, the MoS2@M (M = Sn, Cu, Ni, Co) hybrid nanostructures exhibit the low overpotential of 130–172 mV at the current density of 10 mA/cm2 and a small Tafel slope of 61–86 mV/dec. In addition, the MoS2@M (M = Sn, Cu, Ni, Co) hybrid nanostructures also possess excellent electrocatalytic durability. This work provides an efficient way to achieve highly efficient MoS2 based electrocatalysts for water splitting.

Analysis of the effect of size, material, position and period of metal nanowires on the performance of thin film solar cells

Analysis of the effect of size, material, position and period of metal nanowires on the performance of thin film solar cells

Atomistic modeling of plastic deformation in BCC niobium nanowire under bending

Design of high-performance nanodevices require nanowires with optimized bending properties, which relies on a thorough understanding of the mechanical behavior of nanowires. To explore the mechanism underlying bending plasticity of the nanowire, we adopted a 〈110〉-oriented body-centered cubic (BCC) Nb nanowire as the model system and performed bending tests at various temperatures by means of molecular dynamics simulation. Our results reveal that the BCC Nb nanowire bends plastically and homogeneously into a smoothed arc shape with significant curvature by slip of perfect dislocations, showing excellent bending plasticity and toughness. The generated dislocations are identified as geometrically necessary dislocation for accommodating the strain gradient related to bending, and they accumulate linearly with the bending angle to a value of an order of 1017 m−2. Temperature dependence was found in both elastic modulus and yield strength of the nanowire. In particular, we find that a completely dislocation-mediated plasticity at high temperature changes into a deformation mechanism involving predominant dislocation slip plus additional anti-twinning as temperature is reduced. Both development of high dislocation density and reduced mobility of dislocation at low temperature contribute to the initiation of anti-twinning. Our findings not only enrich the current understanding of deformation behavior of BCC nanomaterials under non-uniaxial load, but also provide valuable information for design of flexible and stretchable nanodevices based on metallic nanowires.

Plasmonic-nanowire near-field beam analyzer

Abstract Experimental near-field analysis of the output beams from the end faces of micro/nano-waveguide is very necessary, because important information such as spatial intensity distributions, mode orders, and divergence angles can be obtained, and are very important for investigating and designing nanophotonic devices. However, as far as we know, it has not been demonstrated yet. In this work, we experimentally demonstrate a plasmonic-nanowire near-field beam analyzer, utilizing a single Au nanowire (AuNW) as the probe to scan the spatial near-field distributions of emitted beams from micro/nano-waveguide end-faces. Our analyzer can resolve the trade-off between high measurement resolution and light collection efficiency in conventional beam analyzers by a reverse nanofocusing process, achieving a probe resolution of 190 nm (<λ/8) and a simulated collection efficiency of ∼47.4 % at λ = 1596 nm. These attractive advantages allow us to obtain three‐dimensional (3D) scanning in a large range from the plasmonic hotspot region to the far-field region, characterizing the 3D spatial distribution evolution from a metal nanowire output beam for the first time, with an M 2 factor lower than that of the ideal Gaussian beam (M 2 = 1). In addition, the analyzer also demonstrates simultaneous characterization of multimodes in irregular and large-sized nanoribbons, further verifying its ability to selectively explore complex multimodes that are difficult to be predicted by numerical simulations. Our results suggest that this plasmonic-nanowire beam analyzer may hold promise for diverse near-field applications for micro/nano-waveguides such as nanolasers and biosensing, and offer a new method for understanding nanophotonic structures.

Zig-zag surface step migration and structure modulation in metallic nanowires

Nanoscale metals frequently exhibit novel mechanical properties or physiochemical performances, due to the growing influence of surfaces. Here, we uncover a unique surface-mediated deformation behavior of Au nanowires by conducting in situ transmission electron microscope tensile testing. A zig-zag migration of surface steps via the transverse slips on alternate (111) and (001) planes is revealed in [112]-oriented Au nanowire, which contributes to unexpected uniform deformation with an elongation of 108.9%. Further, we discover that the unusual (001) slip can induce an anomalous stacking structure on the nanowire surface under uniaxial tension. These findings enrich our understanding of surface-mediated plasticity in metallic nanomaterials.

Adaptive Epidermal Bioelectronics by Highly Breathable and Stretchable Metal Nanowire Bioelectrodes on Electrospun Nanofiber Membrane

AbstractThe potential of the electrospun nanofiber membrane (ENM)‐based soft electronics in epidermal bioelectronics has gained huge attention with their conformal compatibility with the human body and associated performance improvements. This study presents a novel filtration‐based direct local nanowire patterning method on the ENM using dispenser systems, aiming to fabricate stretchable, breathable, and highly conductive epidermal electronics harnessing various types of metal nanowires, including Ag, Ag@Au core–shell, and Ag@(Au–Pt) core–shell nanowires. By utilizing capillary force from a support bed beneath the ENM, efficient fluid flow can be achieved, eliminating the requirement for expensive vacuum equipment typically employed in filtration processes. In the postprocessing phase, the photothermal effect of a laser is harnessed to improve the mechanical stability of the nanowire–ENM interface. The maskless fabrication process is instrumental in crafting epidermal bioelectronics in that the design can be spontaneously replicated according to diverse human body geometries in situ. The selective insulation process can be also executed with the same dispenser system, streamlining the overall fabrication system. Applications are demonstrated showcasing the advantages of the presented fabrication system and the resulting devices, including an in vivo epicardial signal recording electrode, an epidermal electrochemical biosensor, and a customized epidermal electromyography (EMG)‐based human–machine interface (HMI).

Inorganic Hydrogel Based on Low-Dimensional Nanomaterials.

Composed of three-dimensional (3D) nanoscale inorganic bones and up to 99% water, inorganic hydrogels have attracted much attention and undergone significant growth in recent years. The basic units of inorganic hydrogels could be metal nanoparticles, metal nanowires, SiO2 nanowires, graphene nanosheets, and MXene nanosheets, which are then assembled into the special porous structures by the sol-gel process or gelation via either covalent or noncovalent interactions. The high electrical and thermal conductivity, resistance to corrosion, stability across various temperatures, and high surface area make them promising candidates for diverse applications, such as energy storage, catalysis, adsorption, sensing, and solar steam generation. Besides, some interesting derivatives, such as inorganic aerogels and xerogels, can be produced through further processing, diversifying their functionalities and application domains greatly. In this context, we primarily provide a comprehensive overview of the current status of inorganic hydrogels and their derivatives, including the structures of inorganic hydrogels with various compositions, their gelation mechanisms, and their exceptional practical performance in fields related to energy and environmental applications.

Wet Film Leveling for Promoting the Uniformity and Conductivity of Silver Nanowire Transparent Electrode.

Wet film leveling can greatly promote film uniformity. However, in the field of metal nanowire, wet film leveling is rarely mentioned. For low-viscosity inks like metal nanowire ink, how to realize wet film leveling is still unclear. Herein, we study the wet film leveling of silver nanowire ink and systematically investigate the relationship between leveling effect and influence factors: (1) there is a uniformity-promotion limit for traditional methods, while wet film leveling can break through this limit and further promote the film uniformity; (2) for wet film leveling, lowering ink's surface tension has no effect, and eliminating surface tension gradient by high-surface-tension leveling agent is the main task; (3) leveling process includes wet film destruction process and ink reflow process; (4) in the destruction process, the leveling-agent solubility and quantity dominate the leveling effect, while the influence of surface tension is little; (5) for solubility and quantity, there is a suitable range to realize optimum leveling effect, and the leveling effect exhibits a contrary relationship with the solubility in a suitable range (2-11%); (6) in the reflow process, the main influence factor is ink viscosity, and the leveling effect exhibits a contrary relationship with ink viscosity. After being leveled by 1.5% n-pentanol, the sheet resistance and sheet-resistance variation coefficient of film decrease from 38.3 Ω/sq/3.83% to 25.7 Ω/sq/1.88%. Further study reveals that the film improvement is not from the ink wettability and drying. Above theoretical results possess certain universality for film preparation by a wet process and can be used by the science and industry field.

Design of Light-Driven Biocompatible and Biodegradable Microrobots Containing Mg-Based Metallic Glass Nanowires.

Light-driven microrobots capable of moving rapidly on water surfaces in response to external stimuli are widely used in a variety of fields, such as drug delivery, remote sampling, and biosensors. However, most light-driven microrobots use graphene and carbon nanotubes as photothermal materials, resulting in poor biocompatibility and degradability, which greatly limits their practical bioapplications. To address this challenge, a composition and microstructure design strategy with excellent photothermal properties suitable for the fabrication of light-driven microrobots was proposed in this work. The Mg-based metallic glass nanowires (Mg-MGNWs) were embedded with polyhydroxyalkanoates (PHA) to fabricate biocompatible and degradable microrobots with excellent photothermal effect and complex shapes. Consequently, the microrobot can be precisely driven by a near-infrared laser to achieve high efficiency and remote manipulation on the water surface for a long period of time, with a velocity of 9.91 mm/s at a power density of 2.0 W/cm2. Due to the Marangoni effect, programmable and complex motions of the microrobot such as linear, clockwise, counterclockwise, and obstacle avoidance motions can be achieved. The biocompatible and degradable microrobot fabrication strategy could have great potential in the fields of environmental detection, targeted drug delivery, disease diagnosis, and detection.