Structure Of Silver Nanowires Research Articles

Synthesis and morphology of Ag nanowires by fiber template method

The synthesis of traditional silver nanowires often uses a polyol method. There are many factors that affect the structure of silver nanowires, such as silver ion concentration, type and amount of reducing agent, oxygen concentration, stirring speed, temperature, and time. The synthesis conditions are harsh and difficult to replicate. In this paper, natural fibers and synthetic fibers were used as templates to assist the polyol reduction method to obtain silver nanowires with uniform structure. The effect of fiber types on the structure of silver nanowires were studied, including hemp fibers, wheat straw fibers, tobacco stem fibers, and polycarbonate fibers. Polycarbonate fibers induced the synthesis of silver nanowires with the highest aspect ratio, highest yield, and most uniform diameter distribution. The effect of polycarbonate fibers concentrations on the morphology and conductivity of silver nanowires were also studied. When the polycarbonate mass concentration was 8.5 × 10−4 g/mL, the aspect ratio of silver nanowires was the highest. The effect of polycarbonate fibers length (2 mm\\5 mm\\7 mm) on the morphology of silver nanowires were also studied. When the length of the template polycarbonate fibers was 7 mm, the length to diameter ratio and conductivity of the nanowires obtained are the best. Furthermore, the reaction kinetics of the reaction were studied via multiple sampling of silver nanowire reaction solutions and characterized by using UV–visible spectroscopy and scanning electron microscopy. The synthesis method of silver nanowires using fiber template is simple and fast, and can be used to synthesize silver nanowires with uniform diameter distribution on a large scale, thus solving the bottleneck problem of harsh synthesis conditions for silver nanowires. The resulting silver nanowires were blended with carboxymethyl cellulose to prepare conductive inks, which were coated on paper and cured at 180 °C for 30 min to achieve good conductivity.

High-performance lithium metal anode enhanced by multifunctional film of PAN@AgNWs with antimicrobial activity

Lithium metal is expected to be the perfect anode material for the next generation of rechargeable batteries owing to its ultra-high theoretical specific capacity, low density and the lowest redox potential. However, the practical application of lithium metal batteries faces serious challenges, including uneven lithium deposition, negative electrode volume expansion, and short circuits brought by dendritic protrusions. Although the 3D structure of silver nanowires is effective in inhibiting lithium dendrite growth and lithium metal volume expansion, it still suffers from lithium inhomogeneity caused by uneven distribution of silver nanowires and complicated preparation. Therefore, PAN@AgNWs collector was prepared by a simple suction filtration method, and uniform dispersion of silver nanowires and uniform deposition of lithium were achieved. Lithium nucleation overpotential and lithium dendrite formation can be effectively reduced by PAN@AgNWs hosts due to the reduction of local current density by 3D collectors and the improved lithiophilicity of silver nanowires. With low voltage hysteresis, the symmetric battery constructed with its composite anode may cycle steadily for 4500 h at 1 mA cm−2 and 1 mAh cm−2. At the same time, the Li-PAN@AgNWs||LFP full cell still possesses a reversible of 144.18 mAh g−1 after 500 cycles at 1C. Moreover, due to large specific surface area and high surface energy of 3D silver nanowires, it exhibits excellent antimicrobial properties, with an inactivation efficiency of 96.3 % after contacting with E. coli for 2.5 h. This work shows the possibility of using PAN@AgNWs in a large scale for LMBs, and paves the way for development of high-performance antimicrobial materials.

Ultrathin Aramid Nanofiber Composites with Alternating Multilayered Structure of Silver Nanowires and Boron Arsenide: Toward Superior Electrically Insulating Thermoconductive Electromagnetic Interference Shielding Materials

Ultrathin Aramid Nanofiber Composites with Alternating Multilayered Structure of Silver Nanowires and Boron Arsenide: Toward Superior Electrically Insulating Thermoconductive Electromagnetic Interference Shielding Materials

Influence of molecular weight of PVP on the structure of silver nanowires for EMI shielding application

A material with high visual transparency and excellent electromagnetic interference efficiency (EMI SE) at microwave frequencies is the need of the hour for emerging electronic devices. Silver nanowires (AgNWs) are the best alternative to match the commercially used indium tin oxide (ITO) films. Poly (vinylpyrrolidone) (PVP), being the crucial parameter in the preparation of AgNWs, plays an important role in deciding the crystallinity and aspect ratio of AgNWs. In this paper, the molecular weight of PVP is varied (40000, 360000, and 1300000) by keeping other parameters constant in the modified polyol method to understand the structural and morphological properties of the prepared AgNWs. As-synthesized AgNWs are spin-coated on the glass substrate and studied for visible transparency and EMI shielding performance. It is found that optical transparency and EMI SE are inversely related. For 80% visible transparency, a shielding of 20 dB is achieved, while for 42% transparency, a shielding of 37.5 dB is achieved in the frequency range between 8 and 12 GHz.

Highly transmitted silver nanowires-SWCNTs conductive flexible film by nested density structure and aluminum-doped zinc oxide capping layer for flexible amorphous silicon solar cells

• Ag NWs-SWCNTs (AS) composites with high and sparse density networks were fabricated by ultrasonic. • The AS/AZO (ASA) bilayer showed superior transmittance (92%@550 nm), mechanicity, stability, and adhesion. • The film demonstrates high stability with a ΔR/R 0 = 10% after 10,000 bending times, boiling, taping, and CO 2 plasma. • The power conversion efficiency of photovoltaic devices with flexible ASA TCFs was increased by 26%. • No significant reduction in power conversion efficiency was observed even after bending for 3000 times. Indium tin oxide (ITO) is widely used in transparent conductive films (TCFs); however, several disadvantages, such as high cost and toxicity of indium, limit its applications. Therefore, it is necessary to develop other materials that can replace ITO. Silver nanowires or single walled carbon nanotubes (SWCNTs) have attracted considerable interest owing to their unique electrical, optical, and thermal stabilities, and thus, they are ideal for transparent electrodes for flexible or stretchable devices. In this study, we develop a novel architecture of composite TCFs on a polyethylene naphthalate (PEN) flexible substrate. Herein, the silver nanowires-SWCNTs films with nested density structure were fabricated through ultrasonic spraying technology by varying the spraying width. For achieving enhanced transmittance, we combined the larger irregular grids and holes with fewer nanowires stacked in the longitudinal direction, more optical channels, and good carrier transport. Thereafter, aluminum-doped zinc oxide (AZO) was used as capping to the structure for enhancing the optical properties of the TCFs. The silver nanowires-SWCNTs/AZO (ASA) bilayer was obtained in the optimized architecture, which showed superior optoelectronic performance to that shown by commercial ITO with a high optical transmittance of 92% at the wavelength of 550 nm and low sheet resistance of 17 Ω/sq. In the specially structured conductive film, the significant improvement in the transmittance and uniformity of the sheet resistance was attributed to the effective nanowire junction contact compared to that in ordinary structure of silver nanowires, which reduced the mean density of small clusters of nanowires. Compared with the silver nanowires-SWCNTs films, the ASA bilayer film exhibited excellent resistance to boiling, mechanical bending (10,000 cycles), and CO 2 plasma. Moreover, the sheet resistance of ASA changed slightly after the tape tests, thereby illustrating a strong adhesion to the PEN substrate after the enclosure of AZO. Meanwhile, the AZO capping layer can enhance the optical transmittance between 600 and 1500 nm. In addition, the amorphous silicon photovoltaic devices with flexible ASA TCFs exhibited a power conversion efficiency (PCE) of 8.67%. After bending for 3000 times, the PCE was decreased to 8.20%, thereby demonstrating the potential of developed films to replace traditional ITO.

Low-temperature nanowelding silver nanowire hybrid flexible transparent conductive film for green light OLED devices

Flexible organic light emitting diodes (OLED) have attracted great attention in many applications. MXene based flexible transparent conductive films (TCFs) are the most promising next-generation electrodes for flexible electronics. Herein, the sandwich conductive structure of silver nanowires (AgNWs) network, new 2D nanosheets with excellent conductivity, hydrophilicity and mechanical flexibility and PEDOT:PSS contributes to a highly transparent and conductive hybrid electrode through a simple, scalable, low-cost spray method. The Ti3C2T x /AgNWs/PEDOT-PET film shows a low sheet resistance (<30 Ω/sq) and high transmittance (>80%) at 550 nm. Flexible OLED with such hybrid anode has the maximum brightness, current efficiency and current density, as high as 10 040 cd m−2, 3.7 cd A−1 and 535.5 mA cm−2, respectively. These results indicate that the novel Ti3C2T x /AgNWs/PEDOT-PET TCFs have a great potential for high-performance flexible optoelectronic devices.

Flexible piezoresistive pressure sensor based on wrinkled layers with fast response for wearable applications

Flexible piezoresistive sensors are promising candidates for vital components of prospective wearable sensing systems in human-centered intelligent applications. Herein, we present a novel flexible piezoresistive pressure sensor based on the structure of silver nanowires (AgNWs) on polydimethylsiloxane (PDMS) with a wrinkled surface. Modifying the PDMS microstructure enables the sensor to obtain different sensitivities and pressure ranges. At the optimal conditions, our sensor exhibits a high sensitivity of 2.588 kPa−1 and a large pressure range with a very low detectable pressure limit (<1 Pa), which can measure a seed weight of sesame (∼2 mg). Furthermore, The elastic microstructure-based piezoresistive sensor also possesses a very fast response time (10 ms), rapid recovery (20 ms), and excellent cycling stability. The real-time pressure detection ability is demonstrated by the touching behavior, the muscle and joint movement and the vocalization recognition, presenting great application potential in human–machine interaction, human motion monitoring and intelligent robotic systems.

Assembly of long silver nanowires into highly aligned structure to achieve uniform “Hot Spots” for Surface-enhanced Raman scattering detection

Silver nanowires (AgNWs) as a promising surface-enhanced Raman spectroscopy (SERS) substrate could be used in the analytical science due to its high sensitivity. However, it is difficult for the randomly-distributed silver nanowires to offer uniform “hot spots” to achieve the SERS signal reproducibility of small molecules detection. Herein, the evaporation-induced aggregation had been used to assemble long silver nanowires into highly aligned structure to achieve uniform “hot spots” for SERS detection. The normal glass slide with well-aligned silver nanowires could act as a high sensitivity and excellent reproducibility SERS substrate to provide a versatile platform for detecting analytes. Rhodamine 6G (R6G) is used to evaluate the sensitivity and reproducibility of these AgNWs SERS substrates. Even the low concentration of the R6G was 10-10 mol/L, the SERS features of R6G could be still observed clearly, and the uniform distribution of enhancement factor (EF) was higher than 0.8 × 104 accounting for about 75 % in the observed mapping area. Moreover, the relative standard deviation (RSD) of SERS intensity at the band of 610 cm−1 was used to estimate the signal reproducibility, and the calculated RSD value of aligned AgNWs substrate was about 3.6%, which was much higher than that of the randomly distributed AgNWs (26.8%) because of the highly aligned structure of silver nanowires with abundant and uniform inherent “hot spots”. In addition, potential SERS detection of other small molecule, e.g. melamine was also demonstrated in the micromolar range.

A Flexible Integrated Bending Strain and Pressure Sensor System for Motion Monitoring.

Flexible sensors have attracted increasing research interest due to their broad application potential in the fields of human–computer interaction, medical care, sports monitoring, etc. Constructing an integrated sensor system with high performance and being capable of discriminating different stimuli remains a challenge. Here, we proposed a flexible integrated sensor system for motion monitoring that can measure bending strain and pressure independently with a low-cost and simple fabrication process. The resistive bending strain sensor in the system is fabricated by sintering polyimide (PI), demonstrating a gauge factor of 9.54 and good mechanical stability, while the resistive pressure sensor is constructed based on a composite structure of silver nanowires (AgNWs) and polydimethylsiloxane (PDMS)-expandable microspheres with a tunable sensitivity and working range. Action recognition is demonstrated by attaching the flexible integrated sensor system on the wrist with independent strain and pressure information recorded from corresponding sensors. It shows a great application potential in motion monitoring and intelligent human–machine interfaces.

Highly Transparent Conducting Electrodes Based on a Grid Structure of Silver Nanowires

Transparent conducting electrodes (TCEs) formed with silver nanowires (AgNWs) have attracted attention as substitutes for indium tin oxide (ITO). However, the randomly deposited AgNW film performs poorly in terms of the transmittance and sheet resistance to serve as a substitute of ITO. To improve the performance of the AgNW film, we fabricated a grid-patterned AgNW by modifying the surface energy of the substrate. The hydrophobized surface was selectively etched by UV light through a quartz chrome mask, and a suspension of AgNWs in isopropyl alcohol/ethylene glycol mixture was coated on the substrate by a meniscus dragging deposition process. The grid-patterned AgNW film has a lower percolation threshold and a 13% higher figure-of-merit value compared to the randomly deposited AgNW film. The transparent thin films with a grid structure of AgNWs exhibit the high electrical conductivity with a sheet resistance of 33 Ohm/sq at a transmittance of 92.7% (λ = 550 nm).

Electrical bistabilities behaviour of all-solution-processed non-volatile memories based on graphene quantum dots embedded in graphene oxide layers

This study demonstrates the feasibility of all-solution-processed mean to fabricate carbon-based non-volatile memory (NVM). The NVM devices were fabricated on polyethylene terephthalate (PET) substrate using spin-coating and spray-coating techniques in the structure of silver nanowires (AgNWs)/graphene oxide (GO)/graphene quantum dots (GQDs)/graphene oxide (GO)/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/PET. PEDOT:PSS was used as the bottom conductive layer and deposited by spin-coating method. GQDs were used as a charge trapping site in the structure and embedded in the two GO insulator layers. The AgNW metal electrode was formed on top of GO/GQDs/GO/PEDOT:PSS by the spray-coating method. The overall smooth surface morphology of the spray-coated films serves as good contact with the top metal electrode. The electrical characterization of the fabricated device shows the bistable current states with the ON/OFF ratio of 105. The NVM device can be programmed and erased multiple times. Various conduction mechanisms were proposed to describe the charge trapping process in GQD based on the obtained current–voltage measurement.

Electronic structure of self-assembled Ag nanowires on Si(557): spectroscopic evidence for dimensionality

We investigate the electronic structure of silver nanowires at 1 monolayer (ML) Ag coverage on a vicinal Si(557) substrate by angle-resolved photoemission spectroscopy. Fermi surface mapping reveals two-dimensional (2D) Ag-induced electron pockets, which shift to higher binding energies by n-type doping of the step edges. The electronic structure of the 1 ML Ag/Si(557) system exhibits additional 2D metallic states near the Fermi level, which may originate from substrate induced periodicities. By considering the confining potential and electronic coherence length we reconcile the seemingly conflicting views of the dimensionality in this system probed by photoemission spectroscopy, and the dispersion of collective excitations as detected by electron energy loss spectroscopy .

Routing of surface plasmons in silver nanowire networks controlled by polarization and coating.

Controllable propagation of electromagnetic energy in plasmonic nanowaveguides is of great importance for building nanophotonic circuits. Here, we studied the routing of surface plasmons in silver nanowire structures by combining experiments and electromagnetic simulations. The superposition of different plasmon modes results in the tunable near field patterns of surface plasmons on the nanowire. Using the quantum dot fluorescence imaging technique, we experimentally demonstrate that the near field distribution on the nanowire controls the surface plasmon transmission in the nanowire networks. By controlling the polarization of the input light or by controlling the dielectric coating on the nanowire to modulate the plasmon field distribution and guarantee the strong local field intensity at the connecting junction, the surface plasmons can be efficiently routed to the connected nanowires. Depositing a thin layer of Al2O3 film onto the nanowires can reverse the polarization dependence of the output intensity at the nanowire terminals. These results are instructive for designing functional plasmonic nanowire networks and metal-nanowire-based nanophotonic devices.

Plasmonic propagation and spectral splitting in nanostructured metal wires

Due to the coupling of photons with the electrons at a metal-dielectric interface, surface plasmons (SPs) can achieve extreflely small wavelengths and highly localized electromagnetic fields. Hence, plasmonics with subwavelength characteristics can break the diffraction limit of light, and thus has aroused great interest for decades. The SP-inspired reflearch, in the application respect, includes extraordinary optical transmission, surface enhanced Raman spectroscopy, sub-wavelength imaging, electromagnetic induced transparency, perfect absorbers, polarization switches, etc.; and in the fundamental respect, includes plasmon-mediated light-matter interaction, such as plasmonic lasing, plasmon-exciton strong coupling, etc.#br#Recently a series of studies has been performed to push the dimensions of plasmonic devices into deep subwavelength by using nanowires. The chemically synthesized metallic nanowires have good plasmonic properties such as low damping. The reported silver nanowire structures show great potential as plasmonic devices for communication and computation. Now we develop the nanostructured metal wires for plasmonic splitters based on the following considerations. One is that we introduce cascade nano-gratings on a metallic nanowire, enabling a single nanowire to act as a spectral splitting device at subwavelength; and the other is that we use silicon as a substrate for the metallic nanowire, making the plasmonic nanowire device compatible with silicon based technologies.#br#In this paper, we continue and develop our previous work on position-sensitive spectral splitting with a plasmonic nanowire on silicon chip (see Scientific Reports (2013) 3 3095). The three parts are organized as follows. In the first part, we derive analytically the dispersion relation of the SPs in a suspended silver nanowire based on Maxwell equations. In the second part, we placed a silver nanowire in the silicon substrate, and use the finite-element method (FEM) to obtain the dispersion relation of the SPs for the practical applications. The calculations show that the SP mode can be confined better in this system, howbeit with larger loss. Starting from the dispersion relation, we then calculate the mode area, the propagation length and the effective index of the SP modes, with respect to the nanowire dimension and the substrate materials. It is shown that a thinner nanowire has smaller mode area and a higher-index substrate induces larger loss. We also perform the finite-difference time-domain (FDTD) simulation to investigate the electromagnetic field distribution in this system. We find that the SP mode is mainly confined around the top surface of the nanowire, and in the crescent gap between the nanowire and the substrate. In the third part, we demonstrate both experimentally and theoretically that the silver nanowire with two cascaded gratings can act as a spectral splitter for sorting/demultiplexing photons at different spacial locations. The geometry of the grating is optimized by rigorous coupled wave analysis (RCWA) calculation. The carefully designed gratings allow the SPs with the frequencies in the plasmonic band and prohibit the SPs with the frequencies in the plasmonics bandgap. Those prohibited SPs areflemitted out through a single groove in front of each grating. Both the detected images and the measured optical spectra demonstrate that the SPs with different colors can be emitted at different grooves along a single nanowire. Thus the structured metal nanowire shows potential applications in position-sensitive spectral splitting and optical signal processing on a nanoscale, and provides a unique approach to integrating nanophotonics with microelectronics.

Template synthesis of palladium nanotubes and their electrocatalytic properties

Palladium nanotubes were prepared by using silver nanowires as the template, which were prepared in a modified polyol reduction process. The morphology and structure of silver nanowires and palladium nanotubes were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrochemical experimental data showed that palladium nanotubes displayed high electrocatalytic activity toward the electrooxidation of alcohols, especially for ethanol. The formation mechanism of palladium nanotubes as well as the relationship between their structure and electrocatalytic activity was discussed based on the experimental results.

Ultrasonication assisted production of silver nanowires with low aspect ratio and their optical properties

We investigated a facial method to produce silver nanowires with low aspect ratio by fragmentizing as produced long silver nanowires. The length of silver nanowires can be shortened in a controllable manner by increasing ultrasonication time or ultrasonication power. However, excessively large ultrasonication power caused a problem of agglomeration of nanowires. From UV absorption spectra, it was found that the UV absorption characteristic of silver nanowires is not affected by ultrasonication assisted fragmentation indicating that one dimensional structure of silver nanowires is maintained during the fragmentation process.

Electrochemical synthesis and functionality evaluation of silver nanostructured layers

The functionality of silver nanostructures prepared by means of electrochemical deposition of silver into the pores of anodic alumina oxide (AAO) template was examined in correlation to electrodeposition conditions. The optical activity as well as the chemical separation ability of prepared nanostructured films was studied. The surface enhanced Raman spectroscopy (SERS) performance was evaluated by the signals of rhodamine 6G, 4‐aminothiophenol and 2,7‐dichlorfluorescein. Nanostructured silver substrates showed moderate surface enhancement for Raman scattering from adsorbed molecules with the magnitude of about 26.9. Moreover, a novel separation/pre‐concentration function of the silver nanowire structures was indicated. The identification and position detection of the model compounds were realised with SERS. The separation of single chemical components from the two‐component mixture over the examined silver nanostructured films was sufficiently approved. The results obtained demonstrated the potential of the prepared substrate as a SERS detection and separation probe for further implementation to any instrumentation. Copyright © 2014 John Wiley &amp; Sons, Ltd.

A facile synthesis of branched silver nanowire structures and its applications in surface-enhanced Raman scattering

We report a facile method of preparing novel branched silver nanowire structures such as Y-shaped, K-shaped and other multi-branched nanowires. These branched nanostructures are synthesized by reducing silver nitrate (AgNO3) in polyethylene glycol (PEG) with polyvinglpyrrolidone (PVP) as capping agent. Statistical data indicate that for the "y" typed branched nanowire, the branches grow out from the side of the trunk nanowire in a preferential orientation with an angle of 55A degrees between the branch and the trunk. Transmission electron microscopy (TEM) studies indicate that the defects on silver nanowires could support the growth of branched nanowires. Conditions such as the molar ratio of PVP/AgNO3, the reaction temperature, and the degree of polymerization of reducing agent and PVP play important roles in determining the yield of the silver branches. Due to the rough surface, these branched nanostructures can be used as efficient substrates for surface-enhanced Raman scattering applications.

Controllable Excitation of Surface Plasmons in End-to-Trunk Coupled Silver Nanowire Structures

In branched nanowire structures, the controllable excitation of surface plasmons is investigated by both experiments and simulations. By focusing the excitation light at the junction between the main wire and the branch wire, surface plasmons can be selectively launched to propagate to different output terminals, depending on the polarization of the excitation light. The parameters influencing the plasmon excitation and thus emission behavior are investigated, including the branch angle, the position of the branch and the nanowire radius. The different polarization dependence of the output light is determined by the surface plasmon modes selectively excited in the junction through end-excitation or/and gap-excitation manners. For the branch wire, when the branch angle is small, the end-excitation is dominant, which makes the branched wire behave like an individual nanowire. With the increase of the branch angle, the coupling between the branch wire end and the primary wire trunk is increased, which influences the plasmon excitation in the branch wire as evidenced by the rotation of the polarization angle for maximum output. For the primary wire, the SP excitation is dependent on the branch angle, position of the junction along the primary wire, and the radii of the nanowires. The results may be important for the design of a controllable surface plasmon launcher, one of the functional components in surface-plasmon-based nanophotonic circuits.

Controlling surface plasmon interference in branched silver nanowire structures

Using quantum dot fluorescence imaging, we investigated the interference of surface plasmon beams in branched silver nanowire structures. Depending on the phases and polarizations of the incident light, interferences of plasmon beams modulate the plasmon propagation in the branched structures and the output light intensity in the distal ends. The interference visibility is strongly dependent on the incident polarization at the main wire terminal, and the mechanism is revealed by quantum dot fluorescence imaging of the near field distribution of propagating plasmons. The near field distribution pattern resulting from the beating of different plasmon modes plays a critical role in the plasmon interference. The overlap of the antinode in the near field pattern with the connection junction in the nanowire structure is required for a large interference visibility, since the overlap makes the electric field intensity difference of the two plasmon beams smaller. It is found that the plasmon interference is strongly dependent on the polarization of the excitation light at the main wire terminal, but weakly dependent on the polarization at the branch wire terminal.