Nickel Nanowires Research Articles

Asymmetric dual Bloch point domain walls in cylindrical magnetic nanowires

Cylindrical magnetic nanowires have been studied extensively over the past ten years due to the presence of domain walls with novel topology and outstanding dynamic properties. In soft magnetic systems, where shape anisotropy forces the magnetization along the wire axis, and for radii above 50 nm, two topologically distinct walls have been previously identified. The Bloch point wall (BPW) has a circulating magnetization texture around the circumference and contains a single Bloch point within the center of the wire cross section. In contrast, asymmetric transverse walls (ATWs) have a circulating magnetization structure on the surface and contain two topological defects, a vortex and an anti-vortex on opposing sides. These surface defects are connected via a vortex tube that penetrates the volume. In this study, we have numerically investigated the domain wall magnetization textures for nickel nanowires of radii 50–120 nm. Beyond reproducing the known BPW and ATW topology, we discover a new domain wall type that contains aspects of both. This new domain wall type, which we call asymmetric dual Bloch point wall (ADBPW), has surface vortices similar to an ATW and two Bloch-point textures adjacent to the internal vortex tube. Time-resolved simulations investigating the stability of ADBPW show its field-driven transformation into a BPW via the ejection of a single Bloch point at the surface and subsequent annihilation of surface vortices.

Long-range superconducting proximity effect in nickel nanowires

When a ferromagnet is placed in contact with a superconductor, owing to incompatible spin order, the Cooper pairs from the superconductor cannot survive more than one or two nanometers inside the ferromagnet. This is confirmed in the measurements of ferromagnetic nickel (Ni) nanowires contacted by superconducting niobium (Nb) leads. However, when a 3 nm thick copper oxide (CuO) buffer layer made by exposing an evaporated or a sputtered 3 nm Cu film to air, is inserted between the Nb electrodes and the Ni wire, the spatial extent of the superconducting proximity range is dramatically increased from 2 to a few tens of nanometers. Scanning transmission electron microscope study confirms the formation of a 3 nm thick CuO layer when an evaporated Cu film is exposed to air. Magnetization measurements of such a 3 nm CuO film on a SiO2/Si substrate and on Nb/SiO2/Si show clear evidence of ferromagnetism. One way to understand the long-range proximity effect in the Ni nanowire is that the CuO buffer layer with ferromagnetism facilitates the conversion of singlet superconductivity in Nb into triplet supercurrent along the Ni nanowires.

Influence of Size, Shape, and Scattering on Electrical Resistivity of Metal Nanowires

A simple quantitative model has been proposed for exploring the combined effect of size, shape, and electron scattering on the electrical resistivity of metallic nanowires. In the present model, the effect of different cross-sectional shapes of nanowires has been comprised on the surface and grain boundary scattering. For understanding electrical behavior at the nanolevel, the incorporation of specularity parameter (p) with different cross-sectional shapes of nanowires is essential. It is responsible for the reduction in the mean free path of electrons; which generates the favorable condition for enhancing the surface scattering, consequently contributing to increment of electrical resistivity. The applicability of the proposed model has been investigated for copper, nickel, silver, and aluminum metallic nanowires of four different cross-sectional shapes (rectangular, triangular, square, and spherical) along with different values of reflection coefficient (R). Calculated results have been compared with the available experimental data and it is observed that the results are in close agreement, which proves the validity of the proposed model. The proposed model shows the collective effect of size, scattering, and crosssectional shape factor (δ) on electrical resistivity in a very simple and straightforward manner and able to reduce the complexity of existing models up to great extent.

Macro- and atomic-scale observations of a one-dimensional heterojunction in a nickel and palladium nanowire complex

The creation of low-dimensional heterostructures for intelligent devices is a challenging research topic; however, macro- and atomic-scale connections in one-dimensional (1D) electronic systems have not been achieved yet. Herein, we synthesize a heterostructure comprising a 1D Mott insulator [Ni(chxn)2Br]Br2 (1; chxn = 1R-2R-diaminocyclohexane) and a 1D Peierls or charge-density-wave insulator [Pd(chxn)2Br]Br2 (2) using stepwise electrochemical growth. It can be considered as the first example of electrochemical liquid-phase epitaxy applied to molecular-based heterostructures with a macroscopic scale. Moreover, atomic-resolution scanning tunneling microscopy images reveal a modulation of the electronic state in the heterojunction region with a length of five metal atoms (~ 2.5 nm), that is a direct evidence for the atomic-scale connection of 1 and 2. This is the first time that the heterojunction in the 1D chains has been shown and examined experimentally at macro- and atomic-scale. This study thus serves as proof of concept for heterojunctions in 1D electronic systems.

Boosting hydrogen production with ultralow working voltage by selenium vacancy‐enhanced ultrafine platinum–nickel nanowires

AbstractDefect engineering provides a highly potential way to yield exceptional catalytic performance. Herein, we first report the selenium (Se) vacancies‐decorated ultrafine platinum–nickel (PtNi‐Sev) nanowires, as a bifunctional catalyst for the hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR). The optimized PtNi‐Sev exhibits obvious enhancement for HER and MOR compared to PtNi nanowires. It displays merely an overpotential of 18.8 mV for alkaline HER and the outstanding MOR performance (3.51 A/mgPt). When applying in one symmetric overall water splitting electrolyzer coupling with HER and MOR, an ultralow working voltage of 0.637 V with 100% Faraday efficiency for hydrogen production was achieved at the current density of 10 mA/cm2. Further investigations reveal that the weakened hydrogen binding energy, strong OH binding as well as relative weak CO binding are responsible for the improved HER and MOR activities.

Tailor-designed nanowire-structured iron and nickel oxides on platinum catalyst for formic acid electro-oxidation.

This investigation is concerned with designing efficient catalysts for direct formic acid fuel cells. A ternary catalyst containing iron (nano-FeOx) and nickel (nano-NiOx) nanowire oxides assembled sequentially onto a bare platinum (bare-Pt) substrate was recommended for the formic acid electro-oxidation reaction (FAOR). While nano-NiOx appeared as fibrillar nanowire bundles (ca. 82 nm and 4.2 μm average diameter and length, respectively), nano-FeOx was deposited as intersecting nanowires (ca. 74 nm and 400 nm average diameter and length, respectively). The electrocatalytic activity of the catalyst toward the FAOR depended on its composition and loading sequence. The FeOx/NiOx/Pt catalyst exhibited ca. 4.8 and 1.6 times increases in the catalytic activity and tolerance against CO poisoning, respectively, during the FAOR, relative to the bare-Pt catalyst. Interestingly, with a simple activation of the FeOx/NiOx/Pt catalyst at −0.5 V vs. Ag/AgCl/KCl (sat.) in 0.2 mol L−1 NaOH, a favorable Fe2+/Fe3+ transformation succeeded in mitigating the permanent CO poisoning of the Pt-based catalysts. Interestingly, this activated a-FeOx/NiOx/Pt catalyst had an activity 7 times higher than that of bare-Pt with an ca. −122 mV shift in the onset potential of the FAOR. The presence of nano-FeOx and nano-NiOx enriched the catalyst surface with extra oxygen moieties that counteracted the CO poisoning of the Pt substrate and electronically facilitated the kinetics of the FAOR, as revealed from CO stripping and impedance spectra.

Tailor-Made Iron and Nickel Nanowire Oxides at Platinum Catalyst for Formic Acid Electro-Oxidation

Tailor-Made Iron and Nickel Nanowire Oxides at Platinum Catalyst for Formic Acid Electro-Oxidation

Synthesis of Nickel Nanowires as High Ferromagnetic Material by Electrodeposition Technique

Synthesis of Nickel Nanowires as High Ferromagnetic Material by Electrodeposition Technique

INFLUENCE OF BEAM ENERGY OF IONS ON PROPERTIES OF NICKEL NANOWIRES

Electrical conductivity and optical transmittance of nickel nanowire (Ni-NW) networks are reported in this work. The Ni-NWs were irradiated with 3.5, 3.8 and 4.11[Formula: see text]MeV proton (H[Formula: see text]) ions at room temperature. The electrical conductivity of Ni-NW networks was observed to increase with the increase in beam energies of H[Formula: see text] ions. With the increase in ions beam energies, electrical conductivity increases and this may be attributed to a reduction in the wire–wire point contact resistance due to the irradiation-induced welding of NWs. Welding is probably initiated due to H[Formula: see text] ion-irradiation induced heating effect that also improved the crystalline quality of the NWs. After ion beam irradiation, localized heat is generated in the NWs due to ionization which was also verified by SRIM simulation. Optical transmittance is increased with increase in the energy of H[Formula: see text] ions. The Ni-NW networks subjected to an ion beam irradiation to observe corresponding changes in electrical conductivity and optical transparencies are promising for various nanotechnological applications, such as highly transparent and conducting electrodes.

Metal oxide nanotubes via electrodeposition for battery-electrochemical capacitor hybrid device

Charge accessibility in nanotube electrodes and consequent electrochemical properties exploitable for energy storage and sensing device is higher due to their dual surfaces than solid nanowires; however, their controlled growth is often challenging. This article demonstrates synthesis of metal nanowires of cobalt and nickel using a template-assisted electrodeposition technique and its transformation into cobalt oxide (Co3O4) and nickel oxide (NiO) nanotubes by controlled annealing. The materials are characterized for their phase, surface, and morphology. The Co3O4 nanotubes has a spinal-type crystal structure, an inner diameter of ~100 nm and wall thickness of ~220 nm with uniform micropores centered at ~21 nm, whereas NiO has a face centered cubic crystal structure, inner diameter ~90 nm and wall thickness ~330 nm with uniform micropores centered at ~21 nm. The electrochemical charge storability of the nanotubes is evaluated in an aqueous alkaline electrolyte (6 M KOH) using a three-electrode system measurement. The Co3O4 and the NiO nanotubes delivered discharge specific charges of ~324 and ~263 C g−1, respectively, the difference charge storability is attributed to the surface and electrochemical properties. Further, a battery – electrochemical capacitor hybrid device is developed with desirable charge storage performance indicators using the Co3O4 nanotubes and reduced graphene oxide as positive electrode and negative electrode, respectively. This research thereby provides a method for developing scalable, reproducible, and efficient battery-electrochemical capacitor hybrid device using NiO and Co3O4 nanotubes.

Evaluation of superhydrophobicity of chemical-resistant magnetic spiky nickel nanowires grafted with silane coupling agent for highly efficient oil/water separation

In the present study, superhydrophobic magnetic spiky nickel nanowires were fabricated using a one-pot hydrothermal process and grafted with octadecyltrichlorosilane (ODTS) coupling agent. In a systematic investigation, the effects of ODTS concentration, sonication time, and modifying solution volume on the surface wettability of the samples have been investigated. XRD, FTIR, FESEM, EDS, XPS, and VSM analyses were conducted to confirm the self-assembled monolayer deposition of silane coupling agent and evaluating the morphological and chemical features of the produced sample before and after surface modification. Superhydrophobicity analysis of the magnetic spiky nickel nanowires grafted with ODTS coupling agent indicated that the water contact angle (WCA) and the contact angle hysteresis (CAH) values were 167.34 ± 1.23° and 1.29 ± 0.9°, respectively achieved under the best-operating conditions including ODTS concentration of 12.5 mM, reaction time of 60 min, and ODTS/toluene solution volume of 10 mL. The prepared spiky nickel nanowires were soaked in various pH value adjusted media ranging from 2 to 12 for 24, 48, 72, 96, and 120 h. Results indicated excellent chemical stability of the wetting properties (WCA>150° and CAH<10°). Also, gravity-driven dichloromethane and chloroform/water mixture separation were conducted using superhydrophobic layered-spiky nickel nanowires, which showed efficient fluxes of 5203.43±22 and 4327.25±41 L m−2 h−1, respectively. The modified sample also showed good reusability after twenty oil/water separation cycles, highlighting the prepared nanospiky materials for industrial applications.

Tensile and creep behavior of nickel nanowires containing volume defects: Insight into the deformation mechanisms and microstructural evolution using molecular dynamics simulations

In this paper, we report the tensile and creep behavior of nickel nanowire (NW) containing volume defects (voids) using molecular dynamics (MD) simulations. The role of void (diameter = 30 Å) on the tensile deformation behavior and mechanisms is investigated at varying strain rates (108 s−1 – 1010 s−1) and temperatures (300 K–1200 K). Similarly, the creep properties are investigated at constant stresses in the range of 2 GPa–5 GPa, and temperatures in the range of 1000 K–1200 K. Embedded atom method (EAM) potential is used to model the interactions between nickel atoms. The NW model size used is 100 Å (x-axis) × 1000 Å (y-axis) × 100 Å (z-axis) and comprises of ∼920,000 atoms. Tensile results show that the load-bearing capacity, elastic modulus of the NWs have decreased with an increase in the number of voids. The microstructural investigations show that void acts as a source of dislocations and cause plastic strain in the NW. However, at higher temperatures, free surface edges act as the source of dislocations. Creep test results show that the strain rates in the steady-state region increase with the applied stress and temperature. The deformation mechanism is by diffusional creep in the steady-state region, and the stress exponent ‘n’ varies from 0.8 to 2.77. Microstructural investigations show the formation of stacking faults and twins. Based on the activation energy for creep, we observe that multi-void NW is less creep resistant than single void nickel NW.

An industry-applicable hybrid electrode for large current density hydrogen evolution reaction

The performance evaluation on water splitting electrodes is usually conducted in laboratory at current density range of 10–100 mA cm−2, and this is far from satisfactory for the industrial practices that require the operating current density larger than 400 mA cm−2. In this work, an efficient hybrid electrode is developed by firstly electro-etching the nickel mesh (E-NM) in actual seawater and then in-situ depositing nickel nanowires (NWs) onto E-NM substrate under the externally applied magnetic field. The results show that NWs are integrated into the defective E-NM structure. The assembled NWs/E-NM hybrid electrode achieves a high current density of 800 mA cm−2 at 2.0–2.1 V, which outperforms the commercial NM electrode. Moreover, the current density does not decay after 100 h stability test at 500 mA cm−2.

Point Agglomeration of Nickel and Iron Nanowires Synthesized in the Pores of Track Membranes

Point Agglomeration of Nickel and Iron Nanowires Synthesized in the Pores of Track Membranes

PdNi/Ni Nanotubes Assembled by Mesoporous Nanoparticles for Efficient Alkaline Ethanol Oxidation Reaction.

The optimization of structure and composition is essential to improve the performance of catalysts. Herein, mesoporous nanoparticles assembled PdNi/Ni nanotubes (mPdNi/Ni NTs) are successfully fabricated using nickel nanowires as sacrificial template. The combination of nanotubular structure with mesoporous nanoparticle morphology can provide facilitated transfer channels and sufficient active sites, allowing the full contact and reaction between catalysts and reactants. Therefore, the synthesized mPdNi/Ni NTs exhibite superior ethanol oxidation performance to mesoporous Pd nanotubes and commercial Pd black. This study proposes a rational strategy for the development of nanoparticle assembled nanotubes with surface mesoporous morphology, which can greatly improve catalytic performance in various electrocatalytic fields.

A lab-on-a-disc platform based on nickel nanowire net and smartphone imaging for rapid and automatic detection of foodborne bacteria

Foodborne pathogenic bacteria have been considered as a major risk factor for food safety. It is of great significance to carry out in-field screening of pathogenic bacteria to prevent the outbreaks of foodborne diseases. In this study, a portable lab-on-a-disc platform with a microfluidic disc was developed for rapid and automatic detection of Salmonella typhimurium using a nickel nanowire (NiNW) net for effective separation of target bacteria, horseradish peroxidase nanoflowers (HRP NFs) for efficient amplification of biological signals, and a self-developed smartphone APP for accurate analysis of colorimetric images. First, the microfluidic disc was preloaded with reagents and samples and centrifuged to form one bacterial sample column, one immune NiNW column, one HRP NF column, two washing buffer columns and one tetramethylbenzidine (TMB) column, which were separated by air gaps. Then, a rotatable magnetic field was specifically developed to assemble the NiNWs into a net, which was automatically controlled by a stepped motor to successively pass through the sample column for specific capture of target bacteria, the HRP NF column for specific label of target bacteria, the washing columns for effective removal of sample background and non-specific binding NFs, and the TMB column for colorimetric determination of target bacteria. The color change of TMB from colorless to blue was finally analyzed using the smartphone APP to quantitatively determine the target bacteria. This lab-on-a-disc platform could detect Salmonella typhimurium from 5.6 × 101 CFU/20 µL to 5.6 × 105 CFU/20 µL in 1 h with a lower detection limit of 56 CFU/20 µL. The recovery of target bacteria in spiked chicken samples ranged from 97.5% to 101.8%. This portable platform integrating separation, labeling, washing, catalysis and detection onto a single disc is featured with automatic operation, fast reaction, and small size and has shown its potential for in-field detection of foodborne pathogens.

Neuromorphic computation with a single magnetic domain wall

Machine learning techniques are commonly used to model complex relationships but implementations on digital hardware are relatively inefficient due to poor matching between conventional computer architectures and the structures of the algorithms they are required to simulate. Neuromorphic devices, and in particular reservoir computing architectures, utilize the inherent properties of physical systems to implement machine learning algorithms and so have the potential to be much more efficient. In this work, we demonstrate that the dynamics of individual domain walls in magnetic nanowires are suitable for implementing the reservoir computing paradigm in hardware. We modelled the dynamics of a domain wall placed between two anti-notches in a nickel nanowire using both a 1D collective coordinates model and micromagnetic simulations. When driven by an oscillating magnetic field, the domain exhibits non-linear dynamics within the potential well created by the anti-notches that are analogous to those of the Duffing oscillator. We exploit the domain wall dynamics for reservoir computing by modulating the amplitude of the applied magnetic field to inject time-multiplexed input signals into the reservoir, and show how this allows us to perform machine learning tasks including: the classification of (1) sine and square waves; (2) spoken digits; and (3) non-temporal 2D toy data and hand written digits. Our work lays the foundation for the creation of nanoscale neuromorphic devices in which individual magnetic domain walls are used to perform complex data analysis tasks.

Highly-sensitive NO2 gas sensors based on three-dimensional nanotube graphene and ZnO nanospheres nanocomposite at room temperature

NO2 sensing devices derived from three-dimensional (3D) nanotube graphene (NTG) and ZnO nanosphere nanocomposite are proposed for room temperature (RT) operation. The nickel nanowires were grown chemically, then graphene was grown onto the obtained nickel nanowires via chemical vapor deposition (CVD). The 3D NTG was then prepared through etching the nickel nanowires, while synthesis of the NTG/ZnO composite was achieved via the hydrothermal method. The sensing performance of these NTG and NTG/ZnO gas sensors to NO2 was systematically investigated. The NTG gas sensor responded with a 22.5% change upon being exposed to 50 ppm of NO2, while the response of the NTG/ZnO device reached 47.8% when exposed to the same NO2 concentration. Furthermore, these devices were also capable of detecting concentrations of NO2 as low as 100 ppb. In addition, NTG and NTG/ZnO gas sensors were found to have good selectivity and repeatability. According to the analysis of the sensing mechanism for the NTG/ZnO composite, the high response of the sensing device is attributed to the heterostructure between NTG and ZnO. When the device is exposed to air and NO2, the barrier changes significantly, thus causing a change of resistance.

Electrodeposition of palladium-dotted nickel nanowire networks as a robust self-supported methanol electrooxidation catalyst

Mass activity and long-term stability are two major issues in current fuel cell catalyst designs. While supported catalysts normally suffer from poor long-term stability but show high mass activity, unsupported catalysts tend to perform better in the first point while showing deficits in the latter one. In this study, a facile synthesis route towards self-supported metallic electrocatalyst nanoarchitectures with both aspects in mind is outlined. This procedure consists of a palladium seeding step of ion track-etched polymer templates followed by a nickel electrodeposition and template dissolution. With this strategy, free-standing nickel nanowire networks which contain palladium nanoparticles only in their outer surface are obtained. These networks are tested in anodic half-cell measurements for demonstrating their capability of oxidising methanol in alkaline electrolytes. The results from the electrochemical experiments show that this new catalyst is more tolerant towards high methanol concentrations (up to {5},hbox{mol},hbox{L}^{-1}) than a commercial carbon supported palladium nanoparticle catalyst and provides a much better long-term stability during potential cycling.Graphical

Gold–Nickel Nanowires as Nanomotors for Cancer Marker Biodetection and Chemotherapeutic Drug Delivery

Future biomedical applications of nanomachines require elimination of fuel requirements since most of the fuels have potential toxic effects. Herein, we report fuel-free magnetically powered gold–n...