Bimetallic Nanowires Research Articles

Controlled Living Nanowire Growth: Precise Control over the Morphology and Optical Properties of AgAuAg Bimetallic Nanowires.

Inspired by the concept of living polymerization reaction, we are able to produce silver–gold–silver nanowires with a precise control over their total length and plasmonic properties by establishing a constant silver deposition rate on the tips of penta-twinned gold nanorods used as seed cores. Consequently, the length of the wires increases linearly in time. Starting with ∼210 nm × 32 nm gold cores, we produce nanowire lengths up to several microns in a highly controlled manner, with a small self-limited increase in thickness of ∼4 nm, corresponding to aspect ratios above 100, whereas the low polydispersity of the product allows us to detect up to nine distinguishable plasmonic resonances in a single colloidal solution. We analyze the spatial distribution and the nature of the plasmons by electron energy loss spectroscopy and obtain excellent agreement between measurements and electromagnetic simulations, clearly demonstrating that the presence of the gold core plays a marginal role, except for relatively short wires or high-energy modes.

Template-assisted synthesis of Ni–Co bimetallic nanowires for urea electrocatalytic oxidation

Nickel–cobalt bimetallic nanowire electrocatalyts (NCNE), synthesized through anodic aluminium oxide templates, were evaluated for urea electro-oxidation in alkaline medium for their applications in wastewater remediation, hydrogen production, and fuel cells. Compared to bulk nickel film electrocatalysts (NFE), the NCNE resulted in a ca. 110 mV decrease in the overpotential of urea electro-oxidation. In addition, the NCNE exhibited higher oxidation current density and current efficiency for urea electrolysis than those of NFE and nickel–cobalt bimetallic film electrocatalysts (NCFE). The maximum current efficiency for urea electro-oxidation on the NCNE reached up to 81 %, which is ~25 % higher than those of the NFE and NCFE.

Facile synthesis of PtCu nanowires with enhanced electrocatalytic activity

Using Te nanowires as a sacrificial template, we developed a facile wet-chemical method for the synthesis of bimetallic PtCu nanowires. The as-prepared PtCu nanowires possess a porous structure and high aspect ratio. Transmission electron microscopy, X-ray diffraction, energy dispersive spectroscopy, energy dispersive X-ray spectrum elemental mapping, inductively coupled plasmamass spectroscopy, and X-ray photoelectron spectroscopy (XPS) measurement techniques are used to analyze the structure and composition of the as-prepared nanowires. The XPS results verify that the incorporation of Cu led to the modified electronic state of Pt. Electrocatalytic results prove that the as-prepared nanowires present superior activity for methanol and ethanol electrooxidation in an alkaline solution.

Bimetallic Pt3Co nanowires as electrocatalyst: the effects of thermal treatment on electrocatalytic oxidation of Methanol

The influence of thermal treatment effect on the methanol oxidation catalytic activities of Pt3Co alloy nanowires prepared by template-assisted pulsed electrodeposition has been investigated. The catalytic activities of Pt3Co nanowires dose not linearly increase as the annealing temperature rises from 200 to 600°C, in which the best catalytic performance appear at 200°C. Meanwhile, the perpendicular coercivity has a weak increase at a mild thermal treatment from 200 to 400°C and a dramatic increase after annealing at 600°C. These results reveal that the thermal treatment has a strong influence on their catalytic and magnetic properties of electrodeposited Pt3Co alloy nanowires and can be exploited as an effective and facile way to achieve excellent magnetic nanocatalyst.

Preparation and characterization of copper/silver bimetallic nanowires with core-shell structure

Core-shell copper/silver bimetallic nanowires were prepared by replacement reaction with citric acid and polyvinylpyrollidone at room temperature. A uniform silver coating was obtained by strictly controlling the molar ratio of Ag/Cu. The copper/silver composite was characterized by X-ray diffraction, scanning electron microscopy, electron probe microanalysis and X-ray photoelectron spectroscopy. Microscopic analysis shows that a well-copper/silver core-shell structure was formed. Thermo-gravimetry and differential thermal analysis to the composite nanowires show that the silver coatings efficiently inhibit the oxidation of Cu. Copyright © 2015 John Wiley & Sons, Ltd.

Facile synthesis of ultrathin bimetallic PtSn wavy nanowires by nanoparticle attachment as enhanced hydrogenation catalysts.

Ultrathin wavy nanowires represent an emerging class of nanostructures that exhibit unique catalytic, magnetic, and electronic properties, but the controlled production of bimetallic wavy nanowires remains a significant challenge. Ultrathin bimetallic PtSn nanowires have been prepared with high yield and featuring a highly wavy structure. Owing to the ultrathin nature and unique electronic properties of these PtSn wavy nanowires, they exhibit improved catalytic performance for the hydrogenation of nitrobenzene, as well as for the hydrogenation of styrene. These results suggest a new strategy to prepare highly active catalysts through defect engineering and can significantly impact broad practical applications.

Bimetallic PdPt nanowire networks with enhanced electrocatalytic activity for ethylene glycol and glycerol oxidation

A facile avenue to synthesize bimetallic PdPt nanowire networks with tunable composition and enhanced electrocatalytic performance is demonstrated.

Design of Infrared SPR Sensor Based on Bimetallic Nanowire Gratings on Plastic Optical Fiber Surface

In this paper, a bilayer metallic grating with pitch of 1 μm on the flank of a cylindrical plastic optical fiber was proposed as a novel optical sensor. Surface plasmon resonance excited by this structure for refractive index sensing is investigated by finite difference time domain methods. A theoretical sensitivity of 643.75 nm/RIU is obtained, where the wavelength of the resonant sharp dip is obviously shifted from 1.398 μm to 1.501 μm for surrounding refractive index increased from 1.33 to 1.49. Several factors which affect the accuracy of the device, such as the polarization state of the incident light, grating pitch, and refractive index of the sensing medium, are discussed. The successful fabrication of the grating indicates the feasibility of the devices. The sensor is expected to have potential applications in the chemical, biomedical, environmental safety, and food safety industries as well as in many other aspects.

PtAg bimetallic nanowires: Facile synthesis and their use as excellent electrocatalysts toward low-cost fuel cells

Facile chemical synthesis of PtAg nanowires with different compositions through co-reduction of Ag and Pt precursors has been demonstrated. A facet-matching coupled autocatalytic growth mechanism, which favors reducing the exposed surface area while minimizing the interface mismatch energy with the formation of a coherent interface, is supported by SEM, TEM, XRD and EDS characterizations. Interestingly, tunable electrocatalytic activities have also been shown, which can be up to three times higher toward the direct methanol oxidation reaction in acid media for the dealloyed Pt94Ag6 than that of the commercial Pt/C catalyst based on the same mass of Pt. Such an excellent catalytic performance can be ascribed to the synergy effect of enhanced electric conductivity, clean surface, significantly increased caves, as well as the hetero-atomic interactions on the surface of alloyed nanoparticles.

Detection of H2O2 at the nanomolar level by electrode modified with ultrathin AuCu nanowires.

Bimetallic AuCu nanowires (AuCuNWs) are synthesized via a facile water solution method at room temperature. Enhanced electrocatalytic activity is observed toward the oxidation of H2O2, which makes the AuCu nanowire, along with its unique catalytic properties, intriguing bifunctional mechanism, and surface atomic construction, a promising platform for the amplification of interfacing signal. A highly sensitive H2O2 biosensor is thus developed on the base of the as-prepared AuCuNW catalyst. A very low real determination limit (2.0 nM) was reached, and a linear range as wide as 5 orders of magnitude was demonstrated. In addition, a trace amount of H2O2, which was released from Raw 264.7 cells, was selectively detected, hinting at the possible applications for real-time quantitative detection of H2O2 in a biological environment.

Formation of bimetallic core-shell nanowires along vortices in superfluid He nanodroplets

We report on the formation of one-dimensional Au/Ag core-shell nanostructures in superfluid helium nanodroplets $({\mathrm{He}}_{N})$ and their subsequent surface deposition under soft landing conditions. In vortex charged ${\mathrm{He}}_{N}$, dopant atoms and clusters prefer to agglomerate along vortex cores, which serve as personal cryo-templates for each nanowire. A sequential pickup scheme enables the fabrication of Au/Ag structures with either Au as core and Ag as shell or vice versa. The core-shell structure is in both cases shown by energy-dispersive x-ray spectroscopy (EDX) in a scanning transmission electron microscope (STEM). The inherent spatial resolution and element sensitivity of this method allows a direct observation of the two different phases. High resolution STEM studies elucidate morphological details of the Au/Ag nanostructures and, together with the EDX analysis, indicate that the nanowires are formed in a multicenter aggregation process.

Emergence of spin-filter states in Pt–Fe nanowires

Our theoretical study predicts the emergence of a new spin-filter state in one-dimensional Pt-Fe bimetallic nanowires. The results show the existence of two transmission states in contracted "zig-zag" Pt-Fe nanowires with low and high transmission 1G0 and 3G0, correspondingly, and one transmission state in linear stretched nanowires with conductance 2G0. Our first principle calculations revealed the dependence of quantum conductance of Pt-Fe nanowires on their geometry and atomic structure. Thus we found that nanowire stretching up to the interatomic distance of 2.3 Å leads to the transition of the wire from a "zig-zag" to the linear configuration, leading to changes in the conductance properties of the wire, i.e. formation of a new spin-filter state. Our study shows also the emergence of a magnetic transition from ferromagnetic to antiferromagnetic states under wire stretching. We found that the spin-filter state exists only in "zig-zag" Pt-Fe nanowires in the ferromagnetic state. Moreover, the spin-polarization of quantum electron transport through Pt-Fe nanowires vanishes totally in linear stretched nanowires in an antiferromagnetic state. Our electronic structure calculation reveals the emergence of new hybridized states in the band structure of the Pt-Fe nanowire, which causes the formation of a new spin-filter state.

One-step synthesis and shape-control of CuPd nanowire networks

An effective one-step method has been developed to synthesize CuPd bimetallic nanowire networks. Investigation of the growth process revealed that the nanowires were formed by attachment of spherical particles and strongly influenced by interactions between surface ligands and metals. The morphology of CuPd nanoparticles is tuned via changing the molecular weight of polyvinylpyrrolidone (PVP) and solvents. The versatility of this method was further demonstrated by preparation of AgPd nanowires. An electrochemical study of CuPd nanowire networks shows morphology dependent activity in oxygen reduction reaction (ORR), which is comparable to that of platinum.

Cascade-pumped random lasers with coherent emission formed by Ag–Au porous nanowires

A series of sequentially cascade-pumped random lasers is reported. It consists of three random lasers in which the Ag-Au bimetallic porous nanowires play the role of scatterers, and the gain materials are coumarin 440 (C440), coumarin 153 (C153), and rhodamine 6G (R6G), respectively. The random laser with C440 is first pumped by a 355 nm pulsed laser. The emission of C440 pumps the C153, and the emission of C153 pumps the R6G sequentially. Low-threshold coherent emissions from the three random lasers are observed. The cascade-pumped random lasers can be achieved easily with low cost and can be used in applications conveniently.

Random Lasing with a High Quality Factor over the Whole Visible Range Based on Cascade Energy Transfer

On the basis of cascade energy transfer between different dye molecules, single‐excitation and low threshold coherent random lasing with a high quality factor (∼13 000) over the whole visible range is experimentally observed using gold–silver bimetallic porous nanowires with abundant nanogaps as the scatterers. These nanogaps with different sizes in the bimetallic nanowires can produce continuous plasmonic resonance spectra and provide strong feedback or gain channels for the stimulated emission from different dye molecules. It guarantees a low threshold of lasing. Moreover, multi gain media can provide broad tunability of the emission wavelength when the system is pumped by single‐wavelength pulses. It provides excellent flexibility for the design of multicolor output devices.

High performance porous nickel cobalt oxide nanowires for asymmetric supercapacitor

In this work, we present the formation of porous NiCo oxide nanowires from single crystal nickel cobalt bimetallic carbonate hydroxide nanowires (NiCo cNW) for supercapacitor applications. High aspect ratio NiCo cNWs are found to evolve from highly crystalline nickel cobalt layered double hydroxides through a dodecyl anion assisted crystallization–dissolution–recrystallization process. The porous nickel cobalt oxide (NixCo3−xO4) nanowire array is formed by the heat treatment of nickel cobalt bimetallic carbonate hydroxide nanowires on nickel foam (NF) for the assembly of supercapacitors. This binder free electrode shows a high specific capacitance of 1479Fg−1 at 1Ag−1 and 792Fg−1 at 30Ag−1, indicating an excellent rate capability. Asymmetric device is constructed from NixCo3−xO4 on NF and activated carbon (AC) with an operation potential from 0 to 1.6V. It shows a high specific capacitance of 105Fg−1 at a current density of 3.6mAcm−2, while it maintains 58.7Fg−1 at 89.4mAcm−2. In addition, the asymmetric device shows good stability towards long time charge–discharge cycles.

Bimetallic alloy nanowires and nanosponges: A comparative study of peroxidase mimetics and as enhanced catalysts for oxygen reduction reaction

A comparative study on bimetallic alloy nanomaterials, with different dimensions (i.e., 1D nanowires and 3D nanosponges), of peroxidase mimetics and as enhanced catalysts for oxygen reduction reaction was performed. The synthesized PdPt nanosponges possessed much better oxidase and peroxidase mimetics than those of PdPt nanowires. In addition, nanosponges exhibited more advantageous onset potential and higher ORR specific activity, while nanowires presented higher limiting current density.

High performance plasmonic random laser based on nanogaps in bimetallic porous nanowires

A plasmonic random laser is fabricated using gold-silver bimetallic porous nanowires with abundant nanogaps that provide strong feedback or gain channels for coherent lasing from dye molecules. The strong confinement of the nanogaps allows the bimetallic porous nanowire-based random laser, which is pumped by ns pulses, to operate with a very low threshold and extremely low concentrations of Rhodamine 6 G (as low as 0.067 mM). This random laser can be used as a pump source for another coherent random laser based on oxazine. These results provide a basis for studies of coherent random lasing pumped by another random laser.

Bimetallic Ag–Au Nanowires: Synthesis, Growth Mechanism, and Catalytic Properties

Silver-gold (Ag-Au) bimetallic nanowires were controllably synthesized by a newly developed wet-chemical method at room temperature. The Ag nanowires and Au nanoparticles were sequentially formed by reduction with vanadium oxide (V2O3) nanoparticles so as to form Ag-Au bimetal, in which the Ag nanowires show a diameter of ~20 nm and length up to 10 μm. A few unique features were noted in our new approach: it was rapid (within a few minutes), controllable in shape and size, reproducible, and there was no need for any surface modifiers. The formation and growth mechanisms of these Ag-Au bimetallic nanostructures driven by lattice match and a unique reducing agent (V2O3) have been proposed in this study. Moreover, the application of such bimetallic nanoparticles for catalytic reduction of 4-nitrophenol to 4-aminophenol was performed, and they exhibit catalytic properties superior to those of the Ag nanowires, Au nanoparticles, and Ag-Pd bimetallic nanostructures prepared under the reported conditions. These Ag-Au bimetallic nanoparticles have potential to be highly efficient catalysts for the reduction of 4-nitrophenol. This study may lead to new path for the generation of other bimetallic nanostructures with excellent catalytic efficiency.

First-Principles Study of the Structural, Electronic, and Magnetic Properties of Cu-Fe, Cu-Co, and Cu-Ni Linear and Zigzag Nanowires

By using first-principles calculations, we have systematically investigated the equilibrium structure, electronic, and magnetic properties of free-standing Cu-Fe, Cu-Co, and Cu-Ni bimetallic linear and zigzag nanowires, and a comparison was carried out with the corresponding monatomic chains. It was found that all the bimetallic linear and zigzag chains have stable ferromagnetic (FM) states, and the total energies of all the considered zigzag chains are lower than those of the corresponding linear chains. The equilibrium bond lengths of the bimetallic Cu-Fe, Cu-Co, and Cu-Ni nanowires lie in between the values of the corresponding monatomic systems. The magnetic moments in linear nanowires are generally larger than the ones of the corresponding zigzag nanowires, and the Fe, Co, and Ni atoms in bimetallic nanowires have quite high local magnetic moments. The calculations suggest that there is hybridization between the Cu-3d and Fe (Co or Ni) 3d states, which leads to lower cohesive energies of the bimetallic nanowires than those of the corresponding monatomic nanowires. The bimetallic Cu-Fe and Cu-Co nanowires also have high spin polarizations and may be good potential materials for spintronic devices.