Spiral Nanowires Research Articles

Topotactic fabrication of transition metal dichalcogenide superconducting nanocircuits

Superconducting nanocircuits, which are usually fabricated from superconductor films, are the core of superconducting electronic devices. While emerging transition-metal dichalcogenide superconductors (TMDSCs) with exotic properties show promise for exploiting new superconducting mechanisms and applications, their environmental instability leads to a substantial challenge for the nondestructive preparation of TMDSC nanocircuits. Here, we report a universal strategy to fabricate TMDSC nanopatterns via a topotactic conversion method using prepatterned metals as precursors. Typically, robust NbSe2 meandering nanowires can be controllably manufactured on a wafer scale, by which a superconducting nanowire circuit is principally demonstrated toward potential single photon detection. Moreover, versatile superconducting nanocircuits, e.g., periodical circle/triangle hole arrays and spiral nanowires, can be prepared with selected TMD materials (NbS2, TiSe2, or MoTe2). This work provides a generic approach for fabricating nondestructive TMDSC nanocircuits with precise control, which paves the way for the application of TMDSCs in future electronics.

Emerging Nonplanar van der Waals Nanoarchitectures from 2D Allotropes for Optoelectronics

AbstractThe unique atomic thickness and mechanical flexibility of 2D van der Waals (vdW) materials endow them with spatial designability and constructability. It is easy to break the inherent planar construction through various spatial manipulations, thus creating vdW nanoarchitectures with nonplanar topologies. The basic properties before evolution are retained and tunable by architecture‐related feature sizes, and other newly generated properties are inspiring as they are beyond the reach of 2D allotropes, bringing great competitiveness for their encouraging applications in optoelectronics. Here, these representative nonplanar vdW nanoarchitectures (i.e., nanoscrolls, nanotubes, spiral nanopyramids, spiral nanowires, nanoshells, etc.) are summarized and their structural evolution processes are elucidated. Their fascinating nascent properties based on their distinctive structural features, focusing on generally enhanced light–matter interactions and device physics, are further introduced. Finally, their opportunities and challenges for in‐depth experimental exploration are prospected. It is a brand‐new idea to modify the properties of 2D vdW materials from micro‐ and nanostructural design and evolution, offering a solid platform for twistronics, valleytronics, and integrated nanophotonics.

Structure-intensified PtCoRh spiral nanowires as highly active and durable electrocatalysts for methanol oxidation.

Platinum (Pt)-based nanocatalysts with a high density of surface atomic steps hold great prospects in electrocatalysis. However, the structural instability under harsh redox conditions is still a rigorous challenge. Here, we demonstrate that ternary PtCoRh alloyed spiral nanowires (SNWs), which have the advantages of one-dimensional nanowires, alloy synergy, surface atomic steps, and anti-corrosive Rh incorporation, can serve as active and robust MOR electrocatalysts in acidic media. The results showed that the Pt77Co11Rh12 SNWs delivered the highest mass activity (1.48 A mg-1) and specific activity (4.76 mA cm-2), as well as the best durability in the long-term MOR test, compared with the Pt85Co10Rh5 and Pt85Co15 SNWs and Pt black. Further inspections of the morphology, composition, and electronic structure revealed that the incorporated Rh atoms not only stabilized the highly rugged SNWs and the easily leaching Co atoms but also delicately tuned the electron transfer among the three metallic elements, leading to the enhancement of MOR activity, structural stability and anti-CO-poisoning ability. Our work provides a rational strategy for the development of highly efficient and durable alcohol oxidation electrocatalysts.

Superior microwave absorbing properties of O, S, N codoped carbon planar helixes via carbonization of polypyrrole spiral nanowires

Lightweight, and broad and strong absorption are still a huge challenge for electromagnetic (EM) wave absorbers. Here, we propose a facile oxidative polymerization-carbonization strategy to synthesize O, S, N codoped carbon planar helixes for superior EM wave absorbers. The spiral cetyltrimethylammounium bromide crystallites act as a template for the in-situ oxidative polymerization of pyrroles into ordered PPy spiral nanowires. Sintering temperature (Ts) was used to adjust the defects, heteroatoms, graphitization degree, and properties of the carbonized products. With Ts varying from 400 °C to 800 °C, internal stress and heteroatom (N, O, S) content decreased, causing the decreased defect/dipole polarization and increased graphitization degree and conductivity loss. As a result, one broad high-frequency absorption band was exhibited by carbon planar helixes produced at 400 °C− 500 °C, two broad absorption bands were exhibited by those formed at 600 °C, and three absorption bands were exhibited by those formed at 700 °C − 800 °C. The carbon planar helix formed at 700 °C exhibited broader bandwidth (4.96 GHz), thinner sample thickness (1.4 mm), and stronger absorption (−35.44 dB) than those of other absorbers. The superior properties are attributed to a combination of dipole/defect polarization, interface polarization, conductivity loss, multiple scattering, and multiple LC-resonances generated from the unique planar helical structure, defects, heteroatoms, and local electric network.

Tunable polaritons of spiral nanowire metamaterials

The tunable spiral nanowire metamaterial design at optical frequency is presented, and the surface polaritons are theoretically studied. It was found that the dispersions of the polaritons could be tuned by varying physical dimensions of the spiral nanowire metamaterial. This geometry is unique. Doing so, one may dynamically control the properties of surface polaritons. In addition, the Ferrell–Berreman modes can be excited that is impossible with the regular nanowire metamaterials having the circular cross-section of the nanowires. Herein, the presence of Ferrell–Berreman branches is confirmed by the performed analysis of the metamaterial band structure. It is worthwhile noting, that existence of Ferrell–Berreman modes is possible without epsilon-near-zero (ENZ) regime. The design of devices where Ferrell–Berreman modes can be exploited for practical applications ranging from plasmonic sensing to imaging and absorption enhancement is possible because of the propagation constant revealing subtle microscopic resonances.

Three-Dimensional Self-assembled Hairball-Like VS4 as High-Capacity Anodes for Sodium-Ion Batteries

HighlightsThe unique hairball-like VS4 composed of spiral nanowires was successively constructed through a one-step hydrothermal method.The prepared hairball-like VS4 exhibits high capacity and long cycle stability for Na+ storage at room temperature, and it can tolerate drastic temperature changes.The ex situ characterization and electrochemical kinetic analysis reveal that the storage mechanisms of VS4 changed with the increase in the number of cycles.

Gold nanospirals on colloidal gold nanoparticles

Synthesis of asymmetric nanostructures has always been a great challenge. In particular, there are only limited approaches for growing spiral nanowires in solution, and almost all of them require templates. Here, as a step in advancing the synthetic capability at the nanoscale, we report a wet chemistry template-free approach for growing hybrids spiral gold nanowires. The spiral gold nanowires were grown from the surface of colloidal gold nanoparticles, forming hybrid Au nanostructures. As an application of the active surface growth mechanism, the mechanistic understanding enables systematic adjustment of the nanowire morphology. The length and width of the spiral nanowires could be readily adjusted. Furthermore, the number of spiral nanowire on each Au nanoparticle, could be tuned by the pre-hydrolysis of the surface modification reagent. Such versatile system allows creation of complex nanostructures like the octopus-like and spider-like Au hybrids.

Spirals and helices by asymmetric active surface growth.

We show that spiral and helical Au nanowires can be directly grown via the active surface growth mechanism. The formation of spiral nanowires as opposed to straight nanowires is not triggered by the presence of a particular reactant, but controlled by the ratio of reactant concentrations. We propose that the asymmetric blocking of the Au-substrate interface induces imbalanced growth of the nanowire, causing it to curve. Blocking a single corner of the active interface leads to spiral nanowires whereas blocking two corners leads to helical nanowires. Spiral and helical nanowires become more frequent when the diffusion of Au is the limiting factor, as the reactant ratio falls below a critical value. The transition from helices to spirals and finally to nearly straight nanowires indicates a gradual loss of the blocked sites, hence supporting the asymmetric blocking mechanism.

Magnetization reversal in ferromagnetic spirals via domain wall motion

Domain wall dynamics have been investigated in a variety of ferromagnetic nanostructures for potential applications in logic, sensing, and recording. We present a combination of analytic and simulated results describing the reliable field driven motion of a domain wall through the arms of a ferromagnetic spiral nanowire. The spiral geometry is capable of taking advantage of the benefits of both straight and circular wires. Measurements of the in-plane components of the spirals' magnetization can be used to determine the angular location of the domain wall, impacting the magnetoresistive applications dependent on the domain wall location. The spirals' magnetization components are found to depend on the spiral parameters: the initial radius and spacing between spiral arms, along with the domain wall location. The magnetization is independent of the parameters of the rotating field used to move the domain wall, and therefore the model is valid for current induced domain wall motion as well. The speed of the ...

Electrochemistry of tin in the 1-ethyl-3-methylimidazolium dicyanamide room temperature ionic liquid

The electrochemistry of Sn(II) was studied in the room temperature ionic liquid 1-ethyl-3-methylimidazolium dicyanamide (EMI-DCA) on a glassy carbon (GC) and a polycrystalline Pt electrode at 40 °C. The Sn(II) species was introduced into the ionic liquid by either dissolution of SnCl 2 or anodizing a Sn wire. The reduction potential of the Sn(II)/Sn couple produced in these two solutions was found to be different, indicating that different Sn(II) species may be present. The order of the reduction potential of the two Sn(II) species indicates that the Gutmann donor ability of the anions is likely to be DCA − > Cl −. Cyclic voltammetry indicates the stripping efficiency is >90% on the Pt but only 40% on the GC electrode. Analysis of the chronoamperometric transient behavior during electrodeposition suggests that the deposition of Sn on the GC electrode involves a three dimensional progressive nucleation on a finite number of active sites. The diffusion coefficient of SnCl 2 dissolved in the EMI-DCA was found to be 9.8 × 10 −7 cm 2 s −1 which is in the same order of magnitude as those reported for SnCl 2 in several other ionic liquids. Depending on the deposition potentials, potentiostatic electrolysis produced Sn deposits with various unusual morphologies such as hexagonal tubes, spiral nanowires, and dendrite.

Structure and thermal stability of gold nanowire encapsulated in carbon nanotube

The structure and thermal stability of gold nanowire encapsulated in single-walled carbon nanotube (SWCNT) were studied by molecular dynamics simulations. A (8,8) SWCNT was used as a model system and the simulated annealing method was employed to find the stable structure of the gold nanowire at room temperature. Ourresults show that the gold nanowire encapsulated in a (8,8) SWCNT has a cylindrical shape and a helical shell structure. The helical-shell nanowire is thermally stable at temperatures much higher than the melting temperature of its bulk counterpart and is different from the gold nanowire formed in free space without the nanotube envelope. We also found that the spiral nanowire undergoes structural changes at higher temperatures.