Structural and Magnetic Properties of Electrodeposited Ni_(70)Fe_(30) Nanowire Array

Ordered Ni70Fe30 nanowire array was fabricated in a porous alumina template by alternating current electrodeposition. The structural and magnetic properties of the as-obtained nanowire array were investigated by SEM, TEM, XRD, EDS and VSM. The results indicate that the as-obtained Ni70Fe30 nanowires exhibit a diameter of about 69.9 nm and aspect ratio of more than 60. Meanwhile, a preferred orientation [110] of bcc lattice was observed. The as-obtained nanowire array has an obvious magnetic anisotropy, of which the easy direction is perpendicular to the surface of the array. Moreover, after annealed, the Ni70Fe30 nanowire array exhibits an enhanced magnetic anisotropy.

An effective surface-enhanced Raman scattering template based on gold nanoparticle/silicon nanowire arrays

A large-scale Si nanowire array （SiNWA） is fabricated with gold （Au） nanoparticles by simple metal-assisted chemical etching and metal reduction processes. The three-dimensional nanostructured Au/SiNWA is evaluated as an active substrate for surface-enhanced Raman scattering （SERS）. The results show that the detection limit for rhodamine 6G is as low as 10-7 M, and the Raman enhancement factor is as large as 105 with a relative standard deviation of less than 25%. After the calibration of the Raman peak intensifies of rhodamine 6G and thiram, organic molecules could be quantitatively detected. These results indicate that Au/SiNWA is a promising SERS-active substrate for the detection of biomolecules present in low concentrations. Our findings are an important advance in SERS substrates to allow fast and quantitative detection of trace organic contaminants.

Exciton emissions of CdS nanowire array fabricated on Cd foil by the solvothermal method

Nanowires have recently attracted more attention because of their low-dimensional structure, tunable optical and electrical properties for next-generation nanoscale optoelectronic devices. Cd S nanowire array, which is(002)-orientation growth and approximately perpendicular to Cd foil substrate, has been fabricated by the solvothermal method. In the temperature-dependent photoluminescence, from short wavelength to long wavelength, four peaks can be ascribed to the emissions from the bandgap, the transition from the holes being bound to the donors or the electrons being bound to the acceptors, the transition from Cd interstitials to Cd vacancies, and the transition from S vacancies to the valence band,respectively. In the photoluminescence of 10 K, the emission originated from the bandgap appears in the form of multiple peaks. Two stronger peaks and five weaker peaks can be observed. The energy differences of the adjacent peaks are close to 38 me V, which is ascribed to the LO phonon energy of Cd S. For the multiple peaks of bandgap emission, from low energy to high energy, the first, second, and third peaks are contributed to the third-order, second-order, and first-order phonon replica of the free exciton A, respectively;the fourth peak is originated from the free exciton A;the fifth peak is contributed to the first-order phonon replica of the excitons bound to neutral donors;the sixth and seventh peaks are originated from the excitons bound to neutral donors and the light polarization parallel to the c axis of hexagonal Cd S, respectively.

Cu nanowire array with designed interphases enabling high performance Si anode toward flexible lithium-ion battery

To meet the growing demand for wearable smart electronic devices,the development of flexible lithium-ion batteries(LIBs)is essential.Silicon is an ideal candidate for the anode material of flexible lithium-ion batteries due to its high specific capacity,low working potential,and earth abundance.The largest challenge in developing a flexible silicon anode is how to maintain structural integrity and ensure stable electrochemical reactions during external deformation.In this work,we propose a novel design for fabricating core–shell electrodes based on a copper nanowire(CuNW)array core and magnetron sputtered Si/C shell.The nanowire array structure has characteristics of bending under longitudinal stress and twisting under transverse stress,which helps to maintain the mechanical stability of the structure during electrode bending and cycling.The low-temperature annealing generates a small amount of Cu3Si alloy,which enhances the connection strength between Si and the conductive network and solves the poor conductivity problem of Si,which is known as a semiconductor material.This unique configuration design of CuNW@Si@C-400℃ leads to stable long cycle performance of 1109 mAh∙g^(-1) after 1000 cycles and excellent rate performance of 500 mAh∙g^(-1) at a current density of 10 A∙g^(-1).Furthermore,the CuNW@Si@C-400℃||LiFePO_(4)(LFP)full battery demonstrates excellent flexibility,with a capacity retention of more than 96%after 100 bends.This study provides a promising strategy for the development of flexible lithium-ion batteries.

Monolithically integrated CoP nanowire array： An on/off switch for effective on-demand hydrogen generation via hydrolysis of NaBH4 and NH3BH3

The issues of hydrogen generation and storage have hindered the widespread use and commercialization of hydrogen fuel cell vehicles. It is thus highly attractive, but the design and development of highly active non-noble-metal catalysts for on-demand hydrogen release from alkaline NaBH4 solution under mild conditions remains a key challenge. Herein, we describe the use of CoP nanowire array integrated on a Ti mesh （CoP NA/Ti） as a three-dimensional （3D） monolithic catalyst for efficient hydrolytic dehydrogenation of NaBH4 in basic solutions. The CoP NAFFi works as an on/off switch for on-demand hydrogen generation at a rate of 6,500 mL/（min.g） and a low activation energy of 41 kJ/mol. It is highly robust for repeated usage after recycling, without sacrificing catalytic performance. Remarkably, this catalyst also performs efficiently for the hydrolysis of NH3BH3.

Micromagnetic simulation on the dynamic susceptibility spectra of cobalt nanowires arrays:the effect of magnetostatic interaction

Micromagnetic simulations have been performed to obtain the dynamic susceptibility spectra of 4×4 cobalt nanowire arrays with different spatial configurations and geometries. The susceptibility spectra of isolated wires have also been simulated for comparison purposes. It is found that the susceptibility spectrum of nanowire array bears a lot of similarities to that of an isolated wire, such as the occurrences of the edge mode and the bulk resonance mode. The simulation results also reveal that the susceptibility spectrum of nanowire array behaves like that of single isolated wire as the interwire distance grows to an extent, which is believed due to the decrease of magnetostatic interaction among nanowires, and can be further confirmed by the static magnetic hysteresis simulations. In comparison with single nanowire, magnetostatic interaction may increase or decrease the resonance frequencies of nanowire arrays assuming a certain interwire distance when the length of array increases. Our simulation results are also analysed by employing the Kittel equation and recent theoretical studies.

Ultraviolet-infrared dual-color photodetector based on vertical GaN nanowire array and graphene

A monolithic integrated ultraviolet-infrared(UV-IR) dual-color photodetector based on graphene/GaN heterojunction was fabricated by vertically integrating a GaN nanowire array on a silicon substrate with monolayer graphene. The device detects UV and IR lights by different mechanisms. The UV detection is accomplished by the forbidden band absorption of GaN, and the IR detection is realized by the free electron absorption of graphene. At peak wavelengths of 360 nm and 1540 nm, the detector has responsivities up to 6.93 A/W and 0.11 A/W, detection efficiencies of 1.23 × 1012 cm·Hz1/2·W-1 and 1.88 × 1010 cm·Hz1/2·W-1, respectively,and a short response time of less than 3 ms.

Magnetic moment distributions in a-Fe nanowire array

a-Fe nanowire array has been electrodeposited into anodic aluminum oxide template. The magnetic moment distributions, in the interior and near the extremities of a-Fe nanowire with 60 nm in diameter, have been studied by means of transmission M鰏sbauer spectroscopy (MS), conversion electron M鰏sbauer spectroscopy (CEMS) and micromagnetic simulation. Transmission M鰏sbauer spectrum (MS) shows that the magnetic moments, inside the a-Fe nanowire array, are well parallel to nanowire, while conversion electron M鰏sbauer spectrum (CEMS) reveals that the magnetic moments, near the extremities of nanowire, diverge from the long axis of wire, and the average diverging angle calculated by the intensity ratio of the 2,5 peaks is about 24.0°. Moreover, the magnetic moment distributions of different depths to the top of wire are counted using micromagnetic simulation, which indicates that, the interior magnetic moments are strictly parallel to nanowire, and the closer the magnetic moment to the top of wire, the larger the diverging angle. Magnetic measurement shows that this -Fe nanowire array represents a strong magnetic anisotropy.

GISAXS and SAXS studies on the spatial structures of Co nanowire arrays

The spatial structures of magnetic Co nanowire array embedded in anodic aluminium membranes were investigated by grazing incidence small angle X-ray scattering （GISAXS） and conventional small angle X-ray scattering （SAXS） techniques. Compared with SEM observation, the GISAXS and SAXS measurements can get more overall structural information in a large-area scale. In this study, the two-dimensional GISAXS pattern was well reconstructed by using the IsGISAXS program. The results demonstrate that the hexagonal lattice formed by the Co nanowires is distorted （a ≈105 nm, b ≈95 nm）. These Co nanowires are isolated into many structure domains with different orientations with a size of about 2 p_m. The SAXS results have also confirmed that the nanopore structures in the AAM can be retained after depositing Co nanowires although the Co nanowires can not completely but only just fill up the nanopores. These results are helpful for understanding the global structure of the Co nanowire array.

Bi-based Nanowire and Nanojunction Arrays:Fabrication and Physical Properties

This article reviews the recent developments in the fabrication and properties of one-dimensional （1D） Bi-based nanostructures, including Bi, Sb, BixSb1-x and Bi2Te3 nanowire arrays, and Bi-Bi and Bi-Sb nanojunction arrays. In this article, we present an efiective method to fabricate Bi nanowire arrays with difierent diameters in anodic alumina membrane （AAM） with a single pore size by the pulsed electrodeposition. The fabrication of the high-filling and ordered Bi1-xSbx and Bi2Te3 single crystalline nanowire arrays, the Bi nanowire metalsemiconductor homojunction and Bi-Sb nanowire metal-semiconductor heterojunction arrays by the pulsed electrodeposition are reported. The factors controlling the composition, diameter, growth rate and orientation of the nanowires are analyzed, and the growth mechanism of the nanowire and nanojunction arrays are discussed together with the study of the electrical and thermal properties of Bi-based nanowires and nanojunctions.Finally, this review is concluded with some perspectives on the research directions and focuses in the Bi-based nanomaterials fields.

Improved electron capture capability of field-assisted exponential-doping GaN nanowire array photocathode

The exponential-doping GaN nanowire arrays(GaN NWAs)photocathode has a"light-trapping effect",and the built-in electric field can promote the concentration of the photogene rated carrier center to the top surface of the nanowire.However,in the preparation ofactual NWAs photocathodes,the problem that photons emitted from the sides of the nanowires cannot be effectively collected has been encountered.Our proposed field-assisted exponential-doping GaN NWAs can bend the motion trajectory of the emitted electrons toward the collecting side.In this study,the quantum efficiency(QE)and collection efficiency(CE)of the external field-assisted exponential-doping GaN NWAs photocathode are derived based on the two-dimensional carrier diffusion equation and the initial energy and angular distribution,respectively.For a field-assisted exponential-doping GaN NWAs with a width d=200 nm and a height H=400 nm,the optimal structural parameters are obtained:the incident angleθ=50°and the nanowire spacing is L=335.6 nm.On this basis,the field intensity of 0.5 V/μm can maximize the CE of the NWAs.All the results show that the field-assisted approach does contribute to the collection of emitted electrons,which can provide theoretical guidance for high-performance electron sources based on exponential-doping GaN NWAs photocathodes.And field-assisted exponential-doping GaN NWAs cathode is expected to be verified by the experimental results in the future.

Ultra-dense planar metallic nanowire arrays with extremely large anisotropic optical and magnetic properties

A nanofabrication method for the production of ultra-dense planar metallic nanowire arrays scalable to wafer-size is presented. The method is based on an efficient template deposition process to grow diverse metallic nanowire arrays with extreme regularity in only two steps. First, Ⅲ-Ⅴ semiconductor substrates are irradiated by a low-energy ion beam at an elevated temperature, forming a highly ordered nanogroove pattern by a ＂reverse epitaxy＂ process due to self-assembly of surface vacancies. Second, diverse metallic nanowire arrays （Au, Fe, Ni, Co, FeAl alloy） are fabricated on these Ⅲ-Ⅴ templates by deposition at a glancing incidence angle. This method allows for the fabrication of metallic nanowire arrays with periodicities down to 45 nm scaled up to wafer-size fabrication. As typical noble and magnetic metals, the Au and Fe nanowire arrays produced here exhibited large anisotropic optical and magnetic properties, respectively. The excitation of localized surface plasmon resonances （LSPRs） of the Au nanowire arrays resulted in a high electric field enhancement, which was used to detect phthalocyanine （CoPc） in surface-enhanced Raman scattering （SERS）. Furthermore, the Fe nanowire arrays showed a very high in-plane magnetic anisotropy of approximately 412 mT, which may be the largest in-plane magnetic anisotropy field yet reported that is solely induced via shape anisotropy within the plane of a thin film.

Effect of MWCNT Inclusion in TiO_2 Nanowire Array Film on the Photoelectrochemical Performance

Rutile TiO2 nanowire array films with multi-walled carbon nanotube （MWCNT） inclusion perpendicularly grown on fluorine-doped tin oxide （FTO） substrate were prepared by a facile hydrothermal method. The absorption edges of the TiO2 nanowire array films are blue-shifted with increasing MWCNT content. The resistance of the TiO2 nanowire array film is decreased by MWCNT inclusion. The optimum TiO2/MWCNT molar ratio in the feedstock is 1：0.1. For the TiO2 nanowire array film with MWCNT inclusion served as electrode in dye-sensitized solar cell （DSSC）, an overall 194% increase of photoelectric conversion efficiency has been achieved.

Boron-assisted growth of silica nanowire arrays and silica microflowers for bendable capacitor application

Aligned silica nanowire arrays and silica microflowers were fabricated using boron as the catalyst and under the flow N2 gas. The obtained product had no catalyst contamination. And silica nanowires had long lengths of a few hundreds. The growth of nanowire arrays and microflowers was explained using mechanism. Parallel-plate capacitors using silica nanowire mat as the dielectric were fabricated. The silica nanowire capacitor shows a specific capacitance of 0.24 n F/cm~2 at the frequency of 100 Hz. The capacitor is not monotone changing with the frequency. The measurement of mechanical properties shows that the tunneling current increases along with an increase in bending angle of the capacitor.

Absorption through a coupled optical resonance in a horizontal InP nanowire array

We study through electromagnetic modeling the absorption of light of a given wavelength in an array of horizontal In P nanowires of diameter less than 100 nm. Such absorption is performed most efficiently by using polarized light and by exciting a coupled optical resonance in a sparse array. In that case, we excite a resonance in the individual nanowires and couple the resonances in neighboring nanowires through a lattice resonance of the periodic array.At such a resonance, an array with nanowires of 80 nm in diameter can absorb more than eight times more strongly than a tight-packed array, despite containing a seven times smaller amount of the absorbing InP material.

Wafer-level and highly controllable fabricated silicon nanowire transistor arrays on （111） silicon-on-insulator （SOl） wafers for highly sensitive detection in liquid and gaseous environments

This paper presents a wafer-level and highly controllable fabrication technology for silicon nanowire field-effect transistor （SiNW-FET arrays） on （111） silicon- on-insulator （SOI） wafers. Herein, 3,000 SiNW FET array devices were designed and fabricated on 4-inch wafers with a rate of fine variety of more than 90% and a dimension deviation of the SiNWs of less than ＋ 20 nm in each array. As such, wafer-level and highly controllable fabricated SiNW FET arrays were realized. These arrays showed excellent electrical properties and highly sensitive determination of pH values and nitrogen dioxide. The high-performance of the SiNW FET array devices in liquid and gaseous environments can enable the detection under a wide range of conditions. This fabrication technology can lay the foundation for the large-scale application of SiNWs.

Self-organization and tunable characteristic lengths of twodimensional hexagonal superlattices of nanowires directly grown on substrates

The organization of nano-objects on macroscopic surfaces is a key challenge for the technological improvement and implementation of nanotechnologies.For achieving operational functions,it is required to assemble nano-objects as controllable building blocks in highly ordered superstructures.Herein,we demonstrate the growth and self-organization of metallic nanowires on surfaces into hexagonal superlattices with tunable characteristic lengths depending of the stabilizing surfactants employed.Starting from a reacting mixture containing a Pt(111)substrate,a Co organometallic precursor,an amine,and an acid dissolved in a solvent,we quantify the structural evolution of superlattices of vertical single-crystalline Co nanowires on Pt,using a combined analysis of small angle neutron scattering,transmission,and scanning electron microscopies.We show the concerted steps of a spontaneous growth and self-organization of the nanowires into two-dimensional(2D)hexagonal lattice on Pt,at intervals starting from a few hours of reaction to a highly ordered superlattice at longer times.Furthermore,it is shown that apart from long-chain acid and long-chain aliphatic amine pairs used as stabilizers,the combination of a long-chain aliphatic and a short-chain aromatic ligand in the synthesis can also be employed for the nanowire superlattices development.Interestingly,the possibility to employ different pairs allows quantitative modulation of the nanowire arrays,such as the interwire distance and the packing fraction.

Vertical nanowires enhanced X-ray radiation damage of cells

Cell behavior is affected by nanostructured surface,but it remains unknown how ionizing radiation af-fects cells on nanostructured surface.This paper reports an experimental investigation of X-ray radiation induced damage of cells placed on an array of vertically aligned silicon nanowires.X-ray photoelectrons and secondary electrons produced from nanowire array are measured and compared to those from flat silicon substrate.The cell functions including morphology,viability,adhesion and proliferation have been examined and found to be drastically affected when cells are exposed to X-ray radiation,compared to those sitting on flat substrate and those only exposed to X-ray.The enhanced cell damage on nanowires upon X-ray exposure is attributed to nanowire enhanced production of photoelectrons including Auger electrons and secondary electrons,which have high escaping probability from sharp tips of nanowires.The escaped photoelectrons ionize water molecules and generate hydroxyl free radicals that can damage DNAs of cells.An inference of this work is that the contrast in scanning electron microscopy is useful in assessing the effects of nanomaterials for enhanced X-ray radiation therapy.

NOR logic function of a bendable combination of tunneling field-effect transistors with silicon nanowire channels

In this study, we propose a novel combination of tunneling field-effect transistors （TFETs） with asymmetrically doped p^＋-i-n^＋ silicon nanowire （SiNW） channels on a bendable substrate. The combination of two n-channel SiNW-TFETs （NWTFETs） in parallel and two p-channel NWTFETs in series operates as a two-input NOR logic gate. The component NWTFETs with the n- and p-channels exhibit subthreshold swings （SSs） of 69 and 53 mV·dec^-1, respectively, and the on/off current ratios are -106. The NOR logic operation is sustainable and reproducible for up to 1,000 bending cycles with a narrow transition width of -0.26 V. The mechanical bendability of the bendable NWTFETs shows that they are stable and have good fatigue properties. To the best of our knowledge, this is the first study on the electrical and mechanical characteristics of a bendable NOR logic gate composed of NWTFETs.

Ternary nanoarray electrode with corn-inspired hierarchical design for synergistic lithium storage

Single-component anode materials can barely satisfy the growing demand for next-generation Li-ion batteries with higher capacity and cyclability. Thus developing multi-component synergistic electrodes has become a critical issue. Herein, inspired by natural corn, a ternary hierarchical self-supported array design is proposed. Based on a sequential transformation route, Si/C-modified C0304 nanowire arrays are constructed on 3D Ni foams to form a binder-free integrated electrode. Specifically, an ionic liquid-assisted electrodeposition strategy is employed to prepare discrete ultrafine Si nanoparticles on nanoscale array substrates, which follow the Volmer-Weber island growth mode. In this corn-mimetic system, kernel-like Si nanoparticles and a husk-like carbon coating layer function as enhancing and protecting units, respectively, to improve the capacity and stability of the cobalt oxide basic unit. Taking advantage of a synergistic effect, the ternary nanoarray anode achieves a significant performance enhancement compared to pristine Co304, showing a special capacity as high as -1,000 mAh·g^-1 at 100 mA·g^-1. By extending this corn-mimetic hierarchical array design to other basic, enhancing, and protecting units, new ideas for constructing synergistic nano-architectures for energy conversion and storage field are developed.