Fabrication Of Nanowires Research Articles

Location-specific fabrication of suspended nanowires using electrospun fibers on designed microstructure

While there have been remarkable improvements in the fabrication of suspended nanowires, placing a single nanowire at the desired location remains to be a challenging task. In this study, a simple method is proposed to fabricate suspended nanowires at desired locations using an electrospinning process and a designed microstructure. Using electrospun polymer fibers on the designed microstructure as a sacrificial template, various materials are deposited on it, and the electrospun fibers are selectively removed, leaving only nanowires of the deposited material. After the polymer fibers are removed, the remaining metal fibers agglomerate into a single nanowire. Throughout this process, including the removal of the polymer fibers, the samples are not exposed to high temperatures or chemicals, thereby allowing the formation of nanowires without oxidation or contamination. The diameter of the nanowire can be controlled in the electrospinning process, and a suspended Pd nanowire with a minimum diameter of 100 nm is fabricated. Additionally, a suspended single Pd nanowire-based H2 gas sensor fabricated using the proposed process exhibits a highly sensitive response to H2 gas.

Synthesis and characterization of a Sb2Te3/Bi2Te3 p-n junction heterostructure via electrodeposition in nanoporous membranes

SummaryTopological insulators (TIs) are bulk insulators with metallic surface states that can be described by a single Dirac cone. However, low-dimensional solids such as nanowires (NWs) are a challenge, due to the difficulty of separating surface contributions from bulk carriers. Fabrication of NWs with high surface-to-volume ratio can be realized by different methods such as chemical vapor transport, molecular beam epitaxy, and electrodeposition. The last method is used in the present work allowing the growth of structures such as p-n junctions, intercalation of magnetic or superconducting dots. We report the synthesis of high-quality TI NW: Bi2Te3, Sb2Te3 and p-n junction via electrodeposition. Structural, morphological, and nanostructure properties of NWs have been investigated by various characterization techniques. Interface structures and lateral heterojunctions (LHJ) in p-n junction NWs has also been made.

A conductive polymer nanowire including functional quantum dots generated via pulsed laser irradiation for high-sensitivity sensor applications

The fabrication of functional conductive polymer nanowires (CPNWs), including ultrahigh-sensitive flexible nanosensors has attracted considerable attention in field of the Internet of Things. However, the controllable and space-selective growth of CPNWs remains challenging, and a novel synthetic technique is required. Herein, we demonstrate the synthesis of space-selective CPNWs that include quantum dots (QDs) with changeable optical properties via single-pulse laser irradiation in air at atmospheric pressure. Time-resolved shadowgraphy was applied to monitor the synthetic process of the CPNWs and optimise the process conditions. The electrical conductivity of the CPNWs with QDs (QD-CPNWs) was analysed in the presence and absence of light irradiation and was found to change drastically (over six times) under light irradiation. QD-CPNW synthesis under laser irradiation shows great potential for fabricating highly photosensitive functional nanomaterials and is expected to be applied in the production of ultrahigh-sensitive photosensors in the future.

Fabrication and Characterization of CuO nanowires on V-shaped Microgroove surfaces

This study developed a facile and scalable thermal oxidation method to prepare CuO nanowires on the electro-discharge machining (EDM) processed V-shaped microgrooves. The formation feasibility, surface morphology, and wetting properties of nanowires on V-shaped microgrooves were explored by the variation of thermal oxidation temperatures from 300 to 600 °C, and oxidation times from 2 h to 8 h. Nanowires were found to successfully synthesized on the V-shaped microgrooves surfaces when annealing temperature was 400 °C or higher. The microvoids or microcavities on the EDM processed V-shaped microgrooves surfaces contributed to the stress grain boundary (GB) diffusion of copper atoms, and facilitated the growth of nanowires. The diameter of nanowires increased monotonically when the annealing temperatures increased, whereas it almost kept unchanged with increasing annealing times. The length of nanowires was influenced positively by both annealing temperature and annealing time. All the nanowire samples showed hydrophobic properties of water.

Robust silver nanowire membrane with high porosity to construct stable Li metal anodes

Silver is a promising candidate component in the fabrication of Li metal anodes. While most efforts are focused on performance improvement via regulating the lithiophilicity of Ag-based electrodes, the detailed lithiation behavior of Ag nanoparticles is another key research topic for the rational design of Li–Ag anodes. In this work, we report the fabrication of Ag nanowire (AgNW) membranes to examine their electrochemical alloying process in Li cells. The robust and compact membranes show high porosity up to 90% with tunable thickness of 1–10 μm, thus facilitating lithiation reactions as well as accommodating the subsequently deposited Li. Electrochemical tests reveal compositions and phases of lithiated AgNWs can be varied depending on external current, and the electrochemically formed Li–Ag interfaces effectively guide uniform Li deposition from both experimental and theoretical analyses. Full cells composed with thin Li-AgNW composite anodes (10 mAh/cm2) and high-loading LiFePO4 cathodes (12 mg/cm2) also demonstrate stable life over 150 cycles. These findings provide insight into fundamental Ag electrochemistry in Li cells and meanwhile highlight the great potentials of Ag-based Li anodes for practical applications.

Fabrication of freestanding Pt nanowires for use as thermal anemometry probes in turbulence measurements

We report a robust fabrication method for patterning freestanding Pt nanowires for use as thermal anemometry probes for small-scale turbulence measurements. Using e-beam lithography, high aspect ratio Pt nanowires (~300 nm width, ~70 µm length, ~100 nm thickness) were patterned on the surface of oxidized silicon (Si) wafers. Combining wet etching processes with dry etching processes, these Pt nanowires were successfully released, rendering them freestanding between two silicon dioxide (SiO2) beams supported on Si cantilevers. Moreover, the unique design of the bridge holding the device allowed gentle release of the device without damaging the Pt nanowires. The total fabrication time was minimized by restricting the use of e-beam lithography to the patterning of the Pt nanowires, while standard photolithography was employed for other parts of the devices. We demonstrate that the fabricated sensors are suitable for turbulence measurements when operated in constant-current mode. A robust calibration between the output voltage and the fluid velocity was established over the velocity range from 0.5 to 5 m s−1 in a SF6 atmosphere at a pressure of 2 bar and a temperature of 21 °C. The sensing signal from the nanowires showed negligible drift over a period of several hours. Moreover, we confirmed that the nanowires can withstand high dynamic pressures by testing them in air at room temperature for velocities up to 55 m s−1.

Fabrication and characterization of silicon nanowires with MACE method to influence the optical properties

We are presenting here fabrication of silicon (Si) nanowires (NWs) arrays by using Si (100) wafer as substrate, by metal assisted chemical etching (MACE) method. The Si-NWs growth on the Si wafer has been done by using etching time of 45 min in etching solution of hydrogen fluoride and hydrogen peroxide. X-ray diffraction (XRD) has been used for the structural analysis of NWs to estimate the crystalline size, micro-strain, dislocation density of fabricated nanostructures. The surface morphology of Si-NWs array has been studied through field effect scanning electron microscopy (FE-SEM). The optical properties like energy band gap of fabricated Si-NWs has been carried out through UV–Vis diffuse reflectance spectroscopy (UV DRS) and photoluminescence (PL) spectroscopy.

Fabrication of platinum nanowires by centrifugal electrospinning method for proton exchange membrane fuel cell

The centrifugal electrospinning method is employed to fabricate platinum (Pt) nanowires and its application for proton exchange membrane fuel cell (PEMFC) is evaluated. The nanowires are produced from a polymer solution containing hexachloroplatinic acid hydrate as Pt precursor and polyvinyl pyrrolidone (PVP). The effects of system parameters on the morphology of Pt nanowires are studied including the PVP concentration, rotation speed of spinneret, and applied electric field. The electrochemically active surface area (ESA) of the Pt nanowires is characterized by cyclic voltammetry tests. The produced Pt nanowires are also used as electrocatalysts in the cathode of PEMFC and the cell performance is tested. Results show the centrifugal electrospinning method can successfully produce Pt nanowires with mean diameter of 54 ± 14 nm and ESA of 5.64m2g-1, which are comparable to those of traditional electrospun Pt nanowires. The production rate of Pt nanowires can be improved greatly in comparison with the conventional electrospinning technique. It is also found that by the accelerated degradation tests, Pt nanowires demonstrate better durability than commercial Pt/C and the employment of Pt nanowires as electrocatalysts mixed with Pt/C can enhance the fuel cell performance. The present results reveal the centrifugal electrospinning method is an efficient approach to fabricate Pt nanowires for the application in PEMFCs. Novelty statement A centrifugal electrospinning device was designed to fabricate Pt nanowires successfully with good morphology. The production rate of Pt nanowires is enhanced greatly in comparison with the conventional electrospinning method. Electrocatalysts composed of the produced Pt nanowires and Pt/C is found to be able to improve the performance of PEMFC.

Optimizing interferences of DUV lithography on SOI substrates for the rapid fabrication of sub-wavelength features

Scalable fabrication of Si nanowires with a critical dimension of about 100 nm is essential to a variety of applications. Current techniques used to reach these dimensions often involve e-beam lithography or deep-UV (DUV) lithography combined with resolution enhancement techniques. In this study, we report the fabrication of <150 nm Si nanowires from SOI substrates using DUV lithography (λ = 248 nm) by adjusting the exposure dose. Irregular resist profiles generated by in-plane interference under masking patterns of width 800 nm were optimized to split the resulting features into twin Si nanowires. However, masking patterns of micrometre size or more on the same photomask does not generate split features. The resulting resist profiles are verified by optical lithography computer simulation based on Huygens−Fresnel diffraction theory. Photolithography simulation results validate that the key factors in the fabrication of subwavelength nanostructures are the air gap value and the photoresist thickness. This enables the parallel top-down fabrication of Si nanowires and nanoribbons in a single DUV lithography step as a rapid and inexpensive alternative to conventional e-beam techniques.

Effective surface modification method of silver nanowires with alkaline solutions for enhancing electrical property of silver transparent electrode

Transparent electrodes are usually manufactured by depositing electrical materials (silver, ITO, CNT, etc.) on selective substrates. Since the polymeric capping agent is inevitably using to forming certain morphology during the silver nanowires fabrication, the used polyvinylpyrrolidone (hereinafter, PVP) can be partially remain at the surface in [100] facet of the conductive materials with high surface energy, even after conducting washing for purpose of removing. The residual PVP adverse effect to electrical conductivity of manufactured transparent electrode due to the decline of the conductive material contact area. Thus, the surface modification process of silver nanowires using an alkaline solution was performed for the purpose of improving the electrical conductivity of the manufactured transparent electrode, and the efficiency of enhancement electrical conductivity was demonstrated by removing residual PVP. Through these studies, the electrical characteristics were improved much better than the electrodes for which the surface improvement process had not progressed, and the efficiency improvement effect of the surface resistance standard of about 99% decrease was demonstrated. This results proved that the residual PVP was efficiently removed by inducing an ion substitution reaction between PVP and silver ions due to the certain chemical difference of the alkaline elements exposed through the surface modification process.

Ultrasensitive and easily reproducible biosensor based on novel doped MoS2 nanowires field-effect transistor in label-free approach for detection of hepatitis B virus in blood serum

An ultrasensitive field-effect transistor (FET) for hepatitis B virus deoxyribonucleic acid (HBV DNA) detection in label free approach and easily reproducible setup was reported. The fabricated FET biosensor was materialized by ZnO doped MoS2 nanowires (NWs). This report introduced a novel structure of the MoS2 in bio-sensing approach. Because of unique electrical and structural properties of MoS2, HBV biosensor could demonstrate the high sensitivity and showed the detection limit of 1 fM. The MoS2 NWs fabrication was materialized through ZnO based vapor-liquid-solid (VLS) technique. The fabricated device could measure the DNA targets in a linear concentration range from 0.5 pM to 50 μM. The dynamic response time of FET biosensor was 25 s. The functionality of the NWs biosensor for label-free measurements could be repeated for several times without any significant malfunction and biosensor could retain 96% of its initial response after eight weeks maintenance. The HBV biosensor showed high selectivity by discrimination the complementary DNA oligonucleotides from non-complementary and the mismatch (1, 2 and 3 bases) oligonucleotides. The materialized platform was desirably reproduced for HBV concentrations in human serum. The specificity of the biosensor was evaluated against several different types of DNAs and the fabricated device showed the outstanding performance. In order to optimize the device functionality, the biosensor was checked for two different human samples and device could distinguish the samples from each other in the same manner.

Magnetic Configurations in Modulated Cylindrical Nanowires.

Cylindrical magnetic nanowires show great potential for 3D applications such as magnetic recording, shift registers, and logic gates, as well as in sensing architectures or biomedicine. Their cylindrical geometry leads to interesting properties of the local domain structure, leading to multifunctional responses to magnetic fields and electric currents, mechanical stresses, or thermal gradients. This review article is summarizing the work carried out in our group on the fabrication and magnetic characterization of cylindrical magnetic nanowires with modulated geometry and anisotropy. The nanowires are prepared by electrochemical methods allowing the fabrication of magnetic nanowires with precise control over geometry, morphology, and composition. Different routes to control the magnetization configuration and its dynamics through the geometry and magnetocrystalline anisotropy are presented. The diameter modulations change the typical single domain state present in cubic nanowires, providing the possibility to confine or pin circular domains or domain walls in each segment. The control and stabilization of domains and domain walls in cylindrical wires have been achieved in multisegmented structures by alternating magnetic segments of different magnetic properties (producing alternative anisotropy) or with non-magnetic layers. The results point out the relevance of the geometry and magnetocrystalline anisotropy to promote the occurrence of stable magnetochiral structures and provide further information for the design of cylindrical nanowires for multiple applications.

In-situ growth and fabrication of metal-organic charge transfer complex nanowire devices with controlled diameter using dielectrophoretic force

Ultrathin Cu:TCNQ (Cu-tetracyanoquinodimethane) nanowires (∼10–50 nm diameter) are interesting from a fundamental point of view to study electrical as well as opto-electronic transport and also held promising interest in nanoelectronics, particularly for photodetector applications. Dielectrophoresis-based device fabrication from an aqueous solution is useful and has some potential applications. However, such device fabrication may degrade material property. Herein, we demonstrate directed in-situ growth and assembly of Cu:TCNQ nanowire at predefined electrodes in vacuum using dc dielectrophoresis. The mechanistic understanding of the process is verified by COMSOL Multiphysics simulation. The externally applied electric field also exploits to control over the number as well as diameter of the nanowire during growth. Field grown nanowires bridging two electrodes are structurally characterized using a unique challenging technique with Transmission Electron Microscope. The field-grown nanowires are found to have better electrical performance compared to normal growth.

Functionalization of 3-aminopropyltrimethoxysilane Self-Assembled Monolayers on ZnO/Au nanowires: Role of the Seed layer

We grew two different types of ZnO nanowires (NWs), both grown using the vapor–liquid-solid (VLS) technique but with two distinct types of seed layers. Morphology and crystal structure were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The seed layer and subsequent heat treatment resulted in the fabrication of NWs with different orientations and morphologies. After 3-aminopropyltrimethoxysilane (APTMS) functionalization, Photoluminescence (PL) spectroscopy revealed a shift in the spectra, whereas Fourier Transform Infrared Spectroscopy (FTIR-ATR) technique shown a characteristic peak of the Si-O-Si bond that is related to the APTMS multilayer. A mechanism has been proposed for different phases of NWs and their interaction with the molecular species. This work could provide a basis for optimizing the specific orientation in ZnO NWs for their potential use as gas sensors or detect biological compounds for environmental applications.

Fabrication and temperature-dependent electrical characterization of a C-shape nanowire patterned by a DNA origami

We introduce a method based on directed molecular self-assembly to manufacture and electrically characterise C-shape gold nanowires which clearly deviate from typical linear shape due to the design of the template guiding the assembly. To this end, gold nanoparticles are arranged in the desired shape on a DNA-origami template and enhanced to form a continuous wire through electroless deposition. C-shape nanowires with a size below 150nm on a {hbox {SiO}_2}/hbox {Si} substrate are contacted with gold electrodes by means of electron beam lithography. Charge transport measurements of the nanowires show hopping, thermionic and tunneling transports at different temperatures in the 4.2K to 293K range. The different transport mechanisms indicate that the C-shape nanowires consist of metallic segments which are weakly coupled along the wires.

Fabrication and Characterization of Zinc Oxide Nanowire Based Two‐electrode Capacitive Biosensors on Flexible Substrates for Estimating Glucose Content in a Sample

AbstractThe present work deals with fabrication and characterization of the zinc oxide (ZnO) nanowire based novel two‐electrode capacitive biosensors on flexible Polyethylene terephthalate (PET) substrates for accurate estimation of glucose by analyzing the fundamental dielectric nature of the relevant sample. The morphology and crystalline quality of grown nanowires are analyzed by using field‐emission scanning electron microscope (FESEM) and X‐ray diffractometer (XRD), respectively. Current and capacitance values of the device have been studied for ten different glucose concentrations relevant to the physiological standards. The analytical performance of the devices in terms of enzyme activity, reliability and flexibility has also been evaluated.

Preface to the special issue dedicated to Professor Richard P. Van Duyne (1945–2019)

Preface to the special issue dedicated to Professor Richard P. Van Duyne (1945–2019)

Nanowire Waveguides and Lasers: Advances and Opportunities in Photonic Circuits.

Due to their single-crystalline structures, comparatively large aspect ratios, tight optical confinement and smooth surfaces, nanowires have increasingly attracted research interests for both fundamental studies and technological applications in on-chip photonic devices. This class of nanostructures typically have cross-sections of 2~200 nm and lengths upwards of several micrometers, allowing for the bridging of the nanoscopic and macroscopic world. In particular, the lasing behaviors can be established from a nanowire resonator with positive feedback via end-facet reflection, making the nanowire a promising candidate in the next generation of optoelectronics. Consequently, versatile nanowire-based devices ranging from nanoscale coherent lasers, optical sensors, waveguides, optical switching, and photonic networks have been proposed and experimentally demonstrated in the past decade. In this article, significant progresses in the nanowire fabrication, lasers, circuits, and devices are reviewed. First, we focus on the achievements of nanowire synthesis and introduce the basics of nanowire optics. Following the cavity configurations and mode categories, then the different light sources consisting of nanowires are presented. Next, we review the recent progress and current status of functional nanowire devices. Finally, we offer our perspective of nanowires regarding their challenges and future opportunities in photonic circuits.

Fabrication of silver nanowire coated fibrous air filter medium via a two-step process of electrospinning and electrospray for anti-bioaerosol treatment

Antimicrobial agent treatment is needed to prevent airborne infections due to microorganisms causing diseases. Silver nanowires (AgNW) have been increasingly used in air filters for their superior antimicrobial performance. In this study, AgNWs (115 nm in diameter, 4–50 µm in length) were electrosprayed on the surface of polyacrylonitrile (PAN) fibres that were obtained by electrospinning. Filtration efficiency of the AgNW-coated fibres was tested by aerosolizing and convectively delivering test bacteria and virus particles to the fibres. Then the particles filtered on the fibres were cultured to evaluate antibacterial and antiviral abilities. The overall filtration efficiency of the fibres increased from 92% to 96.5% (at 2.5 cm/s of air velocity) to 98.3–99.6% after AgNW coating for 30 min (areal density = 2.352 μg per 1 cm2 of filter surface area), without affecting the pressure drop. The AgNW coating for 30 min significantly increased the antimicrobial efficiency to 98.0 ± 1.1% for Staphylococcus aureus (S. aureus), 95.2 ± 2.6% for Bacillus cereus (B. cereus), 93.7 ± 1.5% for Micrococcus luteus (M. luteus), and 72.5 ± 1.9% for bacteriophage MS2.

Fabrication and Characterization of Double- and Single-Clamped CuO Nanowire Based Nanoelectromechanical Switches.

Electrostatically actuated nanoelectromechanical (NEM) switches hold promise for operation with sharply defined ON/OFF states, high ON/OFF current ratio, low OFF state power consumption, and a compact design. The present challenge for the development of nanoelectromechanical system (NEMS) technology is fabrication of single nanowire based NEM switches. In this work, we demonstrate the first application of CuO nanowires as NEM switch active elements. We develop bottom-up and top-down approaches for NEM switch fabrication, such as CuO nanowire synthesis, lithography, etching, dielectrophoretic alignment of nanowires on electrodes, and nanomanipulations for building devices that are suitable for scalable production. Theoretical modelling finds the device geometry that is necessary for volatile switching. The modelling results are validated by constructing gateless double-clamped and single-clamped devices on-chip that show robust and repeatable switching. The proposed design and fabrication route enable the scalable integration of bottom-up synthesized nanowires in NEMS.