Hierarchical Nanowire Research Articles

A Highly Stretchable, Sensitive, and Transparent Strain Sensor Based on Binary Hybrid Network Consisting of Hierarchical Multiscale Metal Nanowires

AbstractHow to balance the relationship between stretchability, sensitivity, and optical transmittance remains an obstacle for the realization of high‐performance wearable strain sensors. Here, a highly stretchable, sensitive, and transparent strain sensor is presented by using a binary hybrid network consisting of hierarchical multiscale metal nanowires. Small‐sized silver nanaowire (AgNW) network is demonstrated to have considerable sensitivity but very limited sensing range. The introduction of the highly continuous gold nanowire backbone network can not only improve the stretchability by bridging the detached AgNW regions, but also provide excellent sensitivity in large strain range. As a result, the rationally designed hybrid network based strain sensor demonstrates a wide sensing range up to 90%, high gauge factor values from 12 at 5% to 2370 at 70%, high transmittance of 86%, and prominent cyclical stability (1000 times). The highly flexible strain sensor can be conformally attached to human body and succeeds in detecting a series of activities. Both of the outstanding sensing and optical performance endow the hybrid network based sensor great potential as invisible human‐monitoring device.

Hierarchical PbZrxTi1–xO3 Nanowires for Vibrational Energy Harvesting

Perovskite piezoelectric material nanostructures have gained immense interest in the energy harvesting community due to their ability of converting mechanical energy into electric power in a much more efficient manner. In this paper, we first successfully synthesized PbZrxTi1–xO3 (PZT) nanowires with unique hierarchical nanostructures that are ∼100 nm in diameter and 6 μm in length by using a facile hydrothermal process. Then, a unimorph cantilever energy harvester was fabricated by bonding mixed hierarchical PZT nanowires with a polydimethylsiloxane (PDMS) polymer matrix to a brass substrate. The measured open-circuit voltage from this harvester was 2.7 V at its fundamental resonance (25.2 Hz) under a 0.1g root-mean-square (RMS) acceleration input, and the measured power density was 51.8 μW cm–3 with an optimal load resistance of 2 MΩ, which is approximately 8 times larger than that of the commercial BaTiO3 nanoparticle energy harvester on the same scale but driven by a much higher acceleration level.

Construction of hierarchical NiCo2S4 nanowires on 3D biomass carbon for high-performance supercapacitors

One-dimensional/three-dimensional (1D/3D) hierarchical porous network configurations are composed of NiCo2S4 nanowires in-situ grown on biomass carbon (NiCo2S4/3DHC). The 3D biomass carbon (3DHC) with hierarchical micron- to nano-porous structure which is suitable for as a basal growth has been obtained from a pyrolysis active process of wood (Metasequoia). NiCo2S4 nanowires were produced on 3D biomass carbon via a facile hydrothermal method. The characterization and comparison of various properties of NiCo2S4/3DHC have been investigated systematically. A maximum specific capacitance of 765.8 F/g was observed for the NiCo2S4/3DHC electrode at 1 A/g in a 6 M KOH electrolyte solution, while 32.3 F/g for 3DHC at the same condition. The method reported here can be potentially applied to feasible construct 3D electrode configuration for energy storage devices using biomass as main raw materials.

Highly Ordered Hierarchical Pt and PtNi Nanowire Arrays for Enhanced Electrocatalytic Activity toward Methanol Oxidation.

Highly ordered hierarchical Pt and PtNi nanowire arrays were prepared using CdS hierarchical nanowire arrays (HNWAs) as sacrificial templates and demonstrated high electrochemical active surface areas. For the resulting Pt HNWAs sample, the peak current for methanol oxidation at +0.74 V was almost 1 order of magnitude higher than that of Pt solid nanowire arrays prepared in a similar manner but without the use of CdS template, and the addition of a Ni cocatalyst effectively enhanced the tolerance against CO poisoning. The results demonstrated that highly ordered Pt and PtNi HNWAs may be exploited as promising anode catalysts in the application of direct methanol fuel cells.

Highly efficient copper-doped manganese oxide nanorod catalysts derived from CuMnO hierarchical nanowire for catalytic combustion of VOCs

Copper-doped manganese oxide nanorod catalysts with various Cu/Mn molar ratios have been prepared for catalytic combustion of Volatile organic compounds (VOCs). The effects of Cu/Mn ratio and calcination temperatures on catalytic performance were investigated. It turned out that the Cu1Mn1-500 sample exhibited the best catalytic combustion performance, to remove toluene at a temperature of 214 °C over 120 h without a significant decrease in toluene conversion. XRD, SEM, HRTEM, XPS were carried out to explore the physicochemical properties of catalysts, and the results demonstrated that doping copper into manganese oxides can contribute to rich oxygen vacancies, high redox capability, and hence increase the catalytic activity. In addition, both the large surface area and high crystallization of the obtained nanorod catalysts are also helpful for the high activity and stability of these copper-manganese mixed metal oxide catalysts. Furthermore, the presence of water vapor had little inhibition effect on the catalytic activity under the reaction condition.

Preparation of Hierarchical Spinel NiCo2O4 Nanowires for High-Performance Supercapacitors

Hierarchical spinel NiCo2O4 nanowires were synthesized by a facile hydrothermal method followed by an annealing treatment. The prepared NiCo2O4 nanowires presented a hierarchical mesoporous structure. Moreover, the effects of precipitant and solvent on morphologies of NiCo2O4 were researched. The results reveal that the hierarchical mesoporous structured NiCo2O4 exhibited corking supercapacitor performance with a high specific capacitance of 2876 F·g–1 at a current density of 1 A g–1, even increased to 10.0 A g–1, the specific capacitance could still remain 1290 F g–1, what’s more, the capacitance retention reached 84.7% after 500 cycles, which indicates an excellent electrochemical performance. The results demonstrate hierarchical mesoporous NiCo2O4 potential to be a promising supercapacitor electrode materials and inspire furthered research on binary metal oxides as charge storage materials and offer a new route for the large-scale production of high-performance supercapacitor electrode materials.

Electrodeposition based on cyclic voltammograms of hierarchical Pt nanowire arrays: enhanced electrocatalytic activity for methanol oxidation

ABSTRACTHierarchical Pt nanowire arrays are electrodeposited by using cyclic voltammetry on the basis of CdS hierarchical nano-arrays assembled from CdS nanoparticles. The Pt nanowire arrays are found to exhibit a significantly higher electrocatalytic activity, which is attributable to the unique hierarchical structure of Pt nanowires with significantly higher electrochemically active surface areas. The results demonstrate potential of hierarchical Pt nanowire arrays as effective electrocatalysts in direct methanol fuel cells. Importantly, using CdS hierarchical structures as the template, this synthetic strategy, unlike the conventional electrochemical deposition method, allows for the facile preparation of hierarchical Pt nanowire arrays, and is expected to be widely applicable for the deposition of others hierarchical metals and multicomponent alloy arrays.

Facile synthesis of N,O-codoped hard carbon on the kilogram scale for fast capacitive sodium storage

The kilogram-scale preparation of N,O-codoped hierarchical porous hard carbon cuttlefish-like nanowire bundles (NOHPHC) through pyrolysis of Al-based MOFs indicates the excellent sodium-storage performance due to the unique structural advantages. The present work provides inspiration for development of advanced anode materials for practical sodium-ion battery application.

Hierarchical three-dimensional manganese doped cobalt phosphide nanowire decorated nanosheet cluster arrays for high-performance electrochemical pseudocapacitor electrodes.

Ternary metal phosphides with a self-assembled hierarchical nanostructure are promising electrode materials for energy storage and conversion, due to the unique architecture and synergistic effects in bimetallic nanostructures. In this communication, we demonstrate hierarchical Mn-doped cobalt phosphide nanowire decorated nanosheet cluster arrays with robust adhesion on Ni foam (Mn-CoP/NF) as a binder-free electrode for supercapacitors. Such a 3D electrode exhibits boosted areal specific capacitance over that for a single metal counterpart, with the accomplishment of 8.66 F cm-2 capacitance at 1 mA cm-2. Utilizing the Mn-CoP/NF electrode as an anode and an activated carbon (AC) electrode as a cathode, an asymmetric supercapacitor (ASC) of Mn-CoP//AC attains a high area capacitance of 2.05 F cm-2 at 5 mA cm-2 and a high capacitance retention of 88.9% after 4000 cycles. In addition, the assembled ASC shows superior electrochemical performances with a high energy density of 35.21 W h kg-1 at a power density of 193 W kg-1 and of 30.87 W h kg-1 even at 1939 W kg-1.

Centrifugation-assisted preparation of nanoparticle decorated hierarchical nanowire arrays for improved solar cell performance

Considering the fact that large surface areas and fast electron transport properties of photoanodes play an essential role in determining dye sensitized solar cell efficiency. A centrifugation-assisted method was designed to fabricate nanoparticle decorated hierarchical nanowire arrays. The hierarchical nanostructure arrays enable the fast charge transport properties of the photoanode. At the same time, the nanoparticles and the hierarchical nanostructures work together to guarantee the large surface areas of the photoanodes. During the fabrication process, TiO2 hierarchical nanowire arrays were firstly fabricated on fluorine doped tin oxide substrates via a hydrothermal method and then nanoparticles were deposited subsequently in the interval spaces among the neighboring nanostructures. Field-emission scanning electron microscopy and X-ray diffraction were used to characterize the morphology and structure of the obtained products, respectively. The results show that the nanoparticles do deposit in the interval spaces among the hierarchical nanowires forming a hybrid structure composed of anatase and rutile TiO2. The obtained nanoparticle decorated hierarchical nanowire arrays have been successfully applied in dye sensitized solar cells. A power conversion efficiency of 5.52% was achieved with the photoanode film thickness of about 20µm.

Hierarchical Nickel nanowire synthesis using polysorbate 80 as capping agent

Nanomaterials find applications in multiple fields including food and beverages, waste water management, electrical and electronics due to their interesting properties. These properties can be fine-tuned using various synthesis techniques ranging from solid state route to different wet chemical techniques like precipitation, sol-gel, hydrothermal and solvothermal methods Here, we report a simple wet chemical synthesis of nickel nanoparticles using Tween 80 as the capping agent. Scanning electron microscopy (SEM) revealed a hierarchical nanowire- like morphology with thorn like sharp edges while the presence of nickel in the sample was confirmed by energy dispersive spectroscopy (EDS). X-ray diffraction studies ascertained the crystalline nature of nickel nanowires and also the purity of the as-synthesized nanowires. Transmission electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED) analysis of the sample indicated the existence of a small quantity of nickel hydroxide. The magnetic property of the synthesized nickel samples studied using vibrating sample magnetometer (VSM) revealed a high saturation magnetization of ∼43 emug−1. Antibacterial activity studies confirmed that nickel nanowire exhibited an excellent bactericidal activity against both gram- positive and gram- negative bacteria which could be attributed to the morphology of the nickel nanowires.

Hierarchical NiMoO4 nanowire as an anode material for lithium ion batteries

The NiMoO4 samples were synthesized by rheological phase-hydrothermal method. The efforts of different annealed temperatures on the morphologies and electrochemical properties of the final products were systematically investigated. The NiMoO4 samples exhibit the best electrochemical properties with a high reversible capability (640 mAh g−1 at current density of 50 mA g−1) and cycling stability, compared with the other samples. These results indicate that the NiMoO4 samples could be promising electrode materials for lithium ion batteries.

TiO2 nanowire-templated hierarchical nanowire network as water-repelling coating.

Extraordinary water-repelling properties of superhydrophobic surfaces make them novel candidates for a great variety of potential applications. A general approach to achieve superhydrophobicity requires low-energy coating on the surface and roughness on nano- and micrometre scale. However, typical construction of superhydrophobic surfaces with micro-nano structure through top-down fabrication is restricted by sophisticated fabrication techniques and limited choices of substrate materials. Micro-nanoscale topographies templated by conventional microparticles through surface coating may produce large variations in roughness and uncontrollable defects, resulting in poorly controlled surface morphology and wettability. In this work, micro-nanoscale hierarchical nanowire network was fabricated to construct self-cleaning coating using one-dimensional TiO2 nanowires as microscale templates. Hierarchical structure with homogeneous morphology was achieved by branching ZnO nanowires on the TiO2 nanowire backbones through hydrothermal reaction. The hierarchical nanowire network displayed homogeneous micro/nano-topography, in contrast to hierarchical structure templated by traditional microparticles. This hierarchical nanowire network film exhibited high repellency to both water and cell culture medium after functionalization with fluorinated organic molecules. The hierarchical structure templated by TiO2 nanowire coating significantly increased the surface superhydrophobicity compared to vertical ZnO nanowires with nanotopography alone. Our results demonstrated a promising strategy of using nanowires as microscale templates for the rational design of hierarchical coatings with desired superhydrophobicity that can also be applied to various substrate materials.

Electrospinning of hierarchical structure Nd10W22O81 nanowires as high performance lithium storage anode for rechargeable batteries

In this work, hierarchical structure Nd10W22O81 nanowires are successfully prepared by a feasible electro-spinning technique followed by heat treatment. The structure, morphology and electrochemical characteristics of Nd10W22O81 nanowires are investigated and compared with Nd10W22O81 particles fabricated by a high temperature solid state reaction. It can be observed that Nd10W22O81 nanowires display a “nanoparticle-in-nanowire” architecture. For comparison, solid state formed Nd10W22O81 is composed of irregular microsized particles. This hierarchical architecture makes Nd10W22O81 nanowires have higher Li-storage capacity and better rate performance, contributing to the larger ion channels and shorter ion transportation pathways. In addition, an in-situ X-ray diffraction investigation is also operated to study the structural evolution and reaction mechanism during the charge/discharge process. All these evidences indicate that hierarchical structure Nd10W22O81 nanowires could be a potential high capacity anode material for rechargeable lithium-ion batteries.

Facile preparation of branched hierarchical ZnO nanowire arrays with enhanced photocatalytic activity: A photodegradation kinetic model

Branched hierarchical zinc oxide nanowires (BH-ZnO NWs) were fabricated successfully by a facile and rapid synthesis using two-step growth process. Initially, ZnO NWs have been prepared by anodizing zinc foil at room temperature and followed by annealing treatment. Then, the BH- ZnO NWs were grown on the ZnO NWs by a solution based method at very low temperature (31 oC). The BH- ZnO NWs with different aspect ratio were obtained by varying reaction time (0.5, 2, 5, 10 h). Photocatalytic activity of the samples was studied under both UV and visible light. The results indicated that the optimized BH-ZnO NWs (5 h) as a photocatalyst exhibited the highest photoactivity with about 3 times higher than the ZnO NWs under UV light. In addition, it was also determined that photodegradation rate constant (k) for the BH- ZnO NWs surface obeys a linear function with the branch length (l) and their correlation was described by using a proposed kinetic model.

Nanowire-on-Nanowire: All-Nanowire Electronics by On-Demand Selective Integration of Hierarchical Heterogeneous Nanowires

Exploration of the electronics solely composed of bottom-up synthesized nanowires has been largely limited due to the complex multistep integration of diverse nanowires. We report a single-step, selective, direct, and on-demand laser synthesis of a hierarchical heterogeneous nanowire-on-nanowire structure (secondary nanowire on the primary backbone nanowire) without using any conventional photolithography or vacuum deposition. The highly confined temperature rise by laser irradiation on the primary backbone metallic nanowire generates a highly localized nanoscale temperature field and photothermal reaction to selectively grow secondary branch nanowires along the backbone nanowire. As a proof-of-concept for an all-nanowire electronics demonstration, an all-nanowire UV sensor was successfully fabricated without using conventional fabrication processes.

Metallic Aerogels: 3D Printing Hierarchical Silver Nanowire Aerogel with Highly Compressive Resilience and Tensile Elongation through Tunable Poisson's Ratio (Small 38/2017)

Metallic Aerogels: 3D Printing Hierarchical Silver Nanowire Aerogel with Highly Compressive Resilience and Tensile Elongation through Tunable Poisson's Ratio (Small 38/2017)

Selective Thermochemical Growth of Hierarchical ZnO Nanowire Branches on Silver Nanowire Backbone Percolation Network Heaters

The development of hydrothermal growth enabled facile growth of ZnO nanowire over a large area at mild environments, yet its usage in actual electronic devices has been restricted due to poor spatial selectivity in the growth and a difficulty in the integration to other components. We introduce a local thermochemical growth of ZnO nanowire branches on Ag nanowire backbone percolation networks by electrical current induced local resistive heating in liquid environment for easy fabrication of metal–semiconductor hierarchical nanowire structure. Through vacuum filtration transfer and laser ablation process, patterned conductive network composed of ZnO nanoparticle functionalized Ag nanowire percolation network was prepared as a conductive network for localized resistive heating. Upon the application of proper bias voltage, highly localized temperature field was generated in the vicinity of the patterned Ag nanowire network heater to induce the selective growth of ZnO nanowire from the Ag nanowire backbone. As the temperature rise is related to the electrical current flow, ZnO nanowire was selectively synthesized at the area subject to the maximum current density, which was defined by the laser ablation technique. It was further confirmed that the characteristics of grown ZnO nanowires could be controlled by changing the growth condition.

A Delaminated Defect‐Rich ZrO2Hierarchical Nanowire Photocathode for Efficient Photoelectrochemical Hydrogen Evolution

AbstractAn efficient way to combat the energy crisis and the greenhouse gas effect of fossil fuels is the production of hydrogen fuel from solar‐driven water splitting reaction. Here, this study presents a p‐type ZrO2nanoplate‐decorated ZrO2nanowire photocathode with a high photoconversion efficiency that makes it potentially viable for commercial solar H2production. The composition of oxygen vacancy defects, low charge carrier transport property, and high specific surface area of these as‐grown hierarchical nanowires are further improved by an hydrofluoric acid (HF) treatment, which causes partial delamination and produces a thin amorphous ZrO2layer on the surface of the as‐grown nanostructured film. The presence of different types of oxygen vacancies (neutral, singly charged, and doubly charged defects) and their compositional correlation to the Zrx+oxidation states (4 >x> 2) are found to affect the charge transfer process, the p‐type conductivity, and the photocatalytic activity of the ZrO2nanostructured film. The resulting photocathode provides the highest overall photocurrent (−42.3 mA cm−2at 0 V vs reversible hydrogen electrode (RHE)) among all the photocathodes reported to date, and an outstanding 3.1% half‐cell solar‐to‐hydrogen conversion efficiency with a Faradaic efficiency of 97.8%. Even more remarkable is that the majority of the photocurrent (69%) is produced in the visible light region.

Ultralong hydroxyapatite nanowires/collagen scaffolds with hierarchical porous structure, enhanced mechanical properties and excellent cellular attachment

Abstract Hydroxyapatite/collagen (HAP/Col) composite porous scaffolds have been extensively investigated in the field of bone tissue engineering due to their similar chemical composition to that of natural bone and good biocompatibility. However, the relatively poor mechanical properties of the HAP/Col composite porous scaffolds limit their application in bone regeneration. In order to overcome these limitations, the hierarchical porous ultralong hydroxyapatite nanowires (UHANWs)/collagen (Col) composite scaffolds with excellent mechanical properties are synthesized by freeze-drying the suspension containing UHANWs and collagen. Compared with the HAP nanorods (HANRs), the highly flexible UHANWs can interweave with each other to construct a three-dimensional fabric-like structure in the collagen matrix of the UHANWs/Col scaffolds and significantly improve the mechanical properties of the scaffolds. The Young's modulus of the 70 wt% UHANWs/Col scaffold is about 4 times that of the pure collagen scaffold and 63 times that of the 70 wt% HANRs/Col scaffold. More importantly, in the absence of the collagen matrix, the pure UHANWs inorganic porous scaffold can be synthesized and exhibits relative good mechanical properties. However, the HANRs/Col scaffolds with HANRs weight fractions more than 70 wt% are easily cracked during the fabrication process. Furthermore, compared with the pure collagen and 70 wt% HANRs/Col scaffolds, the 70 wt% UHANWs/Col scaffold exhibits a superior biocompatibility and excellent ability to promote cell adhesion and spreading on the surface of the scaffold. In consideration of their outstanding mechanical properties and excellent cellular attachment performance, the as-prepared hierarchical porous UHANWs/Col scaffolds are promising for applications in various biomedical fields such as bone defect repair.