Nanowire Bundles Research Articles

Synthesis of highly oriented WO3 nanowire bundles decorated with Au for gas sensing application

This study demonstrates the synthesis of self-assembled hexagonal WO3 nanowire bundles, with both ordered and random structures in the presence of SO42− ions, by a simple but efficient solvent-thermal method. The as-synthesized products are composed of hierarchical bundles with assembled ultrathin nanowire subunits. The growth and assembly mechanisms, regarding WO3 nanowire bundles, may be elucidated through oriented attachment or Ostwald ripening growth, based on a synergistic effect from both oxalic acid and ethylene glycol in dehydrating WO3·xH2O to WO3 nanocrystals and in controlling segregation behavior, along with high surface areas (18.4 m2 g-1 for ordered structures while 11.6 m2 g-1 disordered ones), which makes WO3 bundles great potential for gas sensing. To further enhance gas sensing, gold nanoparticles were chosen to deposit on the surface of WO3 nanowire bundles by acting with amino groups linked with WO3 bundles in the HAuCl4 solution with further oxidation. The Au-WO3 composites were examined towards various reducing gases, with exemplary sensitivities of (S = 127, 82), (S = 72, 52) towards n-butanol and acetone, respectively. The sensing mechanisms of such WO3 bundle structures are further understood in detail. This work will make the unique WO3 bundle nanostructures highly potential for gas sensing applications.

Porphyrin Nanowire Bundles for Efficient Photoconductivity, Photoemission, and Generation of Singlet Oxygens toward Photodynamic Therapy

Energy released from an accelerated high-energy single/cluster particle triggers solid-state polymerization and crosslinking reactions of porphyrin-based π-conjugated monomers within a nm-scaled 1-...

Effect of Anisotropic Confinement on Electronic Structure and Dynamics of Band Edge Excitons in Inorganic Perovskite Nanowires.

Inorganic lead halide perovskite nanostructures show promise as the active layers in photovoltaics, light emitting diodes, and other optoelectronic devices. They are robust in the presence of oxygen and water, and the electronic structure and dynamics of these nanostructures can be tuned through quantum confinement. Here we create aligned bundles of CsPbBr3 nanowires with widths resulting in quantum confinement of the electronic wave functions and subject them to ultrafast microscopy. We directly image rapid one-dimensional exciton diffusion along the nanowires, and we measure an exciton trap density of roughly one per nanowire. Using transient absorption microscopy, we observe a polarization-dependent splitting of the band edge exciton line, and from the polarized fluorescence of nanowires in solution, we determine that the exciton transition dipole moments are anisotropic in strength. Our observations are consistent with a model in which splitting is driven by shape anisotropy in conjunction with long-range exchange.

Mo-doped WO3 nanowires for adsorbing methylene blue dye from wastewater

Doping tungsten oxide with other metals is a promising approach for obtaining improved properties as compared with its undoped counterpart. Here, the effect of molybdenum doping on the morphology, crystalline structure, and adsorption properties of nanostructured WO3 was investigated. Undoped and Mo-doped hexagonal WO3 (h-WO3) nanowire bundles were synthesized by hydrothermal method. The samples were characterized by X-ray powder diffraction, transmission electron microscopy, scanning transmission electron microscopy, selected-area electron diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Raman spectroscopy. The surface areas of the samples were evaluated by N2 adsorption–desorption isotherm, and their adsorption properties were evaluated based on their ability to adsorb cationic dye methylene blue (MB) in aqueous solution. Upon the addition of molybdenum, the morphology of the h-WO3 nanowire changes from large bundles to narrow bundles with a higher number of isolated thin nanowires. Mo doping also has changed the crystalline structure, porosity, and surface area of the bundled h-WO3 nanowires. Interestingly, Mo-doped h-WO3 nanowire bundles exhibit an enhanced and faster MB uptake, thus implying that Mo-doping WO3 can be an effective strategy to improve the adsorption properties, thereby adding value in developing alternative adsorption-based methods for wastewater treatment.

Quantum Confined Tomonaga-Luttinger Liquid in Mo6Se6 Nanowires Converted from an Epitaxial MoSe2 Monolayer.

Confining interacting particles in one-dimension (1D) changes the electronic behavior of the system fundamentally, which has been studied extensively in the past. Examples of 1D metallic systems include carbon nanotubes, quasi-1D organic conductors, metal chains, and domain boundary defects in monolayer thick transition-metal dichalcogenides such as MoSe2. Here single and bundles of Mo6Se6 nanowires were fabricated through annealing a MoSe2 monolayer grown by molecular-beam epitaxy on graphene. Conversion from two-dimensional (2D) MoSe2 film to 1D Mo6Se6 nanowire is reversible. Mo6Se6 nanowires form preferentially at the Se-terminated zigzag edges of MoSe2 and stitch to it via two distinct atomic configurations. The Mo6Se6 wire is metallic and its length is tunable, which represents one of few 1D systems that exhibit properties pertinent to quantum confined Tomonaga-Luttinger liquid, as evidenced by scanning tunneling microscopic and spectroscopic studies.

Difference in the interaction of nano-diameter rod and tubular particles with a disclination line in a nematic liquid crystal.

In the presence of a disclination line, inclusions within an aligned nematic liquid crystal (LC) are first attracted and ultimately trapped in it. The kind of orientational distortion created by the inclusions is fundamental in determining the trapping. In the present work, we observe differences in the trapping behaviour, onto a ½ defect line in a nematic LC, of two types of particles both elongated but different in their actual geometry. Even if both types have cylindrical shape, aggregates of Mo6S2I8 nanowires (rod-like shape) and multiwall carbon nanotubes (tubular shape, i.e. hollow) trap differently although still due to deformations induced in the LC director field. Attractive forces are stronger on elongated bundles of nanowires than on similarly sized bundles of multi-wall carbon nanotubes. The reason is the difference in the attraction forces originating from different types of distortions of the LCs. The hollow and the full cylinders are not homotopically equivalent and this inequivalence holds also for the liquid crystal around them. The nanowires induce defects in the LC close-by their surfaces as shown for microrods, topologically equivalent to spheres. In contrast, multi-wall carbon nanotubes, being hollow, do not form defects close to their ends. However, the tubes are strongly bent and the strong planar anchoring of LC at the surface induces deformation in the LC enabling attraction forces with the defect line. HiPco single wall carbon nanotubes could not be trapped because their bundles looked much straighter and smaller than the ones of MWCNTs and thus neither defects nor standard strong deformations are expected. In conclusion, even if the shape of both types of particles is cylindrical, the topological difference between rods and tubes has profound consequences on the physical behaviour and on the presence and type of defect-mediated nematic attraction forces.

Solar-driven plasmonic tungsten oxides as catalyst enhancing ethanol dehydration for highly selective ethylene production

Non-metallic plasmonic materials, as alternatives to costly noble metals, have drawn numerous attention owning to their unique localized surface plasmon resonance (LSPR) effect. Herein, we report non-metallic plasmonic tungsten oxide (WO3−x) nanowire bundles with abundant oxygen vacancy (OVs) that gives efficient activity for ethylene production from ethanol dehydration under full spectrum light irradiation. A remarkable ethylene generation rate of 16.9 mmol g−1 h−1 was achieved with high selectivity (94.9 %) over the WO3−x-5 nanowires with maximum oxygen vacancies, which was 16 times higher than 1.0 mmol g−1 h−1 (selectivity of 90.5 %) of WO3−x-20 nanoplates with low oxygen vacancies. Such impressive performance is ascribed to the synergistic effect of plasmonic hot electrons and photothermal effect. This work is expected to provide new insights on photo-induced ethanol dehydration for highly selective ethylene production.

Synthesis of Se nanowires at room temperature using selenourea as Se source

High-yield Se nanowires were synthesized in water at room temperature using selenourea as the only reactant. We have investigated the influence of the solvents and surfactants on the morphologies of Se products. When water/CH3COOH (HAc) was used as solvent, bundles of Se nanowires were prepared. However, when different amines [octylamine, ethylenediamine (EDA), butylamine] were used, we only got Se particles with bad morphology. When SDS was used as surfactant in pure water system, agglomerated nanowires were prepared, and when CTAB was used as surfactant in pure water system, agglomerated Se particles were gotten. Se nanowires and particles prepared in different conditions were characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray.

Novel ZnFe2O4/WO3, a highly efficient visible-light photocatalytic system operated by a Z-scheme mechanism

Dark red ZnFe2O4 (ZFO) nanoparticles (NPs) of ˜9 nm size and pale yellow WO3 nanowire bundles (NWBs) with high porosity were prepared by hydrothermal reactions, respectively, and coupled to form novel ZFO/WO3 heterojunctions. Tiny ZFO NPs and highly porous WO3 NWBs successfully formed intimate heterojunctions, facilitating charge transport at their interfaces. Under visible-light, ZFO/WO3 composites demonstrated outstanding catalytic activities for decomposing isopropyl alcohol (IPA) in the gas phase and salicylic acid (SA) in aqueous solution. In particular, the amount of CO2 evolved in 2 h during decomposition of IPA was 24.7 ppmv, which was 3.0 times that produced using typical nitrogen-doped TiO2 (N-TiO2). Moreover, its degradation rate constant of SA in the presence of ZFO/WO3 was ˜7 times that of N-TiO2. It was determined that •OH and •O2- radicals were the major active species responsible for oxidation reactions, suggesting that the photocatalytic reactions of ZFO/WO3 occurred via Z-scheme mechanism.

Selective growth of metal-free silicon nanowire mat by chemical vapor deposition on hexagonal boron nitride film

The one-dimensional form of silicon (Si) has been attracting significant scientific and industrial interest again in the field of Li-ion batteries as well as electronic devices, offering higher reversible capacity than carbon materials in an anode. In this work, a new method to grow a uniform Si nanowire mat without metallic nanoparticles was developed, and the growth conditions and conformational properties were also characterized. It is suggested that Si nanowire could be grown by the charge transfer through the hexagonal boron nitride (h-BN) film from the Cu foil as the previously reported graphene growth on the h-BN film on Cu. Web-like bundles of Si nanowires or nanoclusters could be selectively grown on this h-BN/Cu substrate by controlling the substrate temperature during Si deposition. The morphology and chemical composition of the Si nanowire mats, therefore, were systematically characterized using scanning tunneling microscopy, atomic force microscopy, and X-ray photoemission spectroscopy. When decoupled from the metal by a thin h-BN film during the growth, this pristine Si nanowire mat can provide promising technical breakthroughs for anode applications in Li-ion batteries.

Solution synthesis of helical gold nanowire bundles

Helical nanostructures are important nanoscale building blocks. While only a few methods are available for synthesizing helical metal nanostructures, those involving collective twisting behaviour are even fewer. Here, we report a solution synthesis of Au nanowire bundles with hierarchical helical constructions. Ultrathin nanowires with diameters of only about 10 nm formed huge ribbon bundles that have a width of 0.5-1 μm and thickness of a few hundreds of nanometres. These bundles extended to hundreds of micrometres and curled into helices. Mechanism studies revealed that the white floccules formed by Au(i) and a thiol ligand are of critical importance for both the nanowire growth and helical bundle formation. The nanowire growth took place in the floccules following the previously reported active surface growth mode, and the bundle formation was due to the splitting of the active surface. Most importantly, the floccules assisted the strain-induced curling process that yielded helices. As the length of the bundles keeps increasing and they break out from the surrounding floccules, they would have to pass through the pores of the floccules. The imbalanced squeezing at the pore caused the bundles to curl into helices.

Mixed transition metal oxide nanowire arrays enabling hybrid capacitor performance enhancement

Herein, we report MnO2@NiCo2O4 nanowire bundles grown on Ni foam by a facile hydrothermal route. The as-prepared products exhibit high areal capacitance of 452.1 C g−1 at 10 A g−1 and 88.6% of initial capacitance after 10 000 cycles.

Particularities of trichloroethylene photocatalytic degradation over crystalline RbLaTa2O7 nanowire bundles grown by solid-state synthesis route

This is the first report on synthesis and photocatalytic activity for trichloroethylene (TCE) degradation under simulated solar light over RbLaTa2O7 layered perovskites with predominant nanowire or platelet morphologies. SEM images witnessed that the one step thermal treatment at 1200 °C lead to formation of RbLaTa2O7 nanowires with diameter of 80–320 nm and several microns in length associated in bundles and sharp-edged, merged platelets (minor phase). The two-step annealing at 950 °C and 1200 °C resulted in decrease of wires bundle population and increase in that of platelets merged in facetted particles. The RbLaTa2O7 nanowires are made of by well-aligned atomic rows with preferred orientation toward the c-axis, relatively free of defect. High density of hydroxyl groups on the sample calcined in mild conditions (RbLaTa_01) favors the photo mineralization of TCE. In contrast, the activity of RbLaTa_02 annealed in harsh conditions (950 and 1200 °C), poor in surface hydroxyl groups, remained modest. The weak surface basicity directed the reaction mainly to generation of intermediate chlorinated compounds. Pd and Au were supported on RbLaTa2O7 perovskites as an alternative strategy to boost the removal of chlorinated pollutants by combining photocatalytic (mineralization) and catalytic (hydrodechlorination, HDC) processes. The mineralization of TCE to Cl− was drastically hindered in presence of methanol due to quenching of ⋅OH radicals by alcohol. The results suggested that the density of RbLaTa2O7 surface hydroxyl groups is essential for photo mineralization of TCE whereas the surface carbonate is beneficial for the formation of intermediate chlorinated product.

Dental enamel-mimetic large-sized multi-scale ordered architecture built by a well controlled bottom-up strategy

Tooth enamel possesses excellent mechanical properties owing to its multi-scale highly ordered architecture. To develop tooth enamel-mimetic structural materials (EMSMs) is of great significance for understanding the important role of ordered hydroxyapatite (HAP) nanocrystals in tooth enamel and exploring high-performance materials. However, it is still a great challenge to mimic the unique multi-scale ordered architecture of the natural tooth enamel. Herein, inspired by the multi-scale structure and self-assembly of the tooth enamel, we have developed a novel bottom-up step-by-step assembly strategy to build the EMSMs based on ultralong HAP nanowires, and achieved the multi-scale (from nano- to micro- to macro-scale) highly ordered HAP nanowire structure control. In this work, ultralong HAP nanowires are assembled in sequence into highly ordered HAP nanowire bundles, aligned HAP microfibers, and three-dimensional (3-D) highly ordered HAP nanowire bulk, which perfectly imitate the structure and self-assembly of the tooth enamel. This novel method is suitable to fabricate the EMSMs with arbitrary sizes and well-designed shapes, which are promising for various applications in the biomedical fields such as hard tissue defect repair.

Nanowires in Energy Storage Devices: Structures, Synthesis, and Applications

AbstractAccompanied by the development and utilization of renewable energy sources, efficient energy storage has become a key topic. Electrochemical energy storage devices are considered to be one of the most practical energy storage devices capable of converting and storing electrical energy generated by renewable resources, which are also used as the power source of electric vehicles and portable electronic devices. The ultimate goals of electrochemical energy storage devices are long lifespan, high safety, high power, and high energy density. To achieve the above goals, researchers have attempted to use various nanomaterials to improve electrochemical performance. Among these, 1D materials play a critical role. This review classifies nanowires according to morphologies (simple nanowires, core–shell/coated nanowires, hierarchical/heterostructured nanowires, porous/mesoporous nanowires, hollow structures) and combined forms (nanowire arrays, nanowire networks, nanowire bundles) and introduces their characteristics and corresponding synthetic methods. The characteristics and advantages of nanowires in lithium‐ion, sodium‐ion and zinc‐ion batteries, and supercapacitors, along with in situ characterization of nanowire electrode are reflected in the application examples. In the summary and outlook section, some comments are presented to provide directions for further exploring nanowire based electrochemical energy storage in the future.

Mo2C@NC nanowire bundle for efficient electrocatalytic hydrogen evolution

We demonstrate a novel route for the shape-controlled synthesis of inorganic-organic hybrid nanowire bundle of Mo2C and N-doped carbon (Mo2C@NC) for the electrochemical hydrogen evolution reaction (HER) in acidic and alkaline medium. The synthetic procedure involves the facile complexation of Mo precursor, molybdate, with cationic polymer, poly (diallyldimethylammonium chloride) (PDDA) and the subsequent carburization at 800 °C under optimized condition. The Mo2C@NC nanowire bundle has an average diameter of 75 nm and length of 2.5–4 μm. It has > 67% pyridinic nitrogen and the Mo2C nanowires are coated with N-doped carbon of 2–5 nm thickness. The annealing temperature has large control over the morphology and chemical composition. The electrocatalytic activity of Mo2C@NC is examined in acidic and alkaline solution. The benchmark current density of 10 mA/cm2 in acidic and alkaline pH at overpotential of 135 and 121 mV, respectively. Tafel slope of 61 and 56 mV/dec was obtained in acidic and alkaline pH, respectively. The electrocatalytic HER involves Volmer-Heyrovsky mechanism. The hybrid material has outstanding durability in acidic pH and it retains its initial activity even after 1000 extensive repeated potential cycles. The post-HER analysis reveals that the integrity of Mo2C@NC does not change in acidic pH. The superior performance can be explained by considering the surface morphology of Mo2C and the synergistic effect between the carbide catalyst and N-doped carbon.

An efficient and novel FDTD method based performance investigation in high-speed current-mode signaling SWCNT bundle interconnect

Carbon nanotube (CNT) has emerged as the most extensively researched area in nanoscience and amongst the frontrunners in co-triggering the nanotechnology revolution. Single-wall CNT (SWCNT) bundle is a part of CNT family and has been proposed as the future nano-wires in integrated circuits. The present paper analyzes the performance of SWCNT bundle interconnect with high-speed current-mode signaling (CMS) scheme using efficient finite-difference time-domain (FDTD) method. For the first time, FDTD based method is explored for modeling CMS SWCNT bundle interconnect incorporating practical CMOS driver gate. The CMOS gate is characterized by nth power-law model. The stability of FDTD method is ascertained by Courant condition. The proposed FDTD based method is efficient and can be used for performance analyses of future nano-wire SWCNT bundle as well as conventional copper interconnects. At the same time, this method is applicable for both traditional full-voltage swing voltage-mode signaling (VMS) and remarkable low-voltage swing CMS schemes. The various analyses in the paper reveal that CMS SWCNT bundle interconnect has higher edge over CMS copper interconnect in terms of smaller delay, lesser crosstalk induced delay and noise. The proposed analytical FDTD based method is validated using Tanner-SPICE EDA simulation tool. The maximum error between the FDTD and SPICE for the transient response in CMS SWCNT bundle interconnect for 32 nm technology node is within 3%.

Synthesis of Chevrel phase $$(\hbox {Cu}_{1.8}\hbox {Mo}_{6}\hbox {S}_{8})$$ ( Cu 1.8 Mo 6 S 8 ) in composite with molybdenum carbide for hydrogen evolution reactions

Sustainable hydrogen generation from water electrolysis using renewable energy sources is the most promising pathway for future energy and hydrogen economy. Here, the Chevrel phase $$(\hbox {Cu}_{1.8}\hbox {Mo}_{6}\hbox {S}_{8})$$ was synthesized in composite with $$\hbox {Mo}_{2}\hbox {C}$$ and good hydrogen evolution activity in acidic media has been demonstrated. Bundles of nanowires were formed in the templated synthesis route. The composites were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and elemental analysis. Detailed electrochemical analysis reveals that MCS-Cu50 composite exhibits higher hydrogen evolution reaction (HER) activity with $$71.4\,\hbox {mA}\,\mathrm{cm}^{-2}$$ current density at an overpotential of 400 mV. It requires 250 mV overpotential to produce $$10\,\hbox {mA}\,\mathrm{cm}^{-2}$$ current density for HER.

Ni-Doped Cobalt Phosphite, Co11(HPO3)8(OH)6, with Different Morphologies Grown on Ni Foam Hydro(solvo)thermally for High-Performance Supercapacitor.

Ni-doped Co11(HPO3)8(OH)6 with different morphologies was directly grown on Ni foam hydro(solvo)thermally under different synthetic conditions. The optimum condition is solvothermal reaction for 6 h in an ethanol/water (EW) mixed solution, the molar ratio of NaH2PO2/Co(NO3)2 being 0.5:0.1, and the obtained S0.5-6 h-EW shows three-dimensional (3D) porous nanowire bundles. Whereas in the water-only solution, microrods are obtained, suggesting that the nanowires in bundles are aggregated together via the lateral (400) direction. Long reaction time and low molar ratio of reactants are all beneficial for the lateral growth of the nanowires, and the possible formation mechanism is proposed. All the obtained Ni-doped Co11(HPO3)8(OH)6/Ni foam samples are directly used as supercapacitor electrodes, and S0.5-6 h-EW shows the best electrochemical performance with a specific capacity of 159 mAh g-1 at 0.5 A g-1, which is close to the theoretical value of 212 mAh g-1 for Co11(HPO3)8(OH)6, and it is the largest reported value so far. The excellent capacitive behavior of S0.5-6 h-EW is ascribed to the 3D porous nanowire bundles directly grown on a Ni foam collector without an additive and a binder, as well as to the doping of Ni into the cobalt phosphite. The S0.5-6 h-EW//activated carbon asymmetrical supercapacitor shows a maximum energy density of 58.7 Wh kg-1 at a power density of 532 W kg-1 and good cycling stability with the capacity retention of 90.5% after 10 000 charging-discharging cycles at 5.5 A g-1.

Material-Versatile Ultrabroadband Light Absorber with Self-Aggregated Multiscale Funnel Structures.

Broadband light absorbers are essential components for a variety of applications, including energy harvesting and optoelectronic devices. Thus, the development of a versatile absorbing structure that is applicable in various operating environments is required. In this study, a material-versatile ultrabroadband absorber consisting of metal-coated self-aggregated Al2O3 nanowire bundles with multiscale funnel structures is fabricated. A high absorptance of ∼0.9 over the AM 1.5G spectrum (300-2500 nm) is realized for absorbers with a range of metal coatings, including Al, W, and titanium nitride (TiN). We demonstrate that the plasmonic nanofocusing and index-matching effects of the funnel structure result in strong ultrabroadband absorption for the various metal coatings, even though the coating materials have different optical properties. As an example of applicability in an operating environment, in the evaluation of the thermal-oxidation resistance, the Al-coated solar absorber exhibits superior performance to those coated with refractory materials such as W and TiN because of the protective alumina layer formed on the Al surface.