Ultralong Nanowires Research Articles

Multifunctional Photocatalytic Filter Paper Based on Ultralong Nanowires of the Calcium-Alendronate Complex for High-Performance Water Purification.

Semiconductor photocatalysts and membrane separation technology have been widely used in the field of water treatment. Usually, the particles of traditional semiconductor photocatalysts are easy to aggregate, difficult to separate from the liquid phase after photocatalysis, and may even cause secondary pollution. On the other hand, the membrane separation technology is also facing the problem of sharp decreases in removal efficiency and water flux caused by the membrane fouling. However, it is an attractive and promising solution to combine two technologies of photocatalysis and membrane separation for high-performance water treatment. In this work, we have developed the calcium oleate precursor solvothermal method to synthesize ultralong nanowires (UNWs) of Ca-alendronate (Ca-ALN) complex for the first time. Experimental results and data analysis indicate that the as-prepared Ca-ALN ultralong nanowires are an n-type semiconductor with an energy band gap of 3.41 eV. A new type of multifunctional photocatalytic filter paper has been developed based on ultralong nanowires of Ca-ALN complex (Ca-ALN-UNWs) and cellulose fibers (CFs). The as-prepared Ca-ALN-UNW/CF photocatalytic filter paper exhibits multifunctions of photocatalysis, adsorption, and filtration, which can be used for high-performance treatment of the wastewater containing various pollutants such as heavy-metal ions, dyes, antibiotics, and bacteria. The active oxygen species produced by the Ca-ALN-UNW/CF photocatalytic filter paper under light illumination are determined by electron spin resonance, and the energy band gap and photoelectric properties of the material are tested by ultraviolet-visible diffuse reflectance spectroscopy and electrochemical workstation. The pure water flux of the Ca-ALN-UNW/CF photocatalytic filter paper is very high, which can reach 2230.5 L m-2 h-1 under a working pressure of 0.1 MPa. The Ca-ALN-UNW/CF photocatalytic filter paper is promising for various applications such as highly efficient water purification and in the biomedical field.

A flexible self-supporting ultralong MnO2 nanowires-expanded graphite nanosheets current collector with enhanced catalytic reaction kinetics for high-loading lithium-sulfur batteries

Owing to the shuttle effect of lithium polysulfides (LiPSs), poor conductivity and low loading mass of active sulfur, and its large volume expansion during cycling, these shortcomings still restrict practical application of high performance lithium-sulfur (Li-S) batteries. Herein, a stable flexible current collector, composed of ultralong MnO 2 nanowires and expanded graphite nanosheets (MnO 2 NW/EG) with high electronic conductivity, is combined with Li 2 S 6 to serve as a self-supporting cathode in Li-S batteries, in which the maximum loading mass of sulfur can be regulated to 7 mg cm −2 , the ultralong MnO 2 nanowires has the ability to accelerate the adsorption and catalytic conversion of LiPSs through the chemical action of the polar active surface and the good mechanical flexibility caused by the introduction of ultralong nanowires and nanosheets can buffer the large volume expansion of sulfur during charging/discharging. Moreover, Li-S batteries with MnO 2 NW/EG current collector still maintain a high capacity of 538 mAh g −1 after 500 cycles at 1 C and the capacity decay is only 1.2 mAh g −1 per cycle, even when the sulfur loading is 7 mg cm −2 , the capacity can be as high as 2.5 mAh cm −2 , indicating a practical application ability. • A stable flexible current collector is applied in Li-S batteries. • The loading mass of sulfur can be regulated to 7 mg cm −2 • The MnO 2 nanowires can accelerate the adsorption and catalytic conversion of LiPSs. • The cathode with high sulfur loading mass exhibits excellent cyclic stability.

Ultra-long silver nanowires prepared via hydrothermal synthesis enable efficient transparent heaters.

Ultra-long silver nanowires (AgNWs) with an aspect ratio of >2000 were prepared by the hydrothermal synthesis method. The influence of reaction time (4-32 h), reaction temperature (150-180 °C), polyvinylpyrrolidone (PVP) molecular weight (10 000-1 300 000 g mol-1), PVP concentration (50-125 mM), glucose concentration (5.6-22.4 mM) and CuCl2 concentration (2-20 μM) on the AgNW length was investigated systematically. The optimum conditions provided nanowires with an average diameter of 207 nm, an average length of 234 μm and a maximum length of 397 μm. Finally, a AgNW electrode was prepared on a glass substrate and used in transparent heater application. The transparent heater enabled outstanding heat-generating properties, reaching >200 °C within 70 s with an applied voltage of 5 V. Our results demonstrate how increasing the aspect ratio of ultra-long AgNWs is beneficial for both optical and electronic applications in terms of increased transmission and a more efficient Joule effect in the heater application. In addition, our results show that AgNWs with different lengths can be simply obtained by tuning synthesis parameters.

Highly conductive thermoresponsive silver nanowire PNIPAM nanocomposite for reversible electrical switch.

Highly conductive nanocomposite hydrogels have been challenging to produce due to their high water volumes inhibiting the incorporation of an essential amount of conductive nanofillers. Furthermore, the most common fillers used, typically for easy integration, display small aspect ratios. Thus, the formation of interparticle pathways for electronic travel is limited, resulting in low conductivities. Here, we introduce ultralong silver nanowires (ULAgNWs) into a thermoresponsive, volume changing PNIPAM gel to form a nanocomposite that shows switchable electronic performance. The produced nanocomposite surpasses other PNIPAM nanocomposites by expressing the largest electrical switch ratio and the highest peak conductivity. The PNIPAM matrix possesses an interconnected microporous structure that offers a spacious network for the dispersion of nanowires while still maintaining a high volume switch ratio and excellent elastic behavior under extreme compression cycles (98% compression). The ULAgNWs significantly enhance the probability of more numerous connections forming during shrinking cycles. The high swellability displayed by the PNIPAM gel provides the ability to separate the embedded nanowires by many lengths. Together, they form a nanocomposite that can thermo-modulate its electrical properties. Moreover, the conductive PNIPAM maintains the electrical switch of 4.3-4.4 orders of magnitude with thermo-responsive cycles. Because of their high electrical conductivity and outstanding elastic behavior, these stimuli-responsive nanocomposite hydrogels may expand the prospects for conductive hydrogel applications and provide greater performance in their applications.

Pearl necklace-like CoMn-based nanostructures derived from metal-organic frames for enhanced electromagnetic wave absorption

Metal-organic frames derived magnetic nanostructures have potential applications in various fields. However, the magnetic particles in the derivatives are frequently agglomerated, limiting their physicochemical properties. Herein, we cross CoZn-MOF particles through ultra-long MnO2 nanowires (MnO2@CoZn-MOF) as precursor for high-performance functional materials. After the carbonization of the MnO2@CoZn-MOF, MnO2 nanowires were transformed into MnO nanowires coated with N-doped carbon layer (MnO@CN), while the CoZn-MOFs were converted into N-doped carbon polyhedron particles encapsulated with Mn3Co7 alloy nanoparticles (Mn3Co7@CN), leading to the formation of hierarchically pearl necklace-like nanostructure (CoMn@CN). The magnetic Mn3Co7@CN nanoparticles are separated uniformly along one-dimensional MnO@CN nanowires, and thus the self-agglomeration of magnetic nanoparticles is avoided efficiently. As a result, the CoMn@CN exhibits excellent electromagnetic wave absorption property with an effective absorption bandwidth of 5.24 GHz as the matching thickness is only 2.0 mm. Experimental results and theory calculations indicate that the improved conductive loss and dielectric relaxation loss caused by abundant heterointerfaces and the electronic interaction between Co and Mn atoms are responsible for the excellent electromagnetic wave absorption performance. Our strategy provides an efficient way for the synthesis of high-performance MOFs-derived nanostructures.

Graphene Oxide-Assisted Growth of Ultralong and Soft Single-Crystalline NaCl Ionic Nanowires for Potential Optical Nanodevices

Graphene Oxide-Assisted Growth of Ultralong and Soft Single-Crystalline NaCl Ionic Nanowires for Potential Optical Nanodevices

Highly stable Pt3Ni ultralong nanowires tailored with trace Mo for the ethanol oxidation

Highly stable Pt3Ni ultralong nanowires tailored with trace Mo for the ethanol oxidation

An ultralong hydroxyapatite nanowire aerogel for rapid hemostasis and wound healing

Rapid hemostasis and wound healing for emergency trauma is the key to ensure the survival of patients with massive hemorrhage. However, it is still a challenge to develop hemostatic materials with both excellent hemostatic activity and wound healing function. Herein, we propose to fabricate an inorganic hemostatic aerogel mainly based on biocompatible inorganic ultralong hydroxyapatite (HAP) nanowires with polyvinyl alcohol (PVA) as organic binder, and the hemostatic aerogel is prepared by using freeze-drying technology to construct three-dimensional (3D) porous structure, which possesses good plasticity and flexibility. When the content of ultralong HAP nanowires reaches 80 wt%, the W-8HAP-2PVA aerogel (aerogel consists of 80 wt% ultralong HAP nanowires and 20 wt% PVA) exhibits super-hydrophilicity/super-hematophilicity, and its in vitro blood clotting index is only 3.81 ± 0.71 %, which is much lower than that of medical gauze. When applied in hemostasis of rat liver and rabbit femoral artery, the hemostatic time and blood loss amount of the W-8HAP-2PVA aerogel are 26.59 ± 7.46 s, 0.18 ± 0.05 g and 174.00 ± 16.57 s, 2.18 ± 1.56 g, respectively. Benefiting from its excellent hydrophilicity and high porosity structure, W-8HAP-2PVA aerogel can quickly absorb water from blood to concentrate blood cells and platelets and accelerate hemostasis. Notably, it shows good hemocompatibility and cytocompatibility, and is able to promote skin wound healing. Hence, W-8HAP-2PVA aerogel has great potential in rapid hemostasis and wound healing for clinical settings.

Free-standing 3D Co3O4@NF micro-flowers composed of porous ultra-long nanowires as an advanced cathode material for supercapacitor

The development of smart structured cathode materials for supercapacitors (SCs) has sparked tremendous interest. However, the appropriate design to achieve high capacitance and energy density-based cathode materials remains a major problem for energy storage systems. This article describes the effective synthesis of self-supported 3D micro-flowers composed of ultrathin nanowires array of Co3O4 on Ni foam (NF) using hydrothermal conditions (Co3O4@NF). The mesoporous Co3O4@NF with a high surface area, providing a rich active state for the Faraday redox reaction and increasing the diffusion rate of the electrolyte ions. The optimized Co3O4@NF-16h electrode exhibited supreme electrochemical performance by delivering a high specific capacitance of 1878, (1127) and 1200 (720 C g−1) F g−1 at 1.0 and 20 A g−1, respectively. The Co3O4@NF electrode retained good capacitance stability of 91% over 10000 cycles at 20 A g−1 with excellent rate-performance of 67% at 20 folded high current values. The obtained results for the Co3O4@NF electrode are presented the enhanced pseudocapacitive performance, indicating the substantial potential for high-performance supercapacitor applications.

Ultrathin PtMo-CeOx hybrid nanowire assemblies as high-performance multifunctional catalysts for methanol oxidation, oxygen reduction and hydrogen oxidation

Although Pt-based alloy catalysts have been considered promising candidates for fuel cell applications, constructing highly efficient, multifunctional Pt-based catalysts that simultaneously boost the three key reactions (MOR, ORR and HOR) in proton exchange membrane fuel cells (PEMFCs) remains a huge challenge. Herein, PtMo-CeOx hybrids with interesting ultrathin and ultralong nanowire assemblies (NAs) structure are synthesized by a one-pot solvothermal method without templates. The PtMo-CeOx-NAs catalyst exhibits 5.2-fold, 6.9-fold and 2.4-fold higher mass activity than commercial Pt/C towards the MOR, ORR and HOR simultaneously and shows excellent durability and CO poisoning tolerance. Detailed experiments reveal that the enhancement should be due to strain and ligand effects. Most impressively, when PtMo-CeOx-NAs membrane electrode assemblies (MEAs) fabricated by a catalyst-coated method are used both as the anode and cathode in PEMFCs, the performance of fuel cells is dramatically boosted compared to those with Pt/C.

Enhancing Electrocatalytic N2 Conversion to NH3 by MnO2 Ultralong Nanowires with Oxygen Vacancies

Background: At present, industrial synthesis of NH3 mainly relies on the Haber-Bosch process, which is characterized by harsh reaction conditions and high energy consumption. Electrochemical nitrogen reduction is considered to be a mild and sustainable alternative method for producing NH3, but efficient electrocatalyst under ambient conditions is the prerequisite for NH3 production. Objective: To demonstrate that CP@MnO2 ultralong nanowires are a highly-efficient electrocatalyst for N2 reduction reaction (NRR) under ambient conditions. Methods: The α-phase MnO2 synthesized by one-step hydrothermal method has an ultralong nanowires structure and oxygen vacancy defects. The catalysts were characterized by XRD, TEM, XPS, etc. The produced NH3 was estimated by indophenol blue method by UV-vis absorption spectra. Results: Such catalyst attains high Faradaic efficiency (FE) of 8.8% and a large NH3 yield of 1.13×10−10 mol cm−2 s−1 at −0.7 V versus reversible hydrogen electrode in 0.1 M Na2SO4. In addition, the catalyst also shows high electrochemical stability and selectivity for NH3 formation. Conclusion: MnO2 ultralong nanowires can expose higher density of active sites and the spontaneously formed oxygen vacancies can manipulate the electronic structure of manganese oxides and provide coordination unsaturation sites (CUS) to enhance the adsorption of N2, which is the main reason for the high activity of the catalyst.

Magnetic Properties of the Densely Packed Ultra-Long Ni Nanowires Encapsulated in Alumina Membrane.

High-quality and compact arrays of Ni nanowires with a high ratio (up to 700) were obtained by DC electrochemical deposition into porous anodic alumina membranes with a distance between pores equal to 105 nm. The nanowire arrays were examined using scanning electron microscopy, X-ray diffraction analysis and vibration magnetometry at 300 K and 4.2 K. Microscopic and X-ray diffraction results showed that Ni nanowires are homogeneous, with smooth walls and mostly single-crystalline materials with a 220-oriented growth direction. The magnetic properties of the samples (coercivity and squareness) depend more on the length of the nanowires and the packing factor (the volume fraction of the nanowires in the membrane). It is shown that the dipolar interaction changes the demagnetizing field during a reversal magnetization of the Ni nanowires, and the general effective field of magnetostatic uniaxial shape anisotropy. The effect of magnetostatic interaction between ultra-long nanowires (with an aspect ratio of >500) in samples with a packing factor of ≥37% leads to a reversal magnetization state, in which a “curling”-type model of nanowire behavior is realized.

Compact Biomimetic Hair Sensors Based on Single Silicon Nanowires for Ultrafast and Highly-Sensitive Airflow Detection.

Wearable sensors that can mimic functionalities of human bodies have attracted intense recent attention. However, research on wearable airflow sensors is still lagging behind. Herein, we report a biomimetic hair sensor based on a single ultralong silicon nanowire (SiNW-BHS) for airflow detection. In our device, the SiNW can provide both mechanical and electrical responses in airflow, which enables a simple and compact design. The SiNW-BHSs can detect airflow with a low detection limit (<0.15 m/s) and a record-high response speed (response time <40 ms). The compact design of the SiNW-BHSs also enables easy integration of an array of devices onto a flexible substrate to mimic human skin to provide comprehensive airflow information including wind speed, incident position, incident angle, and so forth. This work provides novel-designed BHSs for ultrafast and highly sensitive airflow detection, showing great potential for applications such as e-skins, wearable electronics, and robotics.

Ultralong PtPd Alloyed Nanowires Anchored on Graphene for Efficient Methanol Oxidation Reaction.

The rational synthesis of Pt-based alloyed nanowires still remains a great challenge because of the different reduction potentials between Pt and another metal and the intrinsic feature of isotropic growth in face-centered cubic (fcc) structured Pt. In this work, PtPd alloyed nanowires with ultrahigh aspect ratio anchored on graphene (PtPd NWs/graphene) were synthesized by a facile solvothermal method without the use of any templates or surfactants. Due to the integration of ultralong PtPd nanowires and stable graphene support, PtPd NWs/graphene exhibited outstanding electrochemical activity toward methanol oxidation reaction (MOR) in comparison with pure Pt NWs/graphene and commercial Pt/C catalysts. Meanwhile, PtPd NWs/graphene had a much higher current density than Pt NWs/graphene and commercial Pt/C catalysts at a constant potential for 7200s in alkaline methanol solution. Moreover, after 1000 cycles of durability testing, PtPd NWs/graphene retained 89.2% of its initial mass activity, much superior to the 63.7% retained for commercial Pt/C.

Piezocatalytic Effect Induced Hydrogen Production from Water over Non-noble Metal Ni Deposited Ultralong GaN Nanowires.

Piezoelectric material-based catalysis that relies on an external stress-induced piezopotential has been demonstrated to be an effective strategy toward various chemical reactions. In this work, non-noble metal Ni-decorated ultralong monocrystal GaN nanowires (NWs) were prepared through a chemical vapor deposition (CVD) technique, followed by a photodeposition method. The piezocatalytic activity of the GaN NWs was enhanced by ∼9 times after depositing the Ni cocatalyst, generating hydrogen gas of ∼88.3 μmol·g-1·h-1 under ultrasonic vibration (110 W and 40 kHz), which is comparable to that of Pt-loaded GaN NWs. Moreover, Ni/GaN NWs with smaller diameters (∼100 nm) demonstrated superior piezocatalytic efficiency, which can be attributed to the large piezoelectric potential evidenced by both finite-element analysis and piezoresponse force microscopy measurements. These results demonstrate the promising application potential of non-noble metal loaded GaN nanostructures in hydrogen generation driven by weak mechanical energy from the surrounding environment.

Bi2S3 Nanowires: First-Principles Phonon Dynamics and Their Photocatalytic Environmental Remediation

We reported the synthesis and full characterization of ultralong Bi2S3 nanowires with diameters of 60–80 nm and lengths above 1 μm, showing growth in the [001] direction. Combining the computed lattice dynamics of orthorhombic Bi2S3 with the experimental micro-Raman scattering study provided comprehensive solutions. We demonstrate that 10 active modes originated from Raman symmetry modes (4Ag + 2B1g + 3B2g + 1B3g), and the peak at 124 cm–1 is due to the IR-active B3u mode. The use of the Bi2S3 catalyst for dewatering hexavalent chromium-containing wastewater was also reported. This confirms it to be a potential candidate for photocatalytic environmental remediation.

Luminescent net-like inorganic scaffolds with europium-doped hydroxyapatite for enhanced bone reconstruction.

Bone reconstruction is an urgent problem during clinical treatment. In the past few decades, the construction of composite scaffolds has been a hot spot in the research field of bone tissue engineering (BTE). However, the disadvantages of composite materials raise our awareness to explore the potential application of hydroxyapatite (HAp) in bone substitutes due to the closest properties of HAp to natural bone tissue. In our study, we synthesized Eu3+-doped HAp (HAp:Eu3+) ultralong nanowires, which can be transformed to hydrophilic net-like scaffolds via a thiol-ene click reaction. The property of luminescence of HAp from Eu3+ is beneficial for identifying the relative position of materials and bone marrow mesenchymal stem cells (BMSCs). HAp:Eu3+ scaffolds with excellent cell biocompatibility could promote the expression of early bone formation markers (ALP and ARS) and enhance the expression of genes and proteins associated with osteogenesis (Runx 2, OCN, and OPN). In the end, the results of the in vivo osteogenesis experiment showed that pure HAp scaffolds presented different effects of bone tissue reconstruction compared with the composite scaffolds with HAp nanorods and polymer materials. The superior osteogenic effect could be observed in net-like pure HAp scaffold groups. Furthermore, the absorption of HAp:Eu3+ scaffolds could be monitored due to the luminescence property of Eu3+. This strategy based on ultralong HAp nanowires proved to be a new method for the construction of simple reticular scaffolds for potential osteogenic applications.

Highly porous and elastic aerogel based on ultralong hydroxyapatite nanowires for high-performance bone regeneration and neovascularization.

Hydroxyapatite (HAP) is promising for the clinical treatment of bone defects because of its excellent biocompatibility and osteo-conductivity. However, highly porous HAP scaffolds usually exhibit high brittleness and poor mechanical properties, thus organic constituents are usually added to form composite materials. In this work, a highly porous and elastic aerogel made from ultralong HAP nanowires with ultrahigh porosity (∼98.5%), excellent elasticity and suitable porous structure is prepared as the high-performance scaffold for bone defect repair. The highly porous structure of the as-prepared aerogel is beneficial to bone ingrowth and matter/fluid transfer, and the high elasticity can ensure the structural integrity of the scaffold during bone regeneration. Therefore, the HAP nanowire aerogel scaffold can promote the adhesion, proliferation and migration of rat bone marrow derived mesenchymal stem cells (rBMSCs), and elevate the protein expression of osteogenesis and angiogenesis related genes. The in vivo experimental results demonstrate that the HAP nanowire aerogel scaffold is favorable for the ingrowth of new bone and blood vessels, and thus can greatly accelerate bone regeneration and neovascularization. The as-prepared HAP nanowire aerogel scaffold shows promising potential for biomedical applications such as bone defect repair.

A Silk Fibroin and Ultra-Long Silver Nanowires Based Transparent Conductive Composite Film for Nanosensor Devices

In addition to flexible touch screens, organic flexible photoelectric films have broad application prospects. In this paper, a transparent and conductive composite film was prepared by embedding a conductive network of ultra-long silver nanowires with silk fibroin as the substrate material. The ultra-long length can help minimize the number of junctions between the nanowires on the conductive grid, which can reduce greatly the resistance and optical shielding effect of the conductive layer. To tune the flexibility of the film, an appropriate amount of calcium ions (Ca2+) could be added to the silk fibroin solution. The conductivity, light transmittance, and temperature, stress and humidity sensitivity of the composite films were characterized and proved satisfactory. Its capability of self-healing was also demonstrated. With the natural biocompatibility and self-healing ability, this silk fibroin film may be applied in biomedical science, such as an electronic skin that can detect multiple human health indicators.

Ultra-long KFeS2 nanowires grown on Fe foam as a high-performance anode for aqueous solid-state energy storage

A high-performance anode for aqueous solid-state energy storage is fabricated using ultra-long KFeS2 nanowires grown on Fe foam. The assembled solid-state battery exhibits enhanced specific areal capacity, high-rate capability, and long-term cycling stability.