Nanowire Membrane Research Articles

Three-dimensional Li3V2(PO4)3/C nanowire and nanofiber hybrid membrane as a self-standing, binder-free cathode for lithium ion batteries

A three-dimensional (3D) mace-like Li3V2(PO4)3/C nanowire and nanofiber hybrid membrane was prepared for self-standing, bind-free electrodes.

A novel Ni@Ni(OH)2 coaxial core-sheath nanowire membrane for electrochemical energy storage electrodes with high volumetric capacity and excellent rate capability

We report a facile approach to fabricate a novel membrane electrode based on unique Ni@Ni(OH)2 coaxial core-sheath structures for electrochemical energy storage application in this work. The Ni nanowire membranes, prepared from vacuum filtration of Ni nanowires with unique embossments, can be used as excellent precursors for preparing Ni@Ni(OH)2 membranes by an electrochemical cyclic voltammetry method. After electrochemical treatment, a layer of amorphous Ni(OH)2 was obtained on the surface of Ni nanowires. An important property of the as-synthesized Ni@Ni(OH)2 membranes is that it can be directly utilized for electrochemical energy storage applications without the need for binders or additional conducting additives. The Ni@Ni(OH)2 electrode demonstrates a high volumetric capacity (111.1Ccm−3 at 0.12Acm−3), excellent rate capability (83.1Ccm−3 at 1.92Acm−3), and cycling stability at a high current density (78% capacity retention after 1500 cycles at 1.92Acm−3). This fabrication method is very simple and paves a new route for designing membrane electrodes based on similar structures for high-performance electrochemical energy storage electrodes.

Novel anti-fouling Fe2O3/TiO2 nanowire membranes for humic acid removal from water

Membrane fouling is one of the major obstacles inhibiting the wide application of membrane technologies for water treatment. Membranes with surface modification of titanium dioxide (TiO2) nanoparticles or TiO2 nanowire membranes (Ti–NWM) have demonstrated reduced membrane fouling due to the photocatalytic capability of TiO2 in degrading foulants on the membrane surface. However, the wide band gap of TiO2 makes it only absorb ultraviolet light, which limits its applications under solar irradiation. In this study, a novel membrane made of interwoven iron oxide (Fe2O3) nanowires and TiO2 nanowires (FeTi–NWM) has demonstrated superior anti-fouling capability in removing humic acid (HA) from water. Results showed that under simulated solar irradiation the FeTi–NWM achieved nearly complete HA removal during a 2h short-term test at an initial HA concentration of 200mg/L, compared with 89% HA removal by Ti–NWM. During a 12h long-term test, the FeTi–NWM maintained 98% HA removal, while the Ti–NWM showed only 55% removal at the end. Without solar irradiation, the FeTi–NWM was severely contaminated and by contrast, a clean surface was maintained under solar irradiation after the 12h test and the transmembrane pressure change was minimal. The improved HA removal by FeTi–NWM compared with Ti–NWM and its excellent anti-fouling capability under solar irradiation can be attributed to (1) the enhanced HA absorption by Fe2O3 nanowires and (2) the formed Fe2O3/TiO2 heterojunctions that increase photo-induced charge transfer and improve visible light activity.

Synthesis of ultralong MnO/C coaxial nanowires as freestanding anodes for high-performance lithium ion batteries

Ultralong MnO/C nanowire membranes have been fabricated using a facile approach and applied as freestanding anodes for lithium-ion batteries.

Ultrathin and lightweight 3D free-standing Ni@NiO nanowire membrane electrode for a supercapacitor with excellent capacitance retention at high rates.

A free-standing binder-free 3D Ni@NiO nanowire membrane is fabricated by a simple filtration method followed by thermal annealing. With an appropriate annealing temperature, the functional nanowires can keep their rough and echinate surface, and the conductive network composed of welded nickel nanowire cores is well-preserved without isolation (0.53 Ω/sq). The unique 3D multigrade mesporous structure not only accelerates the intercalation and deintercalation velocity of electrolyte ions but also provides numerous electroactive sites for the Faraday reaction. As a result, the supercapacitor electrode can preserve a capacitance retention of 96.1% (36.9 F/cm(3)) with a high discharge current density, indicating its wonderful rate capability. The fabricated membrane electrode exhibits high volumetric capacitance, stable cycling life, and remarkable retention of the capacitance at high rate, energy, and power density, making it a promising candidate for application in portable electronic products.

Hydrothermal growth of TiO2 nanowire membranes sensitized with CdS quantum dots for the enhancement of photocatalytic performance.

In this paper, TiO2 nanowires (NWs) on Ti foils were prepared using a simple hydrothermal approach and annealing treatment. CdS quantum dots (QDs) were assembled onto the crystallized TiO2 NWs by sequential chemical bath deposition. Ultraviolet-visible absorption spectra showed that CdS adds bands in the visible to the TiO2 absorption and exhibited a broad absorption band in the visible region, which extended the scope of absorption spectrum and helped improve the photocatalytic degradation efficiency. The results of photocatalytic experiment revealed that CdS-TiO2 NWs possessed higher photocatalytic activities toward methyl orange than pure TiO2 nanowires. The degradation efficiency of 96.32% after ten cycles indicated that the as-prepared CdS-TiO2 composite exhibited excellent long-time recyclable ability and can be reused for the degradation of contaminants.

High-efficiency dye-sensitized solar cells based on ultra-long single crystalline titanium dioxide nanowires

High-efficiency dye-sensitized solar cells (DSCs) based on 3D networks of ultra-long single crystalline TiO2 nanowires are fabricated. By hydrothermal reaction of Ti foils in alkali aqueous solution, following ion exchange and high temperature sintering processes, the ultra-long single crystalline TiO2 nanowires can be prepared. Due to long enough of the TiO2 nanowires, they not only form 1D arrays perpendicular to Ti foils, but also extend to form 3D network structure on the top-side of the arrays. By optimizing the hydrothermal duration at 24 h, the formed TiO2 nanowire membrane based front-side illuminated photoanode shows enhanced dye-loading and light scattering abilities and excellent charge transport properties. So the DSC with this photoanode can attain to the highest power conversion efficiency about 8.05%.

Fabrication of flexible α-MnO2 nanowire membranes with superior mechanical strength

The Assembly of one-dimensional (1D) nanostructures such as nanowires/nanorods/nanotubes into two-dimensional (2D) macrostructured films is attracting considerable research interest because of their unique properties and wide applications. In this study, flexible membranes were successfully fabricated using α-MnO2 nanowires synthesized through a hydrothermal method. The effects of thickness and post-annealing temperature on the mechanical properties of the membranes were investigated in detail. Nano-indentation measurements showed that the modulus of the as-prepared 11.75 μm-thick membrane reached 5.765 GPa, and the modulus increased with the increasing post-annealing temperature. Thus, the fabricated membranes with superior mechanical strength can have potential applications such as in photocatalysis, filtering, and supporting substrates.

A disordered silver nanowires membrane for extraction and surface-enhanced Raman spectroscopy detection

A disordered silver nanowires membrane combining solid-phase extraction (SPE) with surface-enhanced Raman spectroscopy (SERS) was used for the rapid collection and detection of food contaminants. The membrane was fabricated via filtration of the silver nanowires colloid solution, which was prepared by a solvothermal polyol process. Analytes in 5 mL of liquid phase were concentrated in less than 10 s due to their affinity for the silver nanowires on the filter membrane. The membrane combined the advantages of SPE and SERS technology for the analysis of food safety contaminants. The use of the SERS-active extraction membrane eliminated the procedure of elution, which shortened the time of analysis. It has been shown that the as-prepared membrane had good uniformity and high temporal stability under continuous laser irradiation. Qualitative and quantitative detection of phorate and melamine was further performed based on a flow-through method. The characteristic SERS intensity plotted against phorate and melamine concentrations exhibited a good linear relationship over the concentration range of 2.5 to 10 μg mL(-1) (phorate) and 2.5 to 100 μg mL(-1) (melamine).

Biomimetic Multifunctional Nanochannels Based on the Asymmetric Wettability of Heterogeneous Nanowire Membranes

A charged heterogeneous nanowire membrane with asymmetric wettability serves as a biomimetic passive channel when the bilayer is hydrophilic; It also functions as pH valve based on the hydrophobic CaWO4 layer (contact angle of 145.3˚±0.3˚) and hydrophilic MnO2 layer. Moreover, a reversible ionic rectification is realized in the above-mentioned semi-hydrophobic and hydrophilic state with strong acid environment or in the complete hydrophobic stage with a moderate discrepancy (CA of CaWO4 and MnO2 layer are 141.3˚±0.3˚ and 157.6˚±2.0˚, respectively) in near neuter condition.

Synthesis of carbonaceous nanowire membrane for removing heavy metal ions and high water flux

This study investigated the hydrothermal synthesis of carbonaceous nanowire membrane (CNM) and its separation performances in terms of adsorbing heavy metals and transmembrane water permeation in water treatment. The hydrothermal dehydration and carbonization of mono-saccharide (glucose; 180°C, 48h) can yield one-dimensional (1D) carbonaceous nanowires in the presence of tellurium nanowire template. The subsequent solution-evaporation-self-assembly process results in the formation of macro-scale two-dimensional (2D) hydrophilic CNM sheet with large specific surface area, developed nanoporosity, and abundant superficial oxygen-containing functional groups. Owing to these unique properties, the CNM is shown to be capable of efficiently adsorbing a variety of heavy metals, and highly permeable to water molecules. The CNM synthesized gives precedence over conventional membrane and adsorbents, and demonstrates promise as sustainable nanomaterial for separation of heavy metals from water via membrane adsorption process.

Rapid and large-scale synthesis of Cu nanowires via a continuous flow solvothermal process and its application in dye-sensitized solar cells (DSSCs)

Single crystalline copper nanowires with pentagonal cross sections and large aspect ratios have been successfully prepared in high yield via a continuous flow solvothermal reduction process at a low temperature. The highly crystalline filaments exhibit the face-centered cubic structure, growing mainly along the [110] direction. Both PVP and the solvent environment play an important role for the growth of nanowires. The growth mechanism has been properly discussed. We also report the flexible transparent Cu nanowire membrane electrode fabricated by coating a polymer layer as a potential replacement for the conventional FTO electrode in dye-sensitized solar cells (DSSCs). Fabricated CuNW membranes exhibit high optical transmittance and electrical conductance, which can be controlled via the synthesis process, conveniently. The efficiency of a DSSC with CuNWs increases upto 5%. The DSSC performs as well as with a FTO electrode, which indicates that the super-high aspect ratio of the Cu nanowires offers a range of electrical transport routes to connect dye loaded photo-anodes, and such an electrode has the potential to replace conventional FTO electrodes for low-cost DSSCs applications.

Fast and highly-sensitive hydrogen sensing of Nb2O5 nanowires at room temperature

The single-crystalline Nb2O5 nanowires with tetragonal phase structures were synthesized through thermal oxidation process. The Nb2O5 nanowires were grown along [001] orientation and formed a layer of free-standing nanowire membrane. A pair of platinum electrodes was deposited on the surface of the nanowire layer to fabricate a Pt/Nb2O5 nanowire hydrogen sensor. The Pt/Nb2O5 nanowire hydrogen sensor exhibited fast, highly-sensitive and selective hydrogen response at room temperature, which may be attributed to the hydrogen induced interface and surface effects together with the high specific surface area of the Nb2O5 nanowires.

An inverted fabrication method towards a flexible dye sensitized solar cell based on a free-standing TiO 2 nanowires membrane

This paper reports an inverted fabrication process for the photoanode of a flexible dye sensitized solar cell (DSSC). This procedure involves assembling a free-standing TiO 2 nanowires/nanoparticles hybrid membrane, via high temperature annealing, sputtering an indium tin oxide (ITO) layer onto this membrane, and transferring these onto a polydimethylsiloxane (PDMS) substrate. The inverted procedure prevents thermal decomposition of polymer substrate, whilst enabling effective thermal treatment of the functionalized titanium oxide. The flexible DSSC fabricated in this way has an efficiency of 2.7%, which is comparable with rigid device constructed using similar materials.

Hydrothermal growth of free standing TiO 2 nanowire membranes for photocatalytic degradation of pharmaceuticals

Highly entangled TiO 2 nanowires were directly synthesized by hydrothermal growth on Ti substrates at 180 °C utilizing various organic solvents to oxidize Ti. The growth mechanism, microstructure and phase transition of TiO 2 nanowire membranes were investigated in detail. TiO 2 nanowires, with diameters of 10–20 nm and lengths up to 100 μm, show a phase transition from Type-B to anatase by annealing at 700 °C. Robust, free standing TiO 2 nanowire membranes with millimeter level thickness can be cleaved from Ti substrates or directly prepared from thin Ti foils. These porous TiO 2 membranes, while effective for mechanical microfiltration, can also photocatalytically degrade pharmaceuticals such as trimethoprim under UV irradiation.

Self-Supported Supercapacitor Membrane Through Incorporating MnO<SUB>2</SUB> Nanowires into Carbon Nanotube Networks

We report on a study on the development of a self-supported membrane of carbon nanotube (CNT) mixed with MnO2 nanowires as supercapacitors. Both single-walled CNTs (SWCNTs) and multiwalled CNTs (MWCNTs) have been explored to serve as the electrically conductive networks to connect redox active MnO2 nanowires. High-quality alpha-MnO2 nanowires were synthesized using bulk alpha-MnO2 crystals as the precursor by a facile hydrothermal method. The morphology and structure of the as-prepared alpha-MnO2 nanowires were characterized by X-ray and electron diffraction, transmission electron microscopy, and scanning electron microscopy. Supercapacitor membranes were prepared by filtration of mixture solutions of MnO2 nanowires and CNTs at various ratios, forming entangled networks which are self-supported and directly used as supercapacitor electrodes without binders or backing metals. Cyclic voltammetry at various scan rates and charge--discharging measurements are used to characterize the supercapacitance of the CNT-MnO2 nanowire membranes. The specific capacitance has been found to be increased by several times over that of pure CNT membranes after incorporation of MnO2 nanowires.

Transport selectivity of tribenuron‐methyl imprinted polymer nanowire membrane prepared using N,O‐bismethacryloyl ethanolamine as a functional crosslinking monomer

AbstractUsing tribenuron‐methyl as a template and N,O‐bismethacryloyl ethanolamine as a functional crosslinking monomer, a molecularly imprinted nanowire membrane was prepared over an anodic alumina oxide membrane. The nanowire fabric of the imprinted membrane was established with a scanning electron microscope and a transmission electron microscope. However, the nonimprinted particulate membrane is formed in the absence of a template. Scatchard analysis showed that an equal class of binding sites were formed in the imprinted nanowire membrane and the dissociation constant and the maximum number of these binding sites were estimated to be 1.44 × 10−5 M and 22.7 µmol/g, respectively. The permeation experiments throughout the imprinted membrane and the nonimprinted one were carried out in a solution containing the template and its competitive analogs. These results demonstrated that the molecularly imprinted nanowire membrane exhibited higher transport selectivity for the template tribenuron‐methyl than its analogs, chlorimuron‐ethyl, thifensulfuron‐methyl and N‐(4‐bromophenylcarbamoyl)‐5‐chloro‐1H‐benzo[d]imidazole‐2‐carboxamide. But the nonimprinted granular membrane had no permselectivity for the four substrates. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Heteronanostructure of Ag particle on titanate nanowire membrane with enhanced photocatalytic properties and bactericidal activities

A novel seed induced method has been developed for syntheses of Ag particles on titanate nanowires, and then the heteronanostructured Ag/titanate nanowires were assembled into porous, flexible membranes. These titanate nanowires were about several hundreds micrometers in length and about 80 nm in diameter. The size of the Ag particle can be tuned within 300-700 nm. The pore size and thickness of the heteronanostructured membrane were easily controlled. An Ag/titanate nanowire membrane reactor has been developed to study the photocatalytic degradation of methamidophos in aqueous solution, and 87.0% of the methamidophos can be degraded in a concurrent filtration and photocatalytic oxidation process. The antibacterial activity was also investigated on the heteronanostructured membrane with UVA light (365 nm) irradiation, and a 99.99% satisfactory antibacterial effect on Escherichia coli was achieved.

Superwetting nanowire membranes for selective absorption

The construction of nanoporous membranes is of great technological importance for various applications, including catalyst supports, filters for biomolecule purification, environmental remediation and seawater desalination. A major challenge is the scalable fabrication of membranes with the desirable combination of good thermal stability, high selectivity and excellent recyclability. Here we present a self-assembly method for constructing thermally stable, free-standing nanowire membranes that exhibit controlled wetting behaviour ranging from superhydrophilic to superhydrophobic. These membranes can selectively absorb oils up to 20 times the material's weight in preference to water, through a combination of superhydrophobicity and capillary action. Moreover, the nanowires that form the membrane structure can be re-suspended in solutions and subsequently re-form the original paper-like morphology over many cycles. Our results suggest an innovative material that should find practical applications in the removal of organics, particularly in the field of oil spill cleanup.

TiO 2 nanowire membrane for concurrent filtration and photocatalytic oxidation of humic acid in water

A novel TiO 2 nanowire membrane was successfully fabricated using hydrothermal synthesis-filtration method. The fabricated TiO 2 membrane had uniform thickness and was flexible to form into other shape modules. These nanowires were of 20–100 nm in diameter and had typical length in the range of several micrometers to tens of micrometers. The pore size of the TiO 2 nanowire membrane was about 0.05 μm. The TiO 2 nanowire membrane exhibited similar photocatalytic activity as commercial TiO 2 powder (P25) on degradation of humic acid in water. In continuous experiment, TiO 2 nanowire membrane achieved near 100% and 93.6% removal rate of humic acid and total organic carbon (TOC), respectively, via a concurrent filtration and photocatalytic oxidation. The TiO 2 nanowire membrane also showed excellent anti-fouling ability owing to the photodegration of foulants by the TiO 2 nanowire membrane.