Nanowire Membrane Research Articles

Synthesis of flexible cross-linked cryptomelane-type manganese oxide nanowire membranes and their application for U(VI) and Eu(III) elimination from solutions

The efficient elimination of radionuclides from aqueous solutions is crucial for environmental protection from radionuclides’ pollution. The construction of octahedral molecular sieve (OMS-2) nanoporous membranes is of great technical importance for different kinds of applications like purification filter, catalysts, oil separation, seawater desalination and pollutant elimination. The facile synthesis of freestanding materials demonstrated uniform and monodispersed nanostructures and a cross-sectional pattern of the membranes, which is easily recycled in the process of adsorption and separation of pollutants from aqueous solutions. The OMS-2 exhibited rapid adsorption kinetics and high adsorption capacities of U(VI) (348 mg/g) and Eu(III) (106 mg/g) at pH = 5.0 ± 0.1 and T = 298 K. The paper-like membranes still retained the original filiform morphologies and showed extraordinary stability after 6 adsorption cycles. The surface complexation and ion exchange were the main mechanisms for the uptake of radionuclides, and the change of water environment had little influence on radionuclide adsorption efficiency. Based on the high adsorption capacity and excellent recycle ability, the OMS-2 membranes are considered as superior adsorbents for the efficient elimination of metal ions in the decontamination of polluted water.

Local Crack-Programmed Gold Nanowire Electronic Skin Tattoos for In-Plane Multisensor Integration.

Sensitive, specific, yet multifunctional tattoo-like electronics are ideal wearable systems for "any time, any where" health monitoring because they can virtually become parts of the human skin, offering a burdenless "unfeelable" wearing experience. A skin-like, multifunctional electronic tattoo made entirely from gold using a standing enokitake-mushroom-like vertically aligned nanowire membrane in conjunction with a programmable local cracking technology is reported. Unlike previous multifunctional systems, only a single material type is needed for the integrated gold circuits involved in interconnects and multiplexed specific sensors, thereby avoiding the use of complex multimaterials interfaces. This is possiblebecause the programmable local cracking technology allows for the arbitrary fine-tuning of the properties of elastic gold conductors from strain-insensitive to highly strain-sensitive simply by adjusting localized crack size, shape, and orientations-a capability impossible to achieve with previous bulk cracking technology. Furthermore, in-plane integration of strain/pressure sensors, anisotropic orientation-specific sensors, strain-insensitive stretchable interconnects, temperature sensors, glucose sensors, and lactate sensors without the need of soldering or gluing are demonstrated. This strategy opens a new general route for the design of next-generation wearable electronic tattoos.

Stainless steel mesh supported TiO2 nanowires membrane with ultra-high flux for separation of oil-in-water mixtures and emulsions

A stainless steel mesh supported TiO2 nanowires membrane is prepared by heating hydrogen titanate nanowires deposited on stainless steel mesh. The stainless steel mesh supported TiO2 nanowires membrane exhibits superhydrophilic and underwater superoleophobic property. The water contact angles in air of the stainless steel mesh supported TiO2 nanowires membrane is 0° and the underwater oil contact angles (gasoline, n-hexadecane, hexamethylene and methylbenzene) are >150°. Both of surfactant-free oil-in-water mixtures and surfactant-stabilized emulsions are separated with a high permeation flux of >106 L m−2 h−1 bar−1 and a separation efficiency of >99.1%. The stainless steel mesh supported TiO2 nanowires membrane exhibits good resistant to fouling, and the possible organic pollutants are easy to be removed by heat treatment and the superhydrophilic and underwater superoleophobic property is recovered.

110th Anniversary: Liquid Separation Membranes Based on Nanowire Substrates for Organic Solvent Nanofiltration and Membrane Distillation

Ceramic nanowire-based flat porous membranes allow development of organic–inorganic membranes. Two types of surface modifications of alumina nanowire-based membranes were implemented. The first one involved reaction of hydroxyl groups on an alumina surface with silicone oil at a higher temperature, developing a grafted coating yielding a nonporous or a porous hydrophobic membrane. The hydrophobicity was verified via a contact angle comparable to that of a porous hydrophobic ethylene chlorotrifluoroethylene membrane. The membrane porosity was demonstrated by running vacuum membrane distillation with a 1 wt % salt-containing brine. The process yielded satisfactory water vapor flux with 98% salt rejection. The silicone oil’s reaction with the alumina surface could also block the pores, yielding a nonporous membrane for organic solvent nanofiltration (OSN). Interfacial polymerization was also carried out on the porous nanowire membrane to yield a nonporous polyamide membrane. The developed membrane was tested...

Anti-fouling TiO2 nanowires membrane for oil/water separation: Synergetic effects of wettability and pore size

TiO2 nanowires (NWs) membranes with varied wettability ranging from superhydrophilic to superhydrophobic have been facile fabricated via dip-coating for oil/water separation. Incorporating TiO2 NWs results in the increase of roughness and the formed hierarchical structure from TiO2 NWs micro-aggregations enlarges the wettability. Separation efficiency and permission flux of the as-prepared membranes increase first and decrease with the increment of TiO2 NWs. These superhydrophilic/hydrophilic membranes eliminate water from oil/water mixtures and the separation efficiency declines with the increasing water contact angle until the membrane lose the oil/water separation property at around 90°. Membranes with water contact angle of 90–100° cannot separate oil/water mixtures while membranes with water contact angle larger than 120° become oil-remove type with separation efficiency around ~ 99% and high permission flux. The study illustrates that relatively large pore size (~ 15 µm) attributes to the high separation efficiency and permission flux. The synergetic effects of wettability and pore size indicate that surface wettability is critical for efficient oil/water separation. Both hydrophilic and superhydrophilic membranes show high separation efficiency and outstanding anti-fouling performances after long term oil/water separation.

High-Flux Oil/Water Separation with Interfacial Capillary Effect in Switchable Superwetting Cu(OH)2@ZIF-8 Nanowire Membranes.

Highly ordered architectures with roughness and porous surface are the key challenges toward developing smart superwetting membranes. We prepared switchable superwetting Cu(OH)2@ZIF-8 core/shell nanowire membranes for high-flux oil/water separation as well as simultaneous heavy-metal ions removal in one step. The well-defined Cu(OH)2@ZIF-8 core/shell nanowire grown on copper mesh with average length of ca. 15 μm and diameter of ca. 162 nm exhibits high water contact angle (CA) of ca. 153 ± 0.6°. After modified by ethanol, the membrane holds the reverse superwettability with oil (dichloromethane as an example) CA of ca. 155 ± 0.8° underwater. The separation efficiencies of the membranes are higher than that of 97.2% with a remarkable flux rate higher than 90 000 L m-2 h-1 for the immiscible oil/water mixture. And the removal efficiency for Cr3+ ions at 10 ppb can arrive at 99.2 wt % in the toluene-in-water emulsion. The high performances of the smart superwetting membranes can be attributed to the interfacial capillary effects of the hierarchical Cu(OH)2@ZIF-8 core/shell nanostructures. This work may provide a new insight into the design of smart superwetting surfaces for oil/water separation and target adsorption in one step.

Magnetic-field-induced rapid synthesis of defect-enriched Ni-Co nanowire membrane as highly efficient hydrogen evolution electrocatalyst

Metallic Ni-based materials are promising electrocatalysts for commercial alkaline water electrolysis towards hydrogen generation. It is therefore desirable to develop low-cost and controllable synthesis protocols for efficient Ni-based electrocatalysts. Here we report a rapid one-step method to fabricate self-supported membranes of highly-conductive Ni-Co nanowires, which are formed via self-assembly of reduced Ni/Co nanoparticles under a rotating magnetic field. The Ni-Co nanowires are composed of Co nanoparticles and NiCo alloy nanoparticles domains, with abundant inherent interface defects due to incomplete alloying and insufficient Ostwald ripening during the assembly. Nanowires with different Ni/Co ratios are tested as the HER electrodes in comparison to pure Ni mesh and Ni foam electrodes; And the Ni0.50Co0.50 nanowire electrode gives the most optimized performance. The HER activity shows little degradation for nearly 100 h. These nanowire electrodes are superior to the state-of-the-art metallic Ni-based ones. This facile technology may represent a critical step towards scalable production of highly active and durable metallic Ni-based electrocatalysts for industry applications.

Integrating Superwettability within Covalent Organic Frameworks for Functional Coating

Summary Despite the availability of a variety of skeletons for covalent organic frameworks (COFs), control of pore-surface wettability remains undeveloped, which could immensely expand their overall versatility. Herein, we contribute an effective strategy for imparting superwettability on COFs by chemically coating the pore surface with perfluoroalkyl groups to confer them with superhydrophobicity. Taking advantage of controllable modification, the resultant COFs retain the porosity and crystallinity of the pristine COFs. Benefiting from the bulk superhydrophobicity of the COF crystals and the feasibility of COF synthesis, they can be used as a coat or in situ integrated within various substrates; once applied, this renders them superhydrophobic. Given the modular nature, this protocol is compatible with the development of various specific wettabilities in COFs, which thereby constitutes a step for expanding the scope of COF applications and provides many opportunities for the processing of advanced materials and devices.

Interfacial Constructing Flexible V2O5@Polypyrrole Core-Shell Nanowire Membrane with Superior Supercapacitive Performance.

Flexible membrane consisting of ultralong V2O5@conducting polypyrrole (V2O5@PPy) core-shell nanowires is prepared by a facile in situ interfacial synthesis approach. The V2O5 is for the first time demonstrated to show versatile function of reactive template to initiate the uniform and conformal polymerization of PPy nanocoating without the need for extra oxidants. The freestanding PPy-encapsulated V2O5 nanowire membrane is of great benefit in achieving strong electrochemical harvest by increasing electrical conductivity, shortening ion/electron transport distance, and enlarging electrode/electrolyte contact area. When evaluated as binder- and additive-free supercapacitor electrodes, the V2O5@PPy core-shell hybrid delivers a significantly enhanced specific capacitance of 334 F g-1 along with superior rate capability and improved cycling stability. The present work would provide a simple yet powerful interfacial strategy for elaborate constructing V2O5/conducting polymers toward various energy-storage technologies.

Chinese Knot Inspired Ag Nanowire Membrane for Robust Separation in Water Remediation

AbstractChinese knot is a “traditional handicraft art” in Chinese culture, which is expected to ward off evil spirits and pray for good luck. It is constructed by weaving cords and tying different types of knots firmly. Inspired by Chinese knot, a robust 1D Ag nanowire membrane with nanoscale knots is fabricated to achieve robust catalytic/anti‐bacterial separation. Silver mirror reaction is manipulated to anchor Ag nanowires on a hierarchical polyvinylidene fluoride membrane substrate. The robust Ag nanowire membrane withstands the vigorous cross‐flow hydraulic shear (3000 mL min−1) for 24 h at 0.1 MPa without any physicochemical deterioration. The Chinese knot inspired membrane exhibits extraordinary robustness in continuous catalysis, “kill‐release” anti‐bacteria, oil‐in‐water emulsion, and ultrafiltration separation. This work paves a new way for constructing a robust 1D inorganic nanowire membrane for water remediation applications.

Flexible and Highly Photosensitive Electrolyte-Gated Organic Transistors with Ionogel/Silver Nanowire Membranes.

Flexible and low-voltage photosensors with high near-infrared (NIR) sensitivity are critical for realization of interacting humans with robots and environments by thermal imaging or night vision techniques. In this work, we for the first time develop an easy and cost-effective process to fabricate flexible and ultrathin electrolyte-gated organic phototransistors (EGOPTs) with high transparent nanocomposite membranes of high-conductivity silver nanowire (AgNW) networks and large-capacitance iontronic films. A high responsivity of 1.5 × 103 A·W1-, high sensitivity of 7.5 × 105, and 3 dB bandwidth of ∼100 Hz can be achieved at very low operational voltages. Experimental studies in temporal photoresponse characteristics reveal the device has a shorter photoresponse time at lower light intensity since strong interactions between photoexcited hole carriers and anions induce extra long-lived trap states. The devices, benefiting from fast and air-stable operations, provide the possibility of the organic photosensors for constructing cost-effective and smart optoelectronic systems in the future.

Removal of dissolved toluene in underground water with nanowires of manganese oxide

The objective of the present study was to investigate the adsorption behavior of manganese oxide nanowires as an adsorbent for the removal of dissolved toluene from underground water. The nanowire membrane, composed of three-dimensional porous nanostructures plus superhydrophobic character, is very suitable for removal of the hydrophobic molecules. The effects of adsorbent dose, contact time, initial solution concentration, pH, salinity, and recyclability on the uptake of toluene by the adsorbent in batch mode are examined. The adsorption data compared to the adsorption of two kinds of activated carbons show that manganese oxide nanowire is competitive to activated carbons. Furthermore, the equilibrium data are fitted to different types of adsorption isotherms. Freundlich isotherm model illustrated the best fit to the data. The results of this study suggest that nanowires of manganese oxides can be used as a low cost, highly efficient adsorbent for the removal of dissolved hydrocarbon from aqueous solution.

Effect of post-heat treatment on the photocatalytic activity of titanium dioxide nanowire membranes deposited on a Ti substrate

Titanium dioxide nanowire membranes have been synthesized by a hydrothermal growth on the surfaces of Ti substrates in a 12 M NaOH aqueous solution at 160 °C for 24 h, followed by ion-exchange with 0.5 M HCl aqueous solution and subsequent heat treatment.

Hydrophobic silver nanowire membrane for swabbing extraction and in situ SERS detection of polycyclic aromatic hydrocarbons on toys

The migration of solid samples from the interior to the surface of materials has raised serious concerns due to the increasing environmental health hazards in recent years.

Fabrication of Si3N4 nanowire membranes: free standing disordered nanopapers and aligned nanowire assemblies

Herein, ultralong silicon nitride nanowires were synthesized via a chemical vapor deposition method by using the low-cost quartz and silicon powder as raw materials. Simple processes were used for the fabrication of disordered and ordered nanowire membranes of pure silicon nitride nanowires. The nanowires in the disordered nanopapers are intertwined with each other to form a paper-like structure which exhibit excellent flame retardancy and mechanical properties. Fourier-transform infrared spectroscopy and thermal gravity analysis were employed to characterize the refractory performance of the disordered nanopapers. Highly ordered nanowire membranes were also assembled through a three-phase assembly approach which make the Si3N4 nanowires have potential use in textured ceramics and semiconductor field. Moreover, the surface nanowires can also be modified to be hydrophobic; this characteristic make the as-prepared nanowires have the potential to be assembled by the more effective Langmuir–Blodgett method and also make the disordered nanopapers possess a super-hydrophobic surface.

Enhanced disinfection of Escherichia coli and bacteriophage MS2 in water using a copper and silver loaded titanium dioxide nanowire membrane

Titanium dioxide (TiO2) is a widely used photocatalyst that has been demonstrated for microorganism disinfection in drinking water. In this study, a new material with a novel structure, silver and copper loaded TiO2 nanowire membrane (Cu-Ag-TiO2) was prepared and evaluated for its efficiency to inactivate E. coli and bacteriophage MS2. Enhanced photo-activated bactericidal and virucidal activities were obtained by the Cu-Ag-TiO2 membrane than by the TiO2, Ag-TiO2 and Cu-TiO2 membranes under both dark and UV light illumination. The better performance was attributed to the synergies of enhanced membrane photoactivity by loading silver and copper on the membrane and the synergistic effect between the free silver and copper ions in water. At the end of a 30 min test of deadend filtration under 254 nm UV irradiation, the Cu-Ag-TiO2 membrane was able to obtain an E. coli removal of 7.68 log and bacteriophage MS2 removal of 4.02 log, which have met the US EPA standard. The free metal ions coming off the membrane have concentrations of less than 10 ppb in the water effluent, far below the US EPA maximum contaminant level for silver and copper ions in drinking water. Therefore, the photo-activated disinfection by the Cu-Ag-TiO2 membrane is a viable technique for meeting drinking water treatment standards of microbiological water purifiers.

A positively charged silver nanowire membrane for rapid on-site swabbing extraction and detection of trace inorganic explosives using a portable Raman spectrometer

The sensitive and on-site detection of inorganic explosives has raised serious concerns regarding public safety. However, high stability and non-volatility features currently limit their rapid on-site detection. Surface-enhanced Raman spectroscopy (SERS) is emerging as a powerful technique for the trace-level detection of different molecules. Plasmonic Ag nanowires were produced by a hydrothermal synthesis method using polyvinylpyrrolidone (PVP) as a negatively charged stabilizer. Here, we report a rapid detection method for inorganic explosives based on a simple surface swab with a positively charged diethyldithiocarbamate-modified Ag nanowire membrane coupled with SERS. This membrane, serving as an excellent SERS substrate with high uniformity, stability, and reusability, can capture both typical oxidizers in inorganic explosives and organic nitro-explosives, via electrostatic interaction. The detection level of perchlorates (ClO4−), chlorates (ClO3−), nitrates (NO3−), picric acid, and 2,4-dinitrophenol is as high as 2.0, 1.7, 0.1, 45.8, and 36.6 ng, respectively. In addition, simulated typical inorganic explosives such as black powders, firecrackers, and match heads could also be detected. We believe that this membrane represents an attractive alternative for rapid on-site detection of inorganic explosives with high efficiency.

Oil-Water Separation Using a Self-Cleaning Underwater Superoleophobic Micro/Nanowire Hierarchical Nanostructured Membrane

In this study, we fabricated a novel micro/nanowire hierarchical membrane with flexible, self-cleaning and underwater superoleophobic properties for efficient oil-water separation under vacuum filtration. This novel membrane composed of ultralong copper microwires (MW) and functional TiO2 nanowires (NW). The ultralong copper microwires act as a scaffold, as well as providing mechanical flexibility for the membrane, which allow it to be operated under vacuum-driven condition. Meanwhile, underwater superoleophobic TiO2 nanowires membrane provides nano- scale pore size, ensuring the filtration of smaller oil droplets under vacuum condition. Moreover, the possession of the self-cleaning function of TiO2 nanowires allows the degradation of foulants and contaminants under UV irradiation, which promote the facile recovery of the used membrane. Clearly, the employment of this novel membrane can be considered as a practical option for efficient oil-water separations.

Heterogeneous-surface-mediated crystallization control

The crystallization of matter at interfaces has long been a significant issue in science and technology, but surface-directed crystallization with controlled kinetics remains a matter of challenge. Here, we demonstrate a conceptual novel mechanism to steer liquid–solid phase transformation at interfaces by tailoring the chemical and structural inhomogeneity of a glass substrate through self-limited nanocrystallization of the glassy phase. Importantly, this approach enables large-scale development of metastable crystallization products, such as nanowire membranes. The thorough studies of the intermediate stages of crystallization reveal a unique cooperative mechanism in which the intricate interplays between inherent nanoscale forces and unique heterogeneous surfaces contribute to the mesoscale structural transformation from isolated units to superstructures. We further show that the constructed superstructures offer unprecedented opportuntities for the development of functional membrane systems possessing the combination of robust trace-detection performance and molecular trapping function. These findings not only present clear technological implications, but also provide an improved understanding of the fundamental mechanisms of surface-induced geological and biological processes. A glassy surface embedded with zones of crystalline order can spur materials to form nanowires and molecule-trapping membranes on demand. Surface-induced crystallization plays important roles in processes ranging from bone biomineralization to transistor fabrication. Shifeng Zhou from South China University of Technology in Guangzhou and co-workers have reported a great discovery that glass-ceramics surface can help to control liquid-to-solid transformations at interfaces without resorting to chemical treatments or specialized templates. Using thermal treatments, the team precipitated titanium dioxide nanocrystals into an otherwise homogenous inorganic oxide glass. The resulting non-uniform interface created periodic potential field that enabled strict control over crystal nucleation and aggregation. Additional charge imbalances between tiny aggregations guided materials to grow into remarkable superstructures. As a practical example, microporous silver membranes that detect trace amounts of hazardous aromatic vapours were demonstrated. A new surface-directed crystallization mechanism enabled by the chemical and structural inhomogeneity of the glass substrate through self-limited nanocrystallization of glassy phase was proposed and demonstrated. Benefiting from the intricate interplays between nanoscale force and heterogeneous surface, the strategy offers new opportunities in the large-scale development of various metastable crystallization products and also serves practical purpose.

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.