Ultrafine Hollow Research Articles

Wall-mounted ultrafine hollow fiber membrane module for purification of domestic surface water

The World Health Organization (WHO) estimated that around 844 million people worldwide lack safe drinking water, including 159 million who are dependent only on surface water. Investing in a practical, sustainable, and cost-effective treatment process is indispensable to alleviating the effect of water shortage. Besides water treatment, ultrafiltration (UF) membranes are broadly used in protein fractionation and clarification of fruit juices. The hollow fiber (HF) membrane configuration has a much larger surface area per unit volume, resulting in higher productivity than the flat-sheet membrane. A spinneret was developed with a provision for altering the fiber's inner diameter from 1000 µm to 150 µm and outer dimension from 1500 µm to 350 µm, respectively, using an inbuilt detachable needle arrangement. The ultrathin hollow fiber produced by the indigenously designed spinnerets has a high surface area and packing density, which makes it useful for surface water treatment. A wall-mounted module was designed for direct connection to the tap to obtain a purified water flow of 30–40 liter per hour (LPH) for domestic use, operated with or without electricity. The fabricated ultrafine HF module (ID: 150–200 µm; OD: 350–450 µm) removes complete bacterial contamination and turbidity up to 95–100 %, making the quality of processed water potable. The developed membrane module is durable due to its large membrane area per unit volume, enhancing productivity, high packing density, good fouling resistance, easy handling, and self-supporting structure for backwashing. The present research article paves the way forward to investing in a practical, sustainable, and economical treatment process that is indispensable to alleviating the effect of water shortage.

In-situ growth microcircuits on bacterial membranes to enhance ion capture capability for capacitive deionization

The combination of biotechnology and artificial nanotechnology provide new breakthroughs in the design and manufacture of energy materials. In this work, the porous hollow hyphae carbon membrane with different thicknesses were acquired by biological cultivation approach, along with adsorbed Ni2+ as the in-situ growth points. Then, ultrafine hollow carbon tubes generated on the hyphae surface, forming multi-stage composite membrane (CNTs@MC) with tubules covering large tubes. Subsequently, rich amino functional groups were grafted onto MC (hyphae carbon membrane) surface to further improve its hydrophilicity and capacitance. In addition to the hollow structure, the hyphae carbon surface presents many small holes around 50 nm, which not only provides space for Ni2+ adsorption, but also favors the generation of double-layer capacitance. As secondary structure, ultrafine carbon nanotubes as microcircuits capture more charged ions on hyphae surface, thus offering better capacitance performance. The multistage hollow structure enhances the stability of material during ion adsorption. The grafted amino functional groups and intrinsic heteroatomic defects synergically enhance the wettability and pseudocapacitance of material. In general, large effective specific surface area, abundant surface amino functional groups and intrinsic heteroatomic defects guarantee the high capacitance of material, and also exhibits desirable performance in both solid-state supercapacitors and capacitive deionization applications.

The reaction mechanism of highly dispersed Cu atoms and ultrafine MnOx nanoclusters co-modified ZSM-5 based on in-situ heteronuclear substitution for catalytic oxidation C6H14

A series of Mn/Cu cosubstituted ZSM-5 (Zeolite Socony Mobil–5) with different Mn/Cu molar ratios were synthesized by a one-step heteronuclear substitution hydrothermal method. Singly substituted Mn- and Cu-ZSM-5 compounds were also prepared. The catalytic oxidation performance of hexane and the catalyst surface physicochemical properties over each catalyst were investigated to determine the reaction activity, the main influencing factors and the mechanism for hexane oxidation. Part of the framework Mn of ZSM-5 was substituted by Cu2+ during Mn/Cu cosubstitution, facilitating the generation of isolated and/or framework Cu2+ and extraframework ultrafine hollow spherical MnOx nanoclusters, and increasing the low-temperature reducibility and the amount and transfer capacity of superficial lattice oxygen. Mn-Cu-HZ(1:1) with an appropriate Mn/Cu cosubstitution ratio exhibited the best catalytic oxidation performance, mainly because it has the most superficial lattice oxygens, a relatively high transfer capacity, the highest low-temperature reducibility and suitable acidity. Synergetic catalysis could occur between isolated and/or framework Cu2+ and ultrafine MnOx nanoclusters via a Mars-Van Krevelen (MvK) mechanism. A reaction route for hexane oxidation over Mn-Cu-HZ(1:1) was proposed based on the in situ DRIFTS and GC–MS results. This work provides new insights into the design of VOC degradation catalysts.

Ultrafine hollow Fe3O4 anode material modified with reduced graphene oxides for high-power lithium-ion batteries

In this work, a composite material consisting of ultrafine Fe3O4 with (ca. 15 nm) uniformly anchored in reduced graphene oxides (rGO) is synthesized and reported to be applied in anodes for lithium-ion battery. The obtained hollow Fe3O4/rGO composites (H-Fe3O4/rGO) (827.3 mA h g−1) has much superior specific capacity than that of the solid Fe3O4/rGO composites (S-Fe3O4/rGO) (654.9 mA h g−1) after 550 cycles of the coin cell at 0.5 A g−1. Even if the cells are tested at 1 A g−1, H-Fe3O4/rGO displays a remarkable specific capacity of 917.4 mA h g−1 as well as the capacity retention rate of 56.7%, compared with S-Fe3O4/rGO (573.9 mA h g−1, the capacity retention rate of 37.7%). Such a sufficient cyclic stability and rate capability in the H-Fe3O4/rGO composite is mainly attributed to the ultrafine hollow structure for shortening Li+ diffusion path and conductive rGO beneficial to rapid electron transfer.

Close‐packed storage of potassium metallic clusters achieved through nanostructure engineering of ultrafine hollow nanoparticles‐based carbon nanoclusters

AbstractUltrafine hollow nanoparticles‐based (7 nm) carbon nanoclusters (HNPCNCs) are developed by a facile and novel method. Benefiting from the ultrafine nanostructure, we have achieved close‐packed storage of K metallic clusters and a close‐packed K metallic clusters with a diameter of 7 nm has been observed for the first time through ex TEM. In K‐ion batteries, HNPCNCs anodes deliver an ultrahigh capacity of 269.8 mA h g−1 at 0.5 A g−1 after 200 cycles, outstanding rate performance of 150.5 mA h g−1 after 5000 cycles at 5 A g−1. Moreover, an excellent electrochemical performance has been obtained by HNPCNCs//potassium Prussian blue potassium‐ion full cells, highlighting the practicability of HNPCNCs. The unprecedented electrochemical performance is attributed to the close‐packed K metallic clusters achieved by unique ultrafine hollow nanoparticles in the carbon nanoclusters.image

Hollow carbon nanocapsules-based nitrogen-doped carbon nanofibers with rosary-like structure as a high surface substrate for impedimetric detection of Pseudomonas aeruginosa

The design of hollow mesoporous carbon-based materials has attracted tremendous attention, due to their sizeable intrinsic cavity to load specific chemical and unique physical/chemical properties in various applications. Herein, we have established an effective strategy for the preparation of novel hollow carbon nanocapsules-based nitrogen-doped carbon nanofibers (CNCNF) with rosary-like structure. By embedding ultrafine hollow carbon nanocapsules into electrospun polyacrylonitrile (PAN) skeleton, the as-designed composite CNFs were carbonized into hierarchical porous CNFs, consisted of interconnected nitrogen-doped hollow carbon nanocapsules. Due to its individual structural properties and unique chemical composition, the performance of CNCNF was evaluated in aptasensor application via the detection of Pseudomonas aeruginosa (PA). Under optimized conditions, the aptasensor based on CNCNF has a detection limit of 1 CFU⋅mL−1 and a linear range from 101 CFU ⋅mL−1 to 107 CFU ⋅mL−1 (n = 3). Moreover, the designed aptasensor possesses high sensivity, high selectivity, low detection limit, and high reproducibility. These studies showed that the CNCNF material offers a wide variety of enhanced electrochemical features as an electrode material for aptasensor application.

Ultrafine hollow TiO2 nanofibers from core-shell composite fibers and their photocatalytic properties

Abstract The oxidized electrospun polyacrylonitrile (o-PAN) fibers are used as templates and formed core-shell composite fibers by coating a layer of TiO2 sol. After calcination in air, hollow TiO 2 nanofibers (HTONFs) are fabricated by removing the PAN fibrous template for the photocatalyzed degradation of methylene blue (MB). Scanning electron microscopy, transmission electron microscopy , X-ray diffraction and Raman spectra are used to characterize the morphologies and structures of HTONFs. The effects of MB concentration, amount of TiO 2, light intensity, pH and calcination temperatures on the reaction rate constant are investigated. At last, HTONFs is recycled by a simple method, and the reutilization for photocatalyzation is evaluated.

Fabrication of Stainless Steel Microneedle with Laser-Cut Sharp Tip and its Penetration and Blood Sampling Performance

The demand for minimally invasive injection needles or needle-shaped tools is growing from those who carry out medical practices such as blood or insulin injections. Applying the mosquito biomimetic, we have used a femtosecond laser to fabricate minimally invasive microneedles out of ultrafine hollow SUS304 pipes, 50μm in outer diameter and 20μm in inner diameter. When such a stainless steel needle tip is angled at 15°, it has the lowest penetration resistance, two and a half times lower than that of the finest hollow needle that is commercially available. A blood suction experiment with a newly developed microneedle has demonstrated that 2.8μellof blood can be drawn out in 20 seconds. Such stainless steel microneedles fabricated by femtosecond lasers have great potential as minimally invasive and mass-producible blood sampling needles to be used for diabetic inspections.

Electrochemical properties of hollow copper (II) oxide nanopowders prepared by salt-assisted spray drying process applying nanoscale Kirkendall diffusion

The synthesis of hollow CuO nanopowders by a salt-assisted spray drying process applying nanoscale Kirkendall diffusion is introduced. The electrochemical properties of the hollow CuO nanopowders for lithium-ion storage are also investigated. The first step of post-treatment of the spray-dried powders under a reducing atmosphere forms spherical and hollow NaCl powders embedded with Cu nanocrystals. Further post-treatment of the Cu–NaCl composite powders under an air atmosphere forms the spherical and hollow NaCl powders embedded with the hollow CuO nanopowders. Oxidation of the Cu nanocrystals under an air atmosphere produces hollow CuO nanopowders by nanoscale Kirkendall diffusion. The spherical and hollow CuO–NaCl composite powder transforms into ultrafine hollow CuO nanopowders by complete washing with distilled water to remove NaCl. The initial discharge and charge capacities of the hollow CuO nanopowders for lithium-ion storage at a current density of 1 A g−1 are 1077 and 781 mA h g−1, respectively. The reversible discharge capacity of the hollow CuO nanopowders for the 700th cycle is 803 mA h g−1.

Preparation of zirconium diboride ultrafine hollow spheres by a combined sol–gel and boro/carbothermal reduction technique

As an important ceramic possessing many excellent properties, zirconium diboride (ZrB2) has attracted considerable attention and found many ultra-high temperature applications. In this work, ZrB2 ultrafine powders were successfully synthesized by a combined one-pot sol–gel and boro/carbothermal reduction method using zirconium oxychloride, boric acid and glucose as starting materials. Pure ZrB2 was successfully synthesized at 1,500 °C for 2 h using the optimal molar ratios of n(B)/n(Zr) = 2.5 and n(C)/n(Zr) = 6.5. The as-prepared ZrB2 powders were characterized by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive spectroscopy, selected area electron diffraction and transmission electron microscopy. The grain size and the crystalline size of the as-prepared ZrB2 powders were found to be 1–2 μm and about 48 nm, respectively. Interestingly, some ZrB2 ultrafine hollow spheres (UHS) with diameters from 100 to 500 nm were also in situ formed with the ZrB2 ultrafine particles during the sol–gel and boro/carbothermal reduction process. The mechanism for the formation of these ZrB2 UHS was also proposed based on the experimental results.

Electromagnetic wave absorption properties of composites with ultrafine hollow magnetic fibers

Ultrafine hollow magnetic fibers were prepared by electroless plating using hydrolyzed polyester fiber as a sacrificial substrate. These hollow fibers can be served for lightweight and efficient electromagnetic (EM) absorbing materials. As observed from SEM and EDS analysis, hollow structures consisting of Ni inner layer and Fe or Fe–Co outer layer were obtained. By introducing Co onto Fe, oxidation of the Fe layer was successfully prevented making it possible to enhance the complex permeability compared to a case in which only Fe was used. Polymeric composites containing the hollow fibers with different weight fractions and fiber lengths were prepared by a simple mixing process. The electromagnetic wave properties of the composites were measured by a vector network analyzer and it was found that the hollow magnetic fibers show a clear resonance peak of the complex permittivity around the X-band range (8–12GHz) and the resonance frequency strongly depends on the fiber concentration and length. A possible explanation for the unique resonance is that the hollow fibers possess relatively low electrical conductivity and a long mean free path due to their oxidized phase and hollow structure. The calculated EM wave absorption with the measured EM wave properties showed that the composite containing 30wt% hollow Ni/Fe–Co (7:3) fibers in length of 180μm exhibited multiple absorbance peaks resulting in a broad absorption bandwidth of 4.2GHz. It is obvious that this multiple absorbance is attributed to the resonance characteristic of the composite.

Oxygen mass transfer coefficient in bubble column slurry reactor with ultrafine suspended particles and neural network prediction

AbstractThe gas–liquid volumetric mass transfer coefficient was determined by the dynamic oxygen absorption technique using a polarographic dissolved oxygen probe and the gas–liquid interfacial area was measured using dual‐tip conductivity probes in a bubble column slurry reactor at ambient temperature and normal pressure. The solid particles used were ultrafine hollow glass microspheres with a mean diameter of 8.624 µm. The effects of various axial locations (height–diameter ratio = 1–12), superficial gas velocity (uG = 0.011–0.085 m/s) and solid concentration (εS = 0–30 wt.%) on the gas–liquid volumetric mass transfer coefficient kLaL and liquid‐side mass transfer coefficient kL were discussed in detail in the range of operating variables investigated. Empirical correlations by dimensional analysis were obtained and feed‐forward back propagation neural network models were employed to predict the gas–liquid volumetric mass transfer coefficient and liquid‐side mass transfer coefficient for an air–water–hollow glass microspheres system in a commercial‐scale bubble column slurry reactor. © 2012 Canadian Society for Chemical Engineering

Ultrafine hollow needle formation on silicon

A method for the formation of ultrafine hollow needles, microcylindrical and nano-wall structures on silicon substrates is reported. The fabrication of these ultrafine structures is possible through a combination of high-precision high aspect ratio vertical etching of silicon with a small angle vacuum deposition technique where nanometric walls are feasible. These structures can be used as the media to transfer gas and liquid through their tiny holes. In addition, the structure has been used to realize cavity-based capacitance inclination sensor suitable for small angle detection. A capacitance variation of 0.6 pF/degree of inclination has been obtained.

Facile Fabrication of Ultrafine Hollow Silica and Magnetic Hollow Silica Nanoparticles by a Dual-Templating Approach.

The development of synthetic process for hollow silica materials is an issue of considerable topical interest. While a number of chemical routes are available and are extensively used, the diameter of hollow silica often large than 50 nm. Here, we report on a facial route to synthesis ultrafine hollow silica nanoparticles (the diameter of ca. 24 nm) with high surface area by using cetyltrimethylammmonium bromide (CTAB) and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as co-templates and subsequent annealing treatment. When the hollow magnetite nanoparticles were introduced into the reaction, the ultrafine magnetic hollow silica nanoparticles with the diameter of ca. 32 nm were obtained correspondingly. Transmission electron microscopy studies confirm that the nanoparticles are composed of amorphous silica and that the majority of them are hollow.

Fabrication of ultrafine hollow Ni and Ni/Fe fibers and their dispersion characteristics in the epoxy matrix

Abstract In order to develop a material with light weight and homogeneous characteristics for the electromagnetic wave absorbing, hollow Ni and Fe metallic micro fibers were fabricated by electroless plating and heat treatment method. It is expected that hollow and fibrous structure of fibers can reduce the weight and increase the efficiency of electromagnetic properties. As a substrate for electroless metal plating, commercial polyester micro fibers were used. The surface of micro fibers was coated with Ni and Ni/Fe metal layers and then heat-treated under the argon atmosphere to make the fiber a hollow structure. The surface morphology and composition were verified by SEM and EDS analyses. Hollow structures of the fibers were observed and the optimal thickness of Ni and Fe layers were about 200–300 and 500–700 nm, respectively. Polymeric composites containing 10, 20 and 30 wt.% of hollow Ni/Fe micro fibers were fabricated by mechanical mixing method. SEM images demonstrated the uniform distribution of hollow metallic micro fibers in the epoxy matrix.

Silver Nanoparticles Filling in TiO 2 Hollow Nanofibers by Coaxial Electrospinning

This study investigated the coaxial electrospinning process of silver filling in TiO 2 ultrafine hollow fibers using polyvinyl pyrrolidone (PVP) sol/titanium n-butyloxide (Ti(OC 4H 9) 4) and PVP sol/silver nanoparticles as pore-directing agents. The bicomponent fibers were heat treated at 200 °C and calcined at 600 °C. Silver particles having diameters of 5 to 40 nm were deposited on the inner surface of the long hollow TiO 2 nanofibers (outer diameter of 150.300 nm) with mesoporous walls (thickness of 10.20 nm). The morphological structure of the filled ultrafine hollow fibers has been studied by means of infrared (IR) spectrum, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The diameters and wall thicknesses of the hollow fibers could be tuned by adjusting the electrospinning parameters. Compared with other nanostructured TiO 2 materials, such as mesoporous Ag-TiO 2 blending fibers, TiO 2 hollow nanofibers, TiO 2 nanofibers, and TiO 2 powders, the silver filled TiO 2 hollow fibers exhibited a higher photocatalytic activity toward the degradation of methylene blue.

Surgery in your living room

The design of hollow mesoporous carbon-based materials has attracted tremendous attention, due to their sizeable intrinsic cavity to load specific chemical and unique physical/chemical properties in various applications. Herein, we have established an effective strategy for the preparation of novel hollow carbon nanocapsules-based nitrogen-doped carbon nanofibers (CNCNF) with rosary-like structure. By embedding ultrafine hollow carbon nanocapsules into electrospun polyacrylonitrile (PAN) skeleton, the as-designed composite CNFs were carbonized into hierarchical porous CNFs, consisted of interconnected nitrogen-doped hollow carbon nanocapsules. Due to its individual structural properties and unique chemical composition, the performance of CNCNF was evaluated in aptasensor application via the detection of Pseudomonas aeruginosa (PA). Under optimized conditions, the aptasensor based on CNCNF has a detection limit of 1 CFU⋅mL−1 and a linear range from 101 CFU ⋅mL−1 to 107 CFU ⋅mL−1 (n = 3). Moreover, the designed aptasensor possesses high sensivity, high selectivity, low detection limit, and high reproducibility. These studies showed that the CNCNF material offers a wide variety of enhanced electrochemical features as an electrode material for aptasensor application.