Jianlong Ge

Ultralight nanofibre-assembled cellular aerogels with superelasticity and multifunctionality

Three-dimensional nanofibrous aerogels (NFAs) that are both highly compressible and resilient would have broad technological implications for areas ranging from electrical devices and bioengineering to damping materials; however, creating such NFAs has proven extremely challenging. Here we report a novel strategy to create fibrous, isotropically bonded elastic reconstructed (FIBER) NFAs with a hierarchical cellular structure and superelasticity by combining electrospun nanofibres and the fibrous freeze-shaping technique. Our approach causes the intrinsically lamellar deposited electrospun nanofibres to assemble into elastic bulk aerogels with tunable densities and desirable shapes on a large scale. The resulting FIBER NFAs exhibit densities of >0.12 mg cm(-3), rapid recovery from deformation, efficient energy absorption and multifunctionality in terms of the combination of thermal insulation, sound absorption, emulsion separation and elasticity-responsive electric conduction. The successful synthesis of such fascinating materials may provide new insights into the design and development of multifunctional NFAs for various applications.

In situ polymerized superhydrophobic and superoleophilic nanofibrous membranes for gravity driven oil–water separation

Creating an efficient, cost-effective method that can provide simple, practical and high-throughput separation of oil-water mixtures has proved extremely challenging. This work responds to these challenges by designing, fabricating and evaluating a novel fluorinated polybenzoxazine (F-PBZ) modified nanofibrous membrane optimized to achieve gravity driven oil-water separation. The membrane design is then realized by a facile combination of electrospun poly(m-phenylene isophthalamide) (PMIA) nanofibers and an in situ polymerized F-PBZ functional layer incorporating SiO2 nanoparticles (SiO2 NPs). By employing the F-PBZ/SiO2 NP modification, the pristine hydrophilic PMIA nanofibrous membranes are endowed with promising superhydrophobicity with a water contact angle of 161° and superoleophilicity with an oil contact angle of 0°. This new membrane shows high thermal stability (350 °C) and good repellency to hot water (80 °C), and achieves an excellent mechanical strength of 40.8 MPa. Furthermore, the as-prepared membranes exhibited fast and efficient separation of oil-water mixtures by a solely gravity driven process, which makes them good candidates for industrial oil-polluted water treatments and oil spill cleanup, and also provided new insights into the design and development of functional nanofibrous membranes through F-PBZ modification.

Superhydrophilic and underwater superoleophobic nanofibrous membrane with hierarchical structured skin for effective oil-in-water emulsion separation

A novel superhydrophilic and underwater superoleophobic nanofibrous membrane with a hierarchical structured skin for the separation of oil-in-water emulsions was prepared via electrospinning and electrospraying methods, and was found to exhibit excellent separation efficiency, robust antifouling properties, and extremely high flux solely driven by gravity.

Polybenzoxazine-based highly porous carbon nanofibrous membranes hybridized by tin oxide nanoclusters: durable mechanical elasticity and capacitive performance

Creating porous carbonaceous membranes with durable mechanical properties and designed functionality is critical for the next generation of soft electronic devices; however, it has been proven extremely challenging. Herein, we report a facile strategy to fabricate highly porous carbon nanofibrous membranes with enhanced mechanical elasticity and intriguing functionality based on polybenzoxazine via combining multicomponent electrospinning and in situ polymerization. Tin oxide nanoclusters with diameters of 20–40 nm are homogenously distributed in the carbon matrix and on the surface of carbon nanofiber (CNF). A plausible plasticizing effect of the heterogeneous nanotextures endows the SnO2/CNF membrane with robust mechanical elasticity and durability, which can maintain its original shape after serious deformation. Moreover, the elastic SnO2/CNF membrane possesses a high surface area of 1415 m2 g−1 with a pore volume of 0.82 cm3 g−1. With their integrated properties of extraordinary mechanical properties, high porosity, large surface area, and good electrochemical properties, the as-prepared SnO2/CNF membranes exhibited a satisfactory capacitive performance with high energy density, ultralong cycling properties, and robust electrochemical stability against bending deformation, suggesting a promising usage as soft electrodes for flexible energy storage devices, and also opened up an avenue to the design of functional CNF materials with fine elasticity for various applications.

Cobalt oxide nanoparticles embedded in flexible carbon nanofibers: attractive material for supercapacitor electrodes and CO2 adsorption

Introducing flexibility and high porosity into carbon nanofibers (CNFs) is one of the critical challenges for the next generation of multifunctional energy storage and CO2 adsorption materials. Herein, we developed an efficient strategy for the controllable fabrication of a flexible and mechanically robust Co3O4 nanoparticles (NPs) doped CNFs (CNFs-Co) hybrid membrane via electrospinning and subsequent carbonization treatment. The quantitative pore size distribution and fractal analysis revealed that the CNFs-Co possessed a tunable porous structure with high surface area of 483 m2 g−1. Therefore, it exhibited exceptional performance in CO2 capture, i.e. a high CO2 adsorption capacity of 5.4 mmol g−1 at 1 bar and room temperature. Electrochemical measurements performed on CNFs-Co for supercapacitor applications demonstrated very high capacitance of up to ∼911 F g−1 at 5 mV s−1 (76% capacitance retention after 1000 cycles) in 1 M H2SO4 solution. The successful synthesis of this hybrid membrane may also provide new insights towards the development of materials for various multifunctional applications.

Hierarchical porous carbon nanofibrous membranes with an enhanced shape memory property for effective adsorption of proteins

Designing and fabricating hierarchical porous carbon nanofibrous (CNF) membranes with good mechanical properties is an attractive and challenging work for the next generation of functional separation materials. Here, we demonstrate a novel strategy to create a heterostructured CNF membrane with multiscale pores via multicomponent electrospinning and nano-doping methods. The resultant membrane exhibits an intriguing shape memory property, which can be bent to a radius < 100 μm without any fracture and recover from the deformation rapidly. Besides that, the carbonaceous nanofibrous membrane is quite soft like polymer based wrapping paper. Such robust mechanical properties may be attributed to the “plasticizer” effect of the doped SiO2 nanoparticles and the protogenetic graphitized carbon layers in the carbon matrix. More interesting, benefitting from the functional nitrogenous groups and the hierarchical porous structures, these CNF membranes possess a high adsorption capacity for target protein molecules and high water permeability (15 202 ± 1927 L m−2 h−1 under 3 kPa driven pressure), which is an order of magnitude higher than the commercial polymer based affinity membranes. As this technology is effective and easy to operate, more multifunctional CNF based nanoscale materials could be developed for the next generation of highly efficient proteins separations.

Adsorbents Based on Electrospun Nanofibers

In the past few decades, removing or controlling the concentration levels of the pollutants including toxic gases, heavy metal ions, and organic contaminants in environmental systems has attracted tremendous attention. Among the numerous approaches, adsorption is considered to be one of the most versatile and promising approach in removing pollutants due to its convenience, ease of operation, simplicity of design, and universal in use. Electrospun nanofibers have unique properties such as large surface area, tailored pore structure, high porosity, and flexibility of surface functionalization, therefore could be used as advanced adsorbents for contaminant removal. Importantly, nanofiber-based adsorbents are expected to possess strong adsorption capacity, fast kinetics, and good reproducibility due to the unique structure of nanofibers. In this chapter, we summarize recent progress in the development of electrospun nanofibrous membrane-based adsorbent for the removal of toxic gases and pollutants in aqueous solution (heavy metal ions and organic contaminants), describe the design of the nanofibrous materials, and discuss their adsorption performance in detail. This chapter might trigger further development and evolution of adsorption based on electrospun nanofibers as one potential to ease the environmental pollution problem.

Biomimetic Multilayer Nanofibrous Membranes with Elaborated Superwettability for Effective Purification of Emulsified Oily Wastewater

Creating a porous membrane to effectively separate the emulsified oil-in-water emulsions with energy-saving property is highly desired but remains a challenge. Herein, a multilayer nanofibrous membrane was developed with the inspiration of the natural architectures of earth for gravity-driven water purification. As a result, the obtained biomimetic multilayer nanofibrous membranes exhibited three individual layers with designed functions; they were the inorganic nanofibrous layer to block the serious intrusion of oil to prevent the destructive fouling of the polymeric matrix; the submicron porous layer with designed honeycomb-like cavities to catch the smaller oil droplets and ensures a satisfactory water permeability; and the high porous fibrous substrate with larger pore size provided a template support and allows water to pass through quickly. Consequently, with the cooperation of these three functional layers, the resultant composite membrane possessed superior anti-oil-fouling property and robust oil-in-water emulsion separation performance with good separation efficiency and competitive permeation flux solely under the drive of gravity. The permeation flux of the membrane for the emulsion was up to 5163 L m-2 h-1 with a separation efficiency of 99.5%. We anticipate that our strategy could provide a facile route for developing a new generation of specific membranes for oily wastewater remediation.

Applications of Electrospun Nanofibers in Oil Spill Cleanup

Oil is one of the important sources of energy in the modern industrial world which has to be transported from the source of production to many places across the globe through oceans and inland transport. During transportation the chance of oil spillage over the water body occurs due to accidents or by deliberate action during wartime that causes severe environmental pollution. Nanofibers, mainly fabricated by electrospinning, have exhibited great potential for many emerging environmental applications including oil spill cleanup. They can be considered as one of the safest nanomaterials due to their extremely long length (can be up to hundreds of kilometers) and their ability to be embedded within other media. Their high surface-to-volume ratio, large porosity (up to over 80 %), and adjustable functionality are also much more effective than conventional nonwoven and polymeric membranes in particulate oil sorption and oil–water separation. For sustainable environment, disposal of used sorbents is a major issue. In this context, the naturally available biodegradable materials have great potential than the synthetic ones. This chapter reviews about oil spill cleanup with special emphasis on the wetting phenomenon used for oil absorption and cross-flow filtration methods of oil spill cleanup as well as focus on the characteristics of nanofibrous oil sorbent materials, fluid flow through nanofibrous materials, and types of nanofibrous materials envisaged for making sorbents cross flow filtration membranes.

Polybenzoxazine Functionalized Melamine Sponges with Enhanced Selective Capillarity for Efficient Oil Spill Cleanup

Severe environmental and ecological issues arising from frequent oil spill accidents have been great worldwide concerns. Considering the abruptness, complex condition, and long-term perniciousness of the spilled oil, the development of economic and versatile materials to quickly remove oil contaminants, especially for oil with high viscosity from a large water body, is of significant importance but remains a big challenge. Herein, we demonstrated a facile strategy to fabricate a versatile hierarchical structured sponge with superhydrophobicity and powerful oil capillarity via the in situ polymerization of a novel phenolic resin (polybenzoxazine) composite open-cell sponges. The tunable hierarchical structures of the as-prepared sponge significantly improved its water repellence and oil capillarity; meanwhile, a plausible mechanism is also proposed. With the merits of high porosity, excellent water repellence, enhanced oil capillarity, and robust mechanical stability, the obtained sponge exhibited an intriguing oil spill cleanup performance with fast oil absorption speed, good recyclability, and high absorption capacity. Besides that, the modified sponge could also be utilized for the separation of oil/water mixture with individual phase and the surfactant-stabilized emulsion solely under the drive of gravity. The robust oil/water separation performance, low cost, and facile synthesis strategy make the resultant sponges a competitive material for the large-scale oil spill emergency remediation.