Anisotropic Self-Assembly of Asymmetric Mesoporous Hemispheres with Tunable Pore Structures at Liquid-Liquid Interfaces.

Asymmetric materials have attracted tremendous interest because of their intriguing physicochemical properties and promising applications, but endowing them with precisely controlled morphologies and porous structures remains a formidable challenge. Herein, a facile micelle anisotropic self-assembly approach on a droplet surface is demonstrated to fabricate asymmetric carbon hemispheres with a jellyfish-like shape and radial multilocular mesostructure. This facile synthesis follows an interface-energy-mediated nucleation and growth mechanism, which allows easy control of the micellar self-assembly behaviors from isotropic to anisotropic modes. Furthermore, the micelle structure can also be systematically manipulated by selecting different amphiphilic triblock copolymers as a template, resulting in diverse novel asymmetric nanostructures, including eggshell, lotus, jellyfish, and mushroom-shaped architectures. The unique jellyfish-like hemispheres possess large open mesopores (∼14 nm), a high surface area (∼684 m2 g-1), abundant nitrogen dopants (∼6.3 wt %), a core-shell mesostructure and, as a result, manifest excellent sodium-storage performance in both half and full-cell configurations. Overall, our approach provides new insights and inspirations for exploring sophisticated asymmetric nanostructures for many potential applications.

Modulation of solid surface with desirable under-liquid wettability based on molecular hydrophilic-lipophilic balance.

There has been great interest in the fabrication of solid surfaces with desirable under-liquid wettability, and especially under-liquid dual-lyophobicity, because of their potential for widespread use. However, there remains the lack of a general principle to modulate the under-liquid wettability in terms of surface energy (SE). Herein, we found that the relative proportion between the polar and dispersive components in SE that reflects the competition between hydrophilicity and lipophilicity governs the under-liquid wettability of the solid surface. For the first time, we introduced hydrophilic-lipophilic balance (HLB) calculated solely based on the amount and type of hydrophilic and lipophilic fragments in surface molecules to rapidly predict the under-liquid wettability of a solid surface, thereby guiding the fabrication of solid surfaces with desirable under-liquid wettability. Accordingly, the under-liquid dual superlyophobic surfaces in a nonpolar oil-water-solid system were fabricated by grafting molecules with appropriate HLB values (e.g., 6.341-7.673 in a cyclohexane-water-solid system) onto porous nanofibrous membranes, which were able to achieve continuous separation of oil-water mixtures. This work provides reasonable guidance for the fabrication of solid surfaces with targeted under-liquid wettability, which may lead to advanced applications in oil-water-solid systems.

Flexible Multifunctional Porous Nanofibrous Membranes for High-Efficiency Air Filtration.

Particulate matter (PM) discharged along with the rapid industrialization and urbanization hazardously threatens ecosystems and human health. Membrane-based filtration technology has been proved to be an effective approach to capture PM from the polluted air. However, the fabrication of filtration membranes with excellent reusability and antibacterial activity has rarely been reported. Herein, the flexible multifunctional porous nanofibrous membranes were fabricated by embedding Ag nanoparticles into the electrospun porous SiO2-TiO2 nanofibers via an impregnation method, which integrated the abilities of PM filtration and antibacterial performance. Compared with the reported air filters, the resultant membrane (Ag@STPNM) with high surface polarity and porous structure possessed the low density, high removal efficiency, and small pressure drop. For instance, the removal efficiency and the pressure drop of Ag@STPNM with a basis weight of only 3.9 g m-2 for PM2.5 reached 98.84% and 59 Pa, respectively. In terms of the excellent thermal stability of Ag@STPNM, the adsorbed PM could be removed simply by a calcination process. The filtration performance of Ag@STPNM kept stable during five purification-regeneration cycles and the long-time filtration for 12 h, exhibiting excellent recyclability and durability. Furthermore, the embedded Ag nanoparticles could achieve the effective resistance to the breeding of bacteria on Ag@STPNM, giving the bacteriostatic rate of 95.8%. Therefore, Ag@STPNM holds promising potentials as a highly efficient, reusable, and antibacterial air filter in the practical purification of the indoor environment or personal air.

Under-liquid dual superlyophobic nanofibrous polymer membranes achieved by coating thin-film composites: a design principle.

Surfaces with under-liquid dual superlyophobicity have garnered tremendous interest because of their promising applications, but their unexplored underlying nature restricts the designed construction of such surfaces. Herein, we coated the thin-film composites with different terminal groups over the electrospun polyacrylonitrile nanofibrous membranes, which afforded the membranes excellent stability in organic solvents, as well as modulated under-liquid wetting behaviors. Among them, the representative under-liquid dual superlyophobic 4-cyan-Ph-terminated membrane could realize highly efficient separation of all types of oil/water mixtures and even emulsions. Moreover, we found that the under-liquid wetting behaviors could be classified in terms of the intrinsic water contact angle (θ w). By comparing the total interfacial energy, we proved that the under-liquid dual lyophobic surfaces were thermodynamically metastable. On this basis, we could predict the θ w of rough surfaces with the under-liquid dual lyophobicity in a given oil-water-solid system (e.g., 47.3-89.1° in cyclohexane-water-solid system, R = 2). This work provides a design principle for the fabrication of under-liquid dual superlyophobic surfaces, which will open potential applications in diverse fields in terms of such smart surfaces.

Amino-Functionalized Porous Nanofibrous Membranes for Simultaneous Removal of Oil and Heavy-Metal Ions from Wastewater.

Both oil spill and heavy-metal ions in the industrial wastewater cause severe problems for aquatic ecosystem and human health. In the present work, the electrospun superamphiphilic SiO2-TiO2 porous nanofibrous membranes (STPNMs) comprised of intrafiber mesopores and interfiber macropores are modified by an amino-silanization reaction, which affords the membrane (ASTPNMs) the ability to simultaneously remove the oil contaminants and the water-soluble heavy-metal ions from wastewater. The underwater superoleophobicity of ASTPNMs facilitates the highly efficient separation of water and various oils, even emulsifier-stabilized emulsion. Meanwhile, an optimal modification time (15 min, ASTPNM-15) is important for maintaining the under-oil superhydrophilicity of the membrane, based on which the oil contaminant in membrane can be easily cleaned by water alone, showing excellent self-cleaning performance. The adsorption of Pb2+ over ASTPNM-15 reaches equilibrium at around 20 min, and the monolayer adsorption capacity is 142.86 mg g-1 at pH = 5 at 20 °C. In the breakthrough processes, the permeation volume of ASTPNM-15 for the purification of Pb2+ (5 ppm, pH = 5) reaches 160 mL when the concentration of Pb2+ in the filtrate increases to 0.05 ppm. The separation efficiencies of ASTPNM-15 for simulated wastewater containing both oil spill and various heavy-metal ions (Pb2+, Cr3+, Ni2+) are larger than 99.5%. In addition, the separation capacity keeps stable over five purification-regeneration cycles without obvious decrease, proving excellent recyclability and reusability of ASTPNM-15 for practical applications.

Publisher Correction: Infused-liquid-switchable porous nanofibrous membranes for multiphase liquid separation.

In Table 1 of this Article, the third row in the furthest right column contains a typographical error and should read 'NH', rather than 'NM', corresponding to n-hexane as the infused liquid.

Infused-liquid-switchable porous nanofibrous membranes for multiphase liquid separation.

Materials with selective wettabilities are widely used for effective liquid separation in environmental protection and the chemical industry. Current liquid separation strategies are primarily based on covalent modification to control the membranes' surface energy, or are based on gating mechanisms to accurately tune the gating threshold of the transport substance. Herein, we demonstrate a simple and universal polarity-based protocol to regulate the wetting behavior of superamphiphilic porous nanofibrous membranes by infusing a high polar component of surface energy liquid into the membranes, forming a relatively stable liquid-infusion-interface to repel the immiscible low polar component of surface energy liquid. Even immiscible liquids with a surface energy difference as small as 2 mJ m-2, or emulsions stabilized by emulsifiers can be effectively separated. Furthermore, the infused liquid can be substituted by another immiscible liquid with a higher polar component of surface energy, affording successive separation of multiphase liquids.Separating immiscible liquids with small surface energy differences remains a challenge. Here, the authors develop a polarity-based strategy for the separation of multiphase mixtures of immiscible liquids, even those with surface energy differences as small as 2 mJ m-2.