Super-wetting and self-cleaning polyvinyl alcohol/sodium alginate nanofiber membrane decorated with MIL-88A(Fe) for efficient oil/water emulsion separation and dye degradation.

Membrane separation is considered an effective approach to water purification. Nevertheless, membrane fouling dramatically decreases the separation efficiency and lifetime of membranes, thus limiting its further development and application. Herein, a multifunctional self-cleaning MIL-88A(Fe) decorated polyvinyl alcohol/sodium alginate (MIL-88A(Fe)@PVA-SA) nanofiber membrane was prepared by electrospinning and in-situ growth methods for the separation of oil/water emulsions and photo-Fenton degradation of dyes. The membrane possesses superhydrophilicity with a water contact angle (WCA) of 0° and superoleophobicity with underwater oil contact angle (UCA) of 161.7°, and exhibits superior separation efficiency (>99.5 %) and permeation flux (1140-2455 L/m2/h) for different oil/water emulsions. Moreover, the membrane exhibited an outstanding photo-Fenton performance under visible light, with degradation efficiencies (~99.9 %) towards methylene blue (MB) and reactive red 24 (RR24) within 90 min. Importantly, the membrane can be easily regenerated by simple rinsing and photo-Fenton self-cleaning treatment. In this study, MIL-88A(Fe)@PVA-SA nanofiber membrane has a promising application in dye removal and oil/water separation, providing a new idea to develop novel membrane materials.

Investigation of Electrochemical Assisted Deposition of Sol-Gel Silica Films for Long-Lasting Superhydrophobicity.

Current methods for the protection of metal surfaces utilize harsh chemical processes, such as organic paint or electro-plating, which are not environment-friendly and require extensive waste treatments. In this study, a two-step approach consisting of electrochemical assisted deposition (EAD) of an aqueous silane solution and a dip coating of a low surface energy silane for obtaining a superhydrophobic self-cleaning surface for the enhanced protection of copper substrate is presented. A porous and hierarchical micro-nanostructured silica basecoat (sol-gel) was first formed by EAD of a methyltriethoxysilane (MTES) precursor solution on a copper substrate. Then, a superhydrophobic top-coat (E-MTES/PFOTS) was prepared with 1H,1H,2H,2H-Perfluorooctyltriethoxysilane (PFOTS) for low surface energy. The superhydrophobic coating exhibited anti-stain properties against milk, cola, and oil, with contact angles of 151°, 151.5°, and 129°, respectively. The EAD deposition potential and duration were effective in controlling the microscopic morphology, surface roughness, and coating thickness. The E-MTES/PFOTS coatings exhibited chemical stability against acids, bases, and abrasion resistance by sandpaper. The proposed 2-layer coating system exhibited strong chemical bonding at the two interfaces and provided a brush-like surface morphology with long-lasting superhydrophobicity. The developed method would provide an environment-friendly and expedient process for uniform protective coatings on complex surfaces.

Near-Interface Defects in Graphene/H-BN In-Plane Heterostructures: Insights into the Interfacial Thermal Transport.

Based on nonequilibrium molecular dynamics (NEMD) and nonequilibrium Green's function simulations, the interfacial thermal conductance (ITC) of graphene/h-BN in-plane heterostructures with near-interface defects (monovacancy defects, 585 and f5f7 double-vacancy defects) is studied. Compared to pristine graphene/h-BN, all near-interface defects reduce the ITC of graphene/h-BN. However, differences in defective structures and the wrinkles induced by the defects cause significant discrepancies in heat transfer for defective graphene/h-BN. The stronger phonon scattering and phonon localization caused by the wider cross-section in defects and the larger wrinkles result in the double-vacancy defects having stronger energy hindrance effects than the monovacancy defects. In addition, the approximate cross-sections and wrinkles induced by the 585 and f5f7 double-vacancy defects provide approximate heat hindrance capability. The phonon transmission and vibrational density of states (VDOS) further confirm the above results. The double-vacancy defects in the near-interface region have lower low-frequency phonon transmission and VDOS values than the monovacancy defects, while the 585 and f5f7 double-vacancy defects have similar low-frequency phonon transmission and VDOS values at the near-interface region. This study provides physical insight into the thermal transport mechanisms in graphene/h-BN in-plane heterostructures with near-interface defects and provides design guidelines for related devices.

Multi-Jet Electrospinning with Auxiliary Electrode: The Influence of Solution Properties.

Multiple jets ejection in electrospinning has been a major approach to achieving a high production rate of ultrafine fibers, also known as nanofibers. This work studies the effect of solution parameters-including dielectric constant, polarity, conductivity and surface tension-on the jet number and jet evolution in the auxiliary electrode electrospinning approach. The results show that it is easier to generate 2⁻6 jets with short stable jet length (1.7⁻6.9 mm) under low voltage (5.03⁻7.13 kV) when solutions have higher dielectric constant (32.2⁻78.6) and larger surface tension (31.8⁻41.29 mN/m). The influence of solution properties on stable jet length and the influence of applied voltage to produce multiple jets are discussed in detail. This work provides a new perspective for understanding jet evolution and mass production of nanofibers in electrospinning.