ngxiao Li

Magnetic, Durable, and Superhydrophobic Polyurethane@Fe3O4@SiO2@Fluoropolymer Sponges for Selective Oil Absorption and Oil/Water Separation

Magnetic, durable, and superhydrophobic polyurethane (PU) sponges were fabricated by chemical vapor deposition (CVD) of tetraethoxysilane (TEOS) to bind the Fe3O4 nanoparticles tightly on the sponge and then dip-coating in a fluoropolymer (FP) aqueous solution. The sponges were characterized using scanning electron microscopy and other analytical techniques. The effects of CVD time of TEOS and FP concentration on wettability, mechanical properties, oil absorbency, and oil/water selectivity of the sponges were also investigated. The sponges exhibit fast magnetic responsivity and excellent superhydrophobicity/superoleophilicity (CAwater = 157° and CAoil ≈ 0°). The sponges also show very high efficiency in oil/water separation and could, driven by a magnet, quickly absorb floating oils on the water surface and heavy oils under water. Moreover, the PU@Fe3O4@SiO2@FP sponges could be used as membranes for oil/water separation and for continuous separation of large amounts of oil pollutants from the water surface with the help of a pump. The in turn binding of Fe3O4 nanoparticles, SiO2, and FP can also improve mechanical properties of the PU sponge. The sponges maintain the superhydrophobicity even when they are stretched with 200% strain or compressed with 50% strain. The sponges also show excellent mechanical stability, oil stability, and reusability in terms of superhydrophobicity and oil absorbency. The magnetic, durable, and superhydrophobic PU sponges are very promising materials for practical oil absorption and oil/water separation.

Durable superhydrophobic/superoleophilic PDMS sponges and their applications in selective oil absorption and in plugging oil leakages

A facile method for preparing porous polydimethylsiloxane (PDMS) sponges is reported. The PDMS sponges are fabricated by the polymerization of the PDMS prepolymer and a curing agent in dimethicone using NaCl microparticles as the hard templates. The porous structure of the PDMS sponges is controllable simply by regulating the weight ratio of prepolymer to dimethicone and the size of the NaCl microparticles. The PDMS sponges feature high compressibility and stretchability, excellent superhydrophobicity/superoleophilicity, as well as high chemical and thermal stability. The PDMS sponge can completely recover its original shape even after 50 cycles of 90% strain. The elongation at breaking the sponge is as high as 97%. The PDMS sponge is superhydrophobic with a water contact angle of 151.5° but can be easily wetted by oils. The sponge also exhibits excellent repellency to corrosive aqueous liquids. The flexibility and superhydrophobicity of the sponge remain unchanged even after keeping in liquid nitrogen or at 250 °C for 24 h. Long-term immersion in various organics has no obvious influence on superhydrophobicity, oil absorbency, or weight of the sponge. The PDMS sponge can selectively absorb a large amount of floating oils on the water surface and heavy oils under the water, and furthermore, is reusable. Moreover, the PDMS sponge swells quickly after the adsorption of oils, which makes it a promising material for plugging oil leakages.

Superwetting Double-Layer Polyester Materials for Effective Removal of Both Insoluble Oils and Soluble Dyes in Water

Inspired by the mussel adhesive protein and the lotus leaf, Ag-based double-layer polyester (DL-PET) textiles were fabricated for effective removal of organic pollutants in water. The DL-PET textiles are composed of a top superamphiphilic layer and a bottom superhydrophobic/superoleophilic layer. First, the PET textiles were modified with a layer of polydopamine (PDA) and deposited with Ag nanoparticles to form the PET@PDA@Ag textiles. The top superamphiphilic layer, formed by immobilizing Ag3PO4 nanoparticles on the PET@PDA@Ag textile, shows excellent visible-light photocatalytic activity. The bottom superhydrophobic/superoleophilic layer, formed by modifying the PET@PDA@Ag textile using dodecyl mercaptan, is mechanically, environmentally, and chemically very stable. The water-insoluble oils with low surface tension can penetrate both layers of the DL-PET textiles, while the water with soluble organic dyes can only selectively wet the top layer owing to their unique wettability. Consequently, the water-soluble organic contaminants in the collected water can be decomposed by the Ag3PO4 nanoparticles of the top layer under visible-light irradiation or even sunlight in room conditions. Thus, the DL-PET textiles can remove various kinds of organic pollutants in water including both insoluble oils and soluble dyes. The DL-PET textiles feature unique wettability, high oil/water separation efficiency, and visible-light photocatalytic activity.

Ultralight, compressible and multifunctional carbon aerogels based on natural tubular cellulose

Ultralight, compressible and multifunctional carbon aerogels (UCM aerogels) have broad potential applications in various fields including thermal insulation, oil absorption and electronics. However, the preparation of UCM aerogels has been proven to be very challenging. Herein, we report a novel approach for the fabrication of UCM aerogels by pyrolysis of aerogels composed of kapok fibers (KFs), a kind of natural cellulose with a tubular structure. Different from the frequently used freeze-drying approach, the wet KF aerogels can be dried directly in an oven without any shrinkage. The fascinating UCM aerogels feature ultralow density (∼1.0 mg cm−3), high compressibility, high electrical conductivity (0.1 S cm−1), excellent fire-resistance and very high absorption capacity (147–292 g g−1) for organic liquids. Furthermore, the UCM aerogels can be easily endowed with various other functions, e.g., magnetic responsivity and superhydrophobicity. The successful creation of the UCM aerogels may provide new insights into the design of UCM aerogels for various applications, as the UCM aerogels can be prepared via a very simple procedure.

Facile preparation of super durable superhydrophobic materials

The low stability, complicated and expensive fabrication procedures seriously hinder practical applications of superhydrophobic materials. Here we report an extremely simple method for preparing super durable superhydrophobic materials, e.g., textiles and sponges, by dip coating in fluoropolymers (FPs). The morphology, surface chemical composition, mechanical, chemical and environmental stabilities of the superhydrophobic textiles were investigated. The results show how simple the preparation of super durable superhydrophobic textiles can be! The superhydrophobic textiles outperform their natural counterparts and most of the state-of-the-art synthetic superhydrophobic materials in stability. The intensive mechanical abrasion, long time immersion in various liquids and repeated washing have no obvious influence on the superhydrophobicity. Water drops are spherical in shape on the samples and could easily roll off after these harsh stability tests. In addition, this simple dip coating approach is applicable to various synthetic and natural textiles and can be easily scaled up. Furthermore, the results prove that a two-tier roughness is helpful but not essential with regard to the creation of super durable superhydrophobic textiles. The combination of microscale roughness of textiles and materials with very low surface tension is enough to form super durable superhydrophobic textiles. According to the same procedure, superhydrophobic polyurethane sponges can be prepared, which show high oil absorbency, oil/water separation efficiency and stability.

Roles of silanes and silicones in forming superhydrophobic and superoleophobic materials

Inspired by the self-cleaning and water-repellent properties of plants and animals in the natural world, superhydrophobic and superoleophobic materials develop quickly, and are of great interest in academic and industrial areas. Although various chemicals have been used, silanes and silicones play very important roles in the preparation of superhydrophobic and superoleophobic materials. Approximately 25% of the literature about superhydrophobic and superoleophobic materials is based on silanes and silicones. Thus, we believe that an exhaustive literature review from the viewpoint of silane and silicone chemistry is now pertinent to give an overview of the recent progress about their roles in the preparation of superhydrophobic and superoleophobic materials. First of all, we hope to overview the roles of silanes and silicones in constructing micro-/nanostructures, decreasing the surface energy and/or as binders for the fabrication of superhydrophobic and superoleophobic surfaces. We will then focus on the roles of silanes and silicones in the formation of superhydrophobic and superoleophobic particles, sponges and aerogels. In the conclusions, we will summarize the roles of silanes and silicones in forming superhydrophobic and superoleophobic materials, and the challenges in the field. Overall, this review will hopefully help readers to use silanes and silicones dexterously in the design of novel superhydrophobic and superoleophobic materials.

Dopamine-mediated fabrication of ultralight graphene aerogels with low volume shrinkage

Large volume shrinkage and high temperature are frequently encountered problems during the preparation of graphene aerogels via hydrothermal reactions. Here we report the dopamine-mediated fabrication of ultralight graphene aerogels (UGAs) with low volume shrinkage via hydrothermal reactions at low temperature. The UGAs were fabricated by the hydrothermal reaction of the graphene oxide (GO)/dopamine colloidal solutions at 85 °C in the presence of dopamine followed by freeze-drying and pyrolysis. The interaction between GO and dopamine in the aqueous phase, the effects of various parameters on the formation of the UGAs, the roles of dopamine in hydrothermal reactions as well as the wettability and electrical conductivity of the UGAs were investigated using a wide range of analytical techniques. The GO concentration, dopamine concentration, and the temperature and time of the hydrothermal reaction have great influences on the formation of the UGAs. The addition of dopamine forms crosslinking points among the GO sheets and results in the partial reduction of GO in the hydrothermal reaction. In addition, the N atoms of dopamine were doped into the graphene sheets. The UGAs feature low volume shrinkage (8.3%), ultralow density (3.5 mg cm−3), excellent superhydrophobicity/superoleophilicity (CAwater ∼ 155.5° and CAoil ∼ 0°), very high absorbency for organic liquids (134.0–282.9 g g−1) as well as excellent fire retardant properties and high conductivity (3.07 S cm−1). All these merits make the UGAs very promising materials for absorption of organic pollutants, sensors, energy storage, etc.

Pressure-Sensitive and Conductive Carbon Aerogels from Poplars Catkins for Selective Oil Absorption and Oil/Water Separation

Multifunctional carbon aerogels that are both highly compressible and conductive have broad potential applications in the range of sound insulator, sensor, oil absorption, and electronics. However, the preparation of such carbon aerogels has been proven to be very challenging. Here, we report fabrication of pressure-sensitive and conductive (PSC) carbon aerogels by pyrolysis of cellulose aerogels composed of poplars catkin (PC) microfibers with a tubular structure. The wet PC gels can be dried directly in an oven without any deformation, in marked contrast to the brittle nature of traditional carbon aerogels. The resultant PSC aerogels exhibit ultralow density (4.3 mg cm-3), high compressibility (80%), high electrical conductivity (0.47 S cm-1), and high absorbency (80-161 g g-1) for oils and organic liquids. The PSC aerogels have potential applications in various fields such as elastomeric conductors, absorption of oils from water and oil/water separation, as the PSC aerogels feature simple preparation process with low-cost biomass as the precursor.

Palygorskite@Fe3O4@polyperfluoroalkylsilane nanocomposites for superoleophobic coatings and magnetic liquid marbles

Superoleophobic coatings and remotely controllable liquid marbles are of great interest in many fields. Here, we report the preparation of magnetic nanocomposites that can be used for the fabrication of superoleophobic coatings and magnetic liquid marbles from both water and organic liquids with surface tension as low as 22.85 mN m−1. The nanocomposites were prepared by growing Fe3O4 nanoparticles on the needle-like crystals of palygorskite (PAL) via modified solvothermal reduction reactions between FeCl3 and ethylene glycol, and then coated by hydrolytic condensation of 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) and tetraethoxysilane (TEOS). The nanocomposites were characterized using a wide range of electron microscopy and other analytical techniques. The growth of Fe3O4 nanoparticles on PAL not only provides magnetic responsivity, but also constructs a hierarchical micro/nanostructure. The coatings with tunable wettability and liquid marbles encapsulated with liquids of different surface tensions were obtained simply by controlling the surface topography and surface chemical composition, in other words, the volume ratio of PFDTES to TEOS. The superoleophobic coatings show high contact angles and low sliding angles for various organic liquids such as n-hexadecane, toluene, n-dodecane, etc. The liquid marbles feature excellent magnetic responsivity, high stability and a very thin layer of solid powder.

Compressible and conductive carbon aerogels from waste paper with exceptional performance for oil/water separation

Carbon aerogels are receiving great attention in academia and industry; however, the preparation of high performance carbon aerogels is challenging. Here, we report the preparation of compressible and conductive carbon aerogels (3C aerogels) from waste paper using a general “oxidation-oven drying-carbonization” method. The 3C aerogels are lightweight (23.6 mg cm−3) and show good electrical conductivity (0.051 S cm−1), high compressibility, superhydrophobicity/superoleophilicity and high oil absorption capacity (33–70 g g−1). The 3C aerogels can also be used for the removal of free oils in water via different approaches. Moreover, the 3C aerogels can be used for efficient gravity-driven separation of surfactant-stabilized water-in-oil emulsions and simultaneous adsorption of soluble organic pollutants in the emulsions, both in the water phase and in the oil phase. The 3C aerogels may also find applications in other fields including sensors and pressure-sensitive electronics. This work opens a new avenue for designing carbon aerogels with exceptional performance for oil/water separation.