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Superhydrophobic self-floating carbon nanofiber coating for efficient gravity-directed oil/water separation
Abstract
The fabrication of a superhydrophobic carbon nanofiber (CNF) on various substrates (activated carbon fiber and glass) via a two-step process (plasma sputtering followed by chemical vapor deposition at a lower operating temperature of 300 °C) is reported, eliminating the need for multiple pre- and post-treatments with toxic chemicals (fluorine/Si-based chemicals, metal salts, and organic solvents). Entangled CNFs grown on the coated activated carbon fiber (ACF) and glass substrates showed superhydrophobicity with water contact angles of 146° and 156°, respectively. The superhydrophobicity of the coated substrate is attributed to its lower surface energy, more graphitic structure (lower ID/IG ratio) as observed by Raman spectroscopy, lower carbonization state ratio (sp³/sp² ratio) and restricted carbonyl (C=O) as analyzed by X-ray photo-electron spectroscopy, and hydroxyl functional groups (-OH) as shown by Fourier transform infrared spectroscopy. Coated substrates were found to be stable in both acidic and basic chemicals. The load carrying capacity of the deposited CNF was measured to be up to 153 times that of its own deposited weight. The coated ACF was used for oil/water separation and showed a separation efficiency of >99%. Thus, the as processed durable CNF coated substrates can potentially be used for many applications such as anti-wetting, corrosion resistance, support for floating aquatic micro-devices and oil-water separation applications.
... The surface presented outstanding chemical durability over a wider pH and hot water (95°C). The SHPY was well-maintained during an ultrasonication test for 300 min (Figure 11j) [248]. Xu et al. employed an SHPC CF sponge without any chemical modification for oil separation [247]. ...
... SHPC and SOPL CNF-based systems are also widely investigated that include CNF-coated activated CF [248], fluoroacrylic co-polymer-hollow-core CNF conductive film [251], CNF/PDMS nanocomposite prepared by vacuum filtration [254], CNF-PDMS foam [257], and CNF-reinforced PDMS deposited into MR pores via vacuum filtration [256]. A few works addressed SHPL and underwater SOPC membranes [260,261,268], and mesh [255]. ...
... SEM images of (e and f) coated CFs and (g and h) coated glass surfaces. CAs of the coated glass after (i) abrasion and (j) ultrasonication tests[248]. Reproduced with permission from ref.[248]; © 2017 The Royal Society of Chemistry. ...
Research and development on superhydrophobic carbon nanostructures and their nanocomposites have high industrial significance. Here, a comprehensive review of the topic is provided. Reported works on superhydrophobic surfaces and coatings of carbon nanotubes, nanofibres, nanospheres/nanothorns/others, nanodiamond, fullerene and their various nanocomposites with metals, ceramics, and polymers are described. Superhydrophobic nanostructured carbon soot, graphitic carbon, and others are also presented. The section on superhydrophobic graphene is presented concisely at the end. Reports in different application areas, including anti-corrosion, anti-icing, oil separation, anti-biofouling, and sensors, are discussed separately. Superoleophobic and superamphiphobic surfaces are also discussed.
... 1. Introduction: Carbon nanofibres (CNFs) have outstanding properties, such as high electrical conductivity, large surface areas, and high flexibility. Hence, they are widely used in a variety of areas, including electrocatalysts [1], lithium ion batteries [2], adsorbents for various oils [3], and filtration membranes for separation of oil/water mixtures [4]. So far, various synthetic approaches, including carbonisation [3], electrospinning [1], and electrolysis [5], have been investigated for the controlled synthesis of CNFs. ...
... So far, various synthetic approaches, including carbonisation [3], electrospinning [1], and electrolysis [5], have been investigated for the controlled synthesis of CNFs. Among them, chemical vapour deposition (CVD), where transition metals [such as nickel (Ni), cobalt (Co), copper (Cu), and their alloys] were usually utilised to catalyse growth of CNFs [4,[6][7][8][9][10], received considerable attentions, because of its advantages of easy operation and low cost. However, the transition metal catalysts were difficult to remove even after the multi-step work-up procedures as well as the use of toxic chemicals [11,12], thereby hindering applications of the CNFs. ...
... It has been reported that growth of CNFs, which was catalysed by Cu nanoparticles, could follow tip-growth mechanism [4]. Hence, in order to highlight the important role of bottom-growth mechanism in the fabrication of high-purity CNFs, we replaced nickel nitrates by copper nitrates, and then performed the same CVD and peeling processes. ...
The authors report a facile approach to high‐purity carbon nanofibres (CNFs), by performing chemical vapour deposition on aluminium foils loaded with metal (nickel or cobalt) nitrates, and then peeling the as‐grown CNFs off. The growth of CNFs was catalysed by metal nanoparticles and followed bottom‐growth mechanism, and the high‐purity CNFs were achieved due to detachment of CNFs from their underlying metal nanoparticles during the peeling process. This approach may pave a new way for the controlled and scalable synthesis of high‐purity carbon materials.
... Since the advent of electron microscopies, which allowed the discovery of the surface features that allow the superhydrophobic phenomenon in natural species, scientists have sought to engineer artificial superhydrophobic surfaces (Ge et al., 2020b;Liao et al., 2020;Shao et al., 2020). Mimicking of superhydrophobic surfaces has since been successfully achieved in labs worldwide, and this branch of biomimicry has found many applications such as self-cleaning materials, protection of building materials, corrosion resistance, anti-icing, drag reduction, biomedical, and separation of oil/water mixtures and emulsions Cho et al., 2017;Gao et al., 2017b;Siddiqui et al., 2017;Tang et al., 2017a;Zhang et al., 2017bZhang et al., , 2018bRen et al., 2018;Kang et al., 2020;Lu et al., 2020a,b;Nine et al., 2020;Zhu et al., 2020). Although separation of oil/water mixtures had been demonstrated successfully using superhydrophobic surfaces, the separation of emulsions is not so easy, as the oil droplets are uniformly distributed and often stabilized within the water phase. ...
... Superhydrophobic surfaces have been fabricated via two step fabrication of carbon nanofibers by plasma sputtering followed by chemical vapor deposition (CVD) at 300 • C to achieve superhdyrophobic properties (Siddiqui et al., 2017). This represents a route that does not involve complicated processing and avoids toxic chemicals. ...
... Similarly, CNF structure on glass can also be seen with an individual fiber of diameter of <100 nm (Figures 11H-J). The porous structure formed by CNF is supposed to entrap more air, thus increasing surface superhydrophobicity (Siddiqui et al., 2017). ...
Oil/water mixtures are a potentially major source of environmental pollution if efficient separation technology is not employed during processing. A large volume of oil/water mixtures is produced via many manufacturing operations in food, petrochemical, mining, and metal industries and can be exposed to water sources on a regular basis. To date, several techniques are used in practice to deal with industrial oil/water mixtures and oil spills such as in situ burning of oil, bioremediation, and solidifiers, which change the physical shape of oil as a result of chemical interaction. Physical separation of oil/water mixtures is in industrial practice; however, the existing technologies to do so often require either dissipation of large amounts of energy (such as in cyclones and hydrocyclones) or large residence times or inventories of fluids (such as in decanters). Recently, materials with selective wettability have gained attention for application in separation of oil/water mixtures and surfactant stabilized emulsions. For example, a superhydrophobic material is selectively wettable toward oil while having a poor affinity for the aqueous phase; therefore, a superhydrophobic porous material can easily adsorb the oil while completely rejecting the water from an oil/water mixture, thus physically separating the two components. The ease of separation, low cost, and low-energy requirements are some of the other advantages offered by these materials over existing practices of oil/water separation. The present review aims to focus on the surface engineering aspects to achieve selectively wettability in materials and its their relationship with the separation of oil/water mixtures with particular focus on emulsions, on factors contributing to their stability, and on how wettability can be helpful in their separation. Finally, the challenges in application of superwettable materials will be highlighted, and potential solutions to improve the application of these materials will be put forward.
... Commercially available alloys (AISI 1020 mild steel (MS), and magnesium-based alloy (AZ31)) are used as substrates. On the structural alloys, superhydrophobic CNF is grown through a novel two-step plasma sputter, accompanied by the chemical vapor deposition method used in our recently published research [49]. In brief, metal (Cu) catalyst is sputtered on structural alloys substrates for 40 min at a voltage of 500-700 V and current of 1-100 mA. ...
... Furthermore, acetylene gas is used as a source of carbon, which is decomposed to deposit superhydrophobic CNF using a novel lower operating temperature (~300°C) CVD approach. This new process excludes the intervention of various hazardous substances, such as silane-based substances, metal compounds, and solvents [49]. For details, Fig. S1 describes a schematic of steps involving for CNF deposit parameters over structural metals alloys via the CVD method. ...
Global corrosion damages mandate the synthesis of superhydrophobic, self-cleaning protective surfaces possessing excellent mechanical, chemical, and thermal stability. Thus, a self-cleaning, superhydrophobic carbon nanofiber (CNF) coating on structural alloys AISI 1020 mild steel (MS) and Mg alloy (AZ31) with water contact angle (CA) 145°-150°and sliding angle of 7°± 2°is fabricated by a novel two-step process of plasma sputter followed by CVD. An extraordinary self-buoyancy of the deposited CNFs coating was observed to be~378 and 257 times than that of its own deposited mass on the coated MS and AZ31, respectively. Further, the CNF coated MS, and AZ31 alloys displayed performance of corrosion protection efficiency of about 97% in 3.5 wt NaCl corrosive environment with a lower corrosion current density (I corr = 0.16 and 14.90 μA/cm 2 respectively) than that of uncoated one (I corr = 5.56 and 691.8 μA/cm 2 , respectively). The charge transfer resistance (R ct) was obtained to be~four and two orders of magnitude greater than the uncoated MS (1.4 kΩ cm 2) and AZ31 (2.0 kΩ cm 2) alloys, respectively. Thus, this simple and straightforward process of making corrosion resistance superhydrophobic CNF coating can be potentially used for protecting structural alloys in various engineering applications.
... Hence, there is a great necessity to provide an effective and speedy way to purify polluted water as its scarcity is now a crucial problem of our world. Cotton fabrics [127], non-woven fabrics [128], wood cellulose nanofibers [129], melamine sponges [53], aerogels [46] and activated carbon fibres [130] are common oil-absorbing materials which can be effectively utilized in cleaning and collecting crude oil. However, due to their high hydrophilicity, poor oil/water selectivity, low oil/water separation efficiency and difficulty of reuse [131], these measures cannot provide a satisfactory solution. ...
... crucial problem of our world. Cotton fabrics [127], non-woven fabrics [128], wood cellulose nanofibers [129], melamine sponges [53], aerogels [46] and activated carbon fibres [130] are common oil-absorbing materials which can be effectively utilized in cleaning and collecting crude oil. However, due to their high hydrophilicity, poor oil/water selectivity, low oil/water separation efficiency and difficulty of reuse [131], these measures cannot provide a satisfactory solution. ...
The commercial availability of inorganic/organic precursors for sol-gel formulations is very high and increases day by day. In textile applications, the precursor-synthesized sol-gels along with functional chemicals can be deposited onto textile fabrics in one step by rolling, padding, dip-coating, spraying or spin coating. By using this technology, it is possible to provide fabrics with functional/multi-functional characteristics including flame retardant, anti-mosquito, water- repellent, oil-repellent, anti-bacterial, anti-wrinkle, ultraviolet (UV) protection and self-cleaning properties. These surface properties are discussed, describing the history, basic chemistry, factors affecting the sol-gel synthesis, progress in sol-gel technology along with various parameters controlling sol-gel technology. Additionally, this review deals with the recent progress of sol-gel technology in textiles in addressing fabric finishing, water repellent textiles, oil/water separation, flame retardant, UV protection and self-cleaning, self-sterilizing, wrinkle resistance, heat storage, photochromic and thermochromic color changes and the improvement of the durability and wear resistance properties.
... Importantly, thus prepared aligned CNFs remained near-superhydrophobic even at higher temperature, i.e. up to 80 • C, with WCA in the range from 149.5 ± 1.4 • to 153.1 ± 2.2 • . In turn, entangled CNFs, prepared via CVD, deposited either on the activated carbon or glass substrate, yielded WCA of 156 • and 146 • , respectively, while WCA for activated carbon fabric and glass substrate was 0 • and 36 • [92]. Crucially, WCA of CNF-coated glass was almost unchanged after abrasion cycles by different grift size SiC sand paper. ...
... The treated cotton fabric sample was assessed for contact angle measurement with water using the goniometer (DSA 100, Kruss, Germany) sessile drop technique. 5 μL of water was dropped at points on the sample in five places, at room temperature (Siddiqui et al. 2017). The average value of contact angles was used. ...
C6-Fluorocarbon-dendrimer has been applied to the cotton knit fabric to develop oil–water repellent, oil–water separation, acid-resistant, self-cleaning, UV-resistant, and antibacterial properties. The C6-Fluorocarbon (FC)-dendrimer-coated 100% cotton single jersey knitted fabric samples were prepared using the “pad-dry-cure” method. The 90 g/L and 100 g/L FC-dendrimer-treated cotton fabrics showed excellent water repellency and oil–water separation as well as good self-cleaning performance. However, air permeability and heat conductivity were reduced by 13%, 15%, and 40%, 54%, for 90 g/L and 100 g/L FC-dendrimer-treated cotton fabrics compared to untreated fabrics. The presence of FC-dendrimer in the treated fabric was confirmed by FTIR, SEM, EDX, and XRD analyses. SEM analysis was employed to study the morphology of deposited FC-dendrimer particles on the fabric surface. TGA and DTA evaluated thermal performance. The FC-dendrimer-treated fabric also showed acid resistance, self-cleaning performance, and UV resistance attribute. In addition, Bacterial population growth appears to be less in the FC-dendrimer-treated sample than in the untreated sample. Overall, the result suggests that FC-dendrimer can be a valuable ingredient in the manufacture of multifunctional products.
Graphical abstract
... The nished cotton sample was assessed for contact angle measurement with water using the goniometer (DSA 100, Kruss, Germany) sessile drop technique. 5μLof water, by volume, was dropped at points on the sample in ve places, at room temperature (Siddiqui et al. 2017). The average value of contact angles was used. ...
C6-Fluorocarbon-dendrimer has been applied to the cotton knit fabric to develop oil-water repellent, oil-water separation, acid-resistant, self-cleaning, flame retardant, UV resistant, and antibacterial properties. The C6-Fluorocarbon (FC)-dendrimer-coated 100% cotton single jersey knitted fabric samples were prepared using the “pad-dry-cure” method. The 90 g/L and 100 g/L FC-dendrimer-treated cotton fabrics showed excellent water repellency and oil-water separation as well as good self-cleaning performance. However, air permeability and heat conductivity were reduced by 13%, 15%, and 40%, 54%, for 90 g/L and 100 g/L FC-dendrimer-treated cotton fabrics compared to untreated fabrics. The presence of FC-dendrimer in the treated fabric was confirmed by FTIR, SEM, EDS, and XRD analyses. SEM analysis was employed to study the morphology of deposited FC-dendrimer particles on the fabric surface. TGA and DTA evaluated thermal performance. The FC-dendrimer-treated fabric also showed acid resistance, self-cleaning performance, and UV resistant attribute. In addition, Bacterial population growth appears to be less on the FC-dendrimer-treated sample than on the untreated sample. Overall, the result suggests that FC-dendrimer can be a valuable ingredient in the manufacture of multifunctional products.
... To restore θY the roughness factor r was measured as described in Section III.C.3. To find the polar and dispersive components, the analysed solid surface (2.9) should be represented by a linear function y = mx + b[50][51][52] , where: versus x, using mentioned liquids and their contact angles, one could find the polar and dispersive components of the solid from the linear trendline linking all the plotted data. The standard Excel function LINEST was used to obtain the trendline and its equation using the least-squares method. ...
In this work, micro-milling and laser-etching microfabrication techniques are trialled for mimicking the super water repellence of the lotus leaf and the directional water droplet control of the Namib desert beetle. To further alter the surface wetting properties, subsequent ion-beam surface modification techniques are used. Ion-beam post-processing is used to create an additional nanoroughness on a microstructure as well as a controllable Gibbs surface free energy change of the substrate material. The in-plane spreading for control (smooth) surfaces are compared to the micro-patterned surfaces and combined micro-patterned and ion-beam processed surfaces. 2 Combined, micro-scale surface engineering via milling or laser etching, and ion-beam surface modification allows engineering both hydrophobic and mass-transport properties directly from a bulk material rather than involving a coating. Such surfaces have potential applications in advanced heat-exchanger technology (increasing the condensation heat transfer coefficient), wind turbine technologies (delaying or eliminating ice/frost formation under extreme weather conditions), as well as for atmospheric water harvesting and condensation control on industrial heat exchangers.
... The most important factors that affect the hydrophobic properties of the surface are increases in the surface roughness and decreases in the surface energy [4][5][6]. Thus, the methods applied for manufacturing a hydrophobic surface are etching [7], lithography [8,9], chemical vapor deposition [10], chemical and electrochemical deposition [11,12], anodizing [13,14], plasma treatment [15][16][17], sandblasting [18], phase separation [19], the sol-gel process [20,21], and layer-by-layer assembly [22,23], among others. However, most of the above methods require multiple steps to complete, or require expensive equipment; they are not economical in practice for industrial applications. ...
Nanosilica-modified, fluorine-containing polyacrylate hybrid coating materials, consisting of dodecafluoroheptyl methacrylate (DFMA), methyl methacrylate (MMA), 2-ethyl hexyl acrylate (2-EHA), 3-(trimethoxysilyl) propyl methacrylate (KH-570), and tetraethylorthosilicate (TEOS), are synthesized successfully by free radical polymerization and the sol–gel process. It is revealed that the content of the fluorine-containing polyacrylate hybrid coating materials from DFMA monomers significantly improves the properties of the films. The polyacrylate coating film prepared with a weight ratio of DFMA/MMA at 1:5 exhibits the largest water contact angle of 105.4°, which demonstrates that DFMA can effectively improve the hydrophobicity of the coating film. Moreover, the silicon coupling agent (KH-570) is used to graft silica with acrylate. Spherical in shape, the surface morphology of the nanohybrid film exhibits a core–shell structure, which increases the surface roughness and enhances the hydrophobic properties. The as-prepared fluorine-containing nanohybrid silica polyacrylate film possesses a high transmittance of 89–97% in the visible light region, indicating its potential as a very attractive solution in many practical areas.
... The height and diameter of the water drop were recorded using a drop-shaped analyzer (DSA25B; Kruss, Hamburg, Germany). The contact angle (CA) value between the water drop and the PMC surface was calculated as mentioned elsewhere (Alam, Kumar, and Patel 2015;Kanhed et al. 2017;Abdul Rahim;Siddiqui, Riya, and Kantesh 2017). The water drop was placed at five points on each PMC sample and the average was taken in for further studies. ...
Flax fiber-containing polypropylene-based polymer matrix composites 10 (PMCs) with different lignite fly ash (LFA) contents were synthesized using the formula (80 − x) PP − 20 F – x LFA (where x = 0, 2.5, 5.0, 7.5, and 10.0 wt.%) and analyzed. The added LFA acted as a filler material in the polymer network to re-formulate the microstructure of PMCs. The structural changes in the PMCs were induced to alter their thermal stability and mechanical strength. 15 A linear increase in Tg, density, and compressive strength values was observed up to addition of 10 wt.% LFA in the prepared PMCs. Fourier transform infrared spectra revealed the structural changes that occurred in the polymer network for all the samples during the addition of LFA. Results of the X-ray diffraction studies confirmed the crystalline phase of the added LFA 20 in the PMCs. Contact angle and surface energy studies showed a higher contact angle and lower surface energy in the PMC sample containing 5 wt.% LFA. The low wear depth in the sample containing 5 wt.% LFA confirmed its better wear than other samples. The obtained results confirmed that the flax fiber-added polypropylene composite with 5 wt.% LFA is suitable for aero- 25 space, construction, and automobile applications.
... The height and diameter of the water drop were recorded using a drop-shaped analyzer (DSA25B; Kruss, Hamburg, Germany). The contact angle (CA) value between the water drop and the PMC surface was calculated as mentioned elsewhere (Alam, Kumar, and Patel 2015;Kanhed et al. 2017;Abdul Rahim;Siddiqui, Riya, and Kantesh 2017). The water drop was placed at five points on each PMC sample and the average was taken in for further studies. ...
Flax fiber-containing polypropylene-based polymer matrix composites (PMCs) with different lignite fly ash (LFA) contents were synthesized using the formula (80 − x) PP − 20F – x LFA (where x = 0, 2.5, 5.0, 7.5, and 10.0 wt.%) and analyzed. The added LFA acted as a filler material in the polymer network to re-formulate the microstructure of PMCs. The structural changes in the PMCs were induced to alter their thermal stability and mechanical strength. A linear increase in Tg, density, and compressive strength values was observed up to addition of 10 wt.% LFA in the prepared PMCs. Fourier transform infrared spectra revealed the structural changes that occurred in the polymer network for all the samples during the addition of LFA. Results of the X-ray diffraction studies confirmed the crystalline phase of the added LFA in the PMCs. Contact angle and surface energy studies showed a higher contact angle and lower surface energy in the PMC sample containing 5 wt.% LFA. The low wear depth in the sample containing 5 wt.% LFA confirmed its better wear than other samples. The obtained results confirmed that the flax fiber-added polypropylene composite with 5 wt.% LFA is suitable for aerospace, construction, and automobile applications.
... In addition to that, the amorphous carbon materials, which displays superhydrophobic surface, low surface energy and tuneable topology, which can be found in various morphologies; such as fiber [50], nanotubes [51], composite membranes [52], thin sheet/film [53], foam [54,55], sponges [56], etc., are explored for oil/water separation. In general, powdered amorphous carbon materials are widely used for the sorption process, due to their easy preparation (or) vast availability. ...
Oil/water separation receives increasing interest as the oil contaminants level has been continuously increasing in the water resources in most of parts in the world and is being considered as a severe environmental threat to the society. As the result, a wide range of methods have been investigated in order to minimize the oil-based contaminants (including non-polar organic solvents which are immiscible with water) in water resources, in which sorption process has been widely accepted owing to their easy handling, low-cost, harmless and efficient large-scale approach. Out of the sorbents explored, carbon-based materials gained more interest in oil/water separation because of their superior physiochemical properties as well as structural advantages. The recent advancement in the carbon-based oil/water separation technology is the exploration of various renewable resource based biocarbon materials as green and sustainable approach and their modifications to enhance their sorption properties. The advantages of renewable based biocarbon materials are vast availability and diversity of renewable resources with wide-range of chemical compositions, tuning/predicting the structures by choosing the specific precursors and flexible structure/chemical modifications to improve the properties. Thus, the present review deals with the reported biocarbon-based hydrophobic/oleophilic materials such as biochar, activated biocarbon, biocarbon fibers, biocarbon aerogels and biocarbon-based composite materials as sorbents for oil/water separation, as well as oil spill up from water resources. In detail, various synthesis procedures of biocarbon materials and their physio-chemical characteristics (hydrophobicity/oleophilicity, wettability, water/oil contact angle, etc.) are discussed in this review.
... To obtain a non-wetting surface, the use of nanoparticles, nano-tubes, nano-wires and other nanomaterials may well serve the purpose of creating microstructures with nano-roughness. Hence, general wet chemical synthesis methods were naturally employed, like chemical vapour deposition (CVD), [278][279][280][281][282] hydrothermal, [283][284][285][286][287] and solgel. [288][289][290][291][292][293] It is worth noting that, most of the time, the nanomaterial synthesis is only a single step of the overall multi-step fabrication process. ...
Superhydrophobic surfaces hold great prospects for extremely diverse applications owing to their water repellence property. The essential feature of superhydrophobicity is micro-/nano-scopic roughness to reserve a large portion of air under a liquid drop. However, the vulnerability of the delicate surface textures significantly impedes the practical applications of superhydrophobic surfaces. Robust superhydrophobicity is a must to meet the rigorous industrial requirements and standards for commercial products. In recent years, major advancements have been made in elucidating the mechanisms of wetting transitions, design strategies and fabrication techniques of superhydrophobicity. This review will first introduce the mechanisms of wetting transitions, including the thermodynamic stability of the Cassie state and its breakdown conditions. Then we highlight the development, current status and future prospects of robust superhydrophobicity, including characterization, design strategies and fabrication techniques. In particular, design strategies, which are classified into passive resistance and active regeneration for the first time, are proposed and discussed extensively.
... The wettability of a surface is quantified by the contact angle which is a function of the physical and chemicals properties of the surface. Several microfluidic systems with patterned surface wettability are reported in the literature to perform specific functions [1][2][3][4][5][6]. The reported microdevices can be classified into two main groups. ...
... Researchers have sought to exploit floating materials for certain applications such as photocatalysis [20,21] and adsorbent technology [22], in which the active compound is anchored to a floating substrate. Some of the compounds with a density lower than unity or hydrophobic properties [23] have intrinsic floating properties and are known as self-floating (SF) materials [24,25]. Having the ability of quick flotation to the surface or near the surface of the water, the SF materials could be excellent solutions to the inherent shortcomings of the batch process. ...
In solid phase extraction method, the adsorbent separation is very challenging and is one of the limiting factors for using batch process. As a solution to this problem, a self-floating (SF) adsorbent with simultaneous separation from water is developed in this study. The adsorbent has a very high performance for extracting and recovery of the rare-earth element (REEs), especially Yb³⁺, which has not been reported by other organic adsorbents, so far. The designed adsorbent is very low cost and can be easily prepared by using alkyl ketene dimer (AKD) as a commonly used sizing agent in pulp and paper industry. The designed polymer was used to remove La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Dy³⁺, and Yb³⁺ from aqueous solutions. The adsorption of the ions showed that REEs with smaller ionic radii have more tendencies towards the AKD-based vinylogous amide-diglycolamic acids self-floating (AVD-SF) polymer with the highest adsorption of 191.87 mg.g⁻¹ for Yb³⁺ ions at pH = 5.5. The adsorption isotherm of Yb³⁺ ions fitted with Freundlich model and the kinetics isotherm fitting confirmed the pseudo-second order model. The SF adsorbent was easily separated from water within 30 min. The reusability test showed that both the performance and structure are reserved after 10 cycles.
... Carbon materials have always been a popular material and are widely used in various studies [21][22][23][24][25]. It is an important method to prepare superhydrophobic sponges by using nano-carbon materials to construct rough structures on sponges. ...
Flexible porous composites, as sorbent materials with shape recoverability and excellent adsorption capacity, have always attracted many attentions in these years. In order to endow the sponge with selective adsorption, the sponge needs to be prepared as a superhydrophobic material. In this paper, the nano-graphite flakes were adhered to the melamine sponge by polydimethylsiloxane, and then the sponge was silanized with hexadecyltrimethoxysilane to prepare a superhydrophobic conductive sponge. The prepared sponge has excellent adsorption capacity for oil and organic solvent. It can not only absorb 24–40 g of organic solvent per gram of sponge, but also absorb oil in the oil-in-water emulsion. After the emulsion separation, the COD value of the emulsion can be reduced to 260 mg/L. Even after hundreds of adsorption-extrusion cycles, it can still maintain more than 92% of the adsorption capacity for organic solvents. In addition, its electrical conductivity makes it having potential application for pressure sensors. After adsorbing different organic solvents, the composite exhibits particular current changes and can be used as a sensor for organic solvents to detect the presence of different types of organic solvents.
... 1−6 In recent years, surfaces with extreme wettability have attracted the attention of researchers working in the area of separation. 7,8 Several studies have investigated the use of superhydrophilic/superhydrophobic surfaces, and alternating between them, for the phase separation of liquid−liquid two-phase systems with emphasis on the separation of oil/water systems. 1,8−10 This is mainly due to their potentially high performance in industrial and environmental applications such as separation of entrained water from water-contaminated fuel oil and treatment of oilcontaminated wastewater, where the latter is a serious problem faced by the petroleum industry. ...
This article presents a simple method to pattern the surface energy of a substrate using standard microfabrication techniques. Microfluidic devices with hydrophobic polymer substrate patterned with hydrophilic graphene oxide (GO) for the separation of liquid-liquid two-phase systems are reported. The microdevice consists of a Cyclic Olefin Copolymer (COC) substrate bonded to a Polydimethylsiloxane (PDMS) element that includes a microchannel. The patterned GO film is characterized using scanning electron, atomic force, and metallurgical microscopies. The contact angle of water on COC surface is measured to be more than 120° and is approximately 10° on the GO-patterned COC surface. Different contact angles could be achieved by tuning the GO with oxygen containing functional groups as well as using different concentrations of GO dispersions. The device is used to separate dye-water droplets dispersed in silicone oil by steering the water droplet toward a designated outlet and achieve separation. Using GO as a patterned thin film with tunable hydrophilicity allows for on-chip continuous full separation of water droplets at different flow rates.
... 34 A common way for fabrication of micro-scale superhydrophobic textiles is to decorate the F I G U R E 1 Schematic of electrospinning process for the filter preparation F I G U R E 2 The dip-coating process for preparing the superhydrophobic nanofibrous filters surface of fibers with nanoparticles to obtain nanostructuremicrostructure and posttreatment of them by using fluorinated reagents. 35 Up to now, several methods have been employed to fabricate superhydrophobic filters including, self-assembly, 36 templatebased synthesis, 37 sol-gel, 38 plasma treatment, 39 chemical etching, 40 hydrothermal method, 41 and others. 42 Preroughening the surface of microfibers and post-fluorination of them have been utilized for the fabrication of superhydrophobic cellulosic textiles commonly. ...
Three reusable and durable superhydrophobic nanofibrous filters were prepared by dip coating the nanofibrous fabric in the three different dispersed solutions of the newly modified nanoparticles (ZnO‐NSPO, AlOO‐NSPO, and titanium dioxide [TiO2]‐NSPO). The contact angle results proved that the TiO2‐NSPO coated nanofibrous polyacrylonitrile (PAN) filter was hydrophobic with the water contact angle (WCA) of 141° while the ZnO‐NSPO and AlOO‐NSPO coated nanofibrous PAN filters were superhydrophobic with the WCA of 168° and 152°, respectively. The as‐prepared filters can be utilized as an effective martial for oil‐water separation with separation efficiency of over 98%.
... Compared to bulk material, nanoscale ZnO possesses more active sites and is positively charged in acidic solutions, facilitating the sorption of negatively charged anions (Chouchene et al., 2017). Furthermore, the ZnO nanoparticle exhibits decent radioresistance and hydrophobicity due to its wide range of morphologies and low surface energy, which are expected to enhance its sorption selectivity and efficiency towards TcO 4 - (Banerjee et al., 2016a;Shen et al., 2017;Radu, 2013;Siddiqui et al., 2017;Boyer et al., 2017). In this regard, hybridizing carbon-based materials with ZnO nanoparticles to produce high-performance composites for contaminant remediation has drawn much attention (Moussa et al., 2016;Sharma et al., 2019;Yu et al., 2018). ...
Pertechnetate (TcO4-) is a component of low-activity waste (LAW) fractions of legacy nuclear waste, and the adsorption removal of TcO4- from LAW effluents would greatly benefit the site remediation process. However, available adsorbent materials lack the desired combination of low cost, radiolytic stability, and high selectivity. In this study, a ZnO nanoparticle-anchored biochar composite (ZBC) was fabricated and applied to potentially separate TcO4- from radioactive effluents. The as-synthesized material exhibited γ radiation resistance and superhydrophobicity, with a strong sorption capacity of 25,916 mg/kg for perrhenate (ReO4-), which was used in this study as a surrogate for radioactive pertechnetate (TcO4-). Additionally, the selectivity for ReO4- exceeded that for the competing ions I-, NO2-, NO3-, SO42-, PO43-, Cu2+, Fe3+, Al3+, and UO22+. These unique features show that ZBC is capable of selectively removing ReO4- from Hanford LAW melter off-gas scrubber simulant effluent. This selectivity stems from the synergistic effects of both the superhydrophobic surface of the sorbent and the inherent nature of sorbates. Furthermore, density functional theory (DFT) calculations indicated that ReO4- can form stable complexes on both the (100) and (002) planes of ZnO, of which, the (002) complexes have greater stability. Electron transfer from ReO4- on (002) was greater than that on (100). These phenomena may be because (002) has a lower surface energy than (100). Partial density of state (PDOS) analysis further confirms that ReO4- is chemisorbed on ZBC, which agrees with the findings of the Elovich kinetic model. This work provides a feasible pathway for scale-up to produce high-efficiency and cost-effective biosorbents for the removal of radionuclides.
... Superhydrophobic/superoleophilic materials have proven to be particularly useful for efficient separation of organic pollutants and oil from water and encouraging results have been obtained [4][5][6][7][8]. However, the use of expensive reagents and complicated processes always hampers their wider application. ...
Regular problems faced due to chemical leaks and oil spills have caused tremendous threats to lakes and sea water. Therefore, there is an urgent need to develop efficient strategies to remove oil and organic pollutants from water surfaces. The aim of this study is to develop a high performance magnetic, superhydrophobic/superoleophilic three-dimensional porous composite material for efficient and selective adsorption of organic pollutants from water. The composite material was fabricated by simple immersion of a commercially available polyurethane (PU) sponge into a solution of high-density polyethylene (HDPE) containing pre-synthesized magnetic (Fe3O4) nanoparticles. The composite material exhibited a water contact of ~155° and an oil contact angle of ~0°. The presence of the Fe3O4 particles allowed magnetic-controlled elimination of underwater oil, while the superhydrophobic character of the functionalized PU sponge permitted efficient separation of oil/water mixtures and demulsification of toluene/water emulsions. Moreover, the HDPE coating not only firmly immobilized the magnetic particles, but also contributed to the excellent stability of the composite sponge which withstood acid, base, salts, seawater or temperature variation from −20 °C to 105 °C. In addition, the composite material maintained its oil adsorption ability over 10 cycles. The ease of fabrication of the magnetic super wetting 3D material sponge along with its durability and reusability makes it an interesting material with potential for practical applications.
The increasing demand for efficient and sustainable oil/water separation technologies has driven significant research into advanced materials capable of addressing environmental and industrial challenges. Hybrid nanostructures have emerged as a transformative solution, offering exceptional performance by synergistically combining diverse materials to create tailored interfaces with specialized wettability. These hybrid systems not only enhance oil/water separation but also provide multifunctional benefits such as self-cleaning, dye removal, anti-fouling, and antibacterial properties. This review highlights the latest advancements in hybrid nano-architectures, focusing on their design principles, fabrication techniques, and multifunctional applications. A broad range of nanomaterials, including metal nanoparticles, metal-oxide-based nanomaterials, silica-based nanomaterials, carbon-based nanomaterials, polymeric materials, porous frameworks-based materials including metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), at last MXene-based materials, are explored for their role in creating super-wettable surfaces optimized for oil/water separation. These materials possess unique properties such as high surface area, tunable wettability, and enhanced stability, all crucial for improving separation efficiency. The review emphasizes the importance of material chemistry and structural design in achieving higher separation efficiency, durability, and scalability. It also discusses innovative fabrication strategies, performance benchmarks, and real-world applications. Building on individual materials, hybrid nanostructures combine the strengths of different components to create interfaces with enhanced functionalities. Systems like metal-metal oxide composites, carbon-metal hybrids, polymer-inorganic hybrids, and MXene-based heterostructures exhibit synergistic effects that significantly outperform single-material systems. In addition to superior oil/water separation, these hybrids offer added capabilities such as self-cleaning, anti-fouling, dye removal, and antibacterial properties. By focusing on the transformative potential of these materials, this review highlights their critical role in revolutionizing oil/water separation technologies and catalyzing interdisciplinary innovations in multifunctional materials.
Inspired by the surface structure of rice leaf, the eco-friendly polycaprolactone-carbon black/SiO2 (PCL-C/SiO2) membrane with oriented arrangement was successfully prepared. The oriented arrangement of PCL fiber was realized by doping...
Superhydrophobic textiles with multifunctional characteristics are highly desired and have attracted tremendous research attention. This research employs a simple dip-coating method to obtain a fluorine-free silica-based superhydrophobic and superoleophilic cotton fabric. Pristine cotton fabric is coated with SiO2 nanoparticles and octadecylamine. SiO2 nanoparticles are anchored on the cotton fabric to increase surface roughness, and octadecyl amine lowers the surface energy, turning the hydrophilic cotton fabric into superhydrophobic. The designed cotton fabric exhibits a water contact angle of 159° and a sliding angle of 7°. The prepared cotton fabric is characterized by attenuated total reflectance-fourier transform infrared spectroscopy, X-ray diffraction, atomic force microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. In addition, the coated fabric reveals excellent features, including mechanical and chemical stability, superhydrophobicity, superoleophilicity, and the self-cleaning ability. SiO2 nanoparticles and octadecylamine-coated cotton fabric demonstrate exceptional oil–water separation and wastewater remediation performance by degrading the methylene blue solution up to 89% under visible light. The oil–water separation ability is tested against five different oils with more than 90% separation efficiency. This strategy has the advantages of low-cost precursors, a simple and scalable coating method, enhanced superhydrophobicity and superoleophilicity, self-cleaning ability, efficient oil–water separation, and exceptional wastewater remediation performance.
Superhydrophobic coatings have attracted substantial scientific research in recent years due to their real-world applications in a variety of fields including anti-corrosion, anti-icing, anti-fogging, oil separation and self-cleaning materials.
Several approaches and methods have been used in developing superhydrophobic coatings on different substrates. This book guides readers through their fabrication and application, representing the latest significant advances in this important topic.
Split into four sections, Part One concentrates on the fundamental principles of surface wettability and superhydrophobicity, before moving into Part Two and Part Three, which focus on different aspects of superhydrophobic coatings based on the materials used for fabrication and the substrate on which the coating is applied. Finally, Part Four focuses on the applications of these coatings.
This book will serve as a valuable reference for graduate students, researchers and industrial practitioners in multiple industries working on surface wettability, materials chemistry and coatings related technologies.
Endüstriyel organik çözücü emisyonlarının ve petrol sızıntılarının sık görülmesi ile yüksek verimli yağ-su ayırma malzemelerinin geliştirilmesi büyük önem kazanmıştır. Bu çalışmada, yağ-su ayırma için polikaprolakton/polihidroksibütirat (PCL/PHB) nanolifli matlar paslanmaz çelik elek yüzeyler üzerinde tek basamaklı elektroeğirme yöntemi ile başarılı bir şekilde üretildi. Elde edilen biyobazlı lifli matların yüzey morfolojisi Alan Emisyonlu Taramalı Elektron mikroskopisi (FE-SEM) ile analiz edildi. Ayrıca hazırlanan tüm örneklerinin kimyasal yapılarını açığa çıkarmak ve ıslanma özelliklerini incelemek için Fourier Dönüşümlü Kızılötesi spektroskopisi (FT-IR) ve temas açısı ölçüm cihazı kullanıldı. Hazırlanan yeşil PCL/PHB nanolifli membranların ıslanabilirliği üzerine yapılan çalışmalar, membran yüzeylerinin mükemmel hidrofobik ve süperoleofilik özelliğe sahip olduklarını gösterdi. Ölçülen su temas açısı değerleri biyopolimer katkı oranlarına ve elek boyutuna bağlı olarak değişkenlik gösterdi. Paslanmaz çelik elekler üzerinde elde edilen PCL/PHB biyokompozit nanofiber matların maksimum su temas açısı değeri 144.8° olarak ölçülürken yağ temas açısı değeri ise sıfıra yakın olarak ölçüldü. Çelik elekler üzerinde elde edilen hidrofobik ve süperoleofilik PCL/PHB biyonanolifli membranlar doğrudan yerçekimi güdümlü yağ-su ayrımı için kullanıldı ve ekstra herhangi bir kuvvet veya kimyasal reaktif kullanmaksızın ağ boyutuna ve biyopolimer karışım oranlarına bağlı olarak en yüksek %97.4 'lük yüksek bir ayırma verimliliği değeri gözlendi.
The design and application of multi-functional membrane materials capable of realizing one-step efficient treatment of complex polluted media have been developed into one of the effective solutions to solve the waste liquid with complex working conditions, which can simplify the treatment steps and reduce the treatment cost. Herein, a kind of dual-functional tubular PVC/SiO2/SiO2@Ag nanofiber membrane integrated the functions of oil/water separation and dyes catalytic degradation was prepared via electrospinning process, with the tubular PVC/SiO2 nanofiber membrane as matrix and functionalized SiO2@Ag nanoparticles as inorganic additives. The prepared PVC/SiO2/SiO2@Ag nanofiber membrane contained a three-dimensional hydrophobic structure and SiO2@Ag ultrathin catalytic layer, which could achieve the synergistic effect to endow the as-prepared nanofiber membrane with simultaneous oil/water separation and in-situ catalytic degradation performance. As the SiO2@Ag content reached up to 6 wt%, the membrane revealed excellent oil/water separation performance (96% oil removal rate in the oil/water mixture) and simultaneously achieved efficient catalytic degradation performance (95% catalytic degradation rate of methylene blue in water). Moreover, the SiO2@Ag nanoparticles semi-embedded on the as-prepared nanofiber membrane had good bonding with PVC nanofibers, which endowed the tubular PVC/SiO2/SiO2@Ag nanofiber membrane with excellent reuse performance.
Superhydrophobic materials with surface drying, self-cleaning, and antibiological pollution characters are broadly used in biotechnology, medicine, and shipbuilding sectors. In this paper, micro-nano silica is modified using a silane-based coupling agent. An organosilicon compound is grafted to the silica surface to obtain a superhydrophobic material with low surface energy. The results show that the superhydrophobic material with a 20 nm particle size silica modified with vinyltriethoxysilane (VTES-SiO2) offers the best properties with a contact angle of 163.32° and a rolling angle of smaller than 3°. Compared with the raw material, the treated silica reveals superhydrophobicity under nano conditions with a rolling angle smaller than 3°. The wettability of the prepared material does not decrease after being placed in the air for 3 months. Moreover, it still maintains self-cleaning performance after being placed in water for one month, showing the potential of long-term use of the material. The prepared materials provide excellent superhydrophobic properties while is environmentally friendly. Thus, this study delivers potential value for the preparation of environmentally friendly superhydrophobic materials with broad application prospects of superhydrophobicity and self-cleaning characters.
The phase separation features of typical oil-water parallel flow (stratified flow/annular flow) at both hydrophilic and hydrophobic micro-T-junctions are studied experimentally. Complete (100%) separation of oil and water is only observed at the hydrophilic T-junction as the inlet flow is stratified. The maximum separation efficiency of stratified flow at both hydrophilic and hydrophobic T-junctions is higher than that for annular flow. The phase separation efficiency of annular flow is below 50%. Of note, a comparative study illustrates that the phase separation features of stratified flow at macro- and micro-T-junctions are highly similar and are both attributed to the “channeling effect”. At micro-T-junctions, the flow confinement induces the aqueous (water) phase to flow through a stable “water channel,” while the oil phase flows through an “oil channel.” The position of the channel interface depends on the hydrodynamic conditions at the two arms of the T-junctions. A simple model is developed to predict the critical conditions for the complete separation of the two fluids. This study shows that micro-T-junctions with uniform hydrophilic channels are potential candidates for onsite phase separators in micro-fluidic devices.
Oil spills and waste oily water draining have aroused adverse effects on ecosystem, environmental safety and human health. Separation membranes with high efficiency and antifouling ability is highly desired to separate oil/water mixtures. Herein, biomimetic hierarchical BiVO4/Cu(OH)2 nanocone/nanowire dual-structure are anchored on conductive Cu mesh (BV/[email protected]). The BV/[email protected] membrane with open porous structure and roughness surface behaves excellent superhydrophilicity and underwater superoleophobicity, as well as performs good electrocatalytic oxygen evolution and photocatalytic degradation capability to eliminate surface organic pollutants. Therefore, the BV/[email protected] exhibits high water flux (≥45 kL m⁻² h⁻¹), high separation efficiencies (≥99.8%), and good electroflotation cleaning capability (bubbles removal contaminations within 1 min) and photocatalytic degradation ability (kerosene degradation within 70 min). Moreover, due to the protective coating of ultrasmall BiVO4 nanocones, the membrane exhibits excellent stability under harsh environments, including salty, acid/base, calcination, and surface friction. The high oil/water separation capability, good environmental durability and excellent electro-/photo- cleaning capability demonstrate the extensive potential applications of the membranes under various environmental conditions.
Offshore oil spills, industrial oily wastewater, and domestic oil pollution are some of the most serious global challenges, leading environmental causes of morbidity and mortality. Nanofiber membrane materials manufactured via...
Development of an efficient catalyst for ammonia preparation through electrochemical nitrogen fixation is significant and desirable to relieve the tremendous energy-consumption by the conventional Haber-Bosch process. Herein, the abundant oxygen vacancy-containing CuCeO2@NC composite (denoted as Cu-doped CeO2 nanoparticles supported on carbon nitride) was fabricated by annealing melamine-incorporated metal-organic framework (MOF) of CuCe-BTC (BTC = 1,3,5-benzenetricarboxylic acid) under the reducing atmosphere of 10% H2/Ar. The optimized composite of Cu0·1CeO2@NC achieved a high selectivity and an outstanding electrocatalytic activity with NH3 yield rate of 44.5 μg h⁻¹ mgcat.⁻¹ at −0.5 V versus a reversible hydrogen electrode, surpassing most of the reported electrocatalysts and its analogues without copper and nitrogen atoms as dopants. The favorable performance of Cu0·1CeO2@NC would be ascribed to the synergistic effect of the rich oxygen vacancies and the optimal electrical structure induced by heteroatom doping, further confirmed by X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) spectroscopy, and Raman spectra. Moreover, the great electrochemical selectivity and durability for the longtime electrolysis had been demonstrated. This work offered an insight that the electrocatalytic performance would be regulated by heteroatomic dopants and oxygen vacancy toward MOF-derived materials.
The controlled growth of high-purity three-dimensional carbon nanofiber (CNF) networks is achieved on the outer surfaces of ceramic boatsviachemical vapor deposition (CVD) after placing copper nitrate in ceramic boats. During CVD, the copper-nitrate-derived copper nanoparticles in the ceramic boats dramatically improve the yield of these CNF networks on the inherently rough outer surfaces of the ceramic boats, which act as weak catalytic sites for the growth of CNF networks. This approach can be extended to various commonly used ceramic substrates. The free-standing CNF networks, peeled off from the outer surfaces of the ceramic boats, exhibit superior properties, including hydrophobicity, porosity and excellent flexibility, and hence have high absorption capacity for various oils. Furthermore, Janus CNF networks are prepared using selective plasma modification or ammonia annealing of the free-standing CNF networks to produce areas of different wettabilities on their obverse and reverse surfaces. The hydrophobic areas on the obverse and reverse surfaces of the Janus CNF networks exhibit different patterns, which are reversibly switched between invisibility and visibilityviaalternately dropping and removing water. The Janus CNF networks can also act as bifunctional sorbent materials for the simultaneous removal of oils and dyes from water.
We report a facile approach to the fabrication of free-standing three-dimensional carbon nanofiber (CNF) networks, by loading copper nitrates on aluminum (Al) foils, performing chemical vapour deposition (CVD), and finally etching away Al foils via sodium hydroxide. During CVD, copper-nitrate-derived copper nanoparticles catalyze growth of CNF networks on Al foils, and the CNF networks are then liberated after removal of Al foils. The resultant free-standing CNF networks exhibit porous, hydrophobic, lightweight, and highly flexible properties, and the combination of these properties enables CNF networks to absorb various oils with high absorption capacity and excellent recyclability. This work may benefit the rational design of advanced absorbents for applications in cleanup of oil spillage.
Micro- and nanofibers produced by electrospinning and solution blow spinning (SBS) are highly suitable platforms for diverse applications due to their advantageous properties, including the high surface area to volume ratio, high porosity, and flexibility. To render them additional functionalities, distinct pre- or post-modification processes have been proposed for modifying such micro- and nanofibers with 0D, 1D, 2D, and 3D nanostructures. The pre-modification requires the addition of 0D–3D nanostructures (or their precursors) into the polymeric phase before the spinning process, which can demand laborious solubilization and requires changes in experimental spinning parameters, with impact on morphology, spinnability, and properties. Post-modification methods, on the other hand, enable the fabrication of composite fibers without the need to optimize the spinning parameters, allowing a simple and efficient surface modification. Herein, recent advances on post-modification methods of spun fibers, including wet chemistry, grafting, crosslinking, click chemistry, oxidations, hydrolysis and reduction strategies, dip-coating, layer-by-layer, electro/air-spray, atomic layer deposition, and plasma techniques aiming at the surface functionalization with 0D–3D nanostructures are surveyed. Recent results, trends, and challenges on the application of such surface-modified fibers for environmental, industrial, and medical applications, including as adsorbent and filtering membranes, catalysts for pollutants degradation, and wearable sensors are examined.
C 6 -Fluorocarbon (FC)-dendrimer has been applied on cotton knit fabric for developing water repellent, self-cleaning, oil-water separation, acid-resistant, antibacterial, UV resistant and flame retardant property while maintaining acceptable levels of comfort for wearers. The C 6 -Fluorocarbon (FC)-dendrimer coated 100% cotton single jersey knitted fabric samples were prepared using “pad-dry-cure” method, and characterized and tested for comfort and other textile properties. The 90 g/L and 100 g/L FC-dendrimer treated cotton fabrics provided excellent water repellency, oil-water separation and self-cleaning performance. But air permeability and thermal conductivity were 13%, 15%, and 40%, 54% lower, respectively, than those of untreated fabrics. The presence of FC-dendrimer in the treated fabric was confirmed by FTIR, SEM, EDS and XRD analyses. SEM analysis was employed to study the morphology of deposited FC-dendrimer particles on the fabric surface. Thermal behaviors were evaluated by TGA and DTA. The FC-dendrimer-treated fabric also showed promise as a UV ray absorber, antimicrobial activity, acid resistance and flame retardant property. Overall, the result suggests that FC-dendrimer can be a valuable ingredient in the manufacture of multifunctional products.
Transmission of pathogens via respiratory droplets can spread infections such as COVID‐19. Wearing a mask hinders the spread of COVID‐19 infection and has become mandatory in some cases. Although most masks are affordable and disposable, continual daily replacement is required due to their performance deterioration caused by washing and contamination. Hence, a urethane‐reactive coating material comprising perfluoro‐tert‐butanol‐hexamethylene diisocyanate is developed with highly hydrophobic and oleophobic properties to functionalize a polyurethane‐coated fabric to bestow high breathability, durability, reusability, and protection ability. Its functions are maintained after scratch and wash testing, and its air permeability and water vapor transmittance rate (necessary for respiration) are unaffected. Its filtration efficiency of water droplets containing 100 nm polystyrene particles (similar in size to SARS‐CoV‐2) is increased due to its highly hydrophobic properties. In addition, it inhibits the adsorption of bovine serum albumin, the spike protein of COVID‐19, and Staphylococcus aureus and Pseudomonas aeruginosa. A urethane‐reactive coating material comprising perfluoro‐tertbutanol‐hexamethylene diisocyanate is developed with highly hydrophobic and oleophobic properties to functionalize a polyurethane‐coated fabric to bestow high breathability, durability, reusability, and protection ability. Its functions are maintained after scratch and wash testing, and its air permeability and water vapor transmittance rate (necessary for respiration) are unaffected.
Sterilization of ultra-high molecular weight polyethylene (UHMWPE) based composites used for acetabular cup liner via UV or gamma-irradiation before surgery is inevitable. Thus, understanding the alteration of mechanical properties and wear resistance of cup liner via irradiation process requires investigation. This paper aims to understand the effect of UV (0.03 J/cm²) and gamma (25 kGy) irradiation on mechanical properties and scratch resistance of compression molded UHMWPE composites reinforced with alumina (Al2O3), hydroxyapatite (HAp) and carbon nanotubes (CNTs). After irradiation, nearly 100% increased crystallinity of polyethylene due to recrystallization helped in enhancing the hardness and elastic modulus by ∼1.5 times compared to that of as-processed UHMWPE (Hardness: ∼70 MPa and Elastic modulus: ∼1.25 GPa). The recrystallization was not favored by the presence of nano-reinforcements in irradiated UHMWPE based nanocomposites caused deterioration in the mechanical properties. The micro-scratch results revealed the remarkable wear resistance (i.e., 1.5 to 2 times lower wear rate) of irradiated samples than that of as-processed samples. Mouse fibroblast L929 in vitro cell culture test confirmed the cytocompatibility of irradiated samples. This study indicated that the UV and gamma irradiated UHMWPE nanocomposites are the challenging candidates for acetabular cup liner.
The wettability behavior of materials is the subject of numerous scientific investigations due to its significance and relevance to wide range of applications. Here we present comparative analysis of the wettability properties of glass coated by carbon-based nanostructures. Glass surfaces were coated with carbon nanotubes, nanodiamonds, fullerenes, and graphene by drop casting method. These coatings displayed a notable increase in the contact angle (CA) with water drop beads up to the superhydrophobic limit, except for the nanodiamonds coating, which depicted a significant decrease in the CA compared to the clean glass substrate. Moreover, carbon-based soot nanoparticles from candle flame deposited on the glass surface also imparted superhydrophobic characteristics to the glass with CA close to 152°. Carbon nanoparticles were also deposited by femtosecond laser ablation, which is facile, efficient, and contamination-free technique to produce thin homogeneous film containing carbon nanoparticles, which improved the water repellent characteristic while maintaining its transparency in the longer-wavelength part of the visible spectrum. Our studies have shown that carbon nanotubes, fullerenes, graphene and carbon soot depict superhydrophobic characteristics (CA > 150°) and would introduce significant increase in the hydrophobic properties of the surface.
A self-cleaning, transparent superhydrophobic silica-based surface with water contact angle (CA)/sliding angle (SA) 168°/2° was fabricated by simple one-step thermal oxidation of silicone grease. Microstructural studies (FESEM/TEM) confirmed the presence of a sponge-like pore structure of amorphous silica nanoparticle having a diameter of around 20 ± 2.2 nm. EDS analysis confirms the presence of C, Si, and O in coated substrates. Also, phase and thermal studies (XRD, FTIR, and TG-DSC) analysis showed the thermo-oxidative decomposition of silicone grease results in superhydrophobic –H2C-Si-O-Si-CH2- network structure at 400 °C followed by thermally stable superhydrophilic HO-Si-O-Si-OH network structure at 500 °C. The coated surface showed excellent stability towards corrosive liquids (1 M NaCl, NaOH, HCl aqueous solution, and hot water) and exposed temperature up to 400 °C. The maximum visible light transparency of the superhydrophobic glass was 92.4% compared to the uncoated glass (93.3%). Thus, making transparent superhydrophobic surfaces by a simple and straightforward process can be potentially used in self-cleaning glasses for various engineering applications.
Zwitterionic poly(sulfobetaine methacrylate) (PSBMA) was successfully loaded onto a polyacrylonitrile membrane surface by thiol-ene click chemistry. The chemical composition and structure of zwitterionic membrane surfaces were analyzed by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray (EDX) analysis. An increasing amount of sulfobetaine methacrylate (SBMA) led to a higher density of grafted PSBMA chains, which increased from 0 to 776.7 μg/cm2. As a result, the pores of the membranes were blocked, causing a decrease in the permeation flux of the membranes. The fabricated zwitterionic structure induced superhydrophilicity, underwater superoleophobicity, and oil-fouling resistance to the membrane, as confirmed by contact angle measurements of pure water and oily compounds. The zwitterionic membrane was used for the separation of several oil-in-water emulsions, exhibiting outstanding separation efficiency with more than 99.4% oil removal. The antifouling ability of zwitterionic polyacrylonitrile (PAN) membranes was examined by multicycle filtration. It is found that the reversible and irreversible fouling have been suppressed, which is associated with the recycling of the zwitterionic membrane with a high flux recovery ratio. Generally, surface zwitterionicalization via thiol-ene click chemistry proved to be suitable for the preparation of antifouling polyacrylonitrile membranes for emulsion separation.
Coordination polymers [Cd(1,4-bpeb)2(L1)2] (1), [Zn2(1,4-bpeb)2(L2)2(SO42-)2] (2) and [Cd2(1,4-bpeb)(L3)] (H2O)0.7 (3) (H2L1, 3-[2-(3-Hydroxy-phenoxymethyl)-benzyloxy]-benzoic acid;HL2, 1H-Indazole-3-carboxylic acid; H3L3, benzene-1,2,3-tricarboxylic acid; 1,4-bpeb, 1,4-bis[2-(4-pyridyl)vinyl]benzene) have been synthesized under solvothermal conditions. Complexes 1-3 underwent photodimerization in the solid-state to give quantitative yields of single isomeric products. The choice of carboxyl ligands L and metal center determined the arrangement of 1,4-bpeb ligands, which in turn directed the regiochemistry of the final photoproducts. The solid-state network structures of cadmium based 1 and 3 had 1,4-bpeb pairs aligned face-to-face with both C=C centres in each ligand at an appropriate distance and alignment for photodimerization to give the corresponding para-[2.2]cyclophane (pCP) exclusively. By contrast, compound 2 possessed dinuclear (ZnSO4)2 metallocycles that positioned the 1,4-bpeb "arms" face-to-face, but with C=C centres offset at an appropriate distance for only one pair to undergo [2+2] cycloaddition to yield a single stereoisomer of the monocyclobutane photo-product bpbpvpcb. This work highlights crystal engineering design priciples that can be used to facilitate regio- and stereospecificity in solid-state transformations.
We report fabrication of a novel sticky parahydrophobic cerium oxide (CeO2) coating using a facile and industrially viable plasma spray technique, which has prospective applications in microfluidic chips, no loss microdroplet transportation and chemical microreactors. Our coating displays significantly high water contact angle (∼159.02˚) along with high contact angle hysteresis (CAH≥90˚), very much similar to a ‘Rose petal’. This is further strengthened by the fact that the coating displayed remarkable adhesion even with large inverted water droplets of 70 μL, which is significantly higher than the reported values of 18 μL for polymer and 20 μL for drop casted CeO2 nanotubes. We also present systematic characterization results to clarify the ongoing confusion regarding the hydrophobicity of CeO2 coatings often reported in literature. Meanwhile, our parahydrophobic coating also showed remarkable thermal and mechanical stability even at a significantly high temperature of 200 °C for 14 hours and with 50 g abrasive paper.
Three coordination polymers (CPs), [Ni1.5(L)(bipy)2(H2O)3]n(1), [Zn(L)(Hbipy) (H2O)]n⋅2n(H2O) (2) and [Cu(bipy)2(H2O)2]n⋅2n(H2L)⋅ 3nH2O (3) (NaH2L=5‐sulfoisophthalic monosodium salt, bipy=4,4′‐bipyridine) have been synthesized by solvothermal methods. They were characterized by X‐ray single crystal diffraction, elemental and thermogravimetric analyses. Introduction of the auxiliary N‐donor ligand (bipy) can lead to three Ni(II), Zn(II) and Cu(II) CPs with three‐dimensional (3D) 4‐connected network of the point symbol of (7⁵⋅9), one‐dimensional (1D) ladder and two‐dimensional (2D) lattice frameworks, respectively. Compound 1 is racemic, whose topological structure can be divided into left‐handed and right‐handed helices. The fluorescence emission peaks of compounds 1–3 are located at 416 nm, 412 nm and 455 nm, respectively, which may be attributed to the ligand to metal charge transfers. Variable‐temperature magnetic susceptibility measurements can reveal that there are ferromagnetic and antiferromagnetic exchange interactions between the neighboring spins in compounds 1 and 3, respectively, and compound 2 is a diamagnetism system. Compound 1 shows the second‐harmonic generation (SHG) response that is 4 times those of potassium dihydrogen phosphate (KDP).
Here, we report a method to use natural wood lauan as a template to fabricate superhydrophobic biomorphic copper on a carbon substrate (Cu/C). First, a carbon substrate with the microstructure of lauan was obtained by sintering lauan in an oxygen-free environment. A biomorphic Cu/C material was then obtained by immersing this carbon substrate into a Cu(NO3)2 solution and sintering. Finally, the hydrophobicity of the products obtained was investigated. The Cu/C retained the microstructure of the wood well. It exhibited excellent superhydrophobicity after it was modified with fluorine silane. The water contact angle of this modified Cu/C reached 160°.
O processo de beneficiamento de chapas por lapidação de vidro sodo-cálcico na indústria vidreira gera, por si só, um resíduo não aproveitado (rejeito). O rejeito deste material é encaminhado para aterros sanitários, ocasionando impactos ao meio ambiente. O presente trabalho objetivou caracterizar e avaliar o rejeito da lapidação de vidro sodo-cálcico (PV). Após sua aquisição, o PV foi processado por moagem e peneiramento e posteriormente caracterizado através das análises química/mineralógica (FRX, EDS e DRX), morfológica por MEV, de granulometria por difração a laser, análise termogravimétrica (TGA e DSC) e análises termofísicas. Observou-se que as partículas de PV são irregulares e micrométricas com a presença predominante de Na, Si e Ca, elementos característicos de um vidro amorfo sodo-cálcico. A avaliação das características química/mineralógica, morfológica, termofísicas e termogravimétrica do PV permitiu sugerir seu reaproveitamento como cargas de reforço ou de enchimento em materiais compósitos para obtenção de materiais isolantes térmicos.
In recent years extensive work has been focused onto using superhydrophobic surfaces for drag reduction applications. Superhydrophobic surfaces retain a gas layer, called a plastron, when submerged underwater in the Cassie-Baxter state with water in contact with the tops of surface roughness features. In this state the plastron allows slip to occur across the surface which results in a drag reduction. In this work we report flexible and relatively large area superhydrophobic surfaces produced using two different methods: Large roughness features were created by electrodeposition on copper meshes; Small roughness features were created by embedding carbon nanoparticles (soot) into Polydimethylsiloxane (PDMS). Both samples were made into cylinders with a diameter under 12 mm. To characterize the samples, scanning electron microscope (SEM) images and confocal microscope images were taken. The confocal microscope images were taken with each sample submerged in water to show the extent of the plastron. The hydrophobized electrodeposited copper mesh cylinders showed drag reductions of up to 32% when comparing the superhydrophobic state with a wetted out state. The soot covered cylinders achieved a 30% drag reduction when comparing the superhydrophobic state to a plain cylinder. These results were obtained for turbulent flows with Reynolds numbers 10,000 to 32,500.
The excellent properties of wood utilized as an engineering material are detracted by the complex wood-water interactions and the resulting dimensional instability and low durability against biological degradation. Inspired by the lotus effect, mechanically durable superhydrophobic coatings were successfully fabricated on the intrinsically heterogeneous wood substrates by simply dip-coating the suspensions of hydrophobic silica (SiO2) nanoparticles dispersed in polydimethylsiloxane (PDMS) solution. A subsequent low-surface-energy treatment with some expensive reagents is not necessary owing to the hydrophobic nature of PDMS and the modified silica particles. The surface microstructure, roughness and wetting behavior of the PDMS/silica hybrid coatings on wood surfaces were investigated in relation to the loadings of the silica particles in the PDMS matrix. When the silica particle loading reached a critical level, desirable hierarchical micro/nanostructures were formed on the wood substrate, allowing for the generation of superhydrophobicity with a contact angle of 152° and a sliding angle less than 10°. The fabricated PDMS/silica hybrid coating exhibited desirable durability against mechanical abrasion and high-frequency ultrasonic washing in water whilst basically retaining its microstructure and superhydrophobicity. Such mechanically durable superhydrophobic wood surfaces with self-cleaning properties offer an interesting alternative for wood modification, and could improve the performance of wood as an engineering material.
Superhydrophobic nanocoatings, a combination of nanotechnology and superhydrophobic surface, have received extraordinary attention recently, focusing both on novel preparation strategies and on investigations of their unique properties. In the past dedcades, inspired by lotus leaf, the discovery of nano- and micro- hierarchical structure has brought about great change in superhydrophobic nanocoatings field. In this paper we review the contributions to this field reported in recent literatures, mainly including materials, fabrication and applications. In order to facilitate comparison, materials are divided into 3 categories as follow: the inorganic materials, the organic materials, and the inorganic-organic materials. But each kind of materials has itself merits and demerits, as well as fabrication techniques. The process of each technique is illustrated simply through a few classical examples. There is, to some extent, an association between various fabrication techniques, but a more one is different. So, it is important to choose proper preparation strategies, according to condition and purposes. The peculiar properties of superhydrophobic nanocoatings, such as self-cleaning, anti-bacteria, anti-icing, corrosion resistance and so on, are the most dramatic. Not only do we introduce the application instances, but also try to superficial expound the principle behind the phenomenon. Finally, some challenges and the potential promising breakthroughs are also succinctly highlighted in this field.
By simply heating commercial copper foil under an oxygen atmosphere and subsequently annealing CuO under a hydrogen atmosphere, the 3D Cu structures in the form of double hierarchical bumps are generated. The contact angle of a lotus leaf-inspired graphene grown on the reconstructed 3D Cu structures is 154.2°.
We study fluid flow in the vicinity of textured and superhydrophobically coated surfaces with characteristic texture sizes on the order of 10 mum. Both for droplets moving down an inclined surface and for an external flow near the surface (hydrofoil), there is evidence of appreciable drag reduction in the presence of surface texture combined with superhydrophobic coating. On textured inclined surfaces, the drops roll faster than on a coated untextured surface at the same angle. The highest drop velocities are achieved on surfaces with irregular textures with characteristic feature size ~8 mum. Application of the same texture and coating to the surface of a hydrofoil in a water tunnel results in drag reduction on the order of 10% or higher. This behavior is explained by the reduction of the contact area between the surface and the fluid, which can be interpreted in terms of changing the macroscopic boundary condition to allow nonzero slip velocity.
A superhydrophobic surface is a surface with a water contact angle close to or higher than 150°. In this feature article, we review the historical and present research on superhydrophobic surfaces, including the characterization of superhydrophobicity, different ways to fabricate rough surfaces, and low-surface-energy modifications on inorganic and organic rough surfaces. It is the combination of surface roughness and low-surface-energy modification that leads to superhydrophobicity. Notably, research on superhydrophobic surfaces has not only fundamental interest but various possible functional applications in micro- and nano-materials and devices.
A new class of robust carbon nanotube (CNT) membranes is developed using a scalable chemical vapor deposition method by direct growth of the CNT on a nickel alloy (Hastelloy) mesh with micrometer-sized openings. The developed membranes have a dense, entangled network of CNT with 50–500 nm pore openings and are superhydrophobic. These CNT membranes are resistant to air oxidation up to ∼500 °C and chemical corrosion in concentrated HCl or NaCl solutions. Adhesion and utrasonication tests suggest that the developed CNT membranes are resistant to delamination and demonstrate a high interfacial bonding of the grown CNT with the alloy substrate. Potential application of the developed CNT-Hastelloy membranes for separation is explored by conducting membrane distillation tests using a 10,000 mg/L NaCl solution. The developed membranes show similar salt rejection performance compared with a carbon bucky paper membrane. These robust carbon nanotube membranes are reusable and expected to be less susceptible to fouling because of their superhydrophobic properties. Furthermore, if fouled, they can be regenerated by heating in air or using an acid wash.
Lotus-inspired superhydrophobic coatings are usually mechanically weak and lack durability, this hinders their practical applications. A suspension that can be treated on various materials in any size and shape to form a mechanically durable superhydrophobic coating is developed, which retains water repellent properties after multiple cycles of abrasion, blade scratching, tape-peeling, repeated deformation, a series of environmental tests and recycling. Based on its superhydrophobicity under oil, two highly efficient systems were developed for oil purification-stirring and inverted cone systems. Small water drops converge on the coated surface that was immersed in oil through velocity-controlled stirring, or designing an inverted cone superhydrophobic surface under oil to collect water drops spontaneously. This coating can be readily used for practical applications to make a durable superhydrophobic coating that functions either in air or oils.
Flame-retardant and self-healing superhydrophobic coatings are fabricated on cotton fabrics by a convenient solution dipping method, which involves the sequential deposition of a trilayer of branched poly(ethylenimine) (bPEI), ammonium polyphosphate (APP) and fluorinated-decyl polyhedral oligomeric silsequioxane (F-POSS). When directly exposed to flame, such a trilayer coating generates a porous char layer because of its intumescent effect, successfully endowing the coated fabric with self-extinguishing property. Meanwhile, the preserved F-POSS in cotton fabrics and APP/bPEI coating produce a superhydrohobic surface with self-healing function. The coating can repetitively and autonomically restore superhydrophobicity once the superhydrophobicity is damaged. The resultant cotton fabrics, which are flame resistant, waterproof and self-cleaning, can be readily cleaned with simple water rinsing. Thus, the integration of self-healing superhydrophobicity with flame-retardancy provides a practical way to solve the problem regarding the washing durability of the flame-retardant coatings. The flame-retardant and superhydrophobic fabrics can endure more than 1000 cycles of abrasion under a pressure of 44.8 kPa without losing its flame-retardancy and self-healing superhydrophobicity, showing potential applications as multifunctional advanced textiles.
A simple, one-step method is developed to construct a superhydrophobic surface by electrodepositing Mg-Mn-Ce magnesium plate in an ethanol solution containing cerium nitrate hexahydrate (Ce(NO3)3•6H2O) and myristic acid. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FT-IR) spectroscopy were employed to characterize the surfaces. The shortest electrodepositing time to obtain a superhydrophobic surface is about 1 min, and the as-prepared superhydrophobic surfaces have a maximum contact angle (CA) of 159.8° and sliding angle (SA) less than 2°. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements demonstrated that the superhydrophobic surface greatly improved corrosion properties of magnesium alloy in 3.5 wt.% aqueous solutions of NaCl, Na2SO4, NaClO3, and NaNO3. Besides, the chemical and mechanical durability of the as-prepared superhydrophobic surface were also examined. The presented method is rapid obtained, low-cost and environment-friendly, which is of significant value for industrial fabrication of anticorrosion superhydrophobic surfaces and is supposed to have a promising future in expanding the application of magnesium alloy.
Reactive superhydrophobic surfaces are highly promising for biotechnological, analytical, sensor or diagnostic applications but are difficult to realize due to the chemical inertness of most superhydrophobic surfaces. In this communication, we report on a photoactive, inscribable, non-wettable and transparent surface (PAINTS), prepared by polycondensation of trichlorovinylsilane to form thin transparent reactive porous nanofilament on a solid substrate. The PAINTS shows excellent superhydrophobicity and can be conveniently functionalized with the photo click thiol-ene reaction. In addition, we show for the first time that the PAINTS bearing vinyl groups can be easily modified with disulfides under UV irradiation. The effect of superhydrophobicity of PAINTS on the formation of high-resolution surface patterns has been investigated. The developed reactive superhydrophobic coating can find applications for surface bio-functionalization using abundant disulfide bearing biomolecules, such as peptides, proteins, or antibodies.
Unique and inherent nano-roughened morphologies of vertically aligned carbon nanotube (VACNT) forests are desirable for mimicking biological superhydrophobic surface systems. In this paper, we report on a new class of robust dual-roughened superhydrophobic surfaces based on VACNT forests coated conformally with thin silicone. The vapor phase deposition of silicone considerably reduces the surface energy of the VACNTs by conformally and completely covering the vertical structures. This significantly enhances the superhydrophobic robustness of the VACNTs by preventing the surfaces from being wet, even under pressurized conditions. In addition, micro-patterning based on a simple contact transfer technique enables easy fabrication of VACNT micro-pillar arrays with various pillar-to-pillar spacings ranging from 45 to 160 μm with respect to a fixed width of ∼65 μm. A combination of simple contact transfer and subsequent silicone coating techniques facilitates the achievement of micro/nano hierarchical VACNT superhydrophobic surfaces with superior wetting properties (high water contact angle of 168 ± 0.3°, low contact angle hysteresis of 2.64 ± 0.4°, and low sliding angle of <∼5°) and water-repellent performance (even at impact velocity of up to ∼1.4 m/s) while ensuring superhydrophobic robustness.
Superhydrophobic surfaces are of immense scientific and technological interests for a broad range of applications. However, a major challenge remains in developing scalable methodologies that enable superhydrophobic coatings on versatile substrates with a combination of strong mechanical stability, optical transparency, and even stretchability. Herein, we developed a scalable methodology to versatile hydrophobic surfaces that combine with strong mechanical stability, optical transparency, and stretchability by using a self-assembled hydrogel as the template to in situ generate silica microstructures and subsequent silanization. The superhydrophobic coatings can be enabled on virtually any substrates via large-area deposition techniques like dip coating. Transparent surfaces with optical transmittance as high as 98% were obtained. Moreover, the coatings exhibit superior mechanical flexibility and robustness that it can sustain contact angles ∼160° even after 5000 cycles of mechanically stretching at 100% strain. The multifunctional surfaces can be used as screen filters and sponges for the oil/water separation that can selectively absorb oils up to 40× their weight.
The physicochemical and droplet impact dynamics of superhydrophobic carbon nanotube arrays are investigated. These superhydrophobic arrays are fabricated simply by exposing the as-grown carbon nanotube arrays to a vacuum annealing treatment at a moderate temperature. This treatment, which allows a significant removal of oxygen adsorbates, leads to a dramatic change in wettability of the arrays, from mildly hydrophobic to superhydrophobic. Such change in wettability is also accompanied by a substantial change in surface charge and electrochemical properties. Here, the droplet impact dynamics are characterized in terms of critical Weber number, coefficient of restitution, spreading factor, and contact time. Based on these characteristics, it is found that superhydrophobic carbon nanotube arrays are among the best water-repellent surfaces ever reported. The results presented herein may pave a way for the utilization of superhydrophobic carbon nanotube arrays in numerous industrial and practical applications, including inkjet printing, direct injection engines, steam turbines, and microelectronic fabrication.
Onion-like carbon micro-spheres composed of many nanoflakes have been prepared by pyrolyzing waste polyethylene terephthalate in supercritical carbon dioxide at 650 °C for 3h followed by subsequent vacuum annealing at 1500 °C for 0.5 h. The obtained onion-like carbon micro-spheres have very high surface roughness, and exhibit unique hydrophobic properties. Considering their structural similarities with lotus leaf, we further developed a low-cost, acid/alkaline-resistant and fluorine-free super-hydrophobic coating strategy on fabrics by employing the onion-like carbon micro-spheres and polydimethylsiloxane as raw materials. This provides a novel technique to convert waste polyethylene terephthalate to valuable carbon materials. At the same time, we demonstrate a novel application direction of carbon materials by taking advantage of their unique structural properties. The combination of recycling waste solid materials as carbon feedstock for valuable carbon material production, with the generation of highly value-added products such as super-hydrophobic fabrics, may provide a feasible solution for sustainable solid waste treatment.
We have explored the condensation behavior of water on a superhydrophobic carbon fiber (CF) network with high-aspect-ratio hair-like nanostructures. Nanostructures ranging from nanopillars to hairy shapes were grown on CFs by preferential oxygen plasma etching. Superhydrophobic CF surfaces were achieved by application of a hydrophobic siloxane-based hydrocarbon coating, which increased the water contact angle from 147° to 163° and decreased the contact angle hysteresis from 71° to below 5°, sufficient to cause droplet roll-off from the surface. Water droplet nucleation and growth on the superhydrophobic CF were significantly retarded due to the high-aspect-ratio nanostructures under super-saturated vapor conditions. CFs are observed to wet with condensation between fibers of the pristine surface under super-saturated vapor conditions, which eventually leads to flooding. However, dropwise condensation became dominant in the superhydrophobic CF network, allowing for easy removal of the condensed droplets, which largely allowed the interstitial spaces of the fiber network to remain dry. It is implied that superhydrophobic CF can provide a passage for vapor or gas flow in wet environments such as a gas diffusion layer requiring the effective water removal in the operation of proton exchange membrane fuel cell.
A novel filtration system has been developed for the separation of water and hydrophobic solvents. Copper meshes of various pore diameter (297, 251, 178 and 152 μm) were coated with extremely rough silicone elastomer films. Depositions of this polymer were carried out by aerosol assisted chemical vapour deposition. The polymer coating rendered all meshes superhydrophobic, with static water contact angles of 152–167° depending on mesh diameter. The meshes were found to be exceptionally efficient in separating organic solvents (hexane, petroleum ether and toluene) from water. The dual-layered filtration system developed focuses on directing the transport of oil away from water with the highest efficiency. The device provides a scalable solution to many challenges, including microanalysis, filtration and chemical processing.
This review describes state-of-the-art scientific and technological developments of electrospun nanofibers and their use in self-cleaning membranes, responsive smart materials, and other related applications. Superhydrophobic self-cleaning, also called the lotus effect, utilizes the right combinations of surface chemistry and topology to form a very high contact angle on a surface and drive water droplets away from it. The high-contact-angle water droplets easily roll off the surface, carrying with them dirt, particles, and other contaminants by way of gravity. A brief introduction to the theory of superhydrophobic self-cleaning and the basic principles of the electrospinning process is presented. Also discussed is electrospinning for the purpose of creating superhydrophobic self-cleaning surfaces under a wide variety of parameters that allow effective control of roughness of the porous structure with hydrophobic entities. The main principle of electrospinning at the nanoscale and existing difficulties in synthesis of one-dimensional materials by electrospinning are also covered thoroughly. The results of different electrospun nanofibers are compared to each other in terms of their superhydrophobic properties and their scientific and technological applications.
Surface free energy of biocompatible polymers is important factor which affects the surface properties such as wetting, adhesion and biocompatibility. In the present work, the change in the surface free energy of ultra-high molecular weight polyethylene (UHMWPE) samples, which is produced by electron beam and gamma ray irradiation were, investigated. Mechanism of the changes in surface free energy induced by irradiations of doses ranging from 25 to 500 kGy was studied. FTIR technique was applied for sample analysis. Contact angle measurements showed that wettability and surface free energy of samples have increased with increasing the irradiation dose, where the values of droplet contact angle of the samples decrease gradually with increasing the radiation dose. The increase in the wettability and surface free energy of the irradiated samples are attributed to formation of hydrophilic groups on the polymer surface by the oxidation, which apparently occurs by exposure of irradiated samples to the air.
The relationships among the nominal thickness of Co catalyst, the structure of the catalyst particles, and the structure of carbon nanotubes (CNTs) growing from the catalyst during chemical vapor deposition were investigated. Various morphologies of CNTs such as individuals, random networks parallel to the surface of the substrate (‘grasses’), and vertically aligned forests of single- and multi-walled carbon nanotubes were grown by only varying the nominal thickness of catalyst under the same reaction condition. These different morphologies at the same growth time were due to the different areal density rather than to the length of CNTs. With increasing nominal thickness of catalyst, the catalyst particles changed in diameter while their areal density remained relatively almost constant. The change in diameter possibly affected the number ratio of active catalyst particles to the whole particles, which in turn affected the areal density of CNTs and yielded the various morphologies. Longer growth time increased the CNT length, which caused further change in CNT morphologies from individuals to grasses and grasses to forests.
Nature has developed materials, objects, and processes that function from the macroscale to the nanoscale. The emerging field of biomimetics allows one to mimic biology or nature to develop nanomaterials, nanodevices, and processes which provide desirable properties. Hierarchical structures with dimensions of features ranging from the macroscale to the nanoscale are extremely common in nature to provide properties of interest. There are a large number of objects including bacteria, plants, land and aquatic animals, and seashells with properties of commercial interest. Certain plant leaves, such as Lotus leaves, are known to be superhydrophobic and self-cleaning due to the hierarchical roughness of their leaf surfaces. The self-cleaning phenomenon is widely known as the “Lotus effect.” These surfaces with high contact angle and low contact angle hysteresis with a self-cleaning effect also exhibit low adhesion and drag reduction for fluid flow. In this article, the theoretical mechanisms of the wetting of rough surfaces are presented followed by the characterization of natural leaf surfaces. The next logical step is to realize superhydrophobic surfaces based on understanding of the leaves. Next, a comprehensive review is presented on artificial superhydrophobic surfaces fabricated using various fabrication techniques and the influence of micro-, nano- and hierarchical structures on superhydrophobicity, self-cleaning, low adhesion, and drag reduction.
This letter reports low-pressure, room-temperature growth of carbon nanofibers containing nitrogen by plasma chemical vapor deposition arrangement. By alternating pure acetylene plasma and afterglow pure nitrogen high dense plasma, a fine control of the fibers growth kinetic is obtained. This layer-by-layer deposition technique takes advantage of nitrogen chemical etching effects during the growth of nitrogen-doped carbon nanofibers.
The present study demonstrates the creation of a stable, superhydrophobic surface using the nanoscale roughness inherent in a vertically aligned carbon nanotube forest together with a thin, conformal hydrophobic poly(tetrafluoroethylene) (PTFE) coating on the surface of the nanotubes. Superhydrophobicity is achieved down to the microscopic level where essentially spherical, micrometer-sized water droplets can be suspended on top of the nanotube forest.
Copper-mesoporous molecular sieves type MCM-41 have been successfully prepared by different direct incorporation methods of the metal in the initial synthesis gel. Various techniques including XRD, AAS, adsorption/desorption of N2, UV−vis−DR, TPR, and XPS were employed for the materials characterization. All of the materials exhibited a good structural regularity, even for loadings of copper of 10 wt %, besides high specific surface areas and pore volumes. An extended and detailed study about the nature of copper oxidation state as well as of the copper species distribution on the siliceous nanostructure has been made. It was found that copper is present on the mesoporous silica in the form of various species: isolated mononuclear Cuδ+ cations possibly in coordination with the lattice oxygen; linear oligonuclear [Cuδ+···Oδ−···Cuδ+]n clusters probably inserted into mesoporous channels; and bulky CuO oxide segregated of the structure. The distribution of copper species in the final solid depends on the preparation method used as well as of the copper content in the initial gel. Moreover, we infer the coexistence of the both copper oxidation states +1 and +2 (+δ) in the major species of these materials: isolated and oligonuclear copper species.
We have selectively synthesized ultralow density (0.015 ± 0.002 g/cm3) double-walled carbon nanotube (DWNT) arrays. The low mass density is due to the large diameter and low-site density of DWNTs in the arrays. The diameter of the as-grown DWNTs varies from 4.5 to 14.8 nm with a mean value of 7.9 nm. The role of the thickness of Fe catalyst layer is evaluated for the selective growth of large-diameter DWNTs. Our DWNT arrays have promising applications in areas such as solar absorbers and super-hydrophobic surfaces.
The feasibility of reinforcing conventional carbon fiber composites by grafting carbon nanotubes (CNTs) onto the fiber surface has been investigated. Carbon nanotubes were grown on carbon fibers using the chemical vapor deposition (CVD) method. Iron was selected as the catalyst and predeposited using the incipient wetness technique before the growth reaction. The morphology of the products was characterized using scanning electron microscopy (SEM), which showed evidence of a uniform coating of CNTs on the fiber surface. Contact angle measurements on individual fibers, before and after the CNT growth, demonstrated a change in wettability that can be linked to a change of the polarity of the modified surface. Model composites based on CNT-grafted carbon fibers/epoxy were fabricated in order to examine apparent interfacial shear strength (IFSS). A dramatic improvement in IFSS over carbon fiber/epoxy composites was observed in the single fiber pull-out tests, but no significant change was shown in the push-out tests. The different IFSS results were provisionally attributed to a change of failure mechanism between the two types of tests, supported by fractographic analysis.
Control of wettability is of significance in industry as well as our daily live. Amorphous carbon (a-C) films with nanostructured surface were deposited on silicon and glass substrates at different substrate temperatures through a magnetron sputtering technique. The microstructures of the a-C films were studied by SEM and XPS, which indicate that the surface of the a-C films deposited at room temperature are smooth due to their much dense sp3-bonded carbon, while they turn to be more porous graphite-like structure with elevated deposition temperature. The water contact angle (CA) measurements show that these pure carbon films exhibit different wettability, ranging from hydrophilicity with CA less than 40° to super-hydrophobicity with CA of 152°, which reveal that the surface wettability of a-C films can be controlled well by using nanostructures with various geometrical and carbon state features. The graphite-like carbon film deposited at 400 °C without any modification exhibits super-hydrophobic properties, due to the combining microstructures of spheres with nanostructures of protuberances and interstitials. It may have great significance on the study of wettability and relevant applications.
Cobalt hierarchical structure having intrinsic superhydrophobic property is prepared via an electrochemical growth approach. The structure exhibits aesthetic flower-like morphology. A quenching strategy is employed to elucidate the plausible crystal growth mechanism. Without further hydrophobic organic molecule modification, the hierarchical structure occupying surface exhibits superhydrophobic effect, which is a new superhydrophobicity example achieved from the hydrophilic material. An approach based on computer graphics is utilized to simulate the contact pattern on this non-Euclidean hierarchical structure.Graphical abstractResearch highlights▶ Flower-like cobalt crystal is prepared by electrochemical method without surfactant and template. ▶ Crystal growth mechanism is elucidated in detail. ▶ Without any surface modification to the surface, the structure exhibits intrinsic superhydrophobicity property. ▶ The superhydrophobicity is simulated with computer graphics technique.
The separation of gas molecules and water vapor has become increasingly important for electronic, energy, and environmental systems. Here we demonstrate a new mechanism of enhanced condensation, agglomeration, and rejection of water vapor by superhydrophobic aligned multiwalled carbon nanotubes with the intertube distance of 73 nm, channel aspect ratio of ~5.5 × 10(4), and tortuosity of 1.157. The array with the characteristic channel dimension some 300 times greater than the target molecule size effectively suppressed water molecular transport at room temperature with the selectivity as high as ~2 × 10(5) (H(2)/H(2)O). The flow through the interstitial space of nanotubes allowed high permeability of other gas molecules (2.1 × 10(-9) to 3.8 × 10(-8) mol · m/m(2) · s · Pa), while retaining high selectivity, which is orders of magnitude greater than the permeate flux of polymeric membranes used for the water-gas mixture separation. This new separation mechanism with high selectivity and permeate flux, enabled by the unique geometry of aligned nanotubes, can provide a low-energy and cost-effective method to control humidity.
Research into extreme water-repellent surfaces began many decades ago, although it was only relatively recently that the term superhydrophobicity appeared in literature. Here we review the work on the preparation of superhydrophobic surfaces, with focus on the different techniques used and how they have developed over the years, with particular focus on the last two years. We discuss the origins of water-repellent surfaces, examining how size and shape of surface features are used to control surface characteristics, in particular how techniques have progressed to form multi-scaled roughness to mimic the lotus leaf effect. There are notable differences in the terminology used to describe the varying properties of water-repellent surfaces, so we suggest some key definitions
The wettability of CVD diamond films with liquids of different physico-chemical natures (water, glycerin, tin melt) was investigated by measuring the contact angles using the sessile drop method. The translucent diamond films of 0.5-mm thickness were grown in a microwave plasma CVD using CH4–H2 mixtures as the source gas, and separated from Si substrates. The growth surfaces have been polished to a roughness of Ra≤10 nm, and then exposed to microwave hydrogen plasma or thermal oxidation in air at 500 °C. Raman and Auger/XPS spectroscopies, optical and atomic force microscopies have been used to characterize the diamond films. Based on the wettability data, the variations in surface energy induced by hydrogenation and oxidation of polycrystalline diamond have been evaluated by the Fowkes equation. The hydrogenation of the films in the plasma essentially increases hydrophobic properties (contact angle for water increases up to θ=93°) as compared to oxidation (θ=32°). This is attributable to a reduction in a polar component of the surface energy due to hydrogen adsorption-induced reconstruction of the film surface. For comparison, the wettability of HPHT diamond single crystal, diamond ceramics and pyrolytic graphite have been measured and the differences observed will be discussed in this paper.
Carbon nanofibres are grown on a carbon fibre cloth using plasma enhanced chemical vapour deposition from a gas mixture of acetylene and ammonia. A cobalt colloid is used as a catalyst to achieve a good coverage of nanofibres on the surface of the carbon fibres in the cloth. The low temperature growth conditions that we used would allow growth on temperature sensitive polymers and fibres. The nanofibres grown by a tip growth mechanism have a bamboo-like structure. A significant increase of the bulk electrical conductivity of the carbon cloth was observed after the nanofibre growth indicating a good electrical contact between carbon nanofibres and carbon fibres. The as-grown composite material could be used as high surface area electrodes for electrochemical applications like fuel cells and super-capacitors.
Superhydrophobic/superhydrophilic micropatterning on a carbon nanotube (CNT) film has been achieved using a laser plasma-type hyperthermal atom beam facility, which produces a small amount of damage and generates a highly anisotropic beam. Fluorination and oxidation on CNT films by exposure to fluorine-atom and oxygen-atom beams caused superhydrophobic and superhydrophilic surfaces, respectively, while maintaining the as-grown fibrous forms of the CNT films. Micropatterned oxidation on CNT films without using photoresists created superhydrophilic microdots and microchannels.
Superhydrophobic carbon fabric with micro/nanoscaled two-tier roughness was fabricated by decorating carbon nanotubes (CNTs) onto microsized carbon fibers, using a catalytic chemical vapor deposition and subsequent fluorination surface treatment. The superhydrophobic surfaces are based on the regularly ordered carbon fibers (8–10 μm in diameter) that are decorated by CNTs with an average size of 20–40 nm. The contact angle of water significantly increases from 148.2 ± 2.1° to 169.7 ± 2.2° through the introduction of CNTs. This confirms that the wettability of carbon fabric changes from hydrophobicity to superhydrophobicity due to structural transformation. This finding sheds light on how the two-tier roughness surface induces superhydrophobicity of rough surfaces, and how the presence of CNTs reduces the area fraction of a water droplet in contact with the carbon surface with two-tier roughness.
The analysis of the surface chemistry of carbon materials is of prime importance in numerous applications, but it is still a challenge to identify and quantify the surface functional groups which are present on a given carbon. Temperature programmed desorption with mass spectrometry analysis (TPD-MS) and X-ray photoelectron spectroscopy with an in situ heating device (TPD-XPS) were combined in order to improve the characterization of carbon surface chemistry. TPD-MS analysis allowed the quantitative analysis of the released gases as a function of temperature, while the use of a TPD device inside the XPS setup enabled the determination of the functional groups that remain on the surface at the same temperatures. TPD-MS results were then used to add constraints on the deconvolution of the O1s envelope of the XPS spectra. Furthermore, a better knowledge of the evolution of oxygen functional groups with temperature during a thermal treatment could be obtained. Hence, we show here that the combination of these two methods allows to increase the reliability of the analysis of the surface chemistry of carbon materials.
Coating is an essential step in adjusting the surface properties of materials. Superhydrophobic coatings with contact angles
greater than 150° and roll-off angles below 10° for water have been developed, based on low-energy surfaces and roughness
on the nano- and micrometer scales. However, these surfaces are still wetted by organic liquids such as surfactant-based solutions,
alcohols, or alkanes. Coatings that are simultaneously superhydrophobic and superoleophobic are rare. We designed an easily
fabricated, transparent, and oil-rebounding superamphiphobic coating. A porous deposit of candle soot was coated with a 25-nanometer-thick
silica shell. The black coating became transparent after calcination at 600°C. After silanization, the coating was superamphiphobic
and remained so even after its top layer was damaged by sand impingement.
The control of surface morphology and wettability is crucial in the development of superhydrophobic surfaces, which implies new strategy and molecular design. In this Article, we report the synthesis, characterization, and electrochemical properties of original 3,4-ethyleneoxythiathiophenes (EOTT) as platform molecules and its derivatives bearing a semifluorinated chain of various length (F-octyl, F-hexyl, F-butyl, and F-ethyl). We report the influence of the fluorinated chain length as well as the presence of sulfur atoms in the monomer on the surface construction and nonwetting properties of the corresponding electrodeposited polymer films. Surprisingly, these films exhibit the possibility to obtain extremely long polymer fibers with a possible control of their length by a careful choice in the monomer structure. We show that the presence of sulfur atoms in the monomer structure seems to be necessary to modulate the formation of extremely long polymer fibers by aggregation of smaller polymer fibrils. In this Article, the formation of superhydrophobic material (contact angle above 150°) for four, six, and eight fluoromethylene units but also highly hydrophobic surfaces (contact angle above 125°) from extremely short chains (two fluoromethylene units) is also demonstrated.
We report a simple and rapid method to prepare multifunctional free-standing single-walled carbon nanotube (SWCNT) films with variable thicknesses ranging from a submonolayer to a few micrometers having outstanding properties for a broad range of exceptionally performing devices. We have fabricated state-of-the-art key components from the same single component multifunctional SWCNT material for several high-impact application areas: high efficiency nanoparticle filters with a figure of merit of 147 Pa(-1), transparent and conductive electrodes with a sheet resistance of 84 Ω/◻ and a transmittance of 90%, electrochemical sensors with extremely low detection limits below 100 nM, and polymer-free saturable absorbers for ultrafast femtosecond lasers. Furthermore, the films are demonstrated as the main components in gas flowmeters, gas heaters, and transparent thermoacoustic loudspeakers.
Nature is the creation of aesthetic functional systems, in which many natural materials have vagarious structures. Inspired from nature, such as lotus leaf, butterfly' wings, showing excellent superhydrophobicity, scientists have recently fabricated a lot of biomimetic superhydrophobic surfaces by virtue of various smart and easy routes. Whilst, many examples, such as lotus effect, clearly tell us that biomimicry is dissimilar to a simple copying or duplicating of biological structures. In this feature article, we review the recent studies in both natural superhydrophobic surfaces and biomimetic superhydrophobic surfaces, and highlight some of the recent advances in the last four years, including the various smart routes to construct rough surfaces, and a lot of chemical modifications which lead to superhydrophobicity. We also review their functions and applications to date. Finally, the promising routes from biomimetic superhydrophobic surfaces in the next are proposed.
A new method for transforming common polymers into superhydrophobic conductive surfaces, with both a high static water contact angle (approximately 160 degrees) and a low sliding angle (2.0 degrees-4.5 degrees), and a low sheet resistance on the order of 10(1)-10(3) ohms/sq is presented. A layer of multiwalled carbon nanotubes (MWNTs) is first distributed on the surface of a polymer substrate, then by a single step of pressing, the MWNTs are partially embedded inside the substrate surface and form a superhydrophobic coating with a "carpet-" or "hair"-like morphology. The infiltration of polymer melts into the porous MWNT layer follows Darcy's law, and the pressing time greatly influence the morphology and superhydrophobicity. Moreover, the coating can be electrically heated by 20-70 degrees C with a voltage as low as 4-8 V at an electric energy density below 1.6 J/cm(2) and therefore can be used for deicing applications. Hydroxylation and fluoroalkylsilane treatment can greatly improve the stability of the superhydrophobicity of MWNTs. This method is convenient and applicable to a variety of thermoplastic polymers and nonpolymer substrates coated by silicone rubber.
Direct growth of single-walled carbon nanotubes (SWNTs) on flat substrates by chemical vapor deposition (CVD) is very important for the application of SWNTs in nanodevices. In the growth process, catalysts play an important role in controlling the structure of SWNTs. Over the years, we have systematically studied the size-controlled synthesis of Fe-based nanoparticles and the CVD growth of SWNTs, especially the horizontally aligned SWNTs, catalyzed by these produced nanoparticles. Some new catalysts were also developed. Among them, Cu is shown to be a superior catalyst for growing SWNT arrays on both silicon and quartz substrates and Pb is a unique catalyst from which one can obtain SWNTs without any metallic contaminant. SWNTs prepared with both Cu and Pb are very suitable for building high-performance nanodevices. These studies are also very helpful for further understanding the growth mechanism of SWNTs.
The interest in highly water-repellent surfaces has grown in recent years due to the desire for self-cleaning surfaces. A super-hydrophobic surface is one that achieves a water contact angle of 150 degrees or greater. This article explores the different approaches used to construct super-hydrophobic surfaces and identifies the key properties of each surface that contribute to its hydrophobicity. The models used to describe surface interaction with water are considered, with attention directed to the methods of contact angle analysis. A summary describing the different routes to hydrophobicity is also given.
High-surface-area silicon oxycarbide macroporous fibers were fabricated through in situ cross-linking of a preceramic precursor without a prepatterned template. The unique luffa-like shell combined with intrinsic silicon-containing groups accounts for the resultant superhydrophobic property. Meanwhile, the oil-uptake capacity of the corresponding fiber mat is significantly improved by the capsulated nanoparticles.
The multi-scale microstructure of a lotus leaf is rendered non-wetting by micro-protrusions
and nano-hairs present on its surface. The mechanical properties of the surface become
important since the water droplet has to be supported on the micro-protrusions without
wetting the surface. Current work correlates the non-wetting behavior of the lotus leaf with
its mechanical properties (Young's modulus and critical flexing stress) and areal spread of
micro-protrusions on the leaf surface. Quasistatic nanoindentation of nano-hairs
on the lotus leaf surface has shown a variation of elastic modulus between 359
and 870 MPa, which in turn dictates the critical flexing strength and consequent
non-wetting. Computational fluid dynamics modeling is utilized to correlate wetting
phenomena with the areal spread of micro-protrusions. A qualitative model is
proposed for the way nature has chosen to render the lotus leaf surface non-wetting.