Advanced
Superhydrophobic carbon-based materials: a review of synthesis, structure, and applications
Superhydrophobic carbon-based materials: a review of synthesis, structure, and applications
Carbon letters. 2014. Apr, 15(2): 89-104
Copyright © 2014, Korean Carbon Society
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
  • Received : February 02, 2014
  • Accepted : March 03, 2014
  • Published : April 30, 2014
Download
PDF
e-PUB
PubReader
PPT
Export by style
Share
Article
Author
Metrics
Cited by
TagCloud
About the Authors
Long-Yue Meng
Department of Chemical Engineering, Yanbian University, Yanji 133002, China
Soo-Jin Park
Department of Chemistry, Inha University, Incheon 402-751, Korea
sjpark@inha.ac.kr
Abstract
Materials with appropriate surface roughness and low surface energy can form superhydrophobic surfaces, displaying water contact angles greater than 150°. Superhydrophobic carbon-based materials are particularly interesting due to their exceptional physicochemical properties. This review discusses the various techniques used to produce superhydrophobic carbon-based materials such as carbon fibers, carbon nanotubes, graphene, amorphous carbons, etc. Recent advances in emerging fields such as energy, environmental remediation, and thermal management in relation to these materials are also discussed.
Keywords
1. Introduction
Wettability of a solid surface describes the ability of a liquid to maintain contact with the surface, which is important in the bonding or adherence of two materials [1] . Dependent on both roughness and chemical heterogeneitym, wettability is a very important characteristic in nature as well as in our daily life. Hydrophobicity and hydrophilicity are two principal wettablility conditions. The surfaces of materials are hydrophilic if the water contact angle (WCA, θ) is in the range of 0° ≤ θ < 90° and they are hydrophobic if the WCA is 90° < θ ≤ 180°. Hydrophobicity is observed in nonpolar substances, which tend to aggregate in aqueous solutions and exclude water molecules.
Superhydrophobic materials have recently attracted attention from both academic and industrial circles because of their importance in fundamental research and potential industrial applications such as bio-surfaces, anti-biofouling, transparent and antireflective superhydrophobic coatings, structural color, fluidic drag reduction, enhancing water supporting force, controlled transportation of fluids, superhydrophobic valves, battery and fuel cell applications, prevention of water corrosion and oil-water separation corrosion protective coatings, preventing adhesion of water and snow to windows or antennas, self-cleaning, enhancing buoyancy, and coating films for electronic devices [2 - 8] .
The phenomenon of superhydrophobicity was first studied by Johnson and Dettre [7] in 1964 using rough hydrophobic surfaces. They developed a theoretical model based on experiments with glass beads coated with paraffin and polytetrafluoroethylene telomere, respectively. Barthlott and Ehler [9] studied the self-cleaning property of superhydrophobic micro-nanostructured surfaces in 1977, and they described such self-cleaning and superhydrophobic properties for the first time as the “lotus effect”. The superhydrophobic state of a surface is defined by the contact angle between a water droplet and the surface of a material that has a WCA above 150°. Superhydrophobic surfaces display a self-cleaning effect (water repellent) widely known as the “lotus effect.” Superhydrophobicity can be achieved either by selecting low surface energy materials or by introducing roughness [9 - 14] .
Activated carbons, graphite, carbon fibers (CFs), fullerenes, carbon nanofibers (CNFs) (carbon nanotubes [CNTs], graphite nanofibers [GNFs]), micro-/meso-porous carbon, and, more recently, graphene carbon-based materials have emerged as extremely promising materials for various types of applications owing to their outstanding electronic and optical properties [15 - 28] . Recently, carbon-based superhydrophobic surfaces have been fabricated because of their promising applications such as conductive-transparent films, oil-water separation, and electromagnetic- interference-shielding [29 - 49] . In general, small water droplets on CF fabrics will be up to 120°, but not much greater for a flat surface.
To enhance the hydrophobicity of carbon-based materials, two approaches have been established recently [30 - 33] . First, research on superhydrophobic carbon-based materials has focused on increasing surface roughness by introducing geometric surface area.
Dip-coatings methods are also often employed to obtain superhydrophobic surfaces. As demonstrated by Nguyen et al . [31] , iterative dip coating of a foam in a graphene solution allows desired amounts of graphene sheets to be deposited on the pore-wall surface of melamine foams, rendering the foams superhydrophobic and superoleophilic, with a WCA of 162° and a chloroform absorption capacity of 165 times their own weight (1.86 ton m −3 ) [31 , 50 - 52] . Second, various functional groups or additional organic/inorganic materials can be introduced to remarkably vary surface wettability [53 - 55] . For example, Zeng et al . [32] and Charinpanitkul et al . [52] reported a simple method to produce CNT-based films with exceptional superhydrophobicity and impact icephobicity based on deposition of acetone-treated single-walled CNTs (SWCNTs) onto glass substrates. The acetone-functionalized films showed a strong ability to mitigate ice accretion from supercooled water droplets (−8℃), and the droplets were found to bounce off the films tilted at 30°. The untreated nanotubes films did not display similar behavior, and the supercooled water droplets remained attached to the films’ surfaces. Such studies could serve as the foundation of highly versatile technologies for both water and ice mitigation.
Most current research on carbon-based materials has focused on their electrical, physiochemical, and mechanical properties [56 - 58] . In particular, surface properties such as robustness against environmental contamination are critical design considerations if intrinsic properties are to be maintained. Herein, we start by discussing the properties of carbon-based materials with superhydrophobic surfaces provided by emerging methods to create superhydrophobic surfaces with enhanced bulk properties. The recent advances in this field are summarized, including the wetting behavior of water on carbon materials such as CFs, CNTs, graphene, and amorphous carbons, and the formation of hierarchical structures and low surface energy chemical composition, with emphasis on fundamental understanding of related processes. Potential applications in energy, environmental remediation, and thermal management are also discussed [59 - 63] .
In this paper we discuss the recent theoretical advances in superhydrophobicity, the relation of superhydrophobicity to the more general type of “superphobic” surfaces, manufacturing methods to obtain superhydrophobicity with different kinds of carbon surfaces, and new potential applications of superhydrophobic carbon-based materials such as new energy technology, green engineering, underwater applications such as antifouling, and optical applications.
2. Theoretical Background
- 2.1. Surface roughness
Superhydrophobicity, as shown by lotus leaves, is an area that has received much interest in the past few years in relation to self-cleaning surfaces and other processes as well as in the design and production of artificial biomimetic surfaces [64 - 71] . Fig. 1 shows a structural diagram of the lotus effect [64] . The structures of a lotus leaf, i.e., branch-like nanostructures on top of micropapillae, have been carefully observed by scientists. These microscale-structures can induce superhydrophobic surfaces with large contact angles and low sliding angles. It is believed that this unique self-cleaning property is based on the surface lotus effect illustrated in Fig. 1 . The roughness is caused by the microscale papillae and nanoscale tomenta ( Figs. 1b - d ). To construct superhydrophobic carbon-based material surfaces, it is essential to understand the wetting behavior of water on the surface of the carbons.
PPT Slide
Lager Image
Lotus effect: (a) lotus leaf and beads; (b) scanning electron microscopy image of micropapillae present on the surface of a lotus leaf; (c) image of a water droplet on a lotus leaf (a); (d) structural diagram of micro- and nanostructure of a single micropapilla [43].
Superhydrophobic surfaces are generally expressed by the contact angle between a water droplet and the solid surface. Wenzel’s early works and later Cassie-Baxter’s work defined the importance of surface roughness and heterogeneity, which are now recognized as key parameters in the wettability of hydrophobic surfaces [65 , 66] . Wang et al . [71] and Yu et al . [72] showed that superhydrophobic lotus leaves have a specuticular wax with two scales of roughness (a: papillose epidermal cells around 10 μm; b: tubular wax crystals around 10 nm on the papillose epidermal cells).
Contact angle measurements, as described by Young in 1805, remain the most accurate method for determining the interaction energy between a liquid and solid in a condensed state at the minimum equilibrium distance of solid and liquid. When a droplet of water rests on a surface, the contact angle can be measured at the edge of the droplet ( Fig. 1 ). Fig. 2 shows the liquid droplet wetting behavior of the corresponding theory: (a) Young’s state, (b) Wenzel’s state, (c) Cassie-Baxter’s state, and (d) an example of re-entrant morphology [5 , 11 , 14] . More than 200 years ago, Young, identified in a recent biography as “the last man who knew everything” [73] , described the forces acting on a liquid droplet spreading on a flat surface ( Fig. 1a ).
PPT Slide
Lager Image
Liquid droplet spreading on (a) flat surface (b) and rough surface (b-d). Depending on the roughness of the surface, the droplet is either in the so-called (a) Young, (b) Wenzel, or (c) Cassie-Baxter state; (d) example of re-entrant morphology (color figure available online).
On flat surfaces, Young’s equation defines the contact angle (θ) depending on the solid-vapor, solid-liquid, and liquid-vapor surface tensions, as given in Eq. (1), where γSV is the interfacial tension between solid and vapor, γSL is the interfacial tension between solid and liquid, and γLV relates to the interfacial tension between liquid and vapor. Depending on the value of θ as measured by water, if θ is less than 90°, the surface is conventionally described as hydrophilic; if θ varies between 90° and 150°, the surface is hydrophobic; and if θ is greater than 150°, the surface is conventionally described as superhydrophobic [74 - 81] .
PPT Slide
Lager Image
Depending on the level of surface roughness, two different models can be distinguished. The first, shown in Fig. 2b , is Wenzel’s state. The droplet maintains contact with the surface and fills the asperities, and the surface area associated with the contact angle is increased by the roughness factor r.
PPT Slide
Lager Image
Wenzel’s state is described by Eq. (3).
PPT Slide
Lager Image
In Eq. (3), r is equal to the ratio between the actual surface area of the rough surface and the projected (apparent) area, where the non-dimensional surface roughness factor r > 1. r emphasizes the effect of the surface chemistry determined by the term cos θ , the non-dimensional surface roughness . When θ is less than 90°, an increase in the roughness factor r reduces θw but if θ is higher than 90°, an increase in roughness leads to an increase in θw .
If the droplet is suspended on the surface asperities and the liquid does not penetrate the protrusions of the surface features, then this case belongs to Cassie-Baxter’s model. In this model, the apparent contact angle is the result of all contributions of different phases [82] . In Eq. (4), f 1 and f 2 are the fraction of the projecting solid and vapor on the surface, respectively, and f 1 + f 2 = 1. Eq. (4) only applies to cases where the liquid only contacts the top of the surface. However, a more complex version of Eq. (4) is required when partial penetration of the grooves occurs because the pores are filled with air. The hydrophobicity is enhanced by the increases of the vapor fraction. Because the pores are filled with air, which is hydrophobic, the contact angle always increases, relative to the behavior seen on a flat substrate having an identical chemical composition [82] .
PPT Slide
Lager Image
From these two theories, it can be found that surface topography can enhance surface wettability on solid surfaces, whether they are hydrophobic or hydrophilic. This finding guides us to tune the surface wettability by controlling surface geometrical structures independently of the chemical composition [82 - 87] . On the other hand, the surface morphology was found to be an important parameter and more precisely “reentrant” structures are required to obtain such a superhydrophobic surface ( Fig. 2d ). These morphologies induce a negative Laplace pressure difference because they introduce a transition in the liquid-vapor interface from concave to convex, inducing a higher energy barrier between Wenzel’s states and Cassie-Baxter’ states [86 , 87] .
- 2.2. Modification of roughness of low surface energy materials
Based on the general contact angle theory of Wenzel, two main approaches have been developed to generate superhydrophobic surfaces. One is increasing the surface area on a microscopic scale of low surface energy materials, as described above in Section 2.1; the other is to fabricate a suitable surface roughness with certain materials and subsequently modify the as-prepared surface with low surface energy materials [88] . The latter method is no longer limited to low surface energy materials, and it can be extended to the fabrication of hydrophobic surfaces for many systems. Various low surface energy materials have been developed to modify microscopic scale surfaces to form superhydrophobic surfaces. Fluorinated compounds, silane, and long alkyl chain fatty acids are typical low surface energy compounds, and have the ability to endow various substrates (SiO 2 , TiO 2 , Al 2 O 3 , metals, polymers etc.) with high hydrophobicity. Fig. 3 shows various surface reactive molecules for low-surfaceenergy modifications [88 - 90] .
PPT Slide
Lager Image
Surface reactive molecules for low-surface-energy modifications. (a) Perfluorodecyltrichlorosilane; (b) polyethylene; (c) polytetrafluoroethylene; (d) polyvinyl chloride; (e) polyvinylidene fluoride; (f ) polysiloxane; (g) long alkyl chain thiols; (h) long alkyl chain thiols bearing benzoic acid (MUABA); (i) alkyl or fluorinated organic silanes; (j) long alkyl chain fatty acids; (k) alkyl chain modified aromatic azides; (l) perfluoroalkyl ethyl methacrylate; (m) poly(TMSMA-r-fluoroMA) (3-(trimethoxysilyl)propyl methacrylate (TMSMA) and fluoromonomer(®) bearing methacrylate moiety (fluoroMA)).
The surface energy is generally defined as the work required to build a unit of area of a given surface, using the sessile drop technique [91 , 92] . Numerous such theories have been developed by various researchers. These methods differ in several ways, in terms of derivation and convention for example. Most importantly, they differ in the number of components or parameters. Simpler methods containing fewer components simplify the system by converging the surface energy values into one number, whereas strict methods using more components are derived to distinguish various components of the surface energy. In addition, the total surface energy of solids and liquids depends on the different types of molecular interactions, such as the London dispersive and the polar or acid/base interactions, and is considered to be the sum of these independent components [92] .
In the early 1960s, Fowkes [93 , 94] introduced the concept of the surface free energy of a solid. The total surface free energy can be divided into the London dispersive and specific (or polar) components [93 - 95] .
PPT Slide
Lager Image
where γS is the total surface free energy, the subscript S represents a solid state, and γS L and γS SP are the London dispersive and specific (Debye, Keesom of van der Waals, H-bonding, π-bonding, and other small polar effects) components of the surface free energy of the constitutive elements. The London dispersive and specific components are determined by measuring the contact angles of two testing liquids with known London dispersive and specific components. The surface free energy of a solid can be determined on the basis of contact angle measurements using the geometric mean, according to Fowkes’ proposition based on a solid (subscript S)–liquid (L) droplet–air system, as described by the following equation [93] :
PPT Slide
Lager Image
where θ is the contact angle of a liquid droplet in the solid state. As reported in our previous work, the specific component γSSP is highly dependent on the surface functional groups, and the dispersive component γSL is largely dependent on the total electron density in the carbon [94] .
3. Superhydrophobicity on CFs
CFs have attracted considerable interest due to their electrical properties, thermal conductivity, and high strength, lending outstanding behavior in practical applications [96 - 101] . In many cases, the CF surface properties are a crucial factor in their performance. Their specific surface area, however, is not sufficiently large for them to serve as ideal electrochemical materials compared to other carbon nanomaterials. Superhydrophobicity is an effect where roughness and hydrophobicity combine to generate unusually hydrophobic surfaces [81 , 100 - 105] . Because CFs are intrinsically hydrophobic, surface treatment is usually required to induce a hydrophilic state prior to their practical use [106 - 108] . The pristine hydrophobicity of CFs hinders their widespread utilization, and research on potential applications of this material generally has been limited.
Bliznakov et al . [100] used a simple and inexpensive route for the fabrication of a superhydrophobic metal surface. First, carbon/carbon composite paper (Toray TGP-H) is electroplated with copper. The copper layer is rendered hydrophobic by self-assembling a monolayer of dodecanethiol. The surface topography required to induce superhydrophobic behavior is achieved by varying the plating bath composition (Cl-, polyethylene glycol, and bis (3-sulfopropyl) disulfide additives) and the time of deposition (this varies the effective thickness of the Cu layer). The surface morphology created by the original arrangement of the CFs in the Toray paper (diameter 8 μm, spacing 30 μm) does not produce superhydrophobic behavior. This is true for both continuous and incomplete copper coatings. Actual superhydrophobic behavior (large contact angles, 160-165°, and very small contact angle hysteresis, 2 to 3°) is achieved when a continuous copper layer is deposited on the CFs and secondary micrometer- range roughness is developed as a result of the formation of small copper crystallites (size ~1 μm).
Previous studies have mostly focused on post-treatment of the CF surface to render a chemical composition that promotes surface hydrophobicity. The Hsieh group has carried out research on developing superhydrophobic CFs. They demonstrated the influence of the fluorine/carbon (F/C) ratio on superhydrophobicity of CNFs prepared by a template-assisted synthesis ( Fig. 4a ) [109] . To functionalize the CNFs, the thermal chemical vapor deposition (CVD) method was used to deposit a fluorocarbon (using perfluorohexane as the precursor) coating on the surface of the CNFs at 100, 300, and 500℃. The resulting CNFs exhibited good water-repellent behavior owing to hydrophobic surface groups including −CF 2 and −CF 3 groups. The fluorocarbon coating improves the superhydrophobicity of the CNF array and an upward increase of contact angle of water with F/C ratio was observed, i.e., from 110° to 161°. The superhydrophobic behavior in this study can be explained by 1) the lower surface energies of fluorocarbon coated surfaces and 2) the highly rough CNF arrays. They also investigated a continuous forest of CNTs grown catalytically on microscaled polyacrylonitrile (PAN)-based CF through a catalytic chemical vapor deposition (CCVD) technique, using Ni nanoparticles and acetylene as a catalyst and a carbon source, respectively ( Fig. 4b ) [40] . The nanotubes were successfully branched and decorated onto the CFs at different axes, forming a micro/nano carbon structure. The superhydrophobic surfaces are based on regularly ordered CFs (8-10 μm in diameter) 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 finding sheds light on how the two-tier roughness surface induces superhydrophobicity, and how the presence of CNTs reduces the area fraction of a water droplet in contact with a carbon surface with two-tier roughness. They also used a hydrophobic coating of silica nanoparticles onto microscaled CFs and investigated the superhydrophobic behavior of composite nano/microstructures ( Fig. 4c ) [41] . The two-tier composite surfaces are based on regularly ordered CFs (8-10 μm in diameter) that are coated with SiO 2 nanoparticles with an average size of 300-500 nm. The microscale fiber is used here to provide primary surface roughness, while the silica nanoparticles lend secondary roughness, mimicking the lotus leaf in nature. Increasing the density of silica on CFs had significant effects on the enhancement of the static contact angle, decrease of the contact angle hysteresis, and superhydrophobic stability. Without any subsequent low-surface-energy treatment, the unique composites with two-tier roughness exhibited superhydrophobicity with a high contact angle of 162.5 ± 2.2° with water. The results can be attributed to the higher density of silica coating resulting in more tortuous three-phase contact lines, thus facilitating the self-cleaning effect.
PPT Slide
Lager Image
Illustration of the fabrication process for superhydrophobic carbon fiber (CF) surfaces (a) fluorinated carbon nanofibers (CNFs); (b) fluorinated CNFs/CF fabric with two-tier roughness; (c) SiO2 nanoparticle coated CF composite with two-tier roughness. CCVD: catalytic chemical vapor deposition
The aforementioned method for the growth of CNTs on CF surfaces has some drawbacks. For example, at the high synthesis temperature, the metal catalysts easily aggregate into large particles and form different kinds of carbon nanomaterials. In addition, these processes require purity to attain adequate superhydrophobic and electrochemical properties [104] . Park et al . [102] reported that high-density carbon nanomaterials can be prepared by the decomposition of C 2 H 2 on CF surfaces coated with Ni-doped mesoporous silica films at high temperature to enhance the electrical conductivity of CFs [102 - 105] . This method is more effective than the traditional methods that involve such tasks as controlling the diameter of the carbon nanomaterials, enhancing the contact between the carbon nanomaterials and the CF surface, and eliminating the purification requirement of catalysts. In addition, the Park group fabricated superhydrophobic electrochemical CFs with double-scale roughness by the growth of GNFs on CF surfaces ( Fig. 5 ). Highdensity GNFs were synthesized by chemical decomposition of C 2 H 2 on CF surfaces coated with a Ni-doped mesoporous TiO 2 film at lower temperature. Scanning electron microscopy (SEM) images indicated that GNFs with an average diameter of 40 nm grew uniformly and densely on CF surfaces ( Figs. 5a - d ). The contact angle of the CF surfaces increased from 27.2 to 153.5° after growth of GNFs and coating of a fluoropolymer (FP) ( Figs. 5e - h ). Deionized water, diiodomethane, ethylene glycol, and glycerol were selected for measurement of the contact angle of CFs. Table 1 shows the dispersive ( γSL ), polar ( γSSP ), and surface free energy ( γS ) components of wetting liquids used in Park’s work: pristine CFs, oxidized CF-H, Ni-doped mesoporous TiO 2 film coated CFs, FP coated CFs, GNF coated CFs, and FP coated CF-GNFs. It is shown that the surface treatments significantly affect the surface energy of the CFs. The total surface free energy, γSL + γSSP , for CFs before the chemical treatment was determined to be 50.1 mJ/m 2 ( γSL = 44.5 mJ/m 2 , gS SP = 5.6 mJ/m 2 ). The total surface energy of CF-H increased after oxidation treatment; this is due to an increase of hydrophilic functional groups (–OH, C=O, and O=C–O) during the acid oxidation process. On the contrary, the fluorinated CF-FP shows lower surface energy. The decrease of both γSL and γSSP is ascribed to the substitution of the lower energy –C-F- groups of FP. The total surface free after the growth of GNFs decreased to 11.85 mJ/m 2 ( γSL = 6.45 mJ/m 2 , γSSP = 5.4 mJ/m 2 ). This decreased surface free energy is due to the hydrophobic surface of the GNFs. In the case of CF-GNF-FP, the surface free energy decreases significantly after grafting the FP onto their surface. This provides evidence that the combined effect of double-scaled roughness and low-surface-energy treatment minimizes surface energy.
PPT Slide
Lager Image
Scanning electron microscopy (a-h) and transmission electron microsocpy (i and j) images of carbon fibers (CFs) (a-c) pristine CFs; (d) Ni-doped mesoporous TiO2 film coated CFs; (e-j) graphite nanofibers coated CFs.
Dispersive (γSL), polar (γSSP), and surface free energy (γS) components of wetting liquids used in Park’s work: pristine CFs, oxidized CF-H, Ni-doped mesoporous TiO2film coated CF, fluoropolymer coated CFs, GNF coated CFs, and fluoropolymer coated CF-GNF (unit: mJ m−2)
PPT Slide
Lager Image
CF: carbon fiber, GNF: graphite nanofiber, FP: fluoropolymer
Lu et al. [110] synthesized CFs and SiCO/carbon composite fibers with average diameters of 120 and 163 nm, respectively, by electrospinning 7 wt% PAN and 5/7 wt% polyureasilazane (PUS)/ PAN in dimethylformamide (DMF), respectively, followed by cross-linking, stabilization, and carbonization at temperatures up to 1000℃. The SiCO/CFs exhibited dual superhydrophilicity (absorbing 873% water) and superoleophilicity (608% decane absorption). The electrochemical properties determined by cyclic voltammetry show that the SiCO/CFs possess better capacitance behaviors than CFs.
Seo et al. [111] fabricated nm-scale carbon structures on CFs with micrometer-scale thickness using the CVD method, where Ni nanoparticles were used as catalysts of nanostructure growth. Polydimethylsiloxane (PDMS) thin films were used to provide hydrophobic surface properties. To adjust the pH value of the aqueous solutions, HCl and NaOH were used for acidic and basic solutions, respectively. For both cases, the initial contact angle measured immediately after dropping 3 μL of liquid droplet was higher than 170°. With increasing contact time to 30 min, the contact angles were almost constant. This implies that the superhydrophobicity of PDMS-coated surfaces can be sustained in a corrosive environment.
Qiu et al . [112] fabricated a superhydrophobic CF layer. CFs with enhanced corrosion inhibition ability were catalytically grown on a Zn surface. Cu was produced by a galvanic replacement reaction, and acted as a catalyst for CF growth. CFs endow the Zn surface with superhydrophobic wettability (~150.5°), enabling it to withstand corrosion by the external environment. The Zn-CF material shows enhanced corrosion inhibition properties compared with bare Zn because of the air barrier originating from the superhydrophobic nature of the treated surface. The failure process of the superhydrophobic surface was monitored in situ using the open circuit potential technique. The perforations caused by capillary condensation decreased the superhydrophobicity of the surface and diminished its corrosion inhibition efficacy.
4. Superhydrophobicity on CNTs
CNTs, especially those with a cylindrical nanostructure, are of immense research interest for their outstanding behavior in practical applications such as nanotechnology, electronics, optics and other fields of materials science and technology [43 , 63 , 90 , 113 - 119] . However, in many cases, CNTs wettability and dispensability are crucial factors in their performance; example applications include reinforced polymer composites, templates, sensors, catalysts, electrode, etc. To date, many investigators have endeavored to fabricate CNTs having a superhydrophobic surface.
Previous studies have mostly focused on aligned CNTs films [43 , 90 , 117 - 119] . Zhu et al . [117] fabricated two model surfaces with two-tier scale roughness in a well-controlled manner and compared the superhydrophobicity and contact angle hysteresis of these surfaces with those of microscale rough surfaces by controlled growth of CNT arrays followed by coating with fluorocarbon layers formed by plasma polymerization. A schematic illustration describing surface roughness obtained by the methods investigated in this study is shown in Fig. 6 . Fig. 6a is a control (silicon I) surface fabricated by photolithography; Fig. 6b is a schematic representation of CNT arrays grown on silicon wafers, which are denoted as model surface II (WCA: 154~165°); Fig. 6c represents model surface III (WCA: 155~166°), where nanoscale roughness exists in the CNT array grooves. The only difference between surfaces II and III is the nanoscale roughness that exists in the CNT array grooves on surface III. These surfaces are coated with 20 nm fluorocarbon layers that have low surface energy and stabilize the CNT arrays. The CNT array size, pitch, and height have been varied to explore geometric effects on surface hydrophobicity. Compared to patterned Si surfaces with similar geometrical sizes, the nanoscale roughness does not significantly increase the apparent WCA; the microscale roughness thus determines the apparent WCA provided that the microscale roughness dominates the nanoscale roughness. Wong et al . [117] found that the introduction of nanoscale roughness can decrease the contact angle hysteresis to less than 1° and improve the stability of superhydrophobic surfaces. Furthermore, nanoscale roughness can also reduce the strict requirements of microscale roughness design for superhydrophobic surfaces. Introduction of nanoscale roughness on the groove bottom can decrease the microscale array height required for superhydrophobicity. These results improve the understanding of the effects of two-tier roughness on superhydrophobicity and offer additional design approaches for stable and robust superhydrophobic surfaces with self-cleaning properties.
PPT Slide
Lager Image
Schematic representations of (a) (I) microscale roughness created by photolithography, (II) aligned carbon nanotube (CNT) arrays that establish two-tier roughness, and (III) aligned CNT films on patterned silicon surfaces; (b) the process used to obtain switchable wettability on the CNT film.
Hong and Uhm [118] prepared superhydrophobic CNTs by low-pressure CF 4 glow plasma to provide roughness and fluorination to CNTs. The total surface free energy of CNT powder treated by CF 4 plasma for 20 min was calculated to be drastically decreased from 27.04 to 4.06 × 10 −7 mJ/m 2 . Superhydrophobic CNT powders were prepared by employing CF 4 glow discharge plasma to provide roughness and fluorination to CNT powders and water droplets bouncing on CNT powders were observed.
Luo et al . [43] fabricated a new flexible multifunctional CNT/ Nafion composite film with superhydrophobicity and high conductivity via a vacuum filtering method. The surface wettability of the nanocomposite film could be conveniently controlled by varying the filtering rate and the content ratio of Nafion to CNT in the composite solution. The films fabricated by filtering a 9.8 wt% Nafion composite solution with filtering rate of 0.5 mL/ min exhibited the highest WCA of 165.3 ± 1.9° and the smallest water sliding angle (SA) of 3.3 ± 0.7°. A fatigue test showed that the films retained the superhydrophobicity and the electric conductivity after 1000 bending cycles. The dramatic reduction of the anodic peak potential by the flexible CNT/Nafion nanocomposite films (CNNFs) electrode in cyclic voltammograms of β-nicotinamide adenine dinucleotide (NADH) demonstrates the strong potential of CNNFs in dehydrogenase-based biosensor applications.
It was recently reported that vertically aligned multi-walled CNT (VACNT) films produced by different techniques can present a hydrophobic character [120] . In particular, CO 2 laser irradiance was used to modify the CNT surface by decreasing the polar component of the surface energy. Ramos et al . [120] demonstrated the formation of stable superhydrophobic VACNT surfaces prepared through CO 2 laser irradiance, where the contact angle value reached 161°. VACNT arrays were synthesized by microwave plasma CVD using N 2 /H 2 /CH 4 . A CO 2 laser technique was applied on the VACNT surfaces with irradiance at different laser powers to promote the stability of the superhydrophobic surfaces. Contact angle measurement revealed that the irradiated VACNT surface is superhydrophobic at all irradiances tested. Unlike as-grown VACNTs, the samples treated with a CO 2 laser showed no sign of water seepage even after a prolonged period of time (~24 h). They also obtained superhydrophobic VACNT films by a microwave plasma CVD method. The values of the WCA changed to 35.7 ± 4.2º and to 142.2 ± 6.5º after CO 2 laser irradiance of 15 KW cm −2 and 50 KW cm −2 , respectively.
Stimuli-responsive smart surfaces with dynamically tunable wettability have recently received special attention because of their potential applications [121 - 123] . Yang et al . [121] fabricated various CNTs films with tunable wettability by a one-step spray-coating method without any chemical modification, where the wettability can be reversibly switched between superhydrophobic and superhydrophilic by alternation of UV irradiation and dark storage. The most distinctive characteristic of the film is its tunable wettability in response to UV light. When the CNT film was exposed to UV light for 40 min, the water CA was found to be about 0°; that is, it was switched from superhydrophobic to superhydrophilic. A water droplet can immediately spread out on the surface. After the UV-irradiated film had been in the dark for 24 h, its wettability recovered to the pristine superhydrophobic state ( Fig. 6b ).
Most of the current strategies for fabricating durable hydrophobic surfaces can provide contact angles close to 170° coupled with icephobicity [32 , 124] . Zheng et al . [32] presented a simple method to produce CNT-based films with exceptional superhydrophobicity and impact icephobicity by depositing acetone-treated SWCNTs onto glass substrates. This method is scalable and can be adopted for any substrate, both flexible and rigid. These films displayed a high contact angle, in the vicinity of 170°, verified by both static and dynamic analysis processes. Dynamic evaporation studies indicated that a droplet deposited on the treated films evaporated in the constant contact angle mode for more than 80% of the total evaporation time, which is characteristic of superhydrophobic surfaces. Furthermore, the acetone-functionalized films showed a strong ability to mitigate ice accretion from supercooled water droplets (−8°C); the droplets were found to bounce off the films tilted at 30°.
Recently, superhydrophobic transparent conductive films have attracted considerable interest due to their importance in fundamental research and potential industrial applications [48 , 125 - 127] . Meng and Park [125] prepared multi-walled CNT (MWCNT) thin films on glass substrates. The prepared films showed transparent, conductive, and superhydrophobic properties. MWCNTs were dispersed in FP solutions for modification of their surface by grafting a FP ( Fig. 7 ). A dip-coating process was used to prepare the films at a continuous speed and different numbers of coatings were applied. Fig. 7 shows schematic diagrams illustrating the changes of the contact angle and the surface properties of the film. As shown in this figure, the water droplet retains an ellipsoidal shape on the MWCNTs with a contact angle of 130°, suggesting the raw MWCNT materials have a hydrophobic character ( Fig. 7a ). The sharp decrease of the CA from 130° to 41.9° for MWCNT-OH ( Fig. 7b ) originates from the hydrophilic properties of the fully H 2 O 2 treated surface. This is due to an increase of hydrophilic functional groups (–OH, C=O, and O=C–OH) during the H 2 O 2 oxidation process [21] . The CA of glass increases to 117.5° after being coated with FP, and this is ascribed to the surface of the glass being coated with densely packed –CF 3 groups ( Fig. 7c ). The CA of MWCNTs-OH after treatment with the FP increased to 160.2°, and the surface showed superhydrophobicity ( Fig. 7d ). The CA was 160.2° even at a transmittance of 83.5% (at 550 nm) and a sheet resistance of 1.38 × 10 4 Ω sq −1 . This clearly indicates that the networks comprised of MWCNTs increase the conductivity while those containing the FP did not affect the conductivity of the films.
PPT Slide
Lager Image
Preparation procedure of FP modified MWCNTs and Illustrating the changes of water contact angle of the films. (a) pristine MWCNTs coated films; (b) oxidized MWCNTs-OH coated films; (c) FP coated films; (d) MWCNTs-FP coated films (at the volume ratio of MWCNTs/FP =10:3 and 7 coating times).
Tang et al . [128] functionalized covalently MWCNTs with polyhedral oligomeric silsequioxane (POSS). A stable and morpholsuperhydrophobic surface characteristic was observed for the film made of MWCNTs grafted with POSS (MWCNT-g-POSS) even after exposure to a high-humidity environment for three weeks. The WCA of the sample was measured to be 160.5 ± 1.1°. In addition, MWCNT-g-POSS buckypaper exhibited better efficiency in fire retardancy compared to the MWCNT buckypaper. This was due to the smaller median pore size of the MWCNT-g-POSS hybrid buckypaper and char formation during combustion, which could effectively limit the heat and mass transfer and the diffusion of flammable gases and therefore slow down the combustion and degradation of the resin.
5. Superhydrophobicity on Graphene
Graphene is a single-atom-thick sheet composed of sp 2 -hybridized carbon atoms and it exhibits many intriguing properties [48 , 127 - 130] . A perfect graphene nanosheet is hydrophobic, but surface treatment or introduction of various functional groups or additional components will remarkably vary its surface properties. Graphene has aroused strong interest in the context of exploring novel functional superhydrophobic surfaces [30] . Several experimental and modeling studies have focused on exploiting micro-scale surface roughness to engineer superhydrophobic graphene. Several research groups have fabricated superhydrophobic graphene surfaces using an irregular stack of graphene oxides (GO) prepared by chemical oxidation of graphite, and pertinent results are shown in Table 2 [131 - 144] .
List of graphene-based superhydrophobic surfaces
PPT Slide
Lager Image
WCA: water contact angle, POSS: polyhedral oligomeric silsequioxane, PVDF: polyvinylidene fluoride, HFP: hexafluoropropylene, PDMS: polydimethylsiloxane, CVD: chemical vapor deposition, GO: graphene oxide.
Rafiee et al . [131] demonstrated that a surface roughness effect in conjunction with the surface chemistry of graphene sheets can be used to dramatically alter the wettability of a substrate. In order to disperse graphene sheets on a substrate, they performed high-power ultrasonication of graphene sheets in water or acetone. By controlling the relative proportion of acetone and water in the solvent, the contact angle of the resulting graphene film can be tailored over a wide range (from superhydrophobic to superhydrophilic). Such graphene-based coatings with controllable wetting properties provide a facile and effective means to modify the wettability of a variety of surfaces.
Lin et al . [133] prepared a novel superhydrophobic graphene aerogel (GA) with extremely low bulk density and a high WCA. GA offers lower density and simpler processing than other superhydrophobic surfaces developed using vertically aligned CNTs or silica aerogels. They demonstrated that the GA is naturally hydrophobic because of its high surface roughness; following the application of a fluorinated silane, it becomes superhydrophobic with the WCA reaching 160°.
As shown in Fig. 3 , fluorinated polymers are commonly used as low surface energy materials; for example, polyvinylidene fluoride (PVDF) is used to produce superhydrophobic materials [134 - 136] . Zha et al . [135] demonstrated a combined method of solvent exchanging and freeze-drying to fabricate PVDF porous materials that can effectively avoid the skin-layer formation of dried materials. It was observed that the addition of graphene (1 wt%) exerted clear influences on the crystallization, morpholsuperhydrophobic ogy, surface area, and wettability of PVDF. PVDF/graphene (1 wt%) porous materials are a superhydrophobic material with a large contact angle (>150°). These properties are due to it being a hybrid porous material composed of strings of roughened nanospheres (250-300 nm) with hierarchical micro-/nano-scaled roughness. On the basis of the Cassie-Baxter model, such multilevel surface roughness is responsible for its superhydrophobicity. Zhang et al . [136] demonstrated the fabrication of hybrid PVDF-hexafluoropropylene (HFP)/graphene composite microspheres through a spontaneous formation process. The addition of graphene to a PVDF-HFP/DMF solution has a strong influence on its gel structure in both the wet and dry states. Morphological characterization by SEM indicates that the dried gel is composed of PVDF-HFP/graphene (0.25 wt% to PVDF-HFP) microspheres with a size distribution of 8~10 μm. The contact angles of pure PVDF-HFP and PVDF-HFP/graphene are 132.7 ± 2.7° and 151.6 ± 1.4°, respectively. This superhydrophobicity is due to the PVDF-HFP/graphene gel being composed of microspheres with nanoscaled surface roughness.
Usually, the micro-/macro-scale surface structures of functional films strongly affect the critical properties, such as wettability, and they should exhibit super water repellency with a WCA larger than 150° for self-cleaning and antimicrobial surfaces. Choi and Park [137] demonstrated superhydrophobic thin films of graphene-based materials induced by a hierarchically petal-like structure. The superhydrophobic graphene/Nafion nano hybrid films were prepared by controlling the structures with respect to the chemical composition from an interpenetrating networked and compactly interlocked structure (specific surface area of 9.56 m 2 /g) to a hierarchical petal-like, porous structure (specific surface area of ~ 413 m 2 /g). The hybrid films revealed a petal-like, porous structure with hierarchical roughness, where microscale roughness was produced in the lateral direction of the hybrid sheets while nanoscopic roughness was created on the edges of the hybrid sheets. The surface morphologies of the hybrids were changed with respect to the amount of Nafion and their CAs increased from ~97° to ~161° with increasing Nafion content.
Shanmugharaj et al . [141] demonstrated a facile method for the synthesis of amine functionalized GO films using alkyl-amines of varying chain lengths. Alkylamines consisting of hydrophobic long chain alkyl groups and hydrophilic amine groups were chemically reacted to the GO surface via two types of reactions viz. 1) An amidation reaction between amine groups and carboxylic acid sites of GO, and 2) a nucleophilic substitution reactions between amine and epoxy groups on the GO surface. Alkylamine-modified GO surfaces showed enhanced roughness, and this effect was more pronounced with increasing amine chain length. WCA measurements revealed that the hydrophobic nature of graphene depended on the chain length of the grafted alkylamines, and this may be corroborated to a decrease in the surface energy values. Grafting of long chain alkylamines such as hexadecylamine or octadecylamine on the GO surface followed by thermal reduction resulted in the formation of superhydrophobic surfaces with WCA values of 152° and 162°, corroborating the role of alkylamine chain length in superhydrophobic wetting control of a thermally annealed GO surface.
Singh et al . [143] used Teflon coated graphene building blocks to create a superhydrophobic structure with an ordered pore structure of ~200 μm in dimension. The advancing WCA on the foam surface exceeded 163°. The graphene foam inherits the pore structure of the Ni foam template used in the CVD growth process. This method can be used to uniformly tune the pore size and structure of the graphene foam by selecting the appropriate Ni foam template. The graphene foam can store elastic strain energy as it is deformed by the impacting drop and then deliver it back to the drop, which could assist the rebound process.
6. Superhydrophobicity on Other Carbons
There has been a continuous growth of interest throughout the world in synthesizing porous carbons to fabricate superhydrophobic films, in addition to CFs, CNFs, CNTs, and graphene. A typical method to control the wettability of a solid is surface modification with low surface energy materials. Superhydrophobic surfaces can then be fabricated successfully with micro- or nanostructured surfaces. As an environmentally benign and economically viable optoelectronic device material, superhydrophobic amorphous carbon films are of interest in various applications [35 , 145 - 147] .
Zhou et al . [35] prepared amorphous carbon films with a nanostructured surface and deposited the films on silicon and glass substrates at different substrate temperatures through a magnetron sputtering technique. The pure carbon films exhibited different wettability, ranging from hydrophilicity with WCA less than 40° to superhydrophobicity with a WCA of 152°. This reveals that the surface wettability of WCA films amorphous carbon films can be controlled well by using nanostructures with various geometrical and carbon state features. The graphite-like carbon film deposited at 400℃ without any modification exhibited super-hydrophobic properties, due to the combination of microstructures of spheres with nanostructures of protuberances and interstitials.
Li et al . [145] demonstrated that the wettability of a Pt/carbon/ Nafion catalyst layer in proton exchange membrane fuel cells is critical to their performance and durability, especially with respect to the cathode, as water is needed to transport protons to the active sites and is also involved in deleterious Pt nanoparticle dissolution and carbon corrosion. They used the water droplet impacting method to determine the wettability of 100% Nafion films as a benchmark, and then prepared Vulcan carbon (VC)/Nafion composite films. Spin-coating in a Pt-free state was used for both cases. The wettability of the VC/Nafion composite films depends significantly on the VC/Nafion mass ratios, even though Nafion is believed to be preferentially oriented (sulfonate groups toward VC) in all cases. At low VC contents, a significant water droplet contact angle hysteresis is seen, similar to pure Nafion films, while at higher VC contents (>30%), the films become hydrophobic, also exhibiting superhydrophobicity, with surface roughness playing a significant role. At VC contents higher than 80% VC, the surfaces become wettable again as there is insufficient Nafion loading to fully cover the carbon surface. It is thus possible to calculate the Nafion:carbon ratio required for full coverage of carbon by Nafion.
Banerjee et al . [146] synthesized highly porous activated apcarbon with a large surface area and pore volume by KOH activation using commercially available activated carbon as a precursor. By modification with PDMS, highly porous activated carbon showed superhydrophobicity with a WCA of 163.6°. The changes in wettability of PDMS- treated highly porous activated carbon were attributed to the deposition of a low-surface-energy silicon coating onto activated carbon, which had microporous characteristics. Using a facile dip-coating method, superhydrophobic activated carbon-coated sponges were also fabricated. The sponges exhibited excellent absorption selectivity for the removal of a wide range of organics and oils from water, as well as recyclability, thus showing potential as efficient absorbents for the large-scale removal of organic contaminants or oil spills from water.
7. Summary
Carbon is a versatile material due to its porosity, conductivity, thermal conductivity, wide operating potential range, high chemical stability, and reasonable cost. In this review, we have presented different techniques for the preparation of superhydrophobic carbon-based materials such as CFs, CNFs/CNTs, graphene, amorphous carbons, and porous carbons. These superhydrophobic carbon-based materials hold great promise for the development of various industrial products. Overall, there are two traditional methods to control superhydrophobic surfaces: 1) surface micro-scale roughness; and 2) low surface energy materials treatment. Several technologies that can improve surface roughness and decrease surface energy have been developed, including thermal treatment, chemical modification with –(CH 2 ) n –CH 3 or (CF 2 ) n –CF 3 groups containing materials, CVD method, plasma treatment, an electro-spinning. From a commercial point of view, carbon-based superhydrophobic materials can be applied to smart surfaces with tunable wetting behavior in different stimuli-responsive environments. They have attracted considerable attention for applications in self-cleaning surfaces, anti-adhesive coatings, biosensors, microfluidics, and many other areas.
Acknowledgements
We acknowledge support by the Ministry of Environment under the Eco-Innovation Project and the Carbon Valley Project of the Ministry of Trade, Industry and Energy, Korea.
References
Qiao R , Zhang R , Zhu W , Gong P 2012 Lab simulation of profile modification and enhanced oil recovery with a quaternary ammonium cationic polymer J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2011.11.092 18 111 -
Lafuma A , Quere D 2003 Superhydrophobic states Nat Mater http://dx.doi.org/10.1038/nmat924 2 457 -
Feng XJ , Jiang L 2006 Design and creation of superwetting/antiwetting surfaces Adv Mater http://dx.doi.org/10.1002/adma.200501961 18 3063 -
Fei T , Chen H , Lin J 2014 Transparent superhydrophobic films possessing high thermal stability and improved moisture resistance from the deposition of MTMS-based aerogels Colloids Surf Physicochem Eng Aspects http://dx.doi.org/10.1016/j.colsurfa.2013.11.027 443 255 -
Wolfs M , Darmanin T , Guittard F 2013 Superhydrophobic fibrous polymers Polym Rev http://dx.doi.org/10.1080/15583724.2013.808666 53 460 -
Fowkes FM , Zisman WA 1964 Contact Angle, Wettability, and Adhesion (Advances in Chemistry Series Vol. 43) American Chemical Society Washington, DC
Johnson RE , Dettre RH , Fowkes FM , Zisman WA 1964 Contact angle hysteresis;Contact Angle, Wettability, and Adhesion (Advances in Chemistry Series Vol. 43) American Chemical Society Washington, DC http://dx.doi.org/10.1021/ba-1964-0043.ch007 112 -
Ahn CH , Baek Y , Lee C , Kim SO , Kim S , Lee S , Kim SH , Bae SS , Park J , Yoon J 2012 Carbon nanotube-based membranes: fabrication and application to desalination J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2012.04.005 18 1551 -
Barthlott W , Ehler N 1977 Raster-Elektronenmikroskopie der Epidermis-Oberflächen von Spermatophyten (Tropische und subtropische Pflanzenwelt Vol. 19) Akademie der Wiss. u.d. Literatur Mainz
Quéré D 2002 Rough ideas on wetting Physica A http://dx.doi.org/10.1016/S0378-4371(02)01033-6 313 32 -
Celia E , Darmanin T , Taffin de Givenchy E , Amigoni S , Guittard F 2013 Recent advances in designing superhydrophobic surfaces J Colloid Interface Sci http://dx.doi.org/10.1016/j.jcis.2013.03.041 402 1 -
Yong J , Yang Q , Chen F , Zhang D , Du G , Bian H , Si J , Yun F , Hou X 2014 Superhydrophobic PDMS surfaces with three-dimensional (3D) pattern-dependent controllable adhesion Appl Surf Sci http://dx.doi.org/10.1016/j.apsusc.2013.10.076 288 579 -
Taylor P 2011 The wetting of leaf surfaces Curr Opin Colloid Interface Sci http://dx.doi.org/10.1016/j.cocis.2010.12.003 16 326 -
Shirtcliffe NJ , McHale G , I. Newton M 2011 The superhydrophobicity of polymer surfaces: Recent developments J Polym Sci B http://dx.doi.org/10.1002/polb.22286 49 1203 -
Hassan AF , Youssef AM , Priecel P 2013 Removal of deltamethrin insecticide over highly porous activated carbon prepared from pistachio nutshells Carbon Lett http://dx.doi.org/10.5714/CL.2013.14.4.234 14 (4) 234 - 242
Song YI , Lee JW , Kim TY , Jung HJ , Jung YC , Suh SJ , Yang CM 2013 Performance-determining factors in flexible transparent conducting single-wall carbon nanotube film Carbon Lett http://dx.doi.org/10.5714/CL.2013.14.4.255 14 (4) 255 - 258
Kim SG , Park OK , Lee JH , Ku BC 2013 Layer-by-layer assembled graphene oxide films and barrier properties of thermally reduced graphene oxide membranes Carbon Lett http://dx.doi.org/10.5714/CL.2013.14.4.247 14 (4) 247 - 250
Choi WK , Kim BJ , Park SJ 2013 Fiber surface and electrical conductivity of electroless Ni-plated PET ultra-fine fibers Carbon Lett http://dx.doi.org/10.5714/CL.2013.14.4.243 14 (4) 243 - 246
Li B , Zhao Z , Gao F , Wang X , Qiu J 2014 Mesoporous microspheres composed of carbon-coated TiO2nanocrystals with exposed {0 0 1} facets for improved visible light photocatalytic activity Appl Catal B http://dx.doi.org/10.1016/j.apcatb.2013.10.027 147 958 -
Jain A , Jayaraman S , Balasubramanian R , Srinivasan MP 2014 Hydrothermal pre-treatment for mesoporous carbon synthesis: enhancement of chemical activation J Mater Chem A http://dx.doi.org/10.1039/C3TA12648J 2 520 -
Wu D , Li Y , Zhang Y , Wang P , Wei Q , Du B 2014 Sensitive electrochemical sensor for simultaneous determination of dopamine, ascorbic acid, and uric acid enhanced by amino-group functionalized mesoporous Fe3O4@graphene sheets Electrochim Acta http://dx.doi.org/10.1016/j.electacta.2013.11.033 116 244 -
Zhu Z , Hu Y , Jiang H , Li C 2014 A three-dimensional ordered mesoporous carbon/carbon nanotubes nanocomposites for supercapacitors J Power Sources http://dx.doi.org/10.1016/j.jpowsour.2013.07.086 246 402 -
Tao G , Zhang L , Hua Z , Chen Y , Guo L , Zhang J , Shu Z , Gao J , Chen H , Wu W , Liu Z , Shi J 2014 Highly efficient adsorbents based on hierarchically macro/mesoporous carbon monoliths with strong hydrophobicity Carbon http://dx.doi.org/10.1016/j.carbon.2013.09.037 66 547 -
Liu J , Yang T , Wang DW , Lu GQ , Zhao D , Qiao SZ 2013 A facile soft-template synthesis of mesoporous polymeric and carbonaceous nanospheres Nat Commun http://dx.doi.org/10.1038/ncomms3798 4 2798 -
Kim JM , Song IS , Cho D , Hong I 2011 Effect of carbonization temperature and chemical pre-treatment on the thermal change and fiber morphology of kenaf-based carbon fibers Carbon Lett http://dx.doi.org/10.5714/CL.2011.12.3.131 12 (3) 131 - 137
Lee S , Kim J , Ku BC , Kim J , Chung Y 2011 Effect of process condition on tensile properties of carbon fiber Carbon Lett http://dx.doi.org/10.5714/CL.2011.12.1.026 12 (1) 26 - 30
Asghar HMA , Hussain SN , Roberts EPL , Campen AK , Brown NW 2013 Pre-treatment of adsorbents for waste water treatment using adsorption coupled-with electrochemical regeneration J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2013.02.007 19 1689 -
Han M , Yun J , Kim HI , Lee YS 2012 Effect of surface modification of graphene oxide on photochemical stability of poly(vinyl alcohol)/graphene oxide composites J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2011.11.122 18 752 -
Cho D , Yoon SB , Cho CW , Park JK 2011 Effect of additional heat-treatment temperature on chemical, microstructural, mechanical, and electrical properties of commercial PAN-based carbon fibers Carbon Lett http://dx.doi.org/10.5714/CL.2011.12.4.223 12 (4) 223 - 228
Chen Z , Dong L , Yang D , Lu H 2013 Superhydrophobic graphenebased materials: surface construction and functional applications Adv Mater http://dx.doi.org/10.1002/adma.201302804 25 5352 -
Nguyen DD , Tai NH , Lee SB , Kuo WS 2012 Superhydrophobic and superoleophilic properties of graphene-based sponges fabricated using a facile dip coating method Energy Environ Sci http://dx.doi.org/10.1039/C2EE21848H 5 7908 -
Zheng L , Li Z , Bourdo S , Khedir KR , Asar MP , Ryerson CC , Biris AS 2011 Exceptional superhydrophobicity and low velocity impact icephobicity of acetone-functionalized carbon nanotube films Langmuir http://dx.doi.org/10.1021/la201548k 27 9936 -
Bayer IS , Steele A , Loth E 2013 Superhydrophobic and electroconductive carbon nanotube-fluorinated acrylic copolymer nanocomposites from emulsions Chem Eng J http://dx.doi.org/10.1016/j.cej.2013.01.023 221 522 -
Yao L , He J 2014 Recent progress in antireflection and self-cleaning technology: from surface engineering to functional surfaces Prog Mater Sci http://dx.doi.org/10.1016/j.pmatsci.2013.12.003 61 94 -
Zhou Y , Wang B , Song X , Li E , Li G , Zhao S , Yan H 2006 Control over the wettability of amorphous carbon films in a large range from hydrophilicity to super-hydrophobicity Appl Surf Sci http://dx.doi.org/10.1016/j.apsusc.2006.05.118 253 2690 -
Chen CH , Cai Q , Tsai C , Chen CL , Xiong G , Yu Y , Ren Z 2007 Dropwise condensation on superhydrophobic surfaces with two-tier roughness Appl Phys Lett http://dx.doi.org/10.1063/1.2731434 90 173108 -
Li Y , Huang XJ , Heo SH , Li CC , Choi YK , Cai WP , Cho SO 2006 Superhydrophobic bionic surfaces with hierarchical microsphere/SWCNT composite arrays Langmuir http://dx.doi.org/10.1021/la0620758 23 2169 -
Wang Z , Lopez C , Hirsa A , Koratkar N 2007 Impact dynamics and rebound of water droplets on superhydrophobic carbon nanotube arrays Appl Phys Lett http://dx.doi.org/10.1063/1.2756296 91 023105 -
Zhou XH , Cui GL , Zhi LJ , Zhang SS 2007 Large-area helical carbon microcoils with superhydropho-bicity over a wide range of pH values New Carbon Mater 22 1 -
Hsieh CT , Chen WY , Wu FL 2008 Fabrication and superhydrophobicity of fluorinated carbon fabrics with micro/nanoscaled two-tier roughness Carbon http://dx.doi.org/10.1016/j.carbon.2008.04.026 46 1218 -
Hsieh CT , Wu FL , Yang SY 2008 Superhydrophobicity from composite nano/microstructures: carbon fabrics coated with silica nanoparticles Surf Coat Technol http://dx.doi.org/10.1016/j.surfcoat.2008.07.006 202 6103 -
Li J , Sambandam S , Lu W , Lukehart CM 2008 Carbon nanofibers “spot-welded” to carbon felt: a mechanically stable, bulk mimic of lotus leaves Adv Mater http://dx.doi.org/10.1002/adma.200700444 20 420 -
Luo C , Zuo X , Wang L , Wang E , Song S , Wang J , Wang J , Fan C , Cao Y 2008 Flexible carbon nanotube: polymer composite films with high conductivity and superhydrophobicity made by solution process Nano Lett http://dx.doi.org/10.1021/nl802411d 8 4454 -
Ma M , Hill RM , Rutledge GC 2008 A review of recent results on superhydrophobic materials based on micro- and nanofibers J Adhes Sci Technol http://dx.doi.org/10.1163/156856108X319980 22 1799 -
Srinivasan S , Praveen VK , Philip R , Ajayaghosh A 2008 Bioinspired superhydrophobic coatings of carbon nanotubes and linear π systems based on the “bottom-up” self-assembly approach Angew Chem Int Ed http://dx.doi.org/10.1002/anie.200802097 47 5750 -
Wang N , Xi J , Wang S , Liu H , Feng L , Jiang L 2008 Long-term and thermally stable superhydrophobic surfaces of carbon nanofibers J Colloid Interface Sci http://dx.doi.org/10.1016/j.jcis.2008.01.005 320 365 -
Xiao X , Cheng YT , Sheldon BW , Rankin J 2008 Condensed water on superhydrophobic carbon films J Mater Res http://dx.doi.org/10.1557/JMR.2008.0260 23 2174 -
Zou J , Chen H , Chunder A , Yu Y , Huo Q , Zhai L 2008 Preparation of a superhydrophobic and conductive nanocomposite coating from a carbon-nanotube-conjugated block copolymer dispersion Adv Mater http://dx.doi.org/10.1002/adma.200703094 20 3337 -
Bai BC , Cho S , Yu HR , Yi KB , Kim KD , Lee YS 2013 Effects of aminated carbon molecular sieves on breakthrough curve behavior in CO2/CH4separation J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2012.10.016 19 776 -
Ghaedi M , Montazerozohori M , Sajedi M , Roosta M , Nickoosiar Jahromi M , Asghari A 2013 Comparison of novel sorbents for preconcentration of metal ions prior to their flame atomic absorption spectrometry determination J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2013.02.020 19 1781 -
Ghaedi M , Montazerozohori M , Rahimi N , Biysreh MN 2013 Chemically modified carbon nanotubes as efficient and selective sorbent for enrichment of trace amount of some metal ions J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2013.01.011 19 1477 -
Charinpanitkul T , Suthabanditpong W , Watanabe H , Shirai T , Faungnawakij K , Viriya-empikul N , Fuji M 2012 Improved hydrophilicity of zinc oxide-incorporated layer-by-layer polyelectrolyte film fabricated by dip coating method J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2012.02.003 18 1441 -
Bai BC , Kim JG , Im JS , Jung SC , Lee YS 2011 Influence of oxyfluorination on activated carbon nanofibers for CO2storage Carbon Lett http://dx.doi.org/10.5714/CL.2011.12.4.236 12 (4) 236 - 242
Park SJ , Lee HY 2005 Effect of atmospheric-pressure plasma on adhesion characteristics of polyimide film J Colloid Interface Sci http://dx.doi.org/10.1016/j.jcis.2004.11.062 285 267 -
Chauhan NPS 2013 Structural and thermal characterization of macrobranched functional terpolymer containing 8-hydroxyquinoline moieties with enhancing biocidal properties J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2012.11.025 19 1014 -
Heo GY , Yoo YJ , Park SJ 2013 Effect of carbonization temperature on electrical conductivity of carbon papers prepared from petroleum pitch-coated glass fibers J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2012.11.028 19 1040 -
Lee JH , Kim IJ , Park SJ 2013 Preparation and electrochemical behaviors of styrene-acrylonitrile-based porous carbon electrodes Electrochim Acta http://dx.doi.org/10.1016/j.electacta.2013.09.006 113 23 -
Jin FL , Ma CJ , Park SJ 2011 Thermal and mechanical interfacial properties of epoxy composites based on functionalized carbon nanotubes Mater Sci Eng A http://dx.doi.org/10.1016/j.msea.2011.08.054 528 8517 -
Bikshapathi M , Verma N , Singh RK , Joshi HC , Srivastava A 2011 Preparation of activated carbon fibers from cost effective commercial textile grade acrylic fibers Carbon Lett http://dx.doi.org/10.5714/CL.2011.12.1.044 12 44 - 47
Abdullah ID , Girgis BS , Tmerek YM , Badawy EH 2011 Potential of activated carbon derived from local common reed in the refining of raw cane sugar Carbon Lett http://dx.doi.org/10.5714/CL.2010.11.3.192 11 (3) 192 - 200
Kaneko K , Arai M , Yamamoto M , Ohba T , Miyamoto JI , Kim DY , Tao Y , Yang CM , Urita K , Fujimori T , Tanaka H , Ohkubo T , Utsumi S , Hattori Y , Konishi T , Fujikawa T , Kanoh H , Yudasaka M , Hata K , Yumura M , Iijima S , Muramatsu H , Hayashi T , Kim YA , Endo M 2009 Fundamental understanding of nanoporous carbons for energy application potentials Carbon Lett http://dx.doi.org/10.5714/CL.2009.10.3.177 10 (3) 177 - 180
Lee SY , Park SJ 2013 TiO2photocatalyst for water treatment applications J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2013.07.012 19 1761 -
Lee SY , Yop Rhee K , Nahm SH , Park SJ 2014 Effect of p-type multi-walled carbon nanotubes for improving hydrogen storage behaviors J Solid State Chem http://dx.doi.org/10.1016/j.jssc.2013.11.026 210 256 -
Mao C , Liang C , Luo W , Bao J , Shen J , Hou X , Zhao W 2009 Preparation of lotus-leaf-like polystyrene micro- and nanostructure films and its blood compatibility J Mater Chem http://dx.doi.org/10.1039/B912314H 19 9025 -
Barthlott W , Neinhuis C 1997 Purity of the sacred lotus, or escape from contamination in biological surfaces Planta http://dx.doi.org/10.1007/s004250050096 202 1 -
Neinhuis C , Barthlott W 1997 Characterization and distribution of water-repellent, self-cleaning plant surfaces Ann Bot http://dx.doi.org/10.1006/anbo.1997.0400 79 667 -
Feng L , Li S , Li Y , Li H , Zhang L , Zhai J , Song Y , Liu B , Jiang L , Zhu D 2002 Super-hydrophobic surfaces: from natural to artificial Adv Mater http://dx.doi.org/10.1002/adma.200290020 14 1857 -
Jin M , Feng X , Feng L , Sun T , Zhai J , Li T , Jiang L 2005 Superhydrophobic aligned polystyrene nanotube films with high adhesive force Adv Mater http://dx.doi.org/10.1002/adma.200401726 17 1977 -
Wenzel RN 1936 Resistance of solid surfaces to wetting by water Ind Eng Chem http://dx.doi.org/10.1021/ie50320a024 28 988 -
Cassie ABD , Baxter S 1944 Wettability of porous surfaces Trans Faraday Soc http://dx.doi.org/10.1039/TF9444000546 40 546 -
Wang J , Chen H , Sui T , Li A , Chen D 2009 Investigation on hydrophobicity of lotus leaf: experiment and theory Plant Sci http://dx.doi.org/10.1016/j.plantsci.2009.02.013 176 687 -
Yu Y , Zhao ZH , Zheng QS 2007 Mechanical and superhydrophobic stabilities of two-scale surfacial structure of lotus leaves Langmuir http://dx.doi.org/10.1021/la7003485 23 8212 -
Robinson A 2006 The Last Man Who Knew Everything: Thomas Young, the Anonymous Polymath Who Proved Newton Wrong, Explained How We See, Cured the Sick, and Deciphered the Rosetta Stone, Among Other Feats of Genius Pi Press New York, NY
Lee MW , An S , Latthe SS , Lee C , Hong S , Yoon SS 2013 Electrospun polystyrene nanofiber membrane with superhydrophobicity and superoleophilicity for selective separation of water and low viscous oil ACS Appl Mater Interfaces http://dx.doi.org/10.1021/am404156k 5 10597 -
Chang CH , Hsu MH , Weng CJ , Hung WI , Chuang TL , Chang KC , Peng CW , Yen YC , Yeh JM 2013 3D-bioprinting approach to fabricate superhydrophobic epoxy/organophilic clay as an advanced anticorrosive coating with the synergistic effect of superhydrophobicity and gas barrier properties J Mater Chem A http://dx.doi.org/10.1039/C3TA12754K 1 13869 -
Gupta N , Kavya MV , Singh YRG , Jyothi J , Barshilia HC 2013 Superhydrophobicity on transparent fluorinated ethylene propylene films with nano-protrusion morphology by Ar + O2plasma etching: study of the degradation in hydrophobicity after exposure to the environment J Appl Phys http://dx.doi.org/10.1063/1.4826897 114 164307 -
Yu E , Lee HJ , Ko TJ , Kim SJ , Lee KR , Oh KH , Moon MW 2013 Hierarchical structures of AlOOH nanoflakes nested on Si nanopillars with anti-reflectance and superhydrophobicity Nanoscale http://dx.doi.org/10.1039/C3NR02395H 5 10014 -
Wu J , Li J , Deng B , Jiang H , Wang Z , Yu M , Li L , Xing C , Li Y 2013 Self-healing of the superhydrophobicity by ironing for the abrasion durable superhydrophobic cotton fabrics Sci Rep http://dx.doi.org/10.1038/srep02951 3 2951 -
Cao L , Liu J , Xu S , Xia Y , Huang W , Li Z 2013 Inherent superhydrophobicity of Sn/SnOx films prepared by surface self-passivation of electrodeposited porous dendritic Sn Mater Res Bull http://dx.doi.org/10.1016/j.materresbull.2013.08.044 48 4804 -
Timonen JV , Latikka M , Ikkala O , Ras RH 2013 Free-decay and resonant methods for investigating the fundamental limit of superhydrophobicity Nat Commun http://dx.doi.org/10.1038/ncomms3398 4 2398 -
Meng LY , Rhee KY , Park SJ 2014 Enhancement of superhydrophobicity and conductivity of carbon nanofibers-coated glass fabrics J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2013.08.015
Wang S , Song Y , Jiang L 2007 Photoresponsive surfaces with controllable wettability J Photochem Photobiol C http://dx.doi.org/10.1016/j.jphotochemrev.2007.03.001 8 18 -
Barthlott W , Schimmel T , Wiersch S , Koch K , Brede M , Barczewski M , Walheim S , Weis A , Kaltenmaier A , Leder A , Bohn HF 2010 The Salvinia paradox: superhydrophobic surfaces with hydrophilic pins for air retention under water Adv Mater http://dx.doi.org/10.1002/adma.200904411 22 2325 -
Cui XS , Li W 2010 On the possibility of superhydrophobic behavior for hydrophilic materials J Colloid Interface Sci http://dx.doi.org/10.1016/j.jcis.2010.03.065 347 156 -
Marmur A 2008 From hygrophilic to superhygrophobic: theoretical conditions for making high-contact-angle surfaces from low-contact-angle materials Langmuir http://dx.doi.org/10.1021/la800304r 24 7573 -
Liu JL , Feng XQ , Wang G , Yu SW 2007 Mechanisms of superhydrophobicity on hydrophilic substrates J Phys: Condens Matter http://dx.doi.org/10.1088/0953-8984/19/35/356002 19 356002 -
Herminghaus S 2000 Roughness-induced non-wetting Europhys Lett http://dx.doi.org/10.1209/epl/i2000-00418-8 52 165 -
Zhang X , Shi F , Niu J , Jiang Y , Wang Z 2008 Superhydrophobic surfaces: from structural control to functional application J Mater Chem http://dx.doi.org/10.1039/B711226B 18 621 -
Wang FJ , Li CQ , Tan ZS , Li W , Ou JF , Xue MS 2013 PVDF surfaces with stable superhydrophobicity Surf Coat Technol http://dx.doi.org/10.1016/j.surfcoat.2013.02.004 222 55 -
Liu H , Zhai J , Jiang L 2006 Wetting and anti-wetting on aligned carbon nanotube films Soft Matter http://dx.doi.org/10.1039/B606654B 2 811 -
Park SJ , Brendle M 1997 London dispersive component of the surface free energy and surface enthalpy J Colloid Interface Sci http://dx.doi.org/10.1006/jcis.1997.4763 188 336 -
Park SJ , Seo MK 2011 Solid-liquid interface Interface Sci Technol http://dx.doi.org/10.1016/B978-0-12-375049-5.00003-7 18 147 -
Fowkes FM 1962 Determination of interfacial tensions, contact angles, and dispersion forces in surfaces by assuming additivity of intermolecular interactions in surfaces J Phys Chem http://dx.doi.org/10.1021/j100808a524 66 382 -
Fowkes FM 1963 Additivity of intermolecular forces at interfaces. I. Determination of the contribution to surface and interfacial tensions of dispersion forces in various liquids J Phys Chem http://dx.doi.org/10.1021/j100806a008 67 2538 -
Park SJ , Cho MS , Lee JR 2000 Studies on the surface free energy of carbon-carbon composites: effect of filler addition on the ILSS of composites J Colloid Interface Sci http://dx.doi.org/10.1006/jcis.2000.6787 226 60 -
Mironov VS , Kim SY , Park M 2013 Electrical properties of polyethylene composite films filled with nickel powder and short carbon fiber hybrid filler Carbon Lett http://dx.doi.org/10.5714/CL.2013.14.2.105 14 (2) 105 - 109
Zhu J , Park SW , Joh HI , Kim HC , Lee S 2013 Preparation and characterization of isotropic pitch-based carbon fiber Carbon Lett http://dx.doi.org/10.5714/CL.2013.14.2.094 14 (2) 94 - 98
Jin FL , Lee SY , Park SJ 2013 Polymer matrices for carbon fiber-reinforced polymer composites Carbon Lett http://dx.doi.org/10.5714/CL.2013.14.2.076 14 (2) 76 - 88
Choi KE , Seo MK 2013 A study on the preparation of the eco-friendly carbon fibers-reinforced composites Carbon Lett http://dx.doi.org/10.5714/CL.2012.14.1.058 14 (1) 58 - 61
Bliznakov S , Liu Y , Dimitrov N , Garnica J , Sedev R 2009 Double-scale roughness and superhydrophobicity on metalized toray carbon fiber paper Langmuir http://dx.doi.org/10.1021/la803932k 25 4760 -
Park KM , Lee BS , Youk JH , Lee J , Yu WR 2013 Moisture condensation behavior of hierarchically carbon nanotube-grafted carbon nanofibers ACS Appl Mater Interfaces http://dx.doi.org/10.1021/am403348q 5 11115 -
Meng LY , Park SJ 2012 Effect of growth of graphite nanofibers on superhydrophobic and electrochemical properties of carbon fibers Mater Chem Phys http://dx.doi.org/10.1016/j.matchemphys.2011.11.024 132 324 -
Meng LY , Moon CW , Im SS , Lee KH , Byun JH , Park SJ 2011 Effect of Ni catalyst dispersion on the growth of carbon nanofibers onto carbon fibers Microporous Mesoporous Mater http://dx.doi.org/10.1016/j.micromeso.2010.10.008 142 26 -
Meng LY , Park SJ 2011 Effect of growth of carbon nanofibers on the electrical conductivity of carbon fibers Macromol Res http://dx.doi.org/10.1007/s13233-011-0209-1 19 209 -
Meng LY , Park SJ 2013 Influence of carbon nanofibers on electrochemical properties of carbon nanofibers/glass fibers composites Curr Appl Phys http://dx.doi.org/10.1016/j.cap.2012.10.008 13 640 -
Wang P , Zhang D , Qiu R , Wu J , Wan Y 2013 Super-hydrophobic film prepared on zinc and its effect on corrosion in simulated marine atmosphere Corros Sci http://dx.doi.org/10.1016/j.corsci.2012.10.025 69 23 -
Jung MJ , Kim JW , Im JS , Park SJ , Lee YS 2009 Nitrogen and hydrogen adsorption of activated carbon fibers modified by fluorination J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2008.11.001 15 410 -
Kim S , Kuk Y-S , Chung YS , Jin FL , Park SJ 2014 Preparation and characterization of polyacrylonitrile-based carbon fiber papers J Ind Eng Chem http://dx.doi.org/10.1016/j.jiec.2013.12.032
Hsieh CT , Chen JM , Huang YH , Kuo RR , Li CT , Shih HC , Lin TS , Wu CF 2006 Influence of fluorine/carbon atomic ratio on superhydrophobic behavior of carbon nanofiber arrays J Vac Sci Technol B http://dx.doi.org/10.1116/1.2150224 24 113 -
Lu P , Huang Q , Mukherjee A , Hsieh YL 2010 SiCO-doped carbon fibers with unique dual superhydrophilicity/superoleophilicity and ductile and capacitance properties ACS Appl Mater Interfaces http://dx.doi.org/10.1021/am100918x 2 3738 -
Seo H , Kim KD , Jeong MG , Kim Y , Choi K , Hong E , Lee K , Lim D 2012 Superhydrophobic carbon fiber surfaces prepared by growth of carbon nanostructures and polydimethylsiloxane coating Macromol Res http://dx.doi.org/10.1007/s13233-012-0029-y 20 (2) 216 - 219
Qiu R , Zhang D , Wang P 2013 Superhydrophobic-carbon fibre growth on a zinc surface for corrosion inhibition Corros Sci http://dx.doi.org/10.1016/j.corsci.2012.09.041 66 350 -
Kim KS , Park SJ 2013 Influence of carbon shell structure on electrochemical performance of multi-walled carbon nanotube electrodes Anal Chim Acta http://dx.doi.org/10.1016/j.aca.2013.05.047 788 17 -
Kim KS , Park SJ 2011 Influence of amine-grafted multi-walled carbon nanotubes on physical and rheological properties of PMMA-based nanocomposites J Solid State Chem http://dx.doi.org/10.1016/j.jssc.2011.09.012 184 3021 -
Choi Young Chul 2013 Micro-Raman characterization of isolated single wall carbon nanotubes synthesized using Xylene Carbon Lett http://dx.doi.org/10.5714/CL.2013.14.3.175 14 (3) 175 - 179
Ibrahim Khalid Saeed 2013 Carbon nanotubes-properties and applications: a review Carbon Lett http://dx.doi.org/10.5714/CL.2013.14.3.131 14 (3) 131 - 144
Zhu L , Xiu Y , Xu J , Tamirisa PA , Hess DW , Wong CP 2005 Superhydrophobicity on two-tier rough surfaces fabricated by controlled growth of aligned carbon nanotube arrays coated with fluorocarbon Langmuir http://dx.doi.org/10.1021/la051410+ 21 11208 -
Hong YC , Uhm HS 2006 Superhydrophobicity of a material made from multiwalled carbon nanotubes Appl Phys Lett http://dx.doi.org/10.1063/1.2210449 88 244101 -
Jung YC , Bhushan B 2009 Mechanically durable carbon nanotube: composite hierarchical structures with superhydrophobicity, selfcleaning, and low-drag ACS Nano http://dx.doi.org/10.1021/nn901509r 3 4155 -
Ramos SC , Vasconcelos G , Antunes EF , Lobo AO , Trava-Airoldi VJ , Corat EJ 2010 CO2laser treatment for stabilization of the superhydrophobicity of carbon nanotube surfaces J Vac Sci Technol B http://dx.doi.org/10.1116/1.3502024 28 1153 -
Yang J , Zhang Z , Men X , Xu X , Zhu X 2010 Reversible superhydrophobicity to superhydrophilicity switching of a carbon nanotube film via alternation of UV irradiation and dark storage Langmuir http://dx.doi.org/10.1021/la100355n 26 10198 -
Sun W , Zhou S , You B , Wu L 2013 Polymer brush-functionalized surfaces with unique reversible double-stimulus responsive wettability J Mater Chem A http://dx.doi.org/10.1039/C3TA12367G 1 10646 -
Cabane E , Zhang X , Langowska K , Palivan C , Meier W 2012 Stimuli-responsive polymers and their applications in nanomedicine Biointerphases http://dx.doi.org/10.1007/s13758-011-0009-3 7 1 -
Kulinich SA , Farzaneh M 2009 How wetting hysteresis influences ice adhesion strength on superhydrophobic surfaces Langmuir http://dx.doi.org/10.1021/la901439c 25 8854 -
Meng LY , Park SJ 2010 Effect of fluorination of carbon nanotubes on superhydrophobic properties of fluoro-based films J Colloid Interface Sci http://dx.doi.org/10.1016/j.jcis.2009.10.022 342 559 -
Han JT , Kim SY , Woo JS , Lee GW 2008 Transparent, conductive, and superhydrophobic films from stabilized carbon nanotube/silane sol mixture solution Adv Mater http://dx.doi.org/10.1002/adma.200800239 20 3724 -
Meng Long-Yue , Park Soo-Jin 2012 Improvement of superhydrophobicity of multi-walled CNTs produced by fluorination Carbon Lett http://dx.doi.org/10.5714/CL.2012.13.3.178 13 (3) 178 - 181
Tang Y , Gou J , Hu Y 2013 Covalent functionalization of carbon nanotubes with polyhedral oligomeric silsequioxane for superhydrophobicity and flame retardancy Polym Eng Sci http://dx.doi.org/10.1002/pen.23338 53 1021 -
Lee GH , Cooper RC , An SJ , Lee S , van der Zande A , Petrone N , Hammerberg AG , Lee C , Crawford B , Oliver W , Kysar JW , Hone J 2013 High-strength chemical-vapor-deposited graphene and grain boundaries Science http://dx.doi.org/10.1126/science.1235126 340 1073 -
Ramos SC , Vasconcelos G , Antunes EF , Lobo AO , Trava-Airoldi VJ , Corat EJ 2010 Total re-establishment of superhydrophobicity of vertically-aligned carbon nanotubes by Co2laser treatment Surf Coat Technol http://dx.doi.org/10.1016/j.surfcoat.2010.02.065 204 3073 -
Rafiee J , Rafiee MA , Yu ZZ , Koratkar N 2010 Superhydrophobic to superhydrophilic wetting control in graphene films Adv Mater http://dx.doi.org/10.1002/adma.200903696 22 2151 -
Jin J , Wang X , Song M 2011 Graphene-based nanostructured hybrid materials for conductive and superhydrophobic functional coatings J Nanosci Nanotechnol http://dx.doi.org/10.1166/jnn.2011.4730 11 7715 -
Lin Y , Ehlert GJ , Bukowsky C , Sodano HA 2011 Superhydrophobic functionalized graphene aerogels ACS Appl Mater Interfaces http://dx.doi.org/10.1021/am200527j 3 2200 -
Wang S , Yang Y , Zhang Y , Fei X , Zhou C , Zhang Y , Li Y , Yang Q , Song Y 2014 Fabrication of large-scale superhydrophobic composite films with enhanced tensile properties by multinozzle conveyor belt electrospinning J Appl Polym Sci http://dx.doi.org/10.1002/app.39735 131 39735 -
Zha DA , Mei S , Wang Z , Li H , Shi Z , Jin Z 2011 Superhydrophobic polyvinylidene fluoride/graphene porous materials Carbon http://dx.doi.org/10.1016/j.carbon.2011.07.032 49 5166 -
Zhang L , Zha DA , Du T , Mei S , Shi Z , Jin Z 2011 Formation of superhydrophobic microspheres of poly(vinylidene fluoride-hexafluoropropylene)/graphene composite via gelation Langmuir http://dx.doi.org/10.1021/la200982n 27 8943 -
Choi BG , Park HS 2012 Superhydrophobic graphene/nafion nanohybrid films with hierarchical roughness J Phys Chem C http://dx.doi.org/10.1021/jp207818b 116 3207 -
Wang JN , Shao RQ , Zhang YL , Guo L , Jiang HB , Lu DX , Sun HB 2012 Biomimetic graphene surfaces with superhydrophobicity and iridescence Chemistry http://dx.doi.org/10.1002/asia.201100882 7 301 -
Fan ZL , Qin XJ , Sun HX , Zhu ZQ , Pei CJ , Liang WD , Bao XM , An J , La PQ , Li A , Deng WQ 2013 Superhydrophobic mesoporous graphene for separation and absorption ChemPlusChem http://dx.doi.org/10.1002/cplu.201300119 78 1282 -
Li X , Li L , Wang Y , Li H , Bian X 2013 Wetting and interfacial properties of water on the defective graphene J Phys Chem C http://dx.doi.org/10.1021/jp4045258 117 14106 -
Shanmugharaj AM , Yoon JH , Yang WJ , Ryu SH 2013 Synthesis, characterization, and surface wettability properties of amine functionalized graphene oxide films with varying amine chain lengths J Colloid Interface Sci http://dx.doi.org/10.1016/j.jcis.2013.02.054 401 148 -
M Shateri-Khalilabad , M Yazdanshenas 2013 Preparation of superhydrophobic electroconductive graphene-coated cotton cellulose Cellulose http://dx.doi.org/10.1007/s10570-013-9873-y 20 963 -
Singh E , Chen Z , Houshmand F , Ren W , Peles Y , Cheng HM , Koratkar N 2013 Superhydrophobic graphene foams Small http://dx.doi.org/10.1002/smll.201201176 9 75 -
Wang P , Zhang D 2013 Super-hydrophobic film prepared with reduced graphene sheets and its application as corrosion barrier to copper Appl Mech Mater http://dx.doi.org/10.4028/www.scientific.net/AMM.365-366.1100 365-366 1100 -
Li X , Feng F , Zhang K , Ye S , Kwok DY , Birss V 2012 Wettability of Nafion and Nafion/Vulcan carbon composite films Langmuir http://dx.doi.org/10.1021/la300388x 28 6698 -
Banerjee D , Das NS , Chattopadhyay KK 2012 Enhancement of field emission and hydrophobic properties of silicon nanowires by chemical vapor deposited carbon nanoflakes coating Appl Surf Sci http://dx.doi.org/10.1016/j.apsusc.2012.07.148 261 223 -
Sun H , Li A , Zhu Z , Liang W , Zhao X , La P , Deng W 2013 Superhydrophobic activated carbon-coated sponges for separation and absorption ChemSusChem http://dx.doi.org/10.1002/cssc.201200979 6 1057 -