Formation of Water Layers on Graphene Surfaces

Reversible Constrained Dissociation and Reassembly of MXene Films

Enabling materials to undergo reversible dynamic transformations akin to the behaviors of living organisms represents a critical challenge in the field of material assembly. The pursuit of such capabilities using conventional materials has largely been met with limited success. Herein, the discovery of reversible constrained dissociation and reconfiguration in MXene films, offering an effective solution to overcome this obstacle is reported. Specifically, MXene films permit rapid intercalation of water molecules between their distinctive layers, resulting in a significant expansion and exhibiting confined dissociation within constrained spaces. Meanwhile, the process of capillary compression driven by water evaporation reinstates the dissociated MXene film to its original compact state. Further, the adhesive properties emerging from the confined disassociation of MXene films can spontaneously induce fusion between separate films. Utilizing this attribute, complex structures of MXene films can be effortlessly foamed and interlayer porosity precisely controlled, using only water as the inducer. Additionally, a parallel phenomenon has been identified in graphene oxide films. This work not only provides fresh insights into the microscopic mechanisms of 2D materials such as MXene but also paves a transformative path for their macroscopic assembly applications in the future.

Kinetics of Direct Reaction of Vanadate, Chromate, and Permanganate with Graphene Nanoplatelets for Use in Water Purification

Oxometalates of vanadium(V), chromium(VI), and manganese(VII) have negative impacts on water resources due to their toxicity. To remove them, the kinetics of 0.04 mM oxometalates in natural and synthetic water were studied using graphene nanoplatelets (GNP). The GNP were dispersible in water and formed aggregates >15 µm that could be easily separated. Within 30 min, the GNP were covered with ~0.4 mg/g vanadium and ~1.0 mg/g chromium as Cr(OH)3. The reaction of 0.04 mM permanganate with 50 mg of GNP resulted in a coverage of 10 mg/g in 5 min, while the maximum value was 300 mg/g manganese as Mn2O3/MnO. TEM showed a random metal distribution on the surfaces; no clusters or nanoparticles were detected. The rate of disappearance in aerated water followed a pseudo second-order adsorption kinetics (PSO) for V(V), a pseudo second-order reaction for Cr(VI), and a pseudo first-order reaction for Mn(VII). For Cr(VI) and Mn(VII), the rate constants were found to depend on the GNP mass. Oxygen sorption occurred with PSO kinetics as a parallel slow process upon contact of GNP with air-saturated water. For thermally regenerated GNP, the rate constant decreased for V(V) but increased for Cr(VI), while no effect was observed for Mn(VII). GNP capacity was enhanced through regeneration for V(V) and Cr(VI); no effect was observed for Mn(VII). The reactions are well-suited for use in water purification processes and the reaction products, GNP, decorated with single metal atoms, are of great interest for the construction of sensors, electronic devices, and for application in single-atom catalysis (SAC).

Molecular modeling study on the water-electrode surface interaction in hydrovoltaic energy

The global energy problem caused by the decrease in fossil fuel sources, which have negative effects on human health and the environment, has made it necessary to research alternative energy sources. Renewable energy sources are more advantageous than fossil fuels because they are unlimited in quantity, do not cause great harm to the environment, are safe, and create economic value by reducing foreign dependency because they are obtained from natural resources. With nanotechnology, which enables the development of different technologies to meet energy needs, low-cost and environmentally friendly systems with high energy conversion efficiency are developed. Renewable energy production studies have focused on the development of hydrovoltaic technologies, in which electrical energy is produced by making use of the evaporation of natural water, which is the most abundant in the world. By using nanomaterials such as graphene, carbon nanoparticles, carbon nanotubes, and conductive polymers, hydrovoltaic technology provides systems with high energy conversion performance and low cost, which can directly convert the thermal energy resulting from the evaporation of water into electrical energy. The effect of the presence of water on the generation of energy via the interactions between the ion(s) and the liquid-solid surface can be enlightened by the mechanism of the hydovoltaic effect. Here, we simply try to get some tricky information underlying the hydrovoltaic effect by using DFT/B3LYP/6-311G(d, p) computations. Namely, the physicochemical and electronic properties of the graphene surface with a water molecule were investigated, and how/how much these quantities (or parameters) changed in case of the water molecule contained an equal number of charges were analyzed. In these computations, an excess of both positive charge and negative charge, and also a neutral environment was considered by using the Na+, Cl-, and NaCl salt, respectively.

The First-Water-Layer Evolution at the Graphene/Water Interface under Different Electro-Modulated Hydrophilic Conditions Observed by Suspended/Supported Field-Effect-Device Architectures

Interfacial water molecules affect carrier transportation within graphene and related applications. Without proper tools, however, most of the previous works focus on simulation modeling rather than experimental validation. To overcome this obstacle, a series of graphene field-effect transistors (GFETs) with suspended (substrate-free, SF) and supported (oxide-supported, OS) configurations are developed to investigate the graphene-water interface under different hydrophilic conditions. With deionized water environments, in our experiments, the electrical transportation behaviors of the graphene mainly originate from the evolution of the interfacial water-molecule arrangement. Also, these current-voltage behaviors can be used to elucidate the first-water layer at the graphene-water interface. For SF-GFET, our experimental results show positive hysteresis in electrical transportation. These imply highly ordered interfacial water molecules with a separated-ionic distributed structure. For OS-GFET, on the contrary, the negative hysteresis shows the formation of the hydrogen-bond interaction between the interfacial water layer and the SiO₂ substrate under the graphene. This interaction further promotes current conduction through the graphene/water interface. In addition, the net current-voltage relationship also indicates the energy required to change the orientation of the first-layer water molecules during electro-potential change. Therefore, our work gives an insight into graphene-water interfacial evolution with field-effect modulation. Furthermore, this experimental architecture also paves the way for investigating 2D solid-liquid interfacial features.

Unraveling the hydrophobic interaction mechanisms of hydrocarbon and fluorinated surfaces

HYPOTHESIS

Numerous hydrocarbon and fluorine-based hydrophobic surfaces have been widely applied in various engineering and bioengineering fields. It is hypothesized that the hydrophobic interactions of hydrocarbon and fluorinated surfaces in aqueous media would show some differences.

EXPERIMENTS

The hydrophobic interactions of hydrocarbon and fluorinated surfaces with air bubbles in aqueous solutions have been systematically and quantitatively measured using a bubble probe atomic force microscopy (AFM) technique. Ethanol was introduced to water for modulating the solution polarity. The experimental force profiles were analyzed using a theoretical model combining the Reynolds lubrication theory and augmented Young-Laplace equation by including disjoining pressure arisen from the Derjarguin-Landau-Verwey-Overbeek (DLVO) and non-DLVO interactions (i.e., hydrophobic interactions).

FINDINGS

The experiment results show that the hydrophobic interactions were firstly weakened and then strengthened by increasing ethanol content in the aqueous media, mainly due to the variation in interfacial hydrogen bonding network. The fluorinated surface exhibited less sensitivity to ethanol than hydrocarbon surface, which is attributed to the presence of ordered interfacial water layer. Our work reveals the different hydrophobic effects of hydrocarbon and fluorinated surfaces, with useful implications on modulating the interfacial interactions of relevant materials in various engineering and bioengineering applications.

Interfacial Liquid Water on Graphite, Graphene, and 2D Materials

The optical, electronic, and mechanical properties of graphite, few-layer, and two-dimensional (2D) materials have prompted a considerable number of applications. Biosensing, energy storage, and water desalination illustrate applications that require a molecular-scale understanding of the interfacial water structure on 2D materials. This review introduces the most recent experimental and theoretical advances on the structure of interfacial liquid water on graphite-like and 2D materials surfaces. On pristine conditions, atomic-scale resolution experiments revealed the existence of 1-3 hydration layers. Those layers were separated by ∼0.3 nm. The experimental data were supported by molecular dynamics simulations. However, under standard working conditions, atomic-scale resolution experiments revealed the presence of 2-3 hydrocarbon layers. Those layers were separated by ∼0.5 nm. Linear alkanes were the dominant molecular specie within the hydrocarbon layers. Paradoxically, the interface of an aged 2D material surface immersed in water does not have water molecules on its vicinity. Free-energy considerations favored the replacement of water by alkanes.

Encoding Manipulation of DNA-Nanoparticle Assembled Nanorobot Using Independently Charged Array Nanopores

During the past decades, scientists have developed different kinds of nanorobots based on various driving principles to realize controlled manipulation of them for potential applications like medical diagnosis and directed cargo delivery. In order to design a nanorobot with advantages of simple operation and precise control that can enrich the family of intelligent nanorobots, an encoding manipulation method is proposed to control the movement of a DNA-nanoparticle assembled nanorobot by combing electrophoresis and electroosmosis effect in independently charged array nanopores. The nanorobot is composed of one nanoparticle and one or two ssDNAs. ssDNAs act as the legs of the nanorobot. The selective ion transport through charged nanopores can induce cooperation and competition between the electroosmosis and electrophoresis, which is the main power to activate the nanorobot. Thus by simply switching the applied electric field and surface charge density of each nanopore which is defined as the encoded nanopore according to a predetermined strategy, the well-controlled encoding manipulation including capturing, releasing, jumping, and crawling of the nanorobot is realized in this work. The study is expected to realize its value in many interesting applications like drug delivery, nanosurgery, and so on in the near future.

High Directional Water Transport Graphene Oxide Biphilic Stack

Understanding the nature of water transport in nanoscale is of high importance. Graphene properties such as mass flow rate, stability, filtration efficiency, and selectivity have been studied in various fields. It is a widely held view that the hydrophilicity of graphene oxide enhances the water transport properties. In this study, it is shown that despite this belief, a combination of graphene and graphene oxide can yield superior transport properties including high mass flow rate and directionality. Firstly, different membrane characteristics such as the smallest pore diameter for water molecules sieving and mass flow rate have been evaluated. Furthermore, a combination of graphene and graphene oxide, a biphilic stack of hydrophobic and hydrophilic layers, are used to evaluate the mass flow rates and results are compared with that of normal graphene oxide laminates. The proposed structure acts like a water diode i.e. conduct water molecules in a desired direction and increases the mass flow rate several times. The effect of interatomic potential, oxidation level and charge, and the spacing between layers on both mass flow rate and directionality are examined. It is found that an optimized structure conducts water in a desired direction and increases the mass flow rate up to 10 times for the small interlayer distance of 7 Å compared to the normal graphene oxide laminates. The given structures can be used in a wide range of filtration applications where selective water sieving with high mass flow rate is desired.

Water Adsorption Control by Surface Nanostructures on Graphene-Related Materials by Grand Canonical Monte Carlo Simulations

The interfaces of carbon materials play an important role in various technological and scientific research fields. Graphene is the fundamental unit of sp² carbon allotropes, and the evaluation of the interfacial properties of graphene-related materials is thus essential to clarify the molecular mechanisms occurring at the interfaces. Ideally, graphene is exclusively composed of sp² carbon atoms; however, some parts of graphene normally contain sp³ carbon atoms with oxygen functional groups, vacancy, and grain boundary defects, and these structural characteristics need to be considered to reveal the interfacial properties. Herein, we demonstrate the interfacial properties of graphene-related materials by analyzing the water adsorption properties of graphene, hydrogenated graphene (graphane), and partially oxidized graphene (named as graphoxide) using grand canonical Monte Carlo simulations. The hydrophobicity evaluated from the simulated water adsorption isotherms followed the order: graphane > graphene > graphoxide with 1% oxygen atomic ratio > graphoxide with 3% oxygen atomic ratio > graphoxide with 5% oxygen atomic ratio. The potential calculations between a single water molecule and graphoxides revealed that the presence of oxygen functional groups enhanced the hydrophilicity of graphoxide. This study also disclosed some differences between the hydrophobic interfaces of graphene and graphane, which have been rarely evaluated. Surprisingly, the hydrophobicity of graphane was higher than that of graphene despite the similar potential well depths between a water molecule and graphene/graphane. This was caused by the restriction of water orientation on graphane; water was preferentially adsorbed on the honeycomb center or concave sites in the initial adsorption, and it was hard to interact with neighboring water molecules. The different structures revealed for the graphene-related materials with nanoscale roughness played important roles in controlling the water vapor adsorption mechanism.

Ordered Water Layer on the Macroscopically Hydrophobic Fluorinated Polymer Surface and Its Ultrafast Vibrational Dynamics

Hydrophobic-like water monolayers have been predicted at the metal and some polar surfaces by theoretical simulations. However, direct experimental evidence for the presence of this water layer at surfaces, particularly at biomolecule and polymer surfaces, is yet to be validated at room temperature. Here we observe experimentally that an ordered molecular water layer is present at the hydrophobic fluorinated polymer such as polytetrafluoroethylene (PTFE) surface by using sum frequency generation vibrational spectroscopy. The macroscopic hydrophobicity of PTFE surface is actually hydrophilic at the molecular level. The macroscopically hydrophobic character of PTFE is indeed resulting from the hydrophobicity of the ordered two-dimension (2D) water layer, in which cyclic water tetramer structure is found. The water layer at humidity of ≤40% has a vibrational relaxation time of 550 ± 60 fs. The vibrational relaxation time in the frequency range of 3200-3400 cm^-1 shows remarkable difference from the interfacial water at the air/H₂O interface and the lipid/H₂O interface. No discernible frequency dependence of the vibrational relaxation time is observed, indicating the homogeneous dynamics of OH groups in the water layer. These insights into the water layer at the macroscopically hydrophobic surface may contribute to a better understanding of the hydrophobic interaction and interfacial water dynamics.

In Situ Atomic-Scale Imaging of Interfacial Water under 3D Nanoscale Confinement

Capillary condensation of water from vapor is an everyday phenomenon which has a wide range of scientific and technological implications. Many aspects of capillary condensation are not well understood such as the structure of interfacial water, the existence of distinct properties of confined water, or the validity of the Kelvin equation at nanoscale. We note the absence of high-spatial resolution images inside a meniscus. Here, we develop an AFM-based method to provide in situ atomic-scale resolution maps of the solid-water interface of a nanomeniscus (80-250 nm³). The separation between the first two hydration layers on graphite is 0.30 nm, while on mica it is 0.28 nm. Those values are very close to the ones expected for the same surfaces immersed in bulk water. Thus, the hydration layer structure on a crystalline surface is independent of the water volume.

Dielectric Profile and Electromelting of a Monolayer of Water Confined in Graphene Slit Pore

A monolayer of water confined between two parallel graphene sheets exists in many different phases and exhibits fascinating dielectric properties that have been studied in experiments. In this work, we use molecular dynamics simulations to study how the dielectric properties of a confined monolayer of water is affected by its structure. We consider six of the popular nonpolarizable water models-SPC/E, SPC/Fw, TIP3P, TIP3P_M (modified), TIP4P-2005, and TIP4P-2005f-and find that the in-plane structure of the water molecules at ambient temperature and pressure is strongly dependent on the water model: all the 3-point water models considered here show square ice formation, whereas no such structural ordering is observed for the 4-point water models. This allows us to investigate the role of the in-plane structure of the water monolayer on its dielectric profile. Our simulations show an anomalous perpendicular dielectric constant compared to the bulk, and the models that do not exhibit ice formation show very different dielectric response along the channel width compared to models that exhibit square ice formation. We also demonstrate the occurrence of electromelting of the in-plane ordered water under the application of a perpendicular electric field and find that the critical field for electromelting strongly depends on the water model. Together, we have shown the dependence of confined water properties on the different water structures that it may take when sandwiched between bilayer graphene. These remarkable properties of confined water can be exploited in various nanofluidic devices, artificial ion channels, and molecular sieving.

How do the doping concentrations of N and B in graphene modify the water adsorption?

Understanding the interaction of water and graphene is crucial for various applications such as water purification, desalination, and electrocatalysis. Experimental and theoretical studies have already investigated water adsorption on N- and B-doped graphene. However, there are no reports available that elucidate the influences of the N and B doping content in graphene on the microscopic geometrical structure and the electronic properties of the adsorbed water. Thus, this work is devoted to solving this problem using self-consistent van der Waals density functional theory calculations. The N and B doping contents of 0.0, 3.1, 6.3, and 9.4% were considered. The results showed that the binding energy of water increases almost linearly as a function of doping content at all concentrations for N-doped graphene but below 6.3% for B-doped graphene. In the linear range, the binding energy increases by approximately 30 meV for each increment of the doping ratio. Analyses of the geometric and electronic structures explained the enhancement of the water-graphene interaction with the variation in doping percentage.

Associated molecular liquids at the graphene monolayer interface

We report molecular simulations of the interaction between a graphene sheet and different liquids such as water, ethanol, and ethylene glycol. We describe the structural arrangements at the graphene interface in terms of density profiles, number of hydrogen bonds (HBs), and local structuration in neighboring layers close to the surface. We establish the formation of a two-dimensional HB network in the layer closest to the graphene. We also calculate the interfacial tension of liquids with a graphene monolayer and its profile along the direction normal to the graphene to rationalize and quantify the strengthening of the intermolecular interactions in the liquid due to the presence of the surface.

Direct Measurement of Water-Assisted Ion Desorption and Solvation on Isolated Carbon Nanotubes

We have investigated the change in mean residence time of gaseous ions adsorbed on the surface of suspended carbon nanotube field-effect transistors (CNT-FETs) with and without native surface water layers that exists in atmospheric conditions. Devices were characterized electrically before and after dehydration by thermal, dry gas, and vacuum desiccation and in each scenario were found to have substantially higher mean ion residence times. It is proposed that water molecules native to the CNT surface in ambient conditions provide a reduction pathway for incoming gaseous ions, yielding hydronium ions (H₃O⁺). This is supported by the appearance of frequent clustered readsorption events in the presence of surface water, caused by the rapid hopping of H⁺ between the device surface and the lowest water layer, which are not present in data collected from desiccated devices. After desiccation of the device, a thermal trial was conducted to determine the adsorption energy of N₂⁺ ions on the CNT surface. This work has profound implications for our understanding of wetting in one-dimensional systems and the chemistry of ion chemisorption and solvation on the surfaces of materials in general.

Investigating the Applicability of Molecular Dynamics Simulation for Estimating the Wettability of Sandstone Hydrocarbon Formations

One of the techniques to increase oil recovery from hydrocarbon reservoirs is the injection of low salinity water. It is shown that the injection of low salinity water changes the wettability of the rock. However, there are argumentative debates concerning low salinity water effect on changing the wettability of the oil/brine/rock system in the oil reservoirs. In this regard, molecular dynamics simulation (MDS) as a tool to simulate the phenomena at the molecular level has been used for more than a decade. In this study, the Zisman plot (presented by KRUSS Company) was simulated through MDS, and then, contact angle experiments for n-decane interactions on the Bentheimer substrate in the presence of different concentrations of sodium ions were conducted. MDS was then used to simulate experiments and understand the wettability trend based on free-energy calculations. Hereafter, a new model was developed in this study to correlate free energies with contact angles. The developed model predicted the experimental results with high accuracy (R ² ∼ 0.98). A direct relation was observed between free energy and water contact angle. In contrast, an inverse relation was noticed between the ion concentration and the contact angle such that an increase in the ion concentration resulted in a decrease in the contact angle and vice versa. In other terms, increasing brine ionic concentrations in the presence of n-decane is linked to a decrease in free energies and an increase in the wetting state of a sandstone. The comparison between the developed model's predicted contact angles and experimental observations showed a maximum deviation of 14.32%, which is in satisfactory agreement to conclude that MDS can be used as a valuable and economical tool to understand the wettability alteration process.

Universal relation between the density and the viscosity of dispersions of nanoparticles and stabilized emulsions

The effective viscosity of nanoparticle dispersions has been investigated experimentally quite a lot and various behaviours have been observed. Many models have been proposed to predict the effective viscosity, but these are mainly empirical ones, correlations with a tuning parameter or based on fastidious molecular interactions simulations. In this work, we propose a new fully physics-based analytical expression for the effective viscosity implementing theories from extended thermodynamics, including nano-confinement effects, nanoparticle-fluid interactions, density effects, size effects and nanoparticle volume fraction. We validate this model against several different types of nanoparticle dispersions and emulsions and explain the different behaviours using the same model. It appears that the density ratio of the nanoparticles with respect to the fluid plays a crucial role affecting the viscosity. The nanoparticle-fluid interactions become increasingly important for smaller nanoparticle sizes. From these comparisons, we arrive at a general simplified expression for the effective viscosity of nanoparticle dispersions, where it is observed that there is a direct universal relation between the nanoparticles and fluid densities and the nanodispersion viscosities. The validity of such a relation has been explicitly demonstrated.

Correlation between mobility and the hydrogen bonding network of water at an electrified-graphite electrode using molecular dynamics simulation

Mobility and hydrogen bonding network of water at a graphite electrode: effects of dissolved ions and applied potential.

Interfacial Polymerization of Cellulose Nanocrystal Polyamide Janus Nanocomposites with Controlled Architectures

The widespread use of renewable nanomaterials has been limited due to poor integration with conventional polymer matrices. Often, chemical and physical surface modifications are implemented to improve compatibility, however, this comes with environmental and economic cost. This work demonstrates that renewable nanomaterials, specifically cellulose nanocrystals (CNCs), can be utilized in their unmodified state and presents a simple and versatile, one-step method to produce polyamide/CNC nanocomposites with unique Janus-like properties. Nanocomposites in the form of films, fibers, and capsules are prepared by dispersing as-prepared CNCs in the aqueous phase prior to the interfacial polymerization of aromatic diamines and acyl chlorides. The diamines in the aqueous phase not only serve as a monomer for polymerization, but additionally, adsorb to and promote the incorporation of CNCs into the nanocomposite. Regardless of the architecture, CNCs are only present along the surface facing the aqueous phase, resulting in materials with unique, Janus-like wetting behavior and potential applications in filtration, separations, drug delivery, and advanced fibers.

Key Role of Transfer Layer in Load Dependence of Friction on Hydrogenated Diamond-Like Carbon Films in Humid Air and Vacuum

The friction of hydrogenated diamond-like carbon (H-DLC) films was evaluated under the controlled environments of humid air and vacuum by varying the applied load. In humid air, there is a threshold applied load below which no obvious friction drop occurs and above which the friction decreases to a relatively low level following the running-in process. By contrast, superlubricity can be realized at low applied loads but easily fails at high applied loads under vacuum conditions. Further analysis indicates that the graphitization of the sliding H-DLC surface has a negligible contribution to the sharp drop of friction during the running-in process under both humid air and vacuum conditions. The low friction in humid air and the superlow friction in vacuum are mainly attributed to the formation and stability of the transfer layer on the counterface, which depend on the load and surrounding environment. These results can help us understand the low-friction mechanism of H-DLC film and define optimized working conditions in practical applications, in which the transfer layer can be maintained for a long time under low applied load conditions in vacuum, whereas a high load can benefit the formation of the transfer layer in humid air.

Calculation of the interfacial tension of the graphene-water interaction by molecular simulations

We report the calculation of the solid-liquid interface tension of the graphene-water interaction by using molecular simulations. Local profiles of the interfacial tension are given through the mechanical and thermodynamic definitions. The dependence of the interfacial tension on the graphene area is investigated by applying both reaction field and Ewald summation techniques. The structure of the interfacial region close to the graphene sheet is analyzed through the profiles of the density and hydrogen bond number and the orientation of the water molecules. We complete this study by plotting the profiles of the components of the pressure tensor calculated by the Ewald summation and reaction field methods. We also investigate the case of a reaction field version consisting in applying a damped shifted force in the case of the calculation of the pressure components.

Understanding the effect of nanoconfinement on the structure of water hydrogen bond networks

Dynamic hydrogen bond trails in water confined between two phospholipid membranes traced by the information flow model.

Study of distance dependence of hydrophobic force between two graphene-like walls and a signature of pressure induced structure formation in the confined water

We examine the separation distance dependence of the hydrophobic force by systematically varying the distance (d) between two walls. The hydrophobic force exhibits a distance mediated crossover from a liquid-like to a gas-like behavior at around d ∼ 12 Å for 1 atm pressure. The distance dependence can be fitted to a bi-exponential form, with the longer distance part displaying a correlation length of 20 Å. In addition, the crossover is found to be accompanied by a divergent-like growth of the local relative number fluctuation of the water molecules confined between the two surfaces. Furthermore, at a fixed separation (d = 20 Å), we observe a pressure induced structural modification of confined water at high pressure. The confined water is found to form an ordered structure at high pressure (10 000 atm) and room temperature, in agreement with the experimental study [G. Algara-Siller et al. Nature 519(7544), 443 (2015)].

Streams, cascades, and pools: various water cluster motifs in structurally similar Ni(ii) complexes

Hydrogen bonding (HB) interactions are well known to impact the properties of water in the bulk and within hydrated materials.

Charge Induced Dynamics of Water in a Graphene-Mica Slit Pore

We use atomic force microscopy to in situ investigate the dynamic behavior of confined water at the interface between graphene and mica. The graphene is either uncharged, negatively charged, or positively charged. At high humidity, a third water layer will intercalate between graphene and mica. When graphene is negatively charged, the interface fills faster with a complete three layer water film, compared to uncharged graphene. As charged positively, the third water layer dewets the interface, either by evaporation into the ambient or by the formation of three-dimensional droplets under the graphene, on top of the bilayer. Our experimental findings reveal novel phenomena of water at the nanoscale, which are interesting from a fundamental point of view and demonstrate the direct control over the wetting properties of the graphene/water interface.

Interaction between a water drop and holey graphene: retarded imbibition and generation of novel water–graphene wetting states

Water nanodrop imbibition in holey graphene is studied unraveling novel fiber-like wetting state that enhances water–accessible graphene surface area.