Behavior Of Interfacial Water Research Articles

(Invited) Cations at a Solid-Liquid Interface: A Second Harmonic Generation Investigation

When an electrode contacts an electrolyte, an interfacial electric field forms. This interfacial field can polarize the electrode’s surface and nearby molecules, but its effect can be reversed by applying external potential. One method for quantifying this effect is the phase-sensitive second harmonic generation (PS-SHG) technique. We present our PS-SHG investigation of the Pt/water interface, where we examine the impact of the electrolyte chemistry on the electrical double layer (EDL). We will discuss how switching cations in alkaline electrolytes can affect the solid-liquid interface, in particular, the behavior of interfacial water. Our work provides a tool for quantifying the interfacial electric field at an electrode-electrolyte interface and shows the possibility of how cations can modify the EDL.

Direct observation of anomalous water at the solid-liquid boundary on silica surface

In this study, we investigate the properties and behavior of interfacial water on solid silica surfaces and its implications for various applications. We utilize a combination of transmission electron microscopy (TEM), nuclear magnetic resonance, mass spectrometry, infrared, and Raman spectroscopy to explore the presence and characteristics of anomalous water on silica surfaces. Our findings reveal a stable, nanoscale layer of wall-bound water on the inner surface of silica tubes that persists under high vacuum and room temperature conditions. This layer is rich in hydrated hydrogen ions and exhibits a thickness that correlates with the density of hydroxyl groups in silica. Through additional experimentation, we demonstrate that reducing the density of silica hydroxyl groups causes the wall-bound water to return to a liquid state, highlighting the pivotal role of hydroxyl groups in the formation of this unique water layer. Our study offers valuable insights into the properties and behavior of interfacial water on solid surfaces and lays the foundation for potential applications in a wide range of fields, such as energy storage, drug delivery, environmental remediation, biological sample preparation, microfluidics, and nanofluidics. Future research will further explore the properties and behavior of interfacial water on different material surfaces and under various environmental conditions, laying the groundwork for technological innovation in related fields. By utilizing advanced approaches and fostering interdisciplinary collaboration, this research contributes significantly to our understanding of interfacial water and paves the way for the development of cutting-edge technologies that capitalize on its distinctive properties.

Revealing the Behavior of Interfacial Water in Te-Doped Bi via Operando Infrared Spectroscopy for Improving Electrochemical CO2 Reduction

Revealing the Behavior of Interfacial Water in Te-Doped Bi via Operando Infrared Spectroscopy for Improving Electrochemical CO₂ Reduction

Evidence for Entropically Controlled Interfacial Hydration in Mesoporous Organosilicas.

At aqueous interfaces, the distribution and dynamics of adsorbates are modulated by the behavior of interfacial water. Hydration of a hydrophobic surface can store entropy via the ordering of interfacial water, which contributes to the Gibbs energy of solute binding. However, there is little experimental evidence for the existence of such entropic reservoirs, and virtually no precedent for their rational design in systems involving extended interfaces. In this study, two series of mesoporous silicas were modified in distinct ways: (1) progressively deeper thermal dehydroxylation, via condensation of surface silanols, and (2) increasing incorporation of nonpolar organic linkers into the silica framework. Both approaches result in decreasing average surface polarity, manifested in a blue-shift in the fluorescence of an adsorbed dye. For the inorganic silicas, hydrogen-bonding of water becomes less extensive as the number of surface silanols decreases. Overhauser dynamic nuclear polarization (ODNP) relaxometry indicates enhanced surface water diffusivity, reflecting a loss of enthalpic hydration. In contrast, organosilicas show a monotonic decrease in surface water diffusivity with decreasing polarity, reflecting enhanced hydrophobic hydration. Molecular dynamics simulations predict increased tetrahedrality of interfacial water for the organosilicas, implying increased ordering near the nm-size organic domains (relative to inorganic silicas, which necessarily lack such domains). These findings validate the prediction that hydrophobic hydration at interfaces is controlled by the microscopic length scale of the hydrophobic regions. They further suggest that the hydration thermodynamics of structurally heterogeneous silica surfaces can be tuned to promote adsorption, which in turn tunes the selectivity in catalytic reactions.

Water at Interfaces: Its Behavior and Roles in Interfacial Phenomena

Water at interfaces plays essential roles in many natural phenomena and engineering applications. However, the molecular behavior of interfacial water is still a matter of intense debate. Thus far, many experimental and theoretical methods have been employed to elucidate the real picture (structure, dynamics, hydrogen bonding states, etc.) of interfacial water and its relevance to interfacial phenomena and material functions. The author reviews these works and discusses the principles and limitations of the analytical methods. The significant representative findings on water-mediated interfacial phenomena are also introduced.

Recent advances in probing two-dimensional materials confined water by scanning probe microscopy

<p indent=0mm>Interfacial water is ubiquitous in nature and industry, which plays a crucial role in areas such as wetting, corrosion, lubrication and electrochemistry. The structure and dynamic behavior of interfacial water have been proven to be different from those of bulk water. Therefore, to deeply understand the unique properties of interfacial water, structural imaging with atomic resolution is of great importance. Up to now, owing to its high temporal and spatial resolution, scanning probe microscopy (SPM) has been extensively applied to investigate water molecules at solid interfaces. However, most of those SPM investigations are conducted at cryogenic temperature or under ultra-high vacuum, as under ambient conditions the capillary force between SPM tip and water molecules will perturb the structures of interfacial water on solid surface. Thanks to the two-dimensional (2D) materials which can be utilized as ultra-thin coatings owing to its atomic thickness, good flexibility, impermeability and chemical stability. The graphene coating could protect and fix the structures of interfacial water, which enables the structural imaging by SPM. The 2D material confined water expands the scope of SPM research on interfacial water, promoting the development of interface science. The structure and dynamics of 2D material confined water can be influenced by the structure and hydrophilicity of the interface materials, as well as environment factors such as humidity, temperature and pressure. In recent years, a great deal of works have been conducted with SPM to explore the properties of 2D material confined water and remarkable research results have been achieved. In this review, we will introduce recent progress in probing 2D materials confined water by SPM under ambient conditions, including detecting the microscopic structures of 2D confined water, probing the dynamic behaviors of 2D confined water as well as nanomanipulation of 2D confined water. Furthermore, the effects of confined water on the optical, electrical and frictional properties of the 2D material coatings are also discussed. Finally, a perspective on the directions of future SPM studies of 2D material confined water and the challenges faced by this field are presented. We hope that this review will inspire interest in 2D confined water and provide some new ideas for researchers in this field.

Insights on the Structural and Dynamic Properties of Corundum–Water Interfaces from First-Principle Molecular Dynamics

The interaction of water with hydroxylated mineral surfaces is central to numerous natural and technological processes; yet, at the atomic level much remains to be understood about the structure and dynamics of interfacial water and H-bonding networks. This work applies first-principle molecular dynamics to examine the relationship between surface structure and interfacial water behavior at four hydroxylated corundum (α-Al2O3) surfaces. The four surfaces studied include the (001), (012), (110), and (113) surfaces; they have distinct surface functional groups (−OH, μ-OH, and μ3-OH) and topography (planar, corrugated, and two-tiered). Interfacial H-bonding was investigated in detail by analyzing atomic density 1-D profiles, angular distribution of surface O–H bonds, and the dipole moment orientation of interface H2O molecules and by calculating vibrational density of states in the high-frequency region. Our results reveal distinct differences in the interaction of interfacial water and H-bonding networks at the four surfaces. Specifically, inter- and intramolecular H-bonding depends on surface site coordination geometry, neighboring functional groups, and surface topography. Moreover, intramolecular H-bonding involving in-plane surface hydroxyl groups may persist, thus limiting intermolecular H-bonding. Equally, first solvation layer water molecules are preferentially orientated at the (001), (012), and (113) surfaces, whereas water molecules at the (110) surface show minimal preferred orientation. The distinct differences in the behavior of interfacial water and H-bonding at the four surfaces may play a substantial role in determining the reactivity of the surfaces toward processes such as ion adsorption–desorption and dissolution–precipitation.

Femtosecond Laser Microfabrication of Porous Superwetting Materials for Oil/Water Separation: A Mini-Review.

Frequent oil-leakage accidents and large quantities of oil-bearing wastewater discharge cause severe environmental pollution and huge economic losses. Recently, superwetting porous materials are successfully utilized to separate oil/water mixture (OWM) based on the different interfacial behavior of water and oil. Here, we summarize the recent development of efficient oil/water separation (OWS) based on the femtosecond laser-induced superwetting materials. The typical wettability-based separation manners (including “oil-removing” and “water-removing”) and the characteristic of the femtosecond laser are introduced as background. Various laser-structured porous sheets with either superhydrophobicity or underwater superoleophobicity are successfully used to separate different OWMs. The laser processing methods, surface wettability, separation process, and separation mechanism of these laser-structured separation materials are reviewed. Finally, the current challenges and prospects in achieving OWS by femtosecond laser microfabrication are discussed.

Dynamic behaviors of interfacial water on the self-assembly monolayer (SAM) heterogeneous surface.

Dynamic behaviors of water molecules near the surface with mixed hydrophobic and hydrophilic areas are studied by molecular dynamics simulation. More specifically, the diffusion coefficient and hydrogen bond lifetime of interfacial water on the self-assembly monolayer composed of hydrophobic and hydrophilic groups and their dependence on the mixing ratio are studied. The diffusion dramatically slows down, and the hydrogen bond lifetime considerably increases when a few hydrophilic groups are added to the hydrophobic surface. When the percentage of hydrophilic groups increases to 25%, the behavior of interfacial water is similar to the case of the pure hydrophilic surface. The sensitivity to the hydrophilic group can be attributed to the fact that the grafted hydrophilic groups can not only retard the directly bound water molecules but also affect indirectly bound water by stabilizing hydrogen bonds among interfacial water molecules.

Concentration‐Driven Disruption of Single‐File Water

AbstractStrong hydrogen bonding is known to entail some of the spectacular physical properties of liquid water, including fast diffusion under nanoconfinement. Similar to biological channels, the single‐file or collective motion of interconnected water molecules has been observed in nanotubes and laminar structures, exhibiting tremendous potential for energy‐efficient separation applications. Desalination, breaking azeotropes, and dehumidification have been all addressed with the membranes enabling selective transport of water while most attention has been paid to the fabrication and morphological characteristics of the respective microporous materials. However, the performance of membrane processes also depends on the properties of the chemical systems to be treated, often facing problems under realistic conditions such as concentration polarization. In this study, adsorption controlled permeation is employed to explore the interfacial behavior of water–alcohol mixtures in nanostructured membranes as a function of concentration. The permeation rate of water is found to sink manifold as the molar fraction of isopropanol molecules increases, indicating breakdown of the single‐file mechanism. A phenomenological model is devised to account for intermolecular interactions in the binary liquid–liquid mixture whereas kinetic simulations agree well with the experimental data. The results point to the fundamental limitations of water‐selective conduits for dehydrating organic solvents.

In English

The aim of this study was to analyze the temperature and interfacial behavior of water bound to A-300, A-300/AM1 and Al 2 O 3 /AM1 initial and mechanically treated and located in air, chloroform alone or with addition of trifluoroacetic acid (TFAA) using low-temperature 1 H NMR spectroscopy and cryoporometry. Properties of unmodified (A-300) and modified (AM1) (1 : 1) nanosilicas, as well as nanoalumina, were studied in air or chloroform alone or with addition of TFAA using 1 H NMR spectra recorded at different temperatures and related cryoporometry. In nontreated composite, water interaction with nanosilica (hydration degree h = 1.125 g/g) increases and free surface energy g S grows by five times due to water reorganization into nanoclusters and similar clusters are absent in cA-300 due to several factors. After the mechanical treatment (bulk density increases to r b » 1.2 g/cm 3 ), water interaction energy with nanosilicas becomes smaller (by three times for CDCl 3 and ten times for air medium) than that for nontreated composite. The effects of CDCl 3 are much stronger for water in nontreated system than those in compacted composite. This is due to reorganization of water affected both by changes in the confined space effects and the influence of hydrophobic chloroform, which can displace water into small voids (inaccessible for larger chloroform molecules) or larger voids to reduce the contact area of both liquids. Thus, it has been shown that the observed influence of the hydrophobic components in complex hydrophobic/hydrophilic systems on enhancement of water binding to hydrophilic components is the general phenomenon caused by both the confined space effects and features of interactions of water with various hydrophobic structures such as the surface functionalities of hydrophobic silica and hydrophobic liquid (chloroform) or proton-donor components (TFAA).

Water near bioinert self-assembled monolayers

For a long time, water has been speculated to play an essential role in the interactions of proteins and cells with artificial biocompatible materials. The current question is how water molecules at the interfaces affect the adsorption of proteins and the adhesion of cells. To answer this question, we introduce recent works that investigated the interfacial behavior of water near self-assembled monolayers (SAMs) by different types of analytical techniques. By combining these findings, we discuss how interfacial water affects the protein and cell resistance of various bioinert SAMs. Recent works revealed that protein and cell resistance of bioinert self-assembled monolayers originates in the physical barrier of the interfacial water. We review the history of the previous works that attempted to clarify the underlying mechanism and discuss prospects to apply the findings to design new biomaterials.

Water Structure and Dynamics at Hematite Electrodes

Electrocatalysis at a transition metal oxide (TMO) electrode in aqueous electrolyte is controlled in part by the behavior of interfacial water. Atomically precise measurements of TMO-electrolyte interfaces under electrocatalytic working conditions are therefore prerequisite for developing accurate models of interfacial reactions. We present the most detailed measurements to date of electrolyte ordering at the reactive hematite (α-Fe2O3) (1-102) (r-cut) surface at open circuit conditions and under applied cathodic bias in 5 mM Na2SO­4 solution. Interface structures are measured in situ by synchrotron X-ray crystal truncation rod (CTR) scattering using a novel electrochemical mini-cell. CTR results are interpreted in light of first-principles molecular dynamics simulations. We find that the equilibrium structure of the r-cut hematite-electrolyte interface is defined by frequent exchange of water molecules between terminal aquo ligands and solution, resulting in a steady-state partial coverage of undercoordinated surface iron sites. Under cathodic bias, the surface is excessively protonated, strengthening the near-surface hydrogen-bonding network. The steady-state coverage of terminal aquo ligands subsequently increases, armoring the hematite electrode against reductive dissolution. The ordering and separation of water layers depend on the cathodic bias magnitude. Taken together, these results reveal the fine details of the interface structure which underlie the electrical double layer models used to describe macroscopic electrochemical measurements. The methods developed through this work open a new frontier for the in situ characterization of TMO-electrolyte interfaces during electrocatalytic reactions.

Effect of Cu2 + activation on interfacial water structure at the sphalerite surface as studied by molecular dynamics simulation

In the first part of this paper, an experimental contact angle study of fresh and Cu2+ activated sphalerite-ZnS surfaces as well as the covellite-CuS (001) surface is reported describing the increased hydrophobic character of the surface during Cu2+ activation. In addition to these experimental results, fresh sphalerite-ZnS (110), copper-zinc sulfide-CuZnS2 (110), villamaninite-CuS2 (100), and covellite-CuS (001) surfaces were examined using Molecular Dynamics Simulation (MDS). Our MDS results on the behavior of interfacial water at the fresh sphalerite-ZnS (110), copper-zinc sulfide-CuZnS2 (110), villamaninite-CuS2 (100), and covellite-CuS (001) surfaces include simulated contact angles, water number density distribution, water dipole orientation, water residence time, and hydrogen-bonding considerations. The copper content at the Cu2+ activated sphalerite surface seems to account for the increased hydrophobicity as revealed by both experimental and MD simulated contact angle measurements. The relatively greater hydrophobic character developed at the Cu2+ activated sphalerite surface and at the copper sulfide surfaces has been described by MDS, based on the structure of interfacial water and its dynamic properties.

Effect of surface oxidation on interfacial water structure at a pyrite (100) surface as studied by molecular dynamics simulation

In the first part of this paper, a SEM and contact angle study of a pyrite (100) surface is reported describing the relationship between surface oxidation and the hydrophilic surface state. In addition to these experimental results, the following simulated surface states were examined using molecular dynamics simulation (MDS): a fresh unoxidized (100) surface; polysulfide at the (100) surface; and elemental sulfur at the (100) surface. Crystal structures for the polysulfide and elemental sulfur at the (100) surface were simulated using density functional theory (DFT) quantum chemical calculations. The well known oxidation mechanism which involves formation of a metal deficient layer was also described with DFT. Our MDS results of the behavior of interfacial water at the fresh and oxidized pyrite (100) surfaces without/with the presence of ferric hydroxide include simulated contact angles, number density distribution for water, water dipole orientation, water residence time, and hydrogen-bonding considerations. The significance of the formation of ferric hydroxide islands in accounting for the corresponding hydrophilic surface state is revealed not only from experimental contact angle measurements but also from simulated contact angle measurements using MDS. The hydrophilic surface state developed at oxidized pyrite surfaces has been described by MDS, on which basis the surface state is explained, based on interfacial water structure.

単分子膜における生体不活性特性のメカニズム： 分子集積密度の界面水分子の振る舞いへの影響

単分子膜における生体不活性特性のメカニズム： 分子集積密度の界面水分子の振る舞いへの影響

Textural Characteristics of Resorcinol—Formaldehyde Resin and Temperature Behavior of Bound Water Affected by Co-Adsorbed Trifluoroacetic Acid or Pyridine in Weakly Polar Organic Media

Resorcinol-formaldehyde resin (RFR) was synthesized as a porous material characterized by specific surface area of 140 m2/g and pore volume of 0.59 cm3/g with major proportions of broad mesopores and macropores. The interfacial behavior of water at low (h = 0.05 g of water/gram of dry RFR) and high (h = 2 g/g) hydration degrees depends on temperature and pore size filled by unfrozen water because its freezing-point depression increases in narrower pores. When water is mixed with co-adsorbates, the effects of such co-adsorbates as non-polar, weakly polar and polar organics depend on the amounts and the pore sizes. Even at a low hydration degree (h = 0.05 g/g), a portion of water can be displaced from pores by organic co-adsorbates because water has a relatively weak interaction with the RFR surface.

Surface Strain Effects on the Water–Graphene Interfacial and Confinement Behavior

We studied via molecular dynamics the link between the strain-driven hydration free-energy changes in the association process involving finite-size graphene surfaces, the resulting water–graphene interfacial tension, and the combined effect of the surface strain and confinement on the thermodynamic response functions and the dynamics of confined water. We found that an in-plane biaxial tensile strain ε = 10% enhances significantly not only the water–graphene hydrophobicity with respect to that of the unstrained counterpart but also the confinement effect on the thermodynamic response functions and slowing down of the dynamics of water over those of the corresponding bulk counterpart. The interfacial behavior of water in contact with strained-graphene plates resembles that observed for “pp” corrugated-plate configuration, as reported earlier [Chialvo et al. J. Phys. Chem. C 2013, 117, 23875], exibiting a significant enhancement of the fluid–surface hydrophobicity and response functions relative to those of the unstrained surface. In contrast, the slowing down of the dynamics of the confined water does not show any differentiation with respect to the type of surface.

Interfacial phenomena at a surface of partially silylated nanosilica

Unmodified pyrogenic silica PS300 and partially silylated nanosilica samples at a degree of substitution of surface silanols by trimethylsilyl (TMS) groups ΘTMS=27.2% and 37.2% were studied to elucidate features of the interfacial behavior of water adsorbed alone, or co-adsorbed with methane, hydrogen, or trifluoroacetic acid (TFAA). In the aqueous suspension modified PS300 at ΘTMS=37.2% forms aggregates of 50–200nm in size and can bind significant amounts of water (up to ∼5g/g). Only 0.5g/g of this water is strongly bound, while the major fraction of water is weakly bound. The presence of surface TMS groups causes the appearance of weakly associated water (WAW) at the interfaces. The adsorption of methane and hydrogen onto TMS-nanosilica with pre-adsorbed water (hydration degree h=0.05 or 0.005g/g) increases with increasing temperature. In weakly polar CDCl3 medium, interfacial water exists in strongly (SAW, chemical shift δH=4–5ppm) and weakly (δH=1–2ppm) associated states, as well as strongly (changes in the Gibbs free energy −ΔG>0.5–0.8kJ/mol) and weakly (−ΔG<0.5–0.8kJ/mol) bound states. WAW does not dissolve TFAA but some fraction of SAW bound to TMS-nanosilica surface can dissolve TFAA.

Liquid–solid interfaces: structure and dynamics from spectroscopy and simulations

Liquid–solid interfaces: structure and dynamics from spectroscopy and simulations