Moving beyond the Solvent-Tip Approximation to Determine Site-Specific Variations of Interfacial Water Structure through 3D Force Microscopy
21 Jan 2021-Journal of Physical Chemistry C (American Chemical Society)-Vol. 125, Iss: 2, pp 1282-1291
TL;DR: Although interfacial solution structure impacts environmental, biological, and technological phenomena, including colloidal stability, protein assembly, heterogeneous nucleation, and water desalina as discussed by the authors, it has not been studied in the literature.
Abstract: Although interfacial solution structure impacts environmental, biological, and technological phenomena, including colloidal stability, protein assembly, heterogeneous nucleation, and water desalina...
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TL;DR: In this paper, the atomic-scale structure of interfacial water on hydrophilic and hydrophobic surfaces was probed using 3D-AFM imaging, and it was shown that hydration layers are formed on both hydrophoric and non-hydrophilic surfaces.
Abstract: Hydration layers are formed on hydrophilic crystalline surfaces immersed in water. Their existence has also been predicted for hydrophobic surfaces, yet the experimental evidence is controversial. Using 3D-AFM imaging, we probed the interfacial water structure of hydrophobic and hydrophilic surfaces with atomic-scale spatial resolution. We demonstrate that the atomic-scale structure of interfacial water on crystalline surfaces presents two antagonistic arrangements. On mica, a common hydrophilic crystalline surface, the interface is characterized by the formation of 2 to 3 hydration layers separated by approximately 0.3 nm. On hydrophobic surfaces such as graphite or hexagonal boron nitride (h-BN), the interface is characterized by the formation of 2 to 4 layers separated by about 0.5 nm. The latter interlayer distance indicates that water molecules are expelled from the vicinity of the surface and replaced by hydrocarbon molecules. This creates a new 1.5–2 nm thick interface between the hydrophobic surface and the bulk water. Molecular dynamics simulations reproduced the experimental data and confirmed the above interfacial water structures.
30 citations
TL;DR: In this paper, the authors discuss the role of peptides and proteins involved in the crystallization process of living organisms, ranging from biomineralization in living organisms to various materials in our lives.
Abstract: Crystallization defines what the world is all about, ranging from biomineralization in living organisms to various materials in our lives. During these processes, peptides and proteins involved in ...
14 citations
TL;DR: In this paper, second harmonic generation amplitude and phase measurements are acquired in real time from fused silica: water interfaces that are subjected to ionic strength transitions conducted at pH 5.8.
Abstract: Second harmonic generation amplitude and phase measurements are acquired in real time from fused silica:water interfaces that are subjected to ionic strength transitions conducted at pH 5.8. In conjunction with atomistic modeling, we identify correlations between structure in the Stern layer, encoded in the total second-order nonlinear susceptibility, chi(2)tot, and in the diffuse layer, encoded in the product of chi(2)tot and the total interfacial potential, phi(0)tot. chi(2)tot:phi(0)tot correlation plots indicate that the dynamics in the Stern and diffuse layers are decoupled from one another under some conditions (large change in ionic strength), while they change in lockstep under others (smaller change in ionic strength) as the ionic strength in the aqueous bulk solution varies. The quantitative structural and electrostatic information obtained also informs on the molecular origin of hysteresis in ionic strength cycling over fused silica. Atomistic simulations suggest a prominent role of contact ion pairs (as opposed to solvent-separated ion pairs) in the Stern layer. Those simulations also indicate that net water alignment is limited to the first 2 nm from the interface, even at 0 M ionic strength, highlighting water's polarization as an important contributor to nonlinear optical signal generation.
13 citations
TL;DR: In this article , the individual Stern layer and diffuse layer OH stretching spectra at the silica/water interface in the presence of NaCl over a wide pH range using a combination of vibrational sum frequency generation spectroscopy, heterodyned second harmonic generation, and streaming potential measurements.
Abstract: The electric double layer governs the processes of all charged surfaces in aqueous solutions; however, elucidating the structure of the water molecules is challenging for even the most advanced spectroscopic techniques. Here, we present the individual Stern layer and diffuse layer OH stretching spectra at the silica/water interface in the presence of NaCl over a wide pH range using a combination of vibrational sum frequency generation spectroscopy, heterodyned second harmonic generation, and streaming potential measurements. We find that the Stern layer water molecules and diffuse layer water molecules respond differently to pH changes: unlike the diffuse layer, whose water molecules remain net-oriented in one direction, water molecules in the Stern layer flip their net orientation as the solution pH is reduced from basic to acidic. We obtain an experimental estimate of the non-Gouy-Chapman (Stern) potential contribution to the total potential drop across the insulator/electrolyte interface and discuss it in the context of dipolar, quadrupolar, and higher order potential contributions that vary with the observed changes in the net orientation of water in the Stern layer. Our findings show that a purely Gouy-Chapman (Stern) view is insufficient to accurately describe the electrical double layer of aqueous interfaces.
12 citations
TL;DR: In this paper , atomic force microscopy (AFM) images were combined with molecular dynamics simulations to reveal the molecular details of chitin chain arrangements at the surfaces of individual chitIN nanocrystal (chitin NC) surfaces.
Abstract: Chitin is one of the most abundant and renewable natural biopolymers. It exists in the form of crystalline microfibrils and is the basic structural building block of many biological materials. Its surface crystalline structure is yet to be reported at the molecular level. Herein, atomic force microscopy (AFM) in combination with molecular dynamics simulations reveals the molecular‐scale structural details of the chitin nanocrystal (chitin NC)–water interface. High‐resolution AFM images reveal the molecular details of chitin chain arrangements at the surfaces of individual chitin NCs, showing highly ordered, stable crystalline structures almost free of structural defects or disorder. 3D‐AFM measurements with submolecular spatial resolution demonstrate that chitin NC surfaces interact strongly with interfacial water molecules creating stable, well‐ordered hydration layers. Inhomogeneous encapsulation of the underlying chitin substrate by these hydration layers reflects the chitin NCs’ multifaceted surface character with different chain arrangements and molecular packing. These findings provide important insights into chitin NC structures at the molecular level, which is critical for developing the properties of chitin‐based nanomaterials. Furthermore, these results will contribute to a better understanding of the chemical and enzymatic hydrolysis of chitin and other native polysaccharides, which is also essential for the enzymatic conversion of biomass.
8 citations
References
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TL;DR: A highly concentrated aqueous electrolyte whose window was expanded to ~3.0 volts with the formation of an electrode-electrolyte interphase, which could potentially be replaced with a safer aQueous alternative to lithium-ion batteries.
Abstract: Lithium-ion batteries raise safety, environmental, and cost concerns, which mostly arise from their nonaqueous electrolytes. The use of aqueous alternatives is limited by their narrow electrochemical stability window (1.23 volts), which sets an intrinsic limit on the practical voltage and energy output. We report a highly concentrated aqueous electrolyte whose window was expanded to ~3.0 volts with the formation of an electrode-electrolyte interphase. A full lithium-ion battery of 2.3 volts using such an aqueous electrolyte was demonstrated to cycle up to 1000 times, with nearly 100% coulombic efficiency at both low (0.15 C) and high (4.5 C) discharge and charge rates.
2,229 citations
TL;DR: In this article, a general force field, CLAYFF, was developed for the simulation of hydrated and multicomponent mineral systems and their interfaces with aqueous solutions, and the potentials were derived from parametrizations incorporating structural and spectroscopic data for a variety of simple hydrated compounds.
Abstract: The fate of chemical and radioactive wastes in the environment is related to the ability of natural phases to attenuate and immobilize contaminants through chemical sorption and precipitation processes. Our understanding of these complex processes at the atomic level is provided by a few experimental and analytical methods such as X-ray absorption and NMR spectroscopies. However, due to complexities in the structure and composition of clay and other hydrated minerals, and the inherent uncertainties of the experimental methods, it is important to apply theoretical molecular models for a fundamental atomic-level understanding, interpretation, and prediction of these phenomena. In this effort, we have developed a general force field, CLAYFF, suitable for the simulation of hydrated and multicomponent mineral systems and their interfaces with aqueous solutions. Interatomic potentials were derived from parametrizations incorporating structural and spectroscopic data for a variety of simple hydrated compounds. A...
2,163 citations
TL;DR: When a liquid is confined in a narrow gap, the effective shear viscosity is enhanced compared to the bulk, relaxation times are prolonged, and nonlinear responses set in at lower shear rates.
Abstract: When a liquid is confined in a narrow gap (as near a cell membrane, in a lubricated contact between solids, or in a porous medium), new dynamic behavior emerges. The effective shear viscosity is enhanced compared to the bulk, relaxation times are prolonged, and nonlinear responses set in at lower shear rates. These effects are more prominent, the thinner the liquid film. They appear to be the manifestation of collective motions. The flow of liquids under extreme confinement cannot be understood simply by intuitive extrapolation of bulk properties. Practical consequences are possible in areas from tribology and materials processing to membrane physics.
836 citations
TL;DR: The treatment given here offers wide flexibility in dealing with cell surfaces in the languages of the cell physiologist, biochemist and physical chemist.
635 citations
TL;DR: The short-range hydration force between two molecularly smooth surfaces of mica containing hydrated potassium ions is measured and is found to be overall repulsive but not monotonic at separations, rationalize apparently irreconcilable observations on clay–water systems and go some way towards clarifying the origin and nature of hydration forces.
Abstract: The short-range forces between hydrophilic surfaces in water determine the behaviour of many diverse systems such as the stability of colloidal dispersions1,2 and soap films3, the swelling of clays4 and the interactions of biological membranes5–8 and macromolecules9. So far, all experimental measurements of these forces have indicated that they are repulsive and decay monotonically with distance out to separations of up to ∼6 nm. These forces, variously termed ‘structural’ or ‘hydration’ forces, arise from the energy needed to dehydrate interacting surfaces which contain ionic or polar species. Here we have measured, in some detail, the short-range hydration force between two molecularly smooth surfaces of mica containing hydrated potassium ions. We find that while the hydration force is overall repulsive it is not monotonic at separations ≲1.5 nm but exhibits oscillations, that is, alternating maxima and minima with a mean periodicity of 0.25 ± 0.03 nm, roughly the diameter of the water molecule. These results rationalize apparently irreconcilable observations on clay–water systems and go some way towards clarifying the origin and nature of hydration forces.
634 citations