Changes In Water Structure Research Articles

From Graphene Oxide to Graphene: Changes in Interfacial Water Structure and Reactivity Using Deep Neural Network Force Fields

From Graphene Oxide to Graphene: Changes in Interfacial Water Structure and Reactivity Using Deep Neural Network Force Fields

Insights into the dual effect of an amphiphilic additive on hydrate formation from a water structure perspective

Chemical additives play an important role in gas hydrate formation, which involves the transformation of water structure. However, the relationship between the effects of additives on water structure and hydrate formation is inconclusive, especially for amphiphilic molecules. Here, we investigate the changes in water structure caused by rhamnolipid (Rha) biosurfactants and the resulting effect on methane hydrate formation through kinetic experiments, morphological observation, and in situ Raman spectroscopy. The Gaussian peaks of strongly hydrogen-bonded and weakly hydrogen-bonded water are identified, of which the integrated intensity and position are compared. It is found that the dual effect of Rha on hydrate formation kinetics, namely nucleation inhibition and growth promotion, is attributed to the ordered arrangement of water molecules with stronger hydrogen bonding interactions induced by the charged head groups. The strongly hydrogen-bonded water inhibits nucleation but promotes growth. In addition, the adsorption of Rha on montmorillonite (MMT) eliminates the changes in water structure and the dual effect of hydrate formation kinetics, providing further evidence for the above conclusion. These insights pave the way for a deeper understanding of hydrate formation kinetics from a water structure perspective, as well as providing a scientific basis for the commercial application of surfactants.

Effects of hydrophilic groups of polymer on change in hydrogen-bonding structure of water in hydrogels during dehydration

To investigate the effects of polymer hydrophilicity on hydrogen-bonding structures of water in hydrogels, differential scanning calorimetry and X-ray diffraction measurements were performed. The results show that the amount of intermediate water in polyacrylamide (PAA) hydrogel is about 12% smaller than that in poly-N,N’-dimethylacrylamide (PDMAA) hydrogel. Furthermore, it was found that the bound water in PAA hydrogel primarily exists around the surface of the polymer bundles, whereas that in PDMAA hydrogel acts as a crosslinker between polymer chains. These results suggest that the polymer hydrophilicity is an important factor for dehydration and water absorption in hydrogels.

Water structures in tip-charged carbon nanotubes.

Carbon nanotubes (CNTs) have potential applications in separation membranes and nanofluidic devices. It is well known that the behavior of water molecules confined in CNTs is affected by surface functional groups and external electric fields, leading to structural changes. The understanding of these structural changes of water within various CNTs is crucial, particularly in the context of material separation. While there have been many investigations into the effects of individual specific functional groups, a comprehensive understanding of the effect of these functional groups and the electric fields they generate on water molecules remains elusive. In this study, we investigate the properties of water molecules in tip-charged CNTs of (8,8), (10,10), and (12,12) chiral vectors with positive charges at one tip and negative charges at the other tip. Abstraction of ionized functional groups as tip charges enables a comprehensive understanding that is independent of individual functional groups. The symmetrically arranged tip-charges spontaneously generate a strong and symmetric electric field in the CNTs. However, the strength and directionality of the electric field are non-uniform and complex. In the interiors of (8,8) and (10,10) tip-charged CNTs, helical and square structures, which have disturbances caused by the non-uniformity of the electric field, are observed. The properties of the water molecules differed significantly in the center of the CNTs and near positive and negative charges, despite the electric field symmetry. In (12,12) tip-charged CNTs with 12 charges, a local ring structure is observed in the vicinity of negative charges but not in the vicinity of positive charges. It is concluded that the water structures in tip-charged CNTs have different characteristics from those in plain CNTs under a uniform electric field.

Kappa-carrageenan and xylooligosaccharide effect on water mobility and structural changes in silver carp proteins during frozen storage.

The cryoprotective effect of xylooligosaccharide (XO) and kappa-carrageenan (KC) mixture on silver carp proteins in fluctuated frozen storage from 4 to -18 °C was analyzed. Positive control as a conventional cryoprotectant mixture of sucrose (4%) and sorbitol (4%), KC (3%) and XO/KC (3%) treatments were incorporated in silver carp surimi and myofibrillar proteins to analyze the water mobility and its influence on structural attributes. The temperature fluctuation significantly increased the structural alteration in samples with no treatments due to oxidative changes, protein denaturation and recrystallization. Meanwhile, the mixture of XO and KC (XO/KC 3%) significantly reduced the tertiary and secondary structural alterations by preventing the oxidative changes in α-helix and tryptophan (Trp) residues. Moreover, XO/KC (3%) inhibited water mobility, hindering the T22 relaxation time, as compared to the samples added with KC (3%) and the positive control. Interestingly, the XO/KC (3%) mixture significantly reduced the formation of extracellular spaces and recrystallization by restricting the partial dehydration of muscles and extracellular solution concentration. From the current results, it can be concluded that the XO/KC mixture could be efficient in protecting aquatic food proteins during fluctuating frozen storage by preventing the exposure of Trp residues and α-helix contents. Moreover, XO/KC restricted the water mobility by establishing a bond and making water unavailable for crystallization and recrystallization. Therefore, XO/KC could be used as an effective mixture to prevent fluctuated and frozen storage changes in aquatic foods. © 2024 Society of Chemical Industry.

Using Methods to Assess the Structure of Water and Water-Containing Systems to Improve the Properties of Living and Non-Living Systems

This paper explores how water and water-based systems change their structure under different conditions, such as pH, temperature, and electric fields. These changes affect the properties and performance of living and non-living systems that use water or water-based systems in various technologies. We can use pH, temperature, and electric fields to measure and control the structural changes in water and water-based systems and improve the outcomes of different technologies in biology and medicine. More research is needed to understand how various factors influence the structure of water and water-based systems and how this affects living and non-living systems.

Competition between indigo carmine and water in the formation of dynamics behavior at different temperatures

We apply molecular dynamics methods to determine the impact of temperature on the structural and dynamic properties of aqueous solution of indigo carmine at temperatures between 300 and 323 К. We report that indigo carmine motion changes from the sub-diffuse to the diffuse regime at t = 100 ps, while water molecules continue to move in the slowed sub-diffuse regime. We demonstrate that the determining factor in the change of the structural and dynamic properties of the aqueous solution of indigo carmine at temperatures between 300 and 323 K is the change in the local structure of water and that the presence of indigo carmine leads to the decrease in temperatures at which a slowed motion of solution components is observed.

Long-term changes in water quality and structure of benthic animal communities in the Neva estuary under anthropogenic stress

In the Neva River estuary, 188 species and taxa of a higher rank of benthic animals were found, of which 129 were found in the eastern part of the Gulf of Finland. At present, the zoobenthos of the estuary is dominated by eurybiont species inhabiting polluted waters. We used integrated index IP' specially devised for water-bodies and rivers of the north-western Russia to assess the water quality and a state of ecosystems of the Neva estuary. It is based on structural parameters of zoobenthic communities and makes it possible to take into consideration the pollution by toxic and organic substances. On average the water quality of the Neva Bay assessed from IP′ values was relatively stable during 1994–2021. It was assessed as “polluted” with the exception of 2006 and 2015 caused by large-scale dredging works. In the period 1982–2021, the average number of zoobenthos species at one station in the Neva Bay almost doubled, from 12 ± 1 species in 1982 to 23±2 species in 2020. In the resort area of the eastern Gulf of Finland, the values of species richness and the Shannon index were much lower than in the Neva Bay, and on average for one station varied from 5±0.6 to 14±4 species and from 1.1±0.2 to 2.3±0.2 bit/ind. This is caused by the influence of salinity, eutrophication and pollution, and invasion of alien species. In addition to intense anthropogenic impact, the dynamics of the state of zoobenthos in this part of the estuary was determined by climate fluctuations.

The Microstructural Investigation and the Temperature-Changing Separation of Brine with a High Mg/Li Ratio

The difficult separation of magnesium–lithium has always been a problem that impedes the comprehensive utilization of salt lake brine resources. In this paper, a method for the separation of magnesium and lithium based on the crystallization of magnesium sulfate at high-temperature supersaturation and a low viscosity was investigated. The microstructure of soluble solutions was analyzed, and the results showed that, in a single-salt solution, controlling the temperature can change the contact ion pair structure of MgSO4 solution, and the arrangement of SO42− and H2O in the second hydration layer changes. In the Li2SO4 solution, the hydrogen bonds between SO42− and H2O break, and the surrounding water structure changes, breaking the similarity of the microstructure of magnesium–lithium and enhancing the separation effect. In a multi-ion system, the change in water structure in the solution decreases with the increase in Cl− concentration. Controlling the temperature of salt lake brine with different magnesium–lithium mass ratios, it was found that the magnesium–lithium mass ratio in the brine could be reduced by one-third; when the magnesium–lithium mass ratio was 10:1~160:1, the loss of lithium could be controlled within 5%, but when the magnesium–lithium mass ratio was 5:1, the loss of lithium was 25.06%. The main reason for lithium loss is that Li2SO4 in the liquid phase enters the solid phase as a cluster and is entrapped during the MgSO4 crystallization process. The entire experiment shows that controlling the temperature process is more suitable for salt lake brine with a high magnesium–lithium ratio.

Surface chemistry, water adsorption/desorption, and electrostatic charging behavior of display glass panel: Effect of rinsing solution pH

This study explored the effects of rinsing solutions on the surface energy and elemental composition of Corning's EAGLE-XG® display glass, as well as its water adsorption/desorption behaviors and their impact on surface charging/discharging behaviors. The study employed aqueous solutions with different pHs to immerse the glass samples for 1 min and then characterized them immediately after quick drying using various spectroscopic techniques. The results show that the surface-free energy and overall elemental composition of the glass surfaces were insensitive to the exposure to different pH values. However, the O/(Si + Al) ratio of the glass network exposed at the topmost surface was altered, and the water structure and desorption rate also varied among the samples rinsed with different pH solutions. Interestingly, it was found that the DI water treated surface appeared to discharge more slowly than the pH 1 or pH 13 solution treated surfaces, which correlated with the temporal change of water structure. Overall, this study provides important insights into the fundamental questions regarding the impact of the rinsing process on display glass panel surfaces and what characterization techniques are sensitive to the chemistry change in the topmost layer, which will facilitate future research and development efforts.

Interfacial molecular structure of phosphazene-based polymer electrolyte at the air-aqueous interface using sum frequency generation vibrational spectroscopy

The change induced in the physicochemical properties of polymer while hosting ions provides a platform for studying its potential applications in electrochemical devices, water treatment plants, and materials engineering science. The ability to host ions is limited in very few polymers, which lack a detailed molecular-level understanding for showcasing the polymer-ion linkage behavior at the interfacial region. In the present manuscript, we have employed sum frequency generation (SFG) vibrational spectroscopy to investigate the interfacial structure of a new class phosphazene-based methoxyethoxyethoxyphosphazene (MEEP) polymer in the presence of lithium chloride salt at the air-aqueous interface. The interfacial aspects of the molecular system collected through SFG spectral signatures reveal enhanced water ordering and relative hydrogen bonding strength at the air-aqueous interface. The careful observation of the study finds a synchronous contribution of van der Waals and electrostatic forces in facilitating changes in the interfacial water structure that are susceptible to MEEP concentration in the presence of ions. The observation indicates that dilute MEEP concentrations support the role of electrostatic interaction, leading to an ordered water structure in proximity to diffused ions at the interfacial region. Conversely, higher MEEP concentrations promote the dominance of van der Waals interactions at the air-aqueous interface. Our study highlights the establishment of polymer electrolyte (PE) characteristics mediated by intermolecular interactions, as observed through the spectral signatures witnessed at the air-aqueous interface. The investigation illustrates the polymer-ion linkage adsorption effects at the interfacial region, which explains the macroscopic changes observed from the cyclic voltammetry studies. The fundamental findings from our studies can be helpful in the design and fine-tuning of better PE systems that can offer improved hydrophobic membranes and interface stability for use in electrochemical-based power sources.

How Does pH Affect the Adsorption of Human Serum Protein in the Presence of Hydrophobic and Hydrophilic Nanoparticles at Air-Water and Lipid-Water Interfaces?

This study investigates interaction between hydrophilic (11-mercaptoundecanoic acid (MUA)) and hydrophobic (1-undecanethiol (UDT)) gold nanoparticles (GNPs) with human serum albumin (HSA) protein on air-water and lipid-water interfaces at pH 3 and 7. Vibrational sum frequency generation (VSFG) spectroscopy is used to analyze changes in the intensity of interfacial water molecules and the C-H group of the protein. At the air-water interface, the hydrophobic interaction between the HSA protein and hydrophobic GNPs at pH 3 leads to their accumulation at the interface, resulting in an increased C-H intensity of the protein with a slight decrease in water intensity. Whereas, at pH 7, where the negative charge of the protein results in the reduced surface activity of the HSA compared to pH 3, the interaction between alkyl chain of the hydrophobic GNPs and alkyl group of the protein results in the adsorption of the protein-capped GNPs at the interface. This leads to an increased intensity of the C-H group of protein and water molecules. However, negatively charged hydrophilic GNPs do not induce significant changes in the interfacial water structure or the C-H group of the protein due to the electrostatic force of repulsion with the negatively charged HSA at pH 7. In contrast, at the lipid-water interface, both hydrophobic and hydrophilic GNPs interact with HSA protein, causing disordering of interfacial water molecules at pH 3 and ordering at pH 7. Interestingly, similar behavior of the protein with both types of GNPs results in comparable ordering/disordering at the interface depending on the pH of solution. Furthermore, the VSFG results obtained with the deuterated lipid suggest that changes in ordering and disorder occur due to increased protein adsorption in the presence of GNPs, causing alterations in the membrane structure. These findings give a better understanding of the mechanisms that govern protein-nanoparticle interaction and their consequential effects on the structure, function, and behavior of molecules at the biological membrane interface, which is crucial for developing safe and effective nanoparticle-based therapeutics.

Exploring the dynamic changes in hydrogen bond structure of water and heavy water under external perturbation of DMF

The Raman spectra of DMF-water/heavy water binary solutions at different volume ratios are measured to investigate the hydrogen bond structure between N, N-dimethylformamide (DMF) and water/heavy water. It was observed that when VDMF below 40 %, DMF reinforces the hydrogen bond among water molecules through the substitution of a small amount of water molecules within the tetrahedral structure. However, a similar enhancement phenomenon is not observed in heavy water. When VDMF is less than 60 %, the hydrogen bonds among DMF and heavy water molecules affect the symmetry of OD covalent bond. Furthermore, as VDMF exceeds 40 %/60 %, the tetrahedral structures of water and heavy water are gradually replaced by DMF·3H2O/3D2O, DMF·2H2O/2D2O, and DMF·H2O/D2O clusters. The transition point of hydrogen bond structure in DMF- aqueous solution moved to VDMF = 15 % under the influence of under the influence of dynamic high pressure caused by pulsed laser beam. This study provides valuable insights into the microstructure of water/heavy water clusters.

Free energy decompositions illuminate synergistic effects in interfacial binding thermodynamics of mixed surfactant systems.

Recent vibrational sum frequency generation spectroscopic experiments [Sengupta et al., J. Phys. Chem. Lett. 13, 11391-11397 (2022)] demonstrated synergistic interfacial adsorption effects between the anionic dodecyl sulfate (DS-) and the polar, but charge-neutral hexaethylene glycol monododecyl ether (C12E6), surfactants. In this study, the interfacial adsorption thermodynamics underlying these synergistic effects are analyzed through free energy decompositions. A general decomposition method utilizing alchemical intermediate states is outlined. Combining free energy decompositions with the potential distribution theorem illuminates the statistical interpretations of correlated effects between different system components. This approach allows for the identification of the physical effects leading to synergistic adsorption thermodynamics of DS- binding to the air-C12E6-water interface. The binding properties are found to result from a combination of effects predominantly including energetic van der Waals stabilization between DS- and C12E6, as well as competing energetic and entropic effects due to changes in the interfacial water structure as a result of introducing a C12E6 monolayer into the bare air-water interface.

Laboratory experiments on the sublimation of methane through ice dust layers and applications to cometary activity

Context. Comets are small celestial bodies made of ice, dust, and rock that orbit the Sun. Understanding their behavior as they warm up at perihelion unveils many pieces of information about the interior and general morphology of the ices hidden under the dust. Aims. The goal of this research is to study the sublimation of CH4 through amorphous solid water (ASW), with a focus on the structural changes in water and the influence of a layer of indene (as a proxy of the crust) during a period of thermal processing, which we use in a controlled laboratory setting to simulate cometary environments. Methods. Ices at a CH4/H2O abundance ratio of about 0.01 are deposited and layered, or co-deposited, at 30 K and are heated until 200 K (or 140 K) with a ramp of either 1 or 5 K min−1. We use mass spectrometry and infrared spectroscopy to analyze the results. Results. Depending on the heating ramp and type of deposition, the sublimation of methane through ASW varies, being lower in intensity and higher in temperature when the co-deposited structure is considered. When two temperature cycles are applied, the second one sees less intense CH4 desorptions. When indene is placed above the ice mixtures, we find that the thicker its layer, the later the methane desorption. However, this later desorption sees a greater quantity of methane released due to water reorganization and higher desorbed material pressure. Conclusions. The structural changes of water ice drive volatile and hyper-volatile desorption because of the transition from high to low intrinsic density and transformation from amorphous to crystalline. This desorption indicates that such material has been deposited at low temperatures in agreement with previous theories on cometary ices formed in the pre-stellar cloud. During the two temperature cycles of our experiments, most of the released material is seen to be pristine and the processed part, if any, is of a negligible quantity, in agreement with dust-rock cometary studies.

Unravelling the Mechanism behind Charge Reversal at Silica Nanoparticle-Model Cell Membrane Interfaces.

Vibrational sum frequency generation spectroscopy is used to understand the interactions of silica nanoparticles (SNPs) with a model cationic membrane (1,2-dipalmitoyl-3-(trimethylammonium)propane, DPTAP) by monitoring changes in the interfacial water and lipid structure at pH ∼ 2 and pH ∼ 11. Our study reveals that, at pH ∼ 11, SNPs are attracted to DPTAP due to electrostatic forces, causing changes in the interfacial water structure and lipid membrane. At high concentrations of SNPs (≥70 pM), the interfacial charge reversed from positive to negative, inducing the formation of new hydrogen-bonded structures and reorganization of water molecules. Conversely, negligible changes are observed at pH ∼ 2 due to nearly neutral charge of the SNPs. Molecular dynamics simulations demonstrated that the interfacial potential due to model membrane and SNPs dictates the water structure at the interface. These results elucidate the fundamental mechanism governing interfacial interactions and could have implications in drug delivery, gene therapy, and biosensing.

Roles of hydrogen bonding interactions and hydrophobic effects on enhanced water structure in aqueous solutions of amphiphilic organic molecules

Insights into the solute-induced water structural transformations are essential to understand the role of water in biological and chemical reaction processes. Herein, the structural changes in water induced by amphiphilic organic molecules were investigated using concentration-dependent derivative Raman spectroscopy (DRS) combined with two-dimensional Raman correlation spectroscopy (2D Raman-COS). We shall restrict our attention in this work to binary mixtures of water with dimethyl sulfoxide (DMSO), acetone, and isopropanol (IPA), all of which have similar chemical structures. The spectral changes in O:H and OH stretching modes illustrate that the solute molecules induce an enhancement of the water structure in dilute solutions, where the enhanced degree of water structure is closely related to the size of the dipole moment of organic molecules. In addition, the transformations of solute-induced water-specific structures were evaluated by 2D Raman-COS, which shows that the strong hydrogen bond (H-bond) structure of water is more sensitive to organic molecules and induces a transition to the weak H-bond structure of water.

Adsorption dynamics and hydrothermal stability of MOFs aluminium fumarate, MIL-160 (Al), and CAU-10-H, and zeotype TiAPSO for heat transformation applications

Metal-organic frameworks (MOFs) can be beneficial for heat transformation applications due to their potentially high water uptake and tunable working temperature levels. Although the hydrothermal stability has been assessed in some cases in terms of maximum water uptake and structural changes, there is no data on the impact of hydrothermal stress tests on adsorption dynamics. However, to maintain the designed heating or cooling power in the application, the hydrothermal stability in terms of both water uptake and adsorption dynamics is decisive. To close this gap, we present experimental data for the comprehensive evaluation of hydrothermal stability for three different MOFs and the commercially available zeotype TiAPSO. The hydrothermal stress test includes around 70,000 temperature swing cycles on aluminium sheets with a binder-based coating of different adsorbents. As a novelty of this study, adsorption dynamics are determined before and after the hydrothermal stress test using effective thermal resistances and the characteristic temperature difference. Our results show degradation in terms of a decrease in uptake around 5–10% after hydrothermal stress test for all samples. Under temperature boundary conditions relevant for the application, MIL-160(Al) shows even a drastic uptake reduction of around 35–45%. Except for CAU-10-H, none of the adsorbents show a degradation in terms of increased heat and mass transfer resistance. In case of CAU-10-H, the overall effective heat and mass transfer resistance increases by around 30–40% after the hydrothermal stress test. These results indicate that the hydrothermal stability of MOFs must be assessed in terms of both, uptake and adsorption dynamics, to ensure stable long-term performance in real-world devices.

Greenery and water structure before and after political system transformation. A Poznań city case study

The greenery and water structure, in the form of wedges cutting into the city, is a characteristic and unique element of Poznań’s urban model. Already before the Second World War, it became the matrix setting the framework for spatial and natural connections within and around the city. These areas were originally clearly demarcated and formed an organic network that permeated the built-up areas. It was this local network of linkages that was to have the greatest impact on the quality of urban living, climate improvement, biodiversity and the functional and spatial structure of the city.
 In the idea of the socialist city, ensuring access to green spaces for the masses, was one of the essential policy elements of the time. However, over time, in the various models of the city proposed by successive planners, these interconnections began to disappear and the individual bands were narrowed and sometimes discontinued altogether.
 This study aims to verify the urban planning models of the city of Poznań against the original idea of a wedge-ring system of greenery and water areas, before and after the political transformation in 1989.
 How does this original structure function today and how have the socio-economic changes that followed the fall of communism affect the greenery and water solutions proposed in the new city model?
 A comparative analysis of changes in green and water structure in the different spatial models of the city of Poznań, before and after the political transformation, makes it possible to observe the pace and directions of these changes. The analysis was based on the findings of the then-current master plans and on the studies of spatial development conditions and directions, which are an expression of the city’s spatial policy. It can be used to verify the assumptions made or even to change the current model of the city.

Quality characteristics of fresh noodles with low-sodium salt and the underlying mechanisms.

Influence of low-sodium salt on water mobility, chemical interactions, and structural changes in noodles was investigated to explore the underlying mechanisms of noodle quality changes, and the results were in comparison with those of NaCl and KCl. Low-sodium salt increased the cooking loss, hardness, chewiness, maximum tensile strength, and tensile fracture distance of noodles. Low-sodium salt enhanced the interaction of water and non-aqueous components in noodles by reducing water mobility. Besides, chemical interaction test showed that low-sodium salt induced the oxidation of some free SH groups to form SS bonds, and strengthened the hydrophobic interaction and hydrogen bonds of gluten. Fluorescence spectra revealed that low-sodium salt changed the microenvironment of gluten molecules. Scanning electron microscopy (SEM) images showed that low-sodium salt noodles presented a more continuous and compact microstructure. Among the three kinds of salted noodles, some qualities of low-sodium salt noodles were equivalent to or slightly worse than those of NaCl noodles, but higher than those of KCl noodles. Hence, replacing part of NaCl with KCl in noodle products is an effective method to reduce sodium content.