Water Cluster Size Research Articles

Exploration of the Existence Forms and Patterns of Dissolved Oxygen Molecules in Water

HighlightsA clear negative correlation between the size of water clusters and theconcentration of dissolved oxygen was observed. This implied that smaller clusters water exhibits higher concentrations of dissolved oxygen.Oxygen molecules are primarily existed at the surfaces or interfaces of waterclusters and can rapidly traverse the gas liquid interface.A semi empirical formula relating the average number of water molecules in acluster to 17O NMR half peak width was derived, demonstrating an approximatelin ear relationship.

Nonaggregated Anions Enable the Undercooled Aqueous Electrolyte for Low-Temperature Applications.

Aqueous batteries, with the advantages of high safety and low cost, are highly promising for large-scale energy storage. However, freezing of the aqueous electrolyte limits the low-temperature operation. Here, we propose and achieve a highly dispersed solvation structure in the electrolyte by coupling nonaggregated Cl- anions, which reduces the water cluster size and prevents the solidification of the aqueous electrolyte until -136.3 °C. The low-temperature LiCl electrolyte exhibits a high ionic conductivity (1.0 mS cm-1) at -80 °C and enables a stable low-temperature Ag/AgCl reference electrode at -50 °C. Moreover, the polyaniline-based battery can work at an extremely low temperature of -100 °C and shows superior cycling performance of 4000 cycles at -40 °C with 95.7% capacity retention. This work elucidates the correlation between the anion effect and the thermodynamic transition of the electrolyte, offering a novel approach for designing low-temperature electrolytes.

Molecule aging induced by electron attacking

Here we propose a new concept of “molecule aging”: with some special treatment, a molecule could be “aged” by losing some unknown tiny particles or pieces from atoms in the molecule. Such “aging” or loss of unknown tiny particles does not change apparently its molecular structure or chemical composition, but some physicochemical properties could be changed irreversibly. We further confirm such “molecule aging” via a long-term electron attacking to age water (H2O) molecules. The IR spectra show no structural difference between the fresh water and the aged one, while the NMR spectra show that the electron attacking can decrease the size of water clusters. Such facts indicate that the electron attacking indeed can “affect” the structure of water molecule slightly but without damaging to its basic molecule frame. Further exploration reveals that the hydrogen evolution reaction (HER) activity of the aged water molecule is lower than the fresh water on the same Pt/C electrocatalyst. The density functional theory calculations indicate that the shortened O–H bond in H2O indeed can present lower HER activity, so the observed size decrease of water clusters from NMR probably could be attributed to the shortening of O–H bond in water molecules. Such results indicate significantly that the molecule aging can produce materials with new functions for new possible applications.

Morphology and Transport Study of Acid-Base Blend Proton Exchange Membranes by Molecular Simulations: Case of Chitosan/Nafion.

Blending a basic polymer (e.g., chitosan) with Nafion can modify some membrane properties in direct methanol fuel cell applications, e.g., controlling methanol crossover, by regulating the morphology of hydrophilic channels. Unraveling the mechanisms by which the channel morphology is modified is essential to formulate design strategies for acid-base blend membrane development. Thus, we use molecular simulations to analyze the morphological features of a blend membrane (at 75/25 chitosan/Nafion wt %), i.e., (i) water/polymer phase organizations, (ii) number and size of water clusters, and (iii) quantitative morphological measures of hydrophilic channels, and compare them to the pure Nafion in a wide range of water contents. It is found that the affinity of water to different hydrophilic groups in the blend membrane can result in more distorted and dispersed hydrophilic phase and fewer bulk water-like features compared to pure Nafion. Also, the width of the hydrophilic network bottleneck, i.e., pore limiting diameter (PLD), is found to be almost five times smaller for the blend membrane compared to Nafion at their maximum water contents. Moreover, by changing the chitosan/Nafion weight ratio from 75/25 to 0/100, we show that as Nafion content increases, all channel morphological characteristics alter monotonically except PLD. This is mainly due to the strong acid-base interactions between Nafion and chitosan, which hinder the monotonic growth of PLD. Interestingly, water and methanol diffusion coefficients are strongly correlated with PLD, suggesting that PLD can be used as a single parameter for tailoring the blending ratio for achieving the desired diffusion properties of acid-base membranes.

Real-time detection of the transport of water cluster across cytomembrane with piezoelectric sensor

Acquiring insight into the transport of water clusters across cytomembrane is vital and essential for elucidating cell functions and water channels. Herein, A highly sensitive living cell analysis platform was developed for monitoring the transport dynamics of water clusters through water channels by combining the piezoelectric transducer and the hypotonicity-caused cell volume regulation. The various drinking water was used as the hypotonic perfusate to stimulate vascular endothelial cells and the temporal frequency response to cells was obtained to analyze the transport rate of the influx and efflux of water clusters which is related to water structure. The sensor is capable to distinguish the transport dynamics of different water clusters in five drinking water which the transport rates of water influx of cells are 5.1 ± 0.40, 6.6 ± 0.96, 7.4 ± 0.46, 8.1 ± 0.86, and 8.4 ± 0.80 Hz min−1 (n = 3), respectively, showed that they are ranked in the increasing order: M-water, C-water, S-water, RO-water, d-water. Moreover, inhibitor of HgCl2 was used to block water channels to reveal the water transport via water channels. Conductivity and infrared spectroscopy assays further confirmed the differences of transport dynamics between these drinking water due to the structure or size of water clusters caused by the mineral substance or the electromagnetic field. Therefore, this work provides a novel, simple and effective method for monitoring the transport of different water cluster across cytomembrane.

Steam permeation properties of perfluorosulfonic acid/ceramic composite membranes at a high temperature under various humidity conditions

The perfluorosulfonic acid (PFSA) polymer is an important materials for dehumidification membranes and is typically used at temperatures below 70 °C. In this study, the humid gas separation performances of PFSA membranes were evaluated at temperatures ranging from 80 to 200 °C under various relative humidity (RH) conditions to enable a wide potential range of applications at high temperatures, such as in steam recovery and dehydration membrane reactors. PFSA layers with 80 nm thicknesses were prepared on ceramic supports to achieve a high water permeance of the order of 10−6–10−5 mol/(m2 s Pa) and water/nitrogen permeance ratio ranged from several tens to 100 at temperatures ranging from 150 to 200 °C. This paper discusses the detailed effect of the RH on the permeation properties at 200 °C. The thickness of the PFSA layer is approximately the same as the water cluster size in the PFSA structure, leading to the unique permeation behavior. This study provides insights into the use of PFSA membranes at high temperatures under humid conditions.

Surface Confinement of Finite-Size Water Droplets for SO3 Hydrolysis Reaction Revealed by Molecular Dynamics Simulations Based on a Machine Learning Force Field

As an important source for sulfuric acid in the atmosphere, hydrolysis of sulfur trioxide (SO3) takes place with water clusters of sizes from several molecules to several nanometers, resulting in various final products, including neutral (H2SO4)-(H2O) clusters and ionic (HSO4)--(H3O)+ clusters. The diverse products may be due to the ability of proton transfer and the formation of hydrated ions for water cluster of finite sizes, especially the sub-micrometer ones. However, the detailed molecular-level mechanism is still unclear due to the lack of available characterization and simulations tools. Here, we developed a quantum chemistry-level machine learning (ML) model to simulate the hydrolysis of SO3 with water clusters of sizes up to nanometers. The simulation results demonstrate diverse reaction paths taking place between SO3 and water clusters of different sizes. Generally, neutral (H2SO4)-(H2O) clusters are preferred by water clusters of ultra-small size, and a loop structure-mediated mechanism with SO3(H2O)n≤4 structures and a non-loop structure-mediated mechanism with structure relaxation are observed. As the water cluster size increases to (H2O)8, a (HSO4)--(H3O)+ ion-pair product emerges; and the Eigen-Zundel ion conversion-like proton transfer mechanism takes place and stabilizes the ion pairs. As the water cluster sizes further increase beyond several nanometers ((H2O)n≥32), the (SO4)2-[(H3O)+]2 ion-pair product appears. The reason could be that the surface of these water clusters is large enough to screen Coulomb repulsion between two tri-coordinated ion-pair complexes. These findings would provide new perspectives for understanding SO3 hydrolysis in the real atmosphere and sulfuric acid chemistry in atmospheric aerosols.

Combining molecular simulation and experiment to understand the effect of moisture on methane adsorption in kerogens

There is a limited understanding of the critical impact moisture has on shale gas resource estimation by affecting gas adsorption and pore structure. Laboratory experiments on dry and 95% relative humidity (R.H.) isolated kerogens are combined with Grand Canonical Monte Carlo (GCMC) and Molecular Dynamic (MD) simulations for kerogen models, including matrix and slits (0.5, 1.0, 1.5, and 2.0 nm) with a range of moisture contents (0–42 wt% on a total organic carbon content (TOC) basis) to better understand how moisture impacts methane adsorption. Higher methane adsorption capacities (Qm) and micropore volumes (Vmicro) are observed for simulated kerogens since all pores in GCMC are accessible. Moisture has a negative effect on Qm, displaying ‘rapid’, ‘gentle’, and ‘slow’ stages with increasing moisture in simulation. Reductions in Qm (61–75%) and Vmicro (88–93%) are obtained for isolated kerogens containing moisture of 38–70 wt% TOC with up to 56% of the moisture in micropores. The same Qm and Vmicro reductions can be reached for the simulated kerogens with moisture contents of 4–24 wt% TOC for matrix and slits. The relative coordination number (Cr) from MD simulation indicates water has a stronger affinity than methane for all functional groups with preferred sorption sites like carboxyl (COOH) under reservoir conditions. The microporosity controls condensed water cluster size. Water adsorbed in ultra-micropores (<0.7 nm) leads to ‘rapid’ reduction, the ‘gentle’ Qm reduction stage arises from water condensing, and filling of remaining pores at the highest moisture is related to the ‘slow’ Qm reduction stage. Therefore, water reduces the methane adsorption capacity of kerogen mainly by occupying and blocking the pore volume rather than competing directly with methane for sorption sites.

Understanding the magnetizing process of water and its effects on cementitious materials: A critical review

Magnetized Water (MW) is a fascinating research subject for improving the properties of the cementitious composite due to its physicochemical alterations in cluster size and surface tension of water. However, these physicochemical changes have shown contradictory results in the literature. This paper intends to expound on physicochemical properties variations of MW and its effect on cement composite performance. Consequently, all existing Magnetic fields (MFs) for water treatment were classified into two main categories. The effective MF parameters of these methods on MW characterizations were discovered and collected from the literature, and they are proposed to be considered in future studies to make results more comparable and compatible. The different techniques for molecular cluster examination are introduced to understand each technique's solidity in water cluster investigations. Then the influence of MF on cluster size and surface tension of water was scrutinized, and the results of studies were summarized end of each section inside comprehensive tables. In the continuation, the charming effects of treated water with effective MF parameters on cement composites' fresh and hardened state were addressed to appreciate the magnitude to which MW affects cement composites properties.

Molecular‐Dynamics Modeling of Nafion Membranes

AbstractThe Nafion is a commonly used polyelectrolyte membrane (PEM) in fuel cells and flow batteries. Nanocomposites of Nafion are used to enhance temperature resistance and proton conductivity. The molecular‐dynamics simulation results are reported for Nafion films of different thicknesses confined between two potential walls of variable wettability, mimicking the nanofiller surfaces. The water cluster sizes show an increase with film thickness for the high wettability cases, in agreement with SAXS experiments. The in‐plane water diffusion is considerably enhanced for the high wettability walls. The first results on the annealing effects on both structure, dynamics, and electric conductivity of the membranes are also reported. The hydrophilic channels evolution upon annealing will be discussed.

Attosecond Photoionization Dynamics: from Molecules over Clusters to the Liquid Phase

Photoionization is a process taking place on attosecond time scales. How its properties evolve from isolated particles to the condensed phase is an open question of both fundamental and practical relevance. Here, we review recent work that has advanced the study of photoionization dynamics from atoms to molecules, clusters and the liquid phase. The first measurements of molecular photoionization delays have revealed the attosecond dynamics of electron emission from a molecular shape resonance and their sensitivity to the molecular potential. Using electron-ion coincidence spectroscopy these measurements have been extended from isolated molecules to clusters. A continuous increase of the delays with the water-cluster size has been observed up to a size of 4-5 molecules, followed by a saturation towards larger clusters. Comparison with calculations has revealed a correlation of the time delay with the spatial extension of the created electron hole. Using cylindrical liquid-microjet techniques, these measurements have also been extended to liquid water, revealing a delay relative to isolated water molecules that was very similar to the largest water clusters studied. Detailed modeling based on Monte-Carlo simulations confirmed that these delays are dominated by the contributions of the first two solvation shells, which agrees with the results of the cluster measurements. These combined results open the perspective of experimentally characterizing the delocalization of electronic wave functions in complex systems and studying their evolution on attosecond time scales.

Infrared Spectroscopy of Stepwise Hydration Motifs of Sulfur Dioxide.

Experimental characterization of microscopic events and behaviors of SO2-H2O interactions is crucial to understanding SO2 atmospheric chemistry but has been proven to be very challenging due to the difficulty in size selection. Here, size-dependent development of SO2 hydrate structure and cluster growth in the SO2(H2O)n (n = 1-16) complexes was probed by infrared spectroscopy based on threshold photoionization using a tunable vacuum ultraviolet free electron laser. Spectral changes with cluster size demonstrate that the sandwich structure initially formed at n = 1 develops into cycle structures with the sulfur and oxygen atoms in a two-dimensional plane (n = 2 and 3) and then into three-dimensional cage structures (n ≥ 4). SO2 is favorably bound to the surface of larger water clusters. These stepwise features of SO2 hydration on various sized water clusters contribute to understanding the reactive sites and electrophilicity of SO2 on cloud droplets, which may have important atmospheric implications for studying the SO2-containing aerosol systems.

Active material crossover suppression with bi-ionic transportability by an amphoteric membrane for Zinc–Bromine redox flow battery

Zinc-bromine redox flow batteries (Zn/Br2 RFBs) are gaining attention as a next-generation energy storage system with the advantages of a cost-effective redox couple material price, high output, and high energy density. However, bromine (Br2) crossover through a commercial porous membrane causes self-discharge to lower the capacity retention. Nafion, a commercial ion exchange membrane, can lower the crossover but has low voltage efficiency due to high membrane resistance. To address this trade-off, the amphoteric functionalized silica (Am-SiO2) is introduced into the Nafion membrane (Nafion/Am-SiO2). It suppresses the crossover of active materials such as Br2 and polybromide (Brn−) and possesses high ionic conductivity due to the quaternary ammonium and sulfonic groups on the Am-SiO2 surface. In addition, increasing the water content in the membrane prevents the expansion of the water cluster size, which could help balance bi-ionic transport. As a result, the composite membrane showed 83.3 and 19.0 times higher ion selectivity than the commercial porous membrane (SF600) and ion-exchange membrane (NRE-212). Compared to SF600 and NRE-212, the energy efficiency of Nafion/Am-SiO2 was improved by 4.2 and 6.4%, respectively. Balancing anion and cation transport can be successfully applied in Zn/Br2 RFBs by introducing an amphoteric group into an ion-exchange membrane.

Drying of water from porous structures investigated by time-resolved X-ray tomography

In this contribution, we apply time-resolved X-ray tomography to study drying of water in porous ceramic substrates used in emission control technologies. A time resolution of 2 s is achieved, and allows to observe the spatiotemporal distribution of water in structured porous materials. An image processing framework based on machine learning is introduced to track pore emptying and filling in a large number of 3D scans. Drying curves are extracted from the tomographic data to investigate drying in materials with different structural properties. Water redistribution by capillary pumping and rapid pore emptying by Haines jumps are observed, and their impact on drying dynamics is discussed. The relationship between the evolution of water clusters and different drying regimes is established. The obtained information on the interplay between pore emptying, water redistribution and the size of water clusters provides an important link between the structural properties of dried materials and their drying rate.

Mesoscale hydrated morphology of perfluorosulfonic acid membranes

AbstractFuel cells are expected to play an important role in global carbon neutralization and future social development with high conversion efficiency and zero emissions. The core of the fuel cell is the proton exchange membrane (PEM). However, the unclear of the proton transport mechanism in PEMs limits the development of membranes with improved performance. Perfluorosulfonic acid (PFSA) membranes are currently the most widely used type of PEM, and exhibit varying proton transport capabilities with various chemical structures. In this study, the hydration morphology of several PFSA membranes was studied using dissipative particle dynamics. The result shows that under low water content the hydrophilic and hydrophobic phases separated and the water clusters are relatively isolated. The increased water content formed hydrophilic channels, while the increase in equivalent weight decreases the water cluster size and improves water dispersion. Aciplex 1128 shows great variation owing to the presence of a long sulfonic acid terminated side chain in water cluster size and dispersion compared with Nafion. The average diffusivity and mean square displacement results showed similar results. These results will promote the development of high performance PEM for fuel cells.

Hydrogen Bond Energies in Formation of Water Molecule Clusters

During the last decades, the interest in water structure has increased as an important theoretical and practical problem, connected with different industrial and biological applications. Theoretically, the mechanisms of water molecules cluster formation have been of special interest. It has been assumed that aggregation of water molecules depends on the energy of hydrogen bonds. The character of this process was investigated in the present study. The approach was based on measurements of the wetting angle θ of water droplets at different energy levels during their evaporation. Taking into account previous findings that θ depends on the average energy of hydrogen bonds between water molecules, it was assumed that the size of water clusters is related to the value of θ, measured at different energy levels. This assumption was confirmed by the obtained experimental results.

Effects of Hydration and Temperature on the Microstructure and Transport Properties of Nafion Polyelectrolyte Membrane: A Molecular Dynamics Simulation.

To investigate the effects of temperature and hydration on the microstructure of polymer electrolyte membrane and the transport of water molecules and hydronium ions, molecular dynamics simulations are performed on Nafion 117 for a series of water contents at different temperatures. The interactions among the sulfonate groups, hydronium ions, and water molecules are studied according to the analysis of radial distribution functions and coordination numbers. The sizes and connectivity of water clusters are also discussed, and it is found that the hydration level plays a key role in the phase separation of the membrane. However, the effect of the temperature is slight. When the water content increases from 3.5 to 16, the size of water clusters in the membrane increases, and the clusters connect to each other to form continuous channels for diffusion of water molecules and hydronium ions. The diffusion coefficients are estimated by studying the mean square displacements. The results show that the diffusion of water molecules and hydronium ions are both enhanced by the increase of the temperature and hydration level. Furthermore, the diffusion coefficient of water molecules is always much larger than that of hydronium ions. However, the ratio of the diffusion coefficient of water molecules to that of hydronium ions decreases with the increase of water content.

The Role of Modification of the Structure of Water and Water-Containing Systems in Changing Their Biological, Therapeutic, and Other Properties Overview

Based on published research on modifying the structure of water and water-containing systems, we assess external influence methods: temperature, magnetic field, light radiation, and their combination. We evaluate changes in the electrophysical, photo- and pH-metric biological, therapeutic, and other properties of water systems using non-destructive electrophysical research methods, i.e., thermometry, pH, laser interference, dynamic light scattering, microelectrophoresis, conductivity, surface tension, dielectric constant, polarimetric measurements, atomic force microscopy, and UV and EPR spectroscopy. The effects of temperature or magnetic field lead to a change in the content and size of water clusters, and physicochemical, biological, therapeutic, and other changes in the properties of water and water-containing systems. The combined effect of a magnetic field and curative mud and the impact of magnetised mineral water have a more pronounced therapeutic effect than only mineral water or curative mud. The data presented indirectly indicate structural changes in water and water-containing systems. We conclude that the primary mechanism of action of a magnetic field, light, or a combination of these factors on water and water-containing systems, including mineral water and therapeutic mud, is a change in the structure of water.

EMPLOYMENT OF MAGNETIC WATER TREATMENT IN CONSTRUCTION

Magnetic treatment (MT) is one of the interested techniques that have been widely used in various aspects of life due to its positive effectiveness on the properties of water when utilized. Construction sector received great attention by researchers in order to employ magnetic water (MW) in the production of various building materials especially cement-based materials. This is due to the role of water is involved directly in the hydration process of the cement as well as curing process. The effectiveness of using MW came from the influence of magnetic field (MF) on physical properties of water molecular such as surface tension. Break down in the size of water clusters, therefore, is occurred which increases the activity of water molecular to penetrate the cement particle easily to involve in the hydration process. Various parameters may affect the magnetization process such as time, strength of MF and speed of water through the MF. In the current paper, the impact of using MW in the production of various construction and building materials that based on cement is addressed to clarify the actual need in adopting such an attractive technology to magnetize the water to be used in mixing and curing cement-based materials to construct sustainable concrete structures in construction sites.

Imidazole-Based Ionic Liquids with BF4 as the Counterion Perform Outstanding Abilities in Both Inhibiting Clay Swelling and Lowing Water Cluster Size.

Promoting fluid transportation in porous media has important applications in energy, pedology, bioscience, etc. For this purpose, one effective way is to prevent swelling through surface modification; however, it is far from enough in real cases, such as ultra-low permeability reservoirs and tight oils. In this study, we considered the comprehensive effects of inhibiting clay swelling, flocculation performance, reducing water clusters and interfacial tension and developed a series of imidazole-based tetrafluoroborate ionic liquids (ILs) with different lengths of alkyl chains. Through measurements of anti-swelling rates, XRD, SEM, 17O NMR, molecular dynamics simulation, zeta potential, flocculation evaluation, interfacial tension and a core flooding experiment based on ultra-low permeability reservoirs, the relationships between the molecular structure and physicochemical properties of ILs have been revealed. Interestingly, one of the selected ILs, imidazole-based tetrafluoroborate ILs (C8-OMImBF4), shows excellent performance, which is helpful to design an effective strategy in promoting fluid transportation in narrow spaces.