Polar Water Molecules Research Articles

High photoluminescence quantum yield and stability achieved by encapsulating MAPbBr3 QDs in UIO-66 and their application in LEDs.

Lead halide perovskite quantum dots (QDs) have been extensively studied due to their excellent photoelectric performance. However, the stability of MAPbBr3 QDs is affected by inevitable factors such as light, heat, and moisture, which limits their practical applications. In this work, stable metal-organic framework UIO-66 was synthesized via a solvothermal method, and the composite MAPbBr3@UIO-66 was prepared through an in-situ growth method. Owing to the wide bandgap, small pore size, and regular geometric structure, UIO-66 can confine the size and uniformity of the perovskite QDs encapsulated within the framework, maximally preserving the luminescent properties of the perovskite QDs. Furthermore, UIO-66 isolates the perovskite QDs from contact with polar water molecules in the air, significantly enhancing the stability of the perovskite QDs. The synthesized composite material exhibits high stability and excellent optical performance, with a photoluminescence quantum yield (PLQY) of up to 78.9% in an air environment. After being stored under natural conditions for 35 days, it still retains 65% of its high luminescence intensity and fluorescence quantum efficiency. When packaged into green and white LEDs, the LEDs demonstrate high brightness and good monochromaticity, maintaining stable brightness even after 2.5 hours of continuous operation. These superior characteristics indicate that the composite material MAPbBr3@UIO-66 has great potential for application in LED technology.

Nanofluidic sensing inspired by the anomalous water dynamics in electrical angstrom-scale channels

Manipulation of confined water dynamics by voltage keeps great importance for diverse applications. However, limitations on the membrane functions, voltage-control range, and unclear dynamics need to be addressed. Herein, we report an anomalous electrically controlled gating phenomenon on cation-intercalated multi-layer Ti3C2 membranes and reveal the confined water dynamics. The water permeation rate was improved rapidly following the application and rise of voltage and finally reached a maximum rate at 0.9 V. The permeation rate starts to decrease from 0.9 V. Below 0.9 V, the electric field affects the charge and polarity of water molecules and then leads to ordered and denser rearrangement in the two-dimensional (2D) channel to accelerate the permeation rate. Above 0.9 V, with the assistance of metal cations, the surge in current induced aggregation of water molecules into clusters, thereby limiting the water mobility. Based on these findings, a high-performance humidity sensor was developed by simultaneously optimizing the response and recovery speeds through electric manipulation. This work provides flexible strategies in intelligent membrane design and nanofluidic sensing.

Development of Hydrophilic Self-Cleaning and Ultraviolet-Shielding Coatings Incorporating Micro-Titanium Dioxide/Nano-Calcium Carbonate (µ-TiO<sub>2</sub>)/(Nano-CaCO<sub>3</sub>)

The dust accumulation and dirt particles always degrade the transparency of glass, later hampers its various applications such as photovoltaic panels, building glass, and car-windshield. In this study, the hydrophilic self-cleaning coatings have been developed by using the nanocalcium Carbonate particles (nanoCaCO3) and hydrophilic micro-titanium dioxide particles (µ-TiO2). The presence of oxide groups, CO-3 and TiO2- forms a strong attraction of glass to polar water molecules. At the weight ratio of 1: 1 in the CaCO3 to TiO2 mixture, it forms a great hydrophilic property in which the water contact angle (WCA) of coated glass has been recorded as low as 11.46 ±0.85°. The coated glass also showed high transparency in UV and Visible regions. The optical transmission of coated glass was above 89% at the wavelength of 300-400nm and above 97% at the wavelength of 400-800nm. Due to its hydrophilic property, the coated glass is capable of removing the dust particles away via the water stream. The hydrophilic coating spontaneously forms the water-thin film after contact with coated glass without the presence of UV light.

Pervaporation Dehydration Mechanism and Performance of High-Aluminum ZSM-5 Zeolite Membranes for Organic Solvents.

Membrane-based pervaporation (PV) for organic solvent dehydration is of great significance in the chemical and petrochemical industries. In this work, high-aluminum ZSM-5 zeolite membranes were synthesized by a fluoride-assisted secondary growth on α-alumina tubular supports using mordenite framework inverted (MFI) nanoseeds (~110 nm) and a template-free synthesis solution with a low Si/Al ratio of 10. Characterization by XRD, EDX, and SEM revealed that the prepared membrane was a pure-phase ZSM-5 zeolite membrane with a Si/Al ratio of 3.8 and a thickness of 2.8 µm. Subsequently, two categories of PV performance parameters (i.e., flux versus separation factor and permeance versus selectivity) were used to systematically examine the effects of operating conditions on the PV dehydration performance of different organic solvents (methanol, ethanol, n-propanol, and isopropanol), and their PV mechanisms were explored. Employing permeance and selectivity effectively disentangles the influence of operating conditions on PV performance, thereby elucidating the inherent contribution of membranes to separation performance. The results show that the mass transfer during PV dehydration of organic solvents was mainly dominated by the adsorption-diffusion mechanism. Furthermore, the diffusion of highly polar water and methanol molecules within membrane pores had a strong mutual slowing-down effect, resulting in significantly lower permeance than other binary systems. However, the mass transfer process for water/low-polar organic solvent (ethanol, n-propanol, and isopropanol) mixtures was mainly controlled by competitive adsorption caused by affinity differences. In addition, the high-aluminum ZSM-5 zeolite membrane exhibited superior PV dehydration performance for water/isopropanol mixtures.

Construction of macromolecular structure model of Luling coal and study on the dynamic mechanism of micro-wetting process

The physicochemical structure and energy composition of coal macromolecules are the major factors affecting coal wettability. This study thus employed 13C NMR, FTIR, and XPS to determine the chemical structure of coal in the No. 10 coal seam of the Luling coal mine and gain insights into the molecular mechanisms of coal wetting. The results showed that the molecular formula of the Luling 10 model was C290H223O25N5S. Through molecular dynamics simulation, upon the stable adsorption of sodium dodecyl sulfate (SDS) on the coal surface, both the mobility of water molecules and the water molecule content in the interfacial adsorption layer increased. After SDS was added, except for the hydrogen bond energy, the increase rate of each potential energy increased, and van der Waals energy and bond length energy changed the most. The reason for the decrease of hydrogen bond energy is that more atoms in coal macromolecules form hydrogen bonds with polar water molecules. The increase of SDS promoted the significant changes of bond length energy, bond angle energy and van der Waals force of coal, thus increasing the wettability of coal. Taken together, our findings provide important insights into the molecular mechanisms through which surfactants improve chemical wetting.

Parameters and Effects of Magnetic Field and Potassium Carbonate in Water. Applications

The polar water molecule has an angle between the two-hydroxyl O–H bonds of 104.5∘. The unequal sharing of electrons gives a slight negative charge near the oxygen atom and a slight positive charge near the hydrogen atoms of the water molecule. Water is a polar solvent. Hydrogen electromagnetic bonds are formed between water molecules. They involve hydrogen atoms from one water molecule and oxygen from another one. A permanent magnetic field influences the formation of hydrogen bonds between water molecules. Current research by Wu and Brant, 2020 illustrates that the water conductivity at the magnetic induction B = 13500 or 1.35 T increases from 100 to 250 μS · cm−1. The amount of protons in water (H+) decreases with the water alkalization and increasing pH. The work by Yap and co-authors’ indicates that stronger effects on pH, oxidation-reduction potential (ORP), and dissolved oxygen (DO) are observed in the non-reversed polarity of the magnets. Our study uses a constant magnet with the magnetic induction B = 3000 G or 0.3 T; eight permanent magnets are applied to 1000 L of water. Potassium carbonate (K2CO3) is also added, by increasing the alkalinity of water. The application is in livestock as drinking water for sheep and goats.

Exploring the role of γ-Oryzanol on stabilization mechanism of Pickering emulsion gels loaded by α-Lactalbumin or β-Lactoglobulin via multiscale approaches

The research explored the role of γ-oryzanol (γs) on stabilization behavior of Pickering emulsion gels (PEGs) loaded by α-lactalbumin (α-LA) or β-lactoglobulin (β-LG), being analyzed by experimental and computer methods (molecular dynamic simulation, MD). Primarily, the average particle size of β-LG-γS was expressed 100.07% decrease over that of α-LA-γS. In addition, γs decreased the dynamic interfacial tension of two proteins with the order of β-LG < α-LA. Meanwhile, quartz crystal microbalance with dissipation proved that β-LG-γS exhibited higher adsorption mass and denser rigid interface layer than α-LA-γS. Moreover, the hydrophobic group of γS had electrostatic repulsion with polar water molecules in the aqueous phase, which spread to the oil phase. β-LG-γS had lower RMSD/Rg value and narrower fluctuation compared with α-LA-γS. This work strength the exploration of interfacial stabilization mechanism of whey protein-based PEGs, which enriched its theoretical research for industrial-scale production as the replacement of trans fat and cholesterol.

Water‐tree aging characteristics of chloroacetic acid allyl ester grafted crosslinked polyethylene

AbstractTo investigate the inhibition effect of chloroacetic acid allyl ester (CAAE) grafting modification on water‐tree aging in crosslinked polyethylene (XLPE), CAAE grafted XLPE (XLPE‐g‐CAAE) with different CAAE contents are prepared by melt blending and grafting modification method. The accelerated water‐tree aging experiments are carried out by the water‐blade electrode method. It is found that XLPE‐g‐CAAE has a great inhibitory effect on the water‐tree aging compared to XLPE, and XLPE‐g‐CAAE with 1.0 phr CAAE has the most significant effect on the water‐tree growth in the scope of the study. The microstructure of XLPE and XLPE‐g‐CAAE is investigated by thermal elongation, gel content, and static water contact angle, respectively. The results show that the grafting of CAAE containing polar groups can enhance the polarity of XLPE and improve the hydrophilicity, which has a dispersing effect on the polar water molecules entering the polymer. Thus, the water molecules are not easy to gather, inhibiting the water‐tree growth. Meanwhile, although the mechanical properties of XLPE‐g‐CAAE decrease to a small extent, and the relative dielectric constant and dielectric loss factor increase slightly, but the performance still meet the requirements of water‐tree resistance XLPE cable insulation.Highlights CAAE with polar groups was successfully grafted onto XLPE. The polar groups can enhance the polarity of XLPE to improve the hydrophilicity. CAAE grafting can inhibit the water‐tree growth in XLPE. The dielectric properties meet the requirements of water‐tree resistance XLPE.

Enhancing the photothermal efficiency of MoS2 through ultraviolet-ozone exposure for improved solar evaporation

MoS2 has been explored as a photothermal layer for solar-driven water evaporators to produce clean water. However, there have been no reports studying the effects of ultraviolet-ozone (UVO) exposure on the photothermal properties of MoS2. This study investigates the impact of UVO exposure (10, 20, and 30 minutes) on bulk 2H-MoS2 synthesized via a hydrothermal method at 200°C for 16 hours. The freshly prepared MoS2 contained high concentrations of molybdenum oxide phases, which significantly diminished after 10 minutes of UVO exposure, indicating improved purity of MoS2. The increased purity of UVO-exposed MoS2 led to a rise in layer temperature to 47.37°C, surpassing the 43.40°C temperature of MoS2 without UVO exposure. Extending the UVO exposure to 30 minutes further increased the number of surface edge sites, thereby enhancing the wettability of MoS2 due to the increased binding sites for polar water molecules. Consequently, MoS2 exposed to UVO for 30 minutes demonstrated the highest evaporation rate of 1.83 kg m−2 h−1, achieving a photothermal efficiency of 94%, a high salt rejection rate of 99.98%, and a high heavy metal ion rejection rate of 91.84%. Therefore, the application of UVO-exposed MoS2 serves as an effective photothermal layer for sustainable and eco-friendly clean water production technologies.

Probing Interfacial Aging of Model Adhesion Joints under a Hygrothermal Environment at a Molecular Level.

Generally, for adhesive joints, the polar water molecules in humid environments can have a critical effect on the interfacial structures and structural evolution adjacent to the solid substrates. Regarding this, it is still a big challenge to detect and understand the interfacial hygrothermal aging process at the molecular level in real time and in situ. In this study, to trace the interfacial hygrothermal aging process of a classical epoxy formula containing diglycidyl ether of biphenyl A (DGEBA) and 2,2'-(ethylenedioxy) diethylamine (EDDA) with sapphire and fused silica in a typical hygrothermal environment (85 °C and 85% RH), sum frequency generation (SFG) vibrational spectroscopy was used to probe the molecular-level interfacial structural change over the time. The structural evolution dynamics at the buried epoxy/sapphire and epoxy/silica interfaces upon hygrothermal aging were revealed directly in situ. The interfacial delamination during hygrothermal aging was also elucidated from the molecular level. Upon hygrothermal aging, the interfacial CH signals, such as the ones from methyl, methylene, and phenyl groups, decreased significantly and the water OH signals increased substantially, indicating the water molecules had diffused into the interfaces and destroyed the original interactions between the epoxy formula and the substrates. Further analysis indicates that when the integrated signals in the CH range declined to their minimum and leveled off, the interfacial delamination happened. The tensile experiment proved the validity of these spectroscopic experimental results. Our study provides first-hand and molecular-level evidence on a direct correlation between the diffusion of the surrounding water molecules into the interface and the evolution/destruction of the interfacial structures during hygrothermal aging. More importantly, it is proved, SFG can be developed into a powerful tool to noninvasively reveal the local interfacial delamination in real time and in situ under extreme hygrothermal conditions, complemented by the mechanic test.

Spontaneous Wetting Induced by Contact-Electrification at Liquid-Solid Interface.

Wettability significantly influences various surface interactions and applications at the liquid-solid interface. However, the understanding is complicated by the intricate charge exchange occurring through contact electrification (CE) during this process. The understanding of the influence of triboelectric charge on wettability remains challenging, especially due to the complexities involved in concurrently measuring contact angles and interfacial electrical signals. Here, the relationship is investigated between surface charge density and change of contact angle of dielectric films after contact with water droplets. It is observed that the charge exchange when water spared lead to a spontaneous wetting phenomenon, which is termed as the contact electrification induced wetting (CEW). Notably, these results demonstrate a linear dependence between the change of contact angle (CA) of the materials and the density of surface charge on the solid surface. Continuous CEW tests show that not only the static CA but also the dynamics of wetting are influenced by the accumulation charges at the interface. The mechanism behind CEW involves the redistribution of surface charges on a solid surface and polar water molecules within liquid. This interaction results in a decrease in interface energy, leading to a reduction in the CA. Ab initio calculations suggest that the reduction in interface energy may stem from the enhanced surface charge on the substrate, which strengthens the hydrogen bond interaction between water and the substrate. These findings have the potential to advance the understanding of CE and wetting phenomena, with applications in energy harvesting, catalysis, and droplet manipulation at liquid-solid interfaces.

Nanostructured lubricant additives for titanium alloy: Lubrication by the solid-liquid interface with Coulomb repulsion

In this work, the advantage of Coulomb repulsion in the intermolecular forces experienced by molecules on the solid-liquid nanosized contact interface is taken, and the superior friction-reducing property of Cu3(PO4)2·3H2O (CuP) oil-based additives has been confirmed for titanium alloy. Three-dimensional (3D) CuP nanoflowers (CuP-Fs) with a strong capillary absorption effect are prepared to achieve the homogeneous mixing of solid CuP and lubricating oil. Lubrication by CuP-Fs additives for titanium alloy, friction coefficient (COF) can be reduced by 73.68%, and wear rate (WR) reduced by 99.69%. It is demonstrated that the extraordinary friction-reducing property is due to the repulsive solid-liquid interface with low viscous shear force originating from Coulomb repulsion between polar water molecules in CuP and non-polar oil molecules. However, any steric hindrance or connection between this repulsive solid-liquid interface will trigger the adhesion and increase the viscous shear force, for example, dispersant, hydrogen bondings, and shaky adsorbed water molecules. Besides, the lamellar thickness of CuP and the molecular size of lubricant both have a great influence on tribological properties. Here the lubrication mechanism based on interface Coulomb repulsion is proposed that may help broaden the scope of the exploration in low-friction nanomaterial design and new lubricant systems.

Superwetting membrane-based strategy for highly efficient separation of dimethyl carbonate and methanol

Dimethyl carbonate (DMC) produced through transesterification, which involves the reaction of methanol (MeOH) with a suitable ester, has been considered as an attractive route for industrial production. Although high-purity DMC can be obtained from DMC/MeOH mixture by energy-intensive extractive distillation or time-consuming pervaporation (PV), it is still challenging to produce pure DMC in an energy-saving and high-efficiency manner. Here we demonstrate an energy-economy yet efficient superwetting membrane (SWM)-based strategy to produce pure DMC by combining porous polytetrafluoroethylene (PTFE) as the solid membrane and eco-friendly water molecules as the liquid inductive agent. The relatively low polar DMC can rapidly and selectively permeate the nonpolar PTFE membrane by nonpolar interaction between PTFE and DMC. Meanwhile, the high polar water molecules generate strong hydration with MeOH, which makes the relatively high polar MeOH/H2O being blocked by the nonpolar PTFE membrane. The SWM system exhibits outstanding separation flux of 1090 L m−2 h−1, with DMC purity higher than 93 wt%. Furthermore, taking advantage of the easy assembly of this SWM with conventional PV, we can produce DMC with purity of 99.4 wt%, showing great potential in practical DMC production.

Interfacial structure and transport properties of concentrated lithium chloride solutions under an electrostatic field

Efficient moisture exchange between liquid desiccants and air is essential for optimizing dehumidification and air-conditioning systems, with the interfacial layer playing a critical role. This work investigates the influence of electrostatic fields (E-fields) on the structural and transport properties of the liquid-vapor interface between aqueous lithium chloride solutions and air at a microscopic scale using molecular dynamics (MD) simulations. Our research reveals that negative normal E-fields deplete ions within the interfacial layer, weakening their interactions with water molecules. Conversely, positive normal E-fields enrich surface ions, attracting a higher concentration of water molecules to the interface. The E-field enhances interactions between water molecules, increasing hydrogen bonds (H-bonds) at the interface. This weakens cohesion between water molecules and the liquid phase, ultimately reducing surface tension and the associated interfacial free energy barrier, facilitating the departure of water molecules from the liquid phase. Negative normal E-fields demonstrate greater advantages due to their pronounced alteration of the interface structure and the polarization of water molecules.

Explosions of Ball Lightning inside Enclosed Spaces

According to observations, the energy density contained inside ball lightning can reach 1010 J/m3, and its charge can range from 10−3 to 10−1 C. Witnesses often report seeing moving sparks about one millimeter in size inside the ball lightning shell. When the ball lightning shell ruptures, charge carriers fly out of it in the form of a sheaf of sparks. For many years, the press has published reports of the destruction of houses inside of which a ball lightning explosion had occurred. These events remained unexplained for a long time. This article, for the first time in the world, provides a physical explanation of these events. This article is based on the ball lightning model developed by the authors. According to this model, ball lightning consists of an ensemble of positively charged elements (dynamic electric capacitors) located inside a spherical shell of polarized water molecules. The dynamic capacitor is a system of cyclically moving electrons and ions. The expansion of this capacitor is restrained by the compression force of the ball lightning shell in the non-uniform electric field of the ball lightning core. The model allows us to find a physical explanation for most of the observed properties of ball lightning. Using the example of a simplified model of ball lightning (when the contribution of the kinetic energy of the dynamic capacitors was not taken into account), an analysis of the forces acting inside ball lightning was carried out. It was shown that when the shell of ball lightning is destroyed, the charges emitted from the core remain on the walls of the room or on loose objects for some time. The Coulomb force of the repulsion of charges turns out to be large enough to squeeze out the walls of a building or throw a heavy object or person out of the house.

Polarized Water Enabled Vertical Dynamic Diode Generator to Output Direct Current

Harvesting various mechanical energy from the daily environment has been proposed as a promising way to power electronic devices in the era of Internet of Things. However, most of existing generators are troubled by complex surface structures to achieve higher power output because of the limitations by interfacial effects and unable to achieve direct current (DC) output in the vertical direction. Herein, by introducing the polarized water molecules at the solid contact interface, a vertical structure dynamic diode DC generator is proposed. In the process of polarization and depolarization, water molecules induce, accumulate and rebound charges at the interfaces, and form a voltage output up to 1.7 V based on a solid‐liquid‐solid structure. Furthermore, through integrating series of water molecular generators, a voltage of 4.5 V can be achieved and effectively power commercial LED. This generator has been proven to harvest mechanical energy in the vertical direction to output DC power and excellent potential for applications in distributed energy supply.

Investigation of hydrated channels and proton pathways in a high-resolution cryo-EM structure of mammalian complex I.

Respiratory complex I, a key enzyme in mammalian metabolism, captures the energy released by reduction of ubiquinone by NADH to drive protons across the inner mitochondrial membrane, generating the proton-motive force for ATP synthesis. Despite remarkable advances in structural knowledge of this complicated membrane-bound enzyme, its mechanism of catalysis remains controversial. In particular, how ubiquinone reduction is coupled to proton pumping and the pathways and mechanisms of proton translocation are contested. We present a 2.4-Å resolution cryo-EM structure of complex I from mouse heart mitochondria in the closed, active (ready-to-go) resting state, with 2945 water molecules modeled. By analyzing the networks of charged and polar residues and water molecules present, we evaluate candidate pathways for proton transfer through the enzyme, for the chemical protons for ubiquinone reduction, and for the protons transported across the membrane. Last, we compare our data to the predictions of extant mechanistic models, and identify key questions to answer in future work to test them.

Study of Hexylamine Adsorption on Platinum by Chronoamperometric Method

The kinetics of the redox Fe2+/Fe3+ reaction on a platinum electrode in 1 M HClO4 was studied by the chronoamperometric method in the presence of the hexylamine surfactant. The main kinetic characteristics of the reaction have been estimated. The dependence of the exchange current density on the hexylamine concentration was analyzed. It was found that the hexylamine adsorption on platinum is described by the Dhar-Flory-Huggins isotherm. It is shown that the hexylamine adsorption on platinum is mainly due to the hydrophobic effect of the hexylamine molecules interaction with polar water molecules.

Molecular Dynamics Simulations on the Adsorbed Monolayers of N-Dodecyl Betaine at the Air-Water Interface.

Betaine is a kind of zwitterionic surfactant with both positive and negative charge groups on the polar head, showing good surface activity and aggregation behaviors. The interfacial adsorption, structures and properties of n-dodecyl betaine (NDB) at different surface coverages at the air-water interface are studied through molecular dynamics (MD) simulations. Interactions between the polar heads and water molecules, the distribution of water molecules around polar heads, the tilt angle of the NDB molecule, polar head and tail chain with respect to the surface normal, the conformations and lengths of the tail chain, and the interfacial thickness of the NDB monolayer are analyzed. The change of surface coverage hardly affects the locations and spatial distributions of the water molecules around the polar heads. As more NDB molecules are adsorbed at the air-water interface, the number of hydrogen bonds between polar heads and water molecules slightly decreases, while the lifetimes of hydrogen bonds become larger. With the increase in surface coverage, less gauche defects along the alkyl chain and longer NDB chain are obtained. The thickness of the NDB monolayer also increases. At large surface coverages, tilted angles of the polar head, tail chain and whole NDB molecule show little change with the increase in surface area. Surface coverages can change the tendency of polar heads and the tail chain for the surface normal.

Rigidity of dipolar coupled H2O molecular network in external electric field

We have performed the first study of the effect of an external electric field on the quantum paraelectric state of the electric dipolar lattice of polar water molecules confined within nano-sized cages of beryl crystal lattice. The complex dielectric permittivity ε* = ε'+iε" of a water subsystem in hydrous beryl is measured at frequencies 1 Hz-1 MHz in the temperature interval 10–300 K both in zero and 7 kV/cm external field. For comparison, we measure dielectric response of conventional quantum paraelectric KTaO3. In KTaO3, the application of electric field of several kV/cm suppresses quantum fluctuations and leads to a shallow maximum of ε′(T) around 15 K that could indicate a diffuse phase transition. In hydrous beryl, however, a bias electric field of up to 7 kV/cm has no effect on the dielectric response of the water molecules network. This result is confirmed by Monte Carlo simulations. We attribute the enhanced rigidity of the water dipolar subsystem to the strong long-range dipole-dipole interaction between separate H2O molecules. The field that could affect the polarization state of the dipoles is estimated to be of the order of 100 kV/cm.