Water Molecules Research Articles

Reconfiguring the Electrolyte Network Structure with Bio‐Inspired Cryoprotective Additive for Low‐Temperature Aqueous Zinc Batteries

AbstractDespite promising performance at ambient temperature, the development of aqueous zinc batteries is jeopardized by the freeze of aqueous electrolytes and deteriorative electrode‐electrolyte interphase at low temperatures. Herein, inspired by the cryoprotective mechanism of extracellular polysaccharides in biological organisms, a quaternized galactomannan polysaccharide (q‐GPA) is proposed as a cryoprotective additive for improving low‐temperature performance of aqueous zinc batteries. Mechanistic studies revealed that a multi‐hydroxyl galactomannan backbone can substantially attenuate the activity of water molecules through the reconfiguration of the hydrogen bond network, which inhibits ice crystal formation at subzero temperatures and thus depress the freezing point of the electrolyte. Meanwhile, the quaternary ammonium groups tethered on the q‐GPA skeleton are intended to neutralize the interfacial electric field through electrostatic repulsion, thereby accelerating Zn2+ deposition kinetics and prohibiting zinc dendrite growth. Impressively, the q‐GPA–modified electrolyte enables an extended lifespan of over 1700 h in Zn||Zn symmetric battery at a high current density of 3 mA cm−2 and an ultralong cycle life of 5000 cycles with a capacity retention of 99.2% in the Zn||Na2V6O16·1.5H2O (NVO) full battery at −30 °C. This work provides unprecedented possibilities for optimizing the electrolyte formulation of low‐temperature aqueous batteries.

Synthesis, structure, and mechanism of action of a unique mixed-ligand nickel (II)-complex of tetra-dentate phenol-based ligand with di-aquo co-ligands with significant pro-apoptotic and anti-metastatic effect against malignant human cancer cells

From the discovery of the anticancer activity of “cisplatin”, various type of numerous mononuclear platinum (II) complexes has been evaluated for antitumor activities, though therapeutic use is limited due to side effects and resistance. In this study, A unique mixed ligand mono nuclear octahedral Ni (II) complex [NiL(H2O)2].0·.5H2O (1) [H2L = N,Nʹ-dimethyl-N,Nʹ-bis (2-hydroxy-3,5-di methyl benzyl)-ethylenediamine] with tetra dentate phenol based ligand with N2O2 donor environment along with two labile water molecules was synthesised. The complex (1) is structurally characterized by spectroscopic tools including single-crystal X-ray diffractometer. Complex (1) crystallizes in monoclinic space group P21/n with a = 10.4871(17) Å, b = 20.860 (4) Å and c = 20.955(4) Å. The UV – visible spectra show two peaks around 507 nm and 367 nm due to spin-allowed 1A1g → 1A2g and 1A1g → 1B1g transitions respectively as expected for a square planar d8 system. Mixed ligand octahedral nickel (II) complex with facially coordinating tetra dentate phenol-based ligand (H2L) is in association with two water molecule as ancillary ligand. Two water molecules associated with coordination zone of nickel (II) centre is loosely bound. In this present study, we have evaluated the anti-cancer properties of Complex (1). We found that Complex (1) show potent cancer cell killing activity in case of poorly invasive mice and human cancer cell lines. Complex (1) trigger apoptosis chiefly via p53 dependent pathway. Complex (1) also inhibits cancer cell migration and epithelial to mesenchymal transition in case of metastatic breast cancer cells suggesting potent anti-cancer properties of complex (1).

Theoretical study on the mechanism of alcohol photooxidation on Nb2O5 surface.

Theoretical modeling of the solid-state photocatalysis is one of the important issues as various useful photocatalysts have been developed to date. In this work, we investigated the mechanism of the alcohol photooxidation on niobium oxide (Nb2O5) which was experimentally developed, using the density functional theory (DFT)/time-dependent (TD)DFT calculations based on the cluster model. The alcohol adsorption and the first hydrogen transfer from hydroxy group to surface occur in the ground state, while the second hydrogen transfer from CH proceeds in the excited states during the photoirradiation of UV or visible light. The spin crossing was identified and the low-lying triplet states were solved for the reaction pathway. The photoabsorption in the visible light region was characterized as the charge transfer transition from O 2p of alcohol to Nb 4d of the Nb2O5 surface. The spin density and the natural population analysis indicated the generation of spin density in the moiety of carbonyl compound and its dissipation to the interface of the surface, which partly explains the electron paramagnetic resonance measurement. It was confirmed that the rate determining step is the desorption of carbonyl compound and water molecule in agreement with the experimental rate equation analysis. The present findings with the theoretical modeling will provide useful information for the further studies of the solid-state photocatalysis.

Formation of hydrogen bonding network of methane sulfonic acid at low degree of hydration (MSA)m·(H2O)n (m = 1–2 and n = 1–5)

This study employs ab initio calculations based on density functional theory (DFT) to investigate the structural properties, 1H-NMR spectra, and vibrational spectra of methane sulfonic acid (MSA) at low degree of hydration. The findings reveal that energetically stable structures are formed by small clusters consisting of one or two MSA molecules (m = 1 and 2) and one or two water molecules in (MSA)m·(H2O)n (m = 1–2 and n = 1–5).These stable structures arise from the formation of strong cyclic hydrogen bonds between the proton of the hydroxyl (OH) group in MSA and the water molecules. However, clusters containing three or more water molecules (n > 2) exhibit proton transfer from MSA to water, resulting in the formation of ion-pairs composed of CH3SO3− and H3O+species. The measured 1H-NMR spectra demonstrate the presence of hydrogen-bonded interactions between MSA and water, with a single MSA molecule interacting with water molecules. This interaction model accurately represents the hydrogen bonding network, as supported by the agreement between the experimental and calculated NMR chemical shift results.

Mechanism of Peroxynitrite Interaction with Ferric M. tuberculosis Nitrobindin: A Computational Study.

Nitrobindins (Nbs) are all-β-barrel heme proteins present along the evolutionary ladder. They display a highly solvent-exposed ferric heme group with the iron atom being coordinated by the proximal His residue and a water molecule at the distal position. Ferric nitrobindins (Nb(III)) play a role in the conversion of toxic peroxynitrite (ONOO-) to harmless nitrate, with the value of the second-order rate constant being similar to those of most heme proteins. The value of the second-order rate constant of Nbs increases as the pH decreases; this suggests that Nb(III) preferentially reacts with peroxynitrous acid (ONOOH), although ONOO- is more nucleophilic. In this work, we shed light on the molecular basis of the ONOO- and ONOOH reactivity of ferric Mycobacterium tuberculosis Nb (Mt-Nb(III)) by dissecting the ligand migration toward the active site, the water molecule release, and the ligand binding process by computer simulations. Classical molecular dynamics simulations were performed by employing a steered molecular dynamics approach and the Jarzynski equality to obtain ligand migration free energy profiles for both ONOO- and ONOOH. Our results indicate that ONOO- and ONOOH migration is almost unhindered, consistent with the exposed metal center of Mt-Nb(III). To further analyze the ligand binding process, we computed potential energy profiles for the displacement of the Fe(III)-coordinated water molecule using a hybrid QM/MM scheme at the DFT level and a nudged elastic band approach. These results indicate that ONOO- exhibits a much larger barrier for ligand displacement than ONOOH, suggesting that water displacement is assisted by protonation of the leaving group by the incoming ONOOH.

Influence of IDS and SDS compound ratio on pore structure and wettability of bituminous coal and anthracite: Experimental and simulation discussion

The pore and wetting characteristics of bituminous coal and anthracite treated with different proportions of tetrasodium iminodisuccinate (IDS) and sodium dodecyl sulfate (SDS) were measured. The pore structure characteristics of the coal were studied via low-temperature nitrogen adsorption analysis and the Frenkel-Halsey-Hill fractal theory. Zeta potential measurements were conducted to quantitatively analyze the degree of aggregation or dispersion of coal particles dissolved in solution. Changes in the coal surface morphology were observed and analyzed by scanning electron microscopy (SEM). The results show that when the ratio of IDS:SDS is 1:3, the specific surface area (SSA) values of bituminous coal and anthracite are the lowest. The composite reagent has a greater effect on improving the pore structure of anthracite than bituminous coal. Compared with bituminous coal, anthracite has better pore connectivity and a wider pore network. The absolute zeta potentials of bituminous coal and anthracite reach the maximum at an IDS:SDS ratio of 1:3, with values of 91.08 mV and 91.35 mV, respectively. The electrostatic potential distributions of the molecules show that the advantages of the electrostatic potential difference with water molecules enable IDS and SDS molecules to effectively attract water molecules and form hydrogen bonds, thus revealing the optimization mechanism of coal wettability.

Terahertz Spectroscopy Unambiguously Determines the Orientation of Guest Water Molecules in a Structurally Elusive Metal-Organic Framework.

Porous materials, particularly metal-organic frameworks (MOFs), hold great promise for advanced applications. MIL-53(Al) is an exceptionally well-studied MOF that exhibits a phase transition upon guest capture─in this case, water─resulting in a dramatic change in the pore volume. Despite extensive studies, the structure of the water-loaded narrow-pore phase, MIL-53(Al)-np, remains controversial, particularly with respect to the positions of the adsorbed water molecules. We use terahertz spectroscopy, coupled with powder X-ray diffraction and density functional theory simulations, to unambiguously resolve this controversy. We show that the low-frequency (<100 cm-1) vibrational spectrum depends on weak long-range forces that are extremely sensitive to the orientation of the adsorbed water molecules. This enables definitively determining the correct structure of MIL-53(Al)-np while highlighting the extreme sensitivity of terahertz spectroscopy to bulk structure, suggesting its potential as a robust complement to X-ray diffraction for precise characterization of host-guest complexes.

Theory-based cryopreservation mode of mesenchymal stromal cell spheroids

Cryopreservation of spheroids requires development of new improved methods. The plasma membranes permeability coefficients for water and cryoprotectants determine time characteristics of mass transfer through the cell membranes, and therefore the optimal modes of cells cryopreservation. Here we proposed an approach to cryopreservation of multicellular spheroids which considers their generalised characteristics as analogues of the membranes' permeability coefficients of the individual cells. We have determined such integral characteristics of spheroids from mesenchymal stromal cells (MSCs) as osmotically inactive volume; permeability coefficients for water and Me2SO molecules and the activation energy of their penetration. Based on these characteristics, we calculated the osmotic behaviour of multicellular spheroids under cooling conditions to select the optimal cooling rate. We also determined the optimal cooling rate of spheroids using the probabilistic model developed based on the two-factor theory of cryodamage. From the calculation it follows that the optimal cooling rate of the MSC-based spheroids is 0.75 °С/min. To verify the obtained theoretical estimates, we conducted experiments on freezing MSC-based spheroids under different modes. The obtained results of primary viability screening indicate that freezing at a constant linear cooling rate of 0.75 - 1.0 °С/min gives a good result. Theoretical prediction of the spheroid osmotic behaviour during cooling provided the basis for experimental verification of varying the temperature to which slow cooling should be carried out before immersion in liquid nitrogen. Slow freezing of spheroids to -40 °C followed by immersion in liquid nitrogen was shown to preserve cells better than slow freezing to -80 °C. Obtained data allow more effective use of MSC-based spheroids in drug screening and regenerative medicine.

Promoting Electrochemical CO2 Reduction to Formate via Sulfur‐Assisted Electrolysis

AbstractElectrochemical CO2 reduction reaction (CO2RR) provides a renewable approach to transform CO2 to produce chemicals and fuels. Unfortunately, it faces the challenges of sluggish CO2 activation and slow water dissociation. This study reports the modification of Bi‐based electrocatalyst by S, which leads to a remarkable enhancement in activity and selectivity during electrochemical CO2 reduction to formate. Based on comprehensive in situ examinations and kinetic evaluations, it is observed that the presence of S species over Bi catalyst can significantly enhance its interaction with K+(H2O)n, facilitating fast dissociation of water molecules to generate protons. Further in situ attenuated total reflectance surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) and in situ Raman spectroscopy measurements reveal that S modification is able to decrease the oxidation state of Bi active site, which can effectively enhance CO2 activation and facilitate HCOO* intermediate formation while suppressing competing hydrogen evolution reaction. Consequently, the S‐modified Bi catalyst achieves impressive electrochemical CO2RR performance, reaching a formate Faradaic efficiency (FEformate) of 91.2% at a formate partial current density of ≈135 mA cm−2 and a potential of −0.8 V versus RHE in an alkaline electrolyte.

Ultrafast hydrogen production in boron/oxygen-codoped graphitic carbon nitride revealed by nonadiabatic dynamics simulations.

Graphitic carbon nitride (g-C3N4 or GCN) shows promise in photocatalytic water splitting, despite facing the challenge of rapid electron-hole recombination. In this study, we investigated the influence of boron/oxygen codoping on the photocatalytic performance of GCN systems for hydrogen generation. First-principles calculations and nonadiabatic molecular dynamics (NAMD) simulations were employed to reveal that the recombination time of photogenerated carriers could be increased by 16% to 64% in the codoped systems compared to the pristine GCN. The time-dependent density functional theory (TDDFT) scheme was utilized to select energy windows and initiate dynamics in cluster models of B/O co-doped heptazine with water molecules. Notably, we observed efficient direct photodissociation of hydrogen atoms from water molecules within 60 fs and proton hops within the hydrogen-bonded network within 80 fs in the co-doped system, diverging from the previously proposed mechanism for pristine heptazine in NAMD simulations. This discovery underscores the significant role of faster proton-coupled electron transfer (PCET) reactions and rapid radiationless relaxation in achieving high photocatalytic efficiency in water splitting. Our work enhances the understanding of the internal mechanism of highly efficient photocatalysts for water splitting and provides a new design strategy for doped GCN.

Balancing the Binding of Intermediates Enhances Alkaline Hydrogen Oxidation on D-Band Center Modulated Pd Sites.

Exploring efficient alkaline hydrogen oxidation reaction (HOR) electrocatalysts is of great concern for constructing anion exchange membrane fuel cells (AEMFCs). Herein, d-band center modulated PdCo alloys with ultralow Pd content anchored onto the defective carbon support (abbreviated as PdCo/NC hereafter) are proposed as highly efficient HOR catalyst. The as-prepared catalyst exhibits exceptional HOR performance compared to the Pt/C catalyst, achieving thermodynamically spontaneous and kinetically preferential reactions. Specifically, the resultant PdCo/NC demonstrates a marked enhancement in alkaline HOR performance, with the highest mass and specific activities of 1919.6 mA mgPd-1 and 1.9 mA cm-2, 51.1 and 4.2 times higher than those of benchmark of Pt/C, along with an excellent stability in a chronoamperometry test. In the analysis of in situ Raman spectra, it was discovered that tetrahedrally coordinated H-bonded water molecules were formed during the HOR process. This indicates that the promotion of interfacial water molecule formation and enhancement of HOR activities in PdCo/NC are facilitated by defect engineering and the turning of d-band center in PdCo alloy. The essential knowledge obtained in this study could open up a new direction for modifying the electronic structure of cost-effective HOR catalysts through electronic structure engineering.

Encapsulation of charged halogens by the 512 water cage.

This study focuses on the encapsulation of the entire series of halides by the 512 cage of twenty water molecules and on the characterization of water to water and water to anion interactions. State-of-the-art computations are used to determine equilibrium geometries, energy related quantities, and thermal stability towards dissociation and to dissect the nature and strength of intermolecular interactions holding the clusters as stable units. Two types of structures are revealed: heavily deformed cages for F- indicating a preference for microsolvation, and slightly deformed cages for the remaining anions indicating a preference for encapsulation. The primary variable dictating the properties of the clusters is the charge density of the central halide, with the most severe effects observed for the F- case. For the remaining halides, the anion may be safely viewed as a sort of "big electron" with little local disruptive power, enough to affect the network of non-covalent hydrogen bonds in the cage, but not enough to break it. Gibbs energies for dissociation either into cavity and halide or into water molecules and halide suggest that, in a similar way as to methane clathrate, a more weakly bonded complex that has been detected in the gas phase, all halide containing clathrate-like structures should be amenable to experimental detection in the gas phase at moderate temperature and pressure conditions.

The influence of doping with different surface modified SiO2 nanoparticles on the dielectric properties of natural ester insulating oil

Nanoparticles are presently considered to be high-potential filler materials in insulation medium. Surface-modified nanoparticles can not only improve the compatibility between nanoparticles and insulation liquid but also enhance the dielectric properties. Herein, models of soybean oil-based natural ester insulation oil doped with two silane coupling agents (A151, KH550) modified SiO2 were established, respectively. Molecular dynamics and DFT first principles were applied to explore the effect of two nanoparticles on the dielectric properties of liquid-insulation medium. The results showed that two types of nanoparticles can restrict the diffusion of water molecules by forming hydrogen bonds, while the number of hydrogen bonds in KH550–SiO2 is one-third more than that in A151-SiO2, and the interaction energy is lower, demonstrating a stronger adsorption effect on water molecules. Moreover, surface electrostatic potential and frontier molecular orbitals showed that KH550–SiO2 have a higher adsorption on charged particles in natural ester insulation oil, which can further inhibit the development of streamer discharge in the liquid insulation medium, improve its dielectric property and delay the aging and deterioration of natural ester insulation oil. This study extends our knowledge into the influence of silane coupling agents modified SiO2 nanoparticles on the dielectric performance of liquid insulation materials from a microscopic perspective.

Unraveling the Hydration Shell Structure and Dynamics of Group 10 Aqua Ions.

We present ab initio simulations based on subsystem DFT of group 10 aqua ions accurately compared against experimental data on hydration structure. Our simulations provide insights into the molecular structures and dynamics of hydration shells, offering recalibrated interpretations of experimental results. We observe a soft, but distinct second hydration shell in Palladium (Pd) due to a balance between thermal fluctuations, metal-water interactions, and hydrogen bonding. Nickel (Ni) and platinum (Pt) exhibit more rigid hydration shells. Notably, our simulations align with experimental findings for Pd, showing axial hydration marked by a broad peak at about 3 Å in the Pd-O radial distribution function, revising the previously sharp "mesoshell" prediction. We introduce the "hydrogen bond dome" concept to describe a resilient network of hydrogen-bonded water molecules around the metal, which plays a critical role in the axial hydration dynamics.

When Tautomers Matter: UV-Vis Absorption Spectra of Hypoxanthine in Aqueous Solution from Fully Atomistic Simulations.

The UV-Vis spectrum of the solvated purine derivative Hypoxanthine (HYX) is investigated using the Quantum Mechanics/Fluctuating Charges (QM/FQ) multiscale approach combined with a sampling of configurations through atomistic Molecular Dynamics (MD) simulations. Keto 1H7H and 1H9H tautomeric forms of HYX are the most stable in aqueous solution and form different stable complexes with the surrounding water molecules, ultimately affecting the electronic absorption spectra. The final simulated spectrum resulting from the combination of the individual spectra of tautomers agrees very well with most of the characteristics in the measured spectrum. The importance of considering the effect of the solute tautomers and, in parallel, the contribution of the different solvent arrangements around the solute when modeling spectral properties, is highlighted. In addition, the high quality of the computed spectra leads to suggesting an alternative way for acquiring tautomeric populations from combined computational/experimental spectra.

Room-Temperature Superprotonic Conductivity beyond 10-1 S cm-1 in a Co(II) Coordination Polymer.

An efficient design of crystalline solid-state proton conductors (SSPCs) is crucial for the progress of clean energy applications. Developing such materials to make them work at room temperature with a conductivity of ≥10-1 S cm-1 is of significant interest in terms of technical and commercial aspects. Utilizing the recently highlighted "coordinated-water-driven proton conduction" approach, herein, we have rationally synthesized two highly stable and scalable 1D Co(II) coordination polymers (CPs) as SSPCs, PCM-2 {[Co(bpy)(H2O)2(NO3)2]·H2O}n and PCM-3 {[Co2(bpy)2(SO4)2(H2O)6].4H2O}n, with distinct alignments in coordinated water and coordinated oxo-anions (nitrate and sulfate, respectively). The acidity of the metal-bound water molecules in PCM-2 is further enhanced through cooperative long-range continuous H bonds with coordinated Brønsted basic nitrates (proton acceptors), leading to ultrahigh superprotonic conductivities even at 25 °C (1.03 × 10-1 S cm-1 under 95% RH), and reached a maximum of 2.99 × 10-1 S cm-1 at 85 °C (95% RH). The conductivity at 25 °C is even higher than that of commercial Nafion 117 (6.74 × 10-2 S cm-1 at 100% RH). The absence of such an H-bonding interaction in PCM-3 (closed loops) resulted in a lesser conductivity of 5.87 × 10-5 S cm-1 (95% RH, 85 °C). PCM-2 represents the first example of SSPC exhibiting conductivity in the order 10-1 S cm-1 at ambient temperature (25 °C) with excellent recyclability.

Water‐Assisted Reprocessing and Shape Programming of Epoxy Vitrimer

Water‐Assisted Reprocessing and Shape Programming of Epoxy Vitrimer

Experiments and Molecular Simulations to Study the Effect of Surface-Active Compounds in Mixtures of Model Oils on CO2 Corrosion during Intermittent Oil-Water Wetting.

Intermittent oil-water wetting can have a significant effect on the internal corrosion of steel pipelines. This paper presents a combined experimental and molecular modeling study of several influential factors on the surface properties and corrosion behavior of mild steel in CO2 environments. The influence of different model oils (LVT-200 and Aromatic-200) and select surface-active compounds (myristic acid, cyclohexane butyric acid, and oleic acid) on the corrosion behavior of carbon steel during intermittent oil-water wetting was determined by measuring the corrosion rate after intermittent wetting cycles. The interfacial tension measurements were performed to study the incorporation of the oil phase along with surface-active molecules in the protective layer formed on the specimen surface. Results showed that the interfacial tension for an aromatic oil-water interface is lower than that for an aliphatic oil-water interface. To understand this result, molecular dynamics simulations of oil-water interfaces were performed in the presence of surface-active molecules and different oils to analyze the structure of the layer formed at the interface. The simulations supported the hypothesis that aromatic molecules are less structured at the interface, which results in the incorporation of more water molecules into the protective layer formed at the steel surface, causing a higher corrosion rate. On the other hand, the simulations revealed that myristic acid in an aliphatic oil forms a well-aligned structure at the interface, devoid of any water molecules. This is in agreement with the hypothesis that the linear molecular structure of myristic acid favors the alignment of molecules at an aliphatic oil-water interface, resulting in a lower interfacial tension and more effective corrosion mitigation as compared to the other two nonlinear compounds tested. It is concluded that an important factor controlling the corrosion behavior is the molecular structure of the oil-water interface, which is adopted by the steel surface layer through the Langmuir-Blodgett process.

Laboratory exploration of a novel method to protect silicate relics against salt efflorescence by directional induction of water

Salt efflorescence is one of the critical problems for the preservation of immovable silicate relics. Salt efflorescence mainly comes from continuous cycles of crystallization/dissolution or hydration/dehydration of salts in confined pores in silicate relics. Many protocols have been developed in attempts to alleviate possible salt damages with minor success because of endless water and salt feed from underground. In this study, we propose and design a novel technique for salt damage prevention and protection of immovable relics. Materials with higher water-absorbing ability than matrix are applied to control the water and salt migration direction in simulated sand samples. The distribution of moisture content on the surface of sand is followed by hyperspectral imaging. It appears that water and salt molecules will preferentially transport towards positions containing higher water-absorbing material. Both organic and inorganic high water-absorbing materials show effective in controlling the water and salt migration direction, which provides a new approach for the prevention and protection of salt efflorescence in silicate cultural relics.

The β-subunit of tryptophan synthase is a latent tyrosine synthase.

Aromatic amino acids and their derivatives are diverse primary and secondary metabolites with critical roles in protein synthesis, cell structure and integrity, defense and signaling. All de novo aromatic amino acid production relies on a set of ancient and highly conserved chemistries. Here we introduce a new enzymatic transformation for L-tyrosine synthesis by demonstrating that the β-subunit of tryptophan synthase-which natively couples indole and L-serine to form L-tryptophan-can act as a latent 'tyrosine synthase'. A single substitution of a near-universally conserved catalytic residue unlocks activity toward simple phenol analogs and yields exclusive para carbon-carbon bond formation to furnish L-tyrosines. Structural and mechanistic studies show how a new active-site water molecule orients phenols for a nonnative mechanism of alkylation, with additional directed evolution resulting in a net >30,000-fold rate enhancement. This new biocatalyst can be used to efficiently prepare valuable L-tyrosine analogs at gram scales and provides the missing chemistry for a conceptually different pathway to L-tyrosine.