Hydration Layer Research Articles

Investigating Anion Effects on Metal Ion Binding Interactions With Amyloid β Peptide by Ion Mobility Mass Spectrometry.

The study of metal ion's role in the biological processes of Alzheimer's disease has spurred investigations into the coordination chemistry of amyloid beta peptide and its fragments. Nano-electrospray ionization mass spectrometry (nESI-MS) has been utilized to examine the stabilization of bound anions on multiprotein complexes without bulk solvent. However, the effects of anions on metal ion binding interactions with amyloid beta peptide have not been explored. This study directly examined metal-peptide complexes using nESI-MS and investigated the effects of various anions on the binding ratio and stability of these complexes from ammonium salt solutions. The results indicate that different anions have distinct effects on the binding ratio and stability of various metal-peptide complexes. Of these, the bicarbonate ion exhibits the highest binding ratios for metal-peptide complexes, while binding ratios for these complexes in phosphate are comparatively low. Our results suggest that acetate, formate, bicarbonate, and phosphate have weak affinities and act as weak stabilizers of the metal-peptide complex structure in the gas phase. Intriguingly, chloride and sulfate act as stabilizers of the metal-peptide complex in the gas phase. The rank order determined from these data is substantially different from the Hofmeister salt series in solution. Although this outcome was anticipated due to the reduced influence of anions and water solvation, our findings correlate well with expected anion binding in solution and emphasize the importance of both hydration layer and anion-metal-peptide binding effects for Hofmeister-type stabilization in solution. This approach proved useful in examining the interactions between metal ions and amyloid beta peptide, which are relevant to Alzheimer's disease, using direct ESI-MS.

Protein Nanospheres and Nanofibers Prepared by Ice-Templating for the Controlled Release of Hydrophobic Drugs.

Protein scaffolds play a vital role in drug delivery systems. However, few research studies have been focused on loading hydrophobic drugs on protein scaffolds in biomedical fields. Here, we report on the development of protein microspheres and nanofibers by a simple ice-templating approach and their use as scaffolds for the controlled release of hydrophobic drugs, with bovine serum albumin (BSA) as the model protein and curcumin as the model hydrophobic drug. The BSA scaffolds display the unique nanofibrous and microspherical structures. This is a surprising discovery because there has been no report on the formation of microspheres via simple ice-templating of solutions or suspensions. To further understand the formation of microspheres by this approach, lysozyme, papain, and their composites with BSA are also studied. It is speculated that nanoparticles are first formed in aqueous BSA solution, attributed to the overlapping of hydration layers and autoassembly of inner hydrophobic cores of BSA globular molecules. Nanoprecipitation and soaking evaporation approaches are then used to load curcumin into the BSA scaffolds, followed by cross-linking with glutaraldehyde vapor to improve stability in an aqueous medium. The controlled release of curcumin is demonstrated, paving the way for various hydrophobic drugs loaded into this biodegradable and nonimmunogenic protein scaffold for potential treatments of diverse diseases.

Integrating strategy to investigate the formation and stabilization mechanisms of Curcumin-Cyclodextrin inclusion complexes: experimental characterizations and multi-scale computational simulations.

The Cyclodextrin (CD) encapsulation technology can significantly enhance the water solubility of Curcumin (CUR) and effectively protect it against chemical degradations. In the current study, a combination of experimental and multi-scale computational approaches was used to investigate the binding mechanism between CUR and β-CDs (β-CD, 2-HP-β-CD, Me-β-CD, and DM-β-CD). Phase solubility studies showed that β-CDs exhibited a strong binding affinity with CUR and significantly enhanced its solubility. SEM, PXRD, DSC, and TG analysis confirmed the formation of inclusion complexes, resulting in the transition of CUR from crystalline to an amorphous state. FTIR, 1H, and 13CNMR spectra deduced that CUR may have multiple binding conformations with β-CDs. The rationality of molecular dynamics simulation systems was confirmed by comparing the simulated IR spectrum from quantum mechanics with the experimental IR spectrum. MM-PBSA and umbrella sampling simulation calculated the binding free energy of the CUR/CD inclusion complexes, ranking Me-β-CD > DM-β-CD > 2-HP-β-CD > β-CD, and clarified that van der Waals interaction played a major role in stabilizing the inclusion complexes. RDF analysis confirmed that the release of high-energy water molecules drove the formation of the CUR/CD inclusion complex, and the β-CD substituents affected their exterior hydration layer. Additionally, principal component analysis (PCA) and non-covalent interaction analysis revealed three CUR/CD binding modes: bead-on-string, terminal insertion, and V-shaped-folding. The research strategy adopted here can serve as a paradigm for investigating the encapsulation mechanism of poorly soluble drugs with CDs.

Innovative temperature-responsive membrane with an elastic interface for biofouling mitigation in industrial circulating cooling water treatment

To address the issues of scaling caused by heat and water evaporation in regard to circulating cooling water (CCW), TFC membrane filtration systems have been increasingly considered for terminal treatment processes because of their excellent separation performance. However, membrane biofouling phenomenon significantly hinders the widespread utilization of TFC membranes. In this study, to harness the thermal phenomenon of CCW and establish a stable and durable multifunctional antibiofouling layer, temperature-responsive Pnipam and the spectral antibacterial agent Ag were organically incorporated into commercially available TFC membranes. Biological experimental findings demonstrated that above the lower critical solution temperature (LCST), the contraction of Pnipam molecular chains facilitated the inactivation of bacteria by the antibacterial agent, resulting in an impressive sterilization efficiency of up to 99 %. XDLVO analysis revealed that below the LCST, the establishment of a hydration layer on the functional interface resulted in the creation of elevated energy barriers, effectively impeding bacterial adhesion to the membrane surface. Consequently, a high bacterial release rate of 98.4 % was achieved on the low-temperature surface. The alterations in the functional membrane surface conformation induced by temperature variations further amplified the separation between the pollutants and the membrane, creating an enhanced "elastic interface." This efficient and straightforward cleaning procedure mitigated the formation of irreversible fouling without compromising the integrity of the membrane surface. This study presents a deliberately engineered thermoresponsive antibiofouling membrane interface to address the issue of membrane fouling in membrane-based CCW treatment systems while shedding new light on the mechanisms of "inactivation" and "defense."

Nickel-cobalt hydrogen phosphate membrane with outstanding anti-crude oil-fouling capability and its microscopic anti-fouling mechanism

Oil/water separation membranes with superior anti-fouling properties against highly viscous oils are crucial for the efficient treatment of oily wastewater. Herein, the effects of functional groups in an inorganic superhydrophilic membrane on the anti-fouling properties of the membrane are investigated. Using a facile one-step electrochemical deposition method, Ni1-xCoxHPO4·3H2O membranes were formed on a Cu(OH)2 microneedle-coated copper mesh (CCNC–P) with superhydrophilic and underwater superoleophobic properties. All CCNC–P membranes with different Co2+ contents showed outstanding anti-fouling capability for oily wastewater such as those containing crude oil. The CCNC–P(x = 0.5) membrane exhibited high separation efficiency reaching 99.7 % across five oil–water mixtures and oil-in-water emulsions, concurrently presenting an ultrahigh flux of 61695 L m−2 h−1 for crude oil–water mixture. Moreover, the membrane consistently maintained its separation performance during the long-term crude oil–water separation process. The flux decline ratio was below 1 %, and the flux recovery ratio approached 99.4 %. The CCNC–P membranes possessed superior chemical, thermal, and mechanical stability, suggesting significant potential for the industrial treatment of oily wastewater. Density functional theory calculation revealed that the HPO42− group in CCNC–P can strongly adsorb water molecules. The resultant stabilized hydration layer impeded the contact between the membrane surface and oil droplets, while the metal ions scarcely influenced the adsorption of water molecules on CCNC–P. These findings provide new insights into the development of novel oil–water separation membranes with higher anti-fouling capabilities against high-viscosity oils.

Improving multifunctional properties of the polyvinylidene fluoride (PVDF) membrane with crosslinked dialdehyde-starch (DAS) and polyethyleneimine (PEI) coating

Dialdehyde-soluble starch (DAS) and polyethyleneimine (PEI) were used to coat the polyvinylidene fluoride (PVDF) membrane for improving its antifouling and multifunctional properties through a combination of dip-coating and spray-coating techniques. The resulting membrane demonstrated excellent hydrophilicity and underwater oleophobicity due to hydrophilic DAS and PEI on its surface. The membrane achieved an impressive oil removal rate of 99.8 % and a flux 1420.8 ± 26.5 L·m−2·h−1 when it was used for oil-water emulsion separation. The hydration layer formed by the DAS and PEI greatly enhanced the membrane antifouling property, and its flux recovery rate was up to 96.6 % in BSA filtration experiments. The positive charge PEI and the negative charge DAS contributed to high separation efficiency of 99.1 % for the anion dye MO with the membrane D10P20, and high separation efficiency of 88.3 % for the cation dye RhB with the membrane P5D20. In addition, the coating layer was stable due to the cross-linked DAS and PEI. This research contributes greatly to the preparation of antifouling and multifunctional membrane using environmentally friendly material including polysaccharide derivatives and water soluble polymer.

Effect of particle size, water saturation, inorganic salt and methane on the phase equilibrium of CO2 hydrates in sediments

Understanding the thermal stability of gas hydrate in complex marine geological environment is of importance to hydrate-based carbon sequestration. In this work, the factors affecting the equilibrium of CO2 hydrate in ocean sediments, including quartz sands, inorganic salts and gas impurities were quantitatively measured in a temperature range from 273 to 283 K and a phase equilibrium model of hydrate was established. To reveal the distribution in pore structure, the micro-morphologies of hydrate-bearing sediments were measured by cryo-SEM. Results showed that reduction of initial water saturation, addition of NaCl and CH4 were found to have inhibitory effect on CO2 hydrate equilibrium. Initial water saturation reduced the equilibrium temperature by the capillary pressure, but only 0.3–0.7 K temperature depression was observed as the water saturation reduced to 5 %. About 5.7 K in the average temperature depression was found by the addition of 10 wt% NaCl and 24 mol% CH4. NaCl and CH4 influenced the hydrate equilibrium by changing the water activity and chemical potential of hydrate water lattice. SEM images showed that the hydrate formed in pores of quartz sand had porous surface and coated the sand particles like a layer of cells which are 5–20 μm in diameter, suggesting the hydrate layer exists between the liquid and gas phase. Based on the van der Waals-Platteeuw model, a hydrate equilibrium model was developed. The model provided a good prediction of the hydrate equilibrium in the presence of quartz sand, NaCl and CH4 with an averaged deviation of ±4.2 %, which had the potential to be applicated in more complexed ocean sedimentary environment.

Advanced absorption-storage water molecules strategy reinforces antifouling property for stable oil/water emulsions separation

Constructing membranes with extraordinary resistance to oil contamination under high permeation flux is a considerable challenge. Herein, an advanced absorption-storage water molecules strategy is proposed for constructing the robust hydration layers to achieve effective anti-oil fouling and stable oily wastewater purification. Specifically, metal–organic framework (MOF, UiO-66-NH2) nanoparticles with powerful water-absorbing characteristics are preferentially adsorbed to collect water in oil/surfactant/water systems. Combining excellent water retention, the micro-/ nano-networks formed by attapulgite (APT) could store the water molecules captured by MOF. The synergistic effect of the water-absorbing/water-retaining interactions between the MOF and APT created robust hydration layers defense barriers, which enhanced the resistance of membrane to oil contamination. Furthermore, the abundant hydrophilic groups (e.g., –OH, –NH2 and –CONH2) of chitosan (CS) further improved the membrane surface hydrophilic coverage, permeability and hydration ability. As a result, the developed CS/APT@MOF composite membrane exhibited significant anti-oil fouling capability and realized superior purification property towards various oil-in-water emulsions stabilized by surfactants. The CS/APT@MOF composite membrane demonstrated outstanding oil repellency (flux recovery ratio > 99.6 %, total flux decline ratio < 3.8 %) over 10 cycles under large permeability (>660 L m-2h−1 bar−1). Meanwhile, the constructed CS/APT@MOF composite membrane exhibited stable separation cycle capability (10 cycles) and continuous purification performance (60 min) for different oil/water emulsions. Therefore, this advanced strategy based on absorption-storage water molecules to construct robust hydration layers provides a promising insight for the development of superior antifouling and operationally stable oil/water emulsions separation membranes.

Long-chain alkyl emulsifiers induced asphalt particle dispersion: Lipophilicity-enhancement effect

The structure of the lipophilic groups within the emulsifiers plays a pivotal role in uniformly dispersing the asphalt particles in the water regarding the storage and thermal stability of emulsified asphalt. This study combines laboratory experiments with molecular dynamics simulations, investigating the influence of alkyl chain length on emulsified asphalt dispersion and behavior at the oil/water interface. The results reveal that long-chain alkyl emulsifiers (C16TAC and C18TAC) present a lipophilicity-enhancement effect. This phenomenon increases the free volume fraction of emulsified asphalt, reducing viscosity and improving the compatibility of emulsion. This results in smaller asphalt particle sizes (D50 = 1.982μm) and more uniform dispersion. Vigorously lipophilic long-chain alkyl promotes emulsifier molecular migration towards the asphalt phase, thickening the oil/water interfacial layer and reducing interfacial tension and energy by more than 90 %. Notely, long-chain alkyl emulsifiers establish strong hydrogen bonds with water molecules, leading to water molecule aggregation into a hydration layer. Laboratory experimental results demonstrate that this lipophilicity-enhancement effect significantly improves the storage and thermal stability of emulsified asphalt. This research recommends long-chain alkyl emulsifiers in developing and designing energy-efficient pavement engineering regarding high-performance emulsified asphalt.

Fabrication of charged and zwitterionic nanofiltration membranes and anti-adhesion analysis using quartz crystal microbalance with dissipation and atomic force microscopy

Three nanofiltration (NF) membranes (positive charge, negative charge and near charge neutrality) were fabricated to investigate the anti-adhesion mechanism. Among them, the NF membrane with positive charge was synthesized through an electrophilic substitution reaction between the amino group of polyethyleneimine (PEI) and the chloromethyl groups of chloromethyl polysulfone (CMPSf) on a supporting polysulfone (PSf)/CMPSf blend membrane. The NF membrane with negative charge was fabricated through polycondensation using 1, 3, 5-benzenetricarbonyl trichloride (TMC) as a reactive monomer on the positive charge NF membrane. Subsequently, the near charge neutral zwitterion NF membrane (ZNF) was prepared by grafting 3-((2-aminoethyl) dimethylammonio) propane-1-sulfonate (sulfobetaine) (ADSS) onto the negative charge NF membrane. The anti-adhesion behaviors of the NF membranes during the dye selective separation were analyzed by Atomic force microscopy (AFM) and quartz crystal microbalance with dissipation (QCM-D). The results demonstrated that the near charge neutral ZNF membrane displayed a higher dyes rejection (>94.4 %) and higher flux recovery rates (>88.1 %) than charged NF membranes. Meanwhile, the near charge neutral ZNF membrane demonstrated the lowest amounts of dye deposition compared with charged NF membranes, such as reactive blue 4 (R4) for 509.9 ng/cm2, basic blue 24 (BB 24) for 269.0 ng/cm2, rhodamine B (RB) for 197.4 ng/cm2). Additionally, the near charge neutral ZNF membrane with the thicker hydration layer (121.7 nm) displayed weaker interaction forces (−4.8 nN to −7.4 nN) with the dyes than the charged membranes (−10.4 nN to −28.6 nN). Finally, an anti-adhesion mechanism involved charged shielding effect and hydration layer formation was proposed. These observations provide comprehensive insights into the anti-adhesion mechanism of ZNF membrane.

Design and fabrication of high-performance ultrafiltration membranes for low-temperature conditions

The influence of cold weather conditions on ultrafiltration (UF) membrane performance is noteworthy. Investigating alterations in UF membrane fouling behavior under low-temperature conditions and developing strategies to enhance their performance holds significant importance for advancing membrane separation technology in cold regions. We initiate an exploration into how low-temperature conditions impact the permeation and separation capabilities of unmodified PES UF membranes, concurrently scrutinizing the associated influencing mechanisms. Employing molecular design, we strategically incorporate hydrophilic carboxyl-functionalized groups into the molecular structure of poly (aryl ether sulfone) materials. This method facilitates the development of a series of PAES-modified UF membranes (LTM-x%), exhibiting exceptional performance in low-temperature conditions, grounded in the principles of the hydration layer theory. In a low-temperature condition (5±1 °C), the BSA solution flux and SA solution flux of the LTM-80 membrane surpass the pristine PES membrane flux by 187.38 % and 171.82 %, respectively. Notably, compared to the solution flux at room temperature (22±1 °C), the LTM-80 membrane shows only a slight decrease in the 5±1 °C temperature (flux decline rates of 18.52 % for BSA solution and 15.12 % for SA solution), in contrast to the pronounced decline observed in the pristine PES membrane (49.24 % for BSA and 47.67 % for SA). This investigation unveils an effective and viable strategy for designing and developing high-performance UF membranes suitable for cold regions.

Multifunctional membranes with super-wetting interface and in-situ Fenton-like sites for efficient oil-in-water emulsion separation

The surge in oil-in-water (O/W) emulsions poses a threat to the ecological environment. Membrane separation technology can achieve complete O/W emulsion separation through size sieving; however, its efficiency is limited by membrane fouling. In this study, an efficient O/W separation membrane with passive and positive anti-fouling properties was fabricated using Fe3O4 functionalized attapulgite (ATP) nanofibers. The anti-fouling mechanism of the multifunctional membranes for the separation of various O/W emulsions was studied. During separation process, a hydration layer, which mitigates oil adhesion with binding energy as low as −169 kcal·mol−1, forms on the interface of Fe3O4-ATP. When a cationic surfactant is present, positively charged oil droplets are attracted to the membrane surface, where they compress against each other, leading to demulsification and escape. Synergistic effects including electrostatic shielding, interaction energy, and steric hindrance were demonstrated through characterization and simulation. Our findings showed that the membrane exhibited a high filtration efficiency with an oil rejection of over 99 % and a steady flux of over 73 % of its initial value. After filtration, oil fouling degraded into smaller sizes and escaped from the membrane structure through the Fenton-like catalytic function of Fe3O4, resulting in a flux recovery ratio of up to 90 %. This study provides a reference for the construction of multifunctional membranes for efficient separation processes and advancing anti-fouling research on membrane interfaces.

Effect of Surface Charges in Polymer Coatings on Antifouling Performance in Marine Environments with Sediment.

The antifouling efficacy of hydrophilic polymer coatings is closely related to their surface charge. Many biological foulants such as mammalian cells and marine microalgae possess a negative surface charge, discouraging the use of positively charged polymer coatings for antifouling purposes. Instead, electrically neutral yet hydrophilic polymers have been widely employed, leveraging hydration layers to create a barrier against fouling. However, challenges arise in marine environments where both living marine organisms and sediments can adhere to solid surfaces, rendering previous findings less directly applicable. This study investigates the impact of a polymer coating surface charge on marine antifouling properties. Polymer brushes with various charges are applied to solid substrates, and the adhesion behavior of marine diatoms is assessed under both marine sediment-free and marine sediment conditions. The results underscore the effectiveness of negatively charged polymer brush coatings in marine antifouling, regardless of sediment presence.

Coral-inspired fabrication of Ag-Cu2O-zwitterionic polymers-phosphor films with day and night antifouling properties

Inspired by the antifouling process observed in fluorescent corals, this study introduces a novel functional antifouling film consisting of Ag-Cu2O nanocomposites, zwitterionic polymers, and a phosphor substrate. Zwitterionic polymers serve as a dispersive medium for Ag-Cu2O nanocomposites, enabling a uniform coating and optimal structural through spin-coating. During daylight hours, visible light irradiation excites Ag-Cu2O nanocomposites to produce reactive oxygen species (ROS), which cooperates with the hydration layer, exhibit a high-level antifouling effect. Notably, the unique structural coating can emit a weak coral-like fluorescence at night, sustaining ROS release and further enhancing antifouling performance. The assembly structure of the composite film was studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and water contact angle (WCA), while its antifouling performance was evaluated through antibacterial tests and a 30-day light-dark cycle anti-algae attachment experiment. The distinct nighttime antifouling capability contributes to 97.30 % anti-algae settled rate over a 30-day diurnal cycle. Moreover, we also investigated the effect of phosphor color on the composite film's antifouling properties. The blue phosphor group exhibited greater antifouling performance than the green or transparent phosphor group. The composite film created with multiple synergistic mechanisms exhibited auspicious antifouling performance. Further improvement and development of this composite film could unlock even greater potential for its antifouling properties.

Optimization of energy efficiency in gas production from hydrates assisted by geothermal energy enriched in the deep gas

Scaled-up production from natural gas hydrates is still facing the significant issues of limited gas yield and unsustainable hydrate dissociation. In this work, the deep gas with huge reserves and abundant geothermal energy was used to enhance the hydrate production efficiency. Results showed that the geotherm-assisted gas production was significantly increased by 178.22 %. Surprisingly, the hydrate dissociation rate was slightly weakened by 3.66 % due to the hindered fugacity of the gas from hydrate decomposition as a result of the fast deep gas upwelling. Besides, the energy flow analysis showed that up to 40.67 % of the deep gas injection energy was dissipated to the surroundings, with only 8.28 % utilized for the hydrate decomposition. Consequently, the multi-well deployment was used to regulate the deep gas injection rate. It was found that the multiple wells weakened the sealing effect of hydrate on migration channels, preventing the violent gas upwelling while increasing the hydrate decomposition amount under geothermal stimulation. Then, prolonging crossflow distance of deep gas in the hydrate layer enabled the sediment to absorb more injected energy, resulting in the minimum wasted energy ratio. Not limited to this, the more stable gas production throughout the whole process effectively guaranteed the safety of exploitation. Finally, the hydrate decomposition rate in the depressurization and constant pressure stages was found to be positively correlated with the utilization ratio of the injected energy and the injected rate, respectively. The results could help guide the formulation of the multi-gas joint production scenarios in the field tests to balance production efficiency and cost.

Role of the structural order of the hydration layer in regulating the heterogeneous ice nucleation efficiency

Understanding the complex microscopic mechanisms of heterogeneous ice nucleation is crucial across diverse fields from cloud science to microbiology. In this work, we examined the ability of solid surfaces to promote ice nucleation as a function of the structural order of interfacial water, including the first and second hydration layers. Comprehensive all-atom molecular dynamics simulations using the TIP4P/ice water model were conducted on a water film atop a modeled surface inspired by the (0001) surface of AgI crystal, with varying surface charges. These simulations revealed non-monotonic nucleation rates. The first hydration layer formed a hexagonal hydrogen-bond network resembling ice structures, exhibiting low mobility essential for inducing ice nucleation. Notably, the second hydration layer, acting as a key-point bridge, displayed varying degrees of orientational preference facilitated by inter-layer hydrogen bonds. The calculation of fluctuation parameters indicated that the greater structural order of the second layer significantly enhances the surface’s ice-forming capabilities. Unlike previous studies that focused primarily on the role of the first layer of interfacial water, our findings demonstrate that the second layer provides a more accurate indicator of ice nucleation capabilities.

Unveiling Contact-Electrification Effect on Interfacial Water Oscillation.

Water is crucial for various physicochemical processes at the liquid-solid interfaces. In particular, the interfacial water, mediating the electric field and solvation effect along with the solid, corporately determine the electrochemical properties. Understanding the interaction between solid properties and the interface water holds significant importance in interfacial dynamics. However, the impact of alterations in the charged state of solid surfaces induced by contact electrification on interfacial water remains unknown. Here, the evolution of atomic-level resolution maps of hydration layers are reported on charged surfaces using 3D atomic force microscopy (3D-AFM). These findings demonstrate that electrostatic interactions can reinforce, distort, or collapse the characteristic structure of hydration layers. More importantly, these interactions exhibit interlayer differences and sample specificity in hydration layer structures of different substrates. In addition, similar oscillations of the hydration layer are observed at the electrochemical interface under different voltage biases. This suggests that contact-electrification has the potential to serve as a novel method for manipulating and regulating chemical reactions at the interface.

Hydration structure and dynamics of phosphoric acid and its anions-Ultrafast 2D-IR spectroscopy and abinitio molecular dynamics simulations.

The hydration shells of phosphate ions and phosphate groups of nucleotides and phospholipid membranes display markedly different structures and hydrogen-bond strengths. Understanding phosphate hydration requires insight into the spatial arrangements of water molecules around phosphates and in thermally activated structure fluctuations on ultrafast time scales. Femtosecond two-dimensional infrared spectroscopy of phosphate vibrations, particularly asymmetric stretching vibrations between 1000 and 1200cm-1, and abinitio molecular dynamics (AIMD) simulations are combined to map and characterize dynamic local hydration structures and phosphate-water interactions. Phosphoric acid H3PO4 and its anions H2PO4-, HPO42-, and PO43- are studied in aqueous environments of different pH value. The hydration shells of phosphates providing OH donor groups in hydrogen bonds with the first water layer undergo ultrafast structural fluctuations, which induce a pronounced spectral diffusion of vibrational excitations on a sub-300fs time scale. With a decreasing number of phosphate OH groups, the hydration shell becomes more ordered and rigid. The 2D-IR line shapes observed with hydrated PO43- ions display a pronounced inhomogeneous broadening, reflecting a distribution of hydration geometries without fast equilibration. The AIMD simulations allow for an in-depth characterization of the hydration geometries with different numbers of water molecules in the first hydration layer and different correlation functions of the fluctuating electric field that the water environment exerts on the vibrational phosphate oscillators.

Fabrication of N/P-codoped carbon dots with anti-bacterial activity for enhanced aqueous lubrication performance

To address energy wastage caused by friction, it is urgently needed to develop multi-functionalized nano-additives based on traditional lubricant additives. Herein, nitrogen/phosphorus co-doped carbon dots (N,P-CDs) are successfully prepared via one step hydrothermal method using benzopyrrole as raw materials and diethylenetriaminepenta as N, P-dopant. The prepared N,P-CDs demonstrate good lubrication effects when used as water-based additives. Compared with pure H2O, the coefficient of friction (COF) significantly decreases from 0.448 to 0.144, accompanied by a notable reduction in wear volume from 3.84 × 105 μm3 to 2.31 × 105 μm3. This is attributed to the formulation of the robust hydration layer on the CDs surface, as well as the tribochemical protective film generated on the friction pair surface. In addition, the introduction of N,P-CDs effectively inhibits bacterial growth during long-term storage of H2O as lubricant. With small additions (100 μg/mL), the anti-bacterial rates against Escherichia coli and Staphylococcus aureus could reach 94.9 % and 99.5 %, respectively.

High-Speed Three-Dimensional Scanning Force Microscopy Visualization of Subnanoscale Hydration Structures on Dissolving Calcite Step Edges.

Hydration at solid-liquid interfaces plays an essential role in a wide range of phenomena in biology and in materials and Earth sciences. However, the atomic-scale dynamics of hydration have remained elusive because of difficulties associated with their direct visualization. In this work, a high-speed three-dimensional (3D) scanning force microscopy technique that produces 3D images of solid-liquid interfaces with subnanoscale resolution at a rate of 1.6 s per 3D image was developed. Using this technique, direct 3D images of moving step edges were acquired during calcite dissolution in water, and hydration structures on transition regions were visualized. A Ca(OH)2 monolayer was found to form along the step edge as an intermediate state during dissolution. This imaging process also showed that hydration layers extended from the upper terraces to the transition regions to stabilize adsorbed Ca(OH)2. This technique provides information that cannot be obtained via conventional 1D/2D measurement methods.