Ionic Hydrogen Bonds Research Articles

An Investigation of the Structures of [(Glycine)(1-Methyluracil)]M+ Complexes (M = H, Li, Na, K) in the Gas Phase by IRMPD Spectroscopy and Theoretical Methods.

The presence of ions in the complexation of molecules can profoundly affect the structure, resulting in changes to functionality and stability. These non-covalent interactions drive many biological processes both necessary and inimical and require extensive research to understand and predict their effects. Protonated and alkali metalated complexes of glycine (Gly) and 1-methyluracil (1-mUra) were studied using infrared multiphoton dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations. The experimental and simulated vibrational spectra were compared to help elucidate the structure of each complex. The lowest energy structure for [(Gly)(1-mUra)]H+ consists of amine protonated Gly bound to O4 of canonical 1-mUra through a single ionic hydrogen bond with another, intraglycine ionic hydrogen bond between the protonated amine group and the carbonyl oxygen. For [(Gly)(1-mUra)]Li+, [(Gly)(1-mUra)]Na+ and [(Gly)(1-mUra)]K+, the experimental spectra are most consistent with the metal cations binding in a trigonal planar geometry with 1-mUra bound to the metal cation via the O4 carbonyl. In [(Gly)(1-mUra)]Li+ and [(Gly)(1-mUra)]Na+, the metal cation is bound to canonical Gly via the carbonyl oxygen and amine nitrogen, but in [(Gly)(1-mUra)]K+, Gly is bound through both oxygens and contains an intraglycine hydrogen bond from the hydroxyl to the amine nitrogen.

A Study on the Stability of High Drug Solubility Characteristics of Hydroxyphenyl Adhesives under the Interference of CPEs.

Novel hydroxyphenyl adhesives (HP-PSAs) could significantly increase drug solubility and control drug release through a doubly ionic hydrogen bond (DIH bond) in the patch. However, chemical penetration enhancers (CPEs) always destroy the performance of most adhesives. As a result, this work investigated the stability of both the HP-PSA features and the DIH bond under the interference of the CPEs. Donepezil (DON) was chosen as the model drug, and CPEs with hydroxyl, carboxyl, amido, and ester groups were selected as model CPEs. Unlike the commonly used neutral H-bond, the DIH bond between DON and the HP-PSA was still stable under the interference of the CPEs, resulting in the 2-3-fold drug solubility in the HP-PSA, which was higher than that in the nonfunctional PSA, which reduced the drug crystallization risk and the difficulty of formulation design. FT-IR, 1H NMR, XPS, dynamic simulation, and molecular docking revealed the mechanism of the stability feature of both the DIH bond and the high drug solubility of the HP-PSA, which was that the formed neutral H-bond interaction caused by CPEs is weaker than that of the DIH bond between DON and the HP-PSA. Furthermore, the drug release, skin permeation, and CPE release study showed that the newly formed weak H-bond and strong ionic H-bond interaction promoted or controlled both DON and CPE release, respectively, thereby influencing drug skin permeation, which provided a theoretical basis for drug release regulation. To summarize, besides the reversible, strong features of the DIH bond in our previous study, the stability of the interaction made the HP-PSA's high drug solubility potential to be applied in the TDDS.

Effects of pH on Enzyme Activity in Pakistan

Purpose: The aim of the study was to assess the effects of pH on enzyme activity in Pakistan. Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: The study indicated that effects of pH on enzyme activity are significant because enzymes are highly sensitive to the pH levels in their environment. Each enzyme has an optimal pH at which it functions most efficiently. Deviations from this optimal pH can lead to a decrease in enzyme activity. At extreme pH levels, enzymes may become denatured, altering their structure and impairing their ability to bind to substrates. This is because changes in pH can affect the ionic bonds and hydrogen bonds within the enzyme, altering its active site. As a result, enzyme activity typically increases as the pH approaches the optimal level, and decreases when the pH moves away from this point. Therefore, maintaining proper pH levels is crucial for the effective functioning of enzymes in biological systems. Implications to Theory, Practice and Policy: Lock and key model, induced fit theory and chemical equilibrium theory may be used to anchor future studies on the effects of pH on enzyme activity in Pakistan. In practical applications, industries utilizing enzymes should prioritize the implementation of rigorous pH monitoring and control systems to maintain optimal conditions for enzymatic activity. From a policy perspective, it is crucial for policymakers to establish clear guidelines governing the use of enzymes in industrial applications, with a particular emphasis on the importance of pH control in achieving optimal performance.

Complexation of diserinol isophthalamide with phosphorylated biomolecules in electrospray ionization mass spectrometry

Electrospray ionization (ESI) enables gentle transfer of biomolecules from solution to vacuum, facilitating the study of biomolecular structure under highly controlled conditions. However, biomolecules are desolvated during the ESI process, and the loss of ionic hydrogen bonds to solvent molecules can drive structural rearrangement, most prominently at solvent-exposed charge sites. Microsolvation reagents can bind to these bare charge sites in ESI mass spectrometry (ESI–MS) experiments, providing alternative intermolecular interaction partners. Previously, 18-crown-6 was shown to be an effective reagent for binding to cationic monoalkylammonium residues. More recently, diserinol isophthalamide (DIP) was reported as an analogous anionic microsolvation reagent, primarily for carboxylate residues of small model peptides. Herein, we expand upon this work to examine the complexation of DIP, 1,1’-(1,2-phenylene)bis(3-phenylurea) (PBP), and triclocarban (TCC) with molecules featuring a terminal or linking phosphate moiety. Specifically, using ESI–MS, we assess the binding of these reagents with dimethyl phosphate (DMP), cyclic adenosine monophosphate (cAMP), dibutyryl cAMP, RNA dinucleotides ApU and CpG, and angiotensin II phosphate (DRVpYIHPF). For DMP, the smallest target molecule, reagents TCC, PBP and DIP showed favorable adduction. However, for larger systems, PBP and TCC showed reduced complexation, which was attributed to steric hindrance from the terminal aromatic moieties of PBP and the limited hydrogen bonding network of TCC. Overall, of the three reagents, DIP showed the most consistent performance for anionic microsolvation of phosphate groups, facilitating future studies of gas-phase biomolecular structure and the effects of microsolvation.

In Situ Detection of Interfacial Ions at the Single-Bond Level.

Detecting the ionic state at the solid-liquid interface is essential to reveal the various chemical and physical processes that occur at the interface. In this study, the adsorption states of the highly electronegative ions F- and OH- at the solid-liquid interface are detected by using the scanning tunneling microscopy break junction technique. With the active hydrogen atom of the amino group as a probe, the formed ionic hydrogen bonds are successfully detected, thereby enabling in situ monitoring of the ionic state at the solid-liquid interface. Through noise power spectral density analysis and theoretical simulations, we reveal the mechanism by which ionic hydrogen bonds at the interface affect the charge transport properties. In addition, we discover that the ionic state at the solid-liquid interface can be effectively manipulated by electric fields. Under high electric fields, the concentration of the anion near the electrode is higher, and the proportion of hydrogen bonds formed is greater than that under low electric fields. This study of the interfacial ionic state at the single-bond level provides guidance for the design of high-performance materials for energy conversion and environmental purification.

Arsenic Adsorption in Subunits of Metal‐Organic Frameworks—A DFT Approach to Assist Water Treatment

AbstractThe removal of arsenic compounds from water is classified as an urgent concern by the World Health Organization, since many of these species are hazardous to human health. However, the conventional water treatments are not able to extract them, which makes the development of new methodologies of arsenic removal noteworthy. The application of metal‐organic frameworks (MOFs) as adsorbents to attend this purpose is very promising, because these materials can be intelligently built for the desired application. In this work, the performance of common subunits usually found in MOFs were individually evaluated for the adsorption of some arsenic species through computer simulations based on density functional theory (DFT). Thus, important information at molecular level was obtained, which can assist the design of an optimized adsorbent. Three factors were identified to strengthen the adsorption: ionic coordinate bond, hydrogen bonds, and cycle formation. Furthermore, the evaluated subunits showed to be proper for the removal of HAsO2, once the change in the Gibbs free energy was up to −30.8 kcal mol−1. The comparison with possible coexistent species showed that Cl−, , and can interfere with adsorptive process depending on the MOF composition and on the arsenic species to be removed from water.

Arginine-solubilized lipoic acid-induced β-sheets of silk fibroin-strengthened hydrogel for postoperative rehabilitation of breast cancer

Breast cancer is the most common cancer among women worldwide, and adjuvant radiotherapy (RT) following tumor removal is one of the most commonly used treatments for breast cancer. However, the high risk of tumor recurrence and inevitable radiation skin injury after RT remain fatal problems, seriously challenging the patient's postoperative rehabilitation. Herein, a multifunctional poly (lipoic acid)-based hydrogel is constructed through one-step heating the mixture of α-lipoic acid (LA)/arginine (Arg)/silk fibroin (SF), without introducing any non-natural molecules. The multiple synergistic interactions among LA, Arg, and SF not only enhance the solubilization of LA in aqueous systems but also stabilize poly(lipoic acid) through strong salt bridge hydrogen bonds and ionic hydrogen bonds. Intriguingly, the LA-based surfactant induced β-sheet transformation of SF can further modulate the bulk strength of the hydrogel. Regulating the content of LA in hydrogels not only allows efficient control of hydrogel bioactivity but also enables the evolution of hydrogels from injectable forms to adhesive patches. Based on the different biological activities and forms of hydrogels, they can be implanted internally or applied externally on the mice's skin, achieving simultaneous prevention of tumor recurrence post-surgery and assistance in treating radiation-induced skin damage after radiotherapy.

Unraveling the Roles of Ionic Size and Hydrogen Bonding in Electric Field-Driven Ion Emission from Hydroxylamine Nitrate-Based Ionic Liquids.

Ionic size and hydrogen bonding (HB) may play significant roles in controlling ion emission from HAN (hydroxylamine nitrate)-based ionic liquids (ILs) but have received little attention. In this paper, the ion emission behavior and mechanism in an external electric field are meticulously investigated using the molecular dynamics (MD) method and density functional theory. We find that the higher the proportion of ionic HAN in the blend of ILs, the longer the delay time of the ion start-up emission. In the positive mode, cations can evaporate directly from the surface of the studied ILs and manifest exclusively as the [EMIM]+ monomers within the simulation time scale, whereas in the negative mode, a variety of complicated anion clusters are emitted. As a result, the average charge-to-mass ratio of the positively charged species remarkably exceeds that of the negatively charged species. This large difference is attributed to the relatively larger size of the [EMIM]+ ion and the absence of substantial HB interactions between the [EMIM]+ ion and any other monomer, leading to diminished binding energies. Conversely, the strong HB interactions, primarily constituted by N-H--O and O-H--O hydrogen bonds, are clearly found in the [EtSO4]--based and HAN-based clusters. In addition, the [NO3]- and [EtSO4]- ions tend to combine with the small-sized [HA]+ ions to form large anion clusters rather than with the [EMIM]+ ions. The energy decomposition results further elucidate that the orbital interaction plays a pivotal role in the [NO3]- and [EtSO4]--based clusters. The findings clearly elucidate the experimental phenomena observed in previous studies and have implications for the formulation of multimode IL propellants.

Assessing Structures and Solution Behaviors of Molecular and Ionic Cocrystals with a Common Bioactive Molecule: 2,4-Pyridinedicarboxylic Acid with Tranexamic Acid and Nicotinamide.

Cocrystals of 2,4-pyridinedicarboxylic acid (PDA) with either nicotinamide (NTD) or tranexamic acid (TXA) as (PDA)·(NTD) and 2(PDA)·(TXA), respectively, are reported, with the former being a molecular cocrystal and the latter being an ionic cocrystal. Single-crystal structure analyses showed that PDA and its coformers are sustained by neutral and ionic hydrogen bonds. Suspensions of (PDA)·(NTD) resulted in complete conversion to PDA monohydrate after 48 h, while 2(PDA)·(TXA) was thermodynamically stable at a lower pH and showed a 2-fold increase in the PDA concentration, relative to pure PDA monohydrate under similar conditions. Thermal characterization of 2(PDA)·(TXA) displayed a lower melting point and a lower heat of fusion, relative to the pure components. Powder dissolution studies were evaluated for PDA, (PDA)·(NTD), and 2(PDA)·(TXA) and the corresponding physical mixtures. The percent of PDA dissolved rapidly reached near 100% for most cases; however, for 2(PDA)·(TXA), complete dissolution was not achieved, and the amount of PDA dissolved decreased to 85% after 3 h. Instability of 2(PDA)·(TXA) was likely a result of a high solution pH during dissolution, and our results confirm that the solution pH plays a key role in determining the solution behavior and phase stability of the cocrystals.

Effects of sodium tripolyphosphate on the quality and digestion properties of PSE pork

This study aimed to examine the impact of sodium tripolyphosphate (STPP) on the quality and digestive characteristics of PSE pork. The results showed a notable decrease in cooking loss of PSE pork from 29.11% to 25.67% with increasing STPP concentration (P < 0.05). Additionally, the gastric digestibility of PSE pork decreased significantly from 52.01% to 45.81% (P < 0.05). The particle size of digesta decreased significantly after gastrointestinal digestion (P < 0.05). These changes were primarily due to the enhanced cross-linking of proteins through ionic interactions, hydrogen bonds and hydrophobic interactions, and resulted in the embedding of hydrophobic groups and endogenous fluorophores. Furthermore, denser network was formed. These findings give a new insight into considering the impact of STPP on meat nutrition when used to enhance texture and water holding capacity.

Probing the Effects of Size and Charge on the Monohydration and Dihydration of SiF5- and SiF62- via Comparisons with BF4- and PF6.

This study systematically examines the interactions of the trigonal bipyramidal silicon pentafluoride and octahedral silicon hexafluoride anions with either one or two water molecules, (SiF5-(H2O)n and SiF62-(H2O)n, respectively, where n = 1, 2). Full geometry optimizations and subsequent harmonic vibrational frequency computations are performed using the CCSD(T) ab initio method with a triple-ζ correlation consistent basis set augmented with diffuse functions on all non-hydrogen atoms (cc-pVTZ for H and aug-cc-pVTZ for Si, O, and F; denoted as haTZ). Two monohydrate and six dihydrate minima have been identified for the SiF5-(H2O)n systems, whereas one monohydrate and five dihydrate minima have been identified for the SiF62-(H2O)n systems. Both monohydrated anions have a minimum in which the water molecule adopts a symmetric double ionic hydrogen bond (DIHB) motif with C2v symmetry. However, a second unique monohydrate minimum has been identified for SiF5- in which the water molecule adopts an asymmetric DIHB motif along the edge of the trigonal bipyramidal anion between one axial and one equatorial F atom. This Cs structure is more than 2 kcal mol-1 lower in energy than the C2v local minimum at the CCSD(T)/haTZ level of theory. While the interactions between the solvent and ionic solute are quite strong for the monohydrated anions (electronic dissociation energies of ≈12 and ≈24 kcal mol-1 for the SiF5-(H2O)1 and SiF62-(H2O)1 global minima, respectively), these values are nearly perfectly doubled for the dihydrates, with the lowest-energy SiF5-(H2O)2 and SiF62-(H2O)2 minima exhibiting dissociation energies of ≈24 and ≈47 kcal mol-1, respectively. Structures that form hydrogen bonds between the solvating water molecules also exhibit the largest shifts in the harmonic OH stretching frequencies for the waters of hydration. These shifts can exceed -100 cm-1 for the SiF5-(H2O)2 minimum and -300 cm-1 for the SiF62-(H2O)2 minimum relative to an isolated H2O molecule at the CCSD(T)/haTZ level of theory. This work also corrects the OH stretching frequency shifts for two dihydrate minima of PF6- that were previously erroneously reported ( J. Phys. Chem. A 2020, 124, 8744-8752, DOI: 10.1021/acs.jpca.0c06466).

Pnictogen-Bonding Enzymes.

The objective of this study was to create artificial enzymes that capitalize on pnictogen bonding, a s-hole interaction that is essentially absent in biocatalysis. For this purpose, stibine catalysts were equipped with a biotin derivative and combined with streptavidin mutants to identify an efficient transfer hydrogenation catalyst for the reduction of a fluorogenic quinoline substrate. Increased catalytic activity from wild-type streptavidin to the best mutants coincides with the depth of the s hole on the Sb(V) center, and the emergence of saturation kinetic behavior. Michaelis-Menten analysis reveals transition-state recognition in the low micromolar range, more than three orders of magnitude stronger than the millimolar substrate recognition. Carboxylates preferred by the best mutants contribute to transition-state recognition by hydrogen-bonded ion pairing and anion-π interactions with the emerging pyridinium product. The emergence of challenging stereoselectivity in aqueous systems further emphasizes compatibility of pnictogen bonding with higher order systems catalysis.

Synthesis of metal-free benzimidazole-based catalysts and its application in CO2 cycloaddition.

Ionic polymers functionalized with hydroxyl, carboxyl, and amino groups can enhance the catalytic activity of catalysts. However, the straightforward preparation of bifunctional ionic polymers containing abundant ionic active sites and hydrogen bond donors remains challenging. In this study, a series of porous ionic polymers (BZIs) containing different hydrogen bond donors (-NH2, -OH, -COOH) were prepared through a simple one-pot Friedel-Crafts alkylation using benzimidazole derivatives and benzyl bromide. The structures and properties of BZIs were characterized by various techniques such as Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, solid-state nuclear magnetic resonance, and scanning electron microscopy. Among the prepared catalysts (BZI-NH2, BZI-OH, and BZI-COOH), BZI-NH2 exhibited the highest catalytic activity and recyclability, achieving a yield of 97% in the CO2 cycloaddition. The synergistic effect of Br-, hydrogen bond donors (-NH-, -NH2), and N+ in BZI-NH2 was found to contribute to its superior catalytic performance. DFT calculations were employed to study the effect of hydrogen bonds, Br-, and N+ in BZI-NH2 and BZI-OH on the CO2 cycloaddition. Using BZI-NH2 as an example, a mechanism was proposed for the synergistic effect between amino groups and bromide ions in catalyzing the CO2 cycloaddition reaction.

Ionic Hydrogen Bond-Assisted Catalytic Construction of Nitrogen Stereogenic Center via Formal Desymmetrization of Remote Diols.

The control of noncarbon stereogenic centers is of profound importance owing to their enormous interest in bioactive compounds and chiral catalyst or ligand design for enantioselective synthesis. Despite various elegant approaches have been achieved for construction of S-, P-, Si- and B-stereocenters over the past decades, the catalyst-controlled strategies to govern the formation of N-stereogenic compounds have garnered less attention. Here, we disclose the first organocatalytic approach for efficient access to a wide range of nitrogen-stereogenic compounds through a desymmetrization approach. Intriguingly, the pro-chiral remote diols, which are previously not well addressed with enantiocontrol, are well differentiated by potent chiral carbene-bound acyl azolium intermediates. Preliminary studies shed insights on the critical importance of the ionic hydrogen bond (IHB) formed between the dimer aggregate of diols to afford the chiral N-oxide products that feature a tetrahedral nitrogen as the sole stereogenic element with good yields and excellent enantioselectivities. Notably, the chiral N-oxide products could offer an attractive strategy for chiral ligand design and discovery of potential antibacterial agrochemicals.

Ionic Hydrogen Bond‐Assisted Catalytic Construction of Nitrogen Stereogenic Center via Formal Desymmetrization of Remote Diols

AbstractThe control of noncarbon stereogenic centers is of profound importance owing to their enormous interest in bioactive compounds and chiral catalyst or ligand design for enantioselective synthesis. Despite various elegant approaches have been achieved for construction of S‐, P‐, Si‐ and B‐stereocenters over the past decades, the catalyst‐controlled strategies to govern the formation of N‐stereogenic compounds have garnered less attention. Here, we disclose the first organocatalytic approach for efficient access to a wide range of nitrogen‐stereogenic compounds through a desymmetrization approach. Intriguingly, the pro‐chiral remote diols, which are previously not well addressed with enantiocontrol, are well differentiated by potent chiral carbene‐bound acyl azolium intermediates. Preliminary studies shed insights on the critical importance of the ionic hydrogen bond (IHB) formed between the dimer aggregate of diols to afford the chiral N‐oxide products that feature a tetrahedral nitrogen as the sole stereogenic element with good yields and excellent enantioselectivities. Notably, the chiral N‐oxide products could offer an attractive strategy for chiral ligand design and discovery of potential antibacterial agrochemicals.

Simulation of calcium carbonate nucleation processes in confined C-S-H nanopores with different calcium-silicon ratios

Carbonation curing technology plays an important role in carbon cycling and improving the properties of cement-based materials, while the nucleation and growth mechanism of calcium carbonate (CaCO3) is still unclear. Based on molecular dynamics simulation, the formation process and nucleation mechanism of CaCO3 in confined C-S-H nanopores with different calcium-silicon ratios were studied. The results show that the clustering behavior of CaCO3 in C-S-H nanopores filled with saturated CaCO3 solution can be divided into three phases, rapid agglomeration stage, slow cluster stage, and stable cluster stage. The aggregation is mainly dependent on ionic bonding for nucleation growth and is consistent with the prenucleation mechanism. The Ca/Si ratio of C-S-H has a direct influence on the clustering of CaCO3. The anchoring mechanism of CaCO3 clusters is determined by ionic bonds and hydrogen bonds, and large clusters are preferentially adsorbed at the C-S-H interface through ionic bonds. The Ca/Si ratio of 1.5 can provide more nucleation sites by ionic bonds and hydrogen bonds for the formation of CaCO3, which is more conducive to the growth of clusters. And the calcium source from C-S-H in cluster bodies can be as high as 33 %. This study helps to understand the early formation process of CaCO3 in cement-based materials and lays a theoretical foundation for the development of carbonization curing technology.

Autocatalytic bifunctional supramolecular hydrogels for osteoporotic bone repair.

Conventional bone scaffolds, which are mainly ascribed to highly active osteoclasts and an inflammatory microenvironment with high levels of reactive oxygen species and pro-inflammatory factors, barely satisfy osteoporotic defect repair. Herein, multifunctional self-assembled supramolecular fiber hydrogels (Ce-Aln gel) consisting of alendronate (Aln) and cerium (Ce) ions were constructed for osteoporotic bone defect repair. Based on the reversible interaction and polyvalent cerium ions, the Ce-Aln gel, which was mainly composed of ionic coordination and hydrogen bonds, displayed good injectability and autocatalytic amplification of the antioxidant effect. In vitro studies showed that the Ce-Aln gel effectively maintained the biological function of osteoblasts by regulating redox homeostasis and improved the inflammatory microenvironment to enhance the inhibitory effect on osteoclasts. Ribonucleic acid (RNA) sequencing further revealed significant downregulation of various metabolic pathways, including apoptosis signaling, hypoxia metabolism and tumor necrosis factor-alpha (TNF-α) signaling via the nuclear factor kappa-B pathway after treatment with the Ce-Aln gel. In vivo experiments showed that the clinical drug-based Ce-Aln gel effectively promoted the tissue repair of osteoporotic bone defects by improving inflammation and inhibiting osteoclast formation at the defect. Notably, in vivo systemic osteoporosis was significantly ameliorated, highlighting the strong potential of clinical translation for precise therapy of bone defects.

Spectroscopic Evidence for Doubly Hydrogen-Bonded Cationic Dimers in the Solid, Liquid, and Gaseous Phases of Carboxyl-Functionalized Ionic Liquids.

Intermolecular interactions determine whether matter sticks together, gases condense into liquids, or liquids freeze into solids. The most prominent example is hydrogen bonding in water, responsible for the anomalous properties in the liquid phase and polymorphism in ice. The physical properties are also exceptional for ionic liquids (ILs), wherein a delicate balance of Coulomb interactions, hydrogen bonds, and dispersion interactions results in a broad liquid range and the vaporization of ILs as ion pairs. In this study, we show that strong, local, and directional hydrogen bonds govern the structures and arrangements in the solid, liquid, and gaseous phases of carboxyl-functionalized ILs. For that purpose, we explored the H-bonded motifs by X-ray diffraction and attenuated total reflection (ATR) infrared (IR) spectroscopy in the solid state, by ATR and transmission IR spectroscopy in the liquid phase, and by cryogenic ion vibrational predissociation spectroscopy (CIVPS) in the gaseous phase at low temperature. The analysis of the CO stretching bands reveals doubly hydrogen-bonded cationic dimers (c═c), resembling the archetype H-bond motif known for carboxylic acids. The like-charge doubly hydrogen-bonded ion pairs are present in the crystal structure of the IL, survive phase transition into the liquid state, and are still present in the gaseous phase even in (2,1) complexes wherein one counterion is removed and repulsive Coulomb interaction increased. The interpretation of the vibrational spectra is supported by quantum chemical methods. These observations have implications for the fundamental nature of the hydrogen bond between ions of like charge.

Deep dewatering of sludge and resource recovery of hydroxyapatite: A recyclable approach via ionic liquid biphasic system and hydrogen bonds reformation

Deep dewatering of Waste Activated Sludge (WAS) through mechanical processes remains inefficient, primarily due to the formation of a stable hydrogen bonding network between the biopolymers and water, which consequently leads to significant water trapped by Extracellular Polymeric Substances (EPS). In this study, a novel and recyclable treatment for WAS based on Ionic Liquids (ILs) was established, named IL-biphasic aqueous system (IL-ABS) treatment. Specifically, the IL-ABS formed in WAS facilitated rapid and efficient in-situ deep dewatering while concurrently recovering hydroxyapatite. The water content decreased from an initial 98.27 % to 65.35 % with IL-ABS, formed by 1-Butyl-3-methylimidazolium bromide (BmimBr) and K3PO4 synthesized from waste H3PO4. Moreover, the recycled BmimBr maintaining the water content of the dewatered sludge consistently between 65.61 % and 67.25 % across five cycles, exhibited remarkable reproducibility. Through three-dimensional excitation-emission matrix, lactate dehydrogenase analyses and confocal laser scanning microscopy, the high concentration of BmimBr in the upper phase effectively disrupted the cells and EPS, which exposed protein and polysaccharide on the EPS surface. Subsequently, the K3PO4 in the lower phase led to an enhanced salting-out effect in WAS. Furthermore, FT-IR analysis revealed that K3PO4 disrupted the original hydrogen bonds between EPS and water. Then, BmimBr formed numerous hydrogen bonds with the sludge flocs, leading to deep dewatering and agglomeration of the sludge flocs during the unique phase separation process of IL-ABS. Notably, sludge-derived hydroxyapatite product exhibited remarkable adsorption capacity for prevalent heavy metal contaminants such as Pb2+, Cd2+ and Cu2+, with efficiencies comparable to those of commercial hydroxyapatite, thereby achieving the resource utilization of waste H3PO4. Moreover, economic calculations demonstrated the suitability of this novel treatment. This innovative treatment exhibits potential for practical applications in the non-mechanical deep dewatering of WAS.

Incomplete ionic interactions and hydrogen bonds constructing elastomers with water accelerated Self-Healing and self-healing strengthening capacities

Self-healing polymers with microphase separation structure typically require external stimuli to achieve self-healing, and their performance often degrades. To solve these issues, we introduce tertiary amine and carboxyl groups into polymer. The intermolecular ionic interactions and H-bonds contribute to the formation of microphase separation structures, endowing polyurethane elastomers (PU-n) outstanding mechanical properties with a maximum tensile strength and toughness of 20.61 MPa and 59.02 MJ/m3, respectively. The self-healing of the prepared PU-n can be achieved at room temperature and accelerated significantly by water because hard phases can be dissociated, resulting in enhanced molecular movement. After self-healing with water, the enhanced molecular movement and further ionization of ionic groups lead to stronger H-bonds and ionic interactions, promoting more distinct microphase separation. Thus, the mechanical strength is strengthened and the self-healing efficiency can reach 104.72 %. The enhanced molecular movement and strengthened intermolecular interactions when self-healing with water can also be verified through in-depth analysis of molecular dynamics (MD) simulations of the self-healing process. Furthermore, PU-n display remarkable shape memory and can be recycled through exposure to solvents and hot water. This study provides a novel and general method for preparing materials that can self-heal with water and self-strengthen after self-healing.