Bond Breaking Research Articles

Amorphous Ni(OH)2 Coated Cu Dendrites with Superaerophobic Interface for Bipolar Hydrogen Production Assisted with Formaldehyde Oxidation.

Since formaldehyde oxidation reaction (FOR) can release H2, it is attractive to construct a bipolar hydrogen production system consisting of FOR and hydrogen evolution reaction (HER). Although copper-based catalysts have attracted much attention due to their low cost and high FOR activity, the performance enhancement mechanism lacks in-depth investigation. Here, an amorphous-crystalline catalyst of amorphous nickel hydroxide-coated copper dendrites on copper foam (Cu@Ni(OH)2/CF) is prepared. The modification of Ni(OH)2 resulted in hydrophilic and aerophobic states on the Cu@Ni(OH)2/CF surface, facilitating the transport of liquid-phase species on the electrode surface and accelerating the release of H2. The Open circuit potential (OCP) and density functional theory (DFT) calculations indicate that this core-shell structure facilitates the adsorption of HCHO and OH-. In addition, the catalytic mechanism and reaction pathway of FOR are investigated through in situ FTIR and DFT calculations, and the results showed that the modification of Ni(OH)2 lowered the energy barrier for C─H bond breaking and H─H bond formation. In the HER//FOR system, Pt/C//Cu@Ni(OH)2/CF can provide a current density of 0.5 A cm-2 at 0.36V and achieve efficient and stable H2 production. This work offers new ideas for designing electrocatalysts for bipolar hydrogen production system assisted with formaldehyde oxidation.

Towards a unified fold-cusp model for bond polarity scaling: electron rearrangements in the pyrolytic isomerization of cubane to cyclooctatetraene.

This study meticulously examines the criteria for assigning electron rearrangements along the intrinsic reaction coordinate (IRC) leading to bond formation and breaking processes during the pyrolytic isomerization of cubane (CUB) to 1,3,5,7-cyclooctatetraene (COT) from both thermochemical and bonding perspectives. Notably, no cusp-type function was detected in the initial thermal conversion step of CUB to bicyclo[4.2.0]octa-2,4,7-triene (BOT). Contrary to previous reports, all relevant fluxes of the pairing density must be described in terms of fold unfolding. The transannular ring opening in the second step highlights characteristics indicative of a cusp-type catastrophe, facilitating a direct comparison with fold features. This fact underscores the critical role of density symmetry persistence near topographical events in determining the type of bifurcation. A fold-cusp unified model for scaling the polarity of chemical bonds is proposed, integrating ubiquitous reaction classes such as isomerization, bimolecular nucleophilic substitution, and cycloaddition. The analysis reveals that bond polarity index (BPI) values within the [0, 10-5] au interval correlate with cusp unfolding, whereas fold spans over a broader [10-3, ∞) au spectrum. These insights emphasize that the cusp polynomial is suitable for describing chemical processes involving symmetric electron density distributions, particularly those involving homolytic bond cleavages; in contrast, fold characterizes most chemical events. Geometry optimization and frequency calculations were conducted using various DFT functionals. In line with recent findings concerning the rigorous application of BET, the characterization of bond formations and scissions via unfoldings was carried out by carefully monitoring the determinant of the Hessian matrix at all potentially degenerate CPs and their relative distance. The computed gas-phase activation enthalpies strongly align with experimental values, stressing the adequacy of the chosen levels of theory in describing the ELF topography along the IRC. The BPI was determined using the methodology proposed by Allen and collaborators.

Exploring Mechanism and Kinetics of 1,4-Dioxane Oxidative Degradation by OH Radical: A Computational Quantum Chemistry Investigation.

This study aims to shed light on the mechanism and kinetics of 1,4-dioxane degradation by hydroxyl radical (OH) across various solvation conditions to evaluate electronic and structural properties at the MP2/aug-cc-pVTZ level. Transition states (TS) structures determined in the gas phase and SMD solvation model reveal similar hydrogen abstraction patterns. In contrast, the explicit solvation model (ES) introduces significant changes, suggesting a kinetic preference for axial pathways. The reaction rate constants, employing Deformed Transition State Theory (d-TST), are consistently higher for axial abstraction. The preference for axial hydrogen abstraction, solvation effects on transition states, and temperature-dependent rate constants are highlighted. Furthermore, the identification of carbon-carbon orbital distortion suggests potential bond breakage. This research provides valuable insights into the reaction between 1,4-dioxane and OH radical across different solvation models and enhances the understanding of the advanced oxidative process.

KNG1 mutations (c.618 T > G and c.1165C > T) cause disruption of the Cys206-Cys218 disulfide bond and truncation of the D5 domain leading to hereditary high molecular weight kininogen deficiency.

High molecular weight kininogen (HMWK), encoded by the kininogen-1 (KNG1) gene, is a multifunctional glycoprotein closely associated with the initiation of blood coagulation, tumor growth, and other pathological processes. We conducted a study on the clinical phenotype, genetic mutations, and molecular pathogenesis of a female patient with uterine leiomyosarcoma, who presented with HMWK deficiency and an isolated prolonged activated partial thromboplastin time (APTT). Clinical phenotyping was conducted through APTT mixing studies, quantitative assessments of intrinsic coagulation factor activities, antigen levels of HMWK, and thromboelastography. Genetic analysis revealed a novel mutation within the KNG1 gene. Subsequent bioinformatics analysis focused on the evolutionary conservation of regions flanking codons 618 and 1165 of the KNG1 gene, with an aim of predicting the mutation's functional impact. Clinical phenotypic analysis indicated a severe deficiency of HMWK antigen levels in the patient, with levels below 1.0 % of normal. Genetic sequencing identified two mutation sites in the KNG1 gene: a novel missense mutation in exon 5, c.618 T > G (p.Cys206Trp), which leads to disruption of the disulfide bond between Cys206 and Cys218, and a known nonsense mutation in exon 10, c.1165C > T (p.Arg389X), resulting in truncation of the D5 domain in the HMWK protein and reducing its quantity. These two mutations collectively impact the activation of HMWK within the coagulation system. The compound heterozygous mutations, c.618 T > G (p.Cys206Trp) and c.1165C > T (p.Arg389X), result in a loss of HMWK function, leading to a deficiency in the kinin system and consequently a significant prolongation of the APTT. These findings advance understanding of coagulation factor deficiencies and inform diagnostic and therapeutic approaches for HMWK deficiency, potentially enhancing clinical management strategies.

Atomic-scale insights into topotactic transformations in an extra-large-pore zeolite using time-resolved 3D electron diffraction

AbstractUnderstanding the atomic-scale structural dynamics of phase transformations is crucial for developing materials and tailoring their properties. However, many materials are obtained as polycrystalline powders with large unit cells and/or complex structures, making it challenging to investigate detailed structural changes using conventional X-ray diffraction techniques. Here we employ time-resolved three-dimensional electron diffraction to reveal the topotactic reactions and transformations that convert the extra-large-pore silicate zeolite ECNU-45 into ECNU-46. ECNU-45 features three-dimensional interconnecting 24 × 10 × 10-ring channels, while ECNU-46 consists of one-dimensional 24-ring channels connected to 10-ring pockets. ECNU-45 and ECNU-46 are both examples of pure silicate zeolites with pore openings larger than 22-ring. Our findings indicate changes at six distinct tetrahedral silicon sites, involving atom displacement, addition and removal of framework atoms through bond breakage and formation. This work presents the synthesis of zeolites and also provides atomic-level insights into the dynamic processes of topotactic reactions. Our results have implications for advancing materials engineering and understanding complex solid-state reactions at an atomic scale.

Weakening Pd─O Bonds by an Amorphous Pd Layer to Promote Electrocatalysis.

Construction of core-shell structured electrocatalysts with a thin noble metal shell is an effective strategy for lowering the usage of the noble metal and improving electrocatalytic properties because of the structure-induced geometric and electronic effects. Here, the synthesis of a novel core-shell structured nanocatalyst consisting of a thin amorphous Pd shell and a crystalline PdCu core and its significantly improved electrocatalytic properties for both formic acid oxidation and oxygen reduction reactions are shown. The electrocatalyst exhibits 4.1 times higher catalytic peak current density and better stability in the formic acid oxidation compared to both a PdCu nanoalloy catalyst and a Commercial Pd-C catalyst. An excellent electrocatalytic performance of the core-shell nanocatalyst is also observed in the oxygen reduction reaction. Computational calculation results reveal that tuning of the electronic state of Pd by the amorphous shell and the Cu in the PdCu core weaken the binding strength of surface Pd─O bonds, leading to a bond elongation to facilitate bond breaking. As a result, the electrocatalytic activity in both formic acid oxidation and oxygen reduction reactions is enhanced.

A Close Cognition of Charged Poly(l-methionine) Derivatives for Antifreeze.

Ice formation poses a significant challenge across various fields, from industrial processes to biological preservation. Developing antifreeze agents and recognizing the antifreeze mechanism have gained considerable attention. Herein, a series of poly(l-methionine) derivatives, poly(S-carboxymethyl-l-methionine sulfonium) (PMetA), poly(S-methyl-l-methionine sulfonium chloride) (PMetM), and poly(S-carbamidomethyl-l-methionine sulfonium chloride) (PMetAM), with carboxyl, methyl, and acetamide groups, respectively, are synthesized and investigated for antifreeze. The relationship between the polymer structure and the ice recrystallization inhibition (IRI) activity is examined, suggesting that zwitterionic PMetA shows the highest IRI activity, about 27.0 ± 3.9% at 10 mg mL-1 relative to that of water. Results of low-field nuclear magnetic resonance and differential scanning calorimetry indicate that the IRI activity is associated with the activation energy for hydrogen bond breakage. PMetA exhibits acceptable cytocompatibility at 10.0 mg mL-1 and a good cryoprotective efficiency. This finding provides a valuable insight into the antifreeze mechanism, contributing to the development of potent cryoprotectants.

Recent Advances and Perspectives on Coupled Water Electrolysis for Energy-Saving Hydrogen Production.

Overall water splitting (OWS) to produce hydrogen has attracted large attention in recent years due to its ecological-friendliness and sustainability. However, the efficiency of OWS has been forced by the sluggish kinetics of the four-electron oxygen evolution reaction (OER). The replacement of OER by alternative electrooxidation of small molecules with more thermodynamically favorable potentials may fundamentally break the limitation and achieve hydrogen production with low energy consumption, which may also be accompanied by the production of more value-added chemicals than oxygen or by electrochemical degradation of pollutants. This review critically assesses the latest discoveries in the coupled electrooxidation of various small molecules with OWS, including alcohols, aldehydes, amides, urea, hydrazine, etc. Emphasis is placed on the corresponding electrocatalyst design and related reaction mechanisms (e.g., dual hydrogenation and N-N bond breaking of hydrazine and C═N bond regulation in urea splitting to inhibit hazardous NCO- and NO- productions, etc.), along with emerging alternative electrooxidation reactions (electrooxidation of tetrazoles, furazans, iodide, quinolines, ascorbic acid, sterol, trimethylamine, etc.). Some new decoupled electrolysis and self-powered systems are also discussed in detail. Finally, the potential challenges and prospects of coupled water electrolysis systems are highlighted to aid future research directions.

Functionalization of Polyethylene Terephthalate (PETE) Membranes for the Enhancement of Cellular Adhesion in Organ-on-a-Chip Devices.

Experimental reproducibility in organ-on-chip (OOC) devices is a challenging issue, mainly caused by cell adhesion problems, as OOC devices are made of bioinert materials not suitable for natural cellularization of their surfaces. To improve cell adhesion, several surface functionalization techniques have been proposed, among which the simple use of an intermediate layer of adsorbed proteins has become the preferred one by OOC users. This way, the cells use surface receptors to adhere to the adsorbed proteins, which are in turn attached to the surface. However, as protein adsorption is based on weak electrostatic bonding between the coating proteins and the substrate, this method produces suboptimal results: as the weak electrostatic bonds break, cells detach, leading to poor, heterogeneous cellularization. To solve this problem, we present a surface functionalization method for polyethylene terephthalate (PETE) membranes, commonly used in multilayer organ-on-chip devices to support cellular layers. This protocol involves hydrolyzation of the membrane, followed by (3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) activation, resulting in covalent bonding between the membrane and coating proteins, much stronger than the weak electrostatic bonding provided by simple adsorption. As evaluation, we first measured the effect of the functionalization protocol in the morphological and mechanical integrity of the membranes. Next, we confirmed protein coating efficiency using the ζ potential and surface tension of the functionalized membranes coated with collagen type I, polylysine, gelatin, albumin, fetal bovine serum (FBS), and Matrigel. Finally, we showed that our method significantly improves the attachment of epithelial (A549) and endothelial (EA.hy926) cell lines under static conditions, especially in collagen-coated membranes, which were further tested under dynamic conditions, showing statistically significant improvement in cell attachment compared to uncoated or collagen-adsorbed only membranes.

Water-responsive Contraction for Shape-adaptive Bioelectronics

Water-responsive adaptive contraction represents a pivotal advancement in bioelectronics, offering unparalleled advantages over traditional swollen hydrogels and actuator-based systems. This review explores mechanisms including phase transition, hydrogen bond disruption, and hierarchical hybridization to enable rapid and substantial shape adaptability upon moisture exposure without external control and highlights various component modulation and porous and heterostructure engineering strategies to provide directional control and multifunctionality. Additionally, recent advances in supercontractile films, achieved through cold-drawing processes that disrupt hydrogen bonds in aligned polymer chains are overviewed for wearable and implantable biomedical applications where seamless tissue interfacing is essential. These advances address long-standing challenges in device integration with biological tissues, such as rigidity and inflammation, by creating electrodes that naturally conform to tissue shapes. This review delves into water-responsive adaptive contraction in bioelectronics, emphasizing its potential to revolutionize medical implants, wearable health monitors, and soft robotics by naturally conforming to tissue shapes upon moisture exposure. They promise significant improvements in chronic electronic integration and patient care, paving the way for next-generation medical devices, soft robotics, and smart textiles that adapt dynamically to biological environments.

Strong Component‐Interaction in N‐doped 2D Ti3C2Tx‐Supported Pt Electrocatalyst for Acidic Ethanol Oxidation Reaction

AbstractDesigning electrocatalysts with the selective C─C bond breaking in ethanol electro‐oxidation is of interest as an efficient strategy to accelerate the large‐scale applications of direct ethanol fuel cells (DEFCs).Pt nanoparticles (NPs) are herein on N‐doped 2D Ti3C2Tx MXene via two‐step synthesis steps including NH3‐assisted hydrothermal and NaBH4‐assisted ethylene glycol reduction routes. With the selective C─C bond breaking, the as‐obtained 16 wt.% Pt/N‐Ti3C2Tx catalyst exhibits 435.35 mA mgPt−1 mass activity and 0.83 mA cm−2 specific activity, being 1.26‐ and 1.77‐fold increase compared to those of commercially available 20 wt.% Pt/C (346.21 mA mgPt−1 and 0.47 mA cm−2). This originates from the advantages of unique 2D structures and the strong interplay between Pt NPs and nitrogen‐doped Ti3C2Tx. Also, the Pt/N‐Ti3C2Tx shows superior CO‐poisoning resistance and long‐term stability for the acidic ethanol electro‐oxidation reaction (EOR). This work demonstrates the potential of heteroatom‐doped Ti3C2Tx MXenes to increase the C1 pathway selectivity and the catalytic performance of Pt‐based electrocatalysts in DEFCs.

Concreteness of energy and bonding concepts in 9th grade chemistry – examining learning among high and low achievers

ABSTRACT Concreteness fading was applied in a curricular unit on energy changes in chemical reactions. Students explored bond breaking and formation by physically interacting with magnets, observing these processes through computer simulations and diagrams, and applying them to chemical equations. The participants included 36 ninth graders from a regular public school and 56 from a science magnet school. Conceptual knowledge was assessed using questionnaires administered before and after the unit, and 11 students were interviewed to support the quantitative findings.We observed significant pretest-to-posttest gains among both groups, with magnet school students achieving college-level averages. Regular school students showed smaller gains on items related to the definition of bonds or those involving purely symbolic chemical representations. However, both groups made similar progress in understanding macro-scale observations of energy change and in applying bonding concepts to nano-scale visual representations. Consistent with other studies, our findings indicate that while concreteness fading is an effective teaching strategy, it does not reduce the performance gap between high and low achievers. Interviews suggest that this gap stems from the difficulty low achievers face in adopting bonding concepts as visual and physical representations are phased out.

Reactive molecular dynamics simulations investigating ROS-mediated HIV damage from outer gp120 protein to internal capsid protein.

Molecular dynamics (MD) with the ReaxFF force field is used to study the structural damage to HIV capsid protein and gp120 protein mediated by reactive oxygen species (ROS). Our results show that with an increase in ROS concentration, the structures of the HIV capsid protein and gp120 protein are more severely damaged, including dehydrogenation, increase in oxygen-containing groups, helix shortening or destruction, and peptide bond breaking. In particular, we noticed that extraction of H atoms from N atoms by ROS was significantly higher than that from C atoms. There was no significant difference in the effect of ROS on dehydrogenation and shortening or breaking of the helices. In contrast, the impact of O on the increase in oxygen-containing groups and the fracture of peptide bonds in the gp120 protein is more significant than that of O3, and the effect of O3 is greater than that of ˙OH. In addition, the degree of structural damage of the gp120 protein was greater than that of the capsid protein. These detailed findings deepen our understanding of the role of ROS in regulating the structure and function of the HIV capsid protein and gp120 protein and provide valuable insights for plasma therapy for acquired immune deficiency syndrome (AIDS).

A machine learned potential for investigating single crystal to single crystal transformations in complex organic molecular systems.

The packing of organic molecular crystals is often dominated by weak non-covalent interactions, making their in situ rearrangement under external stimuli challenging to understand. We investigate a pressure-induced single-crystal-to-single-crystal (SCSC) transformation between two polymorphs of 2,4,5-triiodo-1H-imidazole using machine learning potentials. This process involves the rearrangement of halogen and hydrogen bonds combined with proton transfer within a complex solid-state system. We developed a strategy to progressively approach the transition state along the phase transition path from both ends by using both the α and β crystal phases as initial structures for active learning. This method allowed us to develop a DFT-based machine learning potential that faithfully describes both of the stable phases and the transition processes. Our results demonstrate that these anisotropic interactions are represented accurately during molecular dynamic simulations. Bond breaking and reforming during proton transfer is observed and analysed in detail. This approach holds promise for simulating SCSC transitions in organic molecular crystals involving anisotropic interactions and chemical bond changes.

Ethylene glycol co-reduced templating synthesis of PtRhTe nanotubes for polyalcohol electrooxidation

Accelerating the commercialization process of direct fuel cells (DFCs) is an important alternative to alleviate the current energy dependence. While the development of DFCs is limited by the sluggish kinetics and unsatisfactory durability of Pt catalyst used in the anode electrode material. In this term, the intentional design of Pt electrocatalyst with specific shape and composition is helpful for the mitigation of the situation. By employing the appropriate template, one-dimensional (1D) catalyst such as nanotubes can be synthesized. Due to the different reduction rate of Rh and Pt salts precursors, the incorporation of another metal such as Rh with a relatively high content still remain a challenge, regardless of the fact that Rh can promote the C-C bonds break thus enhancing the reaction kinetic. Herein, with Te nanowires act as the template, an ethylene glycol co-reduced templating synthetic approach has been developed for the synthesis of 1D PtRhTe nanotubes with a comparable Pt/Rh ratio. Due to the enhanced polyalcohol electrooxidation kinetic promoted by the Rh, and the 1D porous structure, the resultant PtRhTe nanotubes present a better catalytic activity and stability for polyalcohol electrooxidation compared with PtTe nanotubes and Pt/C catalysts. The synthetic approach developed herein may also useful for controllable synthesis of other Rh-based materials.

Nonadiabatic ab initio chemical reaction dynamics for the photoisomerization reaction of 3,5-dimethylisoxazole via the S1 electronic state.

Nonadiabatic ab initio molecular dynamics simulations were performed to explore the photoisomerization pathway from isoxazole (iso-OXA) to oxazole (OXA), considering four electronic states. The XMS-CASPT2 and SA4-CASSCF theories were employed to describe these electronic structures, which were caused by 12 electrons in 11 orbitals with the cc-pVDZ + sp diffuse basis set; the Gaussian s- and p-type diffuse functions were extracted from Dunning's aug-cc-pVDZ function. The potential energy and its gradient at each time step were computed on-the-fly at these levels in the time evolution of the classical trajectory. When the two electronic states were close to each other, the trajectory surface hopping (TSH) judgment between the two adjacent states was carried out by the anteater procedure based on the Zhu-Nakamura formula (ZN-TSH). The two different excited state lifetimes were found to exist in the first electronic state (S1), estimated at 10.77 and 119.81 fs. Upon photoexcitation, the N-O bond breaks and energetically relaxes to the ground state (S0). In the pathway leading to the main product, azirine formation, the 5-membered ring retains a planar structure while undergoing a non-adiabatic transition with an increasing N-O bond distance. Furthermore, it was verified that a 1,2-shift takes place in the pathway that results in the production of ketenimine, causing a nonadiabatic transition.

CO2-broken Ti-O bonds in the TiO6 octahedron of CaTiO3 for greatly enhanced room-temperature ferromagnetism.

Preparation of two-dimensional (2D) ferromagnetic nanomaterials and the study of their magnetic sources are crucial for the exploration of new materials with multiple applications. Herein, two-dimensional room-temperature ferromagnetic (FM) CaTiO3 nanosheets are successfully constructed with the assistance of supercritical carbon dioxide (SC CO2). In this process, the SC CO2-induced strain effect can lead to lattice expansion and introduction of O vacancies. More importantly, experimentally it can be found out that the breakage of the Ti-O2 bond by CO2 directly results in the equatorial plane of the TiO6 octahedron being exposed. This leads to more opportunities for oxygen vacancies and low-valent titanium to appear, where Ti3+ can optimize the spin structure, releasing the macroscopic magnetization. Greatly improved room-temperature ferromagnetic behavior, with an optimal magnetization of 0.1661 emu g-1 and a high Curie temperature (Tc) of 300 K can be achieved.

Deep learning–based assessment of missense variants in the COG4 gene presented with bilateral congenital cataract

ObjectiveWe compared the protein structure and pathogenicity of clinically relevant variants of the COG4 gene with AlphaFold2 (AF2), Alpha Missense (AM), and ThermoMPNN for the first time.Methods and analysisThe sequences...

Tuning the Local-chemistry of the SPAN to Realize the Development of Room-Temperature Sodium-Sulfur Pouch Cells

Sulfurized polyacrylonitrile (SPAN), a nitrogen-rich carbon-sulfur framework, is a promising alternative to the elemental sulfur cathode. However, repetitive formation and breaking of carbon-sulfur bonds cause irreversible capacity loss. The capacity...

Disruption of a potential disulfide bond of Cys65–Cys141 on the structure and stability of globin X from zebrafish

Removal of the disulfide bond of Cys65–Cys14 in a newly discovered globin X was shown to alter the heme coordination state and protein reactivity, highlighting the critical role of the disulfide bond.