Bond Breaking Research Articles

Mechanism of SO2 effect on the simultaneous removal of NOx and propane over bifunctional NiMn2O4-CeO2 catalysts.

Nitrogen oxides (NOx) and volatile organic compounds (VOCs) are the main pollutants in flue gas, and the synergistic removal of NOx and VOCs in the presence of SO2 is still a challenge. In this work, the microstructure of NiMn2O4-CeO2 catalysts and the distribution of sulfur-containing substances were studied to reveal the inactivation mechanism of sulfur poisoning. NOx conversion could reach more than 80% at 100-250°C, and C3H8 conversion could achieve 90% at 210°C in the synergistic reaction on NiMn2O4-CeO2 catalyst, which has dual active sites with propane oxidation and SCR reactions carried out at Mn and Ni sites, respectively. In addition, the intrinsic effect of SO2 on propane oxidation and NOx reduction were investigated by decoupling. For propane oxidation, mechanistic studies have shown that manganese sulfate generated by SO2 hindered further reactions by inhibiting the breaking of the CC bond. For denitration reaction, the generation of sulfate not only resulted in electron transfer from Ni to Mn thereby reducing reaction activity, but also blocked the L-H pathway by inhibiting NO adsorption. This work provides guidelines and strategies to mitigate SO2 poisoning in the simultaneous removal of NOx and light alkane.

The Role of Protein Disulfide Isomerase Inhibitors in Cancer Therapy.

Protein disulfide isomerase (PDI) is a member of the mercaptan isomerase family, primarily located in the endoplasmic reticulum (ER). At least 21 PDI family members have been identified. PDI plays a key role in protein folding, correcting misfolded proteins, and catalyzing disulfide bond formation, rearrangement, and breaking. It also acts as a molecular chaperone. Dysregulation of PDI activity is thus linked to diseases such as cancer, infections, immune disorders, thrombosis, neurodegenerative diseases, and metabolic disorders. In particular, elevated intracellular PDI levels can enhance cancer cell proliferation, metastasis, and invasion, making it a potential cancer marker. Cancer cells require extensive protein synthesis, with disulfide bond formation by PDI being a critical producer. Thus, cancer cells have higher PDI levels than normal cells. Targeting PDI can induce ER stress and activate the Unfolded Protein Response (UPR) pathway, leading to cancer cell apoptosis. This review discusses the structure and function of PDI, PDI inhibitors in cancer therapy, and the limitations of current inhibitors, proposing especially future directions for developing new PDI inhibitors.

Sustaining 500,000 Folding Cycles Through Bioinspired Stress Dispersion Design in Sodium‐Ion Batteries

AbstractDeveloping super‐foldable electronic materials and devices presents a significant challenge, as intrinsic conductive materials are unable to achieve numerous true‐folding operations (super‐foldable) due to limitations from short‐range forces of chemical bonds. Consequently, super‐foldable batteries remain unexplored. This work focused on sodium‐ion batteries as a breakthrough point to advance super‐foldable devices. By employing a “2+1” bioinspired strategy, we stepwise designed and assembled super‐foldable components, from substrates to electrodes, and to ultimately device. This bioinspired approach completely disperses folding stress and thus prevents the breakage of chemical bonds, enabling the successful fabrication of the first super‐foldable ion battery. This battery can withstand true‐folding at any angle, in any direction, and for an unprecedented number of cycles—far outperforming current foldable phones with hinge structures. Remarkably, after 500,000 true‐folding cycles, the battery's microstructure remains intact with no significant degradation of electrochemical performance. Real‐time dynamic folding observations reveal an M‐shaped folding structure within the bioinspired materials, which effectively disperses stress via bulged layers, dispersed arcs, and slidable microgrooves that work together across different directions and dimensions to achieve super‐foldability. Mechanical simulations vividly verify this principle. This work represents a breakthrough in super‐foldable devices, offering valuable insights and promoting practical application for future super‐foldable devices.

Sustaining 500,000 Folding Cycles Through Bioinspired Stress Dispersion Design in Sodium-Ion Batteries.

Developing super-foldable electronic materials and devices presents a significant challenge, as intrinsic conductive materials are unable to achieve numerous true-folding operations (super-foldable) due to limitations from short-range forces of chemical bonds. Consequently, super-foldable batteries remain unexplored. This work focused on sodium-ion batteries as a breakthrough point to advance super-foldable devices. By employing a "2+1" bioinspired strategy, we stepwise designed and assembled super-foldable components, from substrates to electrodes, and to ultimately device. This bioinspired approach completely disperses folding stress and thus prevents the breakage of chemical bonds, enabling the successful fabrication of the first super-foldable ion battery. This battery can withstand true-folding at any angle, in any direction, and for an unprecedented number of cycles-far outperforming current foldable phones with hinge structures. Remarkably, after 500,000 true-folding cycles, the battery's microstructure remains intact with no significant degradation of electrochemical performance. Real-time dynamic folding observations reveal an M-shaped folding structure within the bioinspired materials, which effectively disperses stress via bulged layers, dispersed arcs, and slidable microgrooves that work together across different directions and dimensions to achieve super-foldability. Mechanical simulations vividly verify this principle. This work represents a breakthrough in super-foldable devices, offering valuable insights and promoting practical application for future super-foldable devices.

Influence of temperature and crack-tip speed on crack propagation in elastic solids.

I study the influence of temperature and the crack-tip velocity of bond breaking at the crack tip in rubber-like materials. Bond breaking is considered as a stress-aided thermally activated process and results in an effective crack propagation energy, which increases strongly with decreasing temperature or increasing crack-tip speed. This effect is particularly important for adhesive (interfacial) crack propagation but less important for cohesive (bulk) crack propagation owing to the much larger bond-breaking energies in the latter case. For adhesive cracks, the theory results are consistent with adhesion measurements for silicone rubber polydimethylsiloxane (PDMS) in contact with silica glass surfaces. For cohesive cracks, the theory agrees well with experimental results PDMS films chemically bound to silanized glass.

Investigation of Combined Aging and Mullins Stress Softening of Rubber Nanocomposites

The present study investigated the effects of thermal aging, ultraviolet radiation (UV), and stress softening on the performance properties of rubber modified with Cloisite Na+ or Cloisite 20A. Tensile strength (TS), strain at break (SB), modulus, and the retention coefficient were measured before and after aging. Results showed that TS and SB decreased by about 50% after 7 days of aging for all tested samples due to the breakage of the chemical bonds between rubber and nanoparticles. The modulus at 300% elongation increased by 20%, 15%, and 7% after thermal aging for the unmodified sample, nanocomposites with Cloisite Na+, and Cloisite 20A, respectively. The shape retention coefficient of all samples was not affected by heat, except for the virgin rubber sample, which exhibited a decrease of about 15% under thermal aging. The virgin matrix and nanocomposites showed different values of aging coefficient during thermal aging and UV radiation. The dissipated energy of samples that were aged after stretching was slightly higher than that of samples that were aged after stretching due to the breakdown of the bonds within the nanocomposites. Loading-reloading energy results showed that the level of stress softening was lower when Mullins was applied after the aging of the samples. Differential scanning calorimetry results indicated a slight decrease in Tg1 in the aged and stretched samples and an increase in the temperature of the first endothermic peak due to the addition of nanofillers in the stretched and aged samples. Thermogravimetric analysis revealed that all tested samples exhibited similar thermograms, regardless of their state of stretching or aging. Scanning electron microscopy analysis showed that the fracture surface of the virgin unaged sample was rough with some holes, while it was flatter and less rough after aging.

Theoretical Study on Intramolecular Hydrogen Bonds of Flavonoid Cocrystals.

This study investigates the role of intramolecular hydrogen bonds in the formation of cocrystals involving flavonoid molecules, focusing on three active pharmaceutical ingredients (APIs): chrysin (CHR), isoliquiritigenin (ISO), and kaempferol (KAE). These APIs form cocrystals with different cocrystal formers (CCFs) through intramolecular hydrogen bonding. We found that disruption of these intramolecular hydrogen bonds leads to decreased stability compared to molecules with intact bonds. The extrema of molecular electrostatic potential surfaces (MEPS) show that flavonoid molecules with disrupted intramolecular hydrogen bonds have stronger hydrogen bond donors and acceptors than those with intact bonds. Using the artificial bee colony algorithm, dimeric structures of these flavonoid molecules were explored, representing early-stage structures in cocrystal formation, including API-API, API-CCF, and CCF-CCF dimers. It was observed that the number and strength of dimeric interactions significantly increased, and the types of interactions changed when intramolecular hydrogen bonds were disrupted. These findings suggest that disrupting intramolecular hydrogen bonds generally hinders the formation of cocrystals. This theoretical study provides deeper insight into the role of intramolecular hydrogen bonds in the cocrystal formation of flavonoids.

Constructing surface oxygen vacancy in the [Bi2O2]2+ layer defects mediated Bi2MoO6 enhanced visible light responsive photocatalytic activity.

Bi2MoO6 nanospheres with surface oxygen vacancies (SOVs) controlled by the calcination process were prepared in this study. Performance testing revealed that the Bi2MoO6-4 sample (Bi2MoO6 calcined at 350 °C for 4h) with SOVs achieved a remarkable photocatalytic degradation efficiency up to 99.16% for Rhodamine B (RhB) within 50min, which is 2.19 times higher than that of pure Bi2MoO6. The higher photocatalytic performance of the Bi2MoO6-4 sample is attributed to the SOVs' defect level located at the Bi2MoO6 bandgap, narrowing the bandgap to effectively promote the photogenerated charge separation. The promotion of photocarrier separation and electron were transferred due to the Bi-O bond breakage in the Bi2MoO6-4 [Bi2O2]2+ layer, which mediates the defect level of SOVs in the band structure. The density functional theory calculation results reveal the possible formation site of the oxygen vacancy and the vacancy-induced defect states. This study provides a new approach for fabricating new photocatalysts with surface oxygen defects.

Preparation and Characterization of Lithraea molleoides Gum Flour and Its Blend Films

Lithraea molleoides fruit gum (LMFG) is a valuable product obtained from the total hydrolysis of the fruit. The hydrolysis process involves three methods: thermal (LMFGT), alkaline (LMFGB), and acid (LMFGA). Through these methods, the aim is to break bonds and de-esterify polysaccharides, resulting in increased solubility and decreased molecular weight. The resulting hydrolysates are then combined with pectins in a 1:2 ratio to form films. In this study, the focus is on utilizing the hydrolysates of Lithraea molleoides gums for film applications, with an evaluation of their structural and physicochemical characteristics. The films produced exhibit excellent mechanical properties and low water vapor permeability, as well as exceptional thermal stability. These properties make them highly suitable for industrial films in pharmaceutical and food applications. This research highlights the potential of LMFG-based films as a viable solution for various industrial needs due to their outstanding performance across multiple parameters.

Study on the uniaxial tensile mechanical behavior of two-dimensional single-crystal aluminum nitride

Abstract To investigate the tensile behavior and mechanical properties of single-crystal aluminum nitride (AlN) at the microscopic level, molecular dynamics simulations were used to study the effects of crystal orientation, strain rate, environmental temperature, and hole defect size on fracture strength, fracture mechanism, and potential energy during uniaxial tensile. The results show that the tensile strength of AlN in the [100] crystal direction is stronger. The anisotropic behavior characteristics of Al-N bonds fracture mechanism, crack growth rate, and cracking degree are significant when stretched along the [100], [010], and [110] crystal directions. Under high temperature condition, the lattice structure undergoes changes, causing grain boundaries to move and slip. This facilitates the breaking of bonds, leading to a decrease in tensile strength and a reduction in stored potential energy. Hole defects cause more lattice damage, reducing the energy required for Al-N bonds breakage and facilitating the propagation of microcracks. Additionally, it was found that the strain rate affects the stress–strain behavior of the model. An increase in strain rate leads to an increase in breaking stress, and the rapid deformation of AlN results in more energy being stored in the lattice in the form of potential energy. Therefore, the tensile strength and potential energy are improved.

Carbodicarbene‐Stibenium Ion‐Mediated Functionalization of C(sp3)−H and C(sp)−H Bonds

AbstractMain‐group element‐mediated C−H activation remains experimentally challenging and the development of clear concepts and design principles has been limited by the increased reactivity of relevant complexes, especially for the heavier elements. Herein, we report that the stibenium ion [(pyCDC)Sb][NTf2]3 (1) (pyCDC=bis‐pyridyl carbodicarbene; NTf2=bis(trifluoromethanesulfonyl)imide) reacts with acetonitrile in the presence of the base 2,6‐di‐tert‐butylpyridine to enable C(sp3)−H bond breaking to generate the stiba‐methylene nitrile complex [(pyCDC)Sb(CH2CN)][NTf2]2 (2). Kinetic analyses were performed to elucidate the rate dependence for all the substrates involved in the reaction. Computational studies suggest that C−H activation proceeds via a mechanism in which acetonitrile first coordinates to the Sb center through the nitrogen atom in a κ1 fashion, thereby weakening the C−H bond which can then be deprotonated by base in solution. Further, we show that 1 reacts with terminal alkynes in the presence of 2,6‐di‐tert‐butylpyridine to enable C(sp)−H bond breaking to form stiba‐alkynyl adducts of the type [(pyCDC)Sb(CCR)][NTf2]2 (3 a–f). Compound 1 shows excellent specificity for the activation of the terminal C(sp)−H bond even across alkynes with diverse functionality. The resulting stiba‐methylene nitrile and stiba‐alkynyl adducts react with elemental iodine (I2) to produce iodoacetonitrile and iodoalkynes, while regenerating an Sb trication.

Carbodicarbene-Stibenium Ion-Mediated Functionalization of C(sp3)-H and C(sp)-H Bonds.

Main-group element-mediated C-H activation remains experimentally challenging and the development of clear concepts and design principles has been limited by the increased reactivity of relevant complexes, especially for the heavier elements. Herein, we report that the stibenium ion [(pyCDC)Sb][NTf2]3 (1) (pyCDC=bis-pyridyl carbodicarbene; NTf2=bis(trifluoromethanesulfonyl)imide) reacts with acetonitrile in the presence of the base 2,6-di-tert-butylpyridine to enable C(sp3)-H bond breaking to generate the stiba-methylene nitrile complex [(pyCDC)Sb(CH2CN)][NTf2]2 (2). Kinetic analyses were performed to elucidate the rate dependence for all the substrates involved in the reaction. Computational studies suggest that C-H activation proceeds via a mechanism in which acetonitrile first coordinates to the Sb center through the nitrogen atom in a κ1 fashion, thereby weakening the C-H bond which can then be deprotonated by base in solution. Further, we show that 1 reacts with terminal alkynes in the presence of 2,6-di-tert-butylpyridine to enable C(sp)-H bond breaking to form stiba-alkynyl adducts of the type [(pyCDC)Sb(CCR)][NTf2]2 (3 a-f). Compound 1 shows excellent specificity for the activation of the terminal C(sp)-H bond even across alkynes with diverse functionality. The resulting stiba-methylene nitrile and stiba-alkynyl adducts react with elemental iodine (I2) to produce iodoacetonitrile and iodoalkynes, while regenerating an Sb trication.

Molecular Dynamics Investigation of the Influenza Hemagglutinin Conformational Changes in Acidic pH.

The surface protein hemagglutinin (HA) of the influenza virus plays a pivotal role in facilitating viral infection by binding to sialic acid receptors on host cells. Its conformational state is pH-sensitive, impacting its receptor-binding ability and evasion of the host immune response. In this study, we conducted extensive equilibrium microsecond-level all-atom molecular dynamics (MD) simulations of the HA protein to explore the influence of low pH on its conformational dynamics. Specifically, we investigated the impact of protonation on conserved histidine residues (H1062) located in the hinge region of HA2. Our analysis encompassed comparisons between nonprotonated (NP), partially protonated (1P, 2P), and fully protonated (3P) conditions. Our findings reveal substantial pH-dependent conformational alterations in the HA protein, affecting its receptor-binding capability and immune evasion potential. Notably, the nonprotonated form exhibits greater stability compared to protonated states. Conformational shifts in the central helices of HA2 involve outward movement, counterclockwise rotation of protonated helices, and fusion peptide release in protonated systems. Disruption of hydrogen bonds between the fusion peptide and central helices of HA2 drives this release. Moreover, HA1 separation is more likely in the fully protonated system (3P) compared to nonprotonated systems (NP), underscoring the influence of protonation. These insights shed light on influenza virus infection mechanisms and may inform the development of novel antiviral drugs targeting HA protein and pH-responsive drug delivery systems for influenza.

The Role of Frustrated Lewis Pair in Catalytic Transfer Hydrogenation of Furfural using Nickel Single-Atom Catalysts: A Theoretical Study.

The burgeoning field of frustrated Lewis pair (FLP) heterogeneous catalysts has garnered significant interest in recent years, primarily due to their inherent ability to activate H-source molecules, thereby facilitating hydrogenation reactions. In this study, non-precious transition metal atoms were anchored onto several models of pyridinic nitrogen incorporated graphene sheet. Theoretical calculations substantiated energy barriers as low as 0.10 eV for isopropanol activation, thereby positioning these catalysts as highly promising candidates for catalytic transfer hydrogenation of furfural. Electronic structure analyses revealed that the H-O bond breakage in isopropanol molecules was significantly facilitated by the presence of FLP sites within the catalysts. Notably, both Ni-C2N and Ni-N6-C demonstrated exceptional potential as selective catalysts for the hydrogenation of furfural into furfuryl alcohol, exhibiting remarkably low barriers of only 0.65-0.72 eV for the rate-determining steps. The findings in this study are helpful to design FLP containing single atom catalysts for hydrogenation reactions.

Auricularia Auricula Polysaccharide-Mediated Green Synthesis of Highly Stable Au NPs

Polysaccharide-functionalized gold nanoparticles (Au NPs) exhibit a promising application in biomedical fields due to their excellent stability and functional properties. The Au NPs from Auricularia auricula polysaccharide (AAP) were successfully synthesized using a straightforward method. By controlling the mass fraction of AAP, pH, reaction temperature, reaction time, and concentration of gold precursor, the highly dispersed spherical AAP-functionalized Au NPs (AAP-Au NPs) were prepared. The Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS) indicated that the synthesis mechanism of AAP-Au NPs was as follows: the molecular chain of AAP undergoes a glycosidic bond breakage to expose the reduction terminus in the presence of gold precursor, which reduced Au(III) to Au(0), and itself was oxidized to carboxylate compounds for maintaining the stability of AAP-Au NPs. Additionally, based on the electrostatic interactions and steric forces, as-prepared AAP-Au NPs exhibit excellent stability at various pH (5–11), temperature (25–60 °C), 5 mmol/L glutathione, and 0.1 mol/L Na+ and K+ solutions. Furthermore, AAP-Au NPs retained the ability to scavenge DDPH and ABTS radicals, which is expected to expand the application of Au NPs in biomedical fields.

Sibling presence during fostering ameliorates endocrine stress profile changes in a social rodent species (Octodon degus) in a sex-specific manner

During early life, disruption of the parent-offspring bond can substantially impact development of offspring physiology and behavior. In rodents, it has been well-documented that parental separation, reduction in parental care, and cross-fostering can affect development of the endocrine stress response. For social species, however, several social factors may mitigate the stress of cross-fostering, such as remaining with other known adult caregivers or siblings. In this study, we cross-fostered a social rodent species (Octodon degus) with or without their siblings at postnatal day (PND) 8 and measured their endocrine stress response immediately after fostering (PND9) and at weaning (PND28). We found that female singly-fostered offspring displayed elevated baseline cortisol levels and reduced weight gain immediately after fostering. At weaning, female singly-fostered offspring continued to display elevated baseline cortisol levels compared to non-fostered female offspring, while singly-fostered males demonstrated weaker cortisol negative feedback strength compared to male offspring that were not fostered or were fostered with their siblings. These results suggest that sibling presence may help mitigate the stress of fostering, and that future studies should further examine other social conditions that may help reduce developmental consequences of long-term parental bond disruption.

Study on the damage characteristics of high-temperature superconducting cable insulation under air gap discharge

This study explores the impact of small air gaps in high-temperature superconducting cables on the insulating material polypropylene-laminated paper (PPLP), and the aging rules and mechanisms of the insulating material during practical uses. An air gap discharge test platform was built to simulate air gap fault defects of superconducting cables in the real operating environment. Hierarchical clustering method was used to divide the gap discharge process of defect model into four stages. Insulation damage assessment was conducted on the intermediate layer PP of the superconducting insulation material PPLP at different discharge stages, revealing surface changes and periodic alterations in dielectric properties. The morphological features, roughness, infrared spectra, dielectric loss, surface resistivity, and other phase characteristics of the superconducting insulation layer material were analyzed at different stages of air gap defects. Molecular group cracking in PP was attributed to the bond breakage on the main chain. These findings provide insights into high-temperature superconducting cable insulation under air gap discharge and provide a guideline for practical applications in semi-conductive industries.

Significance analysis of the attenuation coefficient of vibrations in a boron nitride–carbon nanotube under buckling and fracture: A molecular dynamics study

Boron nitride–carbon nanotubes (BN–CNTs), serving as nanomass sensors, exhibit fatigue characteristics, such as buckling or bond breakage, under impact from measured particles. However, the impact of such damage on the functionality of BN–CNTs remains unclear. Here, we use molecular dynamics simulations to investigate the performance of BN–CNTs mass sensors under impact by C60 particles, focusing on three critical states: buckling, bond breakage, and coexisting buckling and bond breakage. An analysis of the impact stress and mass responsivity shows that damaged beams have a lower mass detection capability than undamaged beams. The results of a paired t-test and an analysis of the decay coefficients and vibration frequencies of damaged nanobeams show that damaged nanobeams have a significantly lower quality factor than undamaged nanobeams. We use an energy equation to analyze the impact process of nanobeams for the first time, revealing that the change in the potential energy of the beam is a crucial influence factor of the beam critical state. This study provides insights into the damage to nanoscale mass sensors caused by impact.

Synthesis and Bioactivity Assessment of N-Aryl-Azasesamins

Sesamin, a tetrahydrofuran lignan, has gained significant attention over the past few decades due to its versatile medicinal activities. However, until now, the research on sesamin analogues has not been explored extensively. In this study, a series of new N-aryl-azasesamins were synthesized for the first time using sesamin as a raw material. The mechanism of the key breakage of the ethereal bond of the tetrahydrofuran ring in sesamin has been studied. The configuration of C6 in N-aryl-azasesamins was confirmed through NMR and X-ray single crystal refraction analyses. The results showed that the configuration of N-aryl-azasesamins was opposite to sesamin in C6. Subsequently, the N-aryl-azasesamins were evaluated for their antifungal and antitumor activities via micro-broth dilution and MTT assays. It was observed that none of the N-aryl-azasesamins exhibited inhibitory activity against the growth of C. albicans and C. neoformans at a concentration of 100 μg/mL. Most analogues showed no activity against HepG2 cells. However, 21c and 21k demonstrated antitumor activity after 24 h of incubation with IC50 values of 6.49 μM and 4.73 μM, respectively. These results suggest that some N-aryl-azasesamins exhibit significantly enhanced antitumor activity compared with sesamin.

Tailored Regulation of Graphite Microcrystals via Tandem Catalytic Carbonization for Enhanced Electrochemical Performance of Hard Carbon in the Low‐Voltage Plateau

AbstractThe sodium storage behavior in the plateau region is crucial for determining the capacity and rate capability of hard carbon (HC) anodes in sodium‐ion batteries (SIBs). Key structural features for achieving excellent plateau performance include extended graphite domains and increased interlayer spacing. However, synchronously optimizing these two structures is challenging due to their inherent trade‐off. Herein, a tandem catalytic carbonization strategy is developed to construct HC with long graphite domains (La = 5.31 nm) and large interlayer spacing (d002 = 0.389 nm) simultaneously. Comprehensive in situ and ex situ tests unravel the catalytic selective bond breaking and aromatization effects of ZnCl2, the catalytic graphitic layers enlargement and occupied effects of formed ZnO and Zn in different temperature stages, leading to the formation of the unique structure. The optimal HCZ‐0.1 exhibits a high reversible capacity of 346.9 mAh g−1 with a plateau capacity of 249.4 mAh g−1, and high‐rate performance (114.0 mAh g−1 at 5 A g−1). In addition, the sodium storage mechanism and origin of enhanced Na+ kinetics of HCZ‐0.1 are also revealed. This work offers a precise method to engineer the graphite microcrystal structure in HC for superior sodium storage in the plateau region.