Types Of Bonds Research Articles

Enhancing NH3-SCR denitrification performance through synergistic A- and B-site effects via CeFe modification of LaMnO3

ABO3 type perovskite catalysts are widely used in NH3-SCR to remove NOx due to excellent low-temperature reduction performance. To study the synergistic effect of A and B sites on the structure, morphology and redox performance of modified perovskite catalysts (La1-xCexMn1-yFeyO3), LaMnO3 perovskite catalysts were co-doped with CeFe by sol-gel method, and the crystal structure, surface chemical environment, optimal metal co-doping ratio and surface adsorption of the modified perovskite catalysts were clarified through various characterizations. In addition, through first-principles calculations, the differential charge density and binding energy of each doping system were analyzed, the relationship between the difficulty of Ce doping and the electronic population of Mn atoms and the redox ability of the catalyst was discussed, and the key bond types and their changing rules in perovskite catalytic reduction were clarified. The results showed that co-doping Ce and Fe could improve the denitrification efficiency and sulfur resistance of the catalyst. When the Fe doping ratio is 0.1, the denitrification activity is the highest. Among them, the La0.9Ce0.1Mn0.9Fe0.1O3 catalyst showed the most favorable active acid site distribution and the best reduction performance, which was conducive to the adsorption and redox of gas molecules on the catalyst surface. At the same time, when the A and B sites were co-doped, the electron transferred mainly occurs between Ce ions and Fe ions, forming a synergistic effect and changing the covalent components between Mn-O and Fe-O bonds. This made the valence states of Mn and Fe ions more, enhanced the catalytic activity of perovskite, and promoted the redox of NO on the catalyst surface, thus providing a new idea for the redox reaction pathway of modified perovskite catalysts.

The Influence and Mechanisms of Natural Plant Polysaccharides on Intestinal Microbiota-Mediated Metabolic Disorders

Natural plant polysaccharides are renowned for their broad spectrum of biological activities, making them invaluable in both the pharmaceutical and food industries. Their safety, characterized by low toxicity and minimal side effects, coupled with their potential therapeutic properties, positions them as crucial elements in health-related applications. The functional effectiveness of these polysaccharides is deeply connected to their structural attributes, including molecular weight, monosaccharide components, and types of glycosidic bonds. These structural elements influence how polysaccharides interact with the gut microbiota, potentially alleviating various metabolic and inflammatory disorders such as inflammatory bowel disease, diabetes, liver-associated pathologies, obesity, and kidney diseases. The polysaccharides operate through a range of biological mechanisms. They enhance the formation of short-chain fatty acids, which are pivotal in keeping intestinal health and metabolic balance. Additionally, they strengthen the intestinal mucosal barrier, crucial for deterring the ingress of pathogens and toxins into the host system. By modulating the immune responses within the gut, they help in managing immune-mediated disorders, and their role in activating specific cellular signaling pathways further underscores their therapeutic potential. The review delves into the intricate structure–activity relationships of various natural polysaccharides and their interactions with the intestinal flora. By understanding these relationships, the scientific community can develop targeted strategies for the use of polysaccharides in therapeutics, potentially leading to innovative treatments for a range of diseases. Furthermore, the insights gained can drive the advancement of research in natural polysaccharide applications, providing direction for novel dietary supplements and functional foods designed to support gut health and overall well-being.

Cross-Electrophile Coupling: Principles, Methods, and Applications in Synthesis.

Cross-electrophile coupling (XEC), defined by us as the cross-coupling of two different σ-electrophiles that is driven by catalyst reduction, has seen rapid progression in recent years. As such, this review aims to summarize the field from its beginnings up until mid-2023 and to provide comprehensive coverage on synthetic methods and current state of mechanistic understanding. Chapters are split by type of bond formed, which include C(sp3)-C(sp3), C(sp2)-C(sp2), C(sp2)-C(sp3), and C(sp2)-C(sp) bond formation. Additional chapters include alkene difunctionalization, alkyne difunctionalization, and formation of carbon-heteroatom bonds. Each chapter is generally organized with an initial summary of mechanisms followed by detailed figures and notes on methodological developments and ending with application notes in synthesis. While XEC is becoming an increasingly utilized approach in synthesis, its early stage of development means that optimal catalysts, ligands, additives, and reductants are still in flux. This review has collected data on these and various other aspects of the reactions to capture the state of the field. Finally, the data collected on the papers in this review is offered as Supporting Information for readers.

Quasi-2D crystals as an electrode material for high energy storage devices

The high value of the specific surface area in quasi-2D crystals, with the possibility of a large variation of their properties due to external factors, allows us to consider them as electrode materials for supercapacitors. In order to describe the specific physical properties of such crystals due to the different types of chemical bonds in them, a model is proposed. The electronic spectrum obtained has the structure (discrete levels) + (two-dimensional bands) or (mini-bands) + (two-dimensional bands). A significant relationship between the geometrical, spectral and statistical properties of the quasi-2D crystals has been found by studying the energy density of the accumulation W within the microscopic model. Contrary to existing models, the proposed model shows that under certain conditions there are two or more optimal crystal sizes where the experimentally observed maximum energy density W is realised. The model and its qualitative conclusions should be considered as the result of a microscopic approach to the problem.

Pressure-induced structural and electronic properties of inorganic halide perovskite CsPbBr3

In this paper, Density Functional Theory (DFT) based on first principles is used to study the influence of pressure on the structural and electronic properties of the cubic and orthorhombic phases of halogen perovskite CsPbBr3. We observe that the lattice constant of the cubic phase shows a monotonically decreasing trend in a wide pressure range, while the Pb–Br irregular octahedron of the orthorhombic phase rotates under pressure and distorts at 65.5 GPa, 67 GPa, 69.5 GPa, and 70 GPa pressure points, respectively. Moreover, the pressure has a good adjustment effect on the band gap of the cubic and orthorhombic phases. The band gap of the orthorhombic phase changes between the direct band gap and the indirect band gap under pressure. The charge difference density and density of states are calculated to study the type of bonds between internal atoms and the effect of pressure on the distribution of orbital electrons. The study of the Crystal Orbital Hamilton Populations and lattice energy of the electron cloud shows that the pressure has a significant adjustment effect on the strength of the Pb–Br covalent bond and the Cs–Br ionic bond. These results provide a comprehensive reference and guidance for the further research and application of perovskite material pressure engineering.

Perturbational and variational energy decomposition analysis on hydrogen bonds of coordinated glycine with water molecule.

Three types of hydrogen bonds of coordinated glycine and water had been investigated: NH/O of α-amino group, O1/HO involving oxygen coordinated to the metal ion (O1), and O2/HO involving α-carbonyl oxygen (O2). Various glycine complexes were investigated: octahedral cobalt(III) and nickel(II), square pyramidal copper(II), and square planar copper(II), palladium(II), and platinum(II) complexes. Nature of these three hydrogen bond types was analysed using symmetry-adapted perturbation theory (SAPT) and variational energy decomposition analysis (EDA) method (TPSS-D3/def2-TZVPP). The results of the EDA decomposition are in good agreement with the reliable SAPT2+3/def2-TZVPP and its total interaction values with CCSD(T)/CBS energies. Electrostatic interaction is generally the dominant attractive energy term in most of the interactions, followed by orbital relaxation, and lastly dispersion as the weakest. We compared EDA results of various complexes to determine the effects of complex charge, metal oxidation, coordination, and atomic number on the energy decomposition terms. The complex charge influences the values of decomposition terms the most, followed by metal oxidation and coordination number, while atomic number effects them the least. All complex and metal changes have a more significant effect on the results of NH/O and O1/HO then O2/HO interactions, due to its location further away from the metal ion.

Covalent vs. Dative Bonding in Carbon Monoxide and Other 10-Valence-Electron Diatomics.

Valence bond theory (VB) was used to determine the extent and driving forces for covalent vs. dative bonding in 10-valence-electron diatomic molecules N2, CO, NO+, CN-, P2, SiS, PS+, and SiP-. VBSCF calculations were performed at the CCSD(T)/cc-pVDZ optimized geometries. The full triply bonded system included 20 VB structures. A separation of the σ and π space allowed for a subdivision of the full 20 structure set into sets of 8 and 3 for the π and σ systems, respectively. The smaller structure sets allowed for a more focused look at each type of bond. In situ bond energies for σ bonds, individual π bonds, the π system, and triple bonds follow expected trends. Our data shows that N2 and P2 have three covalent bonds whereas CO and SiS contain two covalent and one dative bond, and charged species NO+, CN-, PS+, and SiP- are a mixture of N2 and CO type electronic arrangements, resulting in a nearly equal charge distribution. Dative bonds prefer to be in the π position due to enhanced σ covalency and π resonance. Both σ and π resonance energies depend on a balance of ionic strength, orbital compactness, σ constraints, and bond directionality. Resonance energy is a major contributor to bond strength, making up more than 50% of the π bonds in SiS and PS+ (charge-shift bonds), and is greater than charge transfer in dative bonds.

Self-healing electronic skin with high fracture strength and toughness

Human skin is essential for perception, encompassing haptic, thermal, proprioceptive, and pain-sensing functions through ion movement. Additionally, it is mechanically resilient and self-healing for protection. Inspired by these unique properties, researchers have attempted to develop stretchable, self-healing sensors based on ion dynamics. However, most self-healing sensors reported to date suffer from low fracture strength and toughness. In this work, we present an ion-based self-healing electronic skin with exceptionally high fracture strength and toughness. We enhanced self-healing polymers and ionic conductors by introducing two types of orthogonal dynamic crosslinking bonds: dynamic aromatic disulfide bonds and 2-ureido-4-pyrimidone moieties. These dynamic bonds provide autonomous self-healing and high mechanical toughness even in the presence of ionic liquids. As a result, our self-healing polymer and self-healing ionic conductor exhibit remarkable stretchability (700%, 850%), fracture strength (34 MPa, 30 MPa), and toughness (78.5 MJ/m3, 87.3 MJ/m3), the highest values reported among self-healing ionic conductors to date. Using our materials, we developed various fully self-healing sensors and a soft gripper capable of autonomously recovering from mechanical damage. By integrating these components, we created a comprehensive self-healing electronic skin suitable for soft robotics applications.

Crystal structures of two polymorphs for fac-bromidotricarbonyl[4-(4-methoxyphenyl)-2-(pyridin-2-yl)thiazole-κ2 N,N′]rhenium(I)

Crystallization of the title compound, fac-[ReBr(ppt-OMe)(CO)3] (ppt-OMe = C15H12N2OS), from CH2Cl2/n-pentane (1:5 v/v) at room temperature gave two polymorphs, which crystallize in monoclinic (P21/c; α form) and orthorhombic (Pna21; β form) space groups. The ReI complex molecules in either polymorph adopt a six-coordinate octahedral geometry with three facially-oriented carbonyl ligands, one bromido ligand, and two nitrogen atoms from one chelating ligand ppt-OMe. In the crystal, both polymorph α and β form di-periodic sheet-like architectures supported by multiple hydrogen bonds. In polymorph α, two types of hydrogen bonds (C—H...O) are found while, in polymorph β, four types of hydrogen bonds (C—H...O and C—H...Br) exist.

Electron transport and quantum phase transitions in cumulene-connected C80H20 fulleryne: DFT and tight-binding studies

Molecular bridges are opening up exciting new applications in diverse fields, improving the efficiency of conductive inks, enhancing the performance of devices such as organic light-emitting diodes and low-cost solar cells, and advancing the development of highly sensitive sensors, chemical reactions, drug delivery systems, and more. In this paper, we study the electron transport properties of a C80H20 fulleryne (dodecahedryne) connected to two cumulene electrodes. Using density functional theory (DFT), we determine the optimal molecular bridge structure. Based on the IR vibration spectra, different stable phases of the molecular bridge are obtained. The corresponding tight-binding (TB) parameters of the cage are obtained by assigning appropriate values of the length and type of bonds for the fulleryne cage through matching the HOMO-LUMO gap between the DFT calculations and the TB parameters. The electron transport for the desired structures is investigated using the obtained tight-binding parameters and the non-equilibrium Green's function (NEGF) method. Finally, it is concluded that among the five possible configurations for the cumulene-dodecahedryne -cumulene molecular bridge, only one specific configuration—where the electrodes are one edge apart—exhibits metallic behavior, while other positions act as insulators. In addition, the system exhibits quantum phase transitions from metal to semiconductor and from insulator to metal in the presence of critical electric fields. The ability to control quantum phase transitions in these molecular systems can be leveraged to develop qubits for quantum computing. The unique properties can be utilized to design advanced molecular electronic devices.

Preparation and characterization of Tobacco polysaccharides and its modulation on hyperlipidemia in high-fat-diet-induced mice.

This study aimed to investigate the structural properties of tobacco polysaccharide (TP) and its mechanism of modulating hyperlipidemia in high-fat diet-induced mice. The structural properties of TP were characterized by FT-IR, 1HNMR, SEM, AFM and thermogravimetric analysis. And the regulatory mechanism of TP on lipid metabolism was investigated in hyperlipidemia mice. These results showed that TP had a high composition of reducing monosaccharide and the glycosidic bond type was α-glycosidic bond. The intervention by TP resulted in a significant reduction of body weight and improvement in lipid accumulation. And the modulation mechanism by which TP ameliorated the abnormalities of lipid metabolism was associated with the expression levels of lipid metabolism-related genes and serum exosomes miRNA-128-3p, as well as the modulation of structure and abundance of the gut microbiota in mice. In addition, TP treatment significantly increased the content of short-chain fatty acids (SCFAs) in mice feces. The results of molecular docking and dual-luciferase assay exhibited a good interaction between propionic acid and PPAR-α, and it was hypothesized that the interaction might further ameliorate the hyperlipidemia. Therefore, TP can regulate the expression levels of lipid metabolism-related genes through miRNAs from serum exosomes and SCFAs from gut microbiota.

Synthesis of a Pd2L4 Hydrazone Molecular Cage Through Multiple Reaction Pathways.

Molecular cages are preorganized molecules with a central cavity, typically formed through the reaction of their building blocks through chemical bonds. This requires, in most cases, forming and breaking reversible bonds during the cage formation reaction pathway for error correction to drive the reaction to the cage product. In this work, we focus on both Pd-ligand and hydrazone bonds implemented in the structure of a Pd2L4 hydrazone molecular cage. As the cage contains two different types of reversible bonds, we envisaged a cage formation comparative study by performing the synthesis of the cage through three different reaction pathways involving the formation of Pd-ligand bonds, hydrazone bonds, or a combination of both. The three reaction pathways produce the cage with yields ranging from 73% to 79%. Despite the complexity of the reaction, the cage is formed in a high yield, even for the reaction pathway that involves the formation of 16 bonds. This research paves the way for more sophisticated cage designs through complex reaction pathways.

Liquidity and cost advantage of green bonds

The prevailing scholarly consensus suggests that green bonds benefit from a “green premium” by offering a financing cost advantage over conventional bonds. However, our empirical study reveals significant differences in liquidity between green and conventional bonds that could affect this cost advantage. We investigate the variations in liquidity levels between these bond types and explore how these disparities influence the advantage in financing costs associated with green bonds. The findings show that, due to their unique attributes, green bonds tend to have lower liquidity than conventional bonds; this results in higher liquidity costs, which counterbalance the cost benefits of the green premium. The liquidity disadvantage of green bonds thus weakens the overall financing cost advantage they might otherwise offer through the green premium.

Investigation on Ti3AlC2/TiC interfacial properties: Experiment and first-principles calculation

The (Ti3AlC2+Al2O3)p/Al3Ti composite was fabricated through hot pressing. The Ti3AlC2(0001)/TiC(111) interface in the (Ti3AlC2+Al2O3)p/Al3Ti composite was clearly observed, and its interface properties were conducted using first-principles calculations. The results show that: for the TiC(111) surface, the surface energy of Ti-terminated TiC(111) is lower than that of C-terminated TiC(111), indicating that Ti-terminated TiC(111) is more stable. For the Ti3AlC2(0001) surface, surface energy from high to low is: C-terminated > Ti(Al)-terminated > Ti(C)-terminated > Al-terminated Ti3AlC2(0001) surfaces in environments of Ti-rich and Al-rich, while the stability is opposite. Among the 24 interface models, Ti(Al)-on-top-C1 has the highest work of adhesion (13.1552 J/m2) and the lowest interface energy (−3.3553 J/m2), indicating the best interface bonding strength and stability. During the relaxation process, the stacking sites of the three interface models, which were named C-hcp-hollow-C2, C-fcc-rollow-C3, and Ti(Al)-on-top-C1, changed. By analyzing the electronic structure of eight interface models, it was found that covalent and metal bonds form at the interface, such as Ti-C covalent bond, Al-C covalent bond, C-C covalent bond, and Ti-Ti metallic bond. This indicates that the type of chemical bonds at the Ti3AlC2(0001)/TiC(111) interface is determined by the TiC(111) surface termination and Ti3AlC2(0001) surface termination. In the first-principles tensile test, the critical strain and ultimate tensile strength of the Ti(Al)-on-top-C1 interface model are 8 % and 23.55 GPa, respectively.

Two-Factor Rule for Distinguishing the Covalent and Tetrel Bonds.

Understanding and exploring the existence of a recognizable boundary between the noncovalent tetrel bond (TtB) and the coordination or weakened covalent bond are important for the bonding characterization. We have developed a simple methodology for analysing the type of bonds based on comparison of the electrostatic and total static potentials along the bond line. For the typical σ-hole noncovalent bond formed by a Tt atom in a tetrahedral molecule, we have found that the space gap between positions of the maxima of the total static potential and the negative quantity of electrostatic potential is much wider than that for the coordination bonds in a trigonal bipyramid molecular system for the Cl-Tt/Cl…Tt and N-Tt/N…Tt (Tt = C, Si, Ge) bonds in molecules and molecular complexes. The distinction between the weakened covalent and strengthened noncovalent bonds is well reflected in behaviour of the Fermi hole along the bond line. Two-factor empirical rule based on the superposition of the electrostatic and total static potentials is suggested.

Durability of epoxy and vinyl ester polymers in wet, seawater, and seawater sea sand concrete environments: Molecular dynamics simulations

Epoxy and vinyl ester (VE) deteriorate under harsh environmental conditions typical of marine and offshore applications. Enhancing their performance requires a deeper understanding of their molecular-level interactions with these environments. This study uses molecular dynamics simulations to investigate the behavior of epoxy and VE under dry, wet, Na2SO4, NaCl, NaOH, KOH, and simulated seawater sea sand concrete (SWSSC) pore solution environments. The effect of temperatures ranging from 300 K to 368 K was also explored. Key parameters, such as radial distribution function, hydrogen bond dynamics, diffusion coefficients of water molecules and ions, swelling ratio, and glass transition temperature (Tg), were analyzed. Results show that epoxy is more sensitive to environmental effects than VE. In the dry state, three types of hydrogen bonds (H-bonds) were identified, with 64 % of the hydroxyl (OH) group involved in epoxy and 34 % in VE. As temperature increases, polymer chain interactions weaken, leading to a decrease in H-bonds, with epoxy showing a faster decline. Absorbed water molecules accumulate near the polymer polar sites, particularly at the OH groups, breaking some polymer-polymer H-bonds and forming new ones with the polymer polar sites. The hydrogen atoms of most absorbed water molecules orient away from the OH group, creating binding sites for water clustering through water-water H-bonds, leading to plasticization and potential hydrolytic degradation. Ions increase the number of polymer-water H-bonds, significantly decreasing polymer-polymer H-bonds (by 59.22 % for epoxy and 51.52 % for VE in SWSSC), thus accelerating material deterioration. Free volume distribution and dynamics, the transition between bound and free water, hydrogen bond dynamics, as well as ion hydration and dehydration collectively influence the water diffusion process in the polymer networks. Ion species diffuse much slower than water molecules, with epoxy showing higher permeability to Cl- and OH- compared to VE. Glass transition temperature (Tg) of both polymers is sensitive to environmental exposure, with epoxy being more affected. The detrimental effect on Tg is ranked as SWSSC > KOH > NaOH > NaCl > Na2SO4 > Wet. These findings provide new nanoscale insights into the interactions between polymers and SWSSC environments, offering a foundation for accurately predicting the durability of polymer-reinforced SWSSC.

Development and applications of enzymatic peptide and protein ligation.

Chemical synthesis of complex peptides and proteins continues to play increasingly important roles in industry and academia, where strategies for covalent ligation of two or more peptide fragments to produce longer peptides and proteins in convergent manners have become critical. In recent decades, efficient and site-selective ligation strategies mediated by exploiting the biocatalytic capacity of nature's diverse toolkit (i.e., enzymes) have been widely recognized as a powerful extension of existing chemical strategies. In this review, we present a chronological overview of the development of proteases, transpeptidases, transglutaminases, and ubiquitin ligases. We survey the different properties between the ligation reactions of various enzymes, including the selectivity and efficiency of the reaction, the ligation "scar" left in the product, the type of amide bond formed (natural or isopeptide), the synthetic availability of the reactants, and whether the enzymes are orthogonal to another. This review also describes how the inherent specificity of these enzymes can be exploited for peptide and protein ligation.

Biomass derived 3D N, P co-doped porous carbon incorporated with Ni-Cu bimetallic phosphide: Synergistic effect of Ni-Cu boosting Na+ storage performance

Transition metal phosphides (TMPs) as promising anode materials for sodium-ion batteries (SIBs) due to their amazing properties such as high theoretical specific capacity, various bond types and good electrical conductivity. However, TMPs are still facing poor cycling stability and unsatisfactory specific capacity, which restrict their practical application. Herein, NixCu3-xP incorporated in biomass derived 3D N, P co-doped porous carbon (NixCu3-xP-NPC) is constructed as SIB anode and the electrochemical behaviors with various Ni/Cu ratios are explored. The synergistic effect of Ni-Cu in NixCu3-xP is approved by the resulting investigation, and density functional theory (DFT) calculation further confirmed its important influence in enhancing electronic conductivity and boosting Na+ storage. Evidently, the optimum synergistic effect was observed when Ni0.15Cu2.85P/NPC is utilized for SIB anode. It exhibits a reversible specific capacity of 663 mAh g−1 after 200 cycles at 0.2 A g−1, long cycling stability (467 mAh g−1 after 1000 cycles at 1.0 A g−1), and excellent rate capability (432 mAh g−1 at 2.0 A g−1). The ex-situ X-ray diffraction and ex-situ X-ray photoelectron spectroscopy verify the combined conversion mechanism of Ni and Cu during sodiation/desodiation processes, which is greatly favorable for high specific capacity and cycling stability.

Self‐healing polymers in rigid and flexible perovskite photovoltaics

AbstractOver the past 10 years, perovskite solar cell (PSC) device technologies have advanced remarkably and exhibited a notable increase in efficiency. Additionally, significant innovation approaches have improved the stability related to heat, light, and moisture of PSC devices. Despite these developments in PSCs, the instability of PSCs is a pressing problem and an urgent matter to overcome for practical application. Recently, polymers have been suggested suggestion has been presented to solve the instability issues of PSCs and increase the photovoltaic parameters of devices. Here, first, the fundamental chemical bond types of self‐healing polymers are presented. Then, a comprehensive presentation of the ability of self‐healing polymers in rigid and flexible PSCs to enhance the various physical, mechanical, and optoelectronic properties is presented. Furthermore, valuable insights and innovative solutions for perovskite‐based optoelectronics with self‐healing polymers are provided, offering guidance for future optoelectronic applications.image

Electrochemical conversion of CO2 via C−X bond formation: recent progress and perspective

With the depletion of traditional energy sources and growing environmental concerns, it is becoming increasingly urgent to develop green, low-emission renewable energy technologies to replace fossil fuel-driven methods that emit carbon dioxide (CO2). Currently, the electrochemical production of high-value-added chemicals and fuels from CO2 has aroused great interest from scientists. However, to make full use of CO2 for the preparation of chemicals, it is necessary to expand the range of electrosynthesis methods, in particular by expanding reaction pathways through the reaction of CO2 with different substrates. In general, CO2 can form new covalent bonds with substrate molecules through the formation of C−X bonds, including C−H, C−C, C−N, C−O, and C−S bonds, which would expand the range of possible products by diversifying the reaction pathway. In this review, we focus on the research progress in electrochemical conversion of CO2 through C−X bond formation. We start by examining fundamentals of the reactions and summarizing the reaction modes. Next, we discuss the electrosynthesis of C−X bonds (C−H, C−C, C−N, C−O, C−S) using CO2 and different substrate molecules. Finally, (i) strategies for the design and activity optimization of catalyst materials and (ii) the future development of forming five types of bonds from CO2 and small molecules are discussed, along with an outlook on their future research prospects.