Chemical Bonding Research Articles

Position-specific carbon stable isotope analysis of glyphosate: isotope fingerprinting of molecules within a mixture.

Glyphosate [N-(phosphonomethyl) glycine] is a widely used herbicide and a molecule of interest in the environmental sciences, due to its global use in agriculture and its potential impact on ecosystems. This study presents the first position-specific carbon isotope (13C/12C) analyses of glyphosates from multiple sources. In contrast to traditional isotope ratio mass spectrometry (IRMS), position-specific analysis provides 13C/12C ratios at individual carbon atom positions within a molecule, rather than an average carbon isotope ratio across a mixture or a specific compound. In this work, glyphosate in commercial herbicides was analyzed with only minimal purification, using a nuclear magnetic resonance (NMR) spectroscopy method that detects 1H nuclei with bonds to either 13C or 12C, and isolates the signals of interest from other signals in the mixture. Results demonstrate that glyphosate from different sources can have significantly different intramolecular 13C/12C distributions, which were found to be spread over a wide range, with δ13C Vienna Peedee Belemnite (VPDB) values of -28.7 to -57.9‰. In each glyphosate, the carbon with a bond to the phosphorus atom was found to be depleted in 13C compared to the carbon at the C2 position, by 4 to 10‰. Aminomethylphosphonic acid (AMPA) was analyzed for method validation; AMPA contains only a single carbon position, so the 13C/12C results provided by the NMR method could be directly compared with traditional isotope ratio mass spectrometry. The glyphosate mixtures were also analyzed by IRMS to obtain their average 13C/12C ratios, for comparison with our position-specific results. This comparison revealed that the IRMS results significantly disguise the intramolecular isotope distribution. Finally, we introduce a 31P NMR method that can provide a position-specific 13C/12C ratio for carbon positions with a C-P chemical bond, and the results obtained by 1H and 31P for C3 carbon agree with one another within their analytical uncertainty. These analytical tools for position-specific carbon isotope analysis permit the isotopic fingerprinting of target molecules within a mixture, with potential applications in a range of fields, including the environmental sciences and chemical forensics.

Competing CO and HCOOH Pathways in CO2 Electroreduction

AbstractHuman activities have significantly contributed to the increase in global carbon emissions, leading to adverse environmental effects such as global warming. Electrochemical reduction of carbon dioxide (CO2RR) presents a promising approach to mitigate carbon emissions. This process not only stores the low energy density renewable energies into high energy density chemical bonds, but also produces a variety of valuable products, including one‐carbon products like HCOOH and CO, as well as multi‐carbon products like CH3CH2OH and C2H4. Among them, HCOOH and CO can be produced with over 90 % selectivity on various catalysts, indicating their potential for large‐scale applications. However, the precise reaction pathways toward CO and HCOOH remain unclear, and the competition between these pathways often leads to low product selectivity. This review offers a comprehensive examination of the latest research on the selective reduction of CO2 to CO and/or HCOOH, focusing on the development of the reaction mechanisms based on theoretical simulations and experimental investigations, and the application of catalysts designed to fine‐tune CO/HCOOH selectivity. Additionally, this review highlights the challenges and prospects for the further development and understanding of selective catalysts for CO and HCOOH production, aiming to provide valuable insights for future studies in this intriguing and significant research field.

Sulfite-Assisted Acetate Conversion from CO Electroreduction.

The efficient acetate conversion from CO electroreduction is challenging due to the poor selectivity at high reaction rate, which requires the competition with H2 and other C2+ (i.e., ethylene, ethanol, n-propanol) reduction products. Electrolyte engineering is one of the efficient strategies to regulate the reaction microenvironment. In this work, the adding of sulfite (SO32-) with high nucleophilicity in KOH electrolytes was demonstrated to enable improving the CO-to-acetate conversion via generating a S-O chemical bond between SO32- and oxygenated *C2 intermediates (i.e., *CO-CO, *CO-COH) compared with that in pure KOH system on both synthesized Cu(200)- and normal commercial Cu(111)-facets-exposed metallic Cu catalysts. As a result, the prepared Cu(200)-facets-exposed metallic Cu catalyst with surface ions modification showed an superior Faradaic efficiency of 63.6% at -0.6 A·cm-2, and extraordinary absolute value of peak partial current density as high as 1.52 A·cm-2 with adding SO32- in KOH electrolytes, compared to the best reported values in both CO and CO2 electroreduction. Our work suggests an attractive strategy to introduce the oxyanion with high nucleophilicity in electrolytes to regulate the microenvironment for industrial-current-density electrosynthesis of acetate from CO electroreduction.

Potential of Molecular Catalysts with Electron-Rich Transition Metal Centers for Addressing Long-Standing Chemistry Enigmas.

Molecular complexes with electron-rich metal centers are highlighted as potential catalysts for the following five important chemical transformations: selective conversion of methane to methanol, capture and utilization of carbon dioxide, fixation of molecular nitrogen, water splitting, and recycling of perfluorochemicals. Our initial focus lies on negatively charged metal centers and ligands that can stabilize anionic metal atoms. Catalysts with electron-rich metal atoms (CERMAs) can sustain catalytic cycles with a "ping-pong" mechanism, where one or more electrons are transferred from the metal center to the substrate and back. The donated electrons can activate the chemical bonds of the substrate by populating its antibonding orbitals. At the last step of the catalytic cycle, the electrons return to the metal and the product interacts only weakly with the formed anion, which enables the solvent molecules to remove the product fast from the catalytic cycle and prevent subsequent unfavorable reactions. This process resembles electrocatalysis, but the metal serves as both an anode and a cathode (molecular electrocatalysis). We also analyze the usage of CERMAs as the base of Frustrated Lewis pairs proposing a new type of bimetallic catalysts. This Featured Article aspires to initiate systematic experimental and theoretical studies on CERMAs and their reactivity, the potential of which has probably been underestimated in the literature.

Surface Engineering of Biochar Toward Simultaneously Generating Superamphiphilicity and Catalytic Activity for Strengthening Pickering Interfacial Catalysis.

Multifunctional carbon materials have revealed distinctive features and excellent performance in the field of catalysis. However, the facile fabrication of bifunctional carbon materials with special wettability and catalytic activity remains a grand challenge in Pickering emulsion catalysis. Herein, we reported one-step construction of bifunctional biochar with superamphiphilicity and catalytic activity directly from the thermolysis of sawdust and 1-butyl-3-methylimidazolium tetrafluoroborate for enhancing the oxidation of benzyl alcohol in Pickering emulsion. Co-doping of B and F enhanced the hydrophilicity of biochar, and the oleophilicity of biochar was kept simultaneously. Conversion became 4 times using bifunctional biochar compared with blank results during the oxidation of benzyl alcohol. More interestingly, the turnover frequency (TOF) value using bifunctional biochar enhanced 61 % than that employing N-doped superamphiphilic carbon without catalytic activity. Catalytic activities of bifunctional biochar could be ascribed to the existence of different chemical bonds containing the element B. This work paves a path toward rational design of bifunctional biochar materials with special wettability and catalytic activity for greatly enhancing the liquid-liquid biphasic reaction efficiencies.

Base-Mediated Cascade Lactonization/1,3-Dipolar Cycloaddition Pathway for the One-Pot Assembly of Coumarin-Functionalized Pyrrolo[2,1-a]isoquinolines.

An elegant and highly concise strategy for the construction of coumarin-functionalized pyrrolo[2,1-a]isoquinolines from available propargylamines and isoquinolinium N-ylides has been disclosed. In this reaction, isoquinolinium N-ylides acted as a C2 synthon to form a coumarin ring as well as a 1,3-dipole to construct a pyrrole ring in a single pot. This cascade process involves 1,4-conjugate addition/lactonization/1,3-dipolar cycloaddition to construct four chemical bonds (one C-O bond and three C-C bonds) and two new heterocyclic skeletons. Additionally, most of these compounds showed good fluorescence properties and exhibited high molar extinction coefficient and large Stokes shifts.

Geometrical, Electronic, and Optical Properties of Rhombohedral B6O from First‐Principles Calculation

The first‐principles computational methods based on density functional theory are used to study B6O, including its structural, elastic, electronic, and optical properties. The results show that the obtained structural and mechanical parameters are in good agreement with the experimental values. The elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and mechanical stability of rhombohedral B6O are studied. The results show that B6O has mechanical stability, anisotropy, and brittleness. The electronic structure of B6O is analyzed by band structure and density of states. Besides, the chemical bond is systematically explained in terms of Mulliken population and charge density. Finally, the optical characteristics of B6O are examined, encompassing aspects such as the complex dielectric function, conductivity, reflectivity, refractive index, absorption spectrum, and loss function.

Derivation of Morse potential

The Morse potential is widely used in chemistry, physics, and material science to describe interatomic interactions. We show that the Morse potential can be derived from a simple screened charge model accounting for the shielding of the nuclear charge by electron density. In this model, the parameter governing the width of the potential is related to the average shielding strength and the exponents of the atomic orbitals used in electronic structure calculations. The parameter representing the bond dissociation energy of a diatomic molecule is derived by combining the quantum mechanical covalent and classical electrostatic interactions. Moreover, the revealed connection between the parameters of the Morse potential and Pauling’s bond order and electronegativity provides insight into the relation between the classical and quantum mechanical descriptions of chemical bonds. This derivation of the Morse potential from the atomic quantities is expected to contribute to the development of the new basis sets incorporating Slater-type orbitals for electronic structure calculations and the transferable reactive force fields for molecular dynamics simulations. Furthermore, this interpretation of the Morse potential helps to understand the relationships between widely used chemical concepts, including effective atomic charge, bond dissociation energy, electronegativity, and bond order.

Water Microdroplets in Air: A Hitherto Unnoticed Natural Source of Nitrogen Oxides.

Water microdroplets are widespread in the atmosphere. We report a striking observation that micron-sized water droplets obtained from zero-volt spray sources (sonic spray, humidifier, spray bottle, steamer, etc.) spontaneously generate nitrogen oxides. The mechanistic investigation through the development of custom-designed sampling sources combined with mass spectrometry and isotope labeling experiments confirmed that air nitrogen reacts with the water at the air-water interface, fixing molecular nitrogen to its oxides (NO, NO2, and N2O) and acids (HNO2 and HNO3) at trace levels without any catalyst. These reactions are attributed to the consequence of an experimentally detected feeble corona discharge (breakdown of air) at the air-water interface, likely driven by the high intrinsic electric field at the surface of water microdroplets. The extent of this corona discharge effect varies depending on the pH, salinity/impurity, size, speed, and lifetime of microdroplets in the air. Thus, this study discloses that the air-water interface of microdroplets breaks the strong chemical bond of nitrogen (N2), producing nitrogen oxides in the environment, while lightning strikes and microbial processes in soil are considered their dominant natural sources. As nitrogen oxides are toxic air pollutants, their spontaneous formation at the air-water interface should have important implications in atmospheric reactions, requiring further investigations.

Morphological, TGA, and FTIR on Rigid Polyurethane Composite Laminated with Untreated and Treated Bamboo Fiber Roof Insulation

The performance of roof insulation such as polyurethane decreased due to problems such as insufficient absorption and poor thermal insulation performance, especially during rainstorms. The aims of this study are to investigate the physical property and its potential reinforced material such as rigid polyurethane doped with treated and untreated bamboo fiber composite (RPU-BF) at different ratios of 0, 25, 30, 35, and 40% of bamboo fibers as an insulation material for roof applications. The bamboo fibers were treated by using silane coupling agent treatment. The rigid polyurethane composite samples were prepared and then laminated bamboo fiber to overcome the sound problem in roofs. The physical characterization was investigated by Water Contact Angle (WCA), the morphological by Scanning Electron Microscopy (SEM), Thermo-gravimetric Analysis (TGA), and Fourier Transform Infrared Spectroscopy (FTIR) Analysis. The results showed that the treated bamboo fiber had a 192.5° water contact angle as a super hydrophobic property due to the presence of the chemical bonds Si-O-Si and Si-O-C in the silane coupling agent treatment. The morphology showed that 30% ratios of RPU-BF-T30 give the smallest pore diameter size. The peak of thermal degradation temperature of untreated and treated bamboo fiber was increased from 320°C to 350 °C with a weight loss of 80% to 50%. The treated bamboo fiber exhibited peaks at 3010–3040 cm-1 were associated with stronger Si-O-Si bonding, indicating the formation of new chemical bonds between bamboo fiber and silane coupling agent due to the ester bond from the cellulose, lignin, and hemicellulose. Thus, there was a similar trend peak in the functional chemical group in the FTIR spectrum of the RPU-BF composite. This result shows that RPU-BF composite had the potential of the optimum ratio of bamboo fiber as an insulation material for local communities and beneficial to the bamboo industry.

High performance phenothiazine-based battery materials achieved by synergistic steric blocking and extended conjugation

Phenothiazine derivatives, as sustainable cathode materials for batteries, show significant promise for large-scale electrical energy storage applications. However, the irreversibility of the sulfur redox active center severely limits their energy density and discharge voltage in rechargeable organic batteries. This study concentrates on identifying the potential side reactions that contribute to the irreversibility of phenothiazine-based materials. We propose a molecular design strategy that synergistically blocks the active site and extends the conjugation, markedly improving the electrochemical reversibility of these materials. Our findings reveal that phenothiazine derivatives can undergo two successive, one-electron redox reactions without interference from chemical bond rearrangement and reactive radicals. The assembled cells, utilizing lithium (Li) and sodium (Na) as anodes, display two distinct discharge plateaus at 3.3/3.9 V vs. Li+/Li and 3.1/3.7 V vs. Na+/Na, respectively, with nearly identical contributions from the nitrogen (N) and sulfur (S) redox centers. The phenothiazine derivatives designed via this strategy rank among the few phenothiazine-based organic electrode materials capable of achieving highly reversible, two-electron transfer redox reactions in organic batteries.

Effect of cellulose nanocrystals on performance of PVA fiber-reinforced geopolymer composites: Reaction kinetics, bending behavior, and toughening mechanisms

Geopolymer composites are an attractive alternative to those based on ordinary Portland cement, owing to their lower carbon footprint and higher mechanical performance. However, brittleness is one of the major barriers limiting their use in construction applications. In this work, cellulose nanocrystal (CNC), a cost-effective and eco-friendly nanoparticle, was exploited in polyvinyl alcohol (PVA)-reinforced metakaolin-based geopolymer composite to further increase its mechanical performance. To this end, PVA-reinforced geopolymer composites were prepared by varying the CNC concentration from 0 wt% to 0.15 wt%. Three-point bending and fracture testing, combined with digital image correlation (DIC) and scanning electron microscopy (SEM), were performed to evaluate the bending and fracture behavior of samples containing CNC and reveal various toughening mechanisms. Composites with 0.15 wt% CNC recorded an increase of 190% in flexural strength and a 325 time of increase in fracture energy, compared to the control geopolymer (i.e. without PVA fibers and CNC). Isothermal calorimetry, Fourier transform infrared (FTIR) spectroscopy, and x-ray diffraction (XRD) were also utilized to characterize the heat flow, chemical bonds, and crystalline phases of the samples. These analyses revealed that CNC incorporation increased the amount of formed geopolymer gel with no significant changes in the crystalline structure and chemical bonding. In addition, stronger interfacial bonding between the PVA-geopolymer matrix was achieved, resulting in substantial improvements in flexural strength and fracture energy.

Structure and properties of the hot pressing molded anodized aluminum alloy/polyformaldehyde hybrids

The metal-plastic hybrid is one of the important solutions for lightweight and high-strength composite. The anodized aluminum alloy（AAA）/polyformaldehyde（POM） hybrids with excellent mechanical properties were processed by the hot pressing technology. The surface of the aluminum alloy plate was firstly pretreated with phosphoric acid and oxalic acid anodizing, resulting in a large number of micro-nano scale pores on the surface. These pores were well embedded with plastic melt during hot pressing to form micro-nano mechanical interlocking structures and the Al–O–C chemical bond at the interface is generated, thus ensuring good bonding strength at the metal and plastic interface. The maximum tensile-shear strength of the metal-plastic hybrid was 30.65 MPa, meanwhile, the metal-plastic interface failure presented mainly a mixed failure mode, including resin removal from the metal surface and plastic tearing from the plastic surface. At the same time, the salt spray test, thermal shock test, and variable temperature test were adopted to investigate the application performance of the metal-plastic hybrid. The Al/POM hybrids were able to maintain their mechanical strength above 20 MPa for 28 days in a salt spray environment, 14 times in a thermal shock cycle, and at high temperatures. The high mechanical strength of hybrid has good potential for automotive applications.

Synergistic electrochemical and optical properties of a UVC class quaternary nanocomposite incorporating graphene oxide and samarium chromium oxide perovskite

This research presents a comprehensive investigation into a novel quaternary nanocomposite comprising graphene oxide (GO), samarium chromium oxide perovskite (SmCrO3), silicon dioxide (SiO2), and tin dioxide (SnO2). The nanocomposite was synthesized using a modified Stöber method. In order to assess its potential applications in supercapacitors and UVC devices, an extensive analysis of its electrochemical and optical properties was conducted. The crystal structure and phase identification were analyzed using X-ray diffraction (XRD) and Rietveld refinement with X'pert HighScore Plus software, confirming the successful formation of the nanocomposite. Scanning electron microscopy (SEM) provided valuable insights into the structural morphology, while energy dispersive X-ray spectroscopy (EDS) confirmed the presence of constituent elements. Fourier transform infrared (FTIR) analysis and Raman Spectroscopy elucidated the functional groups and chemical bonds, confirming the successful synthesis of the nanocomposite. UV–Vis spectroscopy and photoluminescence (PL) spectroscopy revealed its strong UV radiation absorption and intensified fluorescence properties and confirming the band gap of SmCrO3 and GO/SmCrO3/SiO2/SnO2 quaternary nanocomposite as ∼5.4 eV and 4.84 eV respectively. The potential of nanocomposite potential as a supercapacitor material was evaluated through cyclic voltammetry (CV) measurements and electrochemical impedance spectroscopy (EIS) analyses. Remarkably, the specific capacitance of the nanocomposite reached 253.75 Fg−1 at a scan rate of 10 mVs−1, and electrochemical surface area of 507 cm2, highlighting its exceptional charge storage capability and promising prospects for high-performance energy storage devices. This comprehensive study addresses a significant knowledge gap, providing a profound understanding of the electrochemical and optical behavior of the quaternary nanocomposite. The observed exceptional results underscore its suitability for supercapacitor applications and expected favorable material for UVC device technologies.

Fast reversion of hydrophility-superhydrophobicity on textured metal surface by electron beam irradiation

Reversible hydrophilic-hydrophobic transitions on metal surfaces are challenging in surface-wetting treatment. Existing preparation methods have the disadvantages of requiring a long time, producing a metal oxide layer, and being difficult to implement. In this paper, a rapid reversible transitions between hydrophilicity and superhydrophobicity was achieved on the surface of 316L stainless steel using laser etching combined with electron beam irradiation. The contents of C–C/C–H hydrophobic functional groups was found to be notably increased by low electron dose in the experiments. The contents of C-O-C, O-C = O and –OH hydrophilic functional groups decreased. The interaction of excited secondary electrons with precursor molecules generated free radical fragments that adsorbed onto surfaces and formed new chemical bonds, changing the content of the functional groups. Reversible hydrophilic and superhydrophobic transitions could be achieved by adjusting the electron dose. The contact angle continually changed from 91° to 160° with a beam current of 100 μA, to 17° with 300 μA, and back to 90° with cleaning. The entire procedure required only four minutes. Meanwhile, the superhydrophobic state with contact angle of 160° has a sliding angle of 6°, presenting excellent resistance to bacterial adhesion, UV irradiation, and delayed icing.

Investigation on the lattice vibration, mechanical properties, stress-strain behavior and electronic properties of FeTiSi, CoTiSi and NiTiSi intermetallics from a first-principles calculations

In the present work, we have investigated the structural, electronic, elastic and thermodynamic properties of titanium alloy (XTiSi) (X = Fe, Co, Ni) by using the first-principles calculations. The results showed that XTiSi are dynamically and thermodynamically stable. And the sequence of phase stability is CoTiSi > FeTiSi > NiTiSi. According to the mechanical parameters, three XTiSi ternary alloys exhibit mechanical stability based on the Born stability criteria. FeTiSi exhibits the strongest compression resistance, shear resistance and elastic hardness. The ductility of three alloys is ranked in the order NiTiSi > CoTiSi > FeTiSi. Stress-strain curves are considered by stretching along two directions [100] and [001] directions for three XTiSi alloys. The three-dimensional constructions and two-dimensional projection of elastic moduli were calculated to visually display the anisotropy of three XTiSi alloys. The Debye temperature show that the FeTiSi has good thermal conductivity and chemical bond strength. The electronic structures were used to discussed the magnetic properties, mechanical properties and bonds properties.

Tailoring hydrogen storage performance in γ-graphyne through valence band modulation of adsorbed Li via doping and strain

Hydrogen storage is indeed fundamental to utilizing H2 effectively, and porous carbon materials have emerged as highly promising supports for this purpose. γ-Graphyne (γGy) possesses abundant chemical bonds, considerable porosity, and exceptional chemical stability, positioning it as a promising candidate for hydrogen storage and transport applications. In this study, we conducted density functional theory calculations to investigate the potential of Li- and Na-loaded γGy as hydrogen storage materials. Our findings reveal that the hydrogen storage capacity (HSC) of Na-loaded γGy falls significantly short of expectations, whereas Li-loaded γGy demonstrates a notably higher HSC. Subsequently, our calculations indicate that B-doping of γGy does not promote favorable HSC, whereas N-doping exhibits a beneficial effect. Furthermore, we observed that tensile strain favors the hydrogen storage properties of 4Li@γGy and 4Li@N-γGy, while compressive strain enhances the hydrogen storage characteristics of 4Li@B-γGy. Notably, we discovered the capacity to adjust the valence band center of Li (ɛVB), consequently influencing the hydrogen storage performance of γGy. Our investigation suggests that increased overlap between ɛVB in Li-loaded graphyne and the effective alignment of H2 and the supporting structure augments the binding force between Li and H2, thereby amplifying the HSC.

Effect of anodizing pretreatment on laser joining stainless steel to CFRTP

Metal-carbon fiber reinforced thermoplastic (CFRTP) hybrid joints have demonstrated its effectiveness in achieving lightweight design concept in engineering application. However, it is difficult to produce high-reliability joint due to differences in physical as well as chemical properties between metal and CFRTP. In this study, porous oxide film was prepared by anodizing treatments with various anodic oxidation times on steel surface to enhance joint performance of laser-welded steel/CFRTP. The maximum steel/CFRTP joint fracture load of 1960 N was reached, which was three times as much as that obtained with pretreated steel. The results indicated that porous structure was introduced into steel surface by anodization process, which resulted in better wettability of molten CFRTP and higher surface roughness, thus contributing to the enhancement of joint area as well as mechanical interlocking at the interface, further improving joint performance. Meanwhile, more Cr-O-C chemical bonds were produced because Cr-rich oxide film formed after anodizing contributed to interfacial chemical reaction. The chemical bond between oxide film and CFRTP was proved through density functional theory (DFT) calculation. Additionally, with the increase of anodic oxidation time, chemical bond content and surface roughness first enhanced and then reduced, which suggested that the porous structure prepared with 20 min anodizing time could best improve the interfacial mechanical interlocking, and promote the chemical bonding as well as steel/CFRTP joint interfacial bonding.

Effect of Computer Simulation on Senior High School Students’ Conceptual Understanding of Chemical Bonding

Effect of Computer Simulation on Senior High School Students’ Conceptual Understanding of Chemical Bonding

Band-gap tailoring and third-order optical nonlinearity enhancement through B-site V doping in SrSnO3 films

Perovskite oxide vanadium-doped strontium stannate (SrSn1-xVxO3) thin films with different concentrations x = 0.1–0.9 were fabricated by using pulsed-laser deposition, and the effects of V doping on the structure, optical band gap and the third-order optical nonlinearity were systematically investigated. With the increase of x value, the lattice parameters of SrSn1-xVxO3 decrease from 3.997 to 3.862 Å gradually, while the optical band gaps firstly increase from 4.18 to 4.26 eV, and then decrease to 3.66 eV with a boundary at x = 0.3. The third-order nonlinear optical responses were studied via the z-scan technique. The closed-aperture measurements show a negative nonlinear refractive index n2, and the open-aperture measurements demonstrate a saturable absorption β. Both n2 and β responses vary with the increase of V doping level. The maximum values of n2and β are 2.01×10−13 m2/W and 7.66×10−8 m/W, respectively, which are observed in the SrSn0.5V0.5O3sample. The metal-oxygen chemical bond along with the localized V5+Sn2+V5+complex contribute to the enhancement of optical nonlinearity.