Search Results (5,371)

Classical thermodynamics omits rigidity, which property distinguishes solids from gases and liquids. By accounting for rigidity (i.e., Young’s elastic modulus, ϒ), we recently amended historical formulae and moreover linked heat capacity, thermal expansivity, and ϒ. Further exploration is motivation by the importance of classical thermodynamics to various applied sciences. Based on heat performing work, we show here, theoretically, that density times sublimation enthalpy divided by the molar mass (ρΔH_sub/M, energy per volume), depends linearly on ϒ (1 GPa = 10⁹ J m⁻³). Data on diverse metals, non-metallic elements, chalcogenides, simple oxides, alkali halides, and fluorides with cubic structures validate this relationship at ambient conditions. Furthermore, data on hcp metals and molecular solids show that ρΔH_sub/M is proportional to ϒ for anisotropic materials. Proportionality constants vary only from 0.1 to 0.7 among these different material types (>100 substances), which shows that the elastic energy reservoir of solids is large. Proportionality constants depend on whether molecules or atoms are sublimated and are somewhat affected by structure. We show that ductility of refractory, high-ϒ metals affect high-temperature determinations of their ΔH_sub. Our results provide information on sublimation processes and subsequent gas phase reactions, while showing that elasticity of solids is the key parameter needed to assessing their energetics. Implications are highlighted. Full article

Hydrogen, as a renewable and clean energy with a high energy density, is of great significance to the realization of carbon neutrality. In recent years, extensive research has been conducted on the electrocatalytic hydrogen evolution reaction (HER) by splitting water, with a focus on developing efficient electrocatalysts that can perform the HER at an overpotential with minimal power consumption. Tungsten oxide (WO₃), a non-noble-metal-based material, has great potential in hydrogen evolution due to its excellent redox capability, low cost, and high stability. However, it cannot meet practical needs because of its poor electrical conductivity and the limited number of active sites; thus, it is necessary to further improve HER performance. In this review, recent advances related to WO3-based electrocatalysts for the HER are introduced. Most importantly, several tactics for optimizing the electrocatalytic HER activity of WO₃ are summarized, such as controlling its morphology, phase transition, defect engineering (anion vacancies, cation doping, and interstitial atoms), constructing a heterostructure, and the microenvironment effect. This review can provide insight into the development of novel catalysts with high activity for the HER and other renewable energy applications. Full article

With the rapid growth of energy demand, the development of efficient energy-conversion technologies (e.g., water splitting, fuel cells, metal-air batteries, etc.) becomes an important way to circumvent the problems of fossil fuel depletion and environmental pollution, which motivates the pursuit of high-performance electrocatalysts with controllable compositions and morphologies. Among them, two-dimensional (2D) Pt-group metallic electrocatalysts show a series of distinctive architectural merits, including a high surface-to-volume ratio, numerous unsaturated metal atoms, an ameliorative electronic structure, and abundant electron/ion transfers channels, thus holding great potential in realizing good selectivity, rapid kinetics, and high efficiency for various energy-conversion devices. Considering that great progress on this topic has been made in recent years, here we present a panoramic review of recent advancements in 2D Pt-group metallic nanocrystals, which covers diverse synthetic methods, structural analysis, and their applications as electrode catalysts for various energy-conversion technologies. At the end, the paper also outlines the research challenges and future opportunities in this emerging area. Full article

In order to design new materials at atomic-length scales, there is a need to connect the fractal nature of fracture surfaces at the atomic scale using quantum mechanics modeling with that of the experimental data of fracture surfaces at macroscopic-length scales. We use a semi-empirical quantum mechanics simulation of fracture in amorphous silica to calculate a parameter identified as a critical characteristic length, $a_0$, which has been experimentally derived from the fractal nature of fracture for many materials that fail in a brittle matter. To our knowledge, there are no known simulation models other than our related research that use the fractal parameter $a_0$ to describe the fractal fracture of the fracture surface using quantum mechanical simulations. We provide evidence that $a_0$ can be calculated at both the atomic and macroscopic scale, making it a fundamental property of the structure and one of the elements of fractal fracture. We use a continuous random network model and reaction coordinate method to simulate fracture. We propose that fracture in amorphous silica occurs due to bond reconfiguration resulting in increased strain volume at the crack tip. We hypothesize two specific configurations leading to fracture from a four-fold ring reconfiguration to three-fold ring or (newly observed) five-fold ring configurations resulting in a change in volume. Finally, we define a reconfiguration fracture energy at the atomic level, which is approximately the value of the experimental fracture surface energy. Full article

In the framework of hydrogen production and storage for clean energy generation, the resistance to hydrogen embrittlement of a newly developed austenitic stainless steel is presented. Gas-atomized metal powders prepared from secondary-sourced metals were employed to manufacture test specimens with Laser Powder Bed Fusion (LPBF) technology. After machining and exposure to a controlled, pressurized hydrogen atmosphere at high temperature, the effect of hydrogen charging on the mechanical performance under static and dynamic conditions was investigated. The stabilizing effect of the optimized chemical composition is reflected in the absence of degradation effects on Yield Stress (YS), Ultimate Tensile Stress (UTS), and fatigue life observed for specimens exposed to hydrogen. Moreover, despite a moderate reduction in the elongation at fracture observed by increasing the hydrogen charging time, ductility loss calculated as Relative Reduction of Area (RRA) remains substantially unaffected by the duration of exposure to hydrogen and demonstrates that the austenitic steel is capable of resisting hydrogen embrittlement (HE). Full article

In this work, a comprehensive theoretical investigation is carried out to explore the electronic and spectroscopic properties of selected diatomic molecular ions MgRb⁺ and SrRb⁺. Using high-level ab initio calculations based on a pseudopotential approach, along with large Gaussian basis sets and full valence configuration interaction (FCI), we accurately determine adiabatic potential energy curves, spectroscopic constants, transition dipole moments (TDMs), and permanent electric dipole moments (PDMs). To deepen our understanding of these systems, we calculate radiative lifetimes for vibrational levels in both ground and low-lying excited electronic states. This includes evaluating spontaneous and stimulated emission rates, as well as the effects of blackbody radiation. We also compute Franck–Condon factors and analyze photoassociation processes for both ions. Furthermore, to explore low-energy collisional dynamics, we investigate elastic scattering in the first excited states (2¹Σ⁺) describing the collision between the Ra atom and Mg⁺ or Sr⁺ ions. Our findings provide detailed insights into the theoretical electronic structure of these molecular ions, paving the way for future experimental studies in the field of cold and ultracold molecular ion physics. Full article

The search for selective anticholinergic agents stems from varying cholinesterase levels as Alzheimer’s Disease progresses from the mid-to-late stage and from butyrylcholinesterase’s (BChE) role in β-amyloid plaque formation. While structure-based and pharmacophore-based virtual screening could search from large libraries in a short time, these methods do not consider dynamic features that result from a ligand’s inhibition of the enzyme and consequently may under- or overexaggerate enzyme selectivity of a given ligand. In this computational study, we probed the selectivity of representative secondary metabolite compounds against acetylcholinesterase and BChE through molecular dynamics simulations. The results were evaluated by analysis of the root mean squared deviation of ligand heavy atoms, the radius of gyration of each inhibited and uninhibited enzyme, root mean squared fluctuation of residues, intermolecular interaction energy, and linear interaction energy approximation of the Gibbs free energy of binding. These considerations further reveal the induced-fit characteristics contributing to ChE selectivity that are predominantly due to the greater flexibility of BChE’s active site gorge. Full article

In order to explore the essence of the anticoccidiosis of anticoccidial drugs under bioelectric currents, the intermolecular double-proton transfer and conformational transformation of 4-pyridone-3-carboxylic acid were investigated by quantum chemistry calculations (at the M06-2X/6-311++G**, M06-2X/aug-cc-pVTZ and CCSD(T)/aug-cc-pVTZ levels) and finite temperature string (FTS) under external electric fields. The solvent effect of H₂O on the double-proton transfer was evaluated by the integral equation formalism polarized continuum model. The results indicate that the influences of the external electric fields along the direction of the dipole moment on double-proton transfer are significant. The corresponding products are controlled by the direction of the external electric field. Due to the first-order Stark effect, some good linear relationships form between the changes of the structures, atoms in molecules (AIMs) results, surface electrostatic potentials, barriers of the transition state, and the external electric field strengths. From the gas to solvent phase, the barrier heights increased. The spatial order parameters (ϕ, ψ) of the conformational transformation could be quickly converged through the umbrella sampling and parameter averaging, and thus the free-energy landscape for the conformational transformation was obtained. Under the external electric field, there is competition between the double-proton transfer and conformational transformation. The external electric field greatly affects the cooperativity transfer, while it has little effect on the conformational transformation. This study is helpful in the selection and updating of anticoccidial drugs. Full article

Reducing the application of chemical fertilizers and remediating heavy metal pollution in soil are important directions in current agricultural research. Utilizing the plant-growth-promoting and remediation capabilities of bacteria can provide more environmentally friendly assistance to agricultural production. In this study, the Burkholderia alba YIM B08401 strain was isolated and identified from rhizospheric soil, subjected to whole-genome sequencing and analysis, and its Cd²⁺ adsorption efficiency and characteristics were confirmed using multiple experimental methods, including atomic absorption spectrometry (AAS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS). The results showed that the genome of strain YIM B08401 has a total length of 7,322,157 bp, a GC content of 66.39%, and predicts 6504 protein-coding sequences. It contains abundant functional genes related to nutrient conversion (phosphate solubilization, sulfur metabolism, zinc solubilization, siderophore production), plant hormone regulation (indole-3-acetic acid secretion, ACC deaminase production), phenolic acid degradation, root colonization, heavy metal tolerance, pathogen antagonism, and the production of antagonistic secondary metabolites. Additionally, strain YIM B08401 can specifically bind to Cd²⁺ through various functional groups on the cell surface, such as C-O-C, P=O, and O-H, enabling biosorption. In conclusion, strain YIM B08401 is an excellent strain with plant-growth-promoting, disease-resistant, and bioremediation capabilities, warranting further development as a biofertilizer for agricultural applications to promote green and sustainable agricultural development. Full article

Tungsten and tungsten alloys are widely used in important industrial fields due to their high density, hardness, melting point, and corrosion resistance. However, machining often leaves processing marks on their surface, significantly affecting the surface quality of precision components in industrial applications. Electrolytic polishing offers high efficiency, low workpiece wear, and simple processing. In this study, an electrolytic polishing method is adopted and a novel trisodium phosphate–sodium hydroxide electrolytic polishing electrolyte is developed to study the effects of temperature, voltage, polishing time, and solution composition on the surface roughness of a tungsten–nickel–iron alloy. The optimal voltage, temperature, and polishing time are determined to be 15 V, 55 °C, and 35 s, respectively, when the concentrations of trisodium phosphate and sodium hydroxide are 100 g·L⁻¹ and 6 g·L⁻¹. In addition, glycerol is introduced into the electrolyte as an additive. The calculated LUMO value of glycerol is −5.90 eV and the HOMO value is 0.40 eV. Moreover, electron enrichment in the hydroxyl region of glycerol can form an adsorption layer on the surface of the tungsten alloy, inhibit the formation of micro-pits, balance ion diffusion, and thus promote the formation of a smooth surface. At 100 mL·L⁻¹ of glycerol, the roughness of the tungsten–nickel–iron alloy decreases significantly from 1.134 μm to 0.582 μm. The electrochemical polishing mechanism of the tungsten alloy in a trisodium phosphate electrolyte is further investigated and explained according to viscous film theory. This study demonstrates that the trisodium phosphate–sodium hydroxide–glycerol electrolyte is suitable for electropolishing tungsten–nickel–iron alloys. Overall, the results support the application of tungsten–nickel–iron alloy in the electronics, medical, and atomic energy industries. Full article

In our previous work, we fabricated Ni single-atoms within Beta zeolite (Ni₁@Beta-NO₃⁻) using NiNO₃·6H₂O as a metal precursor without any chelating agents, which exhibited exceptional performance in the selective hydrogenation of furfural. Owing to the confinement effect, the as-encapsulated nickel species appears in the form of Ni⁰ and Ni^δ+, which implies its feasibility in metal catalysis and coordination catalysis. In the study reported herein, we further explored the hydrogen production and olefin oligomerization performance of Ni₁@Beta-NO₃⁻. It was found that Ni₁@Beta-NO₃⁻ demonstrated a high H₂ generation turnover frequency (TOF) and low activation energy (E_a) in a sodium borohydride (NaBH₄) hydrolysis reaction, with values of 331 min⁻¹ and 30.1 kJ/mol, respectively. In ethylene dimerization, it exhibited a high butylene selectivity of 99.4% and a TOF as high as 5804 h⁻¹. In propylene oligomerization, Ni₁@Beta-NO₃⁻ demonstrated high selectivity (75.21%) of long-chain olefins (≥C₆⁺), overcoming the problem of cracking reactions that occur during oligomerization using H-Beta. Additionally, as a comparison, the influence of the metal precursor (NiCl₂) on the performance of the encapsulated Ni catalyst was also examined. This research expands the application scenarios of non-noble metal single-atom catalysts and provides significant assistance and potential for the production of H₂ from hydrogen storage materials and the production of valuable chemicals. Full article

Background/Objectives: A nanostructured membrane of polycaprolactone (a synthetic polymer) was synthesized using an electrospinning technique aiming to enhance its hydrophilicity and rate of degradation by surface modification via aminolysis. Since polycaprolactone nanofibrous films are naturally hydrophobic and with slow degradation, which restricts their use in biological systems, amino groups were added to the fiber surface using the aminolysis technique, greatly increasing the wettability of the membranes. Methods: Polycaprolactone nanofibrous membranes were synthesized via the electrospinning technique and surface modification by aminolysis. Trypsin, pepsin, and pancreatin were conjugated onto the aminolyzed PNF surface to further strengthen biocompatibility by enhancing the hydrophilicity, porosity, and biodegradation rate. SEM, FTIR, EDX, and liquid displacement method were performed to investigate proteolytic efficiency and morphological and physical characteristics such as hydrophilicity, porosity, and degradation rates. Results: Enzyme activity tests, which showed a zone of clearance, validated the successful enzyme conjugation and stability over a wide range of pH and temperatures. Scanning electron microscopy (SEM) confirms the smooth morphology of nanofibers with diameters ranging from 150 to 950 nm. Fourier transform infrared spectroscopy (FTIR) revealed the presence of O–H, C–O, C=O, C–N, C–H, and O–H functional groups. Energy-dispersive X-ray (EDX) elemental analysis indicates the presence of carbon, oxygen, and nitrogen atoms owing to the presence of peptide and amide bonds. The liquid displacement technique and contact angle proved that Pepsin-PNFs possess notably increased porosity (88.50% ± 0.31%) and hydrophilicity (57.6° ± 2.3 (L), 57.9° ± 2.5 (R)), respectively. Pancreatin-PNFs demonstrated enhanced enzyme activity and degradation rate on day 28 (34.61%). Conclusions: These enzyme-conjugated PNFs thus show improvements in physicochemical properties, making them ideal candidates for various biomedical applications. Future studies must aim for optimization of enzyme conjugation and in vitro and in vivo performance to investigate the versatility of these scaffolds. Full article

Hydrogen, as the smallest atom and a key component of water, can penetrate minerals in various forms (e.g., atoms, molecules), significantly influencing their properties. The hydrogen diffusion behavior in corundum (α-Al₂O₃) under high pressure was systematically investigated using the DFT + NEB method. The results indicate that H atoms tend to aggregate into H₂ molecules within corundum under both ambient and high-pressure conditions. However, hydrogen predominantly migrates in its atomic form (H) under both low- and high-pressure environments. The energy barriers for H and H₂ diffusion increase with pressure, and hydrogen diffusion weakens the chemical bonds nearby. Using the Arrhenius equation, we calculated the diffusion coefficient of H in corundum, which increases with temperature but decreases with pressure. On geological time scales, hydrogen diffusion is relatively slow, potentially resulting in a heterogeneous distribution of water in the lower mantle. These findings provide novel insights into hydrogen diffusion mechanisms in corundum under extreme conditions, with significant implications for hydrogen behavior in mantle minerals at high pressures. Full article

The fabrication and application of single-site heterogeneous reaction centers are new frontiers in chemistry. Single-site heterogeneous reaction centers are analogous to metal centers in enzymes and transition-metal complexes: they are charged and decorated with ligands and would exhibit superior reactivity and selectivity in chemical conversion. Such high reactivity would also result in significant response, such as a band gap or resistance change, to approaching molecules, which can be used for sensing applications. As a proof of concept, the electronic structure and reaction pathways with NO and NO₂ of Au(I) fragments dispersed on phosphorene (Pene) were investigated with first-principle-based calculations. Atomic-deposited Au atoms on Pene (Au₁-Pene) have hybridized Au states in the bulk band gap of Pene and a decreased band gap of 0.14 eV and would aggregate into clusters. Passivation of the Au hybrid states with -OH and -CH₃ forms thermodynamically plausible HO-Au₁-Pene and H₃C-Au₁-Pene and restores the band gap to that of bulk Pene. Inspired by this, HO-Au₁-Pene and H₃C-Au₁-Pene were examined for detection of NO and NO₂ that would react with -OH and -CH₃, and the resulting decrease of band gap back to that of Au₁-Pene would be measurable. HO-Au₁-Pene and H₃C-Au₁-Pene are highly sensitive to NO and NO₂, and their calculated theoretical sensitivities are all 99.99%. The reaction of NO₂ with HO-Au₁-Pene is endothermic, making the dissociation of product HNO₃ more plausible, while the barriers for the reaction of CH₃-Au₁-Pene with NO and NO₂ are too high for spontaneous detection. Therefore, HO-Au₁-Pene is not eligible for NO₂ sensing and CH₃-Au₁-Pene is not eligible for NO and NO₂ sensing. The calculated energy barrier for the reaction of HO-Au-Pene with NO is 0.36 eV, and the reaction is about thermal neutral, suggesting HO-Au-Pene is highly sensitive for NO sensing and the reaction for NO detection is spontaneous. This work highlights the potential superior sensing performance of transition-metal fragments and their potential for next-generation sensing applications. Full article

Against the backdrop of global energy transition and strict environmental regulations, supercritical carbon dioxide (scCO₂) fracturing and oil displacement technologies have emerged as pivotal green approaches in shale gas exploitation, offering the dual advantages of zero water consumption and carbon sequestration. However, the inherent low viscosity of scCO₂ severely restricts its sand-carrying capacity, fracture propagation efficiency, and oil recovery rate, necessitating the urgent development of high-performance thickeners. The current research on scCO₂ thickeners faces a critical trade-off: traditional fluorinated polymers exhibit excellent philicity CO₂, but suffer from high costs and environmental hazards, while non-fluorinated systems often struggle to balance solubility and thickening performance. The development of new thickeners primarily involves two directions. On one hand, efforts focus on modifying non-fluorinated polymers, driven by environmental protection needs—traditional fluorinated thickeners may cause environmental pollution, and improving non-fluorinated polymers can maintain good thickening performance while reducing environmental impacts. On the other hand, there is a commitment to developing non-noble metal-catalyzed siloxane modification and synthesis processes, aiming to enhance the technical and economic feasibility of scCO₂ thickeners. Compared with noble metal catalysts like platinum, non-noble metal catalysts can reduce production costs, making the synthesis process more economically viable for large-scale industrial applications. These studies are crucial for promoting the practical application of scCO₂ technology in unconventional oil and gas development, including improving fracturing efficiency and oil displacement efficiency, and providing new technical support for the sustainable development of the energy industry. This study innovatively designed an amphiphilic modified amino silicone oil polymer (MA-co-MPEGA-AS) by combining maleic anhydride (MA), methoxy polyethylene glycol acrylate (MPEGA), and amino silicone oil (AS) through a molecular bridge strategy. The synthesis process involved three key steps: radical polymerization of MA and MPEGA, amidation with AS, and in situ network formation. Fourier transform infrared spectroscopy (FT-IR) confirmed the successful introduction of ether-based CO₂-philic groups. Rheological tests conducted under scCO₂ conditions demonstrated a 114-fold increase in viscosity for MA-co-MPEGA-AS. Mechanistic studies revealed that the ether oxygen atoms (Lewis base) in MPEGA formed dipole–quadrupole interactions with CO₂ (Lewis acid), enhancing solubility by 47%. Simultaneously, the self-assembly of siloxane chains into a three-dimensional network suppressed interlayer sliding in scCO₂ and maintained over 90% viscosity retention at 80 °C. This fluorine-free design eliminates the need for platinum-based catalysts and reduces production costs compared to fluorinated polymers. The hierarchical interactions (coordination bonds and hydrogen bonds) within the system provide a novel synthetic paradigm for scCO₂ thickeners. This research lays the foundation for green CO₂-based energy extraction technologies. Full article