Search Results (1,147)

Coal spontaneous combustion (CSC) remains a major hazard in coal mining. Research on CSC has largely focused on macromolecular structures, while the behavior of low-molecular-weight compounds remains unclear. Using B3LYP/6-311G density functional theory, this study systematically reveals thirteen microscopic reaction pathways, active sites, and the energy barrier order of pentanol during coal spontaneous combustion. The oxidation proceeds via thirteen multi-step pathways involving bond breaking and formation, with the dominant reaction being oxygen attack on the -CH₂OH group to produce pentanal (CH₃CH₂CH₂CH₂CHO) and water as the main products. The priority order of thirteen reaction pathways between pentanol and oxygen was established as: Path 6 > Path 3 > Path 8 > Path 5 > Path 4 > Path 1 > Path 11 > Path 10 > Path 9 > Path 12 > Path 7 > Path 2. The results reveal the multi-step bond-breaking and formation mechanism at the molecular level, providing a fundamental theoretical framework for understanding the radical chain oxidation mechanism of low molecular weight compounds in CSC. Full article

Deep eutectic solvent (DES) extraction is a green and efficient technology. As a substitute for organic reagents, DESs are widely used to extract active ingredients from traditional Chinese medicine. This study established an environmentally friendly and efficient method for extracting astaxanthin (AST) from Phaffia rhodozyma (PR) using ultrasound-assisted deep eutectic solvents (DESs-UAE). The astaxanthin content was determined by high-performance liquid chromatography (HPLC). Six types of deep eutectic solvents composed of DL-menthol and selected hydrogen bond donors were prepared and evaluated, among which the DL-menthol–acetic acid system showed superior extraction performance. Response surface methodology (RSM) was employed to optimize extraction parameters (ultrasonic power, time, and temperature), and the optimal conditions were determined as follows: ultrasonic power 420 W, ultrasonic time 20 min, and ultrasonic temperature 60 °C, achieving an AST extraction rate of 62% (2.49 mg/g). Compared with conventional organic solvent extraction, DESs exhibited a significantly higher AST extraction rate from PR, except for dimethyl sulfoxide (DMSO). Scanning electron microscopy (SEM) analysis demonstrated that DES-UAE treatment disrupted the cellular structure of PR, resulting in numerous surface pores; this facilitated the release of intracellular bioactive components and significantly improved AST extraction efficiency. The PR extract showed no significant cytotoxicity and could effectively promote L929 cell proliferation. It concentration-dependently increased superoxide dismutase (SOD) activity and decreased malondialdehyde (MDA) content in H₂O₂-induced oxidative stress L929 cells, thereby alleviating oxidative damage. Additionally, it concentration-dependently upregulated type I collagen expression in these cells, ameliorated the decline in collagen synthesis function, and exerted a protective effect against cellular oxidative damage. This study provides a green alternative to toxic solvents and offers important theoretical and chemical support for the extraction of natural products and the high-value utilization of Phaffia rhodozyma (PR). Deep eutectic solvents have emerged as promising green alternatives to hazardous organic solvents, yet hydrophobic DESs tailored for lipophilic astaxanthin extraction from Phaffia rhodozyma and the linkage between extraction performance and anti-aging bioactivity remain insufficiently explored. Here, an ultrasound-assisted hydrophobic deep eutectic solvent extraction strategy was constructed to acquire astaxanthin, aiming to overcome low efficiency and environmental risks of conventional organic extraction techniques. Six DL-menthol-based DESs were prepared and screened, and DL-menthol–acetic acid possessed the optimal extraction capacity. Key extraction parameters were optimized via response surface methodology, and the maximum astaxanthin extraction recovery reached 62% (2.49 mg/g) under 420 W ultrasonic power, 20 min treatment and 60 °C. This yield was markedly higher than that of most common organic solvents; though comparable extraction effect was obtained with DMSO, the adopted DES possessed outstanding low-toxic and biodegradable superiorities that DMSO cannot match. SEM characterization verified that the combined treatment destroyed yeast cell structure and formed porous morphology, which accelerated intracellular astaxanthin release and accounted for improved extraction efficiency. Biological assays proved the extract possessed good biosafety and proliferation-promoting effect on L929 cells. It effectively relieved cellular oxidative injury by elevating the SOD level and reducing MDA accumulation in oxidative damaged cells, and upregulated type I collagen expression to mitigate aging-related collagen loss. This work develops an eco-friendly and high-efficiency extraction route for lipophilic active substance, confirms the practical value of hydrophobic DES, and provides experimental basis for high-value utilization of Phaffia rhodozyma resources. Full article

To address gas channeling, low sweep efficiency, and water sensitivity in CO₂ flooding of shale reservoirs, amidine-functionalized graphene quantum dots (FN-GQDs) were synthesized via amidation of citric acid-derived GQDs. FTIR and UV-Vis confirmed successful grafting. Conductometric titration showed an optimal reaction time of 24 h with a grafting ratio of 58%, in good agreement with the 60% saturation predicted by molecular dynamics simulation. Upon CO₂ introduction, protonation of amidine groups induced a nonlinear viscosity increase from 0.298 to 2.0 mPa·s at 0.02 wt% via electrostatic attraction and hydrogen bonding, forming a dynamic crosslinking network. FN-GQDs maintained low oil-water interfacial tension of 0.12–0.25 mN/m at 80–120 °C and rapidly reversed rock wettability from strongly oil-wet to water-wet, reducing the contact angle from 141.7° to 38.9° within 80 min. The positively charged surface inhibited clay swelling, achieving 92% at 0.20 wt%. Core flooding and NMR T₂ spectra revealed that alternating CO₂ and FN-GQDs injection at a 2:1 gas–water ratio achieved a final oil recovery of 52.5%, significantly higher than pure CO₂ flooding. Through synergistic effects of interfacial tension reduction, wettability alteration, viscosity enhancement, and anti-swelling, FN-GQDs improve microscopic displacement efficiency and macroscopic sweep volume, showing great potential for CO₂-enhanced oil recovery in shale reservoirs. Full article

To address the poor solubility, instability, and low oral bioavailability of quercetin (Q), Q-loaded nanoparticles (Q@DDZ) were fabricated using deamidated zein peptide (DDZ) via a pH-driven method. As a food-grade hydrophilic colloid, DDZ effectively improves the colloidal stability of the delivery system. Deamidation increased hydrophilic amino acids and surface negative charge. DDZ bound Q via static quenching with a higher binding constant (K_a = 2.25 × 10³ L/mol) and more binding sites (n = 1.7561) than zein, along with stronger hydrogen bonding and hydrophobic interactions. Q@DDZ exhibited higher encapsulation efficiency (45.36–87.32%) and loading capacity (1.82–12.27%) than Q@zein, with a smaller particle size and better dispersibility. At 50.0 μg/mL Q, Q@DDZ showed 41.06% (DPPH) and 46.62% (ABTS) higher scavenging rates than free Q. It displayed excellent stability under acidic, high ionic strength, and thermal conditions (80 °C, 180 min). In simulated digestion, Q@DDZ delayed Q release in the oral and gastric phases and prolonged intestinal release, which indicated potentially improved bioavailability. This study provides mechanistic insights into deamidation-modified plant protein delivery systems for hydrophobic bioactives, offering new perspectives for the development of functional biopolymer gel materials. Full article

To achieve efficient removal and defluorination of perfluorooctanoic acid (PFOA), a visualized micro-scale fused quartz tube reactor (FQTR) was constructed to systematically investigate sub/supercritical water oxidation (SCWO) processes. Under operating conditions of 200–400 °C and 8–27.3 MPa, PFOA underwent rapid degradation with near-complete conversion. The incorporation of γ-MnO₂ markedly enhanced the PFOA degradation at low temperature and achieved faster fluorine removal. At the conditions of 300 °C, 40 min, O/C ratio (oxygen-to-carbon molar ratio) = 1.5, and pH = 7, the degradation and defluorination efficiencies increased by 12.56% and 15.21%, respectively, compared with the non-catalytic system. This enhancement is primarily attributed to the efficient activation of H₂O₂ by γ-MnO₂, which promotes the breaking of C–F bond and accelerates the converting of PFOA into CO₂ and fluoride ions. The SEM, Raman and leaching experiment results demonstrated that γ-MnO₂ exhibits excellent structural stability and reusability. Furthermore, density functional theory (DFT) calculations were performed to identify potential reactive sites and elucidate degradation pathways at the molecular level, providing mechanistic support for the experimental observations. Overall, the γ-MnO₂-catalyzed SCWO exhibits excellent degradation and defluorination performance for PFOA removal, providing useful insight into the treatment of fluorinated wastewater. Full article

Nitrogen-containing molecules are fundamental components of astrobiology and play a key role in planetary environments. These species are particularly important because they may serve as key precursors to prebiotic molecules and contribute to chemical complexity. Reactions involving the highly reactive species methylidyne (CH) play a key role in complex organic formation in astrochemical environments, yet their interactions with nitriles such as acetonitrile (CH₃CN) remain relatively unexplored. In this work, we investigate the reaction network of CH + CH₃CN using high-level quantum-chemical calculations with RRKM and microcanonical transition-state theories to characterize the relative energies of reactants, intermediates, transition states, and products to identify the most favorable reaction pathways. Our results reveal that the most energetically favorable reaction channels proceed via barrierless CH addition to the triple CN bond and three-membered ring opening or CH insertion into a C-H bond, followed by a hydrogen elimination to form acrylonitrile (C₂H₃CN). This route highlights an efficient pathway toward a molecule of astrobiological interest. Acrylonitrile is particularly significant due to its stability and dual functional groups, which enable molecular growth complexity, both in planetary atmospheres and on surfaces, under astrochemical conditions. In addition to acrylonitrile, we identified a few other competing channels leading to an isonitrile species, which emphasizes a previously unexplored aspect of isomerization chemistry in the atmospheric planetary science. These isonitrile products, while less abundant, provide insight to the diversity of nitrogen-containing molecules that may form in environments such as Titan’s atmosphere or the interstellar medium. In these environments, acrylonitrile may serve as a reactive precursor that facilitates cyclization and molecular growth, which enables the formation of nitrogen-containing polycyclic aromatic molecules and N-heterocycles. This, in turn, contributes to the emergence of larger, more complex organic species relevant to prebiotic chemistry and potential origin of life in our solar system. Full article

This study examined the effects of soy protein isolate (SPI) 7S and SPI 11S on the anthocyanin (AN) retention rate of Lonicera caerulea L. under different processing conditions and further analyzed the molecular interaction mechanisms between 7S/11S and cyanidin-3-O-glucoside (C3G). The results demonstrated that SPI increased the retention rate of anthocyanins to varying degrees while also enhancing the digestive stability. Multispectral results indicated that static quenching occurred between 7S/11S and C3G, and the polarity changes in the amino acid microenvironment varied with pH. Thermodynamic analysis indicated that hydrogen bonds dominated the interaction under both pH conditions, while a certain degree of hydrophobic interaction was additionally observed under neutral conditions. After binding with C3G, the proportion of β-sheet structures in SPI decreased and the proportion of other structures increased. Finally, molecular docking further simulated the binding between SPI and C3G and revealed the important roles of hydrophobic interactions and hydrogen bonding, which also promoted the combination of SPI and C3G to form a stable complex. This study provides a mechanistic reference for using proteins as effective carriers to protect anthocyanins, with implications for developing functional food components with enhanced stability. Full article

Squalene is a triterpene with potent biological activities. Squalene (C₃₀H₅₀) is a linear polyunsaturated hydrocarbon composed of six isoprene units and six carbon–carbon double bonds. It serves as an essential precursor for sterols, steroid hormones, and vitamin D in humans and exhibits antioxidant, anti-tumor, and lipid-regulating properties. In plants, squalene is produced via the mevalonate (MVA) and 2-C-methyl-D-erythritol-4-phosphate (MEP) pathways. The key rate-limiting enzymes in these pathways include 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), farnesyl diphosphate synthase (FPS), and squalene synthase (SQS). Camellia oleifera, a unique woody oil crop native to China, is valued for its high-quality edible oil and as a rich natural source of squalene. This review provides a systematic overview of recent progress in squalene biosynthesis in C. oleifera. It summarizes the structural characteristics and biosynthetic routes. It further elaborates on the multi-level regulatory network modulated by transcription factors (WRKY, bHLH, MYB, and ERF), phytohormones (jasmonic acid, abscisic acid, and gibberellin), and abiotic factors (light and drought). Notably, this review distinguishes earlier foundational studies from recent breakthroughs and integrates emerging progress on squalene’s non-canonical functions and pathway crosstalk. It further highlights novel regulatory mechanisms unique to C. oleifera (e.g., CoWRKY15, CoMYB1, and CoMYC2). By bridging molecular regulation with practical breeding and metabolic engineering, this review lays a solid theoretical foundation for cultivating high-squalene C. oleifera varieties. It represents a prominent innovation relative to previously published studies. Full article

Aquaculture wastewater containing tetracycline hydrochloride (TCH) poses significant environmental problems and health risks. We investigated the adsorption of TCH onto phosphoric acid-activated corncob biochar (PCC) as a sustainable and efficient removal strategy. PCC was synthesized from cob feedstock activated by phosphoric acid under a pyrolysis temperature of 300 °C in a limited-air atmosphere. It was characterized extensively, revealing a high specific surface area (1071.75 m²/g), high porosity with total pore volume of 0.912 cm³/g, and abundant surface functional groups including phosphate, carboxylic, and amine groups. Batch adsorption experiments demonstrated an ultrahigh adsorption capacity for TCH, with a maximum theoretical capacity (Langmuir model) of 953.62 mg/g at 313 K. Its adsorption isotherms transfer from Langmuir type to Freundlich type as temperature rises, indicating a transition from monolayer to multilayer adsorption. The adsorption kinetics were governed by a synergistic mechanism involving surface adsorption and a pore-filling effect (intra-particle diffusion). Critically, the adsorption dynamics exhibit an intra-particle diffusion-controlled process at a low pH (3.0) during the final stage of adsorption. Strong hydrogen bonding led to high initial adsorption rates, and the adsorption converted to diffusion-controlled mode eventually. In contrast, at higher pH (≥7.0), electrostatic repulsion between PCC adsorbents and TCH molecules hindered intra-particle diffusion, causing the final adsorption stage to deviate from diffusion control. This work provides comprehensive insights into the pH-dependent interfacial interactions and kinetics governing TCH removal by corncob-derived, phosphoric acid-activated biochar. Full article

To enhance the interfacial bonding between bamboo and the polymer matrix in natural fiber composites (NFCs), vacuum heat treatment was applied to moso bamboo strips at temperatures ranging from 140 to 180 °C with holding times of 4 and 6 h. The effects of treatment conditions on the surface characteristics and chemical composition of bamboo were systematically investigated. Scanning electron microscopy (SEM), contact angle measurements, and Fourier transform infrared spectroscopy (FTIR) were employed to evaluate the changes in microstructure, surface wettability, and the main functional groups including α-cellulose, hemicellulose, and lignin. The results indicate that the severity of heat treatment (temperature–time combination) significantly influences the physicochemical properties of bamboo. Hemicellulose, which exhibited the lowest thermal stability, underwent pronounced degradation above 140 °C and showed the most substantial compositional variation. Although the relative contents of α-cellulose and lignin increased with increasing treatment severity, their absolute contents decreased. The vacuum environment was found to retard the degradation of α-cellulose to some extent. At 180 °C, severe disruption of the cell wall structure was observed, accompanied by the deformation and collapse of cell lumens. In addition, heat treatment increased the surface contact angle, indicating enhanced hydrophobicity, with temperature exerting a more pronounced effect than treatment time. FTIR analysis revealed a marked reduction in the intensity of the C=O stretching vibration of hemicellulose (~1730 cm⁻¹) and the O–H stretching vibration (~3400 cm⁻¹), while the aromatic structure of lignin remained relatively stable. Overall, vacuum heat treatment effectively enhanced the surface hydrophobicity of bamboo, providing a theoretical basis and technical support for the development of bamboo-reinforced natural fiber composites. Full article

Conductive filaments for Material Extrusion Additive Manufacturing (MEX) can enable low-cost fabrication of functional parts with embedded electrical features. However, systematic studies on process-dependent electrical properties like apparent resistivity and repeatability are limited, and the post-printing stability of the electrical response is not commonly addressed. This study evaluates the influence of printing temperature, printing speed and layer height on the apparent resistivity, specimen-to-specimen repeatability and time-dependent drift of a commercial carbon black-filled conductive PLA filament (ProtoPasta). The novelty of the study consists of evaluating not only the initial apparent resistivity, but also the repeatability between specimens and the post-print drift of apparent resistivity over a 0–50 h interval. The filament was investigated using three printing temperatures (210–230 °C), two printing speeds (60–80 mm/s) and three layer heights (0.2–0.4 mm), with three replicates per configuration. Apparent resistivity ranged between 0.156 and 0.205 kΩ·mm at t0 and between 0.162 and 0.222 kΩ·mm at t50. Multifactorial ANOVA and main-effects analyses showed that the printing temperature was the main factor affecting mean apparent resistivity at both t0 and t50. Higher temperature reduced apparent resistivity, most likely due to improved polymer flow, inter-bead/inter-layer bonding and conductive-network continuity. Printing speed had no significant main effect on the mean apparent resistivity or drift within the tested range. Repeatability depended on the parameter configuration and measurement time, with variability increasing after 24 h and then becoming mainly dependent on layer height. Drift analysis showed a significant main effect of layer height and a significant layer height × temperature interaction, with the largest increase at 0.3 mm. These results show that parameter selection for conductive MEX parts should consider both the initial resistivity level and post-print stability over time. Full article

During flotation, the hydration behavior of collector head groups plays an important role in determining collector hydrophilicity and interfacial adsorption behavior. However, although computation-assisted flotation studies have extensively investigated collector–mineral interactions, systematic comparisons of the intrinsic hydration characteristics of different collector head groups under unified computational conditions remain limited. In this work, density functional theory (DFT) calculations using the B3LYP functional with Grimme dispersion correction were conducted to investigate the hydration interactions between water molecules and representative head groups of five sulfide mineral collectors, including xanthate (X), dithiocarbamate (DTC), dithiophosphate (DTP), dithiophosphinate (3418A), and thiocarbamate (Z-200), and five oxide mineral collectors, including oleate (OA), oxidized paraffin soap (OPS–C₁₂), dodecyl sulfonate (DS), styrene phosphonic acid (SPA), and salicylhydroxamic acid (BHA). The results show that oxide mineral collectors exhibit significantly stronger hydration interactions than sulfide mineral collectors. Sulfide collectors mainly form weak S···H–O hydrogen bonds with relatively long H-bond distances (2.27–2.61 Å), whereas oxide collectors predominantly form stronger O···H–O hydrogen bonds with shorter distances (1.66–2.24 Å). The total hydration binding energies of sulfide collectors range from −150 to −290 kJ/mol, while those of oxide collectors range from −244 to −491 kJ/mol. Among the studied collectors, SPA exhibits the strongest hydration tendency due to its highly charged phosphonate group, whereas Z-200 shows the weakest hydration interaction. The results indicate that hydration behavior is strongly influenced by head group type, charge state, and hydrogen-bond characteristics. Full article

The addition of calcium oxide (CaO) as an additive to B35 biodiesel enhances molecular modifications through changes in the FAME chemical structure. CaO was dispersed in biodiesel using 48 kHz ultrasonic vibration for 48 hours, inducing an exothermic reaction that generated Ca⁺ and O⁻ ions. These ions primarily affected C–H bonds in CH₃, CH₂, and CH groups, with the strongest impact on CH₃ due to its highest bond energy. This perturbation triggered molecular fragmentation and the formation of acetylenic and sp³ alkane C–H compounds, serving as precursors for new functional groups. The study revealed a potential energy increase of 8.1% for acetylenic C–H chains and 13.2% for sp³ alkane C–H stretching. Full article

Bamboo is a renewable and fast-growing biomass resource with limited utilization and service life owing to its susceptibility to mold. Conventional nano-modification methods, particularly two-step approaches, are limited by weak interfacial bonding between nanoparticles and the bamboo substrate, complex processing, and an inability to simultaneously enhance antimildew performance and dimensional stability. To address these limitations, we developed a one-step hydrothermal method involving the use of tannic acid (TA) for in situ fabrication of ZnO/TA/Ag composite particles on bamboo surfaces. Process parameters were optimized to 100 °C, 10 h, and a zinc acetate-to-tannic acid molar ratio of 20:1. The modified bamboo was characterized using Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy coupled with energy-dispersive spectroscopy, and thermogravimetric analysis. We demonstrated that ZnO/TA/Ag composite particles were successfully loaded onto the bamboo surface, thus improving the all-around performance of the bamboo simultaneously. Antimildew activity against Aspergillus niger and Penicillium citrinum increased from grade 4 in untreated bamboo to grades 1 and 0, respectively; water absorption decreased by 52.85%, and anti-swelling efficiency reached 30.41%, indicating improved mold resistance and dimensional stability. Thus, our technique could serve as a green and efficient one-step in situ modification strategy for high-performance functionalization of bamboo, making it suitable for applications in humid outdoor and indoor environments. Full article

The microenvironment of the porous channels in enzyme immobilization carriers critically determines the catalytic performance of immobilized enzymes. In this study, we systematically tuned the hydrophobicity/hydrophilicity of the channel microenvironment of hydrogen-bonded organic frameworks (HOFs) by introducing four different substituents (-CH₃, -Cl, -F, -NH₂) at the 2-position of the phenyl ring of the HOF-101 monomer. These HOF-101 derivatives, which are isostructural to the parent HOF-101, were used to immobilize phosphotriesterase (PTE). The enzyme loading efficiencies ranged from 64.7% to 70.7%, indicating that the substituents had little effect on PTE binding, which primarily relies on carboxyl-residue interactions. Kinetic studies revealed that the hydrophilic -NH₂-functionalized HOF-101 (PTE@HOF-101-NH₂) exhibited the highest catalytic efficiency (1.43 × 10⁸ M⁻¹ s⁻¹), 2.27 times that of free PTE, while the hydrophobic -CH₃ analogue showed reduced activity. Notably, PTE@HOF-101-F demonstrated superior acid resistance (70% relative activity at pH 2) and long-term thermal stability (70% activity retention after 6 h at 70 °C), outperforming other derivatives. In contrast, PTE@HOF-101-NH₂ showed the highest activity under mild conditions but suffered from framework dissolution under prolonged harsh treatments. This work demonstrates that fine-tuning the HOF channel microenvironment is an effective strategy to enhance enzyme activity and stability, providing a platform for designing advanced immobilized enzyme systems. Full article