Search Results (661)

High friction and drag are among the challenging subjects for constructing water-based drilling fluids available in horizontal drilling. Lubricants play a major role in mitigating friction of water-based drilling fluids, and thus, developing new lubricants is necessary for efficient horizontal drilling. In this work, a generation 1.5 (1.5G) hyperbranched polyamide-amine P(EDA-MA-OA), which serves as a candidate for a traditional lubricant with linear conformation, was newly synthesized via a divergent approach. A set of physicochemical characterizations was carried out on P(EDA-MA-OA) to confirm its effective synthesis. The results indicated that P(EDA-MA-OA) has a nanoparticulate morphology with a size of approximately 100 nm. Its molecular structure shows strong thermal stability, with initial thermal decomposition occurring at 146 °C. The water-based drilling fluid formulated with P(EDA-MA-OA) as the lubricant exhibits effective comprehensive properties and, in particular, the lubrication coefficient was 0.067, comparable to that of the oil-based drilling fluid, indicating enhanced lubricity by the incorporation of the hyperbranched polymer. The results of molecular simulations show that P(EDA-MA-OA) possesses a unique “basket-like” architecture, with C18 long chains enveloping the central active segments, namely the carbonyl (-C=O) and amide (-CO(NH₂)) groups. When interacting with montmorillonite (MMT) particulates, the active groups can interact with MMT, allowing the eight C18 branched terminal chains to form a “molecular brush” with a normal orientation toward the MMT interface, which can serve as a hydrophobic lubricating film to improve lubricity. A lubrication model was finally proposed to rationalize the enhanced lubricity from the hyperbranched polymers in the water-based drilling fluid. Full article

This investigation focused on isoniazid (INH)—saccharin (SAC) salts. One hydrate and one anhydrous INH-SAC salt form were synthesized and characterized spectroscopically by Raman and infrared spectroscopy. Solvent (methanol, acetone, acetonitrile)-assisted synthesis in the presence of water, or in water, resulted in production of the monohydrated form of the salt (MH: (INH+H)⁺/(SAC–H)⁻.H₂O). The anhydrous form (A: (INH+H)⁺/(SAC–H)⁻) was obtained using the same synthesis method but in the absence of water or, together with the hydrate, in the presence of traces of water. Differential scanning calorimetry studies revealed that the hydrate can be converted into the anhydrous form of the salt upon heating, with the latter melting at a T_m (onset) of 131.7 ± 0.5 °C. Melting was followed by a reaction between isoniazid and saccharin leading to saccharin ring opening and formation of a new covalent hydrazide–amide derivative, via nucleophilic acyl substitution at the saccharin carbonyl. The newly formed adduct, 2-[2-(pyridine-4-carbonyl)hydrazine-1-carbonyl] benzene-1-sulfonamide, melts at T_m (onset) = 204.4 ± 0.5 °C. The crystal structures of the hydrate and of the anhydrous form were determined by single-crystal X-ray diffraction, and the dominant intermolecular interactions in the crystalline INH-SAC salts were evaluated using Hirshfeld surface analysis. To complement the experimental results, density functional theory (DFT) calculations were performed both on relevant isolated structural units and on the two salts, employing fully periodic DFT methods. Full article

The thiourea grafting method can effectively improve the ability of activated carbon to recover chloroauric acid (AuCl₄⁻). Conventional grafting strategies rely on acyl halide reactions using reagents such as SOCl₂ and CH₂Cl₂, which suffer from instability and high toxicity. Herein, we propose a green grafting strategy for thiourea by activating carboxyl groups with EDC-HCl/NHS in acetonitrile, followed by the amidation reaction to obtain thiourea-modified carbon (AC-NCS). FT-IR and XPS analyses confirm the successful grafting of thiourea onto the activated carbon surface. Compared with pristine activated carbon, the adsorption capacity of AC-NCS is 104.8 mg/g, increased by 5.76 times. Furthermore, it maintains a recovery rate of 84.2% after three cycles. XPS and FT-IR further reveal that adsorption occurs on the thiourea sulfur atoms (C=S) and protonated primary amines(-NH₃⁺), and the recovery of chloroauric acid is achieved through a synergistic “reduction–electrostatic attraction” mechanism. This method reduces the dependence on highly toxic reagents and provides a promising approach for the efficient and green recovery of gold from secondary resources. Full article

This article details the synthesis and structural characterization of a new metalloid germanium cluster 3 with bulky amide ligands. The cluster features a Ge₆ core stabilized by four -N(Si^tBuMe₂)₂ ligands and was obtained via reduction of the amido trichlorogermane 2 using potassium chips in toluene. Single-crystal X-ray diffraction analysis revealed that the Ge₆ core adopts a butterfly-shaped geometry with a Ge-Ge dumbbell unit, which contains two unsubstituted germanium atoms exhibiting prominent lone-pair characteristics. The Ge₆ core can also be classified as a nido cluster, with a cluster-bonding-electron count of 16, perfectly satisfying the 2n + 4 electron-counting rule. Combining the structural features of this nido cluster with the bond length distribution in the folded four-membered ring suggests that the Ge4 ring features a certain degree of electron delocalization. Additionally, two bis(amido)-substituted germylenes (4 and 6) were isolated and structurally characterized. They exhibit analogous structural features, with each germanium center adopting a two-coordinate V-shaped configuration, the Ge–N bond lengths being very similar, and the nitrogen atoms adopting a planar triangular geometry. Notably, compound 6, bearing bulkier -N(SiⁱPr₃)₂ substituents, exhibits a significantly larger N-Ge-N bond angle (120.58°) compared to the corresponding value of 113.54° observed for compound 4 with -N(Si^tBuMe₂)₂ substituents. This clearly demonstrates that the steric bulk of the substituents exerts a remarkable influence on the molecular geometry and σ-donor ability of the lone pairs on germanium centers. Full article

Magnetic covalent organic frameworks (MCOFs) offer efficient adsorption via designable pore channels and active sites, along with rapid magnetic separation due to their intrinsic superparamagnetism. However, physical mixing or non-covalent assembly often leads to weak binding, causing the leaching or detachment of magnetic components during use, and compromises the well-defined crystallinity of the COF. In this study, we employed an in situ synthesis strategy at room temperature based on amidation and Schiff base reactions to fabricate a magnetic TAPT-DHTA-COF with good crystallinity and superparamagnetism. This material was used as a magnetic solid-phase extraction (MSPE) adsorbent to establish an MSPE-GC-MS/MS method for the determination of amide herbicides (AHs). The TAPT-DHTA-COF is rich in hydroxyl groups, which form strong hydrogen bonds with the polar AH molecules. In a green tea matrix, six AHs showed good linearity within the concentration range of 1–500 ng g⁻¹, with correlation coefficients ranging from 0.9910 to 0.9982. The limits of detection were between 0.25 and 0.73 ng g⁻¹, spiked recoveries ranged from 80.1% to 94.8%, and relative standard deviations were below 6.2%. This work offers an improved synthesis strategy for novel magnetic COFs and insights into their application in adsorbing polar pesticides. Full article

Heavy metal contamination of water by cadmium (Cd²⁺) and silver (Ag⁺) represents a significant environmental concern due to their toxicity and persistence. In this study, peptide-functionalized resins were evaluated as bio-inspired adsorbent materials for metal removal from aqueous solutions. Glycine-based and histidine-containing peptide sequences were synthesized via solid-phase peptide synthesis and immobilized onto Wang and Rink amide resins, with and without N-terminal acetylation. Adsorption capacity (Q, mg g⁻¹) was determined for each material. The results showed that adsorption performance strongly depends on both peptide structure and metal type. Higher adsorption capacities were consistently observed for Cd²⁺ (up to 7.9 mg g⁻¹) compared to Ag⁺ (up to 2.4 mg g⁻¹). Interestingly, histidine-containing resins exhibited superior performance, likely due to the presence of imidazole groups that enhance metal coordination. In contrast, the influence of resin type and N-terminal acetylation was less consistent, suggesting a secondary role of these factors. Overall, the findings provide an initial screening or proof-of-concept for peptide-functionalized resins and highlight the potential of these peptidyl resins as effective adsorbent materials for the removal of heavy metals from aqueous environments. Full article

Micro(nano)plastics (MNPs) represent a pervasive and escalating threat to global ecosystems and human health. This review provides a critical synthesis of MNPs’ exposure risks across marine, atmospheric, and terrestrial compartments, with a distinct emphasis on identifying cross-media linkages and methodological inconsistencies that limit current risk assessments. Within marine environments, pollution hazard indices reveal significant spatial heterogeneity, yet their utility is constrained by the absence of toxicity weighting and particle characteristic integration. Atmospheric exposure profiles show variable risks, and the MNPs’ concentration in indoor air (up to 15.8 particles/m³) is significantly higher than in outdoor environments, posing a greater inhalation risk to infants and children who spend more time indoors. A marked increase in MNPs’ concentrations within agricultural soils is identified, where the MNP content in mulched soils (average: 570.2 particles/kg) is more than twice that of non-mulched soils (259.6 particles/kg). Critically, studies have now detected MNPs within human tissues, including the blood, intestines, liver, kidneys, tonsils, and brain, highlighting an urgent need to elucidate their multi-organ toxicity mechanisms, with a novel synthesis of gut–brain axis disruption and transgenerational effects. By integrating exposure dynamics with mechanistic toxicity data, this review advances a cross-system framework that identifies priority research directions, namely standardized detection methodologies, combined pollutant toxicity, and cross-system toxicity mechanisms, which are essential for informing mitigation strategies amid this escalating public health crisis. Full article

The synthesis of hydroxamic acids from sterically hindered substrates, such as abietane-type resin acids, remains a synthetic challenge due to the congestion of the tricyclic skeleton. This study reports an efficient one-pot protocol for the direct conversion of abietic and dehydroabietic acids into their corresponding hydroxamic derivatives, achieving 65% and 74% isolated yields, respectively. Systematic screening of activating agents identified diethyl chlorophosphate (DCP) as the reagent for the hydroxyamidation. A critical finding of this work is that the optimization of the isolation process specifically minimizing the water amount during aqueous work-up was key to recovering these polar products and preventing important yield loss. The reaction proceeds through diethyl phosphate mixed anhydride intermediate, which was successfully isolated, providing direct experimental evidence of the activation pathway. The reaction mechanism was further elucidated using Density Functional Theory (DFT) calculations at the M062X/6-31G** level, identifying a concerted transition state for the simultaneous addition of hydroxylamine and expulsion of the phosphate group. Furthermore, the study rationalizes the observed chemoselectivity; although the ester is the more stable thermodynamic product, the formation of the N-hydroxy amide is kinetically favored through a substantially lower activation barrier. This combined experimental and theoretical approach establishes a practical and scalable methodology for the functionalization of abundant similar natural terpenoids. Full article

Halloysite nanotubes (HNTs), composed of an aluminosilicate framework, are naturally abundant, biocompatible, and sustainable clay minerals with a tubular morphology and tunable surface chemistry, making them attractive platforms for targeted, multifunctional drug delivery systems. In this study, a zinc ferrite integrated halloysite nanocomposite (ZnFe₂O₄/HNT) was developed via a one-pot synthesis approach for sustained release of cisplatin (Cp), aiming to reduce systemic toxicity and enhance cell-specific activity. The nanocomposites were further functionalized by integrating Cp (Cp: ZnFe₂O₄/HNT ratio 0.05) and folic acid (ZnFe₂O₄/HNT/Cp: FA ratio 0.05), followed by PEGylation (0.17 µL/mg of ZnFe₂O₄/HNT/Cp/FA/PEG). The structural and surface characteristics, phase, interfacial interactions (FA and Cp), and colloidal stability of nanoformulations were systematically investigated using powder X-ray diffraction analysis (XRD), Fourier transformed infrared (FT-IR) spectroscopy, zeta potential analysis, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), high-resolution transmission electron microscopy (HRTEM), and diffuse reflectance UV–visible (DRS-UV-Vis) spectroscopy. The results confirmed that ZnFe₂O₄ integration preserved the clay’s tubular framework while inducing nanocrystallization of both ferrite and cisplatin, indicating molecular dispersion within the clay matrix. Functionalization with FA (ZnFe₂O₄/HNT/Cp/FA) promoted amide bond linkage, modulated Cp-FA interactions, and significantly enhanced cumulative Cp release compared to the non-functionalized system ZnFe₂O₄/HNT/Cp (10.3% at 72 h vs. 34.4% at 72 h) under tumor acidic conditions (pH 6.6). PEGylation maintained the controlled release profile while improving dispersion stability. In vitro cytotoxicity studies revealed that FA-conjugated nanocomposites exhibited enhanced, time-dependent anticancer activity against HeLa cervical cancer cells, with reduced toxicity toward normal fibroblasts, indicating preferential cellular uptake via folate receptor-mediated mechanism. Overall, this work demonstrates that FA-functionalized ZnFe₂O₄/HNT nanocomposite provides an effective clay-based platform for modulating Cp release and enhancing folate receptor protein-mediated targeted therapy for cervical cancer. Full article

The fundamental purpose of education—preparing new generations to be contributing members of society—remains constant, yet achieving this has become increasingly complex amid multifaceted technological, cultural, economic, and social transformations. Educational leaders worldwide continuously seek innovative pedagogical models addressing diverse learner needs and rapid societal changes. However, this article challenges the assumption that educational quality requires constant novelty, arguing that solutions lie in the innovative integration of established pedagogical theories developed over the past 150 years by scholars such as Dewey, Vygotsky, Piaget, Feuerstein, Gardner, Freire, and others. The article’s primary objective is to encourage education leaders and teacher educators to reconceptualize innovation by prioritizing pedagogical integration over continuous adaptation to rapidly expanding domain-specific knowledge and emerging technologies. Accordingly, this article employs a conceptual synthesis of major pedagogical approaches to equip educators with theoretical foundations and practical tools to foster learner independence, critical thinking, and holistic development across cognitive, emotional, and social domains. It will also promote inclusion through a practical framework integrating pedagogical theories, addressing diversity from a dual perspective, recognizing that both teachers and learners bring unique characteristics, strengths, and needs. Moreover, developing independent learners requires empowering teachers to cultivate unique professional methodologies grounded in integrated pedagogical understanding, so that a shift from innovation-centered to integration-centered teacher education may serve as a sustainable path toward educational quality and academic excellence. Full article

Harsh modern industrial working conditions require high-performance lubricants, but traditional additives are limited by single functionality and poor compatibility, driving the development of multifunctional alternatives. Two novel hindered phenolic amide–esters (MADE, DAME) were synthesized and characterized. Their thermal/storage stability, antioxidant and tribological properties in synthetic oil were evaluated, with commercial 1010 and T203 as references. DFT calculations and worn surface analysis were also employed to clarify the lubrication mechanism. The results indicate that MADE exhibits better thermal/storage stability, comprehensive antioxidation and lubricating performance than DAME, with residual mass of 85.3% and 73.2% at 300 °C, respectively. A total of 1 wt.% MADE shortens the running-in period to 200 s (vs. 300 s for base oil), reduces the average. WSD by 12.1% and wear volume by 60.2%. Mechanistically, MADE adsorbs strongly on metal surfaces and forms a protective tribofilm via tribochemical reaction, exhibiting synergistic antioxidant and anti-wear effects. This work establishes a novel and sustainable paradigm for developing next-generation, multifunctional lubricant additives with high performance. Full article

A novel dual-imidazoline ring quaternary ammonium salt corrosion inhibitor (TN-IM) was rationally synthesized via a three-step sequential reaction, using hydroxyethyl ethylenediamine and tetradecanedioic acid as starting materials, with benzyl chloride as the quaternizing reagent. The synthetic process involved amidation at 160 °C for 4 h, cyclization at 220 °C for 3 h, and quaternization at 70 °C for 3 h, respectively. Fourier transform infrared spectroscopy and proton nuclear magnetic resonance were employed to characterize the chemical structure of TN-IM, confirming its successful synthesis. The corrosion inhibition performance of TN-IM was evaluated by the static weight loss method and electrochemical measurements, while the corrosion products and surface morphology of N80 carbon steel were analyzed via energy-dispersive X-ray spectroscopy and scanning electron microscopy. Static weight loss tests conducted in 3.5 wt% of a NaCl solution saturated with 0.6 MPa CO₂ at 60 °C for 24 h revealed that TN-IM at a concentration of 0.15 mmol/L exhibited a corrosion inhibition efficiency 1.86% higher than that of a single-imidazoline ring quaternary ammonium salt inhibitor. Potentiodynamic polarization measurements demonstrated that TN-IM functions as a mixed-type corrosion inhibitor, with a predominant inhibitory effect on the anodic reaction on N80 steel. Electrochemical impedance spectroscopy results indicated that TN-IM molecules can adsorb onto the active sites of the N80 surface, thereby retarding the corrosion process by suppressing the charge transfer step in the electrochemical corrosion reaction. This study establishes a new paradigm for the synthesis of high-efficiency imidazoline-based CO₂ corrosion inhibitors with multiple adsorption sites, holding significant implications for corrosion control in harsh industrial environments. Full article

8-Hydroxy-dihydroergotamine is the major human metabolite of the anti-migraine drug dihydroergotamine and is required, along with a stable isotope-labelled derivative, to aid metabolic studies. An efficient, scalable synthesis of the unlabelled compound is described via the coupling of dihydrolysergic acid to the tricyclic amino compound (2R,5S,8R,10aS,10bS)-2-amino-5-benzyl-10b-hydroxy-8-methoxy-2-methyltetrahydro-8H-oxazolo[3,2-a]pyrrolo[2,1-c]pyrazine-3,6(2H,5H)-dione. The tricycle was obtained by a convergent synthesis combining precursors from suitably protected L-glutamic acid and L-phenylalanine, and 2-bromo-2-methylmalonic acid. For the labelled molecule, the tricyclic precursor contained a pentadeutero benzyl group derived from [2,3,4,5,6-²H₅]L-phenylalanine. Considerable experimentation was required to achieve optimal activation of dihydrolysergic acid for efficient amide formation with the tricycle’s amino function affording 8-methoxy-dihydroergotamine. The stereochemical integrity of an intermediate in this synthesis, ethyl (2R,5S,8R,10aS)-5-benzyl-10b-hydroxy-8-methoxy-2-methyl-3,6-dioxooctahydro-8H-oxazolo[3,2-a]pyrrolo[2,1-c]pyrazine-2-carboxylate, was validated by crystal structure analysis. Acid-catalysed hydrolysis of 8-methoxy-dihydroergotamine gave 8-hydroxy-dihydroergotamine. Pentadeuterated 8-hydroxy-dihydroergotamine was obtained in an analogous manner from [2,3,4,5,6-²H₅]L-phenylalanine. Both 8-hydroxy-dihydroergotamine and its ²H₅-derivative were obtained as an equilibrating mixture of C-8 epimers (diastereomers), with the major isomer having (R)-configuration according to ¹H NMR analysis. The syntheses described enable the routine synthesis of 50–100 mg quantities of each target molecule. Full article

Cyclodepsipeptides constitute a structurally diverse class of natural products composed of amino acid and hydroxy acid residues interconnected through both amide and ester bonds. Among them, xylaroamide A, a cyclic heptadepsipeptide, was recently identified from an endolichenic Xylaria species via a molecular networking-guided discovery approach. Despite xylaroamide A exhibiting intriguing structural features and notable bioactivity potential, its total synthesis has thus far remained unexplored. Herein, we report the first total synthesis of xylaroamide A, achieved through a hybrid solid/solution-phase synthetic approach. The linear precursor was assembled in accordance with the native amino acid sequence via Fmoc-based solid-phase peptide synthesis, incorporating the preassembled ester fragment at a later stage of assembly. Subsequent macrocyclization took place under high-dilution conditions to furnish the target cyclodepsipeptide. The structure of the synthetic product was confirmed by means of optical rotation and NMR and MS spectroscopic analyses, which exhibited good agreement with the reported data for the natural product. This work establishes a reliable and efficient synthetic route to xylaroamide A and provides a foundation for further bioactivity and structure optimization investigations. Full article

Ceramides, sphingolipids produced from fatty acids linked to sphingosine and an amide, are structural elements of cellular membranes and lipoproteins. These molecules also retain biological effects in key cellular pathways such as oxidative stress and inflammation, apoptosis, and fibrosis, with a role in the onset and development of many pathophysiological conditions, including obesity, diabetes, and insulin resistance. Increasing evidence suggests that different nutrients and dietary patterns may affect ceramide levels, both negatively (e.g., fructose and the Western diet), whereas others improve the ceramide profile (e.g., ω-3 PUFAs, resveratrol, vitamin D, and the Mediterranean and the Nordic diets). Thus, ceramide nutritional modulation could represent a simple, additive, and reliable tool to improve metabolic health. This review focused on the role of ceramides in the pathophysiology of diabetes and obesity, as well as their pathogenetic mechanisms of action. Ceramides are increasingly recognized as “dynamic metabolic interfaces” linking nutrition and disease. This review aims to address a critical gap by synthesizing recent evidence on how dietary interventions, in addition to pharmacological approaches, can specifically target the enzymatic pathways involved in ceramide synthesis to enhance metabolic health. Thus, this review offers a concentrated analysis of the response of specific ceramide species, such as Cer16:0 and Cer18:0, to distinct dietary factors. Additionally, it incorporates emerging evidence on the role of gut microbiota in the biotransformation of sphingolipids, thereby adding a contemporary dimension to the established nutritional perspective. Full article