Search Results (3,597)

The chemical composition and molecular structure of the pitch-like products obtained by liquid-phase reaction of bituminous coal with heavy hydrocarbon fractions of coal and petroleum origin as solvents at a moderate temperature were comprehensively characterized in terms of a new aromatic feedstock for needle coke and other valuable high-tech carbon materials. The molecular parameters of the products were characterized by using FTIR, ¹H NMR, ¹³C NMR and XPS. Liquid-phase chromatography was used to analyze benzo(a)pyrene (BaP) as a carcinogenicity marker. The chemical composition and the characteristics of the molecular structure of the products were shown to depend greatly on the solvent used. The product obtained using coal tar as a solvent was highly aromatic, its polyaromatic nuclei consisted predominantly of protonated and pericondensed cycles sparsely substituted by CH₃ and occasionally CH₂ groups. The product obtained using petroleum-derived heavy gas oil as solvent was much less aromatic and prone to autogenous surface oxidation. Its aromatic nuclei contained mainly protonated and highly alkylated catacondensed chains. The intermediate structural parameters were characteristic of the product obtained using binary solvent. A remarkable feature of the pitch-like products obtained was a reduced BaP concentration (up to 40 times compared to typical coal-tar pitch). In terms of the molecular structure, the pitch-like products obtained by low-temperature dissolution of coal can serve as a new polyaromatic feedstock with a reduced carcinogenicity for the production of valuable high-tech carbon materials, needle coke, in particular. Full article

Purine-1,4,7,10-tetraazacyclododecane (cyclen) conjugate was designed to study its Cu²⁺ ions complexation capability. Several synthetic approaches were tested to achieve the target compound. The optimal approach involved stepwise modifications of purine N9, C8, and C6 positions that, in nine consecutive steps, provided purine–cyclen conjugate. The synthetic sequence involved Mitsunobu-type alkylation at N9 and iodination at C8, followed by Stille, S_NAr, CuAAC, and alkylation reactions. The designed purine–cyclen conjugate is able to complex Cu²⁺ ions in both the cyclen part and between the purine N7 and triazole N2 positions. The complexation pattern and equilibrium were studied using the NMR titration technique in MeCN-d₃ and absorption spectra. Full article

This study employs ab initio metadynamics to simulate the carbonization of Si(001) surfaces with chemical vapor deposition at a temperature of 1423 K. We reveal the complete reaction mechanism, including the beginning of silicon carbide crystal formation. The existence of surficial native oxide is incorporated into the theoretical model. The mechanism determination includes clarification of all intermediate products and transition states. The free-energy surface of the reaction chain has been found. Carbonization initiates with alkylated surface products and continues with consecutive dehydrogenation steps. Carbon is integrated in the volume, near the crystal surface, only if no covalent interactions with hydrogen atoms remain. The native oxide was not found to prohibit the process of carbonization. The oxygen atoms have certain surface mobility at high temperatures. It was revealed that hypervalency of carbon atoms is possible in transition state structures. The theoretical activation free energy of the rate-determining step was found to be only 166 kJ/mol. This work sheds light on the advantage of the practical use of Si(001) substrates for the synthesis of silicon carbide and Si-O-C glasses using direct carbonization via chemical vapor deposition. We also aim to enable more methodical designs of future synthetic routes and better-informed decisions for experimental investigations. Full article

Chemiresistive sensors integrated with functionalized conductive polymers have emerged as promising candidates for wearable applications, offering adequate protection against highly toxic and widely prevalent organophosphate compounds, due to their high sensitivity, room-temperature operation, and straightforward fabrication process. However, these chemiresistive sensors exhibit poor resistance to water vapor due to the intrinsic properties of these conducting polymers, likely leading to false sensor alarms. In this study, we engineered a series of water-vapor-resistant, yet organophosphate-sensitive, conducting polymers by electro-copolymerizing hexafluoroisopropanol (HFIP)-grafted 3,4-ethylenedioxythiophene (EDOT-HFIP) with EDOT comonomers bearing hydrophobic alkyl groups of varying lengths (ethyl, butyl, and hexyl). The typical results indicated that increasing the alkyl length and alkyl-bearing EDOT comonomer composition significantly enhanced the water resistance of the EDOT-HFIP copolymers and the copolymer-integrated chemiresistive sensor, but this improvement came at the unacceptable cost of compromising the organophosphate sensitivity. To address this issue, we developed a surface-driven phase-segregation strategy to enrich the alkyl chains on the surface while concentrating the HFIP groups beneath it by treating the silica substrates using oxygen plasma before polymer spin coating, thus decoupling and optimizing the two mutually competing characteristics. Finally, the chemiresistive sensor integrated with the EDOT-HFIP copolymer containing 10% hexyl-grafted EDOT comonomer exhibited an organophosphate (DMMP) resistive response 657 times higher than that to water vapor, and more than two times that of a PEDOT-HFIP sensor, while preserving the original specific sensitivity of the PEDOT-HFIP sensor. Furthermore, it demonstrated a markedly improved shelf storage stability, being directly exposed to air for 14 days without any special protection. We envision that this surface-driven phase-segregation strategy could offer a promising solution to the significant challenge of air moisture interference in highly sensitive polymer sensors, promoting their practical use in real-world applications. Full article

Agricultural land abandonment is a widespread phenomenon found in many regions of the world. There are many studies on post-agricultural changes in temperate, arid, semi-arid regions, etc., but studies of such soils in boreal or Arctic conditions are rare. Our study aims to fill the gaps in research on the processes of post-agricultural soil transformation, with a focus on the harsh climatic conditions of the Arctic and Subarctic regions. Parameters of soil organic matter (SOM) are largely reflected in the quality of soil, and this study investigates the dynamics of SOM properties in Subarctic agricultural soils in process of post-agrogenic transformation and long-term fertilization. Using a chronosequence approach (0–25 years of abandonment) and a reference site with over 90 years of fertilization, we performed elemental (CHN-O) analysis, solid-state ¹³C NMR spectroscopy of SOM, PXRD of soil and parent material, and multivariate statistical analysis to identify the connections between SOM composition and other soil properties. The results revealed transient increases in soil organic carbon (SOC) during early abandonment (5–10 years; 3.75–4.03%), followed by significant declines after 25 years (2.15–2.27%), driven by mineralization in quartz-dominated soils lacking reactive minerals for organo-mineral stabilization. The reference site (the Yamal Agricultural Station) maintained stable SOC (3.58–3.83%) through long-term organic inputs, compensating for poor mineralogical protection. ¹³C NMR spectroscopy highlighted shifts from labile alkyl-C (40.88% in active fields) to oxidized O-alkyl-C (21.6% in late abandonment) and lignin-derived aryl-C (15.88% at middle abandonment), reflecting microbial processing and humification. Freeze–thaw cycles and quartz dominance mineralogy exacerbated SOM vulnerability, while fertilization sustained alkyl-C (39.61%) and balanced C:N (19–20) ratios. Principal Component Analysis linked SOC loss to declining nutrient retention and showed SOM to be reliant on physical occlusion and biochemical recalcitrance, both vulnerable to Subarctic freeze–thaw cycles that disrupt aggregates. These findings underscore the fragility of SOM in Subarctic agroecosystems, emphasizing the necessity of organic amendments to counteract limitations of poor mineralogical composition and climatic stress. Full article

Surface treatment is essential for cementitious materials. Siloxane is a material that can potentially be applied in surface treatment, as it possesses the advantages of both inorganic and organic surface treatment materials for cement. Organotin, serving as a neutral catalyst, performs well in improving the performance of siloxane coating. In this work, the effect of organotin on the surface treatment performance of siloxane was studied for application in cementitious materials, including surface hardness and waterproofing properties. Organotin had little effect on the waterproofing of cement paste treated with siloxane. However, the addition of organotin positively impacted the surface hardness of cement paste treated with MTMS, which increased by 105.1%. The function of organotin was analyzed through XRD, FTIR, SEM, and pore structure characterizations. Organotin can speed up the gelation of siloxane, thus consuming more portlandite in cement. The negative effect of the alkyl group could be partially reduced by promoting the condensation of the alkoxy group. This indicated that treating siloxane with organotin is valuable for improving the durability of cement-based materials, increasing their surface hardness without affecting waterproofing. Full article

The sensing of surfactants is a topic of interest for industrial and environmental purposes. Polydopamine-coated magnetite (Fe₃O₄@PDA) can be a relevant support for the detection of cationic surfactants in water samples. The negative charge in the surface of the PDA material favors the interaction with cationic molecules and allows the design of a chemoreagent for the detection of cationic surfactants by displacement or competition with methylene blue (MB). Magnetite nanoparticles with single and double PDA coating have been prepared and characterized. The PDA surface effectively coats magnetite nanoparticles with a thickness of 5 or 19 nm and a Z potential of −30 mV. The adsorption of MB follows second-order kinetics, and up 33 mg of dye can be loaded in 1 g of the support. The cationic surfactants can displace MB from the Fe₃O₄@PDA surface, coloring the solution. Thus, it can be applied for the analysis of water samples. The system is selective towards cationic molecules with long alkyl chains, but the response is influenced by high concentrations of divalent cations. The material can be used following diverse sensing protocols with a detection range from 4 × 10⁻⁶ to 2 × 10⁻⁴ M. The simplicity of its handling together with the naked eye detection allows its application in kits for field analysis with screening purposes. Full article

The oxidation of imines may give several products, such as oxaziridines, nitrones, amides, and other rearranged compounds. Therefore, its selectivity is a challenge that various methods have to face. The controversial selectivity of the oxidation of imines using urea hydrogen peroxide (UHP) catalyzed by methyltrioxorhenium (MTO) is addressed by varying the solvent, temperature, reaction time, amount of oxidant, and catalyst used. The reactivity and selectivity of the oxidation of imines proved to be particularly sensitive to the type of solvent. The use of methanol furnished the corresponding nitrones as the exclusive products, except for very hindered N-tert-alkyl substituted substrates. Using the ionic liquid [bmim]BF₄ as a solvent resulted in a complete switch in reactivity and selectivity. N-methyl substituted imines gave the corresponding amides, while imines with bulkier substituents at nitrogen did not show any reactivity. An exception was the C-phenyl,N-tert-butyl imine—the only substrate that was oxidized to the corresponding oxaziridine, albeit with low conversion. The results reported herein reaffirm the oxidation of imines with UHP/MTO in MeOH as the method of choice for their interconversion to nitrones. Full article

A series of new 3-alkyl substituted cis- and trans-(±)-3,4-dihydro-6,7-dimethoxy-1-oxo-1H-isochromene-4-carboxylic acids (cis-/trans-1–3) was synthesized through the reaction of 6,7-dimethoxyhomophthalic anhydride with aliphatic aldehydes of varying chain lengths. Their structure and configuration were elucidated using spectral methods, including ¹H, ¹³C, DEPT-135 NMR, FTIR, UV-Vis, and HRMS analyses. A deductive conformational analysis was performed for determining the preferred conformations in solution and to explain the observed vicinal coupling constants. Full article

Two-dimensional (2D) metal-halide perovskites with highly efficient room-temperature phosphorescence (RTP) are rare due to their complex structures and intricate intermolecular interactions. In this study, by varying the alkyl chain length in organic amines, we synthesized two 2D metal-halide perovskites, namely 4-POMACC and 4-POEACC, both of which exhibit significant RTP emission. Notably, 4-POMACC demonstrates a stronger green RTP emission with a significantly longer lifetime (254 ms) and a higher photoluminescence quantum yield (9.5%) compared to 4-POEACC. A thorough investigation of structural and optical properties reveals that shorter alkyl chains can enhance the optical performance due to reduced molecular vibrations and more effective exciton recombination. Computational calculations further show that the smaller energy gap between S₁ and T_n in 4-POMA facilitates intersystem crossing, thereby improving RTP performance. Based on their remarkable phosphorescence properties, we demonstrated their applications in information encryption. This work offers a novel design strategy that could inspire the development of next-generation RTP materials. Full article

Chemotherapy-induced neutropenia (CIN) and chemotherapy-induced alopecia (CIA) are significant toxicities affecting cancer patients. CIN is a potentially fatal complication of chemotherapy caused by myelosuppression and increased infection susceptibility, while CIA, although not fatal, severely affects treatment adherence and mental health. This study provides a comprehensive comparative analysis of CIN and CIA, focusing on patient, disease, treatment, and genetic risk factors. Key risk factors for CIN and CIA include age, poor performance status, body mass index (BMI), laboratory abnormalities, and pre-existing comorbidities. Both toxicities were significantly associated with breast cancer patients, although CIN patients were more likely to have hematological cancer, and CIA patients were more likely to have solid tumors. Notably, anthracyclines, alkylators, and taxanes frequently induce both toxicities, although their timelines and clinical implications differed. There was no clear overlap between genetic predispositions and toxicities beyond single-nucleotide polymorphisms (SNPs) in the ABCB1 gene. This is the first study to directly compare CIN and CIA, offering insights into personalized oncology care. Understanding the risk factors implicated in the development of CIN and CIA will enable physicians to manage patient outcomes. Full article

Accurately identifying local interactions such as hydrophilicity and hydrophobicity is of critical importance in regulating the functions of amphiphilic biomolecules, but in situ identification methods for such interactions are still lacking. This study proposes a probe based on carbonyl (C=O) stretching vibration to study the hydrophilic and hydrophobic interactions in amphiphilic alcohol–water systems. A combination of theoretical calculations and Raman spectroscopy experiments is employed to investigate the molecular interactions of ethyl acetate C=O in an ethanol aqueous solution, as well as the reasons behind the splitting of spectral peaks. The results indicate that the spectral peak splitting of the C=O stretching vibration is attributed to ethyl acetate existing in different hydrophilic and hydrophobic environments. Specifically, the two low-wavenumber components arise from the formation of double and single hydrogen bonds between C=O and water or ethanol, respectively, while the high-wavenumber component is attributed to the interaction between C=O and the hydrophobic alkyl group. These findings suggest that the C=O stretching vibration of esters is sensitive to the surrounding hydrophilic and hydrophobic environments, thereby indicating its potential as a useful probe for identifying hydrophilic and hydrophobic interactions. Full article

Mine ramps, serving as a critical transportation hub in underground mining activities, are beset by severe issues of dust pollution and secondary dust generation. While dust suppressants are more efficient than the commonly used sprinkling methods in mines, traditional single-function dust suppressants are inadequate for the complex application environment of mine ramps. Building on the development of conventional single-function dust suppressants, this research optimized the components of bonding, wetting, and moisturizing agents. Through single-factor optimization experiments, a comparison was made of the surface tension water retention property and viscosity of diverse materials, thus enabling the identification of the primary components of the dust suppressant. By means of synergistic antagonism experiments, the optimal combination of the wetting agent and bonding agent with excellent synergy was ascertained. Ultimately, the wind erosion resistance and rolling resistance were measured through three-factor orthogonal experiments, and the optimal ratio of the dust suppressant was established. Specifically, fenugreek gum (FG) was selected as the bonding agent, cane sugar (CS) as the moisturizing agent, and alkyl phenol polyoxyethylene ether (Op-10) as the wetting agent. The research findings demonstrate that the optimal ratio of dust suppressant is 0.3 wt% fenugreek gum (FG) + 0.06 wt% alkyl phenol polyoxyethylene ether (Op-10) + 3 wt% cane sugar (CS). Under these conditions, the dust fixation rate can reach up to 97~98% at a wind speed of 8 m/s. The maximum rolling resistance can reach 65~73% after grinding the samples for 1 min. The surface tension of the solution is 13.74 mN/m, and the wetting performance improved by 81% compared to pure water. This dust suppressant is of great significance for improving the working environment of workers and ensuring the sustainable development of the mining industry. Full article

Aromatic and medicinal plants have been integral to human civilization for thousands of years, serving not only as vital components in traditional and modern medicine but also as sources of captivating fragrances that enhance our sensory experiences. The main objective of this study was to explore the chemical composition, antioxidant and antimicrobial properties, and in silico molecular docking attributes of Gardenia jasminoides essential oil (GJEO). The chemical compositions were determined using gas chromatography–mass spectrometry (GC-MS) analysis. The antioxidant activity was determined by 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and total antioxidant capacity (TAC) test. The antimicrobial activity was tested in vitro using three microbial strains (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus), and two fungal strains (Candida albicans and Aspergillus niger). In silico analysis by molecular docking was used to determine the interaction types of topoisomerase II receptors and the most important antioxidant and antimicrobial compounds (Eugenol, Methyleugenol, and α-Terpineol ligands). The obtained results highlight the presence of 25 volatile compounds including 5 new detected compounds: Methyleugenol (15.41%), 1-Undecyne (3.4%), 2,6,10-Dodecatrien-1-ol, 3,7,11-trimethyl- (1.11%), 2,5-Cyclohexadiene-1,4-dione, 2,6-bis(1,1-dimethylethyl)- (0.4%), and 5,9-Tetradecadiyne (0.32%). The antioxidant capacity of GJEO is around 1.25 µg equivalent of ascorbic acid/mL for TAC assay and IC50 = 19.05 µL/mL for DPPH test. GJEO exhibited significant antimicrobial activity, particularly against Pseudomonas aeruginosa, with a minimum inhibitory concentration (MIC) of 16.67 µL/mL. In silico molecular docking analysis revealed strong interactions between ethyleugenol characterized by multiple bonding interactions, including Pi–Alkyl and carbon–hydrogen bonds, while α-Terpineol formed hydrogen and alkyl interactions. These results underline the potential of Gardenia jasminoides essential oil as a promising source of bioactive compounds with antioxidant and antimicrobial properties, highlighting its possible applications in pharmaceuticals and natural therapies. Full article