13C Nuclear Magnetic Resonance Spectroscopy Research Articles

Synthesis, structural elucidation, biological screening, and density functional theory calculations of Cu(II), Ni(II), Mn(II), and Co(II) complexes of 20 Z‐N‐((Z)‐2‐(6‐nitrobenzo[d]thiazol‐2‐ylimino)‐1,2‐diphenylethylidene)‐5‐nitrobenzo[d]thiazol‐2‐amine Schiff base ligand

The emerging Schiff base‐derived metal complexes are the building blocks for biomedical applications. Herein, novel Schiff base N,N′‐[(1Z,2Z)‐1,2‐diphenylethane‐1,2‐diylidene]bis(6‐nitro‐1,3‐thiazol‐2‐amine) and corresponding Cu(II), Ni(II), Mn(II), and Co(II) metal complexes were successfully synthesized and characterized. The characterization of ligand and corresponding metal complexes was carried out by employing elemental analysis, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, mass spectroscopy, Fourier transform infrared spectroscopy (FTIR) analysis, molar conductance, magnetic susceptibility measurements, electronic spectra, electronic paramagnetic resonance (EPR) and density functional theory (DFT) studies. DFT calculations at B3LYP/6‐311+G** level of theory have been executed to examine the equilibrium geometry of the ligand and metal complexes. Furthermore, total energy, highest‐occupied molecular orbital (HOMO) and lowest‐unoccupied molecular orbital (LUMO), and Mulliken atomic charges were reckoned. Tetrahedral geometry was observed in the case of the Ni(II) complex, and octahedral geometries were discerned for Cu(II), Mn(II), and Co(II), complexes. Docking studies were performed against the newly synthesized analogs with the active site of Escherichia coli (PDB ID: 3t88), Staphylococcus aureus (PDB ID: 3q8u), Candida Albicans (PDB ID: 3qlw), and Aspergillus flavus (PDB ID: 4ynt) receptors to recognize the interactions between complexes and identify their probable binding sites. Synthesized analogs were examined for in vitro antimicrobial activity employing both minimum inhibitory concentration and disk diffusion method against the aforementioned pathogens. The result for these pathogens suggested metal compounds evince higher activity in comparison to the free ligand.

Preparation and Characterization of Dual-Modified Cassava Starch-Based Biodegradable Foams for Sustainable Packaging Applications.

Starch and its derivatives have recently emerged as a sustainable and renewable alternative for petroleum-based expanded polystyrene (EPS) and expanded polypropylene (EPP) foam materials. In this study, biodegradable foam materials were prepared from cassava starch using a novel dual modification technique, combining microwave treatment and freeze-drying. The foam materials were prepared from starch solutions microwaved over different intervals. The starch-based foam materials were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), 13C nuclear magnetic resonance (13C-NMR) spectroscopy, and compression set test. Moreover, the water absorption capacities and density values of the foam materials were measured according to ASTM standards. The biodegradability test was carried out according to the aerobic compost environment test. The lowest water absorption capacities of 65.56% and 70.83% were exhibited for the cassava starch foam sample (MWB) prepared at a 20 s microwave treatment time and immersed in distilled water for 2 and 24 h, respectively. Furthermore, the lightweight cassava starch-based foam materials displayed density ranging from 124 to 245 kg/m3. The biodegradation test exhibited significant biodegradation of over 50% after 15 days for all the foam materials prepared. These results suggest that the dual-modified cassava starch-based biodegradable foams show potential in sustainable packaging applications by replacing petroleum-based materials.

1-Ethyl-3-Methylimidazolium Cyanoborohydride Catalyzed Solvent Free Microwave Assisted One Pot Multicomponent Synthesis of Tetrahydrobenzo[ b]Pyran Derivatives

: We present a facile and environmentally benign protocol for the synthesis of tetrahydrobenzo[b]pyran derivatives via multi-component condensation of dimedon, malononitrile and different aromatic aldehydes in presence of 1-ethyl-3-methylimidazolium cyanoborohydride ([EMIm][BH3CN]) as catalyst under microwave irradiation. The one-pot synthesis, facile solvent-free condition and good isolated yield illustrate the utility of this green approach. The structural features are de-rived using analytical tools including Fourier Transform Infrared Spectroscopy (FT‐IR) and 1H and 13C Nuclear Magnetic Resonance (NMR) Spectroscopy. Electronic synthesis of tetrahydrobenzo[b]pyran derivatives by using catalytic action of 1-ethyl-3-methylimidazolium cyanoborohydride has been used to obtain maximum yield.

Characterization of grafting properties of ABS latexes: ATR-FTIR vs NMR spectroscopy

Acrylonitrile–Butadiene–Styrene (ABS) polymers have a complex microstructure which is formed during the grafting reaction of a polybutadiene seed latex. During the reaction, some styrene-acrylonitrile (SAN) chains are grafted onto the polybutadiene (PB) backbone chains, and this grafting is critical to achieve effective dispersion and compatibility of both phases. Therefore, accurate characterization of grafting properties helps understanding the polymerization mechanism as well as the final properties of the ABS polymer and its applications properties. In this work, the grafting properties of ABS latexes were determined by separation of the soluble and insoluble phase of the polymer, followed by the characterization of these phases using analytical techniques. Phase separation was carried out dispersing the latex in acetone followed by ultracentrifugation. The soluble and insoluble polymer phases were for the first time analysed by NMR spectroscopy to obtain the corresponding fractions of SAN and PB in each phase. The soluble fraction was analysed by liquid-state 1H Nuclear Magnetic Resonance (NMR) spectroscopy, whereas the insoluble fraction was analysed by solid-state 13C NMR spectroscopy. Moreover, both phases were analysed by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), and the results obtained are compared and discussed in this article. We found that the most accurate grafting properties are achieved by analysing the composition of the soluble and insoluble fraction by NMR spectroscopy.

Synthesis of (6-Methoxy-2,5-dinitro-quinoline-4-yl)-(5-vinyl-1-aza-bicyclo[2.2.2]oct-2-yl)-methanol) and In Vitro Assay Against Plasmodium falciparum 3D7

Quinine, a naturally happening alkaloid initially utilized for the treatment of muscle cramps, is currently most usually utilized to treat malaria. Symptoms of poisonous quinine, called Cinchonism, include wooziness, tinnitus (ringing in the ears), blurred vision, nausea, vomiting, serious adverse reaction to excessive quinine use, vision impairment and deafness. This research aimed to obtain more polar quinine derivatives using reactions with sulfuric acid and nitric acid to reduce toxicity. The reactions were performed analogously to the procedures reported in the literature. The characterization of reaction products utilizing proton (1H) and carbon-13 (13C) nuclear magnetic resonance (NMR) spectroscopy showed that the reaction using reagents led to nitration of the quinoline ring with the yields of 7.09 %. The IC50 value of >10.000 μg/mL was obtained from the antimalarial test against Plasmodium falciparum 3D7. The IC50 values proved that the synthesis products (6-Methoxy-2,5-dinitro-quinoline-4-yl)-(5- vinyl-1-aza-bicyclo[2.2.2]oct-2-yl)-methanol) was not potential for malaria treatment.

Importance of R-CH3⋯O tetrel bonding and vinyl⋯aryl stacking interactions in stabilizing the crystal packing of 2’,4’-dihydroxy-3’-methoxychalcone: Exploration of antileishmanial activity and molecular docking studies

A detailed experimental and theoretical investigation of a chalcone derivative 2’,4’-dihydroxy-3’-methoxychalcone (DHMC) isolated from Argentinean type-Zuccagnia propolis has been performed. The isolated compound was characterized by 1H and 13C Nuclear Magnetic Resonance (NMR), infrared (IR) and Raman spectroscopies and its crystal structure was solved by single-crystal X-ray diffraction (XRD). The molecular geometry of the title compound was investigated theoretically and a very good agreement between experimental and computed geometrical parameters and vibrational frequencies have been observed. The substance crystallized in the orthorhombic Pbcn crystal system, with Z= 8 molecules per unit cell. The molecular geometry of the molecule is mainly stabilized by intramolecular O-H⋯O(keto) hydrogen bonds. The structure reveals that the crystal packing is mainly governed by O-H⋯O and C-H⋯O hydrogen bonds. The supramolecular assembly of the compound in solid state is also stabilized by σ-hole tetrel bonding interactions (O⋯C) involving the O-atom of the hydroxyl and the carbon atom of the methoxy group. Other interactions such as C-H⋯π and vinyl⋯π stacking interactions are also relevant in the stabilization of the solid structure of DHMC. The interaction energies of the different self-assembled dimers have been estimated using DFT calculations and various computational tools including MEP surfaces, QTAIM, NBO and NCI plot analysis. The antileishmanial activity of DHMC indicates that the compound was active against the main specie that cause tegumentary leishmaniosis in Argentina. The computational molecular docking simulation was used to predict the binding potential of the title chalcone derivative against six different leishmanial protein targets.

Supramolecular dimers drive the reaction between CO2 and alkanolamines towards carbonate formation

In this work we revisited the mechanisms for CO2 absorption in pure alkanolamines (monoethanolamine, diethanolamine, 2 −amino−2 −methyl−1 −propanol, and ethylenediamine) and in their 30% (v/v) aqueous solution, leading to the corresponding carbonate or carbamate. Fourier-transform infrared and 13C nuclear magnetic resonance spectroscopies strongly suggest that in the aqueous medium the main product is carbamate, whereas in the pure alkanolamines or in an acetonitrile solution carbonate is formed. Density functional theory simulations indicate that when alkanolamine monomers are used, carbamic acid is the most stable product. On the contrary, alkanolamine dimers led mainly to a zwitterionic carbonate. The effect of the solvent was also studied showing that in aqueous medium alkanolamines react as monomers with CO2 to produce carbamates. In pure alkanolamines or in the presence of nonpolar solvents, the main species are the alkanolamine supramolecular dimers, which react with CO2 to form carbonates.

Synthesis and properties of binuclear ferrocene energetic compounds as combustion rate catalyst

AbstractIn order to improve the catalytic performance, oxidation resistance and thermal stability of neutral alkyl ferrocene‐based combustion rate catalysts, mononuclear ferrocene energetic compounds were designed and prepared, but four binuclear ferrocene energetic compounds were unexpectedly discovered during the synthesis compounds. The new compounds were characterized by single‐crystal X‐ray diffraction,1H and13C nuclear magnetic resonance spectroscopy, and high‐resolution mass spectrometry. The crystal structures of compoundsa,b,canddconfirmed that we have successfully prepared binuclear ferrocene nitrogen‐containing heterocyclic compounds. The thermogravimetric results revealed that most of the compounds exhibit high thermal stability. The electrochemical properties of the four compounds were examined by cyclic voltammetry (CV) and differential pulse voltammetry; the CV experimental results indicated that these compounds showed good electrochemical performance, which contributed to their burning rate catalytic activity in composite solid propellants. Differential scanning calorimetry was used to study the catalytic performance of the binuclear ferrocene energetic compounds for ammonium perchlorate (AP). The results show that these compounds have a good combustion catalytic effect on AP due to the increase in the number of ferrocene groups.

Molecular-level characteristics of soil organic carbon in rhizosheaths from a semiarid grassland of North China

Rhizosheaths are aggregated, sheath-like soils that physically adhere to root surface, and they form on herbaceous plant roots worldwide, especially in semiarid grasslands. Representing a strong root−soil−microbe interaction, the rhizosheaths are expected to have distinct soil organic carbon (SOC) signatures from rhizosphere soils of non-rhizosheath forming plants. However, such signatures remain unclear, which hinders our understanding of root effects on SOC cycling in grasslands. We compared SOC characteristics between rhizosheath and non-rhizosheath soils of eight herbaceous plant species, collected from a semiarid grassland of North China, using solid-state 13C nuclear magnetic resonance spectroscopy and biomarker analyses. We further examined the temporal dynamics of SOC characteristics of rhizosheath soils from early, middle, and late plant growth stages. Compared to non-rhizosheath SOC, rhizosheath SOC had more root inputs of both labile substrates (carbohydrates and free alkanoic acids) and relatively recalcitrant suberin- and lignin-derived compounds. Moreover, the labile inputs provided more substrates for microbial degradation of cutin-derived compounds. These indicators of labile substrate availability increased significantly from the early to late growth stages. Overall, our findings clarify the molecular characteristics of rhizosheath SOC and its temporal dynamics, both of which suggest a critical role of rhizosheath in shaping the rhizosphere microenvironment and regulating SOC cycling.

Nitrogenous gas formation mechanisms of chemically modified superfine pulverized coal during pyrolysis

ABSTRACT The pyrolysis products are affected by the O-containing groups in coal. The influences of the introduced O-containing groups on nitrogenous gas formation are rarely explored. To investigate this issue, superfine pulverized coal samples were modified by several kinds of selected chemical reagents. 13C nuclear magnetic resonance spectroscopy (NMR) experiments demonstrate that a considerable amount of carboxyl, hydroxyl structures is introduced into the carbon skeleton after peracetic acid modifications. X-ray photoelectron spectroscopy (XPS) experiments reveal that the content of quaternary nitrogen N-Q on the surface of the samples modified by peracetic acid remain unchanged in general. And oxidized nitrogen N-X structures are formed by the oxidation of pyridinic nitrogen N-6 and pyrrolic nitrogen N-5, which induces the proportion of N-X to increase more than 40%. Because of the introduction of O-containing functional groups, the discrepancy of nitrogenous gas composition has been found between the raw and modified samples during pyrolysis. The production of N2O soars between 200°C and 300°C. After H2O2 modifications, the formation paths of nitrogenous gas do not change significantly due to the absence of O-containing group introduction. This research uncovers that the introduced O-containing groups alter the formation paths of nitrogenous gas in coal during pyrolysis and elucidates the mechanism.

Polyethylene Waxes with Short Chain Branching via Steric and Electronic Tuning of an 8-(Arylimino)-5,6,7-trihydroquinoline-nickel Catalyst

Ten examples of nickel(II) halide complexes [8-{N(2,4-(C15H13)2-6-RC6H2N)}C9H8N]NiBr2 [R = Me (Ni1), Et (Ni2), iPr (Ni3), Cl (Ni4), or F (Ni5)] and [8-{N(2,4-(C15H13)2-6-RC6H2N)}C9H8N]NiCl2 [R = Me (Ni6), Et (Ni7), iPr (Ni8), Cl (Ni9), or F (Ni10)], each incorporating a sterically encumbered N,N-chelating 8-[2,4-bis(dibenzocycloheptyl)-6-R-phenylimino]-5,6,7-trihydroquinoline ligand, are disclosed. Full details for the preparation of these complexes as well as the zinc-mediated synthesis of precursor ligands L1–L5 are given. Structural characterization of Ni3(H2O), Ni6, Ni7(H2O), and Ni8(H2O) reveals halide-bridged dinuclear structures of the type (N,N)NiX(μ-X)2NiX(N,N) with the ortho-substituted dibenzocycloheptyl groups providing steric protection to each metal center. In the presence of ethylaluminum dichloride (EtAlCl2) or methylaluminoxane (MAO), Ni1–Ni10 displayed high activities for ethylene polymerization [≤6.17 × 106 g of PE (mol of Ni)−1 h–1 for Ni6/EtAlCl2 at 20 °C], generating low-molecular weight polyethylene waxes. Notably, catalysts incorporating a 6-alkyl group (Me, Et, or iPr) as the N-aryl substituent proved to be more active than their 6-halide (Cl or F) counterparts and formed relatively higher-molecular weight polymers (Mw range of 9.1–22.9 kg mol–1) with a narrow dispersity. Moreover, analysis of these waxes by 13C nuclear magnetic resonance spectroscopy showed that they typically possessed short chain branching (>83% methyl) with branching densities of 79–90 branches per 1000 Cs. In addition, chain end analysis revealed the presence of both vinyl (−CH═CH2) and internal vinylene (−CH═CH−) functional groups, highlighting the role of both β-H elimination and isomerization.

Sustainable Light‐Stimulated Synthesis of Cross‐Linked Polymer Microparticles

AbstractThe increasing demand for crosslinked polymer microparticles (PMPs) in advanced applications requires the development of new sustainable methods which can reduce the impact of the polymerization process on the environment. This research reports a new environmentally‐friendly light‐assisted polymerization method for the synthesis of highly cross‐linked polymer microspheres by combining light‐induced [2+2] cycloadditions with dispersion polymerization. Using naturally‐occurring coumarin as reactive moieties, this method allows the synthesis of highly crosslinked PMPs in the presence of UV light at room temperature without initiator. The effect of the reaction parameters such as monomer concentration, stabilizer and reaction time on the particle size and yield are investigated using a number of techniques including Fourier transform infrared spectroscopy, solid‐state13C nuclear magnetic resonance spectroscopy, and scanning electron microscopy. The results show the formation of highly crosslinked porous microspheres which demonstrate good thermal stability.

Functional role of a novel algicidal compound produced by Pseudoruegeria sp. M32A2M on the harmful algae Alexandrium catenella

A marine phytoplankton dinoflagellate, Alexandrium sp. is known to cause worldwide harmful algal blooms, resulting in paralytic shellfish poisoning. In this study, we isolated a novel compound secreted by the marine bacterium Pseudoruegeria sp. M32A2M, and showed that it displays algicidal activity against A. catenella (group I). The molecular structure of the compound was analyzed by using 1H nuclear magnetic resonance (NMR), 13C NMR, and gas chromatography-mass spectrometry, which revealed that the compound was a diketopiperazine, cyclo[Ala-Gly]. Cyclo[Ala-Gly] induced a rapid decrease in the active chlorophyll a content and maximal quantum yield of photosystem II, leading to membrane disintegration after 24 h of its treatment. It showed the highest algicidal effect against diketopiperazines and also showed specific algicidal activities against several dinoflagellate species, but not for diatom species. In particular, cyclo[Ala-Gly] caused the transcriptional downregulation of the photosynthesis-related membrane complex in A. catenella, but not in the diatom Chaetoceros simplex. Based on structural modeling, we elucidated that cyclo[Ala-Gly] has a structure similar to that of plastoquinone, which transfers electrons by binding to the photosystem II core proteins PsbA and PsbD. This suggests a novel role for cyclo[Ala-Gly] as a potential inhibitor of photosynthesis.

Heterogeneous development of micro- and meso-pores in shale kerogen: New insights from chemical structure analysis

The development of the pore network during the thermal cracking of organic matter in shale plays an important role in the storage and transport of gas. There are several reports concerning the relationships between pore development and chemical composition in kerogen, however, little research has been performed to investigate how the transformation of the chemical structure affects the heterogeneous development of pores. In this study, kerogen isolation was performed on nine Longmaxi Formation shale samples with different maturities, then the chemical structure and pore development of isolated kerogens were studied using low-pressure gas adsorption, 13C Nuclear Magnetic Resonance spectroscopy, Raman spectroscopy, and high-resolution transmission electron microscopy. Results show that the reduction in micropores (< 2 nm pore diameter) at Ro < 1.55% mainly results from the cleavage of the aliphatic –CH and –CH2, while the increase in micropores at Ro > 1.55% is primarily derived from the condensation of aromatic rings. The development of mesopores (2–50 nm) with increasing maturity could be the result of two different mechanisms: one is developed at the edges of the aromatic layers; another is formation in the space between structural clusters with different orientations. The development of mesopores is related to the compositions and disorder degree of chemical structure. Meanwhile, changes in chemical compositions can affect the surface and structural heterogeneities by altering the surface chemical properties and pore geometry, while variations in spatial arrangement only affect the structural heterogeneity by altering the distribution of void space. Transformation of the chemical structure not only reveals the inherent mechanism of pore heterogeneity in shale kerogens but also provides some microscopic insights for understanding the occurrence and transport behaviors of fluids.

Synthesis of 5(S)-Methyl-L-Proline Containing Peptidomimetic Compounds and their In Vitro Evaluation for Dipeptidyl Peptidase-4 Inhibition

Background: Type 2 diabetes mellitus (T2DM), which is the epidemic of the 21st century, has affected millions of people worldwide. Traditional methods available for the treatment are associated with various side effects. Among the newer therapies, DPP-4 (Dipeptidyl peptidase-4) inhibition has been a promising therapy for the past decade with the scope of further development, especially in peptidomimetics. Objective: 5(S)-methyl-L-proline containing peptidomimetic compounds were designed in the previous work. The designed compounds were synthesized and characterized by spectral methods, such as mass spectrometry, 1H NMR, and 13C NMR (Nuclear magnetic resonance) spectroscopy. The purity of the final compounds was determined by high-performance liquid chromatography (HPLC). The synthesized compounds were in vitro evaluated for their DPP-4 inhibitory activity. Method: Compounds were peptide in nature and were synthesized using the conventional synthesis approach, where peptide synthesis was done using an acid-amine coupling reagent. They were evaluated through fluorimetric enzyme-based assay using a DPP-4 inhibitor screening kit. Moreover, the CLARIOstar microplate reader instrument was used to measure fluorescence. Results: 5(S)-methyl-L-proline containing 13 compounds were synthesized. All of them were characterized for structural integrity using spectral methods. They had HPLC purity of more than 95% and were evaluated for DPP-4 inhibition. Compounds 1, 7, 10, 11, 14 and 17 were found to have good inhibition than others. These compounds were further evaluated at different concentrations to develop a linear correlation coefficient (R2). Conclusion: Six compounds were found to have good DPP-4 inhibition, hence it further opens the possibility of developing DPP-4 inhibitor-containing 5(S)-methyl-L-proline.

Diorganotin(IV) complexes based on tridentate ONO ligands as potential anticancer agents

Eight new diorganotin(IV) complexes (1a-2d), namely {[X-C6H4(O)C=N-N=C(Me)COO]R2Sn(CH3OH)}n (1a, 2a), {[X-C6H4(O)C=N-N=C(Me)COO]R2Sn(CH3OH)}2 (1b, 1c, 1d, 2b), and {[X-C6H4(O)C=N-N=C(Me)COO]R2Sn}2 (2c, 2d) (X = H-, p-Me-, p-OH-, p-NO2-; R = o-Cl-C6H4CH2- or o-Me-C6H4CH2-), have been synthesized by microwave “one-pot” reaction with arylformylhydrazine, pyruvic acid, and the corresponding R2SnCl2. All the complexes have been characterized by FT-IR (Fourier transform infrared spectroscopy), multinuclear NMR (1H, 13C, and 119Sn nuclear magnetic resonance spectroscopies), HRMS (high-resolution mass spectroscopy) and single-crystal X-ray structural analysis. The antiproliferative activity of all complexes was tested against the cancer cell lines NCI-H460, MCF-7 and HepG2. The diorganotin complex 1c has been shown to be more potent antitumor agents against HepG2 than other complexes and cisplatin. Flow cytometry analysis observation demonstrated that complex 1c mediated cell apoptosis of HepG2 cells and arrested cell cycle in the S phase. The single cell gel electrophoreses assay results show that the 1c induce DNA damage. The DNA binding activities of the 1c were studied by UV–visible absorption spectrometry, fluorescence competitive, circular dichroism measurements, and molecular docking, results shown 1c can be well embedded in the groove and cleave DNA.

Chemical Composition of Plant Residues Regulates Soil Organic Carbon Turnover in Typical Soils with Contrasting Textures in Northeast China Plain

Soil organic carbon (SOC) turnover plays a pivotal role in achieving C neutrality, promoting C retention and increasing soil fertility. Residue biochemistry and soil texture essentially determine SOC distribution (including CO2 mineralization and stock in soil) in farmland. However, less is known about allocation of residue-C with contrasting biochemistry and the fate of residue-C in soil under two different textures. This study was conducted in a 61-day aerobic incubation with two Black soils with distinct texture (clay loam vs. sandy loam) in Northeast China. Chemical composition of seven residue parts (soybean roots, leaves, and stems and maize roots, leaves and top and bottom stem parts) was characterized using solid-state 13C nuclear magnetic resonance spectroscopy. The results showed that leaves of both two crops contained significantly higher nitrogen (N), carbonyl and aryl concentrations and lower carbon (C) and lignin concentrations than other parts, resulted in faster decomposition in soils, especially in the clay loam. Stems contained higher O-alkyl and di-O-alkyl concentrations, C/N and lignin/N, while roots contained higher aromaticity. Maize top stem parts with larger slow C pool and longer half-life had higher contribution to SOC accumulation than other parts. Soil textures also induced great impact on SOC turnover. The clay loam favored SOC sequestration due to significantly longer half-life of slow C pool than the sandy loam. Generally, the alkyl/O-alkyl ratio showed the most significant correlation with SOC, CO2 emission and soil biochemical factors in the clay loam; whereas in sandy loam, the lignin/N was the pivotal indicator for SOC accumulation. This study provides insights into the differences in chemical composition among various residue parts, and highlights the significant effects of both residue chemical composition and soil texture on residue decomposition and SOC accumulation.

Preparation and structural characterisation of coal-based fulvic acid based on lignite

Coal-based fulvic acid (FA) is a scarce resource with unique efficacy in many fields such as modern agriculture, ecological restoration and life sciences. However, the efficient and environmentally friendly preparation of FA and its structural characterisation still need to be achieved. In this study, coal-based FA was prepared from Qujing lignite by hydrogen peroxide oxidation under microwave irradiation using CuO as the catalyst. According to the different molecular weights and polar solvent solubility, FA components were separated. Molecular structure models of the components were deduced and constructed through elemental analysis, infrared (IR) spectroscopy and 13C nuclear magnetic resonance (NMR) spectroscopy, combined with quantum chemical calculations and computational analysis. The results showed that each component contains many oxygen-containing functional groups and that carboxyl content > phenolic hydroxyl content > alcohol hydroxyl content > carbonyl content. The chemical formulas of the two components were C44H30O25N (Mr = 972) and C53H35O31N (Mr = 1181). The three-dimensional characteristics of the molecules were determined. The theoretical IR spectra of the models calculated by Gaussian software matched well with the actual spectra, confirming the established models to be reliable. This study provides experimental support and a scientific basis for the efficient preparation and structural characterisation of coal-based FA.

Evolution of pore characteristics and methane adsorption characteristics of Nanshan 1/3 coking coal under different stresses

To ascertain the evolution of pore characteristics and methane adsorption characteristics of the unit cell of Nanshan 1/3 coking coal under different stresses, proximate analysis, ultimate analysis, solid-state 13C nuclear magnetic resonance spectroscopy (13C-NMR) and X-ray photoelectron spectroscopy (XPS) experiments were performed on the coal samples, and a molecular unit cell model of 1/3 coking coal was established. As the increase of stress, pore diameter, proportion of larger pores, number of pores, surface area, and pore volume all decrease, the rate of decrease gradually decreases, and the smaller pores are less affected. Under 8 kinds of stress, the methane adsorption capacity and the overall system energies all conform to the Langmuir adsorption curve; as the stress increases, the methane adsorption capacity and the overall system energies both decrease, the rate of decrease gradually decreases, and the order of the adsorbed methane increases. Stress changes the methane adsorption capacity by changing the pore characteristics of the unit cell, and the stress has a more obvious effect on larger pores. As the stress increases, the speed of the stress's influence on the pores weakens. This has certain guiding significance for studying the saturated adsorption capacity of methane under different original in-situ stresses.

Chlorine-free extraction and structural characterization of cellulose nanofibers from waste husk of millet (Pennisetum glaucum)

This study aims to extract cellulose nanofibers (CNFs) from a sustainable source, i.e. millet husk, which is an agro-waste worthy of consideration. Pre-treatments such as mercerisation, steam explosion, and peroxide bleaching (chlorine-free) were applied for the removal of non-cellulosic components. The bleached millet husk pulp was subjected to acid hydrolysis (5% oxalic acid) followed by homogenization to extract CNFs. The extracted CNFs were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Dynamic Light Scattering (DLS), Energy Dispersive X-ray Spectroscopy (EDX), Thermogravimetry (TG and DTG), Differential scanning calorimetry (DSC), and Solid state 13C nuclear magnetic resonance spectroscopy (solid state 13C NMR). The isolated CNFs show a typical cellulose type-I structure with a diameter of 10-12 nm and a crystallinity index of 58.5%. The appearance of the specific peak at 89.31 ppm in the solid state 13C NMR spectra validates the existence of the type-I cellulose phase in the prepared CNFs. The prepared CNFs had a maximum degradation temperature (Tmax) of 341 °C, that was 31 °C greater than raw millet husk (RMH). The outcome of the study implies that the nanofibers are prominent alternatives for synthetic fibers for assorted potential applications, especially in manufacturing green composites.