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Keywords = CP-MAS NMR

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22 pages, 4578 KiB  
Article
Isolation of Humic Substances Using Waste Wood Ash Extracts: Multiparametric Optimization via Box–Behnken Design and Chemical Characterization of Products
by Dominik Nieweś
Molecules 2025, 30(15), 3067; https://doi.org/10.3390/molecules30153067 - 22 Jul 2025
Viewed by 184
Abstract
This study evaluated birch and oak ash extracts as alternative extractants for isolating humic substances (HSs) from peat and lignite. The effects of ultrasound intensity, extraction time, and temperature were optimized using a Box–Behnken design and validated statistically. The highest HSs yields were [...] Read more.
This study evaluated birch and oak ash extracts as alternative extractants for isolating humic substances (HSs) from peat and lignite. The effects of ultrasound intensity, extraction time, and temperature were optimized using a Box–Behnken design and validated statistically. The highest HSs yields were obtained from peat with oak ash extract (pH 13.18), compared to birch ash extract (pH 12.09). Optimal process parameters varied by variant, falling within 309–391 mW∙cm−2, 116–142 min, and 67–79 °C. HSs extracted under optimal conditions were fractionated into humic acids (HAs) and fulvic acids (FAs), and then analyzed by elemental analysis, Fourier Transform Infrared Spectroscopy (FTIR), and Cross-Polarization Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance Spectroscopy (CP/MAS 13C NMR). The main differences in HSs quality were influenced by raw material and fraction type. However, the use of birch ash extract consistently resulted in a higher proportion of carboxylic structures across all fractions. Overall, wood ash extract, especially from oak, offers a sustainable and effective alternative to conventional extractants, particularly for HSs isolation from lignite. Notably, HSs yield from lignite with oak ash extract (29.13%) was only slightly lower than that achieved with 0.5 M NaOH (31.02%), highlighting its practical potential in environmentally friendly extraction technologies. Full article
(This article belongs to the Section Green Chemistry)
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9 pages, 816 KiB  
Communication
Quantification of Glucosinolates in Seeds by Solid-State 13C-Nuclear Magnetic Resonance (NMR)
by Stefania Mazzini, Marco Zuccolo, Angela Bassoli, Claudio Gardana and Gigliola Borgonovo
Seeds 2025, 4(2), 27; https://doi.org/10.3390/seeds4020027 - 19 Jun 2025
Viewed by 332
Abstract
Solid-state 13C NMR spectroscopy using cross-polarization magic-angle spinning is a highly valuable technique for the semi-quantitative analysis of complex solid matrices. One of its key advantages is that it does not require any manipulation of the matrix, such as extractions or other [...] Read more.
Solid-state 13C NMR spectroscopy using cross-polarization magic-angle spinning is a highly valuable technique for the semi-quantitative analysis of complex solid matrices. One of its key advantages is that it does not require any manipulation of the matrix, such as extractions or other treatments, which is particularly important for preserving the integrity of unstable secondary metabolites. Glucosinolates (β-thioglucoside-N-hydrosulphates) are crucial secondary metabolites specific to Brassica species, and many of them are known to be highly unstable. In this study, we evaluated solid-state nuclear magnetic resonance spectroscopy as an alternative method for the identification and quantification of total glucosinolates in the seeds of Sisymbrium officinale, Brassica napus, Sinapis alba, Brassica nigra, and Moringa oleifera. The results obtained with this method showed good agreement with those from conventional chemical analyses of the seed material. Although, based on a limited number of samples, this preliminary study suggests that the proposed approach could be a useful alternative for quantifying total glucosinolate content in seeds. Full article
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20 pages, 1965 KiB  
Article
Short-Term Effects of Wood Biochar on Soil Fertility, Heterotrophic Respiration and Organic Matter Composition
by Rossella Curcio, Raffaele Bilotti, Carmine Lia, Michele Compitiello, Silvana Cangemi, Mariavittoria Verrillo, Riccardo Spaccini and Pierluigi Mazzei
Agriculture 2025, 15(10), 1091; https://doi.org/10.3390/agriculture15101091 - 19 May 2025
Viewed by 701
Abstract
Biochar may represent a sustainable and eco-friendly strategy to recycle agroforestry wastes, sequester carbon and improve soil health. With the aim of proving these benefits in a real scenario, we treated several soil parcels with 0 (CTRL), 1 (LOW) and 3 (HIGH) kg/m [...] Read more.
Biochar may represent a sustainable and eco-friendly strategy to recycle agroforestry wastes, sequester carbon and improve soil health. With the aim of proving these benefits in a real scenario, we treated several soil parcels with 0 (CTRL), 1 (LOW) and 3 (HIGH) kg/m2 of wood biochar, in open-field trials. The heterotrophic soil respiration (SR) was monitored continuously for two months via a Closed Dynamic Chamber (CDC) associated with an innovative pilot system, and the most important soil chemical parameters were measured 9 and 54 days after biochar application. Biochar induced an immediate dose-dependent increase in organic matter content and CEC (up to 41.6% and 36.8% more than CTRL, respectively), which tended to slightly and gradually decrease after 54 days. In all cases, biochar induced a more pronounced SR, although the most enhanced microbial response was detected for the LOW parcel (19.3% higher than CTRL). Fennels were grown in treated soils and only LOW microplots gave a significantly better response (weight and size). Finally, NMR, FT-IR and Pyr-GC/MS analyses of LOW SOM extracts revealed a relevant impact on the composition, which was accompanied by a higher content of carbohydrates, indole-based compounds and FAME species correlating with enhanced microbial activity. Our findings demonstrate that the proper biochar dose improves soil fertility by creating an environment favorable to plants and promoting microbial activity. Full article
(This article belongs to the Section Agricultural Soils)
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18 pages, 1355 KiB  
Article
The Significance of Herbicide–Humin Interactions in Sustainable Agroecosystems
by Maria Jerzykiewicz, Irmina Ćwieląg-Piasecka, Jerzy Weber, Aleksandra Ukalska-Jaruga, Elżbieta Jamroz, Andrzej Kocowicz, Magdalena Debicka, Jakub Bekier, Lilla Mielnik, Romualda Bejger, Magdalena Banach-Szott and Agnieszka Grabusiewicz
Sustainability 2025, 17(8), 3449; https://doi.org/10.3390/su17083449 - 12 Apr 2025
Viewed by 400
Abstract
Humin, as the most stable fraction in soil organic matter, determines possibility of sustainable environmental development by influencing, among other things, the binding and migration of different chemicals in soil. The aim of this paper was to determine changes in the properties of [...] Read more.
Humin, as the most stable fraction in soil organic matter, determines possibility of sustainable environmental development by influencing, among other things, the binding and migration of different chemicals in soil. The aim of this paper was to determine changes in the properties of humins after interaction with three selected active substances of herbicides differing in structure and chemical properties (pendimethalin, metazachlor, and flufenacet) and two different commercial products. In accordance with OECD 106 guidelines, humins isolated from eight different soils were saturated with herbicide compounds under study. As humin is a non-hydrolyzable organic carbon fraction, solid state research techniques (elemental analysis, NMR, FTIR, EPR, and UV-Vis) were applied. The results clearly showed that the interaction between humin and herbicides increases the concentration of oxygen-containing groups and the internal oxidation (ω) in humin. For all investigated humins, a reduction in radical concentration was observed. Radicals in humins were not completely quenched; a certain concentration of radicals with unchanged structure always remained in the samples. Other spectroscopic analyses showed no significant changes in the structure of pesticide-saturated and non-saturated humins. This suggests that sorption of the studied compounds occurs on the humins only as a result of the interaction of physical forces on the surface of the studied organic matter fraction. Thus, interaction with the studied herbicides occurs as a surface phenomenon, and the inner core remains protected by the condensed structure and/or strong binding to the clay minerals. Full article
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14 pages, 3642 KiB  
Article
Structure of Cellulose Isolated from Rapeseed Stalks
by Bogdan-Marian Tofanica, Emanuela Callone, Elena Ungureanu, Ovidiu C. Ungureanu and Valentin I. Popa
Polymers 2025, 17(8), 1032; https://doi.org/10.3390/polym17081032 - 11 Apr 2025
Cited by 1 | Viewed by 503
Abstract
Solid state Cross-Polarization/Magic-Angle-Spinning 13C CP/MAS Nuclear Magnetic Resonance (NMR) spectra were obtained for cellulose and α-cellulose isolated from rapeseed stalks. This study provides the first characterization of the rapeseed stalk cellulose, revealing that native cellulose occurs as cellulose I allomorph, while α-cellulose [...] Read more.
Solid state Cross-Polarization/Magic-Angle-Spinning 13C CP/MAS Nuclear Magnetic Resonance (NMR) spectra were obtained for cellulose and α-cellulose isolated from rapeseed stalks. This study provides the first characterization of the rapeseed stalk cellulose, revealing that native cellulose occurs as cellulose I allomorph, while α-cellulose exhibits distinct crystalline structures similar to those found in cellulose II. Additionally, Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), and Energy-Dispersive X-ray Microanalysis (EDX) were employed to further investigate and unveil the structural properties of cellulose extracted from rapeseed stalks. These complementary techniques offered a more comprehensive understanding of the cellulose morphology, crystallinity, and chemical composition, providing valuable insights into the potential utilization of rapeseed stalks as a renewable biomass resource for various industrial applications. Full article
(This article belongs to the Special Issue New Advances in Cellulose and Wood Fibers)
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17 pages, 6383 KiB  
Article
Optimization of the Heterogeneous Synthesis Conditions for Cellulose Tosylation and Synthesis of a Propargylamine Cellulosic Derivative
by Marcos V. Ferreira, Poliana Ricci, Henrique A. Sobreira, Anizio M. Faria, Rodrigo B. Panatieri, Brent S. Sumerlin and Rosana M. N. Assunção
Polymers 2025, 17(1), 58; https://doi.org/10.3390/polym17010058 - 29 Dec 2024
Viewed by 1545
Abstract
Cellulose tosylate (MCC-Tos) is a key derivative for surface modification and a crucial precursor for cellulose compatibilization in click reactions, enabling its functionalization for advanced applications. Replacing tosyl groups with alkyne groups broadens cellulose’s potential in biocompatible reactions, such as thiol-yne click chemistry [...] Read more.
Cellulose tosylate (MCC-Tos) is a key derivative for surface modification and a crucial precursor for cellulose compatibilization in click reactions, enabling its functionalization for advanced applications. Replacing tosyl groups with alkyne groups broadens cellulose’s potential in biocompatible reactions, such as thiol-yne click chemistry and protein/enzyme immobilization. To achieve this, we optimized the heterogeneous synthesis of MCC-Tos using a Doehlert matrix statistical design, evaluating the influence and interaction of the reaction conditions. The optimized conditions—144 h reaction time, 10:1 molar ratio, and 30 °C—yielded a degree of substitution for tosyl groups (DStos) of 1.80, determined via elemental analysis and FTIR-ATR spectroscopy. The reaction kinetics followed a first-order model. A subsequent reaction with propargylamine produced aminopropargyl cellulose (MCC-PNH), reducing DStos by 65%, which was confirmed via FTIR, and improving thermal stability by a margin of 30 °C (TGA/DTG). 13C CP/MAS NMR confirmed the alkyne group attachment, further validated via coupling an azide-functionalized coumarin through copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC). Fluorescence microscopy and UV spectroscopy were used to estimate a substitution degree of 0.21. This study establishes a feasible route for synthesizing alkyne-functionalized cellulose, paving the way for eco-friendly materials, including protein/enzyme bioconjugates, composites, and advanced materials via thiol-yne and CuAAC reactions. Full article
(This article belongs to the Section Polymer Chemistry)
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12 pages, 1359 KiB  
Article
Changes in Soil Humin Macromolecular Structure Resulting from Long-Term Catch Cropping
by Jerzy Weber, Elżbieta Jamroz, Lilla Mielnik, Riccardo Spaccini, Andrzej Kocowicz, Irmina Ćwieląg-Piasecka, Maria Jerzykiewicz, Danuta Parylak and Magdalena Dębicka
Molecules 2024, 29(21), 5049; https://doi.org/10.3390/molecules29215049 - 25 Oct 2024
Cited by 1 | Viewed by 1035
Abstract
The aim of this study was to assess the effect of long-term catch crop application on the structural properties of humin, which is considered the most recalcitrant fraction of soil organic matter. Soil samples from a 30-year field experiment on triticale cultivated with [...] Read more.
The aim of this study was to assess the effect of long-term catch crop application on the structural properties of humin, which is considered the most recalcitrant fraction of soil organic matter. Soil samples from a 30-year field experiment on triticale cultivated with and without catch crops were analysed to determine the total organic carbon content and fractional composition of humic substances. Meanwhile, humin isolated from bulk soil was analysed to determine its elemental composition and spectroscopic properties measured with UV-Vis, fluorescence, and 13C-CPMAS-NMR. It was found that catch crop farming enhanced the formation of highly reactive humus substances, like low-molecular-weight fractions and humic acids, while decreasing the humin fraction. The higher H/C and O/C atomic ratios of humin and the UV-Vis, fluorescence, and 13C-CPMAS-NMR results confirmed a higher share of oxygen-containing functional groups in humin isolated from the soil with catch crop rotation, also corroborating its greater aliphatic nature. Under the conditions of our field experiment, the results indicated that organic residues from catch crops quickly undergo the decay process and are transformed mainly into highly reactive humus substances, which can potentially improve soil health, while mineral fertilisation alone without catch crops favours the stabilisation and sequestration of carbon. Full article
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17 pages, 5989 KiB  
Article
Study on Quality and Starch Characteristics of Powdery and Crispy Lotus Roots
by Zichen Cai, Yaying Jiang, Fei Wang, Jun Liu, Juan Kan, Man Zhang, Xiaohua Qi, Liangjun Li, Shuping Zhao and Chunlu Qian
Foods 2024, 13(20), 3335; https://doi.org/10.3390/foods13203335 - 21 Oct 2024
Cited by 4 | Viewed by 1988
Abstract
Nine varieties of lotus root (Suining, Xinhe, Zaohua, Zhonghua, L0014, L0013, Cuiyu, L0011, and Zhenzhu) were selected as the research materials to compare their differences in physical, chemical, and starch characteristics before and [...] Read more.
Nine varieties of lotus root (Suining, Xinhe, Zaohua, Zhonghua, L0014, L0013, Cuiyu, L0011, and Zhenzhu) were selected as the research materials to compare their differences in physical, chemical, and starch characteristics before and after boiling, frying, and microwaving. The results showed that Zhenzhu, Xinhe, L0013, Cuiyu, and Zhonghua belong to the crispy lotus root type, while L0011, L0014, Zaohua, and Suining belong to the powdery lotus root type. Furthermore, the nine varieties were characterized for their starch by optical micrograph (OM), polarized micrograph (PM), scanning electron micrograph (SEM), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), carbon-13 cross-polarization/magic angle spinning nuclear magnetic resonance (13C CP/MAS NMR), and differential scanning calorimetry (DSC). The starch granule of powdery lotus root appeared to be larger than that of crispy lotus, and ATR-FTIR studies revealed that the outer layer of starch granules from nine different varieties of lotus root had a highly organized structure. Moreover, XRD and 13C CP/MAS NMR analyses revealed that starch from eight lotus varieties (Suining, Xinhe, Zaohua, Zhonghua, L0014, L0013, Cuiyu, L0011) belong to the A-crystal type, while starch from Zhenzhu belongs to the CA-crystal type. The starch from powdery lotus root exhibited higher crystallinity, as well as increased gelatinization temperature and enthalpy, indicating that its crystal structure was relatively superior compared to that of crispy lotus starch. The short-range order degree, crystallinity, gelatinization temperature, and heat enthalpy of lotus starch decreased after boiling and frying but increased to varying extents after microwaving. Additionally, the heat resistance and stability of starch particles from crispy lotus root were improved after microwave treatment. Full article
(This article belongs to the Section Food Quality and Safety)
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23 pages, 10596 KiB  
Article
Advanced Nuclear Magnetic Resonance, Fourier Transform–Infrared, Visible-NearInfrared and X-ray Diffraction Methods Used for Characterization of Organo-Mineral Fertilizers Based on Biosolids
by Ramona Crainic, Elena Mihaela Nagy, Gabriel Fodorean, Mihai Vasilescu, Petru Pascuta, Florin Popa and Radu Fechete
Agriculture 2024, 14(10), 1826; https://doi.org/10.3390/agriculture14101826 - 16 Oct 2024
Cited by 1 | Viewed by 1674
Abstract
Biosolids from stabilized sludge present a high fertilization potential, due to their rich content of nutrients and organic matter. The intrinsic and subtle properties of such fertilizers may greatly influence the fertilization efficiency. In this sense, the utility, advantages and limitations of advanced [...] Read more.
Biosolids from stabilized sludge present a high fertilization potential, due to their rich content of nutrients and organic matter. The intrinsic and subtle properties of such fertilizers may greatly influence the fertilization efficiency. In this sense, the utility, advantages and limitations of advanced characterization methods, for the investigation of structural and dynamic properties at the microscopic scale of slightly different formulations of fertilizers were assessed. For that, three formulas of organo-mineral fertilizers based on biosolids (V1, V2 and V3), having at least 2% N, 2% P2O5, and 2% K2O, were characterized by advanced methods, such as 1H NMR relaxometry, 1H MAS and 13C CP-MAS NMR spectroscopy, 1H double-quantum NMR and FT-IR spectroscopy. Advanced structural characterization was performed using SEM, EDX and X-ray diffraction. Four dynamical components were identified in the NMR T2 distribution showing that the rigid component has a percentage larger than 90%, which explains the broad band of NMR spectra confirmed by the distributions of many components in residual dipolar coupling as were revealed by 1H DQ-NMR measurements. SEM and EDX measurements helped the identification of components from crystalline-like X-ray diffraction patterns. To evaluate the release properties of organo-mineral fertilizers, dynamic measurements of classical electric conductivity and pH were performed by placing 0.25 g of the formulas (V1, V2 and V3) in 200 mL of distilled water. The content of N and P were quantified using specific reactants, combined with VIS-nearIR spectroscopy. Two release mechanisms were observed and characterized. It was found that V3 presents the smallest release velocity but releases the largest number of fertilizers. Full article
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12 pages, 1494 KiB  
Article
Chitin Extracted from Black Soldier Fly Larvae at Different Growth Stages
by Andrea Marangon, Geo Paul, Riccardo Zaghi, Leonardo Marchese and Giorgio Gatti
Polymers 2024, 16(20), 2861; https://doi.org/10.3390/polym16202861 - 10 Oct 2024
Cited by 4 | Viewed by 2402
Abstract
The black soldier fly (BSF) Hermetia Illucens can grow rapidly and on a wide variety of organic materials, and it is extensively used as a means of disposing of household organic waste. Different phases of the life cycle of BSF larvae (BSFL) are [...] Read more.
The black soldier fly (BSF) Hermetia Illucens can grow rapidly and on a wide variety of organic materials, and it is extensively used as a means of disposing of household organic waste. Different phases of the life cycle of BSF larvae (BSFL) are used in this work to extract chitin after the removal of lipids, mineral salts, and proteins. Multiple techniques, such as X-ray diffractometry, infrared spectroscopy, solid-state Nuclear Magnetic Resonance (13C ss-NMR) and thermogravimetric analysis, are used to investigate the chemical and physical characteristics of the extracted samples of chitin, which shows a high degree of acetylation (from 78% to 94%). The extracted chitin shows an increase of the thermal stability of 20 °C in the initial stage of life and 35 °C at the end of the life cycle if compared with a commercial standard. Moreover, the extracted chitin shows an increase in the crystallinity degree during the BSFL growth time (from 72% to 78%). Full article
(This article belongs to the Special Issue Natural Polysaccharides: Chitosan, Chitin, Pectin and Gums)
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18 pages, 6838 KiB  
Article
Trialkoxysilane Grafting in Alcohols: A Simple Approach towards Modified Silica-Based Materials
by Paola Marzullo, Vincenzo Campisciano, Leonarda Francesca Liotta, Francesca D’Anna, Francesco Giacalone and Michelangelo Gruttadauria
Molecules 2024, 29(19), 4730; https://doi.org/10.3390/molecules29194730 - 7 Oct 2024
Cited by 1 | Viewed by 1333
Abstract
The grafting of trialkoxysilanes is the most common method for the surface functionalization of silica gel, and it is usually carried out in the presence of toluene or other solvents such as acetonitrile or acetone. Here, we replaced these solvents with alcohols to [...] Read more.
The grafting of trialkoxysilanes is the most common method for the surface functionalization of silica gel, and it is usually carried out in the presence of toluene or other solvents such as acetonitrile or acetone. Here, we replaced these solvents with alcohols to afford silica materials containing alkoxy groups linked to the silicon atom. The grafting of N,N-dimethyl-3-amino- or 3-amino-propyltrimethoxysilane was carried out in the presence of several alcohols containing an unsubstituted alkyl chain (C7 and C14), a PEG functionalized chain, or an amino-substituted chain (N,N-dimethylamino, pyridyl). Materials were characterized via solid-state 13C- and 29Si CPMAS NMR and thermogravimetric analysis to prove that alcohols are not “innocent” solvents but take part in the reaction and lead to [RSi(OR1)-(OSi)2] systems where the OR1 group proceeds from the alcohol used in the synthesis. As a proof of concept, we briefly studied the catalytic activity of some of these materials with the aim of showing how different modifications can influence the course of a selected reaction. Finally, a quaternary ammonium salt (QAS)-based silica was prepared containing both an alkyl-QAS and an alkoxy-QAS linked to silicon atoms. This could represent an interesting approach for the development of new antifouling-based materials and, overall, the described strategy could be useful for the preparation of new organosilica materials. Full article
(This article belongs to the Section Materials Chemistry)
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11 pages, 1874 KiB  
Article
Chemical Bonds Formed in Solid Wood by Reaction with Maleic Anhydride and Sodium Hypophosphite
by Injeong Kim, Oleg N. Antzutkin, Faiz Ullah Shah, Olov Karlsson, Dennis Jones and Dick Sandberg
Materials 2024, 17(19), 4856; https://doi.org/10.3390/ma17194856 - 2 Oct 2024
Cited by 1 | Viewed by 1280
Abstract
The reaction of wood with maleic anhydride (MA) and sodium hypophosphite (SHP) has been identified as a viable modification method, with macroscopical properties indicating formation of cross-linking to explain the results. However, the chemical reaction between wood and the modification reagents has not [...] Read more.
The reaction of wood with maleic anhydride (MA) and sodium hypophosphite (SHP) has been identified as a viable modification method, with macroscopical properties indicating formation of cross-linking to explain the results. However, the chemical reaction between wood and the modification reagents has not been studied yet. To resolve this, the reaction was studied with solid-state 13C cross-polarization magic-angle-spinning (CP-MAS) and 31P MAS nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) to reveal the formation of bonds between wood components, MA and SHP during the treatments to explain the formation of cross-linking and the possible fixation of phosphorus in wood. XPS, solid state 13C and 31P MAS NMR revealed the maleation of wood in the absence of SHP, whilst its presence led to forming a succinic adduct observed through the C-P bond formation, as evidenced by the loss of the maleate C=C bonds at around 130 ppm and the upfield shift of the peak at 165–175 ppm, which was also significantly smoothed, as well as the increase in a peak at 26 ppm due to the reaction between the maleate group and SHP; however, the C-P-C bond could not be unambiguously rationalized from the obtained data. On the other hand, a resonance line at 16 ppm in 31P MAS NMR and the peaks in the XPS P 2p spectrum suggested the formation of a cross-linked structure at low concentrations of SHP, which was more likely to be phosphonate (C-P-O) than organophosphinic acid (C-P-C). The results herein provide a greater fundamental understanding of the mechanisms involved in the reaction of wood, MA and SHP, providing further scope for improved treatment systems in the future. Full article
(This article belongs to the Section Green Materials)
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24 pages, 9702 KiB  
Article
Crystal Structure, Supramolecular Organization, Hirshfeld Analysis, Interaction Energy, and Spectroscopy of Two Tris(4-aminophenyl)amine-Based Derivatives
by Mayra M. Luna-Martínez, Marcos Morales-Santana, José Martín Santiago-Quintana, Efrén V. García-Báez, Jayanthi Narayanan, María de Jesús Rosales-Hoz and Itzia I. Padilla-Martínez
Crystals 2024, 14(10), 855; https://doi.org/10.3390/cryst14100855 - 29 Sep 2024
Viewed by 1882
Abstract
The use of tris(4-aminophenyl)amine (TAPA) as central to the synthesis of both polyimines and polyimides and covalent organic frameworks and inorganic cages, among others, has grown in the last few years. The resulting materials exhibit high performance in their area of application. In [...] Read more.
The use of tris(4-aminophenyl)amine (TAPA) as central to the synthesis of both polyimines and polyimides and covalent organic frameworks and inorganic cages, among others, has grown in the last few years. The resulting materials exhibit high performance in their area of application. In this contribution, the crystal structures of two TAPA derivatives, triethyl (nitrilotris(benzene-4,1-diyl))tricarbamate (1) and triethyl 2,2′,2″-((nitrilotris(benzene-4,1-diyl))tris(azanediyl))tris(2-oxoacetate) (2), are described. The molecular and supramolecular structures of both compounds were compared between them and with analogous compounds. The analyses of their vibrational and 13C-CPMAS NMR spectroscopies, as well as their thermal stability, were included and corelated with the crystal structure. Hirshfeld surface analysis on the crystal structures of both TAPA derivatives revealed the stabilization of the crystal network via the amide N—H∙∙∙O interactions of dispersive nature in the carbamate, whereas dispersive carbonyl–carbonyl interactions also played a competitive role in the supramolecular arrangement of the oxamate. Interaction energy DFT calculations performed at the B3LYP/6-31G(d,p) level allowed us to estimate the energy contributions and nature of several interactions in terms of the stability of both crystal lattices. Full article
(This article belongs to the Section Macromolecular Crystals)
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20 pages, 5663 KiB  
Article
Cross-Linked Metathesis Polynorbornenes Based on Nadimides Bearing Hydrocarbon Substituents: Synthesis and Physicochemical Properties
by Kirill S. Sadovnikov, Ivan V. Nazarov, Vsevolod A. Zhigarev, Anastasia A. Danshina, Igor S. Makarov and Maxim V. Bermeshev
Polymers 2024, 16(18), 2671; https://doi.org/10.3390/polym16182671 - 22 Sep 2024
Cited by 2 | Viewed by 1468
Abstract
Metathesis homo- and copolymerization of bifunctional monomers bearing two norbornene moieties was studied. The monomers were synthesized from cis-5-norbornene-exo-2,3-dicarboxylic anhydride and various diamines (hexamethylenediamine, decamethylenediamine, 1R,3S-isophoronediamine). The metathesis homopolymerization of these bis(nadimides) in the presence of the second-generation Grubbs catalyst afforded glassy cross-linked [...] Read more.
Metathesis homo- and copolymerization of bifunctional monomers bearing two norbornene moieties was studied. The monomers were synthesized from cis-5-norbornene-exo-2,3-dicarboxylic anhydride and various diamines (hexamethylenediamine, decamethylenediamine, 1R,3S-isophoronediamine). The metathesis homopolymerization of these bis(nadimides) in the presence of the second-generation Grubbs catalyst afforded glassy cross-linked polymers in more than 90% yields. The metathesis copolymerization of the bis(nadimides) and a monofunctional norbornene derivative containing the β-pinene fragment also resulted in insoluble cross-linked polymers in nearly quantitative yields. The structures and purity of the synthesized polymers were confirmed via IR spectroscopy and CP/MAS NMR spectroscopy. Conditions for the fabrication of mechanically strong solution-cast thin films based on copolymers synthesized from the comonomers mentioned above were determined by varying the content of the cross-linking agent. It was shown that the films made in this way are stable in a range of organic solvents and could be useful as semipermeable or membrane materials for use in liquid organic media. The permeability of the polymer films in question to 1-phenylethanol and mandelic acid was studied. The results obtained are discussed along with the data from the DSC, TGA, and powder X-ray diffraction studies of the properties of the synthesized metathesis homo- and copolymers. Full article
(This article belongs to the Special Issue Preparation and Application of Functional Polymer Materials)
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20 pages, 2623 KiB  
Article
A Highly Sensitive Chitosan-Based SERS Sensor for the Trace Detection of a Model Cationic Dye
by Bahareh Vafakish and Lee D. Wilson
Int. J. Mol. Sci. 2024, 25(17), 9327; https://doi.org/10.3390/ijms25179327 - 28 Aug 2024
Cited by 3 | Viewed by 1414
Abstract
The rapid detection of contaminants in water resources is vital for safeguarding the environment, where the use of eco-friendly materials for water monitoring technologies has become increasingly prioritized. In this context, the role of biocomposites in the development of a SERS sensor is [...] Read more.
The rapid detection of contaminants in water resources is vital for safeguarding the environment, where the use of eco-friendly materials for water monitoring technologies has become increasingly prioritized. In this context, the role of biocomposites in the development of a SERS sensor is reported in this study. Grafted chitosan was employed as a matrix support for Ag nanoparticles (NPs) for the surface-enhanced Raman spectroscopy (SERS). Chitosan (CS) was decorated with thiol and carboxylic acid groups by incorporating S-acetyl mercaptosuccinic anhydride (SAMSA) to yield CS-SAMSA. Then, Ag NPs were immobilized onto the CS-SAMSA (Ag@CS-SAMSA) and characterized by spectral methods (IR, Raman, NIR, solid state 13C NMR with CP-MAS, XPS, and TEM). Ag@CS-SAMSA was evaluated as a substrate for SERS, where methylene blue (MB) was used as a model dye adsorbate. The Ag@CS-SAMSA sensor demonstrated a high sensitivity (with an enhancement factor ca. 108) and reusability over three cycles, with acceptable reproducibility and storage stability. The Raman imaging revealed a large SERS effect, whereas the MB detection varied from 1–100 μM. The limits of detection (LOD) and quantitation (LOQ) of the biocomposite sensor were characterized, revealing properties that rival current state-of-the-art systems. The dye adsorption profiles were studied via SERS by fitting the isotherm results with the Hill model to yield the ΔG°ads for the adsorption process. This research demonstrates a sustainable dual-function biocomposite with tailored adsorption and sensing properties suitable for potential utility in advanced water treatment technology and environmental monitoring applications. Full article
(This article belongs to the Section Materials Science)
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