Lignin Moieties Research Articles

Catalytic pyrolysis mechanism of lignin moieties driven by aldehyde, hydroxyl, methoxy, and allyl functionalization: the role of reactive quinone methide and ketene intermediates.

The catalytic pyrolysis of guaiacol-based lignin monomers, vanillin, syringol, and eugenol over commercial HZSM-5 has been investigated using operando Photoelectron Photoion Coincidence (PEPICO) spectroscopy to unveil the reaction mechanism by detecting reactive intermediates, such as quinone methides and ketenes, and products. Vanillin shares the decomposition mechanism with guaiacol due to prompt and efficient decarbonylation, which allows us to control this reaction leading to a phenol selectivity increase by switching to a faujasite catalyst and decreasing the Si/Al ratio. Syringol first demethylates to 3-methoxycatechol, which mainly dehydroxylates to o- and m-guaiacol. Ketene formation channels over HZSM-5 are less important here than for guaiacol or vanillin, but product distributionremains similar. C3 addition to guaiacol yields eugenol, which shows a more complex product distribution upon catalytic pyrolysis. By analogies to monomers with simplified functionalization, namely allylbenzene, 4-allylcatechol, and 4-methylcatechol, the eugenol chemistry could be fully resolved. Previously postulated reactive semi-quinone intermediates are detected spectroscopically, and their involvement opens alternative pathways to condensation and phenol formation. Allyl groups, produced by dehydroxylation of the β-O-4 bond, may not only decompose via C1/C2/C3 loss, but also cyclize to indene and its derivatives over HZSM-5. This comparably high reactivity leads to an unselective branching of the chemistry and to a complex product distribution, which is difficult to control. Indenes and naphthalenes are also prototypical coke precursors efficiently deactivating the catalyst. We rely on these mechanistic insights to discuss strategies to fine-tune process conditions to increase the selectivities of desired products by enhancing either vanillin and guaiacol or supressing eugenol yields from native lignin.

A Computational Study of Reactions with Boric Acid Aimed to Promote the Utilization of Lignin.

For exploring the reaction between the hydroxyl groups of lignin and boric acid under the alkaline condition, we study three proposed mechanisms for the formation of the anionic borate diester (ABDE) using the salicyl alcohol anion as the model compound by the density functional theory. ABDE has high flame retardancy and is a potentially practical application of lignin. The catalysis of sodium cation is found to enhance the deprotonation of the water cluster. The deprotonated product, hydroxide anion, is essential to the critical step, which is the cleavage of B-O bonds of the boric acid molecule, in reaction mechanisms. The energy profiles of the mechanisms show that the reaction between lignin and boric acid may start from the hydroxymethyl moieties of lignin since it requires less energy for the aforementioned critical step than from the phenol moieties of lignin. Moreover, the hydroxide anions compete with the hydroxymethyl groups in lignin for the formation of B-O bonds by forming tetrahydroxyborate anion (TBA) which requires very high activation energies to further react to the desired product ABDE. The optimal condition is to enhance the catalytic effect of sodium cations and meanwhile to control the formation of TBA.

The two-faced functionality of birch glucuronoxylan in an emulsion-based carrier of vitamin D3

Emulsions are commonly used to fortify beverages with oil-soluble nutrients. Such emulsions must be physically stable, prevent the cargo nutrient from chemical degradation, and release the nutrient at the right time during digestion. Wood hemicelluloses, with their proven capability in producing nanoemulsions and preventing oil oxidation, have the potential to facilitate such a fortification method. These hemicelluloses are unique, as the presence of residual lignin was proven essential in their functionality. However, the structural interplay between the residual lignin and the polysaccharide fraction at the oil-water interface is unknown, including their effects on the storage stability and digestibility of a loaded bioactive compound. We studied the performance of emulsions stabilized by two grades of birch glucuronoxylans (GX) as vessels for vitamin D3. Both GXs showed similar protective performance to methylcellulose regardless of the lignin content during storage and the gastric phase of digestion. The unrefined GX, which contained larger lignin moieties, delayed the release of vitamin D3 during intestinal digestion. We concluded that the interface is primarily built of a polysaccharide layer with the lignin moieties facing towards the oil phase. We have thus highlighted the potential of GX-stabilized emulsions as carriers of vitamin D3. Additionally, these results advance the understanding of lignin-polysaccharide interplay towards a rationalized strategy in biorefining of wood hemicelluloses, for which the ratio of lignin-to-polysaccharide can be adjusted during extraction and post-extraction treatments to obtain a tailor-made emulsifier for various emulsion-based products.

Impact of future scenarios of climate change on lignin dynamics in soil: A case study in a Mediterranean savannah

Lignin is an abundant and recalcitrant biopolymer of major relevance as soil organic matter (SOM) component playing a significant role in its stabilization. In this work, a factorial field experiment was established, where three climatic treatments (W, warming; D, drought; W + D, warming + drought), mimicking future climate change scenarios were installed over five years in a Mediterranean savannah “dehesa”, accounting for its landscape diversity (under the tree canopy and in open grassland). A combination of analytical pyrolysis (Py-GC/MS) and the study of biogeochemical proxies based on lignin monomers is used for the direct detection of lignin-derived phenols and to infer possible shifts in lignin dynamics in soil. A total of 27 main lignin-derived methoxyphenols were identified, exhibiting different patterns and proportions, mainly driven by the effect of habitat, hence biomass inputs to SOM. An accelerated decomposition of lignin moieties –(exhibited by higher LG/LS and Al/K + Ac ratios)– is particularly exacerbated by the effect of all climatic treatments. There is also an overall effect on increasing lignin oxidation of side chain in syringyl units, especially under the tree canopy due to the alteration in biomass degradation and potential stimulation of enzyme activities. Conversely, in open grassland these effects are slower since the microbial community is expected to be already adapted to harsher conditions. Our findings suggests that climate change-related temperature and soil moisture deviations impact soil lignin decomposition in dehesas threatening this productive Mediterranean agroecosystem and affecting the mechanism of soil carbon storage.

Comparison of Oil-Seed Shell Biomass-Based Biochar for the Removal of Anionic Dyes-Characterization and Adsorption Efficiency Studies.

This research investigated the synthesis of biochar through the direct pyrolysis of pre-roasted sunflower seed shells (SFS) and peanut shells (PNS) and compared their application for the effective removal of textile dyes from wastewater. Biochar prepared at 900 °C (SFS900 and PNS900) showed the highest adsorption capacity, which can be attributed to the presence of higher nitrogen content and graphite-like structures. CHNS analysis revealed that PNS900 exhibited an 11.4% higher carbon content than SFS900, which enhanced the environmental stability of PNS biochar. Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses of the produced biochar indicated the degradation of cellulosic and lignin moieties. X-ray photoelectron spectroscopy (XPS) revealed a 13.8% and 22.6% increase in C-C/C=C mass concentrations in the SFS900 and PNS900, respectively, and could be attributed to the condensation of polyaromatic structures. Batch experiments for dye removal demonstrated that irrespective of dye species, PNS900 exhibited superior dye removal efficiency compared to SFS900 at similar dosages. In addition to H-bonding and electrostatic interactions, the presence of pyridinic-N and graphitic-N can play a vital role in enhancing Lewis acid-base and π-π EDA interactions. The results can provide valuable insights into the biochar-dye interaction mechanisms.

Soft X-rays radiation damage on plunge-frozen and freeze-dried maize roots evaluated by FTIR spectromicroscopy

The radiation damage issue consequent to soft X-rays’ exposure is still an important aspect to be contemplated in soft X-ray microscopy. The work presented here is part of a more extended investigation on the topic and targets the effects of soft X-rays exposure on plant tissues.The aftermaths of soft X-rays’ exposure were evaluated by FTIR spectromicroscopy by comparing irradiated and non-irradiated areas on similar plant structural features, one day and ten days after irradiation, to highlight also a possible time-dependent behavior consequent to air exposure.Our results show partial degradation of lignocellulosic complex and oxidation of cellulose and most probably of hemicellulose; lignin moiety of cell walls in vascular tissue however remains stable.Comparing the current study with our previous works it appears that, as expected, plant tissues seem less prone to soft X-rays radiation damage compared to mammalian cells or tissues.

Advanced NMR Characterization of Aquasolv Omni (AqSO) Biorefinery Lignins/Lignin-Carbohydrate Complexes.

Our recently reported AquaSolv Omni (AqSO) process shows great potential as a parameter-controlled type of biorefinery, which allows tuning of structure and properties of the products towards their optimal use in high-value applications. Herein, a comprehensive NMR (quantitative 13 C, 31 P, and 2D heteronuclear single-quantum coherence) structural characterization of AqSO lignins is reported. The effect of the process severity (P-factor) and liquid-to-solid ratio (L/S) on the structure of the extracted lignins has been investigated and discussed. Low severity (P-factor in the range 400-600) and L/S=1 led to the isolation of less degraded lignin with a higher β-O-4 content up to 34/100 Ar. Harsher processing conditions (P-factor=1000-2500) yielded more condensed lignins with a high degree of condensation up to 66 at P-factor=2000. New types of lignin moieties, such as alkyl-aryl and alkyl-alkyl chemical bonds together with novel furan oxygenated structures have been identified and quantified for the first time. In addition, the formation of lignin carbohydrate complexes bonds has been hypothesized at low severity and L/S. Based on the obtained data we were able to formulate a possible outlook of the occurring reactions during the hydrothermal treatment. Overall, such detailed structural information bridges the gap from process engineering to sustainable product development.

Unraveling the Lignin Structural Variation in Different Bamboo Species.

The structure of cellulolytic enzyme lignin (CEL) prepared from three bamboo species (Neosinocalamus affinis, Bambusa lapidea, and Dendrocalamus brandisii) has been characterized by different analytical methods. The chemical composition analysis revealed a higher lignin content, up to 32.6% of B. lapidea as compared to that of N. affinis (20.7%) and D. brandisii (23.8%). The results indicated that bamboo lignin was a p-hydroxyphenyl-guaiacyl-syringyl (H-G-S) lignin associated with p-coumarates and ferulates. Advanced NMR analyses displayed that the isolated CELs were extensively acylated at the γ-carbon of the lignin side chain (with either acetate and/or p-coumarate groups). Moreover, a predominance of S over G lignin moieties was found in CELs of N. affinis and B. lapidea, with the lowest S/G ratio observed in D. brandisii lignin. Catalytic hydrogenolysis of lignin demonstrated that 4-propyl-substituted syringol/guaiacol and propanol guaiacol/syringol derived from β-O-4' moieties, and methyl coumarate/ferulate derived from hydroxycinnamic units were identified as the six major monomeric products. We anticipate that the insights of this work could shed light on the sufficient understanding of lignin, which could open a new avenue to facilitate the efficient utilization of bamboo.

Effect of chemically modified lignin addition on the physicochemical properties of PCL nanofibers

In this study, a chemically modified lignin additive was successfully prepared to improve the physicochemical properties of biodegradable polycaprolactone (PCL)-based nanofibers. The molecular weight and surface functional group characteristics of lignin were effectively controlled through a solvent fractionation process using ethanol. Then, PCL-g-lignin was successfully synthesized by using ethanol-fractionated lignin as a platform for the PCL grafting process. Finally, PCL/PCL-g-lignin composite nanofibers were simply prepared by adding PCL-g-lignin to the PCL doping solution and performing a solution blow spinning process. The addition of PCL-g-lignin could dramatically improve the physical and chemical properties of PCL nanofibers, and in particular, the tensile strength (0.28 MPa) increased by approximately 280 % compared to the conventional PCL. In addition, the lignin moiety present in PCL-g-lignin was able to impart UV blocking properties to PCL nanofibers, and as a result, it was possible to effectively suppress the photolysis phenomenon that occurred rapidly in existing PCL nanofibers. Therefore, PCL-g-lignin may be widely used not only as a reinforcing agent of existing biodegradable nanofibers but also as a functional additive for UV protection.

Rational design of pyrrolic-N dominated carbon material derived from aminated lignin for Zn-ion supercapacitors

Developing highly efficient, sustainable carbon cathodes is essential for emerging Zn-ion hybrid supercapacitors (ZICs). Herein, lignin's novel chemical modification (amination) has been developed to produce high quantity pyrrolic-N moieties as active sites. Furthermore, chemically modified amine moieties in lignin are vital as a natural self-activating template to generate hierarchical porosity in the 2D (graphene-like) architecture with exceedingly high surface area (2926.4 m2g−1). The rationally introduced dominated pyrrolic-N moieties boost the Zn-ion storage capacity and reaction kinetics due to the dual energy storage mechanism and efficient charge transfer between pyrrolic-N and Zn+2 ions. Furthermore, the pyrrolic-N species are energetically favorable for the adsorption of Zn+2 ions by the formation of N-Zn+2 chemical bonds. Besides, the nitrogen oxides reduce the intrinsic resistance and induce a more polarized surface, resulting in high wettability and efficient transfer of electrolytes into the pores of hydrophobic carbon materials. Subsequently, the chemically modified lignin-derived activated carbon material (Chem-ACM) as a cathode in ZICs delivers a high capacity of 161.2 mA h g−1 at 1 A g−1 with the admirable energy density of 106.7 W h kg−1 at 897 W kg−1 and excellent retention capacity (94%) after 10,000 cycles. Mainly, the assembled quasi solid-state ZICs using Chem-ACM retains the remarkable storage capacity (202 mA h g−1 at 0.2 Ag−1) even at a high bending angle. Notably, the Chem-ACM has been further employed in symmetric supercapacitors as an electrode, and it displays exceptional specific capacitance of 354 Fg−1 at 0.5 Ag−1 with tremendous energy (43.5 W h kg−1) and the power density (0.53 kW kg−1). Additionally, the charge storage capability of Chem-ACM is positively dependent on high nitrogen contents, and it is extrapolated that pyrrolic-N moieties are dominant active sites. Hence, the designed amination-assisted biocarbon synthesis provides a new way to prepare high nitrogen-containing biocarbon for ZICs and further understand pyrrolic-N species' impact on Zn-ion storage.

Application of Unsupervised Learning for the Evaluation of Burial Behavior of Geomaterials in Peatlands: Case of Lignin Moieties Yielded by Alkaline Oxidative Cleavage

Tropical Peatlands accumulate organic matter (OM) and a significant source of carbon dioxide (CO2) and methane (CH4) under anoxic conditions. However, it is still ambiguous where in the peat profile these OM and gases are produced. The composition of organic macromolecules that are present in peatland ecosystems are mainly lignin and polysaccharides. As greater concentrations of lignin are found to be strongly related to the high CO2 and CH4 concentrations under anoxic conditions in the surface peat, the need to study the degradation of lignin under anoxic and oxic conditions has emerged. In this study, we found that the "Wet Chemical Degradation" approach is the most preferable and qualified to evaluate the lignin degradation in soils accurately. Then, we applied PCA for the molecular fingerprint consisting of 11 major phenolic sub-units produced by alkaline oxidation using cupric oxide (II) along with alkaline hydrolysis of the lignin sample presented in the investigated peat column called "Sagnes". The development of various characteristic indicators for lignin degradation state on the basis of the relative distribution of lignin phenols was measured by chromatography after CuO-NaOH oxidation. In order to achieve this aim, the so-called Principal Component Analysis (PCA) has been applied for the molecular fingerprint composed of the phenolic sub-units, yielded by CuO-NaOH oxidation. This approach aims to seek the efficiency of the already available proxies and potentially create new ones for the investigation of lignin burial along a peatland. Lignin phenol vegetation index (LPVI) is used for comparison. LPVI showed a higher correlation with PC1 rather than PC2. This confirms the potential of the application of LPVI to decipher vegetation change, even in a dynamic system as the peatland. The population is composed of the depth peat samples, and the variables are the proxies and relative contributions of the 11 yielded phenolic sub-units.

Exploring Alkyl-O-Alkyl Ether Structures in Softwood Milled Wood Lignins.

Recent studies have suggested that there are significant amounts of various alkyl ether (Alk-O-Alk; Alk = alkyl) moieties in a spruce native lignin preparation, milled wood lignin (SMWL). However, the comprehensive NMR assignment to these moieties has not been addressed yet. This study focused on investigating different types of Alk-O-Alk structures at the α- and γ-positions of the lignin side chain in an heteronuclear single-quantum coherence (HSQC) spectrum of SMWL using experimental NMR data of lignin and synthesized model compounds. Ambiguous structural features were predicted by computer simulation of 1H and 13C NMR spectra to complement the experimental NMR data. As a result, specific regions in the HSQC spectrum were attributed to different Alk-O-Alk moieties of Alk-O-Alk/β-O-4 and Alk-O-Alk/β-β' structures. However, the differences between the specific regions were rather subtle; they were not well separated from each other and some major lignin moieties. Furthermore, SMWL contained a large variety of Alk-O-Alk moieties but in minute individual amounts, resulting in rather broad, superimposing resonances. Thus, evaluation did not allow assigning individual types of Alk-O-Alk moieties from the HSQC spectra; instead, they were quantified as total (α- and γ-linked) Alk-O-Alk based on the balance of structural units in the 13C NMR spectra. At last, potential formation mechanisms of various Alk-O-Alk ether structures in lignin biosynthesis, lignin aging, and during ball milling of wood were hypothesized and discussed.

Root Uptake Pathways and Cell Wall Accumulation Mechanisms of Organophosphate Esters in Wheat (Triticum aestivum L.)

The behavior of organophosphate esters (OPEs) in plants has drawn considerable attention because of their adverse effects to biota. However, the root uptake pathways and cell wall accumulation mechanisms of OPEs in plants are still unclear. In this study, the uptake pathways, subcellular distribution, and accumulation mechanisms of OPEs in wheat roots were elucidated. The results demonstrated that the symplast is the major pathway for uptake of both tris(2-chloroethyl) phosphate (TCEP) and triphenyl phosphate (TPHP) in wheat roots. Inhibitor experiments showed that the transmembrane transport of OPEs is a passive uptake process, and aquaporins and carrier proteins contribute to the uptake of OPEs. More than 69% of TCEP was accumulated in cell sap due to its high hydrophilicity, while the hydrophobic TPHP was mainly stored in the root cell wall. The sorption affinity of TPHP decreased gradually following the sequential fractionation of wheat roots, which confirmed the significant contribution to TPHP sorption on wheat roots. A significant positive correlation between the sorption affinity values and the percentage of aromatic carbon was observed (r2 = 0.856, p < 0.01), indicating that the accumulation of hydrophobic OPEs in roots does not just depend on lipids alone, but the aromatic moieties of lignin in the cell wall also contribute to OPE accumulation.

Oxidation of Lignin-Carbohydrate Complex by Laccase/Co(salen) One-Pot Catalysis

Lignin-carbohydrate complex (LCC) is hybrid structures containing covalently linked moieties of lignin and carbohydrates. The nature and amount of LCC affect both industrial processes and practical applications of lignocellulosic biomass. Herein, the LCC was isolated from bamboo by successive solvent extraction and precipitation. The effects and mechanism of LCC oxidation respectively by laccase, Co(salen), and laccase/Co(salen) in the presence of molecular oxygen have been investigated by composition analysis using the standard of National Renewable Energy Laboratory (NREL) and high-performance anion exchange chromatography (HPAEC), GPC, FTIR, and 2D-HSQC NMR. We can conclude that the laccase/Co(salen) one-pot catalysis modified the LCC in such a way that more carbohydrate was removed from the LCC with lower molecular weight of LCC as shown by GPC; the catalytic treatments produced oxidation at lignin side-chains and cleavage of lignin β-O-4', β-β' and β-5' bonds in LCC, and cleavage of benzyl-sugar ether, phenyl glycoside and γ-ester bonds in LCC, as shown by FTIR and 2D-HSQC NMR, especially after the laccase/Co(salen) one-pot treatment. The further insight of LCC degradation was discussed in light of the results obtained in oxidation of the LCC model compound coniferin.

Modeling the Conformational Preference of the Lignocellulose Interface and Its Interaction with Weak Acids.

We have examined the conformational space of model systems for the hydrogen-bonded and covalent linkages between the sugar and lignin components of lignocellulose. Specifically, glucose and paracoumaryl alcohol moieties are used in our models. Multistage screening protocols are used to identify and validate a set of lowest-energy isomers. We found a cost-effective screening process involving an initial screening with DFTB3/3ob using a 20 kJ mol-1 threshold, a refinement with the SCANh/6-31+G(2d,p) method with a 10 kJ mol-1 cutoff, a third step at the DSD-PBEP86/ma-def2-TZVP//MS1-D3/6-31+G(2d,p) level with the same 10 kJ mol-1 threshold, and a last step at the CCSD(T)/CBS//B3LYP/cc-pVTZ level with a tighter 5 kJ mol-1 threshold. The use of machine learning (with the London and Axilrod-Teller-Muto potential) can further accelerate the screening process. In general, all low-energy conformers are characterized by hydrogen bonding between the sugar and lignin moieties. We examined the interactions of covalently bonded sugar-lignin models with weak acids (HSO3-, H2PO3-, HSeO3-, H2citrate-, etc.) and found that they interacted strongly with the oxygen of the sugar-O-lignin linkage. Our results suggest that acids such as dihydrogen citrate may be attractive alternatives to the commonly used HSO3- for lignocellulose processing.

A feasibility study on green biorefinery of high lignin content agro-food industry waste through supercritical water treatment

This work discusses hydrolysis of defatted grape in supercritical water (SCW) at 380 °C and 260 bar from 0.18 s to 1 s focusing attention to sugars recovery in the liquid phase of the product and detailed characterization of remaining solid phase enriched in polyaromatics (e.g. lignin, flavonoids, etc.). After the longest reaction time of 1 s, 56% of carbohydrates could be recovered in the liquid phase, as a result of carbohydrate hydrolysis. The high content of insoluble lignin in biomass (36%), acts as a mass transfer limitation and presents an important feature in the hydrolysis process, slowing down the conversion of carbohydrate fraction, as after the maximum time of 1s, 10% of carbohydrates still remained in the solid phase. Milled wood lignin, extracted from biomass and dioxane extract from the solid phase were characterized in order to understand the main structural changes during the SCW hydrolysis process. Dioxane (80%) extraction of solids produces a very complex mixture of lipophilic extractives, flavonoids and lignin with a certain amount of chemically linked carbohydrates. 2D NMR analysis of dioxane extract shows remarkably subtle changes in the amounts of main lignin moieties (β-O-4′, β-β’ (resinol) and β-5 (phenylcoumaran)). This subtle change of the main lignin structures is an important feature in the further valorisation of this sulfur-free lignin residue.

Evolution of Composting Process in Maize Biomass Revealed by Analytical Pyrolysis (Py-GC/MS) and Pyrolysis Compound Specific Isotope Analysis (Py-CSIA)

An innovative approach based on the combination of analytical pyrolysis coupled with gas chromatography-mass spectrometry (Py-GC/MS) with compound-specific isotope analysis (Py-CSIA) is used to study the composting process of maize biomass. This multidisciplinary approach aims to elucidate the decomposition rate of the main biogenic materials (lignin, cellulose, proteins, lipids, and waxes) responses to the composting process. According to Py-GC/MS data/structural composition, a noticeable and significant decrease during the first stage of the composting process of carbohydrates and aromatic compounds is found, followed by a gradual increase of all compounds till the end of the experiment. This trend, along with an increase of fatty acids methyl-ester at the first composting stage, sustains the microbial activity and its stabilization over time. Py-CSIA data showed a significant enrichment in 13C in all identified compounds over time, supporting the semi-quantitative results and the decomposition of initial biomass throughout the composting process. This trend is also perceptible in lignin moieties, long-chain aliphatic structures, and isoprenoids, as highly recalcitrant compounds, presumably due to depolymerization and carbon translocation of side-chain molecules during the composting process. Compound-specific isotope values showed a good correlation with the bulk isotope data, and this served as validation of the technique. However, bulk values showed higher heterogeneity because those represent an average of all organic compounds in the sample. By combining isotopic and structural information using Py-GC/MS and Py-CSIA, we are able to provide further information and a more detailed approach to the study of the decomposition process of biomass by considering the diverse dynamics of the main biogenic compounds.

Non-enzymatic colorimetric biosensor for hydrogen peroxide using lignin-based silver nanoparticles tuned with ionic liquid as a peroxidase mimic

Hydrogen peroxide (H2O2) is a byproduct of oxidative metabolism, acts as a signaling molecule, and can induce protein and DNA damage by oxidative stress. Ionic liquid-coated lignin stabilized silver nanoparticles (LAgNPs) have been used for the colorimetric detection of H2O2. Both ionic liquid and lignin moieties have a synergistic effect on the conductivity of silver nanoparticles to display intrinsic peroxidase-like activity with the enhanced potential to catalyze the oxidation of substrate 3,3′,5,5′-tetramethylbenzidine (TMB). LAgNPs have been synthesized by the green synthesis method and the prepared nanoparticles have been characterized by different techniques such as FTIR, EDX, TGA, SEM, and XRD. 1-H-3-methylimidazolium acetate (ionic liquid) was prepared and used for tuning of AgNPs. By using ionic liquid capped LAgNPs the colorimetric detection of H2O2 was done with the assistance of TMB solution and results were analyzed by UV–Vis spectrophotometer. Different parameters such as (amount of capping agent and TMB, pH, H2O2 concentration, and time) were optimized to get the best results of the proposed sensor. The H2O2 biosensor exhibited a linear response in the range of 1 × 10−9–3.6 × 10−7 M, with a detection limit of 1.379 × 10−8 M and a quantification limit of 4.59 × 10−8 M, and R2 of 0.999. The sensor gave a short response time of 5 min for colorimetric detection of H2O2 at pH 7.5 and room temperature. For the detection of hydrogen peroxide, the proposed sensor showed good sensitivity and selectivity and was successfully employed for the detection of H2O2 in the blood serum samples of hypertension patients.

Characterization of a lignin-based gel responsive to aqueous binary solvents and pH

Abstract A lignin-based gel (AL-PE gel) was obtained from hardwood acetic acid lignin (AL) and poly(ethylene glycol) diglycidyl ether (PE) as a cross-linker at a high AL concentration, while the reaction at a lower AL concentration yielded an amphipathic derivative (am-AL-PE). The gel has been reported to swell in aqueous ethanol but shrink in pure water and ethanol. In the present work, swelling behaviors in other aqueous binary solvents and the swelling mechanism were investigated to explore novel lignin-based functional materials, such as stimuli-and/or environment-responsive gels. The AL-PE gel swelled in aqueous methanol, isopropanol, acetone, and tetrahydrofuran, and the order of swelling in the solvents was consistent with that of the am-AL-PE. Spin-spin relaxation time (T 2 ) measurements with 1H NMR analysis of the gel in aqueous acetone revealed that gel swelling was closely related to an increasing T 2 of acetone bound to the gel network. The nature of the lignin moiety in the gel also enabled a pH response, and the amphipathic nature of the gel provided it with a function as an absorbent for cationic surfactants. The results of this study can contribute to the valorization of lignin as a main component for solvent sensors and environmental purification materials.

Active role of lignin in anchoring wood-based stabilizers to the emulsion interface

Lignin moieties anchoring and delivering wood-based stabilizers to the interface improve the physical stabilization of emulsions.