Hydroxyl Content Research Articles

Climate warming inhibits neonicotinoid photodegradation on vegetable leaves: Important role of the olefin group in leaf wax

Neonicotinoid photodegradation is seldom considered in different vegetable leaves after spraying under climate warming. This study investigated the effect of elevated cultivated temperature from 15/10 °C to 21/16 °C on the photodegradation of dinotefuran, thiamethoxam, acetamiprid, and thiacloprid on four vegetable leaves under simulated sunlight irradiation. The photodegradation rates of neonicotinoids on spinach leaves were 1.1–1.6, 1.1–2.0, and 1.4–2.4 times higher than those on pak choi, Chinese cabbage, and radish leaves, respectively. The higher production concentrations of hydroxyl radicals (•OH) and superoxide radicals in spinach leaf wax may contribute to the fastest photodegradation among four vegetables. When the cultivated temperature increased from 15/10 °C to 21/16 °C, neonicotinoid photodegradation rates decreased by 1.4–2.8 times on the four vegetables. Elevated cultivated temperature decreased the polarity of wax, which reduced the contact probability of neonicotinoids with reactive species on vegetable leaves and photodegradation rates. A positive linear correlation was found between the content of CHCH groups in wax determining •OH generation and the neonicotinoid photodegradation rates on four vegetable leaves cultivated at three temperatures (R2 = 0.67–0.94). Insights into neonicotinoid photodegradation on edible vegetables under climate warming are of great significance for better evaluating human exposure to neonicotinoids through the dietary pathway.

Structural and Surface Changes of SiO2 Flint Aggregates under Thermal Treatment for Potential Valorization

In order to extend their use, controlled SiOH SiO2 surfaces were fabricated and investigated. A study of the effect of heat treatment on the structural and surface changes of a natural flint SiO2 aggregate subjected to chemical treatment was carried out. The obtained samples were subjected to thermal treatment at three different temperatures: 500, 700, and 1000 °C. The samples were investigated using different techniques. X-ray diffractions (XRD) were used to follow the structure’s evolution with the heat treatment. The decrease in the FWHM of the SiO2-(101) peak showed that the crystalline quality improved upon heating. This result was confirmed by Fourier transform infrared spectroscopy (FTIR). The morphology of the SiO2 samples was characterized using a Variable Pressure scanning electron microscope (VP-SEM), revealing the presence of disordered needles of nanometric sizes (∼500 nm) on the surface of the grains, which could be eliminated by heating at higher temperatures. Furthermore, FTIR spectroscopy also confirmed that heating caused a reduction in OH groups on the surface. Thermogravimetry (TG) was used as the reference method to determine the hydroxyl group content. The OH groups found on the surface of the sample without and with heat treatment at 500, 700, and 1000 °C were 0.83, 0.44, 0.28, and 0.2 mmol/g, respectively. This study allowed us to obtain a controlled SiO2 surface and provides new insights into the use of SiO2 flint surfaces for new applications as a functional filler in polymers/asphalts composites.

Formalism of the NanOx biophysical model for radiotherapy applications

Introduction: NanOx is a theoretical framework developed to predict cell survival to ionizing radiation in the context of radiotherapy. Based on statistical physics, NanOx takes the stochastic nature of radiation at different spatial scales fully into account. It extends concepts from microdosimetry to nanodosimetry, and considers as well the primary oxidative stress. This article presents in detail the general formalism behind NanOx.Methods: Cell death induction in NanOx is modeled through two types of biological events: the local lethal events, modeled by the inactivation of nanometric sensitive targets, and the global events, represented by the toxic accumulation of oxidative stress and sublethal lesions. The model is structured into general premises and postulates, the theoretical bases compliant with radiation physics and chemistry, and into simplifications and approximations, which are required for its practical implementation.Results: Calculations performed with NanOx showed that the energy deposited in the penumbra of ion tracks may be neglected for the low-energy ions encountered in some radiotherapy techniques, such as targeted radionuclide therapy. On the other hand, the hydroxyl radical concentration induced by ions was shown to be larger for low-LET ions and to decrease faster with time compared to photons. Starting from the general formalism of the NanOx model, an expression was derived for the cell survival to local lethal events in the track-segment approximation.Discussion: The NanOx model combines premises of existing biophysical models with fully innovative features to consider the stochastic effects of radiation at all levels in order to estimate cell survival and the relative biological effectiveness of ions. The details about the NanOx model formalism given in this paper allow anyone to implement the model and modify it by introducing different approximations and simplifications to improve it, or even adapt it to other medical applications.

A functional lignin for heavy metal ions adsorption and wound care dressing

Recently, the application of lignin activation by demethylation to improve reactivity and enrich multiple functions has intensively attracted attention. However, it is still challenge up to now due to the low reactivity and complexity of lignin structure. Here, an effective demethylation way was explored by microwave-assisted method for substantially enhancing the hydroxyl (-OH) content and retaining the structure of lignin. Then, the optimum demethylated lignin was used to removal heavy metal ions and promote wound healing, respectively. In detail, for microwave-assisted demethylated poplar lignin (M-DPOL), the contents of phenolic (Ar-OH) and total hydroxyl (Tot-OH) groups reached the maximum for 60 min at 90 °C in DMF with 7.38 and 9.13 mmol/g, respectively. After demethylation, with this M-DPOL as lignin-based adsorbent, the maximum adsorption capacity (Qmax) for Pb2+ ions reached 104.16 mg/g. Based on the isotherm, kinetic and thermodynamic models analyses, the chemisorption occurred in monolayer on the surface of M-DPOL, and all adsorption processes were endothermic and spontaneous. Meanwhile, M-DPOL as a wound dressing had excellent antioxidant property, outstanding bactericidal activity and remarkable biocompatibility, suggesting that it did not interfere with cell proliferation. Besides, the wounded rats treated with M-DPOL significantly promoted its formation of re-epithelialization and wound healing of full-thickness skin defects. Overall, microwave-assisted method of demethylated lignin can offer great advantages for heavy metal ions removal and wound care dressing, which facilitates high value application of lignin.

1-ethyl-3-methyl imidazolium acetate, hemicellulolytic enzymes and laccase-mediator system: Toward an integrated co-valorization of polysaccharides and lignin from Miscanthus

The pretreatment of Miscanthus x giganteus with the ionic liquid 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]), followed by enzymatic hydrolysis and oxidative depolymerization, resulted in the efficient production of monomeric sugars and selective production of phenolic intermediates. The liquid fractions containing monomeric sugars were obtained with high yields (>80%), while a solid fraction enriched with lignin (>50% w.w−1) was isolated. The phenolic monomers released during [Emim][OAc]-pretreatment were identified and quantified by HPLC. A decrease in the content of vanillin, vanillic acid, and p-hydroxybenzaldehyde was observed during pretreatment, suggesting a selective solubilization of guaicyl and p-hydroxyphenyl units from the lignin polymer in [Emim][OAc]. The decrease in p-coumaric and ferulic acids content suggested a cleavage of lignin-carbohydrate complexes during pretreatment. Both pretreatment and enzymatic hydrolysis affected the content of ferulic acid ether and ester bonds. The NMR structural study (2D HSQC) of the isolated lignin showed the preservation of β-O-4′ interunit bonds, while 31P NMR analysis revealed a high content of aliphatic hydroxyl groups. The oxidative depolymerization of the isolated lignin, catalyzed by the laccase mediator system in the presence of 5% v.v−1 recycled [Emim][OAc] in buffer, mainly led to the production of free p-hydroxybenzaldehyde as a promising platform molecule. The mass balance of glucan, xylan and lignin from Miscanthus was validated throughout this strategy.

Changes in the structure of polysaccharides under different extraction methods

Changes in the structure of polysaccharides under different extraction methods

The effect of protein oxidation on the formation of advanced glycation end products after chicken myofibrillar protein glycation

Investigation that protein oxidation to the formation of advanced glycation end products (AGEs) after chicken myofibrillar protein glycation is limited. Models of protein oxidation induced by different concentrations of hydroxyl radicals (·OH) were developed after the chicken myofibrillar protein mild glycation (MPG). Results exhibited that levels of AGEs and surface hydrophobicity (H0) steadily increased with the addition of hydrogen peroxide (H2O2) concentration. However, levels of sulfhydryl group, free amino group, and particle size gradually decreased with the H2O2 concentration. The protein carbonyl value increased in H2O2 concentration until 10 mmol/L. Pearson’s correlation indicated that MPG structure modification (unfolding and degradation) induced by protein oxidation were significantly positively correlated with AGEs concentration (P < 0.05). Finally, a mechanism was proposed to hypothesize the effect of protein oxidation on the formation of AGEs under MPG conditions.

Synthesis and Characterization of Sol–Gel‐Derived SiO2–CaO Particles: Size Impact on Glass (Bio)Properties

AbstractFour highly bioactive glasses in a binary SiO2–CaO system are prepared following a sol−gel method using Ca(OH)2 as a calcium precursor. In the synthesis of glass according to the modified Stöber method, Ca(OH)2 suspended in polyethylene glycol allows the elimination of the presence of calcite and the increase of ammonia concentration causes formation of spherical particles with different sizes in the range of 26–266 nm. The relation among the size and properties, including bioactivity, of the glass particles is evaluated. New glasses that vary in composition (10–25 wt% CaO), porosity (15–113 m2 g−1), and hydroxyl groups content greatly enhance the formation process of hydroxyapatite (HA) in simulated physiological fluids. For all glasses, superior apatite‐mineralization ability in time as short as 2 h in the physiological‐like buffer is achieved, thus exceeding the bioactivity of the known bioactive glasses, including 45S5 glass (Bioglass). The assessment of the safety and toxicity profile of the obtained glasses is verified in a wide range of concentrations (1–1000 µg mL−1) against human dermal fibroblasts and MC3T3 mouse osteoblast precursors, but also to human erythrocytes by determining hemocompatibility. Two glasses of different sizes, 73 and 266 nm, are promising and warrant further research.

Critical role of water in fused silica glass by silica nanopowder sintering: Nanoparticle dispersion

Thermoplastic nanocomposite preparation using a silica nanopowder/polyethylene glycol (PEG) / polyvinyl butyral (PVB) system followed by heat-treatment sintering to obtain fused silica glass has high precision, scalable manufacturing processes, and short processing time. However, conventional solvents are toxic and harmful to the environment, and for this reason, the ethanol/water solvent system was proposed in this study. In this study, the effect of water content on the dispersion effect of nano-silica suspensions was investigated through particle size and zeta potential tests and FTIR spectra analysis; in addition, the study proposes a dispersion theory based on the solvation layer of the ethanol/water competitive adsorption and viscosity effect. Finally, optical photographs and SEM characterization showed that the obtained fused silica glass was transparent and had no seam defects, and the XRD and hydroxyl group tests showed that the glass had a low hydroxyl group content of only 2.55 ppm.

Luminescent defect centers in magnesium-doped lithium niobate crystals

The photoluminescence of LiNbO3:Mg(0.19÷5.29 mol.% MgO) crystals obtained by various technologies has been studied in the near IR region. It showed that a contribution to the photoluminescence of the crystals was made by two main bands at 1.53 and 1.35 eV being associated with intrinsic defect centers in the crystals. The intensity of these bands, especially the band at 1.53 eV, in LiNbO3:Mg(0.19÷5.29 mol.% MgO) crystals correlated well with the concentration of hydroxyl groups in ones. Therefore, there was a complex luminescence center including OH- groups in the crystals.

Biodegradable Block Poly(ester amine)s with Pendant Hydroxyl Groups for Biomedical Applications.

The article presents the results of the synthesis and characteristics of the amphiphilic block terpolymers, built of a hydrophilic polyesteramine block, and hydrophobic blocks made of lactidyl and glycolidyl units. These terpolymers were obtained during the copolymerization of L-lactide with glycolide carried out in the presence of previously produced macroinitiators with protected amine and hydroxyl groups. The terpolymers were prepared to produce a biodegradable and biocompatible material containing active hydroxyl and/or amino groups, with strong antibacterial properties and high surface wettability by water. The control of the reaction course, the process of deprotection of functional groups, and the properties of the obtained terpolymers were made based on 1H NMR, FTIR, GPC, and DSC tests. Terpolymers differed in the content of amino and hydroxyl groups. The values of average molecular mass oscillated from about 5000 g/mol to less than 15,000 g/mol. Depending on the length of the hydrophilic block and its composition, the value of the contact angle ranged from 50° to 20°. The terpolymers containing amino groups, capable of forming strong intra- and intermolecular bonds, show a high degree of crystallinity. The endotherm responsible for the melting of L-lactidyl semicrystalline regions appeared in the range from about 90 °C to close to 170 °C, with a heat of fusion from about 15 J/mol to over 60 J/mol.

Use of a new ZnFe2O4/biochar composite for degradation and ecotoxicity assessment of effluent containing methylene blue dye

In this study, biochar from coffee grounds was used for the first time as a support for ZnFe2O4 and its application and evaluation as a photocatalyst in methylene blue dye degradation reactions. The new composites were verified by different characterization techniques: XRD, FT-IR, SEM, EDS and band gap. The effect of different proportions of ZnFe2O4 and biochar was investigated on the dye degradation efficiency. The composites ZFO1HC3, ZFO1HC1 and ZFO3HC1 showed 93, 100 and 100% degradation in 60 min of reaction, respectively. The composites were more efficient than pure ZnFe2O4 (∼37% degradation), and this may be related to the fact that the biochar has a high concentration of phenolic, hydroxyl and carboxylic functional groups on its surface. Furthermore, this may be associated with a decrease in band gap energy and in the recombination rate of e¯/h+ pairs. Radical identification tests indicated that h+, O2− and OH were the reactive species involved in the degradation. In addition, to assess the potential toxicity of the effluent containing methylene blue, Danio rerio fish were exposed for 96 h to the crude and treated dye solution. Results showed changes in biomarkers in the gills, such as an increase in catalase activity in the group exposed to untreated methylene blue, and a reduction in glutathione S-transferase activity in this same group. Thus, the set of biomarkers evaluated in fish exposed to effluent containing methylene blue treated with a new ZnFe2O4/biochar composite showed better results when compared to those exposed to raw effluent.

Structural Characterization of Acid DES-Modified Alkaline Lignin and Evaluation of Antioxidant Properties

Lignin is an abundant and environmentally friendly biopolymer that contains a large number of phenolic hydroxyl functional group. In this paper, alkaline lignin was modified using different acidic DES (choline chloride/p-toluenesulfonic acid and choline chloride/lactic acid) at 130 ℃ (TC-lignin and LC-lignin) and the conformational relationship between the modified products and the antioxidant activity was investigated. Lignin was characterized by 31P NMR, gel permeation chromatography (GPC) and Fourier transform infrared spectroscopy (FT-IR), and its antioxidant activity was evaluated. The results showed that the alkaline lignin products modified by acidic DES formed relatively homogenous dispersions and were characterized by a relatively low molecular weight and a high content of phenolic hydroxyl groups (e.g., TC-lignin, aliphatic-OH: 3.52 mmol/g, G-OH: 4.18 mmol/g, Mw: 3726, Mn: 2053, PDI: 1.81). The antioxidant activity (free radical scavenging rate, 90.35%) of TC-lignin was somewhat higher than that of LC-lignin (free radical scavenging rate, 89.12%) and both were higher than that of the commercially available antioxidant BHT (free radical scavenging rate, 88.79%). More specifically, we discussed the possible mechanisms of antioxidant reactions of lignin model substances in DPPH solutions. In addition, LC-lignin has an excellent UV-blocking capacity due to the specific phenolic hydroxyl and phenyl propane structure. A simple method is proposed for the modification of industrial lignin to make it suitable for use as an antioxidant and UV-resistant product.

Visible-infrared optical performance of Er3+-doped fluorotellurite glass via hybrid structural fluctuations

Improving the physicochemical and optical properties of erbium ion-doped fluorotellurite glass is key to addressing the performance bottleneck of current commercial silicon-based fiber amplifiers. In this study, the ZnF2 is used to reduce the hydroxyl content in the tellurite glass matrix, which improved the fluorescence efficiency. Further, the WO3 modifier is introduced to enable the transformation of TeO4→TeO3+δ→TeO3 and the formation of the octahedral [WO6] units and tetrahedral [WO4] units, as demonstrated by Raman spectroscopy and X-ray photoelectron analysis. Finally, Er3+-doped fluorotellurite glass with stable thermal properties is obtained by adjusting the glass topology. Its excellent visible-near-mid-infrared optical properties make it a promising candidate material for infrared fiber amplifiers and gain media for rare-earth-doped solid-state lasers.

Effect of microwave pretreatment on oxidization behaviors of bituminous coal: Experimental measurement and quantum chemistry calculation

The poor heat conduction and mass transfer of coal seam causes unsatisfying performance of gas production for in situ combustion, while microwave pretreatment is a promising technology to solve this problem. In this work, microwave heating is adopted as pretreatment method to prepare coal samples at different microwave time. The low temperature oxidization and high temperature combustion behaviors of raw coal and modified coal samples were studied with programmed temperature rising method. The functional group content in coal samples were measured with Fourier transform infrared spectrometer, while the relationship between microstructure and reactivity was studied with quantum chemistry calculation. As microwave heating time extends from 0 s to 180 s, the crossing point temperature decreases, while the combustion reaction rate increases. As microwave time prolongs from 180 s to 240 s, the crossing point temperature becomes larger, while the combustion reaction rate becomes smaller. As microwave time increases from 0 s to 240 s, hydroxyl content and carbonyl content in coal samples reduce while ether content rises. The reduction of hydroxyl and increase of ether result in an enhancement of oxidization reactivity. The decrease of carbonyl is unfavorable for oxidization reactivity. Therefore, the effect of microwave heating on coal reactivity has two sides. This explains why the microwave pretreatment time has a non-monotonic effect on the coal reactivity in both low temperature and high temperature range.

Lignin-based polymer with high phenolic hydroxyl group content prepared by the alkyl chain bridging method and applied as a dopant of PEDOT

Lignin-based polymer with high phenolic hydroxyl group content prepared by the alkyl chain bridging method and applied as a dopant of PEDOT

Formulation of polymeric particles with controlled charges by alkaline tempering

The control of surface charge of polymeric microparticles is a major challenge because electrostatic interactions stabilize their aqueous suspensions. In this study, anionic PMMA particles were prepared with 5 wt% of methacrylic acid as a comonomer. This comonomer was expected to give a negative charge to the particles, but none was observed from zeta potential measurements. The evolution of the zeta potential in alkaline medium was investigated to better understand this observation. It was demonstrated that the acid groups were present almost only in the core of the particles and that their deprotonation was possible using an alkaline tempering. Two phenomena occurred simultaneously leading to the charge appearance at the particle surface: i) the diffusion of hydroxide ions into the particles, allowing the migration of the negative charges to the particle surface with an appearance rate per mol of particles of 2.0 10−3m3 mol−1 s−1 (multiplied by the hydroxyl ion concentration), and ii) the hydrolysis of ester groups of methyl methacrylate units characterized by a pseudo first order kinetics with k = 3.0 10−9 m3 mol−1 s−1. By carefully choosing the parameters of the tempering process, hydrolysis is minimized and anionic particles can be prepared with stable and controlled charges coming from the anionic comonomer. Doing so, anionic PMMA-like particles exhibited a stable zeta potential of −11.5 mV.

Study on the Occurrence Difference of Functional Groups in Coals with Different Metamorphic Degrees.

In order to quantitatively study the difference in occurrence content of functional groups in coals with different metamorphic degrees, the samples of long flame coal, coking coal, and anthracite of three different coal ranks were characterized by FTIR and the relative content of various functional groups in different coal ranks was obtained. The semi-quantitative structural parameters were calculated, and the evolution law of the chemical structure of the coal body was given. The results show that with the increase in the metamorphic degree, the substitution degree of hydrogen atoms on the benzene ring in the aromatic group increases with the increase in the vitrinite reflectance. With the increase in coal rank, the content of phenolic hydroxyl, carboxyl, carbonyl, and other active oxygen-containing groups gradually decreased, and the content of ether bonds gradually increased. Methyl content increased rapidly first and then increased slowly, methylene content increased slowly first and then decreased rapidly, and methylene content decreased first and then increased. With the increase in vitrinite reflectance, the OH-π hydrogen bond gradually increases, the content of hydroxyl self-association hydrogen bond first increases and then decreases, the oxygen-hydrogen bond of hydroxyl ether gradually increases, and the ring hydrogen bond first significantly decreases and then slowly increases. The content of the OH-N hydrogen bond is in direct proportion to the content of nitrogen in coal molecules. It can be seen from the semi-quantitative structural parameters that with the increase in coal rank, the aromatic carbon ratio fa, aromatic degree AR and condensation degree DOC increase gradually. With the increase in coal rank, A(CH2)/A(CH3) first decreases and then increases, hydrocarbon generation potential 'A' first increases and then decreases, maturity 'C' first decreases rapidly and then decreases slowly, and factor D gradually decreases. This paper is valuable for analyzing the occurrence form of functional groups in different coal ranks and clarifying the evolution process of structure in China.

Study of Phenol Red Photocatalytic Decomposition on KBrO3-Supported TiO2 Nanoparticles for Wastewater Treatment

In this study, the enhanced photodegradation of a high-concentration phenol red (PR) using very fine TiO2 nanocrystals by adding a KBrO3 electron acceptor was reported for the first time. The structural study on TiO2 nanocrystals using HRTEM, XRD, Raman, and EDX was performed and it confirmed the anatase phase of TiO2 nanocrystals. UV–Vis absorbance of 20 mg.L−1 PR was measured and the photodegradation was extracted. The KBrO3 concentration effects exhibited an important enhancement in the degradation of PR dye. The efficiency of PR was increased during 110 min from 75% of pure TiO2 to 92% and 98% of TiO2 with 1 mg and 5 mg KBrO3, respectively. For different samples, a first-order kinetic of dye degradation is confirmed. The instantaneous amount of degraded dye increased from 150 to 180 and 197 mg/g TiO2 with 1 mg and 5 mg KBrO3, respectively. The mechanism of the photodegradation reaction confirms the effect of OH- radicals on increasing the photocatalytic activities. The addition of electron acceptors KBrO3 improved the photocatalysis rate, where it prevented e-h recombination through conduction band electron capture, which increases the concentration of hydroxyl radicals. The proposed mechanism and results were supported by photocurrent measurements and a Raman spectra analysis of the final photodegraded products. The photocurrent of TiO2 was observed at 1.2 µA, which was significantly improved up to 13.2, and 21.3 µA with the addition of 1 mg and 5 mg of KBrO3. The Raman spectra of the final products confirmed that SO42− and carbons are byproducts of PR degradation.

Removal of hydroxyl groups and its influence on the microstructures evolution of alumina-mullite fibers fabricated by sol-gel process

Hydroxyl groups are essential groups in the preparation of alumina-mullite fibers by the sol-gel process, which contributes to the formation of spinnable precursor sol. In this work, the removal of hydroxyl groups during pyrolysis and sintering, and its effect on fibers phase transition and microstructural evolution were systematically studied. Five pyrolyzed alumina-mullite fibers samples with different hydroxyl groups content were obtained by adjusting the pyrolysis temperature or introducing water vapor. It was revealed that the removal of hydroxyl groups existed throughout the sintering process, mainly concentrated before 800 °C. The mullitization temperature of the pyrolyzed fibers with more hydroxyl groups was about 1300 °C, while that of pyrolyzed fibers with fewer hydroxyl groups was 700 °C. In addition, an appropriate amount of residual hydroxyl groups (13.3 wt%) was beneficial to obtain a dense fine-grained microstructure of the pyrolyzed fibers after sintering, and the tensile strength of the fibers was increased to 1.6 ± 0.22 GPa. Finally, the influence mechanism of different hydroxyl content on the alumina-mullite fibers was discussed.