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Antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are emerging contaminants that widely exist in the environment. Effective reduction of ARB and ARGs from soil and water could be achieved by electrokinetic remediation (EKR) technology. In water, hydroxyl radicals (·OH) are proved to play a major role in the EKR process; while the reduction mechanism of ARB and ARGs is still unclear in soil. In this study, different concentrations of hydroxyl radical scavengers (salicylic acid) were added to the EKR system to explore the possible role of ·OH in the reduction of ARB and ARGs. The results showed that generally, ·OH played a more vital role in the reduction of ARB (65.24-72.46%) compared to the reduction of total cultivable bacteria (57.50%). And ·OH contributed to a higher reduction of sul genes (60.94%) compared to tet genes (47.71%) and integrons (36.02%). It was found that the abundance of Gram-negative bacteria (Chloroflexi, Acidobacteria and norank_c_Acidobacteria) was significantly reduced, and the correlation between norank_f_Gemmatimonadaceae and sul1 was weakened in the presence of ·OH. Correlation analysis indicated that the abundance of ARGs (especially sul1) was closely related to the Gram-negative bacteria (Proteobacteria, Acidobacteria, and Gemmatimonadetes) in the soil EKR treatment. Moreover, changes in bacterial community structure affected the abundance of ARB and ARGs indirectly. Overall, this study revealed the reduction mechanism of ARB and ARGs by ·OH in the soil EKR system for the first time. These findings provide valuable support for soil remediation efforts focusing on controlling antibiotic resistance., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Hydroxyl radical (HO • ) and chlorine atom (Cl • ) are common reactive species in aqueous environments. However, the intrinsic difference in their reactions with organic compounds has not been revealed. This study compared the reaction mechanisms of HO • and Cl • with 13 aromatic and 11 aliphatic compounds by quantum chemical calculation and laser flash photolysis. Both HO • and Cl • can spontaneously react with aromatic compounds via radical adduct formation (RAF), hydrogen atom transfer (HAT), and single electron transfer (SET) pathways. The SET reactions of Cl • were more thermodynamically favorable than HO • , but contrary results were obtained for HAT reactions. According to the free energy of activation (Δ G aq ‡ ), the dominant oxidation mechanisms of aromatic compounds were RAF and SET by HO • and SET by Cl • . The important role of SET in the HO • reactions with aromatic compounds was further verified by accurately calculating the solvation free energy of HO • /HO - and experimentally tracking the radical cations, which were generally neglected in previous studies. Meanwhile, the Δ G aq ‡ value of each reaction pathway of Cl • was lower than that of HO • , resulting in higher rate constants of Cl • with aromatic compounds than HO • . For saturated aliphatic compounds, HAT was found to be the only mechanism accounting for their transformation by HO • and Cl • . This study proposed general rules for the reaction mechanisms of HO • and Cl • and unraveled their differences in the aspects of thermodynamics and kinetics, providing fundamental information for understanding contaminant transformation in processes involving HO • and Cl • .

The hydroxyl radical (OH) is highly reactive and plays a significant role in a number of physiological and pathological processes within biosystems. Aberrant changes in the level of hydroxyl radical are associated with many disorders including tumor, inflammatory and cardiovascular diseases. Thus, detecting reactive oxygen species (ROS) in biological systems and imaging them is highly significant. In this work, a novel fluorescent probe (HR-DL) has been developed, targeting two organelles simultaneously. The probe is based on a coumarin-quinoline structure and exhibits high selectivity and sensitivity towards hydroxyl radicals (OH). When reacting with OH, the hydrogen abstraction process released its long-range π-conjugation and ICT processes, leading to a substantial red-shift in wavelength. This probe has the benefits of good water solubility (in its oxidative state), short response time (within 10 s), and unique dual lysosome/mitochondria targeting capabilities. It has been applied for sensing OH in biosystem and inflammation mice models., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Harnessing bacteria for superoxide production in bioremediation holds immense promise, yet its practical application is hindered by slow production rates and the relatively weak redox potential of superoxide. This study delves into a cost-effective approach to amplify superoxide production using an Arthrobacter strain, a prevalent soil bacterial genus. Our research reveals that introducing a carbon source along with specific iron-binding ligands, including deferoxamine (DFO), diethylenetriamine pentaacetate (DTPA), citrate, and oxalate, robustly augments microbial superoxide generation. Moreover, our findings suggest that these iron-binding ligands play a pivotal role in converting superoxide into hydroxyl radicals by modulating the electron transfer rate between Fe(III)/Fe(II) and superoxide. Remarkably, among the tested ligands, only DTPA emerges as a potent promoter of this conversion process when complexed with Fe(III). We identify an optimal Fe(III) to DTPA ratio of approximately 1:1 for enhancing hydroxyl radical production within the Arthrobacter culture. This research underscores the efficacy of simultaneously introducing carbon sources and DTPA in facilitating superoxide production and its subsequent conversion to hydroxyl radicals, significantly elevating bioremediation performance. Furthermore, our study reveals that DTPA augments superoxide production in cultures of diverse soils, with various soil microorganisms beyond Arthrobacter identified as contributors to superoxide generation. This emphasizes the universal applicability of DTPA across multiple bacterial genera. In conclusion, our study introduces a promising methodology for enhancing microbial superoxide production and its conversion into hydroxyl radicals. These findings hold substantial implications for the deployment of microbial reactive oxygen species in bioremediation, offering innovative solutions for addressing environmental contamination challenges., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article., (Copyright © 2023. Published by Elsevier B.V.)

In most of advanced oxidation processes (AOPs) used to destroy harmful organic chemicals in water/wastewater hydroxyl radical ( • OH) reactions oxidize (increasing the oxygen/carbon ratio in the molecules) and mineralize (transforming them to inorganic molecules, H 2 O, CO 2 , etc.) these contaminants. In this paper, we used the radiolysis of water to produce • OH and characterised the rate of oxidation and mineralization by the dose dependences of the Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) content values. Analysis of the dose dependences for 34 harmful organic compounds showed large differences in the oxidation and mineralization rates and these parameters are characteristic to the given group of chemicals. E.g., the rate of oxidation is relatively low for fluoroquinolone antibiotics; it is high for β-blocker medicines. Mineralization rates are low for both fluoroquinolones and β-blockers. The one-electron-oxidant • OH in most cases induces two - four-electron-oxidations. Most of the degradation takes place gradually, through several stable molecule intermediates. However, based on the results it is likely, that some part of the oxidation and mineralization takes place parallel. The organic radicals formed in • OH reactions react with several O 2 molecules and release several inorganic fragments during the radical life cycle., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The OH production by adding magnetite (MGT) alone has been reported in composting. However, the potential of nitrilotriacetic acid (NTA) addition for magnetite-amended sludge composting remained unclear. Three treatments with different addition [control check (CK); T1: 5 % MGT; T2: 5 % MGT + 5 % NTA] were investigated to characterize hydroxyl radical, humification and bacterial community response. The NTA addition manifested the best performance, with the peak OH content increase by 52 % through facilitating the cycle of Fe(Ⅱ)/Fe(Ⅲ). It led to the highest organic matters degradation (22.3 %) and humic acids content (36.1 g/kg). Furthermore, NTA addition altered bacterial community response, promoting relative abundances of iron-redox related genera, and amino acid metabolism but decreasing carbohydrate metabolism. Structural equation model indicated that temperature and Streptomyces were the primary factors affecting OH content. The study suggests that utilizing chelators is a promising strategy to strengthen humification in sewage sludge composting with adding iron-containing minerals., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

To solve the problem of unclear targeted inhibition of key free radicals by antioxidants, this paper took the hydroxyl radical with the highest oxidation activity of coal as the inhibition target and selected five antioxidants such as ethylene diamine tetraacetic acid, tea polyphenol, citric acid, vitamin C, and proanthocyanidins. Based on the theory of quantum chemistry, the characteristics and oxidation pathway of antioxidants inhibiting coal oxidation of hydroxyl radical were analyzed. Analyze the influence characteristics of antioxidants on the evolution of free radicals in coal through an electron paramagnetic resonance experiment (ESR). The results showed that the electron density of antioxidants was mainly distributed in the functional groups of carboxyl and hydroxyl, which played a key inhibitory role, and the vicinity of carboxyl and hydroxyl and other functional groups was positive potential, which was the active site of inhibiting hydroxyl radical. The order of inhibitory capacity of the five antioxidants was determined as GTP > PC > EDTA > CA > VC. It is concluded that the energy barrier of hydroxyl radical inhibition by citric acid is much lower than that of EDTA. For the hydrogen extraction reaction, VC inhibited the hydroxyl radical pathway with a higher energy barrier than the other three antioxidants. The mechanism of five antioxidants inhibiting •OH reaction was comprehensively analyzed. It was found that tea polyphenols have more active sites that can react with •OH to quench it, so the inhibition of tea polyphenols should be the most significant. When antioxidants inhibit coal spontaneous combustion, the type, complexity, concentration, and linewidth of free radicals in coal molecules are lower than those in raw coal, with GTP antioxidants having the best inhibitory effect. The research results have important theoretical and practical significance for revealing the mechanism of coal spontaneous combustion inhibition and developing directional coal spontaneous combustion inhibition technology., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Lingering inconsistencies in the global methane (CH 4 ) budget and ambiguity in CH 4 sources and sinks triggered efforts to identify new CH 4 formation pathways in natural ecosystems. Herein, we reported a novel mechanism of light-induced generation of hydroxyl radicals (•OH) that drove the production of CH 4 from aquatic dissolved organic matters (DOMs) under ambient conditions. A total of five DOM samples with different origins were applied to examine their potential in photo-methanification production under aerobic conditions, presenting a wide range of CH 4 production rates from 3.57 × 10 -3 to 5.90 × 10 -2 nmol CH 4 mg-C -1 h -1 . Experiments of •OH generator and scavenger indicated that the contribution of •OH to photo-methanificaiton among different DOM samples reached about 4∼42 %. In addition, Fourier transform infrared spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry showed that the carbohydrate- and lipid-like substances containing nitrogen-bonded methyl groups, methyl ester, acetyl groups, and ketones, were the potential precursors for light-induced CH 4 production. Based on the experimental results and simulated calculations, the contribution of photo-methanification of aquatic DOMs to the diffusive CH 4 flux across the water-air interface in a typical eutrophic shallow lake (e.g., Lake Chaohu) ranged from 0.1 % to 18.3 %. This study provides a new perspective on the pathways of CH 4 formation in aquatic ecosystems and a deeper understanding on the sources and sinks of global CH 4 ., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Tetracycline (TC) antibiotics, extensively utilized in livestock farming and aquaculture, pose significant environmental challenges. Photocatalysis, leveraging renewable sunlight and reusable photocatalysts, offers a promising avenue for mitigating TC pollution. However, identifying robust photocatalysts remains a formidable challenge. This study introduces a novel hollow-flower-ball-like nanoheterojunction composed of a nitrogen-rich covalent organic framework (N-COF) coupled with BiOBr (BOB), a semiconductor with a higher Fermi level. The synthesized N-COF/BOB S-scheme nanoheterojunction features an expanded contact interface, strengthened chemical bonding, and unique band topologies. The N-COF/BOB composites showcased exceptional TC degradation performance, achieving an 81.2% removal of 60 mg/L TC within 2 h, markedly surpassing the individual efficiencies of N-COF and BOB by factors of 3.80 and 5.96, respectively. Furthermore, the total organic carbon (TOC) removal efficiency highlights a superior mineralization capacity in the N-COF/BOB composite compared to the individual components, N-COF and BOB. The toxicity assessment revealed that the degradation intermediates possess diminished environmental toxicity. This enhanced performance is ascribed to the robust S-scheme nanoheterojunction structure, which promotes efficient photoinduced electron transfer from BOB to N-COF. This process also augments the separation of photogenerated charge carriers, resulting in an increased yield of superoxide radicals (∙O 2 - ) and hydroxyl radicals (∙OH). These reactive species significantly contribute to the degradation and mineralization of TC. Consequently, this study introduces a sustainable approach for addressing emerging antibiotic contaminants, employing COF-based photocatalysts., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Hydroxyl radical (•OH), a highly reactive oxygen species (ROS), is assumed as one of the most aggressive free radicals. This radical has a detrimental impact on cells as it can react with different biological substrates leading to pathophysiological disorders, including inflammation, mitochondrion dysfunction, and cancer. Quantification of this free radical in-situ plays critical roles in early diagnosis and treatment monitoring of various disorders, like macrophage polarization and tumor cell development. Luminescence analysis using responsive probes has been an emerging and reliable technique for in-situ detection of various cellular ROS, and some recently developed •OH responsive nanoprobes have confirmed the association with cancer development. This paper aims to summarize the recent advances in the characterization of •OH in living organisms using responsive nanoprobes, covering the production, the sources of •OH, and biological function, especially in the development of related diseases followed by the discussion of luminescence nanoprobes for •OH detection., (© 2024 The Authors. Chemistry - An Asian Journal published by Wiley-VCH GmbH.)

We report a novel impedimetric sensor based on a graphite electrode impregnated with polyethylene and paraffin under vacuum (IGE) modified with electrochemically deposited gold and a self-assembled monolayer of N-acetyl-L-cysteine (NAC/Au/IGE) for selective and sensitive determination of extracellular hydroxyl radicals (OH • ) generated by living cells. The application of a sulphur-containing molecule oxidized by OH • predicts the high selectivity of the sensor, and the utilization of the non-faradaic impedance spectroscopy for recording an analytical response makes it possible to achieve superior sensitivity with a detection limit of 0.01 nM and a linear dynamic range of 0.08-8 nM. Meanwhile, NAC/Au/IGE demonstrated a strong potential of detecting OH • generated by biological objects via successful determination of extracellular hydroxyl radicals generated by normal fibroblast cells and prostate carcinoma cells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Designing carbon materials with specific oxygen-containing functional groups is very attractive for the precise decoration of carbon electrode materials and the basic understanding of specific charge storage mechanisms, which contributes to the further development of high-performance carbon materials for energy storage and conversion applications. In this contribution, a hydroxyl-rich micropore-dominated porous carbon material was obtained by direct carbonization of cellulose. The content of oxygen atoms in hydroxyl form in the obtained carbon is nearly 6 at.%. With the pyrolysis temperature changed, the macroscopic morphology, the specific surface area, surface functional groups, and graphitization degree of the carbon materials were changed strongly. Besides, the carbon material obtained with a carbonization temperature of 900 °C (C9) showed enhanced specific capacitance in sulfuric acid, sodium hydroxide, and sodium sulfate aqueous electrolytes, which mainly originates from the contribution of pseudocapacitance. The pseudocapacitance mainly depends on the presence of surface hydroxyl functional groups. Besides, the pseudocapacitance value of C9 material in neutral electrolytes (151.34 F g -1 ) is about twice that in acidic (75.9 F g -1 ) and alkaline (75.78 F g -1 ) electrolytes., Competing Interests: Declaration of competing interest There are no conflicts to declare. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

In situ and real-time determination of hydroxyl radicals ( • OH) in physiological and pathological processes is a great challenge due to their ultrashort lifetime. Herein, an electrochemical method was developed by using dimethyl sulfoxide (DMSO) as a trapping probe for rapid determination of • OH in aqueous solution. When DMSO reacted with • OH, an intermediate product methane sulfinic acid (MSIA) was formed, which can be electrochemically oxidized to methanesulfonic acid (MSA) on the glassy carbon electrode (GCE), resulting in a distinct voltammetric signal that is directly proportional to the concentration of • OH. Other commonly encountered reactive oxygen species (ROS), including hypochlorite anions (ClO - ), superoxide anions (O 2 •- ), sulfate radicals (SO 4 •- ), and singlet oxygen ( 1 O 2 ), have showed no interference for • OH determination. Thus, an electrochemical method was developed for the determination of • OH, which exhibits a wide linear range (0.4-5120 μM) and a low limit detection of 0.13 μM (S/N = 3) and was successfully applied for the quantification of • OH in aqueous extracts of cigarette tar (ACT). Alternatively, the same reaction mechanism is also applicable for the determination of DMSO, in which a linear range of 40-320 μM and a detection limit 13.3 μM (S/N = 3) was achieved. The method was used for the evaluation of DMSO content in cell cryopreservation medium. This work demonstrated that DMSO can serve as an electrochemical probe and has valuable application potential in radical study, biological research, and environmental monitoring.

Photocatalytic oxidation has gained great interest in environmental remediation, but it is still limited by its low efficiency and catalytic deactivation in the degradation of aromatic VOCs. In this study, we concurrently regulated the surface hydroxyl and oxygen vacancies by introducing Al into ZnSn layered double hydroxide (LDH). The presence of distorted Al species induced local charge redistribution, leading to the remarkable formation of oxygen vacancies. These oxygen vacancies subsequently increased the amount of surface hydroxyl and elongated its bond length. The synergistic effects of surface hydroxyl and oxygen vacancies greatly enhanced reactant adsorption-activation and facilitated charge transfer to generate • OH, • O 2 - , and 1 O 2 , resulting in highly efficient oxidation and ring-opening of various aromatic VOCs. Compared with commercial TiO 2 , the optimized ZnSnAl-50 catalyst exhibited about 2-fold activity for the toluene and styrene degradation and 10-fold activity for the chlorobenzene degradation. Moreover, ZnSnAl-50 demonstrated exceptional stability in the photocatalytic oxidation of toluene under a wide humidity range of 0-75%. This work marvelously improves the photocatalytic efficiency, stability, and adaptability through a novel strategy of surface hydroxyl and oxygen vacancies engineering.

Pseudanabaena sp. and the odor compound it produces, 2-methylisoborneol (2-MIB), has been reportedly responsible for off-flavor pollution worldwide, leading to substandard drinking water sensory indicators and serious water supply crises. In this paper, the hydroxyl radical (•OH) produced by the synergistic effect of strong ionization discharge and hydrodynamic cavitation rapidly inactivated Pseudanabaena sp. and simultaneously mineralized 2-MIB to a concentration of 2.57 ng/L, which is below the odor threshold of 10 ng/L for a total reactive oxidants (TRO) concentration of 1.2 mg/L within 12 s. Crucially, the intracellular 2-MIB level was maintained in approximately 155.26- 162.29 ng/L range, indicating that 2-MIB was not released from the cells. Based on the scanning electron microscopy (SEM) results, the integrity of Pseudanabaena sp. cells was maintained with intact membranes and no intracellular organic matters (IOM) released during •OH inactivation. In contrast, ClO 2 caused severe membrane rupture and massive IOM release. Based on the gas chromatograph/mass spectrometer (GC/MS) analyses and mass spectral database, the chromatogram fitted the baseline with a TRO concentration of 4 mg/L and no peaks corresponding to intermediates were detected. Moreover, •OH could mineralize 2-MIB by opening the ring structures of 1,2,3,3-tetramethyl-4-cyclopentenone, neomenthol, and 2-methylcyclohexene-1-aldehyde to produce small-molecule compounds, finally leading to CO 2 and H 2 O formation via three reaction pathways. Therefore, the •OH not only maintained the cell integrity of Pseudanabaena sp. during inactivation but also mineralized 2-MIB simultaneously., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Phenolic compounds are industrially versatile chemicals, also the most ubiquitous pollutants. Recently, biosynthesis and biodegradation of phenols has attracted increasing attention, while phenols' toxicity is a major issue. Here, we evolved phloroglucinol-tolerant Escherichia coli strains via adaptive evolution, and three mutations (ΔsodB, ΔclpX and fetAB overexpression) prove of great assistance in the tolerance improvement. We discover that phloroglucinol complexes with iron and promotes the generation of hydroxyl radicals in Fenton reaction, which leads to reducing power depletion, lipid peroxidation, and ferroptosis-like cell death of E. coli. Besides phloroglucinol, various phenols can trigger ferroptosis-like death in diverse organisms, from bacteria to mammalian cells. Furthermore, repressing this ferroptosis-like death improves phloroglucinol production and phenol degradation by corresponding strains respectively, showing great application potential in microbial degradation or production of desired phenolic compounds, and phloroglucinol-induced ferroptosis suppresses tumor growth in mice, indicating phloroglucinol as a promising drug for cancer treatment., (© 2024. The Author(s).)

Free available chlorine has been and is being applied in global water treatment and readily reacts with dissolved organic matter (DOM) in aquatic environments, leading to the formation of chlorinated products. Chlorination enhances the photoreactivity of DOM, but the influence of chlorinated compounds on the photogeneration of hydroxyl radicals ( • OH) has remained unexplored. In this study, a range of chlorinated carboxylate-substituted phenolic model compounds were employed to assess their • OH photogeneration capabilities. These compounds demonstrated a substantial capacity for • OH production, exhibiting quantum yields of 0.1-5.9 × 10 -3 through direct photolysis under 305 nm and 0.2-9.5 × 10 -3 through a triplet sensitizer (4-benzoylbenzoic acid)-inducing reaction under 365 nm LED irradiation. Moreover, the chlorinated compounds exhibited higher light absorption and • OH quantum yields compared to those of their unchlorinated counterparts. The • OH photogeneration capacity of these compounds exhibited a positive correlation with their triplet state one-electron oxidation potentials. Molecular-level compositional analysis revealed that aromatic structures rich in hydroxyl and carboxyl groups (e.g., O/C > 0.5 with H/C < 1.5) within DOM serve as crucial sources of • OH, and chlorination of these compounds significantly enhances their capacity to generate • OH upon irradiation. This study provides novel insights into the enhanced photogeneration of • OH from chlorinated DOM, which is helpful for understanding the fate of trace pollutants in chlorinated waters.

Background: Concerning about the quality of room air has increased exponentially. Specially in dental clinics where diary practice is characterized by the important generation of aerosols., Material and Methods: An in vitro model was used in which samples were collected from the surfaces and room air of a dental clinic before and after the use of an OH˙ radical generator., Results: A total of 1260 samples were collected for bacteriological analysis and 14 samples for the detection of SARS-CoV-2. Following OH˙ treatment, the tested surface samples showed a decrease in the number of colony forming units (CFUs) of 76.9% in TSA culture medium. The circulating room air samples in turn showed a decrease in CFUs of 66.7% in Sabouraud medium and 71.4% in Mannitol agar medium. No presence of SARS-CoV-2 was observed on the surface of the face shield., Conclusions: The disinfectant technology based on the use of hydroxyl radicals (OH˙) is effective in reducing the presence of moulds and yeasts and Staphylococcus in the air, and in reducing total aerobic bacteria on the tested surfaces.

The review considers the problem of hydrogen peroxide decomposition and hydroxyl radical formation in the presence of iron in vivo and in vitro. Analysis of the literature data allows us to conclude that, under physiological conditions, transport of iron, carried out with the help of carrier proteins, minimizes the possibility of appearance of free iron ions in cytoplasm of the cell. Under pathological conditions, when the process of transferring an iron ion from a donor protein to an acceptor protein can be disrupted due to modifications of the carrier proteins, iron ions can enter cytosol. However, at pH values close to neutral, which is typical for cytosol, iron ions are converted into water-insoluble hydroxides. This makes it impossible to decompose hydrogen peroxide according to the mechanism of the classical Fenton reaction. A similar situation is observed in vitro, since buffers with pH close to neutral are used to simulate free radical oxidation. At the same time, iron hydroxides are able to catalyze decomposition of hydrogen peroxide with formation of a hydroxyl radical. Decomposition of hydrogen peroxide with iron hydroxides is called Fenton-like reaction. Studying the features of Fenton-like reaction in biological systems is the subject of future research.

Pyrite is widely distributed in estuarine sediments as an inexpensive natural Fenton-like reagent, however, the mechanism on the hydroxyl radical (HO · ) production by pyrite under estuarine environmental conditions is still poorly understood. The batch experiments were performed to investigate the effects of estuarine conditions including aging (in air, in water), seawater anions (Cl - , Br - and HCO 3 - ) and light on the HO · production by pyrite oxidation. The one-electron transfer dominated the process from O 2 to HO · induced by oxidation of pyrite. The Fe (oxyhydr)oxide coatings on the surface of pyrite aged in air and water consumed hydrogen peroxide while mediating the electron transfer, and the combined effect of the two resulted in a suppression of HO · production in the early stage of aging and a promotion of HO · production in the later stage of aging. Corrosion of the surface oxide layers by aggressive anions was the main reason for the inhibition of HO · production by Cl - and Br - , and the generation of Cl · and Br · may also play a role in the scavenging of HO · . HCO 3 - increased the average rate of HO · production through surface-CO 2 complexes formed by adsorption on the surface of pyrite. The significant enhancement of HO · production under light was attributed to the formation of photoelectrons induced by photochemical reactions on pyrite and its surface oxide layers. These findings provide new insights into the environmental chemical behavior of pyrite in the estuary and enrich the understanding of natural remediation of estuarine environments., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article., (Copyright © 2023. Published by Elsevier B.V.)

This study closely examines the environmental fate of 4-ethylphenol (4-EP), a significant byproduct of biomass combustion. We employed quantum chemical calculations to investigate the reaction mechanism, kinetics, and ecotoxicity of 4-EP initiated by OH radicals in various environments (aqueous, atmospheric liquid, atmospheric and inhomogeneous phases). Our findings highlight that solvent effects contribute to a higher OH-addition reaction branching ratio (Γ add ) of 0.68 for 4-EP in an aqueous solution, compared to 0.26 in the gas-phase environment and 0.22 in the inhomogeneous environment at 298 K. We determined the rate constants for the liquid-phase, gas-phase, and nonhomogeneous phase to be 1.14 × 10 9  s -1  M -1 , 3.09 × 10 9  s -1  M -1 , and 6.19 × 10 14  s -1  M -1 , respectively. Notably, the adsorption of mineral particles considerably enhances the reaction rate of 4-EP with OH radicals. 4-ethylbenzene-1,2-diol, 4-hydroxycyclohexa-3,5-diene-1,2-dione, 1-ethyl-6-methyl-6H-benzo(c)chromene-4,9-diol, 5-ethyl-6'-(1-hydroxyethyl)-(1,1'-biphenyl)-2,3,3'-triol and 2-ethyl-4,6,9-trimethyl-6H-benzo(c) chromene are major products in both gas-phase and liquid-phase reactions, and (2Z, 4Z)-4-ethyl-6-oxohexa-2,4-dienoic acid is also one of the major products in gas-phase reactions. Toxicological predictions indicate that the ecotoxicity of 4-ethyl-6-methyl-6H-benzo(c)chromene-1,9-diol, 2-ethyl-6-methyl-6H-benzo(c)chromene-3,9-diol, and 2-ethyl-4,6,9-trimethyl-6H-benzo(c) chromene surpassed that of 4-EP. However, the toxicity of the reaction products is reduced in the presence of NO x . This investigation provides an exhaustive theoretical foundation for comprehending the degradation behavior of 4-EP and underscores the need to consider various environmental factors in assessing the potential risk of biomass combustion by products., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

It is difficult to achieve deep dehalogenation or mineralization for halogenated antibiotics using traditional reduction or oxidation processes, posing the risk of microbial activity inhibition and bacterial resistance. Herein, an efficient electrocatalytic process coupling atomic hydrogen (H*) reduction with hydroxyl radical (•OH) oxidation on a bifunctional cathode catalyst is developed for the deep dehalogenation and mineralization of florfenicol (FLO). Atomically dispersed NiFe bimetallic catalyst on nitrogen-doped carbon as a bifunctional cathode catalyst can simultaneously generate H* and •OH through H 2 O/H + reduction and O 2 reduction, respectively. The H* performs nucleophilic hydro-dehalogenation, and the •OH performs electrophilic oxidization of the carbon skeleton. The experimental results and theoretical calculations indicate that reductive dehalogenation and oxidative mineralization processes can promote each other mutually, showing an effect of 1 + 1 > 2. 100% removal, 100% dechlorination, 70.8% defluorination, and 65.1% total organic carbon removal for FLO are achieved within 20 min ( C 0 = 20 mg·L -1 , -0.5 V vs SCE, pH 7). The relative abundance of the FLO resistance gene can be significantly reduced in the subsequent biodegradation system. This study demonstrates that the synergy of reduction dehalogenation and oxidation degradation can achieve the deep removal of refractory halogenated organic contaminants.

Mackinawite (FeS) has gained increasing interest due to its potential application in contaminant removal by either reduction or oxidation processes. This study further demonstrated the efficiency of FeS in degrading nitrobenzene (ArNO 2 ) via a sequential two-step reduction and oxidation process under neutral conditions. In the reduction stage, FeS rapidly reduced ArNO 2 to aniline (ArNH 2 ), with nitrosobenzene (ArNO) and phenylhydroxylamine (ArNHOH) serving as the intermediates. X-ray photoelectron spectroscopy (XPS) analysis indicated that both Fe(II) and S(II) in FeS contributed electrons to the reduction of ArNO 2 . In the subsequent oxidation stage with oxygen, by addition of 0.5 mM tripolyphosphate (TPP), ArNH 2 generated in the reduction process could be effectively oxidized to aminophenols by hydroxyl radicals ( • OH), which would undergo eventual mineralization via ring-cleavage reactions. TPP exerted a favorable role in enhancing • OH production for ArNH 2 degradation by promoting the formation of the dissolved Fe(II)-TPP complex, thus enhancing the homogeneous Fenton reaction. Additionally, TPP adsorption inhibited the surface oxidation reactivity of FeS due to the change of Fe(II) coordination. Finally, the effective degradation of ArNO 2 by FeS in actual groundwater was demonstrated by using this sequential reduction and oxidation approach. These research findings provide a theoretical basis for a new FeS-based remediation approach, offering an alternative way for comprehensive removal of ArNO 2 .

Ferryl ion ([Fe IV O] 2+ ) has often been suggested to play a role in iron-based advanced oxidation processes (AOPs) with its presence commonly determined using the unique oxidation pathway from methyl phenyl sulfoxide (PMSO) to methyl phenyl sulfone (PMSO 2 ). However, we show here that the oxidation products of PMSO, formed on reaction with hydroxyl radical, enhance PMSO 2 formation as a result of their complexation with Fe(III) leading to the changes in the reactivity of Fe(III) species in the homogeneous Fenton reaction. As such, PMSO should be used with caution to investigate the role of [Fe IV O] 2+ in iron-based AOPs with these insights suggesting the need to reassess the findings of many previous studies in which this reagent was used. The other common target compounds, phthalhydrazide and hydroxybenzoic acids, were also found to modify the rate and extent of iron cycling as a result of complexation and/or redox reactions, either by the probe compound itself and/or oxidation products formed. Overall, this study highlights that these confounding effects of the aromatic probe compounds on the reactivity of iron species should be recognized if reliable mechanistic insights into iron-based AOPs are to be obtained.

The use of Advance Oxidation Process (AOPs) has been extensively examined in order to eradicate organic pollutants. This review assesses the efficacy of photolysis, O 3 based (O 3 /UV, O 3 /H 2 O 2 , O 3 /H 2 O 2 /UV, H 2 O 2 /UV, Fenton, Fenton-like, hetero-system) and sonochemical and electro-oxidative AOPs in this regard. The main purpose of this review and some suggestions for the advancement of AOPs is to facilitate the elimination of toxic organic pollutants. Initially proposed for the purification of drinking water in 1980, AOPs have since been employed for various wastewater treatments. AOPs technologies are essentially a process intensification through the use of hybrid methods for wastewater treatment, which generate large amounts of hydroxyl (•OH) and sulfate (SO4·-) radicals, the ultimate oxidants for the remediation of organic pollutants. This review covers the use of AOPs and ozone or UV treatment in combination to create a powerful method of wastewater treatment. This novel approach has been demonstrated to be highly effective, with the acceleration of the oxidation process through Fenton reaction and photocatalytic oxidation technologies. It is clear that Advance Oxidation Process are a helpful for the degradation of organic toxic compounds. Additionally, other processes such as •OH and SO4·- radical-based oxidation may also arise during AOPs treatment and contribute to the reduction of target organic pollutants. This review summarizes the current development of AOPs treatment of wastewater organic pollutants., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Surface antibacterial coatings with outstanding antibacterial efficiency have attracted increasing attention in medical protective clothing and cotton surgical clothing. Although nanozymes, as a new generation of antibiotics, are used to combat bacteria, their catalytic performance remains far from satisfactory as alternatives to natural enzymes. Single-atom nanodots provide a solution to the low catalytic activity bottleneck of nanozymes. Here, atomically thin C 3 N 4 nanodots supported single Cu atom nanozymes (Cu-CNNDs) are developed by a self-tailoring approach, which exhibits catalytic efficiency of 8.09 × 10 5 M -1 s -1 , similar to that of natural enzyme. Experimental and theoretical calculations show that excellent peroxidase-like activity stems from the size effect of carrier optimizing the coordination structure, leading to full exposure of Cu-N 3 active site, which improves the ability of H 2 O 2 to generate hydroxyl radicals (•OH). Notably, Cu-CNNDs exhibit over 99% superior antibacterial efficacy and are successfully grafted onto cotton fabrics. Thus, Cu-CNNDs blaze an avenue for exquisite biomimetic nanozyme design and have great potential applications in antibacterial textiles., (© 2023 Wiley-VCH GmbH.)

This study used experimental and computational analysis to investigate the advanced oxidation of bisphenol A (BPA) and 2,4-dinitroanisole (DNAN). The pseudo first-order reaction rate constants depended on the molar peroxide ratio and were between 0.13 and 0.28 min -1 for BPA and between 0.018 and 0.032 min -1 for DNAN. The kinetic differences appear to be due in part to the energy requirements for oxidation, which depended on the reaction mechanism but were typically lower for BPA than they were for DNAN. Density functional theory (DFT) was used to develop transformation pathways that included experimentally-detected byproducts. The most energetically favored pathway for BPA oxidation begins with the formation of hydroxylated derivatives, while for DNAN, the most energetically favorable degradation pathway begins with the substitution of the methoxy group. Overall, these findings demonstrate the power of combining experimental and computational tools to reveal transformation mechanisms during water treatment. PRACTITIONER POINTS: Advanced oxidation transformations for two emerging water pollutants, bisphenol A and dinitroanisole, was investigated. The observed reaction kinetics depended on molar peroxide ratio in a manner that is in keeping with previous findings. Density functional theory-based analysis revealed reaction energy requirements and degradation pathways., (Published 2023. This article is a U.S. Government work and is in the public domain in the USA.)

Iron(II) species can participate in the Fenton and Fenton-like reactions to generate the hydroxyl radical that can oxidatively damage biomolecules and induce oxidative stress in biological systems. Many diseases, including neurodegeneration, cardiovascular disease and cancer, are associated with oxidative stress. However, it is proposed recently that hydroxyl radical would not be generated from the Fenton reaction under physiological conditions and thus would not cause oxidative stress in biological systems. This proposal may cause confusion for understanding oxidative stress and can also have impact on therapeutic strategies for the diseases associated with oxidative stress. In this Mini-review, the up-to-date convincing evidences of hydroxyl radical generation from the physiologically relevant Fenton-like reactions of the iron(II) complexes with physiological ligands in human blood plasma, including histidine, citrate and phosphate, are succinctly reviewed. The oxidative damages caused by hydroxyl radical to biomolecules and cells are briefly summarized. These findings strongly challenge the above proposal., Competing Interests: Declaration of competing interest The author declares no competing interest., (Copyright © 2023 Elsevier Inc. All rights reserved.)

In this study, chrysin (Chr), baicalein (Bai), apigenin (Api) and galangin (Gal) were selected as the representative flavonoids with different position of phenolic hydroxyl groups, and edible dock protein (EDP) was used as a material to construct delivery system. Subsequently, the molecular interactions and functional properties of flavonoids-loaded EDP nanomicelles were investigated. Results exhibited that hydrogen bond, hydrophobic interaction and van der Waals force were the main driving forces for self-assembly of flavonoids and EDP molecules. Meanwhile, this self-assembly remarkably enhance the storage and digestion stability of flavonoid compounds. Among four flavonoids, the order of loading ability was: Api > Gal > Bai > Chr. Herein, Api had a largest loading capacity (6.74%) because of its active phenolic hydroxyl group in ring B. These results suggested that the position of phenolic hydroxyl groups in flavonoids is a key factor to regulate its self-assembly with protein molecules., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

We examined the reaction of hydroxyl radicals (HO • ) and sulfate radical anions (SO 4 •- ), which is generated by ionizing radiation in aqueous solutions under anoxic conditions, with an alternating GC doubled-stranded oligodeoxynucleotide (ds-ODN), i.e., the palindromic 5'-d(GCGCGC)-3'. In particular, the optical spectra of the intermediate species and associated kinetic data in the range of ns to ms were obtained via pulse radiolysis. Computational studies by means of density functional theory (DFT) for structural and time-dependent DFT for spectroscopic features were performed on 5'-d(GCGC)-3'. Comprehensively, our results suggest the addition of HO • to the G:C pair moiety, affording the [8-HO-G:C] • detectable adduct. The previous reported spectra of one-electron oxidation of a variety of ds-ODN were assigned to [G(-H + ):C] • after deprotonation. Regarding 5'-d(GCGCGC)-3' ds-ODN, the spectrum at 800 ns has a completely different spectral shape and kinetic behavior. By means of calculations, we assigned the species to [G:C/C:G] •+ , in which the electron hole is predicted to be delocalized on the two stacked base pairs. This transient species was further hydrated to afford the [8-HO-G:C] • detectable adduct. These remarkable findings suggest that the double-stranded alternating GC sequences allow for a new type of electron hole stabilization via delocalization over the whole sequence or part of it.

Effective photodynamic therapy (PDT) requires photosensitizers (PSs) to massively generate type I reactive oxygen species (ROS) in a less oxygen-dependent manner in the hypoxia tumor microenvironment. Herein, we present a cascade strategy to boost type I ROS, especially hydroxyl radical (OH· - ), generation with an aggregation-induced emission (AIE) photosensitizer-albumin complex for hypoxia-tolerant PDT. The cationic AIE PS TPAQ-Py-PF 6 (TPA = triphenylamine, Q = anthraquinone, Py = pyridine) contains three important moieties to cooperatively enhance free radical generation: the AIE-active TPA unit ensures the effective triplet exciton generation in aggregate, the anthraquinone moiety possesses the redox cycling ability to promote electron transfer, while the cationic methylpyridinium cation further increases intramolecular charge transfer and electron separation processes. Inserting the cationic TPAQ-Py-PF 6 into the hydrophobic domain of bovine serum albumin nanoparticles (BSA NPs) could greatly immobilize its molecular geometry to further increase triplet exciton generation, while the electron-rich microenvironment of BSA ultimately leads to OH· - generation. Both experimental and theoretical results confirm the effectiveness of our molecular cationization and BSA immobilization cascade strategy for enhancing OH· - generation. In vitro and in vivo experiments validate the excellent antitumor PDT performance of BSA NPs, superior to the conventional polymeric encapsulation approach. Such a multidimensional cascade strategy for specially boosting OH· - generation shall hold great potential in hypoxia-tolerant PDT and related antitumor applications.

Hydroxyl radical protein footprinting (HRPF) using synchrotron radiation is a well-validated method to assess protein structure in the native solution state. In this method, X-ray radiolysis of water generates hydroxyl radicals that can react with solvent accessible side chains of proteins, with mass spectrometry used to detect the resulting labeled products. An ideal footprinting dose provides sufficient labeling to measure the structure but not so much as to influence the results. The optimization of hydroxyl radical dose is typically performed using an indirect Alexa488 fluorescence assay sensitive to hydroxyl radical concentration, but full evaluation of the experiment's outcome relies upon bottom-up liquid chromatography mass spectrometry (LC-MS) measurements to directly determine sites and extent of oxidative labeling at the peptide and protein level. A direct evaluation of the extent of labeling to provide direct and absolute measurements of dose and "safe" dose ranges in terms of, for example, average numbers of labels per protein, would provide immediate feedback on experimental outcomes prior to embarking on detailed LC-MS analyses. To this end, we describe an approach to integrate intact MS screening of labeled samples immediately following exposure, along with metrics to quantify the extent of observed labeling from the intact mass spectra. Intact MS results on the model protein lysozyme were evaluated in the context of Alexa488 assay results and a bottom-up LC-MS analysis of the same samples. This approach provides a basis for placing delivered hydroxyl radical dose metrics on firmer technical grounds for synchrotron X-ray footprinting of proteins, with explicit parameters to increase the likelihood of a productive experimental outcome. Further, the method directs approaches to provide absolute and direct dosimetry for all types of labeling for protein footprinting., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Mark R. Chance is Founder and Chief Scientific Officer of NeoProteomics, which provides access to footprinting technologies and services. Janna Kiselar is a consultant for NeoProteomics., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Periodate (PI) as an oxidant has been extensively studied for organic foulants removal in advanced oxidation processes. Here PI was introduced into In 2 O 3 /Vis-LED process to enhance the formation of ·OH for promoting the degradation of organic foulants. Results showed that the addition of PI would significantly promote the removal of sulfamethoxazole (SMX) in the In 2 O 3 /Vis-LED process (from 9.26% to 100%), and ·OH was proved to be the dominant species in the system. Besides, the process exhibited non-selectivity in the removal of different organic foulants. Comparatively, various oxidants (e.g., peroxymonosulfate, peroxydisulfate, and hydrogen peroxide) did not markedly promote the removal of SMX in the In 2 O 3 /Vis-LED process. Electrochemical analyses demonstrated that PI could effectively receive photoelectrons, thus inhibiting the recombination of photogenerated electron-hole (e - /h + ) pairs. The holes then oxidized the adsorbed H 2 O to generate ·OH, and the PI converted to iodate at the same time. Additionally, the removal rate of SMX reduced from 100% to 17.2% as Vis-LED wavelengths increased from 440 to 560 nm, because of the low energy of photons produced at longer wavelengths. Notably, the species of PI do not affect its ability to accept electrons, resulting in the degradation efficiency of SMX irrespective of pH (4.0-10.0). The coexistence of inorganic cations and anions (such as Cl - , CO 3 2- /HCO 3 - , SO 4 2- , Ca 2+ , and Mg 2+ ) also had an insignificant effect on SMX degradation. Furthermore, the process also showed excellent degradation potential in real water. The proposed strategy provides a new insight for visible light-catalyzed activation of PI and guidance to explore green catalytic processes for high-efficiency removal of various organic foulants., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

FeOCl is a highly effective candidate material for advanced oxidation process (AOP) catalysts, but there remain enormous uncertainties about the essence of its outstanding activity. Herein, we clearly elucidate the mechanism involved in the FeOCl-catalyzed perdisulfate (PDS) activation, and the role of surface hydroxyls in bridging the electron transfer between Fe sites and PDS onto the FeOCl/H 2 O interface is highlighted. ATR-FTIR and Raman analyses reveal that phosphate could suppress the activity of FeOCl via substituting its surface hydroxyls, demonstrating the essential role of hydroxyl in PDS activation. By the use of X-ray absorption fine structure and density functional theory calculations, we found that the polar surface of FeOCl experienced prominent hydrolyzation, which enriched abundant electrons within the microarea around the Fe site, leading to a stronger attraction between FeOCl and PDS. As a result, PDS adsorption onto the FeOCl/H 2 O interface was obviously enhanced, the bond length of O-O in adsorbed PDS was lengthened, and the electron transfer from Fe atoms to O-O was also promoted. This work proposed a new strategy for PDS-based AOP development and a hint of building efficient heterogeneous AOP catalysts via regulating the hydroxylation of active sites.

Green energy from the surrounding environment has great potential for reducing environmental pollution and sustainable development. Triboelectric nanogenerators (TENGs) are of great interest as they can easily harvest mechanical energy from the environment. Here, we present a triboelectric nanogenerator (RS-TENG) based on rape straw (RS), which was developed from a film composed of waste RS and polyvinyl alcohol (PVA). Due to the high content of carbonyl, hydroxyl and amino acid functional groups in RS, the ability of RS/PVA to lose electrons is increased. The proposed RS-TENG device with a size of 6.25 cm 2 exhibits open circuit voltage (78 V), short circuit current (5.3 μ A) performance under uniform external stress at a frequency of 3.5 Hz and 10 N in the cylinder motor. 104.5 μ W was obtained with a load resistance of 25 MΩ. Results obtained from degradability tests revealed that the RS/PVA film was able to degrade over a period of 30 d (In PBS solution). The RS-TENG produces a significantly high current signal under conditions of finger bending, elbow movements, and foot tapping. Practical tests of the RS-TENG have shown that it is a promising sensing device that will be widely used in the future., (© 2023 IOP Publishing Ltd.)

Regulation of the free radical types is crucial but challenging in the ubiquitous heterogeneous catalytic oxidation for chemosynthesis, biotherapy, and environmental remediation. Here, using aromatic pollutant (AP) removal as a prototype, we identify the massive accumulation of the benzoquinone (BQ) intermediate in the hydroxyl radical ( • OH)-mediated AP degradation process. Theoretical prediction and experiments demonstrate that BQ is both a Lewis acid and base because of its unique molecular and electronic structure caused by the existence of symmetrical carbonyl groups; therefore, it is hard to be electrophilically added by oxidizing • OH as a result of the high reaction energy barrier (Δ G = 1.74 eV). Fortunately, the introduction of the superoxide anion ( • O 2 - ) significantly lowers the conversion barrier (Δ G = 0.91 eV) of BQ because • O 2 - can act as the electron donor and acceptor simultaneously, electrophilically and nucleophilically add to BQ synchronously, and break it down. Subsequently, the breakdown products can then be further oxidized by • OH until completely mineralized. Such synergistic oxidation based on • OH and • O 2 - timely eliminates BQ, potentiates AP mineralization, and inhibits electrode fouling caused by high-resistance polymeric BQ; more importantly, it effectively reduces toxicity, saves energy and costs, and decreases the environmental footprint, evidenced by the life cycle assessment.

Due to the emergence of drug resistance in bacteria and biofilm protection, achieving a satisfactory therapeutic effect for bacteria-infected open wounds with conventional measures is problematic. Here, a photothermal cascade nano-reactor (CPNC@GOx-Fe 2+ ) is constructed through a supramolecular strategy through hydrogen bonding and coordination interactions between chitosan-modified palladium nano-cube (CPNC), glucose oxidase (GOx), and ferrous iron (Fe 2+ ). CPNC@GOx-Fe 2+ exhibits excellent photothermal effects and powers the GOx-assisted cascade reaction to generate hydroxyl radicals, enabling photothermal and chemodynamic combination therapy against bacteria and biofilms. Further proteomics, metabolomics, and all-atom simulation results indicate that the damage of the hydroxyl radical to the function and structure of the cell membrane and the thermal effect enhance the fluidity and inhomogeneity of the bacterial cell membrane, resulting in the synergistic antibacterial effect. In the biofilm-associated tooth extraction wound model, the hydroxyl radical generated from the cascade reaction process can initiate the radical polymerization process to form a hydrogel in situ for wound protection. In vivo experiments confirm that synergistic antibacterial and wound protection can accelerate the healing of infected tooth-extraction wounds without affecting the oral commensal microbiota. This study provides a way to propose a multifunctional supramolecular system for the treatment of open wound infection., (© 2023 Wiley-VCH GmbH.)

Tetraphenylethene derivatives (TPEs) are used as luminescence probes for the detection of metal ions and biomolecules. These sensors function by monitoring the increase in the photoluminescence (PL) intensity of the TPEs resulting from aggregation-induced emission (AIE) upon interaction with the analytes. The AIE behavior of the sensors was investigated by measuring their PL. In this study, PL, PL lifetime, and confocal laser scanning microscopy measurements were carried out as part of our in-depth investigation of AIE behavior of TPEs for the detection of biomolecules and radical species. We used 1,1,2,2-tetrakis(4-((trimethylammonium)alkoxy)phenyl)tetraphenylethene tetrabromide (TPE-C( m )N + Me 3 Br - , m = 2, 4, and 6, where m denotes the number of methylene groups in the alkyl chain) and TPE-C( m )N + Me 3 TCNQ -• (TCNQ -• is the 7,7',8,8'-tetracyanoquinodimethane anion radical) as luminescent probes for the detection of bovine serum albumin (BSA), DNA, and the hydroxyl radical ( • OH) generated from Fenton's reagent. The sensing performance of TPE-C( m )N + Me 3 Br - for BSA and DNA was found to depend on the length of the alkyl chains ( m ). UV-vis and PL measurements revealed that the responses of TPE-C( m )N + Me 3 Br - and TPE-C(4)N + TCNQ -• to Fenton's reagent depended on the solvent. The electrochemical properties of the TPE derivatives prepared in this study were additionally investigated via cyclic voltammetry.

This work addresses two research topics: the first concerns the specific/sensitive trapping of hydroxyl radicals ( • OH), and the second concerns the efficacy of encapsulating natural antioxidants, potentially lengthening their preservation activity. For context, nano-titania was solar-irradiated to produce • OH, which was spectrofluorimetrically assessed, based on the selective aromatic hydroxylation of the non-fluorescent sodium terephthalate to 2-hydroxyterephthalate fluorophore. Fluorescence intensity is proportional to generated • OH. Thus, a simple/rapid indirect method was utilized to assess • OH precisely. Accordingly, novel photoluminescent system is outlined in order to assess the scavenging potentiality of • OH in date seed oil (DSO) in both its pure and encapsulated formulations (ECP-DSO), i.e., when fresh and 5 months after extraction and encapsulation, respectively. With the addition of 80 μg/mL DSO or ECP-DSO, the efficacy of • OH scavenging amounted to 25.12 and 63.39%, which increased to 68.65 and 92.72% when 200 μg/mL DSO or ECP-DSO, respectively, was added. Moreover, the IC50 of DSO and ECP-DSO is 136.6 and 62.1 µg/mL, respectively. Furthermore, DSO and ECP-DSO decreased the kinetics for producing • OH by ≈20 and 40%, respectively, relative to • OH generated in the absence of antioxidant. This demonstrates the benefits of encapsulation on the preservation activity of natural antioxidants, even after five months after extraction, in terms of its interesting activity when compared to synthetic antioxidants. The developed fluorimetric • OH probing upgrades antioxidant medicines, thus paving the way for theoretical/practical insights on mechanistic hydroxyl radical-damaging biology.

As an anticonvulsant, oxcarbazepine (OXC) has attracted considerable attention for its potential threat to aquatic organisms. Density functional theory has been used to study the mechanisms and kinetics of OXC degradation initiated by OH radicals in aqueous environment. A total of fourteen OH-addition pathways were investigated, and the addition to the C8 position of the right benzene ring was the most vulnerable pathway, resulting in the intermediate IM8. The H-abstraction reactions initiated by OH radicals were also explored, where the extraction site of the methylene group (C14) on the seven-member carbon heterocyclic ring was found to be the optimal path. The calculations show that the total rate constant of OXC with OH radicals is 9.47 × 10 9 (mol/L) -1 sec -1 , and the half-life time is 7.32 s at 298 K with the [·OH] of 10 -11 mol/L. Moreover, the branch ratio values revealed that OH-addition (89.58%) shows more advantageous than H-abstraction (10.42%). To further understand the potential eco-toxicity of OXC and its transformation products to aquatic organisms, acute toxicity and chronic toxicity were evaluated using ECOSAR software. The toxicity assessment revealed that most degradation products such as OXC-2OH, OXC-4OH, OXC-1O-1OOH, and OXC-1OH' are innoxious to fish and daphnia. Conversely, green algae are more sensitive to these compounds. This study can provide an extensive investigation into the degradation of OXC by OH radicals and enrich the understanding of the aquatic oxidation processes of pharmaceuticals and personal care products (PPCPs)., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier B.V.)

Density functional theory (DFT) calculations at the M06-2X/def2-TZVP level have been employed to investigate the atmospheric oxidation mechanism of anthracene (ANT) initiated by HO • . Direct hydrogen atom abstraction from the ANT using HO • takes place hardly at ambient conditions while addition of HO • to the C1, C2, and C4 sites are thermodynamically and kinetically more advantageous. The addition reactions are controlled by the aromaticity and the kinetic trends were justified by resonance stabilization energies. The rate constants were calculated by using the Rice-Ramsperger-Kassel-Marcus (RRKM) and canonical transition state theory (CTST) methods in conjugation with zero curvature tunneling (ZCT). The overall RRKM-bimolecular rate constant at ambient conditions is 6.72 × 10 -12  cm 3 molecule -1 s -1 , is negatively dependent on the temperature and can be expressed as k 250-350 1bar =3.92×10 -14 exp(1534.9T). Contribution of the AD-C4 path in the overall reaction is about 70-80%, implying that the dependence of overall rate constant on pressure can be ignored. The kinetic data exhibit that the ANT is degraded during its long-range transport in the atmosphere and cannot be classified as persistent organic pollutants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Reduced iron-containing clay (RIC) minerals have been documented to exhibit antibacterial activity through a synergistic action of extracellular membrane attack and intracellular oxidation of cellular components. However, the relative importance between extracellular and intracellular processes has remained elusive. Here, metal-chelating organic ligands (lactate, oxalate, citrate, and ethylene diaminetetraacetic acid (EDTA)) were amended to the bactericidal assays such that the importance of the two processes could be evaluated. Reduced nontronite (rNAu-2) was used as a model clay mineral to produce extracellular hydroxyl radical ( • OH) upon oxygenation. The presence of Fe-chelating ligands increased • OH yield by 3-5 times. Consequently, bacterial cell membrane attack was enhanced, yet the antibacterial activity of RIC diminished. Additional experiments revealed that the ligands inhibited soluble metal ions from adsorption onto the bacterial cell membrane and/or penetration into the cytoplasm. Consequently, intracellular Fe concentration for the ligand-treated group was nearly 2 orders of magnitude lower than that for no-ligand control, which greatly decreased intracellular accumulation of reactive oxygen species (ROS) and increased cell survival. These results highlight that destruction of intracellular contents (proteins and DNA) is more important than oxidative degradation of membrane lipids and cell envelope proteins in causing bacterial cell death by RIC.

We report the synthesis of hydroxyl-radical (˙OH) responsive fluorescent probes that utilise the 3,5-dihydroxybenzyl (DHB) functionality. 4-Methylumbeliferone-DHB (Umb-DHB) and resorufin-DHB (Res-DHB) in the presence of ˙OH radicals resulted in significant increases in their respective fluorescent emission intensities at 460 nm and 585 nm. The incubation of Res-DHB in HeLa cells followed by therapeutic ultrasound (1 MHz) resulted in a significant increase in fluorescence emission intensity thus permitting the ability to monitor ultrasound-induced ˙OH production in live cells.

Sulfoxaflor is one of the widely used insecticides in agricultural lands to protect crops from insects. Due to its persistent nature, sulfoxaflor is identified as an environmental pollutant. In the present work, the mechanism and kinetics of sulfoxaflor degradation initiated by OH radical addition reaction are studied by using quantum chemical calculations. In the gas phase, the OH addition reaction at the C4 position of sulfoxaflor is found to be the favorable reaction pathway. The rate constant for the initial OH-addition reaction has been studied using canonical variational transition state theory (CVT) over the temperature range of 200-350 K. The initially formed sulfoxaflor-OH adduct intermediate transforms by reacting with O 2 , H 2 O, HO 2 , and NO x (x = 1-2) radicals. The excited-state calculation performed for the stationary points shows that the intermediates formed along the reaction pathway are easily photolyzed in normal sunlight. The toxicity assessment result shows that sulfoxaflor and few of its degradation products are harmful and toxic. The acidification potential of sulfoxaflor was found to be one, which shows its contribution to acid rain. This study gives an in-depth understanding of the mechanism, kinetics, and risk assessment of sulfoxaflor in the environment and aquatic system., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In the present study, novel copper-doped zirconium-based MOF (UIO-66) and copper-doped iron-based UIO-66 catalysts were prepared by hydrothermal synthesis method to improve the removal performance of gaseous benzene. The characteristics of the catalysts were analyzed by means of XRD, SEM, XPS, BET, and EPR. The copper loading catalyst had high crystallinity and irregular globular. The three kinds of catalysts with different Cu/Fe ratios had regular cubic shape. Compared with the catalyst supported with single copper, the bimetal Cu/Fe modification had a certain adjustment effect on the morphology, which specifically reflected in the uniform size and shape of catalyst particles with better dispersibility. The factors of different metal loading, dose of H 2 O 2 , and reaction temperature on benzene removal have been studied. It has been observed that in heterogeneous advanced oxidation removal of benzene, 3-Cu@UIO-66 and Cu 1.5 /Fe 1.5 @UIO-66 achieved the highest benzene removal efficiency of 81.2% and 94.6%, respectively. EPR results showed that the increase of Cu loading and different Cu/Fe ratios promoted the yield of hydroxyl radicals, thus promoted the benzene removal efficiency. The efficiency of heterogeneous oxidation removal of benzene first increased and then decreased with the increase of temperature due to H 2 O 2 instability. DFT calculations exhibited that the Fe oct -Cu-O site was a more effective activation site than the single Fe oct -O site. Dissociative adsorption occurred with the O-O bond of H 2 O 2 cracked, and the formed hydroxyls parallel adsorbed on the benzene surface. The combination of benzene and hydroxyls was strong chemisorption with the torsion angle of benzene ring obviously turned. The work was of great importance for identifying the roles of the novel catalyst for the removal of benzene pollutant from waste gases., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Lipids represent a large family of compounds with highly diverse structures that are involved in complex biological processes. A photocatalytic technique of on-tissue epoxidation of C=C double bonds has been developed for in situ mass spectrometric identification and spatial imaging of positional isomers of lipids. It is based on the plasmonic hot-electron transfer from irradiated gold nanowires to redox-active organic matrix compounds that undergo bond cleavages and generate hydroxyl radicals in nanoseconds. Intermediate radical anions and negative fragment ions have been unambiguously identified. Under the irradiation of a pulsed laser of the third harmonic of Nd 3+ :YAG (355 nm), the hydroxyl radical-driven epoxidation of unsaturated lipids with different numbers of C=C bonds can be completed in nanoseconds with high yields of up to 95%. Locations of C=C bonds were recognized with diagnostic fragment ions that were produced by either collision with an inert gas or auto-fragmentation resulting from the impact of energetic hot electrons and vibrational excitation. This technique has been applied to the analysis of breast cancer tissues of mice models without extensive sample processes. It was experimentally demonstrated that C=C bonds may be formed at different positions of not only regular mono- or poly-unsaturated fatty acids but also other odd-numbered long-chain fatty acids.

An aromatic substrate for hydroxylation by hydroxyl radicals ( • OH) was investigated. The probe, N,N '-(5-nitro-1,3-phenylene)- bis -glutaramide, and its hydroxylated product do not bind either iron(III) or iron(II), and so they do not interfere with the Fenton reaction. A spectrophotometric assay based on the hydroxylation of the substrate was developed. The synthesis and purification methods of this probe from previously published methodologies were improved upon, as well as the analytical procedure for monitoring the Fenton reaction through its use, enabling univocal and sensitive • OH detection. The assay was utilised to demonstrate that the iron(III) complexes of long-chain fatty acids lack Fenton activity under biological conditions.

In-situ thermal desorption (ISTD) has attracted increasing attention owing to the efficient removal of organic contaminants from contaminated sites. However, it is poorly understood that whether and to what extent contamination degradation occurs upon oxygenation of reduced Fe-bearing clay minerals (RFC) in the subsurface during ISTD. In this study, we evaluated the mechanism of contaminant degradation upon oxygenation of reduced clay minerals during the ISTD. Reduced nontronite (rNAu-2) and montmorillonite (rSWy-3) were selected as RFC models. Results showed that thermal treatment during ISTD could significantly enhance phenol degradation, which increased from 25.8 % at 10 °C to 74.4 % at 70 °C in rNAu-2 and from 17.7 % at 10 °C to 49.8 % at 70 °C in rSWy-3. Correspondingly, the cumulative •OH at steady-state ([•OH] ss ) increased by 3.7 and 1.5 times, respectively. The acceleration of Fe(II) oxidation with increasing temperature could be mainly responsible for [•OH] ss generation, which degrades phenol. Moreover, thermal treatment improved the fast oxidation of trioctahedral entities Fe(II)Fe(II)Fe(II) (TOF) and the slow oxidation of dioctahedral entities Fe(II)Fe(II) (DTF 1 ), AlFe(II) (DAF 1 ), and Fe(II)Fe(III) (DTF 2 ). Our study suggests that the overlooked degradation progress of phenol by oxygenation of RFC during ISTD, and it could be favorable for contaminant degradation during remediation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)