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The widespread use of rubber antioxidants, especially p-phenylenediamines (PPDs), has raised increasing concerns about their risk assessment. However, there is a notable lack of research on their transformation products (TPs). Photolysis, influenced by active components, plays a significant role in the environmental fates of PPDs. This study investigated four emerging PPDs (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N, N'-diphenyl-p-phenylenediamine (DPPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N-cyclohexyl-N'-phenyl-p-phenylenediamine (CPPD)) through a combination of experiments (photolysis kinetics, quenching experiments, acute toxicity test to Vibrio Fischeri (V. fischeri) and identification of photolytic products) and theoretical calculations. The results revealed different pathways for indirect photolysis mediated by the hydroxyl radicals (•OH) and singlet oxygen ( 1 O 2 ) of DPPD and IPPD under simulated sunlight irradiation. The effects of dissolved organic matter (DOM) and fulvic acid (FA) on the rates of photolysis of PPDs highlighted the complex interactions among the molecular structure, light absorption properties, and environmental variables. Quenching for reactive oxygen species (ROS) reduced photo-induced toxicity, whereas the addition of DOM and FA increased it, suggesting the crucial role of ROS in the formation of more toxic photolytic products. The study of photolysis pathways and the evaluation of the health risks provide a comprehensive understanding of the environmental effects of these 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 © 2024 Elsevier B.V. All rights reserved.)

This study investigated the degradation of aflatoxin B 1 (AFB 1 ) in food by using dual-frequency ultrasound (DFUS) and the effects of sonochemical oxidation on the efficacy. It was found that the degradation of AFB 1 by bath ultrasound (BU), probe ultrasound (PU), and DFUS were all consistent with first-order kinetics. The use of DFUS significantly increased the AFB 1 degradation to 91.3%, and compared with BU and PU, it increased by about 177.0% and 61.5% after 30 min treatment. DFUS could generate a synergistic effect to accelerate the generation of free radicals, which promoted sonochemical oxidation to degrade AFB 1 . It could be speculated that hydroxyl radical (·OH) probably acted a dominant part in the AFB 1 degradation by DFUS, and the hydrogen atoms (·H) might also are contributed. These results indicated that DFUS was an effective method of AFB 1 degradation., 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 Ltd.)

Chemodynamic therapy (CDT) is an innovative and burgeoning strategy that utilizes Fenton-Fenton-like chemistry and specific microenvironments to produce highly toxic hydroxyl radicals ( • OH), with numerous methods emerging to refine this approach. Herein, we report a coordination compound, Fe-norepinephrine nanoparticles (Fe-NE NPs), via a one-pot synthesis. The Fe-NE NPs are based on ferrous ions (Fe 2+ ) and norepinephrine, which are capable of efficient Fe 2+ /Fe 3+ delivery. Once internalized by tumor cells, the released Fe 2+ /Fe 3+ exerts the Fenton reaction to specifically produce toxic • OH. Moreover, the internal photothermal conversion ability of Fe-NE NPs allows us to simultaneously introduce light to trigger local heat generation and then largely improve the Fenton reaction efficiency, which enables a synergetic photothermal and chemodynamic therapy to realize satisfactory in vivo antitumor efficiency. This proof-of-concept work offers a promising approach to developing nanomaterials and refining strategies for enhanced CDT against tumors.

Cardiovascular disease (CVD) is a chronic disease characterized by the accumulation of lipids and fibrous tissue within the arterial walls, potentially leading to vascular obstruction and an increased risk of heart disease and stroke. Hydroxyl radicals play a significant role in the formation and progression of CVD as they can instigate lipid peroxidation, resulting in cellular damage and inflammatory responses. However, precisely detecting hydroxyl radicals in CVD lesions presents significant challenges due to their high reactivity and short lifespan. Herein, we present the development and application of a novel activatable optical probe, Cy-OH-LP , designed to detect hydroxyl radicals in lipid-rich environments specifically. Built on the Cy7 molecular skeleton, Cy-OH-LP exhibits near-infrared absorption and fluorescence characteristics, and its specific response to hydroxyl radicals enables a turn-on signal in both photoacoustic and fluorescence spectra. The probe demonstrated excellent selectivity and stability in various tests. Furthermore, Cy-OH-LP was successfully applied in an in vivo model to detect hydroxyl radicals in mouse models, providing a potential tool for diagnosing and monitoring AS. The biosafety of Cy-OH-LP was also verified, showing low cytotoxicity and no significant organ damage in mice. The findings suggest that Cy-OH-LP is a promising tool for the specific detection of hydroxyl radicals in lipid-rich environments, providing new possibilities for research and clinical applications in the field of oxidative stress-related diseases.

We developed stable luminescent morpholine-appended copper nanoclusters CuNCs@MorMB with an ultra-small size (<3 nm) and a long emission lifetime (577 ns). They mediate a Fenton-like reaction to produce reactive hydroxyl radicals (˙OH), subsequently depleting antioxidant glutathione levels for cancer chemodynamic therapy (CDT).

Chemodynamic therapy (CDT) utilizing the Fenton reaction to convert hydrogen peroxide (H 2 O 2 ) into cytotoxic hydroxyl radicals (˙OH) has recently drawn extensive interest in tumor treatment. However, the therapeutic efficiency of CDT often suffers from high concentrations of glutathione (GSH), insufficient endogenous H 2 O 2 and inefficient Fenton activity. Herein, a GSH-depleting and H 2 O 2 self-providing nanosystem that can efficiently load copper ions and doxorubicin (DOX) (MSN-Cu 2+ -DOX) to induce enhanced CDT and chemotherapy is proposed. The results show that MSN-Cu 2+ -DOX could release Cu 2+ and DOX under acidic conditions. Particularly, both the released Cu 2+ and Cu 2+ in MSN-Cu 2+ -DOX are available for ˙OH production via a Fenton-like reaction for CDT. Meanwhile, Cu 2+ undergoes a reduction to Cu + by depleting overexpressed GSH, thereby enhancing CDT. Moreover, the released DOX could not only be used for chemotherapy, but also promote the generation of endogenous H 2 O 2 to improve the efficiency of a Cu-based Fenton-like reaction. Resultantly, this nanosystem featuring Fenton-like activity, GSH consumption, H 2 O 2 self-sufficiency and chemotherapy exhibits a great antitumor effect with a tumor inhibition ratio of 93.05%. Overall, this study provides a promising strategy to enhance CDT for effective tumor therapy.

This study focused on exploring the effect of peroxydisulfate (PDS) on the regulation of reactive species during water radiolysis process and its potential application for degrading organic pollutants. The results indicated that PDS was successfully activated by ionizing radiation for efficient removal of three typical phenolic compounds over a wide pH range (3.0∼12.0) at absorbed dose of 5 kGy. Chemical probe methods provided the evidence that the addition of PDS could introduce the sulfate radicals (SO 4 •- ) and enhance the production of hydroxyl radicals ( • OH). According to the quenching tests, • OH and SO 4 •- were the dominant reactive species responsible for the degradation of 4-NP, while hydrated electron (e aq - ) played a minor role. The regulatory effect of PDS on active species in the ionizing radiation process could divided by (i) PDS could be directly activated by ionizing radiation to produce • OH and SO 4 •- via energy transfer pathway; (ii) PDS could boost the conversion of e aq - to SO 4 •- via electron transfer pathway. Furthermore, we assessed the applicability of the IR and IR/PDS systems in treating mixed solutions containing various pollutants and actual coking wastewater., 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. Published by Elsevier Ltd.)

Chlorite (ClO 2 - ) is a regulated byproduct of chlorine dioxide water treatment processes. The transformation of chlorite under UV irradiation into chloride (Cl - ) and chlorate (ClO 3 - ) involves reactive species chain reactions that could enhance chlorine dioxide water treatment efficiency while reducing residual chlorite levels. This study conducted a mechanistic investigation of chlorite phototransformation by analyzing reaction intermediates and stable end products, including chlorine dioxide (ClO 2 ), free chlorine (HOCl/OCl - ), hydroxyl‑radical ( • OH), Cl - , and ClO 3 - through combined experimental and modeling approaches. Experiments were performed at UV 254 irradiation in pure buffered water within the pH range of 6 to 8. Results indicated that the apparent quantum yields for chlorite phototransformation increased from 0.86 to 1.45, and steady-state • OH concentrations at 1 mM initial chlorite concentration rose from 8.16 × 10 -14 M - 16.1 × 10 -14 M with decreasing pH values. It was observed that under UV irradiation, chlorite acts as both a significant producer and consumer of reactive species through three distinct reaction pathways. The developed kinetic model, which incorporates optimized intrinsic chlorite quantum yields Φ chlorite in ranging from 0.33 to 0.39, effectively simulated the loss of oxidants and the formation of major products. It also accurately predicted steady-state concentrations of various species, including • OH, • ClO, Cl • and O 3 . For the first time, this study provides a comprehensive transformation pathway scheme for chlorite phototransformation. The findings offer important insights into the mechanistic aspects of product and oxidizing species formation during chlorite phototransformation., 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 Author(s). Published by 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 • .

Humin, endowed with abundant redox functional groups, can be reduced anaerobically under dark. When reduced humin encounters O 2 , the possibility of ·OH formation arises. However, the exploration of ·OH generation mediated by humin has not been comprehensively conducted. The study found that O 2 oxidized the reduced humin, generating 8.61 μmol/g of ·OH. After isolating humin using the methyl isobutyl ketone (MIBK) method, the lipid component was identified as the primary contributor to ·OH generation. Subsequent polar separation revealed that the lipid fraction extracted from the ethanol-water mixture with a volume ratio of 7:3 (LFEW7:3) played the most significant role in ·OH production. Further characterization confirmed that the simultaneous presence of aromatic C═C and C═O were the predominant features contributing to the ·OH generation. The ·OH generation experiments with humin-pyridine analogue compound demonstrated that polycyclic pyridine N (≥3 rings) played a significant role in promoting the ·OH generation. Most importantly, the study compared the ·OH production by humin and homologous humic acid, indicating that ·OH generated by humin was higher than that of humic acid. Overall, these affirmative findings manifested the overlooked role of humin in ·OH production and offered valuable insights into the mechanism of ·OH generation by humin in the dark.

The extracellular degradation of antibiotics facilitated by bio-nanoparticles is significant in the field of waste valorization. Among different bio-nanoparticles, bio-FeS nanoparticles stand out for their convenient and cost-effective synthesis. Nevertheless, there is a lack of understanding regarding the extracellular degradation of pollutants driven by bio-FeS nanoparticles. Hence, this study aimed to investigate the role of bio-FeS nanoparticles in the extracellular degradation of tetracycline under aerobic and anaerobic conditions. The findings demonstrated that bio-FeS nanoparticles generated hydroxyl radical (·OH), which significantly contributes to the degradation of tetracycline in both aerobic and anaerobic environments. The production of ·OH in anaerobic conditions was primarily attributed to the limited formation of FeS 2 during the biosynthesis of nanoparticles, which was very different from aerobic conditions. The bio-FeS nanoparticles facilitated extracellular electron transport by promoting electron shuttles and Fe(II)/Fe(III) cycling, resulting in the continuous production of ·OH. The degradation pathways showed differences under aerobic and anaerobic conditions, with intermediates exhibiting higher toxicity and greater cellular damage under aerobic conditions. However, in anaerobic conditions, bio-FeS nanoparticles enabled the successful integration of intracellular and extracellular degradation of tetracycline. This research proposed a new avenue for biocatalysis and environmental 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 © 2024 Elsevier B.V. All rights reserved.)

2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (UV328) is an emerging persistent organic pollutant ubiquitously found in environmental matrices. Though some advanced oxidation processes have been tested to degrade UV328 in waste streams, the degradation mechanisms are largely unknown. In this study, the degradation of UV328 by ozone (O 3 ) and peroxymonosulfate (PMS) was systemically investigated. At neutral pH, 97.0% UV328 was removed in 5 min with 6.4 mg/min O 3 and 2 mM PMS, and the degradation rate was positively correlated with the concentration of oxidants. Hydroxyl radical (•OH), sulfate radical (SO 4 •- ) and singlet oxygen ( 1 O 2 ) participated in the degradation of UV328, in which 1 O 2 played a key role. Based on the identified transformation intermediates and density functional theory simulations, three degradation pathways of dehydrogenation, cycloaddition and hydroxylation were proposed. •OH and SO 4 •- radicals could attack UV328 through hydrogen atom abstraction channel. 1 O 2 -mediated cycloaddition reaction is favorable, and •OH could react with UV328 via radical adduct formation pathway. Toxicity assessment indicated that O 3 /PMS treatment mitigated the ecological risks of UV328., 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.)

Tetrabromobisphenol A bis (allyl ether) (TBBPA-BAE) represents an extensively used brominated flame retardant (BFRs) in the production of many fields and their phototransformation in natural water is still unclear. The environmentally persistent free radicals (EPFRs) with preserved activities could exist in the environment for a long time and involve in the phototransformation of many organic pollutants. Here, the photodegradation of TBBPA-BAE with the degradation rate constant (k = 0.060 h -1 ) under simulate sunlight and the promoting effect of EPFRs on TBBPA-BAE photodegradation (k = 0.135 h -1 ) were investigated. According to the detected photogenerated electrons (e - ) and singlet oxygen ( 1 O 2 ) rather than hydroxyl radicals (•OH) by the electron paramagnetic resonance (EPR), the effect mechanism may not be related to the typical •OH induced by EPFRs. The possible transformation pathways of the ether cleavage, hydrolysis and hydroxylation of propenyl bond and the debromination were proposed by the primary byproducts identified by UPLC-Q-Exactive Orbitrap MS. EPFRs caused a further debromination and ether cleavage and probably be due to EPFRs directly providing electrons to TBBPA-BAE which promoted the photodegradation of TBBPA-BAE, and their reaction mechanism needed further attention. Overall, this study provided useful information to understand the role of EPFRs on phototransformation of TBBPA-BAE in water., 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.)

Respiratory complex I (R-CI) is an essential enzyme in the mitochondrial electron transport chain but also a major source of reactive oxygen species (ROS), which are implicated in neurodegenerative diseases and ageing. While the mechanism of ROS production by R-CI is well-established, the feedback of ROS on R-CI activity is poorly understood. Here, we perform EPR spectroscopy on R-CI incorporated in artificial membrane vesicles to reveal that ROS (particularly hydroxyl radicals) reduce R-CI activity by making the membrane more polar and by increasing its hydrogen bonding capability. Moreover, the mechanism that we have uncovered reveals that the feedback of ROS on R-CI activity via the membrane is transient and not permanent; lipid peroxidation is negligible for the levels of ROS generated under these conditions. Our successful use of modular proteoliposome systems in conjunction with EPR spectroscopy and other biophysical techniques is a powerful approach for investigating ROS effects on other membrane proteins., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)

Photodynamic therapy (PDT) can destroy tumor cells by generating singlet oxygen ( 1 O 2 ) under light irradiation, which is limited by the hypoxia of the neoplastic tissue. Chemodynamic therapy (CDT) can produce toxic hydroxyl radical (⋅OH) to eradicate tumor cells by catalytic decomposition of endogenous hydrogen peroxide (H 2 O 2 ), the therapeutic effect of which is highly dependent on the concentration of H 2 O 2 . Herein, we propose a BODIPY-ferrocene conjugate with a balanced 1 O 2 and ⋅OH generation capacity, which can serve as a high-efficiency antitumor agent by combining PDT and CDT. The ferrocene moieties endow the as-prepared conjugates with the ability of chemodynamic killing of tumor cells. Moreover, combined PDT/CDT therapy with improved antitumor efficiency can be realized after exposure to light irradiation. Compared with the monotherapy by PDT or CDT, the BODIPY-ferrocene conjugates can significantly increase the intracellular ROS levels of the tumor cells after light irradiation, thereby inducing the tumor cell apoptosis at low drug doses. In this way, a synergistic antitumor treatment is achieved by the combination of PDT and CDT., (© 2024 Wiley-VCH GmbH.)

The spontaneous generation of hydrogen peroxide (H 2 O 2 ) within atmospheric microdroplets, such as raindrops and aerosols, plays a crucial role in various environmental processes including pollutant degradation and oxidative stress. However, quantifying hydroxyl radicals (•OH), essential for H 2 O 2 formation, remains challenging due to their short lifespan and low concentration. This study addresses this gap by presenting a highly sensitive and selective surface-enhanced Raman scattering (SERS) nanosensor specifically designed for quantifying •OH within water microdroplets. Utilizing a phthalhydrazide (Phth) probe, the SERS technique enables rapid, interference-free detection of •OH at nanomolar concentrations. It achieves a linear detection range from 2 nM to 2 μM and a limit of detection as low as 0.34 nM. Importantly, the SERS sensor demonstrates robustness and accuracy within water microdroplets, paving the way for comprehensive mechanistic studies of H 2 O 2 generation in the atmosphere. This innovative approach not only offers a powerful tool for environmental research but also holds potential for advancing our understanding of atmospheric H 2 O 2 formation and its impact on air quality and pollutant degradation.

In this study, a hydroxyl radical oxidation system was established to simulate the oxidation process in fermented meat products. This system was employed to examine the structural changes in myofibrillar proteins (MPs) resulting from tryptic hydrolysis after a hydroxyl radical oxidative regime. The effect of these changes on the ability of MPs to bind selected aldehydes (3-methyl butanal, pentanal, hexanal, and heptanal) was also investigated. Moderate oxidation (H 2 O 2  ≤ 1.0 mM) unfolded the structure of MPs, facilitating trypsin-mediated hydrolysis and increasing their binding capacity for the four selected aldehydes. However, excessive oxidation (H 2 O 2  ≥ 2.5 mM) led to cross-linking and aggregation of MPs, inhibiting trypsin-mediated hydrolysis. The oxidised MPs had the best binding capacity for heptanal. The interaction of the oxidised trypsin-hydrolysed MPs with heptanal was driven by hydrophobic interactions. The binding of heptanal affected the structure of the oxidised trypsin-hydrolysed MPs and reduced their α-helix content., 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 Ltd.)

Context: Recently, a few antiviral drugs viz Molnupiravir (EIDD-1931), Favipiravir, Ribavirin, Sofosbuvir, Galidesivir, and Remdesivir are shown to be beneficial against COVID-19 disease. These drugs bind to the viral RNA single strand to inhibit the virus genome replication. Similarly, recently, some artificial nucleotides, such as P, J, B, X, Z, V, S, and K were proposed to behave as potent antiviral candidates. However, their activity in the presence of the most reactive hydroxyl (OH) radical is not yet known. Here, the possibility of RNA strand break due to the OH radical-induced C1'-hydrogen (H) abstraction reaction of the above molecules (except Remdesivir) is studied in detail by considering their nucleotide conformation. The results are compared with those of the natural RNA nucleotides (G, C, A, and U). Due to low Gibbs barrier-free energy and high exothermicity, all these nucleotides (except Remdesivir) are prone to OH radical-induced C1'-H abstraction reaction. As Remdesivir contains a C1'-CN bond, the OH radical substitution reactions at the CN and C1' sites would likely liberate the catalytically important CN group, thereby downgrading its activity., Method: Initially, the B3LYP-D3 dispersion-corrected density functional theory method and 6-31 + G* basis set were used to optimize all reactant, transition state, and product complexes in the implicit aqueous medium. Subsequently, the structures of these complexes were further optimized by using the ωB97X-D dispersion-corrected density functional theory method and cc-PVTZ basis set in the aqueous medium. The IEFPCM method was used to model the aqueous medium., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Hydroxyl (OH) and hydroperoxyl (HO 2 ) radicals, collectively known as HOx radicals, are crucial in removing primary pollutants, controlling atmospheric oxidation capacity, and regulating global air quality and climate. An imbalance between radical observations and simulations has been identified based on radical closure experiments, a valuable tool for accessing the state-of-the-art chemical mechanisms, demonstrating a deviation between the existing and actual tropospheric mechanisms. In the past decades, researchers have attempted to explain this deviation and proposed numerous radical generation mechanisms. However, these newly proposed unclassical radical generation mechanisms have not been systematically reviewed, and previous radical-related reviews dominantly focus on radical measurement instruments and radical observations in extensive field campaigns. Herein, we overview the unclassical generation mechanisms of radicals, mainly focusing on outlining the methodology and results of radical closure experiments worldwide and systematically introducing the mainstream mechanisms of unclassical radical generation, involving the bimolecular reaction of HO 2 and organic peroxy radicals (RO 2 ), RO 2 isomerization, halogen chemistry, the reaction of H 2 O with O 2 over soot, epoxide formation mechanism, mechanism of electronically excited NO 2 and water, and prompt HO 2 formation in aromatic oxidation. Finally, we highlight the existing gaps in the current studies and suggest possible directions for future research. This review of unclassical radical generation mechanisms will help promote a comprehensive understanding of the latest radical mechanisms and the development of additional new mechanisms to further explain deviations between the existing and actual mechanisms.

Nitrites (NO 2 - /HONO), as the primary source of hydroxyl radicals ( • OH) in the atmosphere, play a key role in atmospheric chemistry. However, the current understanding of the source of NO 2 - /HONO is insufficient and therefore hinders the accurate quantification of atmospheric oxidation capacity. Herein, we highlighted an overlooked HONO source by the reaction between nitrophenols (NPs) and • OH in the aqueous phase and provided kinetic data to better evaluate the contribution of this process to atmospheric HONO. Three typical NPs, including 4-nitrophenol (4NP), 2-nitrophenol (2NP), and 4-nitrocatechol (4NC), underwent a denitration process to form aqueous NO 2 - and gaseous HONO through the • OH oxidation, with the yield of NO 2 - /HONO varied from 15.0 to 33.5%. According to chemical composition and structure analysis, the reaction pathway, where the ipso addition of • OH to the NO 2 group on 4NP generated hydroquinone, can contribute to more than 61.9% of the NO 2 - /HONO formation. The aqueous photooxidation of NPs may account for HONO in the atmosphere, depending on the specific conditions. The results clearly suggest that the photooxidation of NPs should be considered in the field observation and calculation to better evaluate the HONO budget in the atmosphere.

β-caryophyllonic acid (BCA), as an important precursor of aqueous secondary organic aerosols (aqSOA), has adverse effects on the atmospheric environment and human health. However, the key atmospheric chemical reaction process in which BCA participates in the formation of aqueous secondary organic aerosols is still unclear. In this study, the reaction mechanism and kinetics of BCA with ·OH and O 3 were investigated by quantum chemical calculations. The initiation reactions between BCA and ·OH include addition and H-abstraction reaction pathways, subsequent intermediates will also react with O 2 , ultimately undergo a cracking reaction to generate small molecular substances. The reaction of BCA with O 3 can generate primary ozone oxides and the Criegee Intermediates oIM3, subsequent main reaction products include keto-BCA, as well as other small molecule aqSOA precursors. The entire reaction process increases the O/C ratio of aqSOA in the aqueous phase and generates products of small molecules such as 4-formylpropionic acid, which plays an important role in the formation of aqSOA. At 298K, the transformation rate constants of BCA initiated by ·OH and O 3 are 1.47 × 10 10  M -1  s -1 and 3.16 × 10 5  M -1  s -1 , respectively, the atmospheric lifetimes of BCA reacting with ·OH range from 0.86 h-5.40 h, while the lifetimes of BCA reacting with O 3 range from 0.44 h-10.04 years. This suggests that BCA primarily reacts with ·OH. However, under higher O 3 concentrations, its ozonolysis becomes significant, promoting the formation of aqSOA. According to the risk assessment, the toxicity of most transformation products (TPs) gradually decreased, but the residual developmental toxicity could not be ignored. In this paper, the atmospheric liquid phase oxidation mechanisms of sesquiterpene unsaturated derived acid were studied from the microscopic level, which has guiding significance for the formation and transformation of aqSOA in atmosphere., 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.)

Citrinin (CIT), a mycotoxin produced by Monascus, Penicillium, and other fungies, can contaminate red yeast rice and other foods, thus constraining their application and development. Exploring efficient degradation methods of citrinin is becoming as one of the hot research topics. In this study, the degradation of citrinin, irradiated by visible (Vis) light, ultraviolet (UV) light, and simulated sunlight alone, as well as in combination with hydrogen peroxide (light/H 2 O 2 ), was investigated. The research demonstrates UV, Vis, and simulated sunlight all have a degree of degradation on citrinin, and the degradation efficiency correlates with light source and light intensity. Interestingly, when combined with 100 W Vis and 0.01 M H 2 O 2 , the citrinin degradation rate increases to 32%, compared to 1% and 5% achieved by Vis and H 2 O 2 alone. Hydroxyl radicals, arising from the uniform cracking of H 2 O 2 under Vis, were experimentally validated by electron spin resonance measurement and could accelerate the dissociation of citrinin by nucleophilic attacking. Employing the density functional theory, we deduced nucleophilic •OH mainly attack onto C 8 and C 5 site by comparing the electrophilic Parr functions (Pk + ) value of main C atom of citrinin. This research presents a rapid and efficient degradation of citrinin by combining visible light with H 2 O 2 . PRACTICAL APPLICATION: This research presents a rapid and efficient method for the degradation of citrnin in red yeast rice and other citrnin containing products by combining visible light with H 2 O 2 ., (© 2024 Institute of Food Technologists.)

The abatement of micropollutants by ozonation can be accurately calculated by measuring the exposures of molecular ozone (O 3 ) and hydroxyl radical ( • OH) (i.e., ∫[O 3 ]dt and ∫[ • OH]dt). In the actual ozonation process, ∫[O 3 ]dt values can be calculated by monitoring the O 3 decay during the process. However, calculating ∫[ • OH]dt is challenging in the field, which necessitates developing models to predict ∫[ • OH]dt from measurable parameters. This study demonstrates the development of machine learning models to predict ∫[ • OH]dt (the output variable) from five basic input variables (pH, dissolved organic carbon concentration, alkalinity, temperature, and O 3 dose) and two optional ones (∫[O 3 ]dt and instantaneous ozone demand, IOD). To develop the models, four different machine learning methods (random forest, support vector regression, artificial neural network, and Gaussian process regression) were employed using the input and output variables measured (or determined) in 130 different natural water samples. The results indicated that incorporating ∫[O 3 ]dt as an input variable significantly improved the accuracy of prediction models, increasing overall R 2 by 0.01-0.09, depending on the machine learning method. This suggests that ∫[O 3 ]dt plays a crucial role as a key variable reflecting the • OH-yielding characteristics of dissolved organic matter. Conversely, IOD had a minimal impact on the accuracy of the prediction models. Generally, machine-learning-based prediction models outperformed those based on the response surface methodology developed as a control. Notably, models utilizing the Gaussian process regression algorithm demonstrated the highest coefficients of determination (overall R 2 = 0.91-0.95) among the prediction 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 Ltd. All rights reserved.)

Ultrafiltration (UF) is increasingly used in the pretreatment of shale gas produced water (SGPW), whereas severe membrane fouling hampers its actual operation. In this work, ferrate(VI)-based oxidation was proposed for membrane fouling alleviation in SGPW pretreatment, and the activation strategies of calcium peroxide (CaO 2 ) and ultraviolet (UV) were selected for comparison. The findings indicated that UV/Fe(VI) was more effective in removing fluorescent components, and the concentration of dissolved organic carbon was reduced by 24.1 %. With pretreatments of CaO 2 /Fe(VI) and UV/Fe(VI), the terminal specific membrane flux was elevated from 0.196 to 0.385 and 0.512, and the total fouling resistance diminished by 52.7 % and 76.2 %, respectively. Interfacial free energy analysis indicated that the repulsive interactions between pollutants and membrane were notably enhanced by Fe(VI)-based oxidation, thereby delaying the deposition of cake layers on the membrane surface. Quenching and probe experiments revealed that high-valent iron intermediates (Fe(IV)/Fe(V)) played significant roles in both CaO 2 /Fe(VI) and UV/Fe(VI) processes. Besides, hydroxyl radicals ( • OH) were also important reactive species in the UV/Fe(VI) treatment, and the synergistic effect of Fe(IV)/Fe(V) and • OH showed a positive influence on SGPW fouling mitigation. In general, these findings establish a theoretical underpinning for the application of Fe(VI)-based oxidation for UF membrane fouling mitigation in SGPW pretreatment., 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.)

The conventional silver nanoparticles (Ag NPs) are characterized with high loading rate and stacking phenomenon, leading to shedding caused biotoxicity and low catalytic efficiency. This seriously hinders their application in biomedicine. Here, we modified the highly dispersible Ag NPs and Ag single-atoms (SAs) synthesis by combining the halloysite clay nanotubes (HNTs) and dodecahydro-dodecaborate (closo-[B 12 H 12 ] 2- ) to increase the biocompatible properties and decrease the loading rate. This novel Ag single-atom nanoenzyme alongside Ag NPs nanoenzyme avoid the elevated-temperature calcination while maintaining the exceptionally high-level efficiency of Ag utilization via the reducibility and coordination stabilization of closo-[B 12 H 12 ] 2- and HNTs. With theoretical calculation and electron paramagnetic resonance, we confirmed that both Ag SAzymes and Ag NPs in HNT@B 12 H 12 @Ag nanoenzyme are capable decompose the H 2 O 2 into hydroxyl radical (·OH). For the application, we investigated the catalytic activity in the tumor cells and antitumor effects of HNT@B 12 H 12 @Ag nanoenzyme both in vitro and in vivo, and confirmed that it effectively suppressed melanoma growth through ·OH generation, with limited biotoxicity. This study provides a novel Ag nanoenzyme synthesis approach to increase the possibility of its clinical application., 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 B.V. All rights reserved.)

We investigated the deoxyribonucleic acid (DNA) damage induced by laser filamentation, which was generated by focusing femtosecond near-infrared Ti:Sapphire laser light in water at several repetition rates ranging from 1000 Hz to 10 Hz. Using plasmid DNA (pUC19), the single-strand break, double-strand break, nucleobase lesions, and the fragmented DNA were analyzed and quantified by agarose gel electrophoresis. Additionally, the H 2 O 2 concentration after irradiation was determined. We observed that (1) the DNA damage per laser shot and (2) the enzyme-sensitive base lesions per total DNA damage decreased as the laser repetition rate increased. Furthermore, (3) extraordinarily short DNA fragments were likely to be produced, compared with those produced using X-rays, and (4) most OH radicals could be eliminated by recombination to generate H 2 O 2 , preventing them from damaging the DNA. The Monte-Carlo simulation of the strand break formation implies that the observed dependency of strand break efficiency on the laser repetition rate is mainly due to diffusion of DNA molecules. These findings quantitatively and qualitatively revealed that an intense laser pulse induces a specific DNA damage profile that is not induced by X-rays, a sparsely ionizing radiation source., 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 B.V. All rights reserved.)

The effectiveness of ozonation, one of the techniques known for destroying organic contaminants from wastewater, depends on the composition of the wastewater matrix. The required ozone (O 3 ) dose is determined based on the target compounds during ozonation. Hydroxyl radicals are quantified using a probe compound. The para-chlorobenzoic acid (pCBA) is typically used as a probe compound to measure hydroxyl radicals. However, real-time measurement is impossible, as the analysis process consumes time and resources. This study aimed to evaluate the spectroscopic characteristics of various organic substances in wastewater ozonation through fluorescence excitation-emission matrix and parallel factor analysis. The study also demonstrated that real-time analyzable tryptophan-like fluorescence (TLF) can be used as a hydroxyl radical index. Importantly, the correlation between para-chlorobenzoic acid and TLF was derived, and the results showed a high correlation (R 2  = 0.91), confirming the reliability of our findings. Seven trace organic compounds, classified based on their reactivity with O 3 and hydroxyl radicals, were selected as target compounds and treated with O 3 . The TLF index was used as a model factor for the removal rate of the target compounds. The experimental and model values matched when the O 3 dose was below 1.0 g O 3 /g DOC (RMSE: 0.0445-0.0895)., 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 Ltd.. All rights reserved.)

Recognizing the pervasive presence of alumina minerals and low-molecular-weight organic acids (LMWOAs) in the environment, this study addressed the gap in the interaction mechanisms within the ternary system involving these two components and Fe(II). Specifically, the impacts of LMWOAs on hydroxyl radicals (•OH) production and iron species transformation during Fe(II) oxidation on γ-Al 2 O 3 mineral surface were examined. Results demonstrated that adding 0.5 mM oxalate (OA) or citrate (CA) to the γ-Al 2 O 3 /Fe(II) system (28.1 μM) significantly enhanced •OH production by 1.9-fold (51.9 μM) and 1.3-fold (36.2 μM), respectively, whereas succinate (SA) exhibited limited effect (30.7 μM). Raising OA concentration to 5 mM further promoted •OH yield to 125.0 μM after 24 h. Deeper analysis revealed that CA facilitated the dissolution of adsorbed Fe(II) and its subsequent oxygenation by O 2 through both one- and two-electron transfer mechanisms, whereas OA enhanced the adsorption of dissolved Fe(II) and more efficient two-electron transfer for H 2 O 2 production. Additionally, LMWOAs presence favored the formation of iron minerals with poor crystallinity like ferrihydrite and lepidocrocite rather than well-crystallized forms such as goethite. The distinct impacts of various LMWOAs on Fe(II) oxidation and •OH generation underscore their unique roles in the redox processes at mineral surface, consequently modulating the environmental fate of prototypical pollutants like phenol., 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.)

Chemodynamic therapy (CDT), an approach that eradicates tumor cells through the catalysis of hydrogen peroxide (H 2 O 2 ) into highly toxic hydroxyl radicals (·OH), possesses distinct advantages in tumor specificity and minimal side effects. However, CDT's therapeutic efficacy is currently hampered by the low production efficiency of ·OH. To address this limitation, this study introduces a water-soluble chitosan-coated W-doped MoO x (WMoO x /CS) designed for the combined application of photothermal therapy (PTT) combined with CDT. The W-doped MoO x (WMoO x ) was synthesized in one step by the hydrothermal method, and its surface was modified by water-soluble chitosan (carboxylated chitosan, CS) to enhance its biocompatibility. WMoOx boasts a high near-infrared photothermal conversion efficiency of 52.66 %, efficiently transducing near-infrared radiation into heat. Moreover, the Mo 4+ /Mo 5+ and W 5+ ions in WMoO x catalyze H 2 O 2 to produce ·OH for CDT, and the Mo 5+ /Mo 6+ and W 6+ ions in WMoO x reduce intracellular glutathione levels and prevent the scavenging of ·OH by glutathione. Crucially, the combination of WMoO x /CS and near-infrared light irradiation demonstrates promising synergistic antitumor effects in both in vitro and in vivo models, highlighting its potential for the combined application of PTT and CDT., 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 B.V. All rights reserved.)

Ozonation is used worldwide for drinking water disinfection and increasingly also for micropollutant abatement from wastewater. Identification of transformation products formed during the ozonation of micropollutants is challenging due to several factors including (i) the reactions of both oxidants, ozone and hydroxyl radicals with the micropollutants, as well as with intermediate transformation products, (ii) effects of the water matrix on the ozone and hydroxyl radical chemistry and (iii) the generation of oxidation by-products. In this study, a simple approach to achieve realistic ozonation conditions in the absence of dissolved organic matter has been developed. It is based on composing synthetic water matrices with low-molecular-weight scavenger compounds (phenol, methanol, acetate, and carbonate) that mimic the chemical interactions of ozone and hydroxyl radicals with real water matrices. Synthetic waters composed of only four low-molecular-weight compounds successfully replicated two lake waters and two secondary wastewater effluents, matching instantaneous ozone demand, ozone and hydroxyl radical exposures in the initial phase, as well as the ozone evolution in the second phase of the ozonation process. The synthetic water matrices also reproduced the effects of temperature and pH changes observed in real waters. The abatement of two micropollutants, bezafibrate and atrazine, and the formation of the corresponding transformation products during ozonation were in agreement for synthetic and real waters. Furthermore, the kinetics and extent of bromate formation during ozonation in synthetic water were comparable to real lake water and wastewater. This supports the robustness of the proposed approach because bromate formation is very sensitive to the interplay of ozone and hydroxyl radicals. Furthermore, with the novel reaction system, a significant effect of hydroxyl radicals scavenging by carbonate on bromate formation was demonstrated. Overall, the herein-developed approach based on synthetic water matrices allows to perform realistic ozonation studies including both oxidants, ozone and hydroxyl radicals, without the constraints of using dissolved organic matter., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Simon A. Rath reports financial support was provided by Swiss National Science Foundation. If there are other authors, they 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 Author(s). Published by Elsevier Ltd.. All rights reserved.)

Natural polyphenolic compound rosmarinic acid (RA) has good antitumor activity. However, the distinctive tumor microenvironment, characterized by low pH and elevated levels of glutathione (GSH), enhances the tolerance of tumors to the singular anti-tumor treatment mode using RA, resulting in unsatisfactory therapeutic efficacy. Targeting nonapoptotic programmed cell death processes may provide another impetus to inhibit tumor growth. RA possesses the capability to coordinate with metal elements. To solve the effect restriction of the above single treatment mode, it is proposed to construct a self-assembled nanocomposite, Fe-RA. Under tumor microenvironment, Fe-RA nanocomposite exerts the characteristics of POD-like enzyme activity and depletion of GSH, producing a large amount of hydroxyl radical (·OH) while disrupting the antioxidant defense system of tumor cells. Moreover, due to the enhanced permeability and retention effect (EPR), Fe-RA can transport Fe 2+ to a greater extent to tumor cells and increase intracellular iron content. Causing an imbalance in iron metabolism in tumor cells and promoting cell ferroptosis. The results of the synchrotron X-ray absorption spectroscopy (XAS) and high-resolution mass spectrometry (HRMS) prove the successful complexation of Fe-RA nanocomposite. Density functional theory (DFT) explains the efficient catalytic mechanism of its peroxide-like enzyme activity and the reaction principle with GSH., (© 2024 Wiley‐VCH GmbH.)

Although dissolved oxygen plays an important role in electro-Fenton-like processes, few investigations have revealed its underlying effects in such processes. Herein, the effect of dissolved oxygen on peroxide activation in an electro-Fenton-like system comprising electrochemical cells and peroxymonosulfate (PMS) was investigated. Cobalt phosphide-modified carbon aerogel (Co/P/CA) was used as the cathode material owing to the high conductivity and catalytic activity of Co/P/CA. Several free radicals and their effects on organic pollutant removal were observed using electron paramagnetic resonance spectrometry and quenching experiments, respectively. The observations revealed that in the presence of O 2 , hydroxyl radical (·OH), superoxide (O 2 - ·), and singlet oxygen ( 1 O 2 ) served as the primary active species in the PMS activation process, while in the presence of N 2 , ·OH and sulfate radical (SO 4 - ·) served as the dominant active species in this process. The factor responsible for the difference in the PMS activation pathways available under O 2 and N 2 conditions was investigated using rotating disk electrode tests and free energy calculations. The tests indicated that O 2 facilitates PMS activation to form ·OH instead of SO 4 - ·. The dissolved oxygen subsequently underwent a single-electron-reduction reaction and was converted into O 2 - ·, which could serve as a source of 1 O 2 . When N 2 was introduced, Co species, particularly Co(II), played a key role in activating PMS. The free radicals ·OH and SO 4 - · were generated during the PMS activation process. This study clearly demonstrates the mediating catalysis role of dissolved oxygen in electro-Fenton-like system through experimental data and theoretical calculations, thereby positively contributing to future studies regarding the continuous activation of peroxides in composite systems and improvement of the efficiency of waterbody remediation., Competing Interests: Declaration of competing interest We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In this study, we have utilized theoretical calculations to predict the reaction active sites of naproxen when reacting with radicals and to further study the thermodynamics and kinetics of the reactions with ·OH and SO 4 -· . The evidence, derived from the average local ionization energy and electrostatic potential, points to the naphthalene ring as the preferred site of attack, especially for the C2, C6, C9, and C10 sites. The changes in Gibbs free energy and enthalpy of the reactions initiated by ·OH and SO 4 -· ranged between -19.6 kcal/mol - 26.3 kcal/mol and -22.3 kcal/mol -18.5 kcal/mol, respectively. More in-depth investigation revealed that RA2 pathway for ·OH exhibited the lowest free energy of activation, suggesting this reaction is more inclined to proceed. The second-order rate constant results indicate the ·OH attacking reaction is faster than reactions initiated by SO 4 ·- , yet controlled by diffusion. The consistency between theoretical findings and experimental data underscores the validity of this computational method for our study., 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.)

Cuproptosis, as a newly identified form of programmed cell death, shows great promise in cancer treatment. Efficient Cu + delivery while avoiding systemic toxicity and elimination of the resistance from over-expressed intracellular copper chelator glutathione (GSH) are critical for cuproptosis. Herein, this work innovatively constructs a biocompatible and defect-rich copper hydroxide nanowire (HCu nanowire) through a human serum albumin (HSA) mediated biomineralization method. This work finds that the morphology and size of HCu nanowires can be controlled adjusted by the feed ratio of HSA and Cu 2+ . Remarkably, except for outstanding biocompatibility, HSA coordination endows HCu nanowires abundant oxygen vacancies (OVs), and the defect-rich HCu nanowire possesses excellent GSH consumption efficiency. Density functional theory studies indicate that OVs change GSH absorption energy on defective HCu nanowires. In cancer cells, HCu nanowires deplete GSH and simultaneously produce sufficient free Cu + for enhanced cuproptosis. Meanwhile, Cu + can catalyze endogenous H 2 O 2 into hydroxyl radicals (·OH) via a Fenton-like reaction. Thus, synergetic cuproptosis and ROS mediated apoptosis against tumor are achieved. The experimental results show that HCu nanowires have a better performance in both antitumor efficiency and safety compared with chemotherapeutic drug Dox at the same dose, demonstrating its great potential in clinical applications., (© 2024 Wiley‐VCH GmbH.)

Heterogeneous oxidation by gas-phase oxidants is an important chemical transformation pathway of secondary organic aerosol (SOA) and plays an important role in controlling the abundance, properties, as well as climate and health impacts of aerosols. However, our knowledge on this heterogeneous chemistry remains inadequate. In this study, the heterogeneous oxidation of α-pinene ozonolysis SOA by hydroxyl (OH) radicals was investigated under both low and high relative humidity (RH) conditions, with an emphasis on the evolution of molecular composition of SOA and its RH dependence. It is found that the heterogeneous oxidation of SOA at an OH exposure level equivalent to 12 hr of atmospheric aging leads to particle mass loss of 60% at 25% RH and 95% at 90% RH. The heterogeneous oxidation strongly changes the molecular composition of SOA. The dimer-to-monomer signal ratios increase dramatically with rising OH exposure, in particular under high RH conditions, suggesting that aerosol water stimulates the reaction of monomers with OH radicals more than that of dimers. In addition, the typical SOA tracer compounds such as pinic acid, pinonic acid, hydroxy pinonic acid and dimer esters (e.g., C 17 H 26 O 8 and C 19 H 28 O 7 ) have lifetimes of several hours against heterogeneous OH oxidation under typical atmospheric conditions, which highlights the need for the consideration of their heterogeneous loss in the estimation of monoterpene SOA concentrations using tracer-based methods. Our study sheds lights on the heterogeneous oxidation chemistry of monoterpene SOA and would help to understand their evolution and impacts in the atmosphere., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest, (Copyright © 2023. Published by Elsevier B.V.)

Fenton and Fenton-like processes, which could produce highly reactive species to degrade organic contaminants, have been widely used in the field of wastewater treatment. Therein, the chemistry of Fenton process including the nature of active oxidants, the complicated reactions involved, and the behind reason for its strongly pH-dependent performance, is the basis for the application of Fenton and Fenton-like processes in wastewater treatment. Nevertheless, the conflicting views still exist about the mechanism of the Fenton process. For instance, reaching a unanimous consensus on the nature of active oxidants (hydroxyl radical or tetravalent iron) in this process remains challenging. This review comprehensively examined the mechanism of the Fenton process including the debate on the nature of active oxidants, reactions involved in the Fenton process, and the behind reason for the pH-dependent degradation of contaminants in the Fenton process. Then, we summarized several strategies that promote the Fe(II)/Fe(III) cycle, reduce the competitive consumption of active oxidants by side reactions, and replace the Fenton reagent, thus improving the performance of the Fenton process. Furthermore, advances for the future were proposed including the demand for the high-accuracy identification of active oxidants and taking advantages of the characteristic of target contaminants during the degradation of contaminants by the Fenton process., 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.)

This study emphasizes the innovative application of FePt and Cu core-shell nanostructures with increased lattice microstrain, coupled with Au single-atom catalysis, in significantly enhancing • OH generation for catalytic tumor therapy. The combination of core-shell with increased lattice microstrain and single-atom structures introduces an unexpected boost in hydroxyl radical ( • OH) production, representing a pivotal advancement in strategies for enhancing reactive oxygen species. The creation of a core-shell structure, FePt@Cu, showcases a synergistic effect in • OH generation that surpasses the combined effects of FePt and Cu individually. Incorporating atomic Au with FePt@Cu/Au further enhances • OH production. Both FePt@Cu and FePt@Cu/Au structures boost the O 2 → H 2 O 2 → • OH reaction pathway and catalyze Fenton-like reactions. This enhancement is underpinned by DFT theoretical calculations revealing a reduced O 2 adsorption energy and energy barrier, facilitated by lattice mismatch and the unique catalytic activity of single-atom Au. Notably, the FePt@Cu/Au structure demonstrates remarkable efficacy in tumor suppression and exhibits biodegradable properties, allowing for rapid excretion from the body. This dual attribute underscores its potential as a highly effective and safe cancer therapeutic agent.

A Fe 2+ -EGTA(ethylene glycol-bis (β-aminoethyl ether)- N , N , N ', N '-tetraacetic acid)-H 2 O 2 system emits photons, and quenching this chemiluminescence can be used for determination of anti-hydroxyl radical (•OH) activity of various compounds. The generation of •OH and light emission due to oxidative damage to EGTA may depend on the buffer and pH of the reaction milieu. In this study, we evaluated the effect of pH from 6.0 to 7.4 (that may occur in human cells) stabilized with 10 mM phosphate buffer (main intracellular buffer) on a chemiluminescence signal and the ratio of this signal to noise (light emission from medium alone). The highest signal (4698 ± 583 RLU) and signal-to-noise ratio (9.7 ± 1.5) were noted for pH 6.6. Lower and higher pH caused suppression of these variables to 2696 ± 292 RLU, 4.0 ± 0.8 at pH 6.2 and to 3946 ± 558 RLU, 5.0 ± 1.5 at pH 7.4, respectively. The following processes may explain these observations: enhancement and inhibition of •OH production in lower and higher pH; formation of insoluble Fe(OH) 3 at neutral and alkaline environments; augmentation of •OH production by phosphates at weakly acidic and neutral environments; and decreased regeneration of Fe 2+ -EGTA in an acidic environment. Fe 2+ -EGTA-H 2 O 2 system in 10 mM phosphate buffer pH 6.6 seems optimal for the determination of anti-•OH activity.

Metal-organic framework (MOF) modified with iron oxide, Fe 3 O 4 -MOF, is a perspective drug delivery agent, enabling magnetic control and production of active hydroxyl radicals, •OH, via the Fenton reaction. This paper studies cytotoxic and radical activities of Fe-containing nanoparticles (NPs): Fe 3 O 4 -MOF and its components - bare Fe 3 O 4 and MOF (MIL-88B). Luminous marine bacteria Photobacteriumphosphoreum were used as a model cellular system to monitor bioeffects of the NPs. Neither the NPs of Fe 3 O 4 -MOF nor MOF showed cytotoxic effects in a wide range of concentrations (<10 mg/L); while Fe 3 O 4 was toxic at >3·10 -3  mg/L. The NPs of Fe 3 O 4 did not affect the bacterial bioluminescence enzymatic system; their toxic effect was attributed to cellular membrane processes. The integral content of reactive oxygen species (ROS) was determined using a chemiluminescence luminol assay. Bacteria mitigated excess of ROS in water suspensions of Fe 3 O 4 -MOF and MOF, maintaining bioluminescence intensity closer to the control; this resulted in low toxicity of these NPs. We estimated the activity of •OH radicals in the NPs samples with physical and chemical methods - spin capture technology (using electron paramagnetic resonance spectroscopy) and methylene blue degradation. Physico-chemical interpretation of cellular responses is provided in terms of iron content, iron ions release and •OH radical production., 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 B.V. All rights reserved.)

The synthesis of graphene quantum dots-like enriched with specific oxygenated groups (o-GQDs) exhibiting great catalytic performance offers a promising tool for diagnosis and biomedicine, but introducing specific oxygen groups remains a challenge. Here, we propose a mild synthetic protocol for producing regulated fluorescence emission (from blue to yellow) carbonyl functionalized GQDs with double catalytic function through Fe 3 O 4 -catalyzed hydroxyl radical (·OH) oxidation the precursors like graphene oxide, polyaniline (PANI) and polydopamine (PDA). The method can be carried out at room temperature than the traditional high-temperature oxidation in concentrated acid. Interestingly, o-GQDs exhibit excellent peroxidase (POD)- and ascorbate oxidase-like activity. XPS characterization showed a significant increase in carbonyl content in o-GQDs compared to the precursor, even a 14-fold increase in blue-emitting iron-doped GQDs (b-Fe-GQDs). The introduction of Fe 3 O 4 during the synthesis process results in a minor degree of Fe doping, which enhances the catalytic activity of b-Fe-GQDs through coordination with N. Based on this feature, highly sensitive single-signal and ultra-selective dual-signal methods for alkaline phosphatase detection were developed. This low cost and safe synthesis strategy paves the way for practical usage of o-GQDs., 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 B.V. All rights reserved.)

The surface photochemical activity of goethite, which occurs widely in surface soils and sediments, plays a crucial role in the environmental transformation of various pollutants and natural organic matter. This study systemically investigated the mechanism of different types of surface hydroxyl groups on goethite in generating reactive oxygen species (ROSs) and Fe(III) reduction under sunlight irradiation. Surface hydroxyl groups were found to induce photoreductive dissolution of Fe(III) at the goethite-water interface to produce Fe 2+ (aq) , while promoting the production of ROSs. Substitution of the surface hydroxyl groups on goethite by fluoride significantly inhibited the photochemical activity of goethite, demonstrating their important role in photochemical activation of goethite. The results showed that the surface hydroxyl groups (especially the terminating hydroxyl groups, ≡FeOH) led to the formation of Fe(III)-hydroxyl complexes via ligand-metal charge transfer on the goethite surface upon photoexcitation, facilitating the production of Fe 2+ (aq) and •OH. The bridging hydroxyl groups (≡Fe 2 OH) were shown to mainly catalyze the production of H 2 O 2 , leading to the subsequent light-driven Fenton reaction to produce •OH. These findings provide important insights into the activation of molecular oxygen on the goethite surface driven by sunlight in the environment, and the corresponding degradation of anthropogenic and natural organic compounds caused by the generated ROSs.

The combination of ozone (O 3 ) and ferrate (Fe(VI)) oxidation technology demonstrates substantial potential for practical applications, though it has been underreported, resulting in gaps in comprehensive activity assessments and thorough exploration of its mechanisms. This study reveals that the previous use of a borate buffer solution obscured certain synergistic reactions between O 3 and Fe(VI), causing a reduction of activity by ∼40 % when oxidizing the electron-deficient pollutant atrazine. Consequently, we reassessed the activity and mechanisms using a buffer-salt-free O 3 /Fe(VI) system. Our findings showed that the hydroxyl radical ( · OH) served as the predominant active species, responsible for an impressive 95.9 % of the oxidation activity against electron-deficient pollutants. Additional experiments demonstrated that the rapid production of neglected and really important superoxide radicals ( · O 2 - ) could facilitate the decomposition of O 3 to generate · OH and accelerate the reduction of Fe(VI) to Fe(V), reactivating O 3 to produce · OH anew. Intriguingly, as the reaction progressed, the initially depleted Fe(VI) was partially regenerated, stabilizing at over 50 %, highlighting the significant potential of this combined system. Moreover, this combined system could achieve a high mineralization efficiency of 80.4 % in treating actual coking wastewater, complemented by extensive toxicity assessments using Escherichia coli, wheat seeds, and zebrafish embryos, showcasing its robust application potential. This study revisits and amends previous research on the O 3 /Fe(VI) system, providing new insights into its activity and synergistic mechanisms. Such a combined technology has potential for the treatment of difficult-to-degrade industrial wastewater., 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. Published by Elsevier Ltd.)

Rationale: Theranostic nanoplatforms exert a vital role in facilitating concurrent real-time diagnosis and on-demand treatment of diseases, thereby making contributions to the improvement of therapeutic efficacy. Nevertheless, the structural intricacy and the absence of well-defined integration of dual functionality persist as challenges in the development of theranostic nanoplatforms. Methods: We develop an atomically precise theranostic nanoplatform based on metal-organic cage (MOC) to provide magnetic resonance imaging (MRI) guided chemodynamic therapy (CDT) for cancer therapy and assess the theranostic performance both in vitro and in vivo . Through UV-vis spectroscopy, electron paramagnetic resonance (EPR), confocal microscopy, flow cytometry, immunofluorescence staining, and western blotting, the ability of MOC-Mn to generate •OH and the subsequent inhibition of HeLa cells was confirmed. Results: The MOC-Mn composed of manganese and calixarene was successfully synthesized and comprehensively characterized. The catalytic activity of manganese within MOC-Mn facilitated the efficient generation of hydroxyl radicals (•OH) through a Fenton-like reaction, leveraging the high concentrations of hydrogen peroxide in the tumor microenvironment (TME). Additionally, its capacity to prolong the T1 relaxation time and augment the MR signal was observed. The theranostic efficacy was verified via rigorous in vitro and in vivo experiments, indicating that MOC-Mn offered clearer visualization of tumor particulars and substantial suppression of tumor growth. Conclusion: This study showcases a precise MRI-guided CDT theranostic nanoplatform for cancer therapy, thereby promoting the advancement of precise nanomedicine and structure-function research., Competing Interests: Competing Interests: The authors have declared that no competing interest exists., (© The author(s).)

In recent years, using pharmacological ascorbic acid has emerged as a promising therapeutic approach in cancer treatment, owing to its capacity to induce extracellular hydrogen peroxide (H 2 O 2 ) production in solid tumors. The H 2 O 2 is then converted into cytotoxic hydroxyl free radicals (HO˙) by redox-active Fe 2+ inside cells. However, the high dosage of ascorbic acid required for efficacy is hampered by adverse effects such as kidney stone formation. In a recent study, we demonstrated the efficient catalytic conversion of H 2 O 2 to HO˙ by wüstite (Fe 1- x O) nanoparticles (WNPs) through a heterogenous Fenton reaction. Here, we explore whether WNPs can enhance the therapeutic potential of ascorbic acid, thus mitigating its dose-related limitations. Our findings reveal distinct pH dependencies for WNPs and ascorbic acid in the Fenton reaction and H 2 O 2 generation, respectively. Importantly, WNPs exhibit the capability to either impede or enhance the cytotoxic effect of ascorbic acid, depending on the spatial segregation of the two reagents by cellular compartments. Furthermore, our study demonstrates that treatment with ascorbic acid promotes the polarization of WNP-loaded macrophages toward a pro-inflammatory M1 phenotype, significantly suppressing the growth of 4T1 breast cancer cells. This study highlights the importance of orchestrating the interplay between ascorbic acid and nanozymes in cancer therapy and presents a novel macrophage-based cell therapy approach.

Hydrogen therapy, leveraging its selective attenuation of hydroxyl radicals (˙OH) and ONOO - , has emerged as a pivotal pathophysiological modulator with antioxidant, anti-inflammatory, and antiapoptotic attributes. Hydrogen therapy has been extensively studied both preclinically and clinically, especially in diseases with an inflammatory nature. Despite the substantial progress, challenges persist in achieving high hydrogen concentrations in target lesions, especially in cancer treatment. A notable breakthrough lies in water/acid reactive materials, offering enhanced hydrogen generation and sustained release potential. However, limitations include hydrogen termination upon material depletion and reduced bioavailability at targeted lesions. To overcome these challenges, catalytic materials like photocatalytic and sonocatalytic materials have surfaced as promising solutions. With enhanced permeability and retention effects, these materials exhibit targeted delivery and sustained stimuli-reactive hydrogen release. The future of hydrogen therapy hinges on continuous exploration and modification of catalytic materials. Researchers are urged to prioritize improved catalytic efficiency, enhanced lesion targeting effects, and heightened biosafety and biocompatibility in future development.

To oxidize trace concentrations of organic contaminants under conditions relevant to surface- and groundwater, air-diffusion cathodes were coupled to stainless-steel cathodes that convert atmospheric O 2 into hydrogen peroxide (H 2 O 2 ), which then was activated to produce hydroxyl radicals ( · OH). By separating H 2 O 2 generation from its activation and employing a flow-through electrode consisting of stainless-steel fibers, the two processes could be operated efficiently in a manner that overcame mass-transfer limitations for O 2 , H 2 O 2 , and trace organic contaminants. The flexibility resulting from separate control of the two processes made it possible to avoid both the accumulation of excess H 2 O 2 and the energy losses that take place after H 2 O 2 has been depleted. The decrease in treatment efficacy occurring in the presence of natural organic matter was substantially lower than that typically observed in homogeneous advanced oxidation processes. Experiments conducted with ionized and neutral compounds indicated that electrostatic repulsion prevented negatively charged · OH scavengers from interfering with the oxidation of neutral contaminants. Energy consumption by the dual-cathode system was lower than values reported for other technologies intended for small-scale drinking water treatment systems. The coordinated operation of these two cathodes has the potential to provide a practical, inexpensive way for point-of-use drinking water treatment.

A sequential dual-locked luminescent copper nanoclusters (CuNCs) probe was designed and synthesized for the specific imaging and selective killing of tumor cells. This nanoprobe was prepared by first forming a Fe 3+ -coupled tannic acid (TA)-stabilized CuNCs (CuNCs-Fe III ), which is in quenching state due to the electron transfer between CuNCs and Fe 3+ , and then coating a protectable layer of hyaluronic acid (HA) on the surface of CuNCs-Fe III to form the final dual-locked nanoprobe (CuNCs-Fe III @HA). When the nanoprobe of CuNCs-Fe III @HA target enter the tumor cells through CD44-HA receptor, HAase will first digest the HA layer of the nanoprobes, and then, GSH over-expressed in tumor cells will reduce Fe 3+ to Fe 2+ , thus restoring the fluorescence emission of CuNCs and at the same time killing the tumor cells with the hydroxyl free radicals (∙OH) produced by the Fenton reaction between Fe 2+ and H 2 O 2 . This sequential dual-locked luminescent nanoprobe of CuNCs-Fe III @HA has been successfully used for the specific imaging and selective killing of tumor cells., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

The kinetic study of the gas-phase reactions of hydroxyl (OH) radicals and chlorine (Cl) atoms with CF 3 CHFCF 2 OCH 3 (HFE-356mec3) and CHF 2 CHFOCF 3 (HFE-236ea1) was performed by the pulsed laser photolysis/laser-induced fluorescence technique and a relative method by using Fourier Transform infrared (FTIR) spectroscopy as detection technique. The temperature dependences of the OH-rate coefficients (k OH (T) in cm 3 s -1 ) between 263 and 353 K are well described by the following expressions: 9.93 × 10 -13 exp{-(988 ± 35)/T}for HFE-356mec3 and 4.75 × 10 -13 exp{-(1285 ± 22)/T} for HFE-236ea1. Under NO x -free conditions, the rate coefficients k Cl at 298 K and 1013 mbar (760 Torr) of air were determined to be (2.30 ± 1.08) × 10 -13 cm 3 s -1 and (1.19 ± 0.10) × 10 -15 cm 3 s -1 , for HFE-356mec3 and HFE-236ea1, respectively. Additionally, the relative kinetic study of the Cl + CH 2 ClCHCl 2 reaction was investigated at 298 K, as it was used as a reference reaction in the kinetic study of the Cl-reaction with HFE-356mec3 and discrepant rate coefficients were found in the literature. The global atmospheric lifetimes were estimated relative to CH 3 CCl 3 at the tropospheric mean temperature (272 K) as 1.4 and 8.6 years for HFE-356mec3 and HFE-236ea1, respectively. These values combined with the radiative efficiencies for HFE-356mec3 and HFE-236ea1 derived from the measured IR absorption cross sections (0.27 and 0.41 W m -2 ppv -1 ) yield global warming potentials at a 100-yrs time horizon of 143 and 1473, respectively. The contribution of HFE-356mec3 and HFE-236ea1 to global warming of the atmosphere would be large if they become widespread increasing their atmospheric concentration., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

This study proposes a novel and eco-friendly approach for wastewater treatment using plasma jet technology under bubble condition. This method allows for the controlled production of highly reactive hydroxyl radicals (OH•) while minimizing unwanted interactions with nitrogen in the air. The presence of bubbles in liquid significantly boosts the diffusion of OH• within the wastewater, leading to a two-fold increase in degradation rate compared to normal condition. The effectiveness of the treatment was confirmed through ultraviolet-visible spectroscopy, which showed a significant decrease in rhodamine B and methyl orange absorbance peaks. Raman spectroscopy further revealed structural changes in both pollutants, indicating successful degradation. Additionally, plasma characteristics like power, electron temperature, and density were monitored to gain deeper insights into the underlying mechanism. Importantly, the process minimizes the formation of harmful secondary pollutants such as ozone and nitrogen oxides. These pollutants were found under concentration of 0.14 mg m -3 which is below established safety thresholds, adhering to World Health Organization guidelines. This research demonstrates that plasma jet treatment in bubble condition not only enhances the degradation efficiency of pollutants in wastewater but also minimizes the formation of harmful byproducts. This represents a significant breakthrough in developing sustainable wastewater treatment technologies., 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.)

Despite the vital roles of Fe 0 /biochar composites in the Fenton-like systems for eliminating pollutants that have been recognized, the contributions of persistent free radicals (PFRs) of carbon-based materials are typically overlooked. In this study, the high-PFR-containing biochar nanoiron composites were prepared (nZVI/500), and the in situ generation of hydroxyl radicals (·OH) and degradation of p-nitrophenol (PNP) were investigated. The results showed that nZVI/500 could effectively remove PNP in solution within the pH range of 3-8. Quantitative experiments of ·OH presented that, compared with low PFRs-containing composites, nZVI/500 could generate 64.6 µM ·OH in 60 min without any extra energy consumption. Mechanistic studies revealed that (1) both PFRs and Fe 0 are able to utilize dissolved oxygen to generate H 2 O 2 in situ; (2) PFRs can promote the cycling of Fe 3+ /Fe 2+ in the system due to their strong electron exchange ability; and (3) PFRs directly transfer electrons to H 2 O 2 ; therefore, the presence of PFRs accelerates the generation of ·OH in the system and facilitates the removal of PNP. This study provides an important theoretical basis and technical reference for expanding the application of PFR-rich carbon-based materials to remove environmental pollutants., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)