Contribution of the Excited Triplet State of Humic Acid and Superoxide Radical Anion to Generation and Elimination of Phenoxyl Radical

Chen, Yuan; Zhang, Xu; Su, Feng

doi:10.1021/acs.est.8b00890

Cited by 48 publications

(27 citation statements)

References 61 publications

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“…These observations call for a detailed examination of the role of superoxide, and possibly further transient reducing species formed under irradiation of DOM, in aquatic photochemistry. 43 The modest results obtained in the present study for sulfadiazine preclude a prediction of the inhibitory effect on its photosensitized transformation, because the rate constants of the corresponding intermediate radical are missing. The example of sulfadiazine demonstrates that laser flash photolysis is not always a suitable tool to understand and predict the inhibitory effect of phenols and DOM on the indirect phototransformation of relevant aquatic contaminants.…”

Section: Environmental Implicationsmentioning

confidence: 70%

Quenching of an Aniline Radical Cation by Dissolved Organic Matter and Phenols: A Laser Flash Photolysis Study

Leresche

Ludvíková

Heger

et al. 2020

Environ. Sci. Technol.

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Aromatic amines are relevant aquatic organic contaminants whose photochemical transformation is affected by dissolved organic matter (DOM). The goal of this study is to elucidate the underlying mechanism of the inhibitory effect of DOM on such reactions. The selected model aromatic amine, 4-(dimethylamino)benzonitrile (DMABN), was submitted to laser flash photolysis in the presence and absence of various model photosensitizers. The produced radical cation (DMABN •+ ) was observed to react with several phenols and different types of DOM on a time scale of ∼100 µs. The determined second-order rate constants for the quenching of DMABN •+ by phenols were in the range of (1.4 -26) × 10 8 M −1 s −1 and increased with increasing electron donor character of the aromatic ring substituent. For DOM, quenching rate constants increased with the phenolic content of the DOM. These results indicate the reduction of DMABN •+ to re-form its parent compound as the basic reaction governing the inhibitory effect. In addition, the photosensitized oxidation of the sulfonamide antibiotic sulfadiazine (SDZ) was studied. The observed radical intermediate of SDZ was quenched by 4-methoxyphenol less effectively than DMABN •+ , which was attributed to the lower reduction potential of this radical compared to DMABN •+ .

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Section: Environmental Implicationsmentioning

confidence: 70%

Quenching of an Aniline Radical Cation by Dissolved Organic Matter and Phenols: A Laser Flash Photolysis Study

Leresche

Ludvíková

Heger

et al. 2020

Environ. Sci. Technol.

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“…The effective concentration 435 of O 2 ⦁-, therefore, increases at higher pH, potentially explaining the faster EBS photodegradation 436 kinetics in RB-sensitized solutions at high pH. This hypothesis is supported by results from Chen 437 et al54 , who reported that a one-electron transfer mechanism for acetaminophen with O 2 ⦁was 1.1× faster at pH 10.0 than at pH 8.0. Given the faster EBS photodegradation kinetics at higher pH, the contribution of H 2 O 2 generated through O 2 ⦁self-dismutation to EBS degradation was negligible.Overall, the reported data suggest that investigation of the environmental photochemistry of organoselenium chemicals requires careful consideration of the protocols used to identify transformation mechanisms and calculate rate constants.…”

mentioning

confidence: 74%

Photochemistry of the Organoselenium Compound Ebselen: Direct Photolysis and Reaction with Active Intermediates of Conventional Reactive Species Sensitizers and Quenchers

Hopanna

Kelly

Blaney

2020

Environ. Sci. Technol.

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Ebselen (EBS), 2-phenyl-1,2-benzisoselenazol-3(2H)-one, is an organoselenium pharmaceutical with antioxidant and anti-inflammatory properties. Furthermore, EBS is an excellent scavenger of reactive oxygen species. This property complicates conventional protocols for sensitizing and quenching reactive species due to potential generation of active intermediates that quickly react with EBS. In this study, the photochemical reactivity of EBS was investigated in the presence of (1) 1 O 2 and • OH sensitizers (Rose Bengal (RB), perinaphthanone, H 2 O 2 ) and (2) reactive species scavenging and quenching agents (sorbic acid, isopropanol, sodium azide, tert-butanol) that are commonly employed to study photodegradation mechanisms and kinetics. The carbon analog of EBS, namely 2-phenyl-3H-isoindol-1-one, was included as a reference compound to confirm the impact of the selenium atom on EBS photochemical reactivity. EBS does not undergo acid dissociation, but pH-dependent kinetics were observed in RB-sensitized solutions, suggesting EBS reaction with active intermediates ( 3 RB 2-*, O 2 ⦁-, H 2 O 2 ) that are not kinetically-relevant for 38 other compounds. In addition, the observed rate constant of EBS increased in the presence of 39 sorbic acid, isopropanol, and sodium azide. These findings suggest that conventional reactive 40 species sensitizers, scavengers, and quenchers need to be carefully applied to highly reactive 41 organoselenium compounds to account for reactions that are typically slow for other organic 42 contaminants. 43

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“…Atmospheric chromophoric organic matter (COM) is an important component of biomass combustion emissions and secondary organic aerosol (SOA) (Andreae and Gelencser, 2006;Budisulistiorini et al, 2017;Graber and Rudich, 2006;Zappoli et al, 1999). COM has a significant absorption in the near-ultraviolet and visible region (Rosario-Ortiz and Canonica, 2016;Cheng et al, 2016), and photochemistry of COM has a significant impact on air quality (Zhao et al, 2013;Jo et al, 2016). Therefore, simulation and evaluation of COM photochemistry are both necessary for understanding aerosol aging.…”

Section: Introductionmentioning

confidence: 99%

Photodegradation of atmospheric chromophores: changes in oxidation state and photochemical reactivity

Chen

Zhang

et al. 2021

Atmos. Chem. Phys.

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Abstract. Atmospheric chromophoric organic matter (COM) plays a fundamental role in photochemistry and aerosol aging. However, the effects of photodegradation on chemical components and photochemical reactivity of COM remain unresolved. Here, we report the potential effects of photodegradation on carbon contents, optical properties, fluorophore components and photochemical reactivity in aerosol. After 7 d of photodegradation, fluorescent intensity and the absorption coefficient of COM decrease by 71.4 % and 32.0 %, respectively. Photodegradation makes a difference to the chemical component of chromophore and the degree of aerosol aging. Low-oxidation humic-like substance (HULIS) is converted into high-oxidation HULIS due to photooxidation. Photodegradation also changes the photochemical reactivity. The generation of triplet-state COM (3COM*) decreases slightly in ambient particulate matter (ambient PM) but increases in primary organic aerosol (POA) following photodegradation. The results highlight that the opposite effect of photodegradation on photochemical reactivity in POA and ambient PM. However, the generation of singlet-oxygen (1O2) decreases obviously in POA and ambient PM, which could be attributed to photodegradation of precursors of 1O2. The combination of optical property, chemical component and reactive oxygen species has an important impact on the air quality. The new insights on COM photodegradation in aerosol reinforce the importance of studying dissolved organic matter (DOM) related with the photochemistry and aerosol aging.

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Contribution of the Excited Triplet State of Humic Acid and Superoxide Radical Anion to Generation and Elimination of Phenoxyl Radical

Cited by 48 publications

References 61 publications

Quenching of an Aniline Radical Cation by Dissolved Organic Matter and Phenols: A Laser Flash Photolysis Study

Quenching of an Aniline Radical Cation by Dissolved Organic Matter and Phenols: A Laser Flash Photolysis Study

Photochemistry of the Organoselenium Compound Ebselen: Direct Photolysis and Reaction with Active Intermediates of Conventional Reactive Species Sensitizers and Quenchers

Photodegradation of atmospheric chromophores: changes in oxidation state and photochemical reactivity

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