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The Science of the Total Environment May 2024In recent years, among many oxidation pathways studied for atmospheric sulfate formation, the aqueous phase oxidation pathways of HO and organic hydroperoxides (ROOHs)...
In recent years, among many oxidation pathways studied for atmospheric sulfate formation, the aqueous phase oxidation pathways of HO and organic hydroperoxides (ROOHs) have attracted great scientific attention. Higher concentrations of HO and ubiquitous ROOHs have been observed in atmospheric aqueous phase environments (cloud water, fog droplets, etc.). However, there are still some gaps in the study of their aqueous phase generation and their influences on sulfate formation. In this study, the aqueous phase photochemical reaction of methylglyoxal, a ubiquitous organic substance in the atmospheric aqueous phase, was studied under UV irradiation, and the generation of HO and ROOHs in this system was investigated. It is found for the first time that the aqueous phase photolysis of methylglyoxal not only produces HO but also produces ROOHs, and UV light and O are necessary for the formation of HO and ROOHs. Based on the experimental results, the possible mechanism of aqueous phase photochemistry of methylglyoxal and the generation of HO and ROOHs were proposed. The effect of aqueous phase photolysis of methylglyoxal on sulfate formation under different conditions was also investigated. The results show that the aqueous phase photolysis of methylglyoxal significantly promoted SO oxidation and sulfate formation, in which SO oxidation was realized by the generated HO, ROOHs and •OH radicals, and the importance of the formed ROOHs cannot be ignored. These results fill some gaps in the field of aqueous phase HO and ROOHs production, and to a certain extent confirm the important roles of the aqueous phase photolysis of methylglyoxal and the formed HO and ROOHs in the production of sulfate. The study reveals the new sources of HO and ROOHs, and provides a new insight into the heterogeneous aqueous phase oxidation pathways and mechanisms of SO in cloud and fog droplets and haze particles.
PubMed: 38460698
DOI: 10.1016/j.scitotenv.2024.171519 -
Environmental Science & Technology Nov 2023Krypton chloride (KrCl*) excimer ultraviolet (UV) light may provide advantages for contaminant degradation compared to conventional low-pressure (LP) UV. Direct and...
Krypton chloride (KrCl*) excimer ultraviolet (UV) light may provide advantages for contaminant degradation compared to conventional low-pressure (LP) UV. Direct and indirect photolysis as well as UV/hydrogen peroxide-driven advanced oxidation (AOP) of two chemical contaminants were investigated in laboratory grade water (LGW) and treated secondary effluent (SE) for LPUV and filtered KrCl* excimer lamps emitting at 254 and 222 nm, respectively. Carbamazepine (CBZ) and -nitrosodimethylamine (NDMA) were chosen because of their unique molar absorption coefficient profiles, quantum yields (QYs) at 254 nm, and reaction rate constants with hydroxyl radical. Quantum yields and molar absorption coefficients at 222 nm for both CBZ and NDMA were determined, with measured molar absorption coefficients of 26 422 and 8170 M cm, respectively, and QYs of 1.95 × 10 and 6.68 × 10 mol Einstein, respectively. The 222 nm irradiation of CBZ in SE improved degradation compared to that in LGW, likely through promotion of in situ radical formation. AOP conditions improved degradation of CBZ in LGW for both UV LP and KrCl* sources but did not improve NDMA decay. In SE, photolysis of CBZ resulted in decay similar to that of AOP, likely due to the in situ generation of radicals. Overall, the KrCl* 222 nm source significantly improves contaminant degradation compared to that of 254 nm LPUV.
Topics: Dimethylnitrosamine; Water Pollutants, Chemical; Oxidation-Reduction; Carbamazepine; Ultraviolet Rays; Photolysis; Hydrogen Peroxide; Water Purification
PubMed: 37186817
DOI: 10.1021/acs.est.3c00703 -
Chemosphere Mar 2024Using methods of time-resolved and stationary photolysis, HPLC-MS and quantum-chemical calculations by the DFT method, the mechanism of direct UV photolysis of the...
Laser flash photolysis and quantum chemical studies of UV degradation of pharmaceutical drug chloramphenicol: Short-lived intermediates, quantum yields and mechanism of photolysis.
Using methods of time-resolved and stationary photolysis, HPLC-MS and quantum-chemical calculations by the DFT method, the mechanism of direct UV photolysis of the antibiotic chloramphenicol (CAP) was established. For the first time, short-lived intermediates formed during photolysis were detected. The primary photoprocess is the cleavage of the β-C-C bond relative to the aromatic system with the formation of 4-nitrobenzylalcohol radical and residual aliphatic radical. The first radical in deoxygenated solutions predominantly transforms into para-nitrobenzaldehyde and its secondary photolysis products. In the presence of oxygen, the aromatic radical and para-nitrobenzaldehyde are transformed into para-nitrosobenzoic and para-nitrobenzoic acids as a result of reaction with reactive oxygen species (ROS). Formation of ROS is provoked by reactions of aliphatic radical with dissolved oxygen, so this radical is very important for CAP degradation. The quantum yield of direct photolysis of CAP is ∼3% and does not depend on the presence of dissolved oxygen and on the change of the excitation wavelength in the range of 254-308 nm. Obtained data are important for further understanding of the transformation pathways of CAP and similar PPCP in natural and wastewaters under the action of sunlight and artificial UV radiation.
Topics: Ultraviolet Rays; Photolysis; Reactive Oxygen Species; Chloramphenicol; Oxygen; Pharmaceutical Preparations; Lasers; Water Pollutants, Chemical; Kinetics; Benzaldehydes
PubMed: 38219992
DOI: 10.1016/j.chemosphere.2024.141211 -
The Journal of Organic Chemistry Jul 2023The photolysis of 2-azidofluorene in solid argon at 3 K results in the formation of 2-fluorenylnitrene. The nitrene undergoes subsequent rearrangements to two isomeric... (Review)
Review
The photolysis of 2-azidofluorene in solid argon at 3 K results in the formation of 2-fluorenylnitrene. The nitrene undergoes subsequent rearrangements to two isomeric didehydroazepines (ketenimines) which differ in the position of the N atom in the seven-membered ring. The rearrangement of the nitrene to the didehydroazepines proceeds in a two-step process. The first step is a photochemical rearrangement to form the corresponding isomeric benzazirines and . The second step is the opening of the three-membered rings of and to form the isomeric didehydroazepines. While benzazirine could easily be detected, isomer was not observed, despite the corresponding didehydroazepine being formed in the matrix. Further experiments revealed that rearranges to the didehydroazepine via heavy-atom tunneling. Semiquantitative estimations based on DFT calculations confirm that should undergo a tunneling rearrangement with tunneling rates on the order of the experimentally observed rates. In contrast, estimations for suggest that for this isomer the tunneling rates should be much larger, resulting in lifetimes too short to be observable under the conditions of matrix isolation. These experiments demonstrate the influence of position isomerism on quantum tunneling rates.
Topics: Isomerism; Imines; Photolysis
PubMed: 37204141
DOI: 10.1021/acs.joc.3c00484 -
Nature Materials Jun 2024
PubMed: 38834730
DOI: 10.1038/s41563-024-01879-z -
Journal of Hazardous Materials Feb 2024We investigated the degradation of hexafluoropropylene oxide dimer acid (GenX) in water via VUV photolysis and VUV/sulfite reactions under nitrogen-saturated conditions....
We investigated the degradation of hexafluoropropylene oxide dimer acid (GenX) in water via VUV photolysis and VUV/sulfite reactions under nitrogen-saturated conditions. Approximately 35% and 90% of GenX were degraded in 3 h in the VUV photolysis and VUV/sulfite reaction. While GenX removal rate was highest at pH 6 in VUV photolysis, it increased under alkaline pHs, especially at pH 10, in VUV/sulfite reaction. Radical scavenging experiments showed that, while both e and •H contributed to VUV photolysis, e played a significant role and •OH had a negative effect during VUV/sulfite reaction. Two transformation products (TPs) (TFA and PFPrA) were identified in VUV photolysis, whereas five TPs (TFA, PFPrA, TP182, TP348, and TP366) were identified in VUV/sulfite reaction by LCMS/MS and LCQTOF/MS. Defluorination of GenX was observed with the defluorination efficiency after 6 h reaching 17% and 67% in the VUV photolysis and VUV/sulfite reactions, respectively. Degradation mechanism for GenX based on the identified TPs and the theoretical calculation confirmed the susceptibility of GenX to nucleophilic attack. The initial reactions for GenX decomposition were C-C and C-O bond cleavage in both reactions, whereas sulfonation followed by decarboxylation was observed only in the VUV/sulfite reaction. ECOSAR ecotoxicity simulation showed that the toxicities of the TPs were not as harmful as those of GenX.
PubMed: 37907009
DOI: 10.1016/j.jhazmat.2023.132864 -
Journal of Hazardous Materials Feb 2024Organic ultraviolet filters (OUVFs) have been used globally for the past 20 years. Given that OUVFs can be quickly released from sunscreens applied on human skins, they... (Review)
Review
Organic ultraviolet filters (OUVFs) have been used globally for the past 20 years. Given that OUVFs can be quickly released from sunscreens applied on human skins, they have been frequently detected in aquatic environments and organisms. Some byproducts of OUVFs might be more recalcitrant and toxic than their parent compounds. To further assess the toxicity and potential risk of OUVFs' byproducts, it is necessary to determine the fate of OUVFs and identify their transformation products. This review summarizes and analyzes pertinent literature and reports in the field of OUVFs research. These published research works majorly focus on the degradation mechanisms of OUVFs in aquatic environments, their intermediates/byproducts, and chlorination reaction. Photodegradation (direct photolysis, self-sensitive photolysis and indirect photolysis) and biodegradation are the main transformation pathways of OUVFs through natural degradation. To remove residual OUVFs' pollutants from aqueous environments, novel physicochemical and biological approaches have been developed in recent years. Advanced oxidation, ultrasound, and bio-based technologies have been proven to eliminate OUVFs from wastewaters. In addition, the disinfection mechanism and the byproducts (DBPs) of various OUVFs in swimming pools are discussed in this review. Besides, knowledge gaps and future research directions in this field of study are also mentioned.
Topics: Humans; Water; Water Pollutants, Chemical; Ultraviolet Rays; Sunscreening Agents; Disinfection; Photolysis; Water Purification
PubMed: 37898090
DOI: 10.1016/j.jhazmat.2023.132822 -
Angewandte Chemie (International Ed. in... Oct 2023Cellular membranes, including the plasma and endosome membranes, are barriers to outside proteins. Various vehicles have been devised to deliver proteins across the...
Cellular membranes, including the plasma and endosome membranes, are barriers to outside proteins. Various vehicles have been devised to deliver proteins across the plasma membrane, but in many cases, the payload gets trapped in the endosome. Here we designed a photo-responsive phase-separating fluorescent molecule (PPFM) with a molecular weight of 666.8 daltons. The PPFM compound condensates as fluorescent droplets in the aqueous solution by liquid-liquid phase separation (LLPS), which disintegrate upon photoirradiation with a 405 nm light-emitting diode (LED) lamp within 20 min or a 405 nm laser within 3 min. The PPFM coacervates recruit a wide range of peptides and proteins and deliver them into mammalian cells. Photolysis disperses the payload from condensates into the cytosolic space. Altogether, a type of small molecules that are photo-responsive and phase separating are discovered; their coacervates can serve as transmembrane vehicles for intracellular delivery of proteins, whereas photo illumination triggers the cytosolic distribution of the payload.
Topics: Cell Membrane; Peptides; Photolysis; Light
PubMed: 37648812
DOI: 10.1002/anie.202307045 -
Environmental Pollution (Barking, Essex... Oct 2023The degradation kinetics and transformation products of pharmaceutical azole drugs from Watch List 2020/1161 (fluconazole, FCZ; miconazole, MCZ; clotrimazole, CTZ; and...
The degradation kinetics and transformation products of pharmaceutical azole drugs from Watch List 2020/1161 (fluconazole, FCZ; miconazole, MCZ; clotrimazole, CTZ; and sulfamethoxazole, SMX) are examined individually and as a mixture in Milli-Q water and simulated wastewater (SWW) upon treatment with three different advanced oxidation processes: (i) photolysis (UV), (ii) electrochemical (eAOP), and (iii) photoelectrochemical (eAOP/UV). For individual pollutant degradation, UV was found to be significantly more effective for SMX and CTZ compared to MCZ and FCZ. Whereas when treating the azole drugs mixture, eAOP/UV was determined to be the most effective treatment method. The degradation efficiency was higher in Milli-Q than in SWW because the treatment efficiency depended on the matrix compositions. The degradation products formed under different processes were identified, and the routes of transformation were proposed. The results of this study can assist in the selection of the most suitable treatment technology depending upon the pollutant or matrix.
Topics: Azoles; Photolysis; Kinetics; Water Pollutants, Chemical; Anti-Infective Agents; Oxidation-Reduction; Sulfamethoxazole; Ultraviolet Rays; Hydrogen Peroxide
PubMed: 37467915
DOI: 10.1016/j.envpol.2023.122220 -
Angewandte Chemie (International Ed. in... Nov 2023The synthesis of polymers with high molecular weights, controlled sequence, and tunable dispersities remains a challenge. A simple and effective visible-light controlled...
The synthesis of polymers with high molecular weights, controlled sequence, and tunable dispersities remains a challenge. A simple and effective visible-light controlled photoiniferter reversible addition-fragmentation chain transfer (RAFT) polymerization is reported here to realize this goal. Key to this strategy is the use of switchable RAFT agents (SRAs) to tune polymerization activities coupled with the inherent highly living nature of photoiniferter RAFT polymerization. The polymerization activities of SRAs were in situ adjusted by the addition of acid. In addition to a switchable chain-transfer coefficient, photolysis and polymerization kinetic studies revealed that neutral and protonated SRAs showed different photolysis and polymerization rates, which is unique to photoiniferter RAFT polymerization in terms of dispersity control. This strategy features no catalyst, no exogenous radical source, temporal regulation by visible light, and tunable dispersities in the unprecedented high molecular weight regime (up to 500 kg mol ). Pentablock copolymers with three different dispersity combinations were also synthesized, highlighting that the highly living nature was maintained even for blocks with large dispersities. T was lowered for high-dispersity polymers of similar MWs due to the existence of more low-MW polymers. This strategy holds great potential for the synthesis of advanced materials with controlled molecular weight, dispersity and sequence.
PubMed: 37814139
DOI: 10.1002/anie.202314729