Analytical method development, identification, and characterization of stress degradation products of idelalisib by ultrahigh-performance liquid chromatography with photodiode array and ultrahigh-performance liquid chromatography with electrospray ionization quadrupole time-of-flight mass spectrometry studies.

RATIONALE: As per International Council for Harmonization (ICH) drug stability test guideline Q1A(R2), inherent stability characteristics of a drug should be studied. This work was designed to investigate inherent degradation characteristics of the drug idelalisib under ICH prescribed stress conditions, identify its degradation products, and postulate their corresponding degradation pathways. METHODS: Idelalisib was subjected to the ICH prescribed conditions of hydrolytic (neutral, acidic, and alkaline), photolytic, oxidative, and thermal stress according to ICH guideline Q1A(R2). An ultrahigh-performance liquid chromatography with photodiode array (UHPLC-PDA) method was developed to adequately resolve the drug from its degradation products, validated as per the ICH guidelines, and subsequently extended to UHPLC with electrospray ionization quadrupole time-of-flight mass spectrometry (ESI-QTOFMS) studies to identify the degradation products. RESULTS: Significant degradation was noted under conditions of acidic/alkaline hydrolysis, acid photolysis, and oxidative stress. The UHPLC/ESI-QTOFMS studies revealed the generation of four degradation products (I-IV), which were satisfactorily resolved from the drug by UHPLC on a Kinetex® C18 (100 × 4.6 mm; 2.6 µm) column by the developed isocratic elution method. Detection wavelength was selected as 270 nm. All the degradation products (I-IV) could be identified and characterized from their mass spectral data. The degradation pathways for the generation of various products from the drug were postulated. CONCLUSIONS: A UHPLC-PDA method was developed and validated for idelalisib. Four degradation products of idelalisib were revealed through UHPLC/ESI-QTOFMS studies, and corresponding degradation pathways were postulated for the same.

Simultaneous determination of folic acid photolysis products and oxidized guanine derivatives in plasma by liquid chromatography-tandem mass spectrometry.

Folic acid (FA) is easily photodegraded to yield 6-formylpterin and pterin-6-carboxylic acid, which can generate reactive oxygen species and result in the formation of oxidized guanine derivatives such as 8-hydroxy-2'-deoxyguanosine and 8-hydroxy-guanosine. In this study, we developed a simple, rapid, and sensitive liquid chromatography-tandem mass spectrometry strategy for the simultaneous determination of FA photolysis products and oxidized guanine derivatives in plasma samples. Chromatographic separation was performed on a Waters HSS T3 column (2.1 × 100 mm, 5.0 µm) with gradient elution at a flow rate of 0.25 mL/min. Plasma samples were first pretreated with 1% formic acid, followed by protein precipitation with methanol. The developed method showed good linear relationships between 1 and 2000 ng/mL (r2 > 0.99). The intra- and inter-day precisions ranged from 2.6% to 7.5% and from 2.5% to 6.5%, respectively. Recoveries of the analytes were between 75.4% and 112.4% with the relative standard deviation < 9.1%. Finally, the method was applied to quantify FA photolysis products and oxidized guanine derivatives in rats with light and non-light conditions.

Theoretical insights of the pharmaceutical compound fluoxetine in water: Role in direct photolysis and indirect photolysis by free radicals.

The frequent detection of pharmaceutical compounds in the environment has led to a growing awareness, which may pose a major threat to the aquatic environment. In this study, photodegradation (direct and indirect photolysis) of two different dissociation states of fluoxetine (FLU) was investigated in water, mainly including the determination of photolytic transition states and products, and the mechanisms of indirect photodegradation with ·OH, CO3*- and NO3*. The main direct photolysis pathways are defluorination and C-C bond cleavage. In addition, the indirect photodegradation of FLU in water is mainly through the reactions with ·OH and NO3*, and the photodegradation reaction with CO3*- is relatively difficult to occur in the water environment. Our results provide a theoretical basis for understanding the phototransformation process of FLU in the water environment and assessing its potential risk.

Three-dimensional donor-acceptor conjugated porous polymers based on metal-porphyrin and triazine for highly effective photodegradation of organic pollutants in water.

Three-dimensional donor-acceptor (D-A) type conjugated porous polymers (CPPs) was designed and synthesized via imine condensation of copper tetraaminoporphyrin (CuTAPP) as donor and 1,3,5-tris-(4-formyl phenyl) triazine (TFPT) as acceptor, named as CuPT-CPP. The CuPT-CPP possesses a high specific surface area (73.7 m2/g) and excellent photophysical properties. The simultaneous introduction of the organometallic molecules and D-A structures in CuPT-CPP could be broadened the visible-light response range (400-800 nm) and facilitated efficient photogenerated carrier separation and transportation. As heterogeneous photocatalysts, CuPT-CPP has excellent photocatalytic performances under visible light irradiation, leading to excellent model pollutant rhodamine B degradation efficiency up to about 100% in 3 h, it has superb stability and reusability during the photocatalytic processes, and CuPT-CPP also exhibited broad substrate adaptability, which could photocatalytic degradation of methylene blue (MB), methyl orange (MO), and tetracycline hydrochloride (TC). This work indicates that three-dimensional D-A type porphyrin- and triazine-based CuPT-CPP has great potential in the practical application of photocatalysis.

Estrogenic disruption effects and formation mechanisms of transformation products during photolysis of preservative parabens.

The ubiquitous presence of emerging contaminants (ECs) in the environment and their associated adverse effects has raised concerns about their potential risks. The increased toxicity observed during the environmental transformation of ECs is often linked to the formation of their transformation products (TPs). However, comprehension of their formation mechanisms and contribution to the increased toxicity remains an unresolved challenge. To address this gap, by combining quantum chemical and molecular simulations with photochemical experiments in water, this study investigated the formation of TPs and their molecular interactions related to estrogenic effect using the photochemical degradation of benzylparaben (BZP) preservative as a representative example. A non-targeted analysis was carried out and three previously unknown TPs were identified during the transformation of BZP. Noteworthy, two of these novel TPs, namely oligomers BZP-o-phenol and BZP-m-phenol, exhibited higher estrogenic activities compared to the parent BZP. Their IC50 values of 0.26 and 0.50 µM, respectively, were found to be lower than that of the parent BZP (6.42 µM). The binding free energies (ΔGbind) of BZP-o-phenol and BZP-m-phenol (-29.71 to -23.28 kcal·mol-1) were lower than that of the parent BZP (-20.86 kcal·mol-1), confirming their stronger binding affinities toward the estrogen receptor (ER) α-ligand binding domain. Subsequent analysis unveiled that these hydrophobic residues contributed most favorably to ER binding, with van der Waals interactions playing a significant role. In-depth examination of the formation mechanisms indicated that these toxic TPs primarily originated from the successive cleavage of ester bonds (OCH2C6H5 and COO group), followed by their combination with BZP*. This study provides valuable insight into the mechanisms underlying the formation of toxic TPs and their binding interactions causing the endocrine-disrupting effects. It offers a crucial framework for elucidating the toxicological patterns of ECs with similar structures.

Reassessing the Quantum Yield and Reactivity of Triplet-State Dissolved Organic Matter via Global Kinetic Modeling.

Measuring the quantum yield and reactivity of triplet-state dissolved organic matter (3DOM*) is essential for assessing the impact of DOM on aquatic photochemical processes. However, current 3DOM* quantification methods require multiple fitting steps and rely on steady-state approximations under stringent application criteria, which may introduce certain inaccuracies in the estimation of DOM photoreactivity parameters. Here, we developed a global kinetic model to simulate the reaction kinetics of the hv/DOM system using four DOM types and 2,4,6-trimethylphenol as the probe for 3DOM*. Analyses of residuals and the root-mean-square error validated the exceptional precision of the new model compared to conventional methods. 3DOM* in the global kinetic model consistently displayed a lower quantum yield and higher reactivity than those in local regression models, indicating that the generation and reactivity of 3DOM* have often been overestimated and underestimated, respectively. The global kinetic model derives parameters by simultaneously fitting probe degradation kinetics under different conditions and considers the temporally increasing concentrations of the involved reactive species. It minimizes error propagation and offers insights into the interactions of different species, thereby providing advantages in accuracy, robustness, and interpretability. This study significantly advances the understanding of 3DOM* behavior and provides a valuable kinetic model for aquatic photochemistry research.

Far-UVC Photolysis of Peroxydisulfate for Micropollutant Degradation in Water.

Increasing radical yields to reduce UV fluence requirement for achieving targeted removal of micropollutants in water would make UV-based advanced oxidation processes (AOPs) less energy demanding in the context of United Nations' Sustainable Development Goals and carbon neutrality. We herein demonstrate that, by switching the UV radiation source from conventional low-pressure UV at 254 nm (UV254) to emerging Far-UVC at 222 nm (UV222), the fluence-based concentration of HO• in the UV/peroxydisulfate (UV/PDS) AOP increases by 6.40, 2.89, and 6.00 times in deionized water, tap water, and surface water, respectively, with increases in the fluence-based concentration of SO4•- also by 5.06, 5.81, and 55.47 times, respectively. The enhancement to radical generation is confirmed using a kinetic model. The pseudo-first-order degradation rate constants of 16 micropollutants by the UV222/PDS AOP in surface water are predicted to be 1.94-13.71 times higher than those by the UV254/PDS AOP. Among the tested water matrix components, chloride and nitrate decrease SO4•- but increase HO• concentration in the UV222/PDS AOP. Compared to the UV254/PDS AOP, the UV222/PDS AOP decreases the formation potentials of carbonaceous disinfection byproducts (DBPs) but increases the formation potentials of nitrogenous DBPs.

Hydrothermal-assisted synthesis of Sr-doped SnS nanoflower catalysts for photodegradation of metronidazole antibiotic pollutant in wastewater promoted by natural sunlight irradiation.

In this study, we report a facile hydrothermal synthesis of strontium-doped SnS nanoflowers that were used as a catalyst for the degradation of antibiotic molecules in water. The prepared sample was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible absorption spectroscopy (UV-Vis). The photocatalytic ability of the strontium-doped SnS nanoflowers was evaluated by studying the degradation of metronidazole in an aqueous solution under photocatalytic conditions. The degradation study was conducted for a reaction period of 300 min at neutral pH, and it was found that the degradation of metronidazole reached 91%, indicating the excellent photocatalytic performance of the catalyst. The influence of experimental parameters such as catalyst dosage, initial metronidazole concentration, initial reaction pH, and light source nature was optimized with respect to metronidazole degradation over time. The reusability of the strontium-doped SnS nanoflowers catalyst was investigated, and its photocatalytic efficiency remained unchanged even after four cycles of use.

Study of the impurity profile of photodegradation in lomefloxacin hydrochloride ear drops using liquid chromatography combined with ion trap/time-of-flight mass spectrometry.

RATIONALE: Lomefloxacin hydrochloride ear drops are highly unstable to light and prone to produce photodegradation impurities. These impurities might be related to the phototoxicity of lomefloxacin, which could seriously threaten the health of patients. In this article, the photodegradation impurity profile in lomefloxacin hydrochloride ear drops was studied for further improvement of quality control of the drug. METHODS: By studying the chromatographic behavior of photodegradation impurities, the photodegradation impurities in lomefloxacin hydrochloride ear drops were separated and detected effectively. Liquid chromatography combined with ion trap/time-of-flight mass spectrometry was applied to characterize the structures of the photodegradation impurities in lomefloxacin hydrochloride ear drops. RESULTS: The structures of 17 impurities in lomefloxacin hydrochloride ear drops were elucidated based on high-resolution MSn data in positive ion mode, 12 of them being unknown impurities. CONCLUSIONS: The structural characteristics and fragmentation patterns of the photodegradation impurities were also studied. The study of the photodegradation impurity profile in lomefloxacin hydrochloride ear drops provides a scientific basis for quality control of these ear drops and ensures the safety of drug use by the public.

Analysis of pharmacokinetic profile and ecotoxicological character of cefepime and its photodegradation products.

An important problem is the impact of photodegradation on product toxicity in biological tests, which may be complex and context-dependent. Previous studies have described the pharmacology of cefepime, but the toxicological effects of its photodegradation products remain largely unknown. Therefore, photodegradation studies were undertaken in conditions similar to those occurring in biological systems insilico, in vitro, in vivo and ecotoxicological experiments. The structures of four cefepime photodegradation products were determined by UPLC-MS/MS method. The calculated in silico ADMET profile indicates that carcinogenic potential is expected for compounds CP-1, cefepime, CP-2 and CP-3. The Cell Line Cytomotovity Predictor 2.0 tool was used to predict the cytotoxic effects of cefepime and related compounds in non-transformed and cancer cell lines. The results indicate that possible actions include: non-small cell lung cancer, breast adenocarcinoma, prostate cancer and papillary renal cell carcinoma. OPERA models were used to predict absorption, distribution, metabolism and excretion (ADME) endpoints, and potential bioactivity of CP-2, cefepime and CP-4. The results obtained in silico show that after 96h of exposure, cefepime, CP-1, CP-2, and CP-3 are moderately toxic in the zebrafish model, while CP-4 is highly toxic. On the contrary, cefepime is more toxic to T. platyurus (highly toxic) compared to the zebrafish model, similar to products CP-4, CP-3 and CP-2. In vitro cytotoxicity studies were performed by MTT assay and in vivo acute embryo toxicity studies using Danio rerio embryos and larvae. In vitro showed an increase in the cytotoxicity of products with the longest exposure period i.e. for 8 h. Additionally, at a concentration of 200 µg/mL, statistically significant changes in metabolic activity were observed depending on the irradiation time. In vivo studies conducted with Zebrafish showed that both cefepime and its photodegradation products have only low toxicity. Assessment of potential ecotoxicity included Microbiotests on invertebrates (Thamnotoxkit F and Daphtoxkit F), and luminescence inhibition tests (LumiMara). The observed toxicity of the tested solutions towards both Thamnocephalus platyurus and Daphnia magna indicates that the parent substance (unexposed) has lower toxicity, which increases during irradiation. The acute toxicity (Lumi Mara) of nonirradiated cefepime solution is low for all tested strains (<10%), but mixtures of cefepime and its photoproducts showed growth inhibition against all tested strains (except #6, Photobacterium phoreum). Generally, it can be concluded that after UV-Vis irradiation, the mixture of cefepime phototransformation products shows a significant increase in toxicity.

Efficient visible light-driven photodegradation of glyphosate utilizing Bi2WO6 with oxygen vacancies: Performance, mechanism, and toxicity assessment.

Global environmental deterioration poses a major risk to ecological security and human health, and emerging technologies are urgently needed to deal with it. Therefore, the exploitation of photocatalysts with favorable activity for efficient degradation of pesticide contaminants is one of the strategies to achieve environmental remediation. Herein, oxygen vacancy-rich Bi2WO6 (Ov-BWO) was prepared through a solvothermal method utilizing ethylene glycol (EG), which exhibited excellent photocatalytic efficiency in photodegradation of glyphosate. The formation of oxygen vacancies (Ovs) in Ov-BWO was demonstrated utilizing XPS and EPR. PL, TRPL, photocurrent tests, and EIS analyses revealed that Ovs accelerated effective transfer of photogenerated charge, extended lifetime of charge carriers, promoted production of active species and significantly improved the photocatalytic performance. Compared with the low-activity Bi2WO6 (BWO, 59.6%), Ov-BWO showed outstanding photocatalytic activity, achieving a degradation efficiency of 91% for glyphosate at 120 min of visible light irradiation. Moreover, Ov-BWO also displayed outstanding recyclable stability after four repeated uses. Based on the characterization of photoelectric properties, a feasible photocatalytic reaction was put forth, along with glyphosate degradation pathways. Furthermore, the degradation intermediates of glyphosate were analyzed in detail employing HPLC-MS. The toxicity assessment indicated that degraded products had been proven to be non-toxic to the ecological system. This work presents the potential of photocatalysts with Ovs for the photodegradation of pesticides, providing a viable strategy for environmental renovation.

Mn3O4/ZnO-Al2O3-CeO2 mixed oxide catalyst derived from Mn-doped Zn-(Al/Ce)-LDHs: efficient visible light photodegradation of clofibric acid in water.

Mn3O4/ZnO-Al2O3-CeO2 catalyst was synthesized through a solid-state process from a 3% Mn-doped Zn-(Al/Ce) layered double hydroxide structure. Detailed structural and optical characterization using XRD, FTIR, UV-visible DRS, and TEM was conducted. By investigating clofibric acid (CA) degradation in aqueous solution, Mn3O4/ZnO-Al2O3-CeO2 photocatalytic activity was evaluated. The results show that the heterostructure mixed oxide catalyst has excellent CA photodegradation performance. Further, the characterization reveals that such photocatalytic efficiency can be attributed to two facts that are summarized in the optical properties and the synergic effect between Mn and Ce elements. The sample demonstrated a narrow band gap of 2.34 eV based on DRS. According to the experimental results of the photodegradation, after 120 min of irradiation, the photocatalyst exhibited the highest photocatalytic activity, with a degradation efficiency of 93.6%. Optimization outcomes indicated that maximum degradation efficiency was attained under the following optimum conditions: catalyst dose of 0.3 g/L, initial dye concentration of 20 mg/L, pH 3.86, and 120 min of reaction time. The quenching test demonstrates that photogenerated electrons and superoxide radicals are the most powerful reactive species. The catalyst could be useful in decreasing the photogenerated charges recombination, which offers more redox cycles simultaneously during the catalytic process. The strong Ce-Mn interaction and the formation of their different oxidation states offer a high degradation efficiency by facilitating electron-hole transfer. The introduction of Mn3O4 in the catalyst can effectively improve the visible absorption properties, which are beneficial in the photocatalytic process by reaching a high catalytic efficiency at a low cost.

Fe2+-NTA synergized UV254 photolytic defluorination of perfluorooctane sulfonate (PFOS): Enhancing through intramolecular electron density perturbation via electron acquisition.

Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant posing a risk in environmental persistence, bioaccumulation and biotoxicity. This study was to reach a comprehensive and deeper understanding of PFOS elimination in a UV254 photolytic treatment with the co-presence of Fe2+ and nitrilotriacetic acid trisodium salt (NTA). PFOS defluorination was noticeably enhanced in the UV/Fe2+-NTA treatment compared with UV/NTA, UV/Fe2+ and our previously studied UV/Fe3+ treatments. UV-vis, FTIR, and UPLC/MS-MS results indicated the formation of PFOS-Fe2+-NTA complex in PFOS, Fe2+ and NTA mixture. The transition energy gap of PFOS-Fe2+-NTA decreased below the excitation energy supplied by UV254 irradiation, corresponding with red shift appearing in UV-vis scanning spectrum. This favored intramolecular electron transfer from Fe2+-NTA to PFOS under UV254 irradiation to form electron-accepting PFOS. Molecular electrostatic potential and atom charge distribution analyses suggested electron density rearrangement and perturbation in the perfluorinated carbon chain of electron-accepting PFOS, leading to the decrease in bond dissociation energies. Intermediate products detection suggested the parallel defluorination pathways of PFOS desulfonation, middle carbon chain scission and direct C-F cleavage. NTA exhibited crucial functions in the UV/Fe2+-NTA treatment by holding Fe2+/Fe3+ in soluble form as a chelant and favoring water activation to generate hydrated electrons (eaq-) under UV irradiation as a photosensitizer. Fe2+ acting as the conduit for electron transfer and the bridge of PFOS anion and NTA was thought functioning best at 200 µM in this study. The degree of UV/Fe2+-NTA -synergized PFOS defluorination also depended on eaq- yield and UV254 photon flux. The structure dependence on the electron transfer process of PFOS and PFOA was explored incorporating molecular structure descriptors. Because of possessing greater potential to acquire electrons or less likeliness to donate its electrons than PFOA, PFOS exhibited faster defluorination kinetics in the published "reduction treatments" than "oxidation" ones. Whereas, PFOA defluorination kinetics were at similar level in both "reduction" and "oxidation" treatments.

Enhanced visible light driven photodegradation of rifampicin and Cr(VI) reduction activity of ultra-thin ZnO nanosheets/CuCo2S4QDs: A mechanistic insights, degradation pathway and toxicity assessment.

In this study, we focused on fabrication of porous ultra-thin ZnO nanosheet (PUNs)/CuCo2S4 quantum dots (CCS QDs) for visible light-driven photodegradation of rifampicin (RIF) and Cr(VI) reduction. The morphology, structural, optical and textural properties of fabricated photocatalyst were critically analyzed with different analytical and spectroscopic techniques. An exceptionally high RIF degradation (99.97%) and maximum hexavalent Cr(VI) reduction (96.17%) under visible light was achieved at 10 wt% CCS QDs loaded ZnO, which is 213% and 517% greater than bare ZnO PUNs. This enhancement attributed to the improved visible light absorption, interfacial synergistic effect, and high surface-rich active sites. Extremely high generation of ●OH attributed to the spin-orbit coupling in ZnO PUNs@CCS QDs and the existence of oxygen vacancies. Besides, the ZnOPUNs@CCS QDs, forming Z-scheme heterojunctions, enhanced the separation of photogenerated charge carriers. We investigated the influencing factors such as pH, inorganic ions, catalyst dosage and drug dosage on the degradation process. More impressively, a stable performance of ZnO PUNs@CCS QDs obtained even after six consecutive degradation (85.9%) and Cr(VI) reduction (67.7%) cycles. Furthermore, the toxicity of intermediates produced during the photodegradation process were assessed using ECOSAR program. This work provides a new strategy for ZnO-based photocatalysis as a promising candidate for the treatment of various contaminants present in water bodies.

Spectroscopic studies of the role of dissolved organic matter in acenaphthene photodegradation in liquid water and ice.

The effect of concentration and origin of dissolved organic matter (DOM) on acenaphthene (Ace) photodegradation in liquid water and ice was investigated, and the components in DOM which were involved in Ace photodegradation were identified. The DOM samples included Suwannee River fulvic acid (SRFA), Elliott soil humic acid (ESHA), and an effluent organic matter (EfOM) sample. Due to the production of hydroxyl radical (•OH) and triplet excited-state DOM (3DOM*) which react with Ace, DOM had promotion effects on Ace photodegradation. However, the promotion effects of DOM were prevailed over by their suppressing effect of DOM including screening light effect, intermediates reducing effect and RS quenching effect, and thus, the photodegradation rates of Ace decreased in the presence of the three DOM with concentrations of 0.5-7.5 mg C/L in liquid water and ice. ESHA had higher light absorption and thus had higher screening light effect on Ace photodegradation in liquid water than SRFA and EfOM. At each DOM concentration, ESHA exhibited higher promotion effect on Ace photodegradation than SRFA and EfOM, in liquid water and ice. The binding of Ace with DOM was indicated by decreases in fluorescence intensity of Ace when coexisted with DOM. However, the binding of Ace to DOM played an unimportant role in suppressing Ace photodegradation. The photodegradation behavior of fluorophores in Ace with DOM present in ice was not similar to that in liquid water. C-O, C═O, carboxyl groups O-H and aliphatic C-H functional groups in DOM were involved in the interaction of DOM with Ace. The presence of Ace seemed to have no influence on the photodegradation behavior of functional groups in DOM.

Transition-state defect structure: A new strategy for TiO2-based porous materials to enhance photodegradation of pollutants.

The aim of this paper is to investigate the derived structure and properties of Zeolitic Imidazolate Framework-8 (ZIF-8), and the effect of residual structural on the catalytic properties after loading with Titanium Dioxide (TiO2). For this purpose, we ingeniously prepare C-ZIF-8@TiO2 with a transition-state defect structure and apply it for efficiently degrading organic dye wastewater represented by Rhodamine B (Rh-B). Thanks to the transition-state defect structure loaded with TiO2 and ZIF-8 self-derived Carbon (C) and Zinc Oxide (ZnO), the catalytic performance of C-ZIF-8@TiO2 is superior to that of TiO2 and normal TiO2/ZIF-8 composites, and it is effective in degrading a variety of antibiotics and dyes. The related characterization also shows good photovoltaic properties and long-term durability for C-ZIF-8@TiO2. The mechanism on free radical action is elucidated and the possible degradation pathway for Rh-B is speculated. Therefore, C-ZIF-8@TiO2 provides a new strategy for the degradation of organic pollutants in water bodies.

Effects of dissolved organic matter and halogen ions on phototransformation of pharmaceuticals and personal care products in aquatic environments.

Photochemical reactions contribute to the attenuation and transformation of pharmaceuticals and personal care products (PPCPs) in surface natural waters. Nevertheless, effects of DOM and halogen ions on phototransformation of PPCPs remain elusive. This work selected disparate PPCPs as target pollutants to investigate their aquatic phototransformation processes. Results show that PPCPs containing multiple electron-donating groups (-OH, -NH2, -OR, etc.) are more reactive with photochemically produced reactive intermediates (PPRIs) such as triplet DOM (3DOM*), singlet oxygen (1O2), and reactive halogen species (RHSs), relative to PPCPs containing electron-withdrawing groups (-NOR, -COOR, -OCR, etc.). The generation of RHSs as a result of the coexistance of DOM and halide ions changed the contribution of PPRIs to the photochemical conversion of PPCPs during their migration from fresh water to seawater. For PPCPs (AMP, SMZ, PN, NOR, CIP, etc) with highly reactive groups toward RHSs, the generation of RHSs facilitated their photolysis in halide ion-rich waters, where Cl- plays a critical role in the photochemical transformation of PPCPs. Density functional theory (DFT) calculations showed that single electron transfer and H-abstraction are main reaction pathways of RHSs with the PPCPs. These results demonstate the irreplaceable roles of PPRIs and revealing the underlying reaction mechanisms during the phototransformation of PPCPs, which contributes to a better understanding of the environmental behaviors of PPCPs in complex aquatic environments.

Electron-Induced Damage by UV Photolysis of DNA Attached to Gold Nanoparticles.

Photolysis of DNA attached to gold nanoparticles (AuNPs) with ultraviolet (UV) photons induces DNA damage. The release of nucleobases (Cyt, Gua, Ade, and Thy) from DNA was the major reaction (99%) with an approximately equal release of pyrimidines and purines. This reaction contributes to the formation of abasic sites in DNA. In addition, liquid chromatography-mass spectrometry/MS (LC-MS/MS) analysis revealed the formation of reduction products of pyrimidines (5,6-dihydrothymidine and 5,6-dihydro-2'-deoxyuridine) and eight 2',3'- and 2',5'-dideoxynucleosides. In contrast, there was no evidence of the formation of 5-hydroxymethyluracil and 8-oxo-7,8-dihydroguanine, which are common oxidation products of thymine and guanine, respectively. Using appropriate filters, the main photochemical reactions were found to involve photoelectrons ejected from AuNPs by UV photons. The contribution of "hot" conduction band electrons with energies below the photoemission threshold was minor. The mechanism for the release of free nucleobases by photoelectrons is proposed to take place by the initial formation of transient molecular anions of the nucleobases, followed by dissociative electron attachment at the C1'-N glycosidic bond connecting the nucleobase to the sugar-phosphate backbone. This mechanism is consistent with the reactivity of secondary electrons ejected by X-ray irradiation of AuNPs attached to DNA, as well as the reactions of various nucleic acid derivatives irradiated with monoenergetic very-low-energy electrons (∼2 eV). These studies should help us to understand the chemistry of nanoparticles that are exposed to UV light and that are used as scaffolds and catalysts in molecular biology, curative agents in photodynamic therapy, and components of sunscreens and cosmetics.

Enhanced photodegradation of oxytetracycline antibiotic in wastewater by implementing ZnO-loaded carbon fiber.

The antibiotic oxytetracycline (OCA) exhibits high insolubility in the natural environment, posing a significant challenge for its removal. This study synthesized a porous structure and a high-surface-area carbon fiber, incorporating zinc oxide (ZnO/CFB) for the effective removal of OCA in wastewater. The material characterization revealed exceptional optical and photochemical properties of ZnO/CFB, featuring a reduced band gap energy of 2.7 eV. ZnO/CFB exhibited robust performance in the photodegradation of OCA in wastewater, achieving an impressive removal efficiency of 86.7%. Remarkably, the reduction of total organic carbon (TOC) reached an outstanding 97.5%. LC-MS analysis confirmed the complete oxidation of OCA and its intermediates, transforming them into inorganic substances within 60 min. This study introduces an efficient strategy for eliminating antibiotic pollutants from wastewater, highlighting the potential of ZnO/CFB as an effective and stable photocatalyst for environmental remediation.

Photochemical behaviors of sludge extracellular polymeric substances from bio-treated effluents towards antibiotic degradation: Distinguish the main photosensitive active component and its environmental implication.

Activated sludge extracellular polymeric substances (ASEPSs) comprise most dissolved organic matters (DOMs) in the tail water. However, the understanding of the link between the photolysis of antibiotic and the photo-reactivity/photo-persistence of ASEPS components is limited. This study first investigated the photochemical behaviors of ASEPS's components (humic acids (HA), hydrophobic substances (HOS) and hydrophilic substances (HIS)) separated from municipal sludge's EPS (M-EPS) and nitrification sludge's EPS (N-EPS) in the photolysis of sulfadiazine (SDZ). The results showed that 60% of SDZ was removed by the M-EPS, but the effect in the separated components was weakened, and only 24% - 39% was degraded. However, 58% of SDZ was cleaned by HOS in N-EPS, which was 23% higher than full N-EPS. M-EPS components had lower steady-state concentrations of triplet intermediates (3EPS*), hydroxyl radicals (·OH) and singlet oxygen (1O2) than M-EPS, but N-EPS components had the highest concentrations (5.96 ×10-15, 8.44 ×10-18, 4.56 ×10-13 M, respectively). The changes of CO, C-O and O-CO groups in HA and HOS potentially correspond to reactive specie's generation. These groups change little in HIS, which may make it have radiation resistance. HCO-3 and NO-3 decreased the indirect photolysis of SDZ, and its by-product N-(2-Pyrimidinyl)1,4-benzenediamine presents high environmental risk.