Electron Paramagnetic Resonance Analysis Research Articles

Efficient acetaminophen degradation via peroxymonosulfate activation by Mn/N co-doped biochar: Performance, mechanism and approach

Advanced oxidation processes (AOPs) are frequently used to remove stubborn pollutants from the aquatic environment, and developing an eco-friendly and high-performance catalyst is an effective strategy to enhance the efficiency of AOPs. In this study, Mn nanoparticle-loaded nitrogen-doped kelp biochar catalysts were synthesized at varying temperatures to activate peroxymonosulfate (PMS) and degrade acetaminophen (ACT). The findings show that the Mn@NBC-800/PMS system can fully remove ACT (20 mg/L) in 10 min under ideal circumstances. Electrochemical tests, electron paramagnetic resonance (EPR) analysis and quenching experiments reveal that the primary mechanism of ACT degradation was a non-radical pathway dominated by electron transfer and singlet oxygen (1O2). In addition, mechanism studies indicate that Mn species, C═O groups and graphite N were possible active sites. The Mn@NBC-800/PMS system demonstrates excellent catalytic activity across various pH values, inorganic anions, and water conditions, making it highly suitable for practical applications. This study emphasizes the significant potential of Mn/N co-doped biochar and provides invaluable insights for designing efficient carbon-based catalysts for wastewater treatment.

The synergistic effect of periodate/ferrate (VI) system on disinfection of antibiotic resistant bacteria and removal of antibiotic resistant genes: The dominance of Fe (IV)/Fe (V)

The proliferation of antibiotic resistant genes (ARGs) and antibiotic resistant bacteria (ARB) caused by antibiotic abuse has raised concerns about the global infectious-disease crisis. This study employed periodate (PI)/ferrate (VI) (Fe (VI)) system to disinfect Gram-negative ARB (Escherichia coli DH5α) and Gram-positive bacteria (Bacillus subtilis ATCC6633). The PI/Fe (VI) system could inactivate 1 × 108 CFU/mL of Gram-negative ARB and Gram-positive bacteria by 4.0 and 2.8 log in 30 min. Neutral and acidic pH, increase of PI dosage and Fe (VI) dosage had positive impacts on the inactivation efficiency of ARB, while alkaline solution and the coexistence of 10 mM Cl-, NO3-, SO42- and 20 mg/L humic acid had slightly negative impacts. The reactive species generated by PI/Fe (VI) system could disrupt the integrity of cell membrane and wall, leading to oxidative stress and lipid peroxidation. Intracellular hereditary substance, including DNA and ARGs (tetA), would leak into the external environment through damaged cells and be degraded. The electron spin resonance analysis and quenching experiments indicated that Fe (IV)/Fe (V) played a leading role in disinfection. Meanwhile, PI/Fe (VI) system also had an efficient removal effect on sulfadiazine, which was expected to inhibit the ARGs transmission from the source.

IZCp and PZCp: Redox Non-innocent Cyclopentadienyl Ligands as Electron Reservoirs for Sandwich Complexes.

A long-sustained effort of systematic steric and electronic modification of cyclopentadienyl (Cp) ligands has enabled them to find wide-ranging, valuable applications. Herein, we present two novel Cp ligands: imidazolium- and pyrrolinium-substituted zwitterionic Cps (IZCp and PZCp), whose key utility is redox non-innocence─the ability to participate cooperatively with the metal center in redox reactions. Through the simple metalation of ZCps, the Cr(0) and Mo(0) half-sandwich complexes (IZCp)Cr(CO)3, (PZCp)Cr(CO)3, (IZCp)Mo(CO)3, and (PZCp)Mo(CO)3, respectively, as well as the Ru(II) sandwich complexes [(IZCp)RuCp]PF6 and [(PZCp)RuCp]PF6 were prepared. The sandwich complexes were fully characterized and showed by cyclic voltammetry reversible one-electron reduction at E1/2 potentials ranging from -1.7 to -2.7 V vs Fc/Fc+. These values are unusually low and have not been observed with other Cp ligands due to the instability of the reduced complexes. Density functional theory (DFT) calculations for the reduced sandwich derivatives with IZCp and PZCp showed their spin densities to be highly delocalized over their ZCp ligand moieties (70-90%). Electron paramagnetic resonance (EPR) analysis of the isolated K[(PZCp)Mo(CO)3] and (PZCp)RuCp also indicated a high degree of ligand-localized radical character. Thus, the IZCp and PZCp ligands act as electron reservoirs to sustain these sandwich complexes in highly reduced states. At the same time, the CO stretching frequencies of K[(PZCp)Mo(CO)3]: νCO 1871, 1748, and 1699 cm-1, rank the [PZCp]- ligand as the strongest electron-donating Cp ligand among the reported CpMo(CO)3 derivatives, whose νCO > 1746 cm-1. In addition, these redox non-innocent Cps were obtained in high yields and found to be practically air- and moisture-stable, unlike typical Cps.

Highly dispersed Pd icosahedra and Ag nanocubes on ultrathin g-C3N4 nanosheet for boosting photocatalytic bacterial inactivation and organic pollutants degradation

Engineering surface facet of metallic nanoparticles that decorated on certain substants is an intriguing strategy to modulate photocatalytic capacity. Herein, a novel photocatalyst by doping g-C3N4 nanosheet with Pd icosahedra with {111} facets and Ag nanocubes with {100} facets were firstly synthesized through facile wet-chemical route. The successfully constructed g-C3N4/Pd/Ag composites were employed as a visible-light-driven dual-functional photocatalyst for bacterial inactivation and organic contaminant degradation. Result suggested that 1 × 108 CFU/mL E. coli strains can be totally inactivated by g-C3N4/Pd/Ag within 60 min, outperformed that of {100} faceted enclosed Pd nanocubes functioned g-C3N4/Ag. Also, the optimized g-C3N4/Pd/Ag exhibited ideal photocatalytic performance toward tetracycline and methylene blue degradation. The rate constant was found to be 8.74 × 10−3 and 7.08 × 10−3 min−1, respectively, which was higher than those of bare g-C3N4 and g-C3N4/Pd. Quenching experiment and electron paramagnetic resonance analysis suggested that hole (h+), electron (e−), and superoxide radical (O2−) exerted a key role in the improved capacity. Furthermore, the more positive Fermi level of Pd icosahedra and Ag nanocubes relative to that of g-C3N4 also contributed to the enhanced photocatalytic performance. Collectively, our work can provide in-depth insight into fabricate novel facet-engineering photocatalyst for environmental applications.

Novel cow dung-doped sludge biochar as an efficient ozone catalyst: Synergy between graphitic structure and defects induces free radical pathways

A composite material, cow dung-doped sludge biochar (Zn@SBC-CD), was synthesized by one-step pyrolysis using ZnCl2 as an activating agent and applied to a catalytic ozonation process (COP) for methylene blue (MB) removal. SEM, XRD, FTIR, XPS and BET analyses were performed to characterize the biochar (BC) catalysts. Zn@SBC-CD had high graphitization degree, abundant active sites and uniform distribution of Zn on its surface. Complete removal of MB was achieved within 10 min, with a removal rate much higher than that of ozone alone (32.4%), implying the excellent ozone activation performance of Zn@SBC-CD. The influence of experimental parameters on MB removal efficiency was examined. Under the optimum conditions in terms of ozone dose 0.04 mg/mL, catalyst dose 400 mg/L and pH 6.0, COD was completely removed after 20 min. Electron paramagnetic resonance (EPR) analysis revealed radical and non-radical pathways were involved in MB degradation. The Zn@SBC-CD/O3 system generated superoxide anion radicals (•O2−), which were the main active species for MB removal, through adsorption, transformation, and transfer, Furthermore, Zn@SBC-CD exhibited good reusability and stability in cycling experiments. This study provides a novel approach for the utilization of cow dung and sludge in synthesis of functional biocatalysts and application in organic wastewater treatment.

Comparative study of reactive oxygen species and tetracycline degradation pathways in catalytic peroxodisulfate activation by asymmetric mesoporous TiO2 and the corresponding controlled-release materials

The removal of trace amounts of antibiotics from water environments while simultaneously avoiding potential environmental hazards during the treatment is still a challenge. In this work, green, harmless, and novel asymmetric mesoporous TiO2 (A-mTiO2) was combined with peroxodisulfate (PDS) as active components in a controlled-release material (CRM) system for the degradation of tetracycline (TC) in the dark. The formation of reactive oxygen species (ROS) and the degradation pathways of TC during catalytic PDS activation by A-mTiO2 powder catalysts and the CRMs were thoroughly studied. Due to its asymmetric mesoporous structure, there were abundant Ti3+/Ti4+ couples and oxygen vacancies in A-mTiO2, resulting in excellent activity in the activation of PDS for TC degradation, with a mineralization rate of 78.6%. In CRMs, ROS could first form during PDS activation by A-mTiO2 and subsequently dissolve from the CRMs to degrade TC in groundwater. Due to the excellent performance and good stability of A-mTiO2, the resulting constructed CRMs could effectively degrade TC in simulated groundwater over a long period (more than 20 days). From electron paramagnetic resonance analysis and TC degradation experiments, it was interesting to find that the ROS formed during PDS activation by A-mTiO2 powder catalysts and CRMs were different, but the degradation pathways for TC were indeed similar in the two systems. In PDS activation by A-mTiO2, besides the free hydroxyl radical (·OH), singlet oxygen (1O2) worked as a major ROS participating in TC degradation. For CRMs, the immobilization of A-mTiO2 inside CRMs made it difficult to capture superoxide radicals (·O2−), and continuously generate 1O2. In addition, the formation of sulfate radicals (·SO4−), and ·OH during the release process of CRMs was consistent with PDS activation by the A-mTiO2 powder catalyst. The eco-friendly CRMs had a promising potential for practical application in the remediation of organic pollutants from groundwater.

Synthesis of Fe-doped sludge biochar from Fenton sludge for efficient activation of peroxymonosulfate in tetracycline hydrochloride degradation

Traditional sludge treatment methods have problems in terms of environmental safety and cost-effectiveness. In this study, we followed the principle of "waste for waste" to synthesize magnetic sludge biochar (FSBC800) from biochemical sludge and Fenton sludge to activate persulfate (PMS) to remove persistent pollutants. Tetracycline hydrochloride (TC-HCl) was degraded up to 90.9% by FSBC800 using an active PMS system in just 30 minutes. This removal rate is higher than that of Fenton sludge biochar and biochemical sludge biochar by 2.7 and 1.8 times, respectively. The self-contained Fe in Fenton sludge formed evenly distributed Fe3O4 particles, while the biochemical sludge provided a large number of oxygen-containing functional groups, which increased the reactive active sites of FSBC800 and improved the catalytic performance. The dominant role of SO₄•⁻, •OH, and ¹O₂ in the degradation of TC-HCl was demonstrated by the identification of reactive oxygen species and electron paramagnetic resonance (EPR) analysis. By examining the intermediates, a potential TC-HCl degradation pathway was postulated. The catalyst has good reusability and practical application, and the removal of TC-HCl was still 84.8% after four replicated experiments. This study establishes a cost-effective, efficient, and recyclable biochar-based catalyst for water remediation, and at the same realizes resourceful utilization of sludge.

Co2+-adsorbed chitosan-grafted-poly(acrylic acid) hydrogel as peroxymonosulfate activator for effective dye degradation

In this work, chitosan-grafted-poly(acrylic acid) (CS-g-PAA) was synthesized for use as a Co2+ adsorbent and circularly utilized as a peroxymonosulfate (PMS) activator in the degradation of rhodamine B (RhB) dye. CS-g-PAA demonstrated 3.7 times higher adsorption capacity toward Co2+ than pristine chitosan. The impact of the adsorption conditions was evaluated. The pseudo-second-order kinetic model and the Langmuir isotherm model best described the adsorption process. Under optimum conditions, the adsorption capacity of CS-g-PAA for Co2+ was 212 mg/g. The Co2+-adsorbed CS-g-PAA hydrogel was further utilized in the RhB degradation process. The effects of catalyst dosage, initial RhB concentration, pH, and the coexistence of anions on the degradation of RhB were studied. The hydrogel catalyst could remove 98 % of RhB within 5 min, at a degradation rate of 0.624 per min. Electron paramagnetic resonance (EPR) analysis and the radical scavenger experiment suggested that SO4•−, HO•, 1O2, and O2•− were involved in the degradation. Furthermore, when tested in various water systems, high degradation efficiencies of 98 % were attained after 20 min. The hydrogel catalyst performed excellent degradation over ten cycles without any chemical recovery processes. Moreover, high degradation efficiencies were observed between 95 % and 98 % when tested with other dyes.

Al/Ca-doped CuFe2O4 prepared from waste printed circuit boards as a magnetic peroxymonosulfate activator for the degradation of organic pollutants

Cu-containing heterogeneous catalysts are being increasingly used to activate peroxymonosulfate (PMS) and remove organic pollutants from wastewater. However, expensive raw materials and limited metal resources restrict the practical applications of these catalysts. In this study, waste printed circuit boards (PCBs), a typical Cu-rich electronic waste, were used to prepare Al/Ca-doped CuFe2O4 (PCBs-CuFe2O4) with the assistance of Fe3+. The obtained PCBs-CuFe2O4, doped with the catalytically inert metals Al and Ca, possessed abundant porous structures, high specific surface areas, rich surface oxygen vacancies, and excellent magnetic properties. Despite its relatively poor purity and crystallinity compared to those of CuFe2O4 prepared using commercial chemicals, PCBs-CuFe2O4 exhibited superior performance in reactive blue 19 (RB19) degradation by activating PMS. Additionally, the PCBs-CuFe2O4/PMS system exhibited strong resistance to pH and water matrices, confirming the practical application of PCBs-CuFe2O4 for the elimination of organic pollutants in wastewater. Furthermore, the results of electrochemical measurements, quenching experiments, and electron paramagnetic resonance analysis revealed that 1O2 plays an important role in the degradation of RB19. The Cu(I)/Cu(II), Fe(II)/Fe(III), and OV of PCBs-CuFe2O4 dominate the activation of PMS. Thus, this study presents a novel strategy for reutilizing waste PCBs and eliminating organic contaminants in wastewater.

MoS2/SrTiO3 composite for piezocatalysis and piezocatalytic activation of peroxymonosulfate for efficient degradation of sulfamethoxazole

The piezocatalysis, in which piezoelectric polarization charges on the surface of piezocatalyst can initiate the generation of highly active species, has emerged as one of the effective strategies for organic pollutant removal in water and wastewater treatment. In this work, the composite piezoelectric material MoS2/SrTiO3 (MS/STO) was prepared and characterized. The synergistically piezoelectric effect between SrTiO3 and MoS2 was proven by electrochemical tests. Using ultrasound (US) as inputting mechanical energy, MS/STO exhibited effective degradation (∼ 70.2 % in 20 min) towards target antibiotic (sulfamethoxazole, SMX) in water. Further improving effect of peroxymonosulfate (PMS) on US/(MS/STO) for the degradation of SMX was also investigated. The results revealed that SMX was completely degraded within 20 min. Influencing factors including operation parameters and water composition for SMX degradation in US/(MS/STO)/PMS were studied, which demonstrated the good environmental adaptability of the system. The active species generated in the reaction system were identified via quenching experiments and electron paramagnetic resonance analysis, revealing the presence of O2•−, 1O2, •OH, and SO4•−. The possible reaction mechanism in US/(MS/STO)/PMS and the degrading pathway of SMX were proposed.

Electron spin resonance analysis of photoenzymatic catalysis

This Perspective highlights recent research progress and prospects in elucidating the catalytic mechanism of photoenzymes using ESR (electron spin resonance) spectroscopy, which is emerging as a unique and crucial method for identifying radical intermediates, illustrating electron transfer events and the underlying mechanisms of photoenzymatic catalysis.

Cation-mediated acid-base pairs for mild oxidative cleavage of lignocellulosic β-1,4-glycosidic bonds

Solar-driven lignocellulosic biomass photoreforming holds significant promise for the production of value-added chemicals and fuels. The cleavage of the β-1,4-glycosidic bond is crucial for the effective conversion of lignocellulosic biomass. Polymeric carbon nitride (PCN) with acid-base pairs (M-C sites) is developed through heteroatomic carbon incorporation and cation insertion. It can be used for the gentle oxidation of cellobiose to monosaccharides, bypassing the formation of organic acids such as gluconic acid and glucaric acid. A series of different alkaline/alkaline-earth cation for regulation of acid-base pairs exhibited a negative correlation between β-1,4-glycosidic bond cleavage and cation radii. In particular, the introduction of short-radius cations (such as Li) into PCN enabled the formation of acid-base (M-C) pairs characterized by strong acidity. It also enhanced electron delocalization around M-C sites, potentially promoting the generation of reactive radicals in the reaction. Electron paramagnetic resonance analysis confirmed the presence of •OH radicals. The mild oxidative species, are the primary reactive radicals responsible for β-1,4-glycosidic bond cleavage in cellobiose. This study provides insightful evidence for the rational regulation of acid-base sites in facilitating β-1,4-glycosidic bond cleavage. It sheds light on the oxidative cleavage mechanisms integral to lignocellulosic biomass photoreforming, offering insights for advancing sustainable biomass conversion technologies.

Inhibition of 7-dehydrocholesterol reductase prevents hepatic ferroptosis under an active state of sterol synthesis

Recent evidence indicates ferroptosis is implicated in the pathophysiology of various liver diseases; however, the organ-specific regulation mechanism is poorly understood. Here, we demonstrate 7-dehydrocholesterol reductase (DHCR7), the terminal enzyme of cholesterol biosynthesis, as a regulator of ferroptosis in hepatocytes. Genetic and pharmacological inhibition (with AY9944) of DHCR7 suppress ferroptosis in human hepatocellular carcinoma Huh-7 cells. DHCR7 inhibition increases its substrate, 7-dehydrocholesterol (7-DHC). Furthermore, exogenous 7-DHC supplementation using hydroxypropyl β-cyclodextrin suppresses ferroptosis. A 7-DHC-derived oxysterol metabolite, 3β,5α-dihydroxycholest-7-en-6-one (DHCEO), is increased by the ferroptosis-inducer RSL-3 in DHCR7-deficient cells, suggesting that the ferroptosis-suppressive effect of DHCR7 inhibition is associated with the oxidation of 7-DHC. Electron spin resonance analysis reveals that 7-DHC functions as a radical trapping agent, thus protecting cells from ferroptosis. We further show that AY9944 inhibits hepatic ischemia-reperfusion injury, and genetic ablation of Dhcr7 prevents acetaminophen-induced acute liver failure in mice. These findings provide new insights into the regulatory mechanism of liver ferroptosis and suggest a potential therapeutic option for ferroptosis-related liver diseases.

Photocatalytic degradation of tetracycline using a novel WO3–ZnO/AC under visible light irradiation: Optimization of effective factors by RSM-CCD

Mitigating pharmaceutical pollution in the global environment is imperative, and tetracycline (TC) is a commonly utilized antibiotic in human and veterinary medicine. The persistent existence of TC highlights the necessity of establishing efficient measures to protect water systems and the environment from detrimental contaminants. Herein, a novel rhubarb seed waste-derived activated carbon-supported photocatalyst (WO3–ZnO/RUAC) was synthesized by combining wet impregnation and ultrasonic methods. The activated carbon (AC) was obtained from rhubarb seed waste for the first time via chemical activation. The function of AC as an electron acceptor and in separating electron-hole pairs was illuminated by characterization analyses that included XRD, FTIR, XPS, SEM, TEM, PL, EIS, TPC, and UV-DRS. Using the response surface methodology-central composite design (RSM-CCD) technique, the synthesis parameters of the composite were systematically optimized. Under ideal conditions, with a TC concentration of 33 mg. L−1, pH of 4.57, irradiation time of 108 min, and catalyst dose of 0.85 g. L−1, the highest degradation efficiency of TC by this composite, achieved 96.5%, and it was reusable for five cycles. Subsequently, trapping tests and electron spin resonance (ESR) analysis were conducted, elucidating that •OH and •O2− radicals played pivotal roles in the photocatalytic degradation of TC. This research offers valuable insights into utilizing the AC-based photocatalyst to degrade pharmaceutical micropollutants effectively.

Synthesis, molecular modeling, DFT studies, and EPR analysis of 1,4-dihydropyridines as potential calcium channel blockers

1,4-Dihydropyridines (DHPs) are widely recognized as a highly effective class of L-type calcium channel blockers that offer significant therapeutic potential in managing cardiovascular conditions. Furthermore, their ability to target other types of calcium channels makes DHPs attractive candidates for therapeutic applications in neurological and psychiatric disorders. Close examination of the chemical structures of approved DHP-based antihypertensive drugs with a history of over forty years in the market reveals that the C-4 position is the least altered part of this privileged ring system. In the present study, we focused on this position and synthesized two novel compounds (DB1 and DB2) by carrying out chemical modifications on suitable positions of the main scaffold of DA1 (isobutyl 4-(benzo[d][1,3]dioxol-5-yl)-2,6,6-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate) that was previously identified as a DHP-based effective and selective inhibitor of T-type (Cav3.2) over L-type (Cav1.2) calcium channel. Based on whole-cell patch-clamp analysis on Cav1.2 and Cav3.2, DB1 with bromine group on the benzodioxole ring appeared to be a more effective and selective inhibitor of Cav3.2 compared to DB2 with nitro at the same locus. Molecular docking and molecular dynamics (MD) simulations were performed to investigate the binding mode of both DB1 isomers to Cav3.2. Furthermore, density functional theory (DFT) methods were employed to obtain information regarding the stability of the molecules by computing various parameters, such as electric dipole moment, band gap, electronegativity, and global chemical hardness-softness, related to their charge-transfer characteristics. According to DFT studies, DB1 also appeared to be chemically more stable than DB2. Finally, ionizing radiation-induced free radicals of gamma-irradiated DB1 and DB2 in powder form were examined utilizing the electron paramagnetic resonance (EPR) technique and the obtained data demonstrated that radiation sterilization is suitable for the dosage forms including DB1 and DB2.

Flash combustion synthesis using two different fuels and characterization of LiF-doped TiO2 for the photocatalytic applications

The flash combustion method was used to prepare LiF-doped TiO2 photocatalysts materials using glycine or urea as a fuel with different weight percentage of LiF. The synthesized powders have been characterized by thermogravimetric analysis (TG), scanning electron microscope (SEM) with energy dispersive spectrometer (EDX) analyzer, the specific surface area measurement was performed by BET. The crystallization and the phase transformation anatase-rutile for the powders have been verified by XRD. SEM micrographs for these powders shows the presence of nanoparticles. To investigate the optical band gap of the synthesized samples, UV–Vis spectroscopy was conducted using the diffuse reflectance mode (DRS). The O2−/F− substitution and the presence of Ti3+ centers was confirmed by electron paramagnetic resonance (EPR) analysis. The photocatalytic activity of the TiO2-xLiF powders were evaluated through the photocatalytic degradation of Methylene blue (MB) in water under UV–visible light exposure. The results indicated that during the flash combustion synthesis, the nature of the fuel and the percentage of the doping element led to the presence of different polymorphs of TiO2 which influences the photocatalytic efficiency attributed to the synergistic effect between the two phases (anatase and rutile). The LiF-doped TiO2 powders synthesized by flash combustion in both cases (by using glycine or urea) showed high performance in MB degradation compared to commercial TiO2 and undoped synthesized TiO2 powders, with an optimal degradation of 99 % achieved with 2 wt % LiF-doped TiO2 using glycine as a fuel and after 6 h of UV–Vis irradiation.

Comparative EPR Studies on the Influence of Genistein on Free Radicals in Non-Irradiated and UV-Irradiated MCF7, T47D and MDA-MB-231 Breast Cancer Cells.

The antioxidant activity and the association of genistein with carcinogenesis are widely documented. Few studies directly measure the number of free radicals generated in cells, either during the action of factors stimulating their formation, e.g., ultraviolet (UV), or after exposure to antioxidants. The most suitable method for analysing free radicals is electron paramagnetic resonance (EPR) spectroscopy. The EPR method detects a paramagnetic centre with a single electron. Antioxidants neutralize free radicals, therefore, EPR analysis of antioxidant efficacy is as valuable and important as studying the paramagnetic centres of radicals. The aim of the study was to determine the influence of genistein on free radicals basal level and after UV exposure in breast cancer cell lines MCF7, T47D and MDA-MB-231 cell lines. The impact of genistein on cell viability was investigated at concentrations of 0.37 μM, 3.7 μM, 37 μM and 370 μM. Genistein at a concentration of 370 μM revealed a cytotoxic effect on the cells of all three tested breast cancer lines. Genistein at a concentration of 0.37 μM showed no significant effect on the cell viability of all tested breast cancer lines. Therefore, cell proliferation and antioxidant properties were examined using genistein at a concentration of 0.37 μM and 37 μM. X-band (9.3 GHz) EPR spectra of three different types of breast cancer cells (ER-positive, PR-positive and HER-2 negative: MCF7 and T47D and triple-negative MDA-MB-231) were compared. UV irradiation was used as a factor to generate free radicals in cells. The effect of free radical interactions with the antioxidant genistein was tested for non-UV-irradiated (corresponding to the basal level of free radicals in cells) and UV-irradiated cells. The levels of free radicals in the non-irradiated cells studied increased in the following order in breast cancer cells: T47D < MDA-MB-231 < MCF7 and UV-irradiated breast cancer cells: MDA-MB-231 < MCF7 < T47D. UV-irradiation altered free radical levels in all control and genistein-cultured cells tested. UV irradiation caused a slight decrease in the amount of free radicals in MCF7 cells. A strong decrease in the amount of free radicals was observed in UV-irradiated MDA-MB-231 breast cancer cells. The amount of free radicals in T47D cancer cells increased after UV irradiation. Genistein decreased the amount of free radicals in non-irradiated and UV-irradiated MCF7 cells, and only a weak effect of genistein concentrations was reported. Genistein greatly decreased the amount of free radicals in UV-irradiated T47D cancer cells cultured with genistein at a concentration of 3.7 μM. The effect of genistein was negligible in the other samples. Genistein at a concentration of 3.7 μM decreased the amount of free radicals in non-irradiated MDA-MB-231 cancer cells, but genistein at a concentration of 37 μM did not change the amount of free radicals in these cells. An increase in the amount of free radicals in UV-irradiated MDA-MB-231 cancer cells was observed with increasing genistein concentration. The antioxidant efficacy of genistein as a potential plant-derived agent supporting the treatment of various cancers may be determined by differences in signalling pathways that are characteristic of breast cancer cell line subtypes and differences in activation of oxidative stress response pathways.

Hollow AMn2O4-δ (A = Co, Zn, Ni) nanotube for direct photo-oxidation of methane to C1 and C2 alcohols at atmospheric pressure and room temperature

Methane (CH4) conversion is brought into research hotspot in the field of environment, and direct photo-oxidation of methane into C1 and C2 alcohols under moderate conditions remains a huge challenge. Herein, we report a series of hollow AMn2O4-δ (A = Co, Zn, Ni) spinel nanotubes (HNTs) for the direct photo-oxidation of methane (DPOM) reaction. The results of catalytic performance demonstrated that the CH4 conversion and the yields of high value-added liquid products arrange in order of ZnMn2O4-δ HNTs > CoMn2O4-δ HNTs > NiMn2O4-δ HNTs. The ZnMn2O4-δ HNTs exhibited a superior CH4 conversion of 53.9 %, a liquid product yield of 241.7 μmol g−1h−1 (CH3OH 40.1 μmol g−1h−1, CH3CH2OH 200.9 μmol g−1h−1) and a selectivity of 100 % under light irradiation at atmospheric pressure and room temperature conditions. Xray photoelectron spectroscopy (XPS) and low-temperature electron paramagnetic resonance (EPR) analysis showed that the substitution of Zn ion at the A-site of manganate spinel significantly improved surface chemisorbed oxygen (Oα) and oxygen vacancy activity, which were beneficial to the formation of •CH3. Multi-technology photocatalytic activity characterizations results showed that ZnMn2O4-δ HNTs possessed a narrower band gap and greatly favored the separation of photogenerated carriers. Moreover, the DPOM reaction mechanism involving the formation and dehydrogenation of alkyl and alkoxy intermediates was proposed over AMn2O4-δ (A = Zn, Co, Ni) HNTs, which was investigated through temperature-programmed desorption of CH4 (CH4-TPD), in situ EPR, in situ Fourier transform infrared spectroscopy (FT-IR) and density functional theoretical (DFT) calculations. It emphasized that CH3OH was formed via the combination of •CH3 and •OH. And it was more inclined to generate CH3CH2OH through the intermediates *CH2CH3/*CH3O. This study could broaden the avenue toward the application of manganese-based spinel in the direct photo-oxidation of methane into alcohols and offer a disparate perspective on the role of the substitution of metal ion at the A-site in enhancing the photocatalytic performance.

Two Better Than One: Enhanced Photo‐Assisted Li‐O2 Batteries with Bimetallic Fe‐UiO‐66 Metal‐Organic Framework Photocathodes

AbstractLi‐O2 batteries, known for their impressive theoretical specific energy, face significant practical challenges, including slow kinetics, voltage hysteresis, and reduced cycle life. In this study, a novel approach is introduced utilizing a bimetallic metal‐organic framework known as Fe‐UiO‐66 as a multifunctional photocatalyst to enhance the oxygen‐related reactions in photo‐assisted Li‐O2 batteries. In contrast to UiO‐66, Fe‐UiO‐66 exhibits an extended response to visible light, as confirmed through UV–vis and photoluminescence spectra. Electron paramagnetic resonance analysis provides further validation of the pivotal role played by O2− radicals in the electrochemical processes. Additionally, computations are employed to elucidate the distinct function of Fe centers and the underlying reaction mechanisms. Li‐O2 batteries with Fe‐UiO‐66 cathodes have a reduced charge/discharge voltage difference of 0.14 V under illumination and operate stably for 500 cycles. This work encourages MOF‐based photocathode development for Li‐O2 batteries.

Iron-decorated covalent organic framework as efficient catalyst for activating peroxydisulfate to degrade 2,4-dichlorophenol: Performance and mechanism insight

Herein, a novel two-dimensional double-pore covalent organic framework (JLNU-305) was synthesized using N,N,N',N'-tetrakis(4-aminophenyl)-1,4-phenylenediamine (TAPD) and 2,2′-bipyridine-5,5′-dicarboxaldehyde (BPDA). The extended π-π conjugated structure and nitrogen-riched pyridine in JLNU-305 (JLNU = Jilin Normal University) provide abundant binding sites for Fe doping. The obtained JLNU-305-Fe exhibited high and recycled catalytic efficiency for peroxydisulfate (PDS) activation to completely degrade 10 mg/L 2,4-dichlorophenol (2,4-DCP) within 8 min. The JLNU-305-Fe/PDS system showed excellent catalytic activity and cyclic stability. The capture experiments and electron paramagnetic resonance (ESR) analysis indicated that the catalytic behavior of JLNU-305-Fe/PDS is contributed to the synergistic effect between free radicals and non-free radicals. It is the first time to activate PDS for covalent organic frameworks (COFs) being used to degrade 2,4-DCP, which has a great potential for development and practical application in related water environment remediation.