Superoxide Radical Production Research Articles

Synthesis and characterization of plasmonic Au/TiO2 nanorod solids for heterogeneous photocatalysis

Plasmonic Au (1 wt%) catalysts deposited on hydrothermally synthesized TiO2 nanorods (TNR) were investigated in this study. Based on the duration of mixing of the Au precursor/TNR suspension during the wet impregnation synthesis and parameters of the end calcination, Au/TiO2 catalysts with different sizes of Au nanoparticles (Au NPs) were obtained. The prepared solids were thoroughly characterized by several instrumental techniques to investigate property-activity relationships. Regardless of the size of Au particles on the catalyst surface, an absorption peak at 550 nm occurred in all UV-Vis diffuse reflectance spectra of the investigated Au/TiO2 catalysts, which is characteristic of the localized surface plasmon resonance effect exerted by metallic Au NPs. By measuring the formation of reactive oxygen species under visible-light illumination using various scavengers, the production of superoxide anion radicals (O2•) and hydroxyl radicals were identified, however, the former were found to represent the main reactive oxygen species that govern the oxidation of aqueous bisphenol A (BPA) employed as a model organic pollutant. The activity of Au/TiO2 catalysts for the generation of O2• radicals (and BPA oxidation) increases by increasing the Schottky barrier height, which is due to the slow reduction of water-dissolved O2 on the catalyst surface.

Uncovering nanotoxicity of a water-soluble and red-fluorescent [70]fullerene nanomaterial

Engineered fullerene materials have attracted the attention of researchers in the biomedical sciences, especially when their synthetic methodology is developed to endow them with significant levels of water-solubility and bioavailability. In this study, we synthesized and characterized a water-soluble and red-fluorescent [70]fullerene nanomaterial, which fluoresced at 693 nm with a quantum yield of 0.065 and a large Stokes shift (around 300 nm). The fullerene nanomaterial generated mainly singlet oxygen after illumination with blue LED light, while superoxide anion radical production was minimal. The transmission electron microscopy as well as fluorescent studies of Drosophila melanogaster revealed that prepared [70]fullerene nanoparticles had better bioavailability than pristine [70]fullerene nanoparticles. The designed nanomaterials were observed in the apical, perinuclear, and basal regions of digestive cells, as well as the basal lamina of the digestive system's epithelium, with no damage to cell organelles and no activation of degenerative processes and cell death. Our findings provide a new perspective for understanding the in vivo behavior of fullerene nanomaterials and their future application in bioimaging and light-activated nanotherapeutics.

Вплив модуляторів факторів транскрипції NF-κB і Nrf2 на показники оксидативно–нітрозативного стресу в скелетних м’язах щурів за умов хронічної гіпомелатонінемії та вуглеводно-ліпідної дієти

This article describes the effect of NF-κB inhibitor ammonium pyrrolidine dithiocarbamate and Nrf2 inducer dimethylfumarate on indicators of oxidative-nitrosative stress in skeletal muscles of rats with chronic hypomelatoninemia, induced by roundthe-clock illumination with an intensity of 1500 lux for 30 days, against the background of a carbohydrate-lipid diet (20% fructose solution and appropriate food) for 60 days. The study demonstrated that the administration of ammonium pyrrolidine dithiocarbamate and dimethylfumarate under the experimental conditions impedes the development of hypomelatoninemia, this was accompanied by a two-fold increase in the blood serum melatonin concentration compared to the control group. Moreover, the administration of ammonium pyrrolidine dithiocarbamate and dimethylfumarate significantly reduces the production of superoxide anion radical by electron transport chains of mitochondria (by 47.9 and 51.3%) and sarcoplasmic reticulum (by 48.6 and 52.0%) in the homogenate of femoral muscles, the total activity of NO synthase (by 37.2 and 36.2%) and its inducible isoform (by 41.1 and 40.0%), the concentration of peroxynitrites of alkaline and alkaline earth metals (by 37.2 and 41.0 %), while the activity of constitutive NO-synthases (by 2.9 and 2.8 times) and their conjugation index (by 5.2 and 5.4 times) increases compared to the respective control values. We suggest that modulators of redox-sensitive transcription factors NF-κB and Nrf2 under conditions of chronic hypomelatoninemia and the exposure to the carbohydrate-lipid diet are effective means to restrain the development of oxidative-nitrosative stress in skeletal muscles.

Highly Selective Transformation of Biomass Derivatives to Valuable Chemicals by Single-Atom Photocatalyst Ni/TiO2.

Selective CC cleavage of the biomass derivative glycerol under mild conditions is recognized as a promising yet challenging synthesis route to produce value-added chemicals. Here, a highly selective catalyst for the transformation of glycerol to the high-value product glycolaldehyde is presented, which is composed of nickel single atoms confined to the surface of titanium dioxide. Driven by light, the catalyst operates under ambient conditions using air as a green oxidant. The optimized catalyst shows a selectivity of over 60% to glycolaldehyde, resulting in 1058 µmolgCat -1 h-1 production rate, and ≈3 times higher turnover number than NiOx -nanoparticle-decorated TiO2 photocatalyst. Diverse operando and in situ spectroscopies unveil the unique function of the Ni single atom, which can significantly promote oxygen adsorption, work as an electron sink, and accelerate the production of superoxide radicals, thereby improving the selectivity toward glycolaldehyde over other by-products.

Physiological Toxicity and Antioxidant Mechanism of Photoaging Microplastics on Pisum sativum L. Seedlings.

Recent studies have confirmed that changes in the physical properties of microplastics (MPs) trigger toxicological effects and ecological risks. To explore the toxicity of different types of MPs on plants, and the influence of MP photoaging, this study investigated the toxicity mechanisms of pristine, 7 and 14 d photoaged polystyrene (PS), polyamide (PA), polyethylene (PE), and polyethylene terephthalate (PET) MPs on seed germination, root growth, nutrient fraction, oxidative stress, and antioxidant systems of Pisum sativum L. (pea) seedlings. The results showed that pristine PS and 14 d photoaged PET inhibited seed germination. Compared to the pristine MPs, photoaged MPs had negative effects on root elongation. Moreover, photoaged PA and PE impeded the nutrient transport of soluble sugars from roots to stems. Notably, the production of superoxide anion radicals (•O2-) and hydroxyl radicals (•OH) through the photoaging of MPs exacerbated oxidative stress and reactive oxygen species formation in roots. Antioxidant enzyme data revealed that the activities of superoxide dismutase and catalase were significantly activated in photoaged PS and PE, respectively, in order to scavenge •O2- and hydrogen peroxide (H2O2) accumulation and alleviate lipid peroxidation levels in cells. These findings provide a new research perspective on the phytotoxicity and ecological risk of photoaged MPs.

Synthesize, construction and enhanced performance of Bi2WO6/ZnS heterojunction under visible light: Experimental and DFT study

With the simple perovskite structure, Bi2WO6 could be utilized as a modifier to overcome the low visible light response of the wide energy band photocatalyst ZnS. Flower-like Bi2WO6 was simply synthesized by hydrothermal method and Bi2WO6/ZnS heterojunction was constructed via solvothermal reaction. The results showed that ZnS nanospheres were uniformly loaded on the flower-like structure, which was well kept under low concentration loading (≤20%ωt ZnS). The degradation of MB and Rh.B under visible light was used to measure the photocatalytic activity of the photocatalysts. The degradation rates of MB and Rh.B by 20%ωt-Bi2WO6/ZnS were as high as 94.3% and 92.8%, respectively. Moreover, the degradation performance of photocatalyst still maintained 89.3% after 4 times recycling tests. The visible light absorption ability of modified ZnS was improved, and the recombination of photogenerated electrons and holes was inhibited due to the formation of heterojunction. According to the data from density functional theory calculation, the composition of the valence band and conductive band of the Bi2WO6/ZnS system has been altered. The band gap of Bi2WO6/ZnS was reduced by roughly 1.12 eV compared to that of pure ZnS, and the work function analysis were in good agreement with the experimental results. Under light stimulation, electrons were transferred from Bi2WO6 to ZnS to produce superoxide radicals which played key roles in the degradation reaction of dyes.

Assessment of synergism between enzyme inhibition of Cu/Zn-SOD and antimicrobial photodynamic therapy in suspension and E. coli biofilm.

Antimicrobial Photodynamic Therapy (aPDT) is a treatment based on the interaction between a photosensitizer (PS), oxygen and a light source, resulting in the production of reactive oxygen species (ROS). There are two main types of reactions that can be triggered by this interaction: type I reaction, which can result in the production of hydrogen peroxide, superoxide anion and hydroxyl radical, and type II reaction, which is the Photodynamic Reaction, which results in singlet oxygen production. Antioxidant enzymes (e.g., catalase and superoxide dismutase) are agents that help prevent the damage caused by ROS and, consequently, reduce the effectiveness of aPDT. The aim of this study was to evaluate a possible synergism of the combined inhibition therapy of the enzyme Cu/Zn-Superoxide dismutase (SOD) and the methylene blue- and curcumin-mediated aPDT against Escherichia coli ATCC 25922, in suspension and biofilm. Kinetic assay of antimicrobial activity of diethydithiocarbamate (DDC) and Minimum Bactericidal Concentration (MIC) of DDC were performed to evaluate the behavior of the compound on bacterial suspension. Inhibition times of Cu/Zn-SOD, as well as DDC concentration, were evaluated via bacterial susceptibility to combined therapy in suspension and biofilm. DDC did not present MIC at the evaluated concentrations. The inhibition time and Cu/Zn-SOD concentration with the highest bacterial reductions were 30 minutes and 1.2 μg/mL, respectively. Synergism occurred between DDC and MB-mediated aPDT, but not with CUR-mediated aPDT. The synergism between Cu/Zn-SOD inhibition and aPDT has been confirmed, opening up a new field of study full of possibilities.

Protoporphyrin-sensitized degradable bismuth nanoformulations for enhanced sonodynamic oncotherapy.

Decreasing the scavenging capacity of reactive oxygen species (ROS) and enhancing ROS production are the two principal objectives in the development of novel sonosensitizers for sonodynamic therapy (SDT). Herein, we designed a protoporphyrin-sensitized bismuth-based semiconductor (P-NBOF) as a sonosensitizer to generate ROS and synergistically depleted glutathione for enhanced SDT against tumors. The bismuth-based nanomaterial (NBOF) is a wide-bandgap semiconductor. Sensitization by protoporphyrin made it easier to excite electrons under ultrasonic stimulation, and the energy of the lowest unoccupied electron orbital in protoporphyrin was higher than the conduction-band energy of NBOF. Under ultrasound excitation, the excited electrons in the protoporphyrin were injected into the conduction band of the NBOF, increasing its reducing ability leading to the production of more superoxide anion radicals and also helping to increase the charge separation of protoporphyrin leading to the production of more singlet oxygen. Meanwhile, P-NBOF continuously depleted glutathione, which was not only conducive to breaking the redox balance of the tumor microenvironment to enhance the therapeutic efficacy of SDT, but also promoted its degradation and metabolism. The construction of this P-NBOF sonosensitizer thus provided an effective strategy to enhance SDT for tumors. STATEMENT OF SIGNIFICANCE: To enhance the efficacy of sonodynamic tumor therapy, we developed a degradable protoporphyrin-sensitized bismuth-based nano-semiconductor (P-NBOF) by optimizing the band structure and glutathione-depletion ability. Protoporphyrin in P-NBOF under excitation preferentially generates free electrons, which are then injected into the conduction band of NBOF, improving the reducing ability of NBOF and promoting the separation of electron-hole pairs, thereby enhancing the production capacity of reactive oxygen species. Furthermore, P-NBOF can deplete glutathione, reduce the scavenging of reactive oxygen species, and reactivate and amplify the effect of sonodynamic therapy. The construction of the nanotherapeutic platform provides an option for enhancing sonodynamic therapy.

Elucidation of Physio-Biochemical Changes in Citrus spp. Incited by Xanthomonas citri pv. citri

India is one of the leading citrus−producing countries, next to China and Brazil. Despite the sizeable production, especially of lemons and limes, India contributes meagerly to the world’s citrus market. Of the various factors responsible for the restricted quantum of citrus export, citrus canker (Xanthomonas citri pv. citri) is one of the leading serious causes and directly impacts the appearance of the fruits. Considering the extent of damage, the present study aimed to understand the impact of Xanthomonas citri pv. citri (Xcc) on the physio−biochemical responses in contrasting Citrus spp. Two genotypes, each of three citrus species, namely Citrus aurantifolia (Pusa Udit and ALC−35), C. limon (Kagzi Kalan and Konkan Seedless), and C. paradisi (Redblush and Marsh Seedless), were artificially inoculated with Xcc (108 to 109 cfu/ mL) by the pinprick method. The physio−biochemical changes in the host were evaluated after 48 h post inoculation (hpi). The chlorophyll content (total, a, and b) degradation and reduction in leaf gas exchange parameters, such as photosynthetic rate (A), transpiration rate (E), stomatal conductance (gs), and intrinsic water−use efficiency (iWUE), were measured to a greater extent in susceptible than resistant genotypes. The microscopic observations also evidenced higher stomatal density with larger stomatal areas in susceptible genotypes, favoring the easier penetration of Xcc in host tissues than resistant species or genotypes. The higher activities of various antioxidant enzymes, viz., superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and glutathione reductase (GR), the contents of soluble protein, and phenolics were measured in resistant genotypes in contrast to susceptible genotypes. The activities of phenyl ammonia lyase (PAL) and polyphenol oxidase (PPO) were also higher in resistant genotypes, whilst the levels of ROS (superoxide radical and hydrogen peroxide) production were enhanced in susceptible genotypes. Based on the host–pathogen interaction, the order of resistance in a descending manner was found as Kagzi Kalan, Marsh Seedless, Redblush, Konkan Seedless, Pusa Udit, and ALC−35. Further, the results will enhance the understanding of the pathogen mechanism during pathogenesis in resistant and susceptible Citrus species.

A Sulfur-Bridging Sulfonate-Modified Zinc(II) Phthalocyanine Nanoliposome Possessing Hybrid Type I and Type II Photoreactions with Efficient Photodynamic Anticancer Effects

Phthalocyanines are potentially promising photosensitizers (PSs) for photodynamic therapy (PDT), but the inherent defects such as aggregation-caused quenching effects and non-specific toxicity severely hinder their further application in PDT. Herein, we synthesized two zinc(II) phthalocyanines (PcSA and PcOA) monosubstituted with a sulphonate group in the alpha position with "O bridge" and "S bridge" as bonds and prepared a liposomal nanophotosensitizer (PcSA@Lip) by thin-film hydration method to regulate the aggregation of PcSA in the aqueous solution and enhance its tumor targeting ability. PcSA@Lip exhibited highly efficient production of superoxide radical (O2∙-) and singlet oxygen (1O2) in water under light irradiation, which were 2.6-fold and 15.4-fold higher than those of free PcSA, respectively. Furthermore, PcSA@Lip was able to accumulate selectively in tumors after intravenous injection with the fluorescence intensity ratio of tumors to livers was 4.1:1. The significant tumor inhibition effects resulted in a 98% tumor inhibition rate after PcSA@Lip was injected intravenously at an ultra-low PcSA@Lip dose (0.8 nmol g-1 PcSA) and light dose (30 J cm-2). Therefore, the liposomal PcSA@Lip is a prospective nanophotosensitizer possessing hybrid type I and type II photoreactions with efficient photodynamic anticancer effects.

Influence of NF-κB on the development of oxidative-nitrosative stress in the liver of rats under conditions of chronic alcohol intoxication

Alcohol-related liver disease is the most common cause of liver disease worldwide. The purpose of this work is the establishment of the influence of the transcription factor κB on the development of oxidative-nitrosative stress in the liver of rats under conditions of chronic alcohol intoxication. The experiments were performed on 24 male Wistar rats weighing 180-220 g. The animals were divided into 4 groups of 6 animals: control; animals, which were administered NF-κB inhibitor, namely ammonium pyrrolidinedithio­carbamate (PDTC) at a dose of 76 mg/kg 3 times a week; animals, on which we simulated alcoholic hepatitis and group of combination of alcoholic hepatitis and NF-κB inhibitor. We determined in rat liver homogenate the following biochemical parameters: the activi­ty of NO synthase isoforms, superoxide dismutase and catalase activity, the concentration of malonic dialdehyde, the concentration of peroxynitrite, nitrites and nitrosothiols, concentration of sulfide anion and superoxide anion radical production. Chronic alcohol intoxication led to increased production of reactive oxygen and nitrogen species on the background of decreased antioxidant activity, thus intensifying lipid peroxidation in the liver. Blockade of the transcription factor κB during chronic alcohol intoxication despite an increase in antioxidant activity and decrease of reactive oxygen and nitrogen species production did not ameliorate oxidative damage to the liver. Blockade of activation of nuclear transcription factor κB in rat liver by PDTC reduced the risk of oxidative damage to hepatocytes, but did not reduce the risk of developing nitrosative damage to hepatocytes. Keywords: chronic alcohol intoxication, NF-κB, oxidative-nitrosative stress, PDTC, rat liver

Engineering high-coordinated cerium single-atom sites on carbon nitride nanosheets for efficient photocatalytic amine oxidation and water splitting into hydrogen

Developing highly-active rare-earth single atom photocatalysts have attracted extensive attention due to their excellent catalytic properties. Herein, we prepared a single-atom Ce-SA-C3N4 catalyst composed of atomically dispersed rare-earth cerium (Ce) on C3N4 nanosheets by the pyrolysis of cerium-incorporated layered precursor. The atomic distribution and high-coordinated environment of Ce sites were disclosed by aberration-corrected scanning transmission electron microscopy, electron energy-loss spectra, X-ray absorption spectroscopy, and theoretical calculations. In Ce-SA-C3N4, Ce single atoms are coordinated by four N atoms and six O atoms (Ce-N4/O6). The cooperation of single-atom Ce-N4/O6 active sites in C3N4 nanosheets tunes the electronic structure and the surface trap states, resulting in accelerated charge transfer/separation and extended lifetime of photoinduced electrons. Meanwhile, the high-coordinated Ce-N4/O6 active sites could promote the production of superoxide radicals (•O2−) and C = N bond, thus, the optimized single-atom Ce-SA-C3N4 photocatalyst exhibits highly efficient photocatalytic oxidation of amines under visible light irradiation. Furthermore, the fabricated single-atom Ce-SA-C3N4 photocatalysts are applied to split water into hydrogen, producing the maximum hydrogen yield of 33.5 mmol h−1 g−1. The apparent quantum efficiency for hydrogen evolution achieves 32.6% at 420 nm. This study provides a guideline for rationally designing efficient high-coordinated rare-earth single-atom active sites for efficient solar energy conversion and utilization.

Exogenous glucose reduces the incidence of black rot disease in apricot (Prunus armeniaca L.) by regulating energy metabolism and ROS

Apricot is one of the most highly consumed fruit in Xingjiang, China, but it is extremely perishable. In this study, the effects of exogenous glucose (Glu) on postharvest energy metabolism and reactive oxygen species (ROS) metabolism in the apricot fruit and its relationship to black rot disease were investigated. The results demonstrated that the disease incidence of apricot fruit inoculation and the expansion of the diameter of the disease spots were inhibited after exogenous Glu-treatment. Contrarily to the control group, exogenous Glu-treated fruits exhibited higher activities of enzymes involved in energy metabolism and ROS-scavenge system and effectively maintain the adenosine triphosphate (ATP), adenosine diphosphate (ADP), and energy charge in the apricot fruit. Simultaneously, the accumulation of adenosine monophosphate (AMP), superoxide radical (O2−) production, hydrogen peroxide (H2O2), malondialdehyde (MDA) and the electrolyte leakage was inhibited after treatment. Overall, the results suggested that exogenous Glu-treatment can effectively enhance the resistance of apricot fruit to black rot disease by regulating ROS production and energy metabolism.

Functionalization of anatase nanoparticles with Glutaric acid and their photochemical and photocatalytic properties under visible light

Charge transfer complexes (CTCs) formed between TiO2 and chelating ligands have attracted extensive attention for photocatalytic applications under visible radiation due to their increased visible light absorption. Different TiO2-based CTCs have been widely studied. However, the sensitization of TiO2 to visible light by functionalization with glutaric acid (TiO2-GA) and its photocatalytic performance under visible light radiation have not yet been investigated, as far as the authors know. In this study, visible-light-sensitive TiO2-GA nanomaterials were synthesized via sol-gel and calcined under static air at 270 °C. The as-prepared TiO2-GA CTCs were characterized by XRPD, FTIR, TGA, DRS, PL, EPR and XPS techniques. FTIR data supported the formation of the CTC through bidentate chelating interaction between TiO2 and GA. TiO2-GA CTCs calcined at 270 °C under static air exhibited a long absorption tail in the visible light spectrum mainly due to the formation of F+ centers. The high content of GA molecules bounded to the TiO2 surface was not beneficial for photocatalytic performance of the TiO2-GA CTCs, since these molecules reduced the active sites on the nanostructure surface, resulting in a lower production of superoxide radicals by the TiO2-GA CTCs. Our findings indicated that: a) TiO2-GA CTCs are capable to degrade antibiotic liquid pollutants via interactions with superoxide radicals and also, b) provided fundamental insights into the influence of bulk Ti3+ defects and bulk oxygen vacancies on photocatalytic performance and photochemical properties of TiO2-based CTCs.

Integration of nitrogen-doped carbon dots onto active layer of forward osmosis membrane for highly efficient antibacteria and enhanced membrane performances

Biofouling severely hampered the development of thin-film composite (TFC) forward osmosis (FO) membrane. Herein, novel nitrogen-doped carbon dots (N-C-dots) with fluorescence and long-lived afterglow dual-emission were fabricated using Na2EDTA and urea as co-precursors. The N-C-dots aqueous solution can synchronously produce superoxide anion radical (O2-ˑ) and singlet oxygen (1O2) under light irradiation, exhibiting immense nanoenzyme activities. The membranes (PEI-M and N-C-dots/PEI-M) were prepared by grafting PEI and N-C-dots/polyethyleneimine nanocomposites (N-C-dots/PEI) onto the active layer of pristine TFC FO membrane (Control-M), respectively. The N-C-dots/PEI-M exhibited much better hydrophilicity and smoothness than Control-M and PEI-M, resulting in a higher water permeability. Most significantly, N-C-dots/PEI-M possessed a unique dual-mode biofouling resistance, which responded to the potentials of N-C-dots as oxidase mimic and photosensitizer. In dynamic sewage treatment test, N-C-dots/PEI-M displayed much lower reduction in water flux and much better anti-biofouling behavior. Results above demonstrated that the modification strategy with N-C-dots/PEI is highly effective, pioneering a new horizon for the highly efficient inhibition of biofilm growth and biofouling development under visible light.

Algal extracellular polymeric substances (algal-EPS) for mitigating the combined toxic effects of polystyrene nanoplastics and nano-TiO2 in Chlorella sp.

The continuous release of nanoparticles and nanoplastics into the marine environment necessitates the examination of their combined effects in marine organisms. Natural Organic Matter (NOM) can significantly influence the behavior of nanomaterials in the marine environment. The present study explores the effects of algal Extracellular Polymeric Substances (EPS) in reducing the combined toxic effects of three different polystyrene nanoplastics (PSNPs)— aminated (NH2-PSNPs), carboxylated (COOH-PSNPs), and plain PSNPs — and P25 titanium dioxide nanoparticles (Nano-TiO2) towards the marine alga, Chlorella sp. Two doses (0.25 and 2.5 mg/L) of nano-TiO2 mixed with the PSNPs (1 mg/L) were employed. The COOH-PSNPs with 2.5 mg/L nano-TiO2 exhibited higher growth inhibition toward algal cells. Addition of algal EPS to the mixture of NMs decreased the negative effect significantly. The mean hydrodynamic diameter increased significantly from 666 to 797 nm and 1248 to 3589 nm at concentrations 0.25 and 2.5 mg/L, respectively when the mixtures of nano-TiO2 and COOH-PSNPs were incubated with the algal EPS. In comparison to the pristine NMs, the EPS-NMs were found to significantly reduce the superoxide and hydroxyl radical production. The results were further validated with the estimation of lipid peroxidation (LPO), esterase activity, photosynthetic efficiency, and membrane permeability in the cells. The major outcomes from this study highlight the role of algal EPS in significantly reducing the toxic impact of binary mixture of NMs in marine organisms.

Regulation and mechanism of ethylene treatment on storage quality of fresh-cut lotus (Nelumbo nucifera Gaertn.) root slices

This study investigated the effects of 1 g L−1 ethylene immersion treatment for 1 min on the storage quality, antioxidant capacity and ethylene signal transduction pathway of fresh-cut lotus roots. Phenylalanine ammonia-lyase and polyphenol oxidase activities were increased in ethylene treatment slices, and total phenolic content was increased. The activities of peroxidase, catalase and superoxide dismutase were increased after ethylene treatment, as well as the expression of related genes (NnPOD, NnSOD, NnCAT) was upregulated. The rate of superoxide anion radical and hydroxyl radical production in ethylene treatment fresh-cut lotus roots was inhibited, the hydrogen peroxide content was reduced, and the degree of membrane lipid peroxidation was decreased, which delayed browning during the early storage. However, ethylene treatment inhibited microbial growth and improved 1,1-Diphenyl-2-picrylhydrazyl scavenging capacity only during the early storage, promoted respiration and accelerated the decline of hardness and soluble solids content throughout the storage period. At the molecular level, ethylene treatment overall upregulated the transcription of NnmetK, NnACO, NnETR, NnEIN3, and NnERF genes and promoted ethylene biosynthesis and signal transduction. This finding may be related to the senescence of fresh-cut lotus roots during late storage. These results suggest that ethylene treatment improved the antioxidant system, reduced the accumulation of reactive oxygen species, and effectively delayed the early browning of fresh-cut lotus roots, while promoting late senescence.

Extrinsic Point Defects in TiO2–Acetylacetone Charge-Transfer Complex and Their Effects on Optical and Photochemical Properties

TiO2-based visible-light-sensitive nanomaterials are widely studied for photocatalytic applications under UV-Vis radiation. Among the mechanisms of visible-light sensitization, extrinsic oxygen vacancies have been introduced into TiO2 and charge-transfer complexes (CTCs) have been formed between chelating ligands, such as acetylacetone, and nanocrystalline TiO2 (TiO2-ACAC). However, the influence of extrinsic oxygen vacancies on the photocatalytic performance of TiO2-based CTCs is unknown. In this work, surface/bulk extrinsic oxygen vacancies were introduced into TiO2-ACAC through calcination at 270 °C under static air, argon, and hydrogen atmospheres. TiO2-ACAC CTCs were characterized by X-ray powder diffraction, thermogravimetric analysis, diffuse-reflectance spectroscopy, photoluminescence, electron paramagnetic resonance (EPR), and X-ray photoelectron spectroscopy techniques. The correlation between EPR-spin trapping and tetracycline (TC) photodegradation, using scavengers, highlighted the key role of the superoxide radical in TC degradation by TiO2-ACAC CTCs under low-power visible-light radiation. The increased extrinsic oxygen vacancies concentration was not beneficial for the photocatalytic performance of TiO2 CTCs, since bulk extrinsic oxygen vacancies additionally act as recombination centers. In fact, the TiO2-ACAC CTC with the lowest extrinsic oxygen vacancies concentration exhibited the highest photocatalytic performance for TC degradation due to an adequate distribution of extrinsic bulk oxygen vacancies, which led to the trapped electrons undergoing repeated hopping, reducing the recombination rates and improving the efficiency in superoxide radicals production. Our findings indicated that TiO2-ACAC CTCs are able to degrade pollutants via interactions with electronic holes and principally superoxide radicals and also, provided fundamental information about the influence of surface/bulk extrinsic oxygen vacancies on the photocatalytic performance, lattice parameters, and optical and photochemical properties of TiO2-based CTCs.

Copper Foam-Supported CuxO@Fe2O3 Core–Shell Nanotubes: An Efficient Ozonation Catalyst for Degradation of Organic Pollutants

Copper foam (CF)-supported CuxO@Fe2O3 core–shell nanotubes (CF/CuxO@Fe2O3 NTs) were synthesized as a hybrid catalyst for heterogeneous catalytic ozonation (HCO). The hybrid catalyst exhibits high activity and excellent stability for the HCO of organic pollutants. The total organic carbon removal rates of methyl orange, ibuprofen, and nitrobenzene via HCO were 89, 82, and 88%, respectively, which are over 2 times higher than the corresponding values obtained without the catalyst. The hybrid catalyst also displays wide pH operation range, low metal leaching, easy separation from treated water, and excellent recyclability. We prove that large amounts of Lewis acid sites with medium acidity are created at the CuxO/Fe2O3 interface due to the synergic effect of CuxO and Fe2O3. These medium acid sites are the main active centers for the production of free hydroxyl radicals (•OH) and superoxide radicals (O2•– or HO2•) in neutral solution. Moreover, the 3D porous framework of the catalyst enables easy dispersion in and separation from water. This work develops a new strategy to design HCO catalysts by combining strong and weak Lewis acid oxides and also opens a new avenue for developing HCO catalysts on a 3D porous framework.

2D/3D g-C3N4/BiOI heterostructure catalyst for efficient and robust photocatalytic NO removal

Developing visible light responsive photocatalysts with strong light capture ability for catalytic NO removal is of great significance. In this work, we coupled the narrow-gap semiconductor BiOI with graphite-like carbon nitride (g-C3N4) to construct 2D/3D heterostructure and applied it for efficient photocatalytic elimination of NO under visible light irradiation. At relative humidity (RH) of 15 %, g-C3N4/BiOI achieves remarkable NO removal activity (80.5 %) under a gas hourly space velocity (GHSV) of 1,740,000 mL h−1 g−1. Outstanding durability was realized that the NO removal efficiency of g-C3N4/BiOI after 6 consecutive runs. Even at high RH of 50 % and 80 %, g-C3N4/BiOI still exhibited excellent NO removal performances of 80.3 % and 78.5 %, respectively. The heterostructure of g-C3N4/BiOI endowed the enhanced light harvesting, efficient charge separation and rapid charge transfer, which enables sufficient superoxide radicals (O2−) production to improve the efficiency and strengthen the durability of photocatalytic NO removal. This work provides insights into the rational design of heterostructure photocatalyst toward air purification.