Radical Formation Research Articles

Effect mechanism of H3PO4 on the formation and transformation of persistent free radicals in biochar

Persistent free radicals (PFRs) in biochar have attracted wide attention due to their multifaceted roles in the environment. The regulation of PFRs in biochar is not only beneficial to broaden its application potential, but also eliminates its environmental risks. However, as a common biochar modification reagent, phosphoric acid (H3PO4) has not been studied in the field of PFRs regulation. Herein, this study systematically investigated the effect of H3PO4 on PFRs in biochar under various conditions. The results indicated that H3PO4 promoted the formation of PFRs in biochar at low pyrolysis temperature (< 500 °C), owing to the positive effect of catalytic cross-linking on the degradation of biomass precursor. Yet, H3PO4 reduced PFRs in biochar at high pyrolysis temperature (≥ 500 °C), since the capture of H∙ or HO∙ by PO∙ and the steric hindrance changed by H3PO4, which caused the rearrangement and polycondensation of carbon structure. H3PO4 also favored carbon-centered PFRs as the dominant type. The ingredients of biomass precursor, including cellulose, Fe, Ti, protein, etc., contributed to different effects on PFRs under H3PO4 modification. This study provided new insights into the roles of H3PO4 on the formation and transformation of PFRs in biochar, coupled with regulation strategies in the practical application.Graphical

NXS/TBHP as a Reagent System for Expedient Generation of Halogen Radicals: Site-Selective Halogenation of Quinoxalin-2(1H)-ones and Conversion of Terminal Alkynes to gem-Dihaloketones.

We report an efficient and practical protocol for the generation of halogen (Br and Cl) radicals using inexpensive and readily available N-bromo/N-chlorosuccinimide (NXS) and t-butylhydroperoxide (TBHP) at rt. The NXS/TBHP reagent systems are demonstrated for site-selective bromination and chlorination of the benzene-core of quinoxalin-2(1H)-ones. It is shown that the reagent system permits regioselective halogenation at the C7 position of the benzene core over the readily-functionalized C3 position of quinoxalin-2(1H)-ones under mild reaction conditions. We further show that terminal alkynes can be converted to gem-dihaloketones in a facile manner by NXS/TBHP. Mechanistically, single electron transfer between TBHP and NXS leads to instantaneous formation of electrophilic halogen radicals, which attack arenes and alkynes.

Recent advances in surface charge dynamics in dielectric barrier discharge: future strategies for control and technological optimisation

Abstract Dielectric barrier discharges (DBDs) using atmospheric pressure plasma are utilised in various industries, including environmental remediation, semiconductor manufacturing, and energy technology. It is crucial to understand and regulate their properties for technological optimisation. Of particular significance is the surface charge generated by DBDs, as it is the primary physical factor that determines the electric field in the plasma, resulting in overcurrent suppression and radical formation. This study explores recent advancements in research concerning the dynamic properties of surface charge and examines future strategies for optimising DBDs and achieving real-time surface charge control.

A Photo-Smiles Rearrangement: Mechanistic Investigation of the Formation of Blatter Radical Helicenes.

Photocyclization of 8-aryloxy-3-phenylbenzo[e][1,2,4]triazines leads to helicene radicals. Structural analysis of radicals leuco forms by two-dimensional correlation nuclear magnetic resonance methods demonstrated that the photocyclization involves a Smiles rearrangement and exclusive formation of a single rearranged product for all substrates. Density functional theory investigations indicate that the mechanism requires the T1 state with (n, π*) character localized on the benzo[e][1,2,4]triazine (BT) fragment and at least one occupied π molecular orbital (MO) localized on the aryloxy fragment with an energy that is higher than that of the n MO. This electronic structure is favorable for aryl-to-BT single-electron transfer and formation of a zwitterion, which undergoes an intramolecular polar cyclization followed by ring opening of the resulting spirooxazole. The proposed mechanism represents a new variation of photo-Smiles rearrangement and appears to be general for the photochemical formation of planar Blatter radicals.

C-H Arylation of Aminoquinones through Electrochemical Denitrogenative Coupling.

An electrooxidative C-C coupling between arylhydrazines and aminoquinones has been developed for the construction of aryl-substituted aminoquinones, which features excellent chemo- and regioselectivity. Mechanistic studies support the idea that the denitrogenative formation of aryl radicals might be involved in the metal-free C-H arylation.

In Situ 2D-XAS Imaging and Modeling Analysis of Cerium Migration in Proton Exchange Membrane Fuel Cells

Abstract In-situ two-dimensional X-ray absorption spectroscopy (XAS) imaging was employed to analyze cerium ion (Ce3+) migration in the through-plane direction in proton exchange membrane fuel cells (PEMFCs), offering fundamental insights supporting improvement of their power density and membrane durability. The transport of Ce3+ was visualized in both unreinforced thick Nafion membranes (Nafion 115, 127 µm) and reinforced thin (12 µm) perfluorosulfonic acid (PFSA) membranes under either an electrical potential gradient or a water activity gradient. The diffusion coefficients of Ce3+ were ascertained based on its behavior after removal of these gradients in both membrane types. Additionally, using a one-dimensional cation transport model, the mobility and electroosmotic drag coefficients of Ce3+ were derived from experimentally obtained data of the thick Nafion membrane. Our measurements also demonstrate that the migration of Ce3+ in the thick membranes was notably impeded by the presence of ferrous ion (Fe2+) impurities. Because Fe2+ is known to accelerate membrane degradation by promoting hydroxyl radical formation, this effect might further exacerbate membrane degradation. It therefore warrants careful consideration.

Abolitionist Ecological Security

As ecological crises deepen, many scholars have challenged dominant practices of security by developing more progressive environmental or ecological security discourses. Others, on the other hand, critique these moves by emphasizing the inherently repressive features of security discourse. This article engages this debate by proposing a more radical form of ecological security informed by the ‘abolitionist’ tradition – which I call Abolitionist Ecological Security. From this view, the problem with existing ecological security approaches is not their efforts to rethink the term ‘security’, but rather (1) their failure to foreground the political economy of racial capitalism as the structure that hegemonic security practices function to secure, and (2) their neglect of how ‘racial capitalist security assemblages’ – encompassing structures of militarism, policing, incarceration and border controls – produce ecological insecurity through their ecological impacts and violence against workers, the poor, migrants and racialized communities. Thus I argue, following the abolitionist tradition, that any genuine ecological security must necessarily be abolitionist in orientation, entailing the struggle for new worlds beyond racial capitalism and the creation of alternative security practices beyond militarism, policing and imprisonment.

Selective nitric oxide redistribution by phospholipid nanoparticles: A novel strategy to mitigate massive nitric oxide release and prevent reperfusion injury in septic shock.

Nitric oxide plays a critical role in regulating vascular tone, but excessive nitric oxide release during septic shock results in hypotension due to excessive vasodilation and the formation of toxic free radicals. VBI-S is a phospholipid nanoparticle based fluid composed of lipid bilayers formed primarily by phosphatidylcholine and micelles of soybean oil encapsulated by a monolayer of phosphatidylcholine. These nanoparticles offer a novel solution by absorbing and redistributing nitric oxide and nitrite, potentially mitigating the harmful effects of excessive nitric oxide in sepsis. This paper proposes a mechanism in which VBI-S not only redistributes nitric oxide but also reduces ischemia-reperfusion injury by limiting the production and availability of reactive species. VBI-S captures nitric oxide and nitrite in areas of high concentration and redistributes them in low-nitric oxide environments, primarily within oxygen-deprived tissues. Nitrite then contributes to nitric oxide regeneration in hypoxic microvasculature via various reduction pathways, thereby improving tissue perfusion and minimizing oxidative stress. Preliminary studies suggest that nitrite may also decrease reactive species production, primarily superoxide, through the inhibition of mitochondrial complex I. Additionally, the lipid composition of VBI-S is rich in poly and monounsaturated fatty acids which allows VBI-S to act as a substrate for peroxidation via peroxynitrite. Therefore, VBI-S acts as a decoy target thereby protecting cellular membranes from oxidative damage caused by reactive species. These findings position VBI-S as a promising therapeutic agent, offering both nitric oxide regulation and protection against hypotension and toxic free radicals in septic shock patients. Further research is necessary to fully elucidate the molecular pathways and optimize its clinical application.

Terpene speciation: Analytical insights into the oxidation and pyrolysis of limonene and 1,8-cineole via molecular-beam mass spectrometry

Comprehensive speciation datasets for the stoichiometric oxidation and pyrolysis of the two monoterpenes limonene (C10H16) and 1,8-cineole (C10H18O) are measured in an atmospheric laminar flow reactor using electron-ionization molecular-beam mass spectrometry. This setup allows direct sampling from the reactive flow and preserves the actual gas composition. Furthermore, clear determination of the exact elemental composition of the formed species is possible with the used time-of-flight mass spectrometer. Limonene is a monocyclic terpene and 1,8-cineole is a saturated bicyclic terpene ether and both terpenes might be potential biofuel candidates. Focus in this study is the intermediate temperature region between 673 and 1173 K to obtain insights into the first fuel decomposition steps and the formation of typical soot precursors. The obtained mole fraction profiles for over 40 species in each of the investigated terpenes are a first step for future development and validation of chemical kinetic combustion mechanisms. While the overall species pool is similar, significant concentration differences can be observed for certain combustion intermediates. For limonene, larger quantities of C8–C10 hydrocarbons are detected and most of them are probably substituted benzenes or cyclohexadienes formed from hydrogen abstraction. Some reaction steps in the decomposition of limonene may also involve initial isomerization of the fuel molecule. In contrast, direct formation of C7H11 radicals and acetone (C3H6O) is identified as an important decomposition step of 1,8-cineole. C7H11 is then a source of toluene (C7H8) and cyclohexadienes (C6H8). Generally, a higher sooting propensity of limonene compared to 1,8-cineole can be expected due to the higher concentrations of polycyclic aromatic hydrocarbons (PAHs) in the investigated temperature range. During limonene oxidation, formation of oxygenated species larger than the fuel molecule are observed and might represent carbonyls or cyclic ethers from the first oxygen addition due to low-temperature chemistry.

Novel S-scheme based nanocomposite of MXene/V2O5 for environmental remediation towards sustainable development: An insight into influencing parameters.

In this study, a novel 2D/2D nanocomposite of MXene and V2O5 was synthesized using a facile hydrothermal approach for the efficient removal of crystal violet (CV), a textile dye from contaminated water to achieve Sustainable Development Goal (SDG) 14; "Save Lives Below Water". Here, the catalytic performance of pristine MXene was prominently boosted with the introduction of ball milled V2O5 as an electron generating agent. The degradation efficiency of synthesized nanocomposite significantly enhanced from 57 % to 92 %, 41 % - 76 % and 7 % - 58 % with an error of ±2 % as compared to pristine MXene at 10, 20 and 30ppm concentrations of CV, respectively. The effective degradation of pollutants is ascribed to the electron-transfer via S-scheme based mechanism and helps in reducing recombination rate of photogenerated carriers, which could produce hydroxyl radicals (OH.) as a primary species for effectively degradation of pollutants. The superior performance of nanocomposite is attributed to: (i) the optimized surface charge (-27.8mV), (ii) small value of charge transfer resistance (Rct=1.3Ω), (iii) enhanced value of carrier concentration (6.3 X 1032cm-3), (iv) small recombination rate of excitons and (v) high specific surface area as compared to pristine samples. Moreover, to strengthen the findings, scavenger study and electron paramagnetic resonance (EPR) study were carried out and concluded that hydroxyl radicals (OH.) are the primary species in the mineralization of CV dye. The values of lande g-factor are calculated using EPR plots which comes out to be 2.03 and 2.04 for (O2.-) and (OH.) radicals, respectively and demonstrates the formation of free radicals during catalytic reactions. The Chemical Oxygen Demand (COD) analysis was carried out before and after the removal of CV using MV nanocomposite and confirms the reduction in COD vlaue of 81.60 %. The reusability experiment confirms stability of synthesized sample and provides a good shred for industrial applications in the treatment of wastewater and getting out cleaner productions and to save marine ecosystem.

Electron paramagnetic resonance spectroscopy: toward the path of dihydrogen isotopologue detection in porous materials.

Electron paramagnetic resonance (EPR) spectroscopy is a powerful method to characterize the local framework structure of nanoporous materials during the dihydrogen isotopologue adsorption process. It also allows for exploring the adsorption sites of the dihydrogen isotopes and monitoring their desorption characteristics on the microscopic scale. The paramagnetic spin probes in the form of transition metal ions or organic radicals are required for EPR spectroscopy and are introduced either at the framework lattice position or in the pores of the metal-organic frameworks. This review highlights current advancements within the field of dihydrogen isotopologue detection as well as key findings related to the versatility of in situ continuous wave EPR and pulsed EPR experiments as toolkits for monitoring the adsorption-desorption process of dihydrogen isotopologues from the perspective of the framework as well as studying the host-guest interactions based on high-resolution advantages offered by using a pulsed EPR approach.

Triazole Drives Hole Localization and Superoxide Radical Formation for Enhancive Photocatalytic Cascade Isomerization/C─C Bond Scission of Biomass to Lactic Acid.

Chemocatalytic synthesis of lactic acid (LA) from biomass sugars involves heat-absorbing multistep cascade reactions mediated by different active sites, often encountering unsatisfactory selectivity. Here, a hole-localized carbon nitride-based photocatalyst (C-CNN) is constructed by covalent binding of heptazine and triazole skeleton via C─N bonds and further conjugated interaction with activated carbon, achieving the complete conversion of various biomass sugars to LA (up to 98.6% selectivity) at room temperature for 2h. The introduced triazole electron donor in C-CNN can not only enhance the adsorption of sugar for the enhanced aldose-to-ketose isomerization over the localized hole (Lewis acid) on the triazole skeleton, but also modulate the valence band oxidation to circumvent the formation of •OH but only •O2 ‒ for selective C3‒C4 cleavage of ketose, thus realizing the exclusive synthesis of LA. Moreover, near-infrared light absorption endowed by activated carbon can supply sufficient interface photothermal effect for ambient LA production. Life cycle assessment shows that the photocatalytic system has good prospects for industrialization in terms of both energy and environment. This work offers novel insights into the multidirectional utilization of solar energy for the value-added conversion of biomass through rational modulation of photothermal active sites.

Plasma-driven synthesis of nitrogen-doped graphene: unveiling the reaction mechanism and kinetic insights.

The rotating arc plasma technique for the synthesis of nitrogen-doped graphene capitalizes on the distinctive attributes of plasma, presenting a straightforward, efficient, and catalyst-free strategy for the production of nitrogen-doped graphene. However, experimental outcomes generally fail to elucidate the atomic-level mechanism behind this process. Our research utilizes molecular dynamics simulations to explore theoretically the formation of radicals during the plasma-driven reaction between methane (CH₄) and nitrogen (N₂). The simulations present a complex reaction system comprising nine principal species: CH₄, CH₃, CN, CH₂, HCN, CH, N₂, H₂ and H. Notably, HCN and CN emerge as pivotal precursors for nitrogen doping. Optimal nitrogen concentrations enhance the synthesis of these precursors, whereas excessive nitrogen suppresses the formation of C₂ species, impacting the yield of nitrogen-doped graphene. Conversely, higher methane concentrations stimulate the generation of carbon radicals, augmenting the production of HCN and CN and thus, influencing the properties of the synthesized material. This work is expected to lay a theoretical foundation for the refinement of nitrogen-doped graphene synthesis processes. In this investigation, we employed the LAMMPS software package to explore the formation of free radicals during the methane-nitrogen reaction via molecular dynamics (MD) simulations. These simulations were conducted under an NVT ensemble, maintaining a constant temperature of 3500K with a time step of 0.1fs over a duration of 1000ps. To reduce the variability and enhance the reliability of the simulation outcomes, each simulation was meticulously conducted three times under identical parameters for subsequent statistical analysis.

Study of the chloroformic extract of Gnaphaliumspin a model of alloxan-induced diabetes in Wistar rats. An alternative use of the “gordolobo” plant within traditional Mexican medicine

“Gordolobo”(Gnaphalium sp) is a Mexican medicinal plant understudied for the treatment of diabetes; therefore, the aim was to evaluate the chloroformic extract of G sp. (CEG) in alloxan-induced diabetic rats. Sesquiterpene lactones, polyphenolic compounds, triterpenes and steroids, apigenin, and lauric and myristic acid were identified in CEG by phytochemical, HPLC and GC-MS analysis; and the antioxidant capacity evaluated by FRAP, DPPH and ABTS, inhibited the formation of free radicals. There was no lethality or toxicity at doses of 2000 mg/kg. At doses of 200 mg/kg it did not decrease hyperglycemia; however, it did decrease biomarkers of oxidative stress (malondialdehyde, oxidized proteins, superoxide dismutase) associated with diabetes in pancreas. The β-cell function, insulin resistance and insulin sensitivity were not improved. In conclusion, CEG showed no hypoglycemic activity, but antioxidantactivity in pancreatic tissue.

Collaborative modification strategy to improve the formation of biochar-derived persistent free radicals for aniline removal via peroxymonosulfate activation

This study explores a novel approach to biochar modification aimed at increasing persistent free radical (PFR) formation on biochar surfaces, thereby enhancing aniline removal via peroxymonosulfate (PMS) activation. By adjusting pyrolysis temperatures and doping ratios, optimal conditions were established. Spearman's analysis highlighted the importance of C=C bonds, the ID/IG ratio, and pyridinic N in generating PFRs. The modified biochar derived at 500 ℃ (MB500), in conjunction with the PMS system demonstrated impressive efficiency, achieving 92% aniline removal within 30 min. Detailed adsorption tests and active species detection indicated that aniline degradation occurred through both direct oxidation by PFRs and indirect oxidation by reactive species, particularly superoxide radicals (O₂⋅⁻). Furthermore, the synergistic effects of heteroatom nitrogen and Na2CO3 modifications significantly impacted PFR formation and stability. These findings provide valuable insights into the mechanisms of PFR-mediated catalytic oxidation, highlighting the key roles of pyridinic rings, with or without oxygenated groups, in enhancing catalytic performance of biochar. This research advances the understanding of biochar surface chemistry and presents an effective strategy for developing high-performance biochar-based catalysts for environmental remediation, addressing the limitations of unmodified biochar through targeted surface modifications.Graphical

Ring Opening and C(ω)‐S Coupling: Nickel‐Mediated Transformation of Alicyclic Alkoxyhydroperoxides

AbstractOzonolysis of cycloalkanone semicarbazones in alcohol containing solution with the subsequent addition of nickel (II) dithiocarbamates or xanthates was found to result in ω‐xanthyl or ω‐dithiocarbamyl carboxylic acid esters. The reaction proceeds in several steps. The initial one is cycloalkanone semicarbazone ozonolysis in the presence of alcohol, which leads to alicyclic alkoxyhydroperoxide. The second step is an extraordinary interaction between the alkoxyhydroperoxide and nickel (II) dithiocarbamate or xanthate, which proceeds via alkoxy radical formation and its subsequent β‐scission, resulting in C−S coupling products. The developed method allows to obtain ω‐xanthyl or ω‐dithiocarbamyl esters in yields up to 52 % relative to the initial cycloalkanone semicarbazone.

Kombucha fortified with Cascade hops (Humulus lupulus L.): enhanced antioxidative and sensory properties

In recent years, there has been a surge in the production of kombucha—a functional beverage obtained via microbial fermentation of tea. However, fresh, unpasteurized kombucha is sensitive to quality deterioration as a result of, among other factors, oxidation. The addition of hops seems to be promising, due to their antioxidative properties, which may improve the stability of kombucha. However, aiming at retaining the highest antioxidative properties of kombucha, it remains unclear at which stage of the production process hops should be added. The study investigated the effect of hop supplementation during kombucha production on the basic physicochemical, antioxidative, and sensory properties of kombucha. Cascade hops in the concentrations 0.5 and 2 g/L were added at the onset of tea infusion and to the fresh, unpasteurized kombucha. The addition of hops (particularly at the pre-fermentation stage of production) led to a significant decrease in radical formation in the produced kombucha measured by electron spin resonance spectroscopy (ESR), which correlated with the higher DPPH antiradical activity and the elevated bitter α-acid content. From the sensory perspective, the post-fermentation addition of hops to kombucha resulted in a significantly higher rating of the overall quality. This enhancement was directly associated with heightened bitterness, increased presence of fruity and citrusy aromas, and a simultaneous reduction in the intensities of acetic and tea-related attributes. The data presented in this study are relevant for kombucha producers, who want to deliver a sensory-novel product in combination with an improved oxidative stability.Key points• Hop addition in kombucha production improves the antioxidative activity of the beverage.• Hop α-acids display higher antioxidative properties in kombucha than polyphenols.• Oxidative stability of kombucha fortified with hops depends on the timing of hops addition.• Hop addition enriches the taste and aroma attributes of kombucha.

Vertical Gradient of Nitryl Chloride and Implications for Atmospheric Photochemistry in Pearl River Delta, China, during Wintertime.

Nitryl chloride (ClNO2) is a key precursor of chlorine radicals, influencing atmospheric oxidation and secondary pollutants formation. Few studies have examined the ClNO2 chemistry from the perspective of the planetary boundary layer. Here, we conducted a vertically resolved investigation of ClNO2 at six heights (ranging from 5 to 335 m) on a 356 m tower in the Pearl River Delta, China, during winter 2021. Nocturnal ClNO2 is notably lower at the surface than the upper layers, with the nocturnal median concentration at 220 m (51 parts per trillion by volume, pptv) being approximately three times higher than that recorded in the surface layer (16 pptv). Observation-constrained box model simulations show that the NO gradients primarily account for the vertical disparities. Compared to the hydroxyl radical (OH) production via the nitrous acid and ozone photolysis, ClNO2 photolysis contributes to radical formation by 3.8% (1.8%) at 220 m (5 m) in the morning (07:00-08:00), indicates the enhanced significance of ClNO2 chemistry aloft compared with the ground, and may cause the underestimation of ClNO2 photolysis impacts if solely relying on surface measurements. We highlight that more field studies are needed to elucidate ClNO2 chemistry across the boundary layer.

Photoacid-Catalyzed Esterification of Carboxylic Acids Using Eosin Y.

A photoacid-catalyzed method for esterification is proposed wherein eosin Y is introduced as a photoacid and photoredox catalyst that can be activated with visible light and catalyze the esterification of carboxylic acids. The strategy presented here revealed that proton-coupled electron transfer (PCET) between eosin Y and carboxylic acid might facilitate the formation of a transient ketyl radical. This ketyl radical would subsequently undergo a single electron transfer and then couple with alkyl alcohols, yielding carboxylic esters in good to excellent yields.

On limited communitarianism: Matolino’s thinking and the changing African world

In the corpus of African philosophy, Bernard Matolino has made a substantial contribution to the development of communitarian theory, offering a fresh perspective on the concept. While his predecessors, such as Ifeanyi Menkiti and Kwame Gyekye, proposed radical and moderate forms of communitarianism, Matolino argues that these accounts are inadequate in capturing the rapidly evolving African reality. For instance, Menkiti’s radical communitarianism emphasized the community’s role in shaping individual identity, whereas Gyekye’s moderate approach sought to strike a balance between individual and communal interests. In response, Matolino introduces the concept of limited communitarianism, which acknowledges the dynamic nature of African societies and offers a more nuanced understanding of communitarianism. This concept recognizes that communities are not static entities but rather adapt to changing circumstances, and, thus, our understanding of communitarianism must also evolve. This article serves as a timely reminder to scholars and theorists of communitarianism to re-examine their assumptions and approaches to the African reality with a more nuanced and adaptable perspective. It underscores the importance of recognizing the complexities of our past, acknowledging the diversity of our present, and envisioning a future that is responsive to the changing needs and aspirations of African communities. By doing so, we can move beyond dogmatic and rigid interpretations of communitarianism and instead embrace a more inclusive and dynamic understanding of African reality.