Electron Paramagnetic Resonance Research Articles

Abstract 4140122: Bioengineered Self-Adhering Electrospun Nanoscaffolds to Deliver Mitochondrial Antioxidant, JP4-039

Introduction: Treatment of pathologic remodeling and subsequent decline in cardiac function post-myocardial infarction (MI) remains limited. Our lab has previously demonstrated that the targeted mitochondrial antioxidant, JP4-039 (JP4), can abrogate post-MI remodeling and decline in cardiac function, and that JP4 released from electrospun nanoscaffolds improved proliferation and migration of coronary vascular endothelial cells in vitro . The aims of this study were to develop a suture-free, bioadhesive electrospun nanoscaffold that will adhere post-MI cardiac tissue and reliably release JP4 in a localized manner. Hypothesis: Plasma treatment of JP4-loaded biocompatible electrospun nanoscaffold will adhere to cardiac tissue and deliver active moiety of JP4. Methods: A 2% poly(l-lactide-co-glycolide) (PGLA) was electrospun with and without 1% JP4. Nanoscaffolds then underwent plasma treatment for one minute followed by a force adhesion assay. SEM imaging and electron paramagnetic resonance ( EPR ) assays before and after plasma treatment of both control and JP4-loaded patches were performed to examine patch consistency and ensure the release of the unaltered, active structure of JP4. Results: JP4 loading and plasma treatment did not affect fiber dimeter of the scaffolds (p > 0.5 for all; Fig. 1B). JP4-loaded patches demonstrated similar release pattern of the antioxidant’s nitroxide moiety by displaying a characteristic triple peak both before and after plasma treatment as determined by EPR (Fig. 1C). Plasma-treated patches demonstrated significant increase in force adhesion compared to non-treated patches in both the control and JP4-loaded scaffolds (p < 0.0001) (Fig. 1A.). No significant difference in force adhesion was observed between the plasma treated control and JP4 loaded patch (p > 0.05) as determined by ANOVA (Fig. 1A). There was no significant difference in force adhesion between one minute and two minutes of plasma treatment (p > 0.05; Fig. 1A lower panel). Conclusion: The findings demonstrate that plasma-treated biocompatible JP4-loaded patches may reliably adhere to cardiac tissue and release the bioactive component of the mitochondrial antioxidant, JP4.

Copper Versatility in Hydroxyapatite: Valence States, Clusters, and Optical Absorption Properties.

The solid-state reaction between a stoichiometric hydroxyapatite (HA) and CuO at temperatures above 1100 °C produces pure Cux-HA phases for x ≤ 0.7 with the general formula Ca10CuIx(PO4)6(OH)2-xOx. The Cu atoms are located at the center of the hexagonal tunnels between two hydroxyl ligands, as determined by Fourier analysis based on XRD data. During heat treatment, the reduction of Cu2+ ions into Cu+ is concomitant with the stabilization of copper in HA in the hexagonal tunnel. The incorporation of monovalent copper within the apatite, as revealed by XANES spectroscopy, explains the violet color of the samples. The incorporation of Cu+ ions, by substitution of a hydrogen atom by copper(I), results in the formation of linear O-Cu-O chains where the majority of which are isolated for x ≤ 0.3. In addition, the EXAFS investigation showed, thanks to the linear geometry of these clusters that results in multiple diffusion effects, the existence of [CuO]n chains with n ≥ 2, which only appear clearly for higher copper contents x ≥ 0.5. The strong covalency of the Cu-O bond in such a dumbbell configuration would lead to strong hybridization between the 3d and 4s orbitals of copper and the 2p orbitals of oxygen, as illustrated by ESR signals. In the case of Cu-doped HA prepared by coprecipitation and annealed at a lower temperature (T ≤ 600 °C), copper substitutes calcium according to the theoretical formula Ca10-xCux(PO4)6(OH)2, mainly at the Ca(2) site. This local environment is in line with the Jahn-Teller distortion induced by the Cu2+ ion (as evidenced by UV-vis-NIR, XPS, and XANES-EXAFS spectroscopy analyses) and also allows copper-copper interactions from one site to another, as observed by ESR spectroscopy. This versatility of copper in HA gives it optical properties that change from a violet color with near-IR absorption to a blue hue. In all cases, Cu-O-Cu interactions persist whatever the valence state, and heat treatment induces a redox phenomenon, with copper exchanging between two sites close to each other.

Frustrated Radical Pairs: From Fleeting Intermediates to Isolable Species.

We present the design and comprehensive investigation of stable para-substituted triarylamine-2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) radical ion pairs (RIPs) generated via single-electron transfer (SET). We quantified the degree of SET in both solution and solid phases, utilising a suite of spectroscopic techniques including IR, EPR, NMR, and single-crystal X-ray diffraction (SC-XRD). Our findings reveal that the extent of SET is significantly influenced by the nature of the substituents (MeO > tBu > Br) and the polarity of the solvent (MeCN > DCM > toluene). The radical ion pair [(pMeOPh)3N]•+[DDQ]•- was unambiguously identified using EPR and UV-vis spectroscopy, and its structure was confirmed by SC-XRD. Detailed analysis indicates an open-shell singlet ground state with a thermally accessible triplet state, as corroborated by EPR, magnetic susceptibility measurements, and DFT calculations. This study offers crucial insights into the mechanistic pathways of RIP formation and tuning both in solution and solid states, laying the groundwork for future exploration of their reactivity and potential applications.

Continuous-Flow Electron Spin Resonance Measurements of Hydroxyl Radicals Produced during Photocatalytic Water Oxidation

Continuous-Flow Electron Spin Resonance Measurements of Hydroxyl Radicals Produced during Photocatalytic Water Oxidation

Mn-Fe Dual-Metal Assemblages on Carbon-Coated Al2O3 Spheres for Catalytic Ozonation Oxidation: Structure, Performance, and Reaction Mechanism.

Catalysts with high catalytic activity and low production cost are important for industrial application of heterogeneous catalytic ozonation (HCO). In this study, we designed a carbon-coated aluminum oxide carrier (C-Al2O3) and reinforced it with Mn-Fe bimetal assemblages to prepare a high-performance catalyst Mn-Fe/C-Al2O3. The results showed that the carbon embedding significantly improved the abundance of surface oxygen functional groups, conductivity, and adsorption capacity of γ-Al2O3, while preserving its exceptional mechanical strength as a carrier. The prepared Mn-Fe/C-Al2O3 catalyst exhibited satisfactory catalytic ozonation activity and stability in the degradation of p-nitrophenol (PNP). Electron paramagnetic resonance (EPR) and quenching experiments reveal that radical ( ⋅ OH and ⋅ O2 ⋅ ) and nonradical oxidation (1O2) dominated the PNP degradation process. Theoretical calculations corroborated that the anchored atomic Fe and Mn sites regulated the local electronic structure of the catalyst. This modulation effectively promoted the activation of O3 molecules, resulting in the generation of atomic oxygen species (AOS) and reactive oxygen species (ROS). The economic analysis on Mn-Fe/C-Al2O3 revealed that it was a cost-competitive catalyst for HCO. This study not only deepens the understanding on the reaction mechanism of HCO with transition metal/carbon composite catalysts, also provides a high-performance and cost-competitive ozone catalyst for prospective application.

The contribution of methyl groups to electron spin decoherence of nitroxides in glassy matrices.

Long electron spin coherence lifetimes are crucial for high sensitivity and resolution in many pulse electron paramagnetic resonance (EPR) experiments aimed at measuring hyperfine and dipolar couplings, as well as in potential quantum sensing applications of molecular spin qubits. In immobilized systems, methyl groups contribute significantly to electron spin decoherence as a result of methyl torsional quantum tunneling. We examine the electron spin decoherence dynamics of the nitroxide radical 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) in both a methyl-free solvent and a methyl-containing solvent at cryogenic temperature. We model nitroxide and solvent methyl effects on decoherence using cluster correlation expansion (CCE) simulations extended to include methyl tunneling and compare the calculations to experimental data. We show that by using the methyl tunneling frequency as a fit parameter, experimental Hahn echo decays can be reproduced fairly well, allowing structural properties to be investigated in silico. In addition, we examine the Hahn echo of a hypothetical system with an unpaired electron and a single methyl to determine the effect of geometric configuration on methyl-driven electron spin decoherence. The simulations show that a methyl group contributes the most to electron spin decoherence if it is located between 2.5 and 6-7Å from the electron spin, with its orientation being of secondary importance.

Singlet Oxygen Photocatalytic Generation by Silanized TiO2 Nanoparticles

AbstractA commercial TiO2 sample, used as received or hydrothermally treated to increase surface hydroxylation, has been functionalized by surface modification with hexadecyltrimethoxysilane. The anchoring of the silane has been characterized by means of FTIR and solid‐state NMR spectroscopies, and the grafting density was determined by thermogravimetric and N2 physisorption analyses. The silane moieties induce a partial decrease of the shielding of the valence electrons of the Ti ions at the surface, and a local modification of their crystal field, as demonstrated by XPS and UV/Vis spectroscopy, respectively. The changes in coordination and the produced oxygen vacancies result in the formation of Ti3+ defects localized in the sub‐surface region, as revealed by EPR spectroscopy. These paramagnetic centers are stabilized in the silanized samples, as the electron transfer to O2 is efficiently inhibited even under UV irradiation. However, the amount of Ti3+ centers appears to be correlated with the singlet oxygen (1O2) formation rate. Accordingly, epoxidation of limonene under UV light, chosen as a model photocatalytic reaction triggered by 1O2, occurred with higher selectivity when TiO2 was silanized and upon simultaneous NIR irradiation. These evidences suggest that in the silanized sample 1O2 may be generated through Förster‐type energy transfer from excited sub‐surface Ti3+ centers.

Radicals in Annulation of Mixed Benzoyl Phosphonium‐Iodonium Ylide and Acetylenes Explored by EPR‐ST Spectroscopy

AbstractAnnulation of mixed phosponium‐iodonium ylides and compounds with a triple bond is an interesting example of the synthesis of different types of heterocycles in one‐pot, metal‐free systems at ambient temperature to give substituted oxazoles in the reaction with nitriles and phosphorus‐containing λ5‐phosphinolines and substituted furans in the reaction with acetylenes. The iodonium group in the mixed ylides provides the possibility for the radical initiation of the reaction. Herein, we investigated the generation of primary radicals and the formation of phosphorus‐containing products in the photolysis of benzoyl phosphonium‐iodonium ylide alone and in its reaction with acetylenes in DCM by EPR and 31P NMR spectroscopies with the use of two most popular spin traps, PBN and DMPO. The results allowed us to account the crucial difference in the registered radicals in the two systems for the aggregation of the components, with ylide molecules forming a core and acetylene molecules being a shell of the aggregates in DCM, in which the annulation occurs. The peculiarities of the reactions of PBN and DMPO with generated radicals are discussed.

Stable Mono‐radical and Triplet Diradicals Based on Allylic Radical‐Embedded All‐benzenoid Polycyclic Hydrocarbons

High‐spin organic radicals are notable for their unique optical, electronic, and magnetic properties, but synthesizing stable high‐spin systems is challenging due to their inherent reactivity. This study presents a novel strategy for designing stable high‐spin polycyclic hydrocarbons (PHs) by incorporating allylic radical into fused aromatic benzenoid rings. To enhance stability, large steric hindrance groups with a synergistic captodative effect were added to the allylic radical centers. This approach was applied to synthesize derivatives of two open‐shell all‐benzenoid PHs: benzo[fg]tetracene (1) and dibenzo[fg,lm]heptacene (2). Both compounds exhibited excellent stability, with diradical 2 showing a half‐life of up to 17.2 days under ambient conditions. Bond length analysis and theoretical calculations suggest that 1 and 2 predominantly feature Clar’s aromatic sextet structures with embedded allylic radicals. Compound 2 was confirmed to have a triplet ground state through DFT calculations and experimental methods, including pulse EPR spectroscopy and SQUID measurements. This work introduces a new design strategy for stable high‐spin hydrocarbons, paving the way for future developments in high‐spin organic materials.

Rational Design of Crystalline and Enantiomerically Pure Helicenes with Open-Shell Singlet Ground States.

Helicene diradical derivatives have attracted widespread attentions because of their unique magnetic and chiroptoelectronic properties, however, crystalline and enantiomerically pure forms of helicene diradicals are extremely rare. Herein, we describe the rational design and synthesis of o-quinone functionalized helicene diradicals with crystalline enantiomerical purity. Diradical dianion salt Rac-3K and its enantiomers P/M-3K were obtained by reduction of corresponding precursors Rac-3 and P/M-3 with two equivalent potassium graphite in THF in the presence of (di)benzo-18-crown-6. Neutral dioxoborocyclic helicene diradicals (Rac-3B and P/M-3B) were produced by reactions of Rac-3 or P/M-3 with chlorobis(perfluorophenyl)borane (B(C6F5)2Cl. Crystal structures of compounds Rac-3K, Rac-3B and P/M-3K were obtained by single crystal X-ray diffraction. Their open-shell singlet state ground states were confirmed by electron paramagnetic resonance (EPR) spectroscopy, superconducting quantum interference device (SQUID) measurements and theoretical calculations. Their chiroptical properties were investigated by the electronic circular dichroism (ECD) spectroscopy. This work provides the first examples of enantiopure helicene diradical dianions and boron-containing helicene diradicals.

Rational Design of Crystalline and Enantiomerically Pure Helicenes with Open‐Shell Singlet Ground States

AbstractHelicene diradical derivatives have attracted widespread attentions because of their unique magnetic and chiroptoelectronic properties, however, crystalline and enantiomerically pure forms of helicene diradicals are extremely rare. Herein, we describe the rational design and synthesis of o‐quinone functionalized helicene diradicals with crystalline enantiomerical purity. Diradical dianion salt Rac‐3K and its enantiomers P/M‐3K were obtained by reduction of corresponding precursors Rac‐3 and P/M‐3 with two equivalent potassium graphite in THF in the presence of (di)benzo‐18‐crown‐6. Neutral dioxoborocyclic helicene diradicals (Rac‐3B and P/M‐3B) were produced by reactions of Rac‐3 or P/M‐3 with chlorobis(perfluorophenyl)borane (B(C6F5)2Cl. Crystal structures of compounds Rac‐3K, Rac‐3B and P/M‐3K were obtained by single crystal X‐ray diffraction. Their open‐shell singlet state ground states were confirmed by electron paramagnetic resonance (EPR) spectroscopy, superconducting quantum interference device (SQUID) measurements and theoretical calculations. Their chiroptical properties were investigated by the electronic circular dichroism (ECD) spectroscopy. This work provides the first examples of enantiopure helicene diradical dianions and boron‐containing helicene diradicals.

I2BODIPY as a new photoswitchable spin label for light-induced pulsed EPR dipolar spectroscopy exploiting magnetophotoselection.

Electron paramagnetic resonance (EPR) pulsed dipolar spectroscopy (PDS) using triplet states of organic molecules is a growing area of research due to the favourable properties that these transient states may afford over stable spin centers, such as switchability, increased signal intensity when the triplet is formed in a non-Boltzmann distribution and the triplet signal is used for detection, and high orientation selection, when the triplet signal is probed by microwave pulses. This arises due to the large spectral width at low fields, a result of the large zero field splitting, and limited bandwidth of microwave pulses used. Here we propose the triplet state of a substituted BODIPY moiety as a spin label in light induced PDS, coupled to a nitroxide, in a model peptide with a rigid structure. Orientation selection allows information on the relative position of the centres of the two labels to be obtained with respect to the nitroxide reference frame. Additionally, magnetophotoselection effects are employed to introduce optical selection and additional constraints for the determination of the relative orientation of the spin labels considering the reference frame of the triplet state.

Pd/UiO‐66(Zr)‐2OH as a High‐Performance Catalyst for Hydrogen‐Enhanced Fenton Oxidation of Trimethoprim

ABSTRACTA novel catalyst material named Pd/UiO‐66(Zr)‐2OH was successfully developed and applied in a hydrogen‐promoted Fenton system for the efficient catalytic oxidation of the widely used antibiotic trimethoprim (TMP). The UiO‐66(Zr)‐2OH, as the carrier of catalyst in this work, was synthesized through a solvothermal method. The Pd0 nanoparticle, as the active center of the catalyst, was loaded onto its surface by the “ship‐in‐a‐bottle” strategy. The results showed that the composite Pd/UiO‐66(Zr)‐2OH demonstrated excellent catalytic performance during the reaction, achieving over 97% of TMP removal efficiency within 180 min under optimal conditions under the condition of only trace of iron without adding H2O2. This may be attributed to the fact that the [H], as a clean and efficient reducing agent, can be utilized to accelerate the regeneration of Fe2+ in the Fenton reaction, as well as in the in‐situ regeneration of H2O2. The key parameters affecting the removal efficiency of TMP, including the initial pH and concentration of Fe2+, the dosage of the synthesized material, the flow rate of H2 and the stirring speed were investigated systematically. The Pd/UiO‐66(Zr)‐2OH exhibited high stability and reusability, maintaining over 82% of its initial degradation efficiency of TMP after six reaction cycles. The mechanistic insight revealed that the system primarily relied on the generation of hydroxyl radical (·OH) and singlet oxygen (1O2) for the degradation of TMP, which was verified through quenching experiments and electron spin resonance (ESR). The degradation pathway of TMP was elucidated by analyzing intermediates and the reduction in total organic carbon (TOC). This research offers novel conceptual insights into the evolution and application of advanced oxidation technologies, efficient degradation of emerging pollutants, and expansion of pathways for hydrogen resource utilization.

High‐Frequency Electron Paramagnetic Resonance and Electron‐Nuclear Double Resonance Spectroscopy Study of the Ga Vacancy in β‐Ga2O3

The Ga vacancy (VGa) defect in β‐Ga2O3, generated by proton irradiation, is studied using high‐frequency electron paramagnetic resonance (EPR) and electron‐nuclear double resonance spectroscopy. The previous X‐band EPR studies of this defect, attributed to VGa2−, are extended to higher frequencies (240 GHz) and lower temperatures (T = 6 K). The spin Hamiltonian parameters of the VGa2− center are determined: electron spin S = 1/2, g‐tensor: gb = 2.0313, gc = 2.0079, and ga = 2.0025; the hyperfine interaction parameters with 2 equivalent Ga neighbors: Ab = 14.0 G, Ac = 14.6 G, and Aa* = 12.8 G for 69Ga; the superhyperfine interaction with distant Ga neighbors ASHF(69Ga) = 11 MHz; and the quadrupole interaction Qb(69Ga) = 0.32 MHz and Qb(71Ga) = 0.22 MHz. These results shall allow to refine the assignment of this center to a split vacancy or an unrelaxed VGa2− defect.

Detection of electron paramagnetic resonance of two electron spins using a single NV center in diamond

An interacting spin system is an excellent testbed for fundamental quantum physics and applications in quantum sensing and quantum simulation. For these investigations, detailed information on the interactions, e.g., the number of spins and their interaction strengths, is often required. In this study, we present the identification and characterization of a single nitrogen vacancy (NV) center coupled to two electron spins. In the experiment, we first identify a well-isolated single NV center and characterize its spin decoherence time. Then, we perform NV-detected electron paramagnetic resonance (EPR) spectroscopy to detect surrounding electron spins. From the analysis of the NV-EPR signal, we precisely determine the number of detected spins and their interaction strengths. Moreover, the spectral analysis indicates that the candidates of the detected spins are diamond surface spins. This study demonstrates a promising approach for the identification and characterization of an interacting spin system for realizing entangled sensing using electron spin as quantum reporters.

New Horizons in Micro/Nanoplastic-Induced Oxidative Stress: Overlooked Free Radical Contributions and Microbial Metabolic Dysregulations in Anaerobic Digestion.

Excessive production of reactive oxygen species (ROS) induced by micro/nanoplastics (MPs/NPs) is highly toxic to microbes. However, the mechanisms underlying ROS generation and metabolic regulation within anaerobic guilds remain poorly understood. In this study, we investigated the effects of environmentally relevant levels of polypropylene (PP)-MPs/NPs on oxidative stress and microbial ecology during anaerobic digestion (AD). Electron paramagnetic resonance spectroscopy revealed that PP-MPs/NPs elevated the concentrations of environmentally persistent free radicals (EPFRs) and derived hydroxyl radicals (•OH). EPFRs were identified as the primary contributors to •OH generation, as evidenced by a high Spearman correlation coefficient (r = 0.884, p < 0.001) and free radical-quenching studies. The formation of •OH enhanced ROS production by 86.2-100.9%, resulting in decreased cellular viability and methane production (by 37.5-50.5%) at 100 mg/g TS PP-MPs/NPs. Genome-centric metagenomic and metatranscriptomic analyses suggested that PP-MPs/NPs induced the reassembly of community structures, re-evolution of functional traits, and remodeling of interspecies interactions. Specifically, PP-MPs/NPs induced a shift in methanogen consortia from hydrogenotrophic Methanofollis sp. to acetoclastic and hydrogenotrophic Methanothrix soehngenii, primarily because of the latter's diverse ingestion patterns, electron bifurcation complexes, and ROS-scavenging abilities. Downregulation of genes associated with antioxidative defense systems (i.e., sodN, katA, and osmC) and ROS-driven redox signal transduction pathways (c-di-AMP and phosphorylation signaling pathways) provided insights into the mechanisms underlying ROS-induced microbial metabolic dysregulation. Our findings enhance the understanding of microbial ecological and metabolic traits under MPs/NPs stressors, facilitating the control of MPs/NPs toxicity and the stabilization of AD processes.

Z-Scheme Enabled 1D/2D Nanocomposite of ZnO Nanorods and Functionalized g-C3 N4 Nanosheets for Sustainable Degradation of Terephthalic Acid.

The urgent need to mitigate water pollution and achieve Sustainable Development Goal 14 (SDG 14)-Life below water, necessitates developing efficient and eco-friendly wastewater treatment technologies. This research addresses this challenge by photocatalytic degradation of terephthalic acid, a precursor for PET bottles using environment-friendly and biocompatible photocatalysts. The 1D/2D nanocomposite comprising zinc oxide (ZnO) nanorods and functionalized graphitic carbon nitride (Zn-TG) nanosheets were synthesized and thoroughly characterized. The nanocomposite effectively mitigated the individual drawbacks of Zn-TG agglomeration and the wide band gap of ZnO as confirmed through zeta potential and Tauc's plot studies, respectively. The synthesized nanocomposite achieved ~100 % degradation within 60 minutes, exhibiting superior kinetics (~2.5 times) compared to pristine samples. The enhanced degradation efficiency was elucidated by efficient charge carrier transfer (~5 times faster) and separation (~2 times improved) as confirmed through electrochemical impedance spectroscopy and time-resolved photoluminescence studies. The proposed Z-scheme pathway provides mechanistic insights. This proposed mechanism is supported by extensive electron paramagnetic resonance (EPR) and scavenger studies. The liquid chromatography-mass spectrometry (LC-MS) analysis confirms the formation of less toxic byproducts for ensuring that the wastewater treatment process is efficient and environmentally friendly. This research helps in developing a highly effective and sustainable wastewater treatment technology.

A highly-efficient peroxymonosulfate activator using a sewage sludge derived biochar supported cobalt oxide: Mechanism and characteristics

The application of biochar derived from sewage sludge (BS) in Fenton-like reactions for contaminant removal has attracted considerable attention. Herein, a BS-supported Co3O4 (BS-Co3O4) catalyst was synthesized using a simple two-step hydrothermal-calcination process to achieve highly efficient activation of peroxymonosulfate (PMS). The introduction of biochar effectively inhibited the aggregation of Co3O4 and reduced cobalt leaching. Compared to Co3O4, the mesoporous BS-Co3O4 exhibited an 8-fold increase in specific surface area (SSA) to 111.92 m2∙g−1, and a 46 %-66.4 % reduction in crystal plane size. The interaction between biochar and cobalt oxide resulted in several notable enhancements in the BS-Co3O4 composite. Specifically, there was an increase in sp2 carbon content, a 42.69 % rise in capacitance, and a 79.99 % reduction in charge transfer resistance. These improvements contributed to enhanced PMS activation performance. The BS-Co3O4 also contained a higher content of Co(II), sp2 carbon, and oxygen vacancies (OV). Co(II) played a crucial role in the redox reaction, accelerating the formation of SO4•− and 1O2 during the PMS activation process. Additionally, OV acted as electron capture centers, further promoting the generation of 1O2. Evidence from reactive species investigations and electron paramagnetic resonance (EPR) tests indicated that SO4•− and 1O2 were the main reactive radicals for eliminating tetracycline (TC). Based on the identification of TC intermediates, two potential degradation pathways were proposed, and a reduction in intermediate toxicity was observed. Experiments involving interference and repetition demonstrated that the BS-Co3O4 catalyst was stable and reusable. This work provides a solution with low metal leaching, high recycling performance, and safety for antibiotic wastewater treatment.

In-situ generation of highly-reactive FeIV=O and its contribution during CH4 conversion to CH3OH

Photocatalytic CH4 conversion to CH3OH under mild conditions is undoubtedly an efficient strategy to realize CH4 upgrading. In this work, in-situ formed highly reactive FeIV=O complex with a bound Cl axial ligand was detected at ambient temperature and its contribution to CH4 photoxidation to CH3OH was deeply investigated. Under optimized experimental condition, a high CH3OH yield of 3026.1 mmol molFe−1 (6.76 mmol gcat−1 h−1) with selectivity of 73.6 % was obtained during 8 h. Isotope labeling mass spectroscopy experiments manifested that O2 was the only source of oxygen in products. The formation of Cl-(H2O)4FeIVO complex was confirmed using low-temperature electron spin resonance spectroscopy and cryogenic Raman spectroscopy (ν(FeO) = 828 cm−1). Through density functional theory (DFT) calculation, we showed that the Cl axial ligand acts as an “electron reservoir” during CH4 conversion, i.e., electron acceptor during the process of CH4 oxidation to CH3OH, while electron donor in CH3OH desorption. This not only lowered C-H cleavage energy, but also facilitated CH3OH desoption and inhibited overoxidation. As far as we know, Cl-(H2O)4FeIVO is the first detected FeIVO complex generated directly from O2 and Fe3+ at ambient temperature.

Research on the Influence of Fault Structure on Physical and Chemical Structure of Coking Coal During Spontaneous Combustion

ABSTRACT The spontaneous combustion tendency and oxidation combustion properties of coking coal in fault fracture zone and primary coking coal are different. Accordingly, this study uses Thermogravimetric analysis, in-situ Fourier transform infrared spectroscopy, Scanning electron microscope, low-temperature N2 adsorption and Electron spin resonance techniques were used to study the difference of macroscopic and microscopic structural characteristics between coking coal and primary coking coal in fault fracture zone. The results show that: The oxygen absorption capacity of coking coal in fault fracture zone is enhanced and the thermogravimetric characteristic temperature is advanced, and the ignition point temperature is advanced by 5.36°C; the maximum weight loss temperature of coking coal in fault fracture zone is 3.32°C lower than that of primary coking coal. The apparent activation energy of coking coal in oxidation stage and pyrolytic combustion stage decreased by 4.88 and 5.03 kJ/mol, respectively. Compared with primary coking coal, the pore structure of coking coal in fault fracture zone is more complex, which increases the roughness of coal surface and is conducive to oxygen adsorption. In addition, fault tectonics promotes the separation and cracking of oxygen-containing functional groups into small molecules, and the polycondensation of aliphatic hydrocarbon structure promotes the formation of active free radicals, thus promoting spontaneous combustion. This study provides an important reference and theoretical support for further understanding of the structural evolution and oxidation kinetics of highly metamorphic coking coal induced by fault tectonics, which is helpful for fire prevention and control in fault structure-developed mining areas and safe production of coal industry.