Electron Spin Resonance Measurements Research Articles

Correlating color with free radical concentration in irradiated poly(ethylene terephthalate)

When polymers are irradiated, free radicals form, often accompanied by yellowing in the material. This color gradually fades after active irradiation due to the decay of free radicals. This study analyzed the kinetics of post-irradiated PET discoloration under different temperatures using a UV–visible spectrophotometer. Meanwhile, the free radical decay was also monitored using the electron paramagnetic resonance (EPR) measurements, and then both experiments were compared. The results illustrate the potential of readily available spectrophotometry as an alternative method to track free radical evolution in irradiated polymers because free radical decay leads to the disappearance of annealable color centers over time. Furthermore, PET structure modification by irradiation was studied using extensional rheological analysis. The observed strain hardening suggests the evolution of long-chain branching structures in post-irradiated PET, especially at 50 kGy irradiation absorbed dose.

An efficient, green, and magnetic recycling wastewater treatment technique enabled by ZnO/NiFe2O4/BiOBr 3D nanofibers photo-fenton process

A novel magnetic recycling ZnO/NiFe2O4/BiOBr 3D nanofibers photo-Fenton system was successfully prepared by parallel electrospinning combining with solvothermal method. ZnO/NiFe2O4 composite nanofibers was prepared via parallel electrospinning, then ZnO/NiFe2O4/BiOBr 3D nanofibers was obtained by solvothermal growth of BiOBr on electrospun ZnO/NiFe2O4 composite nanofibers. The composition, morphologies, structures and photocatalytic properties of ZnO/NiFe2O4/BiOBr 3D nanofibers were systematically tested and analyzed, and some meaningful results were obtained. The prepared ZnO/NiFe2O4/BiOBr 3D nanofibers, combined with H2O2, form a photo-Fenton system that exhibits excellent photocatalytic performance. When 0.05 mL of H2O2 is added to the photo-Fenton system, the degradation rate of organic dye Rhodamine B (RhB) reaches 99.61 % under light exposure for 10 min. Capture experiments and Electron Spin Resonance (ESR) measurements have confirmed that holes (h+) and hydroxyl radicals (·OH) are the primary active species that play a dominant role in the photocatalytic degradation of Rhodamine B (RhB). Furthermore, the ZnO/NiFe2O4/BiOBr 3D nanofibers have demonstrated exceptional photocatalytic degradation efficiency towards RhB, maintaining a degradation rate of over 95 % even after undergoing three recycling experiments. Significantly, this photo-Fenton system also has good magnetic properties, which can be separated from the treatment system under the applied magnetic field, avoiding secondary pollution of the treatment system, improving reuse rate and saving costs. This study provides valuable insights for the purposeful utilization of the photocatalytic materils.

Spirocyclic pyrrolidinyl nitroxides with exo-methylene substituents.

Nitroxides are stable organic radicals with exceptionally long lifetimes, which render them uniquely suitable as observable probes or polarising agents for spectroscopic investigation of biomolecular structure and dynamics. Radical-based probes for biological applications are ideally characterized by both robustness towards reductive degradation and beneficial electron spin relaxation parameters. These properties are largely influenced by the molecular structure of the nitroxide scaffold, and also by the conformations it prefers to adopt. In this study we present the synthesis of the first nitroxides based on a spirocyclic pyrrolidine scaffold with an exocyclic methylene substituent. The conformations adopted by these nitroxides were evaluated by X-ray crystallography, both with single nitroxide crystals and by inclusion of nitroxides in a microporous crystalline sponge. The kinetic and thermodynamic stability of the new nitroxides towards reduction was investigated by electron paramagnetic resonance (EPR) spectroscopy and cyclic voltammetry (CV). In combination with EPR measurements of electron spin relaxation properties, these results suggest that this new family of nitroxides can provide access to multifunctionalized probes and polarising agents suitable for use in biological environments at elevated temperatures.

The inhibitory potential of 4,7-dihydroxycoumarin derivatives on ROS-producing enzymes and direct HOO•/o2 • – radical scavenging activity – a comprehensive kinetic DFT study

This study examined the antiradical activity of three synthesized coumarin derivatives: (E)-3-(1-((2-hydroxyphenyl)amino)ethylidene)-2,4-dioxochroman-7-yl acetate (A1-OH), (E)-3-(1-((3-hydroxyphenyl)amino)ethylidene)-2,4-dioxochroman-7-yl acetate (A2-OH), and (E)-3-(1-((4-hydroxyphenyl)amino)ethylidene)-2,4-dioxochroman-7-yl acetate (A3-OH) against HOO•/O2•− radical species. The investigation included electron spin resonance (ESR) measurements and a DFT kinetic study. Thermodynamic and kinetic parameters of antiradical mechanisms—Formal Hydrogen Atom Transfer (f-HAT), Radical Adduct Formation (RAF), Sequential Proton Loss followed by Electron Transfer (SPLET), and Single-Electron Transfer followed by Proton Transfer (SET-PT)—were evaluated using the Quantum Mechanics-based test for Overall Free Radical Scavenging Activity (QM–ORSA) under physiological conditions. ESR results indicated antiradical activity decreased in the sequence A1–OH (58.7%) > A2–OH (57.5%) > A3–OH (53.1%). Kinetic analysis revealed the f-HAT mechanism dominated HOO• inactivation. A newly formulated Sequential Proton Loss followed by Radical Adduct Formation (SPL-RAF) mechanism described interactions with O2 •−. The activity toward O2 •− was A2–OH (1.26 × 106 M−1s−1) > A3–OH (7.71 × 105 M−1s−1) > A1–OH (4.22 × 105 M−1s−1). Molecular docking and dynamics studies tested inhibitory capability against enzymes producing reactive species: Lipoxygenase (LOX), Myeloperoxidase (MPO), NAD(P)H oxidase (NOX), and Xanthine Oxidase (XOD). Affinity to enzymes decreased in the order: XOD > LOX > NOX > MPO.

Finite Temperature Magnetism in the Triangular Lattice Antiferromagnet KErTe2

Abstract After the discovery of the ARECh2 (A = alkali or monovalent ions, RE = rare-earth, Ch = chalcogen) triangular lattice quantum spin liquid (QSL) family, a series of its oxide, sulfide, and selenide counterparts has been consistently reported and extensively investigated. While KErTe2 represents the initial synthesized telluride member, preserving its triangular spin lattice, it was anticipated that the substantial tellurium ions could impart more pronounced magnetic attributes and electronic structures to this material class. This study delves into the magnetism of KErTe2 at finite temperatures through magnetization and electron spin resonance (ESR) measurements. Based on the angular momentum J ^ after spin-orbit coupling (SOC) and symmetry analysis, we obtain the magnetic effective Hamiltonian to describe the magnetism of Er3+ in R 3 ¯ m space group. Applying the mean-field approximation to the Hamiltonian, we can simulate the magnetization and magnetic heat capacity of KErTe2 in paramagnetic state and determine the crystalline electric field (CEF) parameters and partial exchange interactions. The relatively narrow energy gaps between the CEF ground state and excited states exert a significant influence on the magnetism. For example, small CEF excitations can result in a significant broadening of the ESR linewidth at 2 K. For the fitted exchange interactions, although the values are small, given a large angular momentum J = 15/2 after SOC, they still have a noticeable effect at finite temperatures. Notably, the heat capacity data under different magnetic fields along the c axis direction also roughly match our calculated results, further validating the reliability of our analytical approach. These derived parameters serve as crucial tools for future investigations into the ground state magnetism of KErTe2. The findings presented herein lay a foundation for exploration of the intricate magnetism within the triangular-lattice delafossite family.

WS2@FeBC assisted Fe(III)-activated percarbonate for roxarsone and tetracycline simultaneous removal: Interfacial fenton-like process enhanced by oxygen vacancies and tungsten redox

Sodium percarbonate (SPC) has garnered significant interest for its application in water decontamination via advanced oxidation processes (AOPs), however, SPC Fenton-like processes are always hindered by slow iron cyclic conversion and the production of ferric sludge, which limit their efficiency and practicality. Herein, a novel strategy was proposed to greatly improves the Fe(II)/Fe(III) cycling by utilizing oxygen vacancies (OV) in conjunction with W(IV)/W(VI) redox couples synergistically. In the optimized WS2@FeBC/Fe3+/SPC system, over 97 % removal efficiencies were achieved for both tetracycline (TC) and roxarsone (ROX) within just 10 min. Furthermore, the WS2@FeBC/Fe3+/SPC system exhibits robust performance across a broad pH range (3 to 11) and maintains high removal efficiencies above 90 % even after seven reuse cycles. Quenching experiments combined with electron paramagnetic resonance (EPR) and open-circuit potential measurements indicate that surface-adsorbed hydroxyl radicals (•OHads) and direct electron transfer are crucial for TC/ROX degradation. Density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) analyses reveal that oxygen vacancies enhance H2O2 activation to produce •OHads, while sulfur vacancies accelerate the W(IV)/W(VI) redox process by mediating localized electron density around tungsten, thereby promoting the Fe(III)/Fe(II) cycling. This study provides a novel perspective on the surface interfacial reactions between reactive oxygen species (ROS) and organic pollutants, offering significant advancements in understanding and improving AOPs for water treatment.

Rapid Oxidative Dissolution of Zerovalent Iron Induced by Sulfite for Efficient Removal of Arsenate and Arsenite: Selective Formation of Scorodite.

In this study, we proposed a moderate oxidation strategy for accelerating the oxidative dissolution of zerovalent iron (ZVI) using sulfite (S(IV)), thereby improving the removal of As(V) and As(III). Results revealed that, in the presence of 2.0 mM S(IV), both As(V) and As(III) were selectively converted into scorodite at pH0 3.0-7.0, while As(III) oxidation and As(V) immobilization were impressed over pH0 8.0-10.0. Batch experiments, radical quenching experiments, and electron spin resonance (ESR) measurements demonstrated that ZVI initially boosted S(IV) activation to generate SO4•-, •OH, and protons, and in turn, ZVI was further oxidized more intensely by these radicals than by oxygen. Concurrently, substantial protons derived from S(IV) oxidation neutralized hydroxyls produced by ZVI oxidation, maintaining an acidic environment conducive to the generation of scorodite rather than iron (hydr)oxides. Characterizations of X-ray diffraction (XRD), Raman, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) confirmed that scorodite was formed in situ and then exfoliated from the surface of ZVI, and approximately 75% of ZVI could still be recovered, which contributed to efficient As removal in successive runs and real As-polluted wastewater. The application of S(IV) achieved a balance among ZVI reactivity improvement, As(V)/As(III) removal, and raw material consumption, making it a promising approach for addressing arsenic contamination in wastewater treatment.

Advanced activation of peroxymonosulfate by NiFe-LDH/CeO2 heterostructure photocatalysts toward medical wastewater remediation

The great harm of antibiotic residues in medical wastewater to the ecological environment and human health has become the focus of social attention. Herein, we designed a new peroxymonosulfate (PMS) activation system by in-situ anchoring NiFe-LDH nanosheets into CeO2 (NFC) as a heterogeneous photocatalyst to degrade pollutants. The NFC/PMS/Vis system showed excellent and rapid degradation effect on tetracycline (TC) under the synergistic effect of photocatalysis and PMS activation, and the removal rate of TC was about 98.8 % within 40 min. The chemical compositions, microstructures, and optical properties of synthesized photocatalysts were studied by a series of characterization methods such as XRD, XPS, SEM, TEM and UV-DRS. The effects of various reaction systems and operating parameters such as initial concentration, catalyst dosage, and PMS concentration on the degradation efficiency of TC over optimized NFC-4 composite were investigated. The active species in the reaction system and the dominant SO4− were confirmed by quenching tests and electron paramagnetic resonance (EPR) measurements, and a plausible photocatalytic mechanism for PMS activation and pollutant remediation was further proposed.

Lignin Structural Characterization and Its Antioxidant Potential: A Comparative Evaluation by EPR, UV-Vis Spectroscopy, and DPPH Assays.

The natural aromatic polymer lignin and its lignin-like oligomeric fragments have attracted attention for their antioxidant capacity and free radical scavenging activities. In this study, a 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was employed to assess the antioxidant capacity of fractionated and partially depolymerized organosolv lignin by electron paramagnetic resonance (EPR) and UV-Vis spectroscopy. The results show significant antioxidant activity for both the lignin and oligomeric fragments, with the EPR measurements demonstrating their efficiency in quenching the free radicals. The EPR data were analyzed to derive the kinetic rate constants. The radical scavenging activity (RSA) of lignins was then determined by UV-Vis spectroscopy and the results were compared with the EPR method. This two-method approach improves the reliability and understanding of the antioxidant potential of lignin and its derivatives and provides valuable insights for their potential applications in various industries, including pharmaceuticals, food preservation, and cosmetics.

Energy transfer of Eu3+/Dy3+ ions co-doped BaCO3 elaborated by auto-combustion process

Samples of undoped and (Eu3+, Dy3+) ions co-doped BaCO3, were synthesized by autocombustion method. The samples nanostructures were characterized by various techniques such as X-ray diffraction, scanning electron microscopy (SEM), Photoluminescence (PL) spectroscopy and electron paramagnetic resonance (EPR). Based on XRD analysis, the undoped and (Eu3+, Dy3+) co-doped BaCO3 kept its orthorhombic structure. The calculated crystallite sizes for undoped and (Eu3+, Dy3+) co-doped BaCO3 samples are 70 and 49 nm, respectively. The FTIR spectra allowed the determination of the vibration modes of BaCO3. Morphological analysis showed that the synthesized powders consist of spherical and agglomerated particles. The EPR measurements exhibited a narrow response for BaCO3, along with an increased intensity in the case of the Eu3+ doped and (Eu3+, Dy3+) co-doped samples, indicating the incorporation of Eu3+ and Dy3+ ions into the matrix. The effect of Dy3+ (0.5 %) on the luminescence properties of BaCO3:Eu3+were studied. The results indicated that the lifetimes of the state 5D0 of Eu3+ increase from 1.15 to 1.31 ms in the presence of Dy3+, proving an energy transfer from Dy3+ to Eu3+ ions. This transfer was verified also by photoluminescence spectra, quantum efficiency of the 5D0 → 7F2 emission (80 %) and the emission cross section (39×10−22 cm2). The CCT (4239 K) and CRI (87) were calculated. Therefore, Eu3+, Dy3+ co-doped BaCO3 material could be used in the fields of w-LED applications.

Production of Lactic Acid via Catalytic Transfer Dehydrogenation of Glycerol Catalyzed by Base Metal Salt Ferrous Chloride and Its NNN Pincer-Iron Complexes.

NNN-Bis(imino) pyridine-based pincer-Fe(II) complexes with an expected trigonal bipyramidal (TBP) geometry equilibrated to a rearranged ion pair of an octahedral dicationic Fe complex containing two bis(imino)pyridine ligands that are neutralized by a tetrahedral dianionic-[FeCl4]2-. Single-crystal X-ray diffraction (SCXRD), high-resolution mass spectrometry (HRMS), and UV-visible (UV-vis) studies suggested that the equilibrium was dictated by the sterics of the R group on the imine N, with the less-crowded groups tilting the equilibrium to the ion pair and the bulky ones favoring the TBP geometry. Electron paramagnetic resonance (EPR) and Evan's magnetic moment measurements indicated that the complexes were paramagnetic with Fe(II) in a high-spin state. In solution, over a period of 7 days, these Fe(II) complexes oxidized to a mixture of low-spin and high-spin Fe(III) species. These pincer-Fe(II) were found to be highly active toward the transformation of biodiesel waste glycerol to value-added lactic acid (LA). Particularly, (Ph2NNN)FeCl2 (0.1 mol %) gave 91% LA with a 99% selectivity at 140 °C using 1.2 equiv of NaOH. With 0.0001 mol % (Ph2NNN)FeCl2, very high turnovers (74% LA, 98% selectivity, 740 000 turnover number (TON) at 4405 turnovers per hour (TOs/h)) were obtained after 7 days. EPR indicated Fe(III) species to be the active catalyst, a few of which were detected by HRMS. Experiments with Hg are suggestive of the mostly homogeneous molecular nature of the catalyst with a minor contribution from heterogeneous Fe nanoparticles.

Magnetic properties of polycrystalline bulk crystals of MnGeP2

Room temperature ferromagnetism observed in polycrystalline MnGeP2 bulk samples was investigated by different experimental techniques. The magnetization measurements show a high temperature ferromagnetic phase with a critical temperature TC = 294.0 K and a low temperature magnetic phase transition at TN = 40.5 K. As these parameters (TC,TN) correspond to those of MnP, a ferromagnetic half-metal, whose composition of the samples was further characterized by x-ray diffraction and Rutherford backscattering measurements. They confirmed the presence of orthorhombic MnP precipitates. Electron paramagnetic resonance (EPR) and ferromagnetic resonance (FMR) measurements in the temperature range of T = 4 K to T = 380 K confirm the attribution of the magnetic phase to MnP and show no additional EPR or FMR signal associated with MnGeP2. We conclude that the magnetic properties of the polycrystalline MnGeP2 bulk samples grown by the horizontal gradient freeze technique are dominated by MnP inclusions and that phase pure chalcopyrite MnGeP2 is not ferromagnetic in contrary to previous reports.

Degradation of citrinin by different types of light and hydrogen peroxide.

Citrinin (CIT), a mycotoxin produced by Monascus, Penicillium, and other fungies, can contaminate red yeast rice and other foods, thus constraining their application and development. Exploring efficient degradation methods of citrinin is becoming as one of the hot research topics. In this study, the degradation of citrinin, irradiated by visible (Vis) light, ultraviolet (UV) light, and simulated sunlight alone, as well as in combination with hydrogen peroxide (light/H2O2), was investigated. The research demonstrates UV, Vis, and simulated sunlight all have a degree of degradation on citrinin, and the degradation efficiency correlates with light source and light intensity. Interestingly, when combined with 100W Vis and 0.01M H2O2, the citrinin degradation rate increases to 32%, compared to 1% and 5% achieved by Vis and H2O2 alone. Hydroxyl radicals, arising from the uniform cracking of H2O2 under Vis, were experimentally validated by electron spin resonance measurement and could accelerate the dissociation of citrinin by nucleophilic attacking. Employing the density functional theory, we deduced nucleophilic •OH mainly attack onto C8 and C5 site by comparing the electrophilic Parr functions (Pk+) value of main C atom of citrinin. This research presents a rapid and efficient degradation of citrinin by combining visible light with H2O2. PRACTICAL APPLICATION: This research presents a rapid and efficient method for the degradation of citrnin in red yeast rice and other citrnin containing products by combining visible light with H2O2.

Double template synthesis of N/S co-doped shrimp shell derived biochar for efficient sulfadiazine degradation: The role of non-radical pathway

In this work, waste shrimp shells were used to synthesize N/S-co-doped biochar nanomaterials (BC-NS) by simple hard template and soft template. Through the cooperative effect of adsorption and degradation, the BC-NS/PMS system could remove 100 % of SDZ within 30 min. The combination of soft and hard templates produces hierarchical porous structure and provides more reactive sites. The radical quenching tests and electron paramagnetic resonance measurements (EPR) illustrated that the non-radical 1O2 was the dominant reactive oxidative species (ROS) in the BC-NS/PMS system. By density functional theory (DFT) computation, it demonstrated that graphitic N and pyridinic N were the main reactive sites of BC-NS. Finally, intermediate products of SDZ have been identified and four possible pathways for the degradation of SDZ were proposed. Consequently, a novel synthesis strategy of metal-free biochar materials was proposed in this study, which broadened a new prospect for the application of metal-free biochar materials in SR-AOPs.

The Dynamic Plasticity of P. aeruginosa CueR Copper Transcription Factor upon Cofactor and DNA Binding.

Bacteria use specialized proteins, like transcription factors, to rapidly control metal ion balance. CueR is a Gram-negative bacterial copper regulator. The structure of E. coli CueR complexed with Cu(I) and DNA was published, since then many studies have shed light on its function. However, P. aeruginosa CueR, which shows high sequence similarity to E. coli CueR, has been less studied. Here, we applied room-temperature electron paramagnetic resonance (EPR) measurements to explore changes in dynamics of P. aeruginosa CueR in dependency of copper concentrations and interaction with two different DNA promoter regions. We showed that P. aeruginosa CueR is less dynamic than the E. coli CueR protein and exhibits much higher sensitivity to DNA binding as compared to its E. coli CueR homolog. Moreover, a difference in dynamical behavior was observed when P. aeruginosa CueR binds to the copZ2 DNA promoter sequence compared to the mexPQ-opmE promoter sequence. Such dynamical differences may affect the expression levels of CopZ2 and MexPQ-OpmE proteins in P. aeruginosa. Overall, such comparative measurements of protein-DNA complexes derived from different bacterial systems reveal insights about how structural and dynamical differences between two highly homologous proteins lead to quite different DNA sequence-recognition and mechanistic properties.

Ozone nanobubble technology as a novel AOPs for pollutants degradation under high salinity conditions

Conventional water treatment systems frequently exhibit diminished efficiency at high salinity - a significant issue especially for real industrial effluents - mostly due to the creation of intricate structures between pollutants and salts. One of the primary obstacles associated with high salinity conditions is the generation of by-products that pose additional hurdles for treatment. In this work, we have investigated the novel advanced oxidation process a so-called ozone nanobubble technology for degradation of the pollutants at high salinity conditions. The mass transfer is often the rate-limiting step in gas-liquid process and the poor rate of mass transfer diminishes the overall efficacy. One of the primary disadvantages associated with ozone is its restricted solubility and instability when dissolved in an aqueous solution. These characteristics impose limitations on its potential applications and need the use of specialized systems to facilitate gas-liquid interaction. In this work, we have also suggested enhancing the ozonation process through the utilization of ozone nanobubbles. The findings of our experiment and subsequent analysis indicate that the presence of nanobubbles enhances the process of ozonation through three key mechanisms: (i) an increased mass transfer coefficient, (ii) a higher rate of reactive oxygen species (ROS) generation attributed to the charged interface, and (iii) the nanobubble interface serving as an active surface for chemical reactions. The predicted mass transfer coefficients were found to range from 3 to 3.5 min−1, a value that is notably greater than that seen for microbubbles. The study showcased the degradation of methylene blue dye through the utilization of ozone nanobubbles, which exhibited a much higher rate of dye degradation compared to ozone microbubbles. The confirmation of the radical degradation mechanism was achieved by the utilization of electron spin resonance (ESR) measurements. The developed process has high potential for application in industrial scale textile wastewater treatment.

Efficient degradation of halogenated disinfection by products in a three-dimensional electrode reactor with MnO2/NiMn-LDH/C as particle electrodes: Performance prediction and mechanism exploration

In this work, an in situ novel MnO2/NiMn-LDH/C composite material was designed and used as a particle electrode in a three-dimensional electrochemical continuous flow system, which degraded dichloroacetamide (DCAcAm) because a suitable nickel-manganese metal ratio leads to the construction of MnO2 and NiMn-LDH, and the addition of carbon contributes to the formation of a hierarchical structure. The effects of different conditions were explored by single factor experiments and response surface design experiments. A high removal rate of 89 % was obtained under optimal conditions (current density of 12 mA/cm2, flow rate of 0.5 mL/min, electrolyte concentration of 0.175 mol/L, and a pollutant concentration of 10.5 g/L). According to density functional theory (DFT) calculations, electron paramagnetic resonance (EPR) measurements and free radical quenching experiments, the corresponding electrocatalytic mechanism and reaction pathways were clarified. The application of response surfaces was utilized to predict degradation performance. The results of the recycling experiments show the good stability of this electrode. Finally, the actual chlorin wastewater degradation experiment results showed that the COD and TOC of this wastewater decreased by 76.03 % and 72.41 %, respectively, after 90 min of electrocatalytic degradation. This study offers a novel theoretical framework and technical support for the control of HAcAms.

An efficient EPR spin-labeling method enables insights into conformational changes in DNA

Electron paramagnetic resonance (EPR) is a powerful tool for elucidating both static and dynamic conformational alterations in macromolecules. However, to effectively utilize EPR for such investigations, the presence of paramagnetic centers, known as spin labels, is required. The process of spin labeling, particularly for nucleotides, typically demands intricate organic synthesis techniques. In this study, we introduce a unique addition-elimination reaction method with a simple spin-labeling process, facilitating the monitoring of structural changes within nucleotide sequences. Our investigation focuses on three distinct labeling positions with a DNA sequence, allowing the measurement of distance between two spin labels. The experimental mean distances obtained agreed with the calculated distances, underscoring the efficacy of this straightforward spin-labeling approach in studying complex biological processes such as transcription mechanism using EPR measurements.

Limiting factors for charge generation in low-offset fullerene-based organic solar cells

Free charge generation after photoexcitation of donor or acceptor molecules in organic solar cells generally proceeds via (1) formation of charge transfer states and (2) their dissociation into charge separated states. Research often either focuses on the first component or the combined effect of both processes. Here, we provide evidence that charge transfer state dissociation rather than formation presents a major bottleneck for free charge generation in fullerene-based blends with low energetic offsets between singlet and charge transfer states. We investigate devices based on dilute donor content blends of (fluorinated) ZnPc:C60 and perform density functional theory calculations, device characterization, transient absorption spectroscopy and time-resolved electron paramagnetic resonance measurements. We draw a comprehensive picture of how energies and transitions between singlet, charge transfer, and charge separated states change upon ZnPc fluorination. We find that a significant reduction in photocurrent can be attributed to increasingly inefficient charge transfer state dissociation. With this, our work highlights potential reasons why low offset fullerene systems do not show the high performance of non-fullerene acceptors.

Construction of Co3O4/Bi5O7I heterojunction derived from ZIF-67/BiOI with enhanced photodegradation ability

Recently, the degradation of expired and unused antibiotics has been a great concern for human health, and it has become a serious environmental hazard. Photocatalysis technology has treated the most promising ways to degrade antibiotics in the environment with high efficiency and low cost. A series of Co3O4/Bi5O7I composites were successfully synthesized via the calcination method derived from Zeolitic imidazolate frameworks-67 and Bismuth oxyiodide, and chatacerized by spectroscopic and also X-ray diffraction (XRD) processes. Co3O4/Bi5O7I composites exhibited enhanced photocatalytic performance for tetracycline degradation, which is about 6 times higher than that of the pristine Co3O4. The Co3O4/Bi5O7I can remove 86.67% tetracycline in 90 min and shows enhanced photocatalytic activities, which are about 6 times higher than those of the pristine Co3O4. The possible mechanisms of photocatalytic degradation were analyzed by trapping experiments, electron paramagnetic resonance, photocurrent, and electrochemical impedance measurements. The direct Z-scheme structure of Co3O4/Bi5O7I composites facilitated the charge separation and transportation of the photogenerated electrons and holes.