Electron Spin Research Articles

Evidence for capture of spin-labeled ibuprofen drug molecules by lipid rafts in model membranes

Lipid rafts are lipid-cholesterol nanostructures thought to exist in cell membranes, which are characterized by higher ordering compared to their surroundings. Ibuprofen and other non-steroidal anti-inflammatory drugs (NSAIDs) have a high affinity for phospholipid membranes and can alter their structure and biological properties. Here we use electron paramagnetic resonance (EPR) in its pulsed electron spin echo (ESE) version to study spin-labeled ibuprofen (ibuprofen-SL) in a raft-mimicking bilayer, which consists of an equimolar mixture of the phospholipids dioleoyl-glycero-phosphocholine (DOPC) and dipalmitoyl-glycero-phosphocholine (DPPC), with cholesterol added in various proportions. ESE decays are sensitive to the presence of low-temperature small-angle orientational motions of molecules − stochastic molecular librations. The data obtained show that in the presence of lipid rafts the temperature dependence of the spin relaxation rate induced by this motion reaches a plateau. This behavior is characteristic of non-cooperative motion of a molecule bound to some structure denser than the rest of the medium. Based on this analogy, the data obtained were interpreted as evidence that ibuprofen-SL molecules are adsorbed on the raft boundaries.

Kinetics of optical phonons and DP depolarization of spins in drift transport: Hot carrier spin effect in semiconductors

<p>Spin-<strong>c</strong>onserving transport of carriers is an essential requirement for the practical semiconductor-based spintronic devices. Kinetics of optical phonons and Dyakonov-Perel (DP) depolarization of spins in drift transport in semiconductor gallium arsenide (GaAs) is theoretically investigated<strong>. </strong>We consider electrons in <em>n</em>-type bulk GaAs subjected to a strong electric field, where the electron distribution is assumed to be drifted Maxwellian. The momentum drift of this distribution results in the enhanced drift velocity, and electrons with the corresponding energy emit optical hot phonons in the drifting process. The hot phonons are incorporated via the longitudinal polar optical phonon (POP) mechanism in the momentum relaxation. It is found that a finite phonon lifetime can reduce the momentum relaxation rate, which results in a delay in the runaway to higher fields, where the effect increases with the electron density. The electron spin is found to relax with the DP relaxation frequencies, and the DP spin lifetimes are found to decrease with increasing the drift field. However, a high field completely depolarizes the electron spin due to an increase of the DP spin precession frequency of the hot electrons in the POP scattering process. It is also found that the DP spin precession frequency decreases with decreasing electron temperature or increasing electron density in the moderate range. However, the findings resulting from this investigation demonstrate the hot carrier effect in the spin transport in semiconductors. The results are discussed in comparison with those obtained in earlier experimental and theoretical studies with different approaches.</p>

Stabilize the oxygen vacancies in ZnO via altering local electronic structure by Co and Ni doping: A novel strategy for achieving durable visible light driven photo-Fenton degradation of chloramphenicol

The build-up of antibiotics, harmful pollutants, and pharmaceutical products has led to the significant contamination of environmental water bodies. Hence, the advancement of oxidation methods such as light-induced photo-Fenton degradation has proven crucial for efficiently desolating these harmful pollutants. Herein, we report a novel photo Fenton catalyst, Co and Ni co-doped ZnO (Zn1-x-yCoxNiyO) nanorods (NRs) for enhanced photocatalytic degradation of chloramphenicol (CAP) under visible light irradiation. The NRs were synthesized via the ultrasonication-assisted solvothermal method. Among the different Co and Ni doping concentrations, Zn0.96Co0.03Ni0.01O NRs showed superior photodegradation efficiency of 94.2%. Here, •OH radicals were identified as predominant reactive oxygen species in photocatalytic degradation by electron spin resonance (ESR) analysis and scavenging assay. The effect of various environmental parameters such as nanoparticle dosage, CAP concentration, pH, and ions were investigated to understand the impact of these parameters on the degradation of CAP. Further, Zn0.96Co0.03Ni0.01O NRs were stable for six consecutive photodegradation cycles, which showed their excellent efficiency and reusability for prolonged usage. Photostability was further confirmed by XPS and XRD analysis of the used photocatalyst. Also, the photodegradation pathway of CAP was predicted by identifying the intermediate compounds via GC-MS analysis. This approach holds promise for the efficient visible-light-driven degradation of pharmaceutical pollutants including CAP and contributes to the advancement of sustainable water treatment technologies.

Rational design of H2 production sites for achieving photoconversion of CO2 with H2O into widely adjustable syngas and highly effective H2 evolution

The photoconversion of CO2 with H2O into widely tunable syngas (CO and H2) or pure H2 production is regarded as a promising strategy to mitigate escalating energy shortages and climate change. Herein, anchoring the H2 production sites onto the surface of CdIn2S4 (CIS) with a nanoscale hollow sphere allows for the photoconversion of CO2 into syngas and water splitting to H2. The CO/H2 ratio can be realized in a remarkably wide range from 1:0.38–1:3.76. The optimized CIS/Co-PBA/NaY-5 hybrid exhibits superior photocatalytic syngas evolution up to 1458.48 μmol·g−1·h−1 (H2/CO, 1152.29/306.19 μmol·g−1·h−1), and the H2 evolution rate increases by 431.70 % compared with CIS. The CIS/Co-PBA/NaY-5 hybrid exhibited not only superior H2 evolution but also recyclability. The experimental, energy-dispersive X-ray spectroscopy, and electron spin resonance results indicate that the Co sites serve as H2 production sites and promote the H2 evolution reaction. In addition, the construction of a p-n heterojunction with a special micromorphology is beneficial for the separation/transfer of carriers.

Plasmonic S-type Bi/TiO2@C Heterojunction Composites for Efficient Visible-Light Photocatalytic Removal of Multi-Antibiotics and Dyes

In this work, two series of plasmonic S-type heterojunction photocatalysts containing Bi, TiO2, and biochar (Bi/TiO2@C) have been developed through a biomass-assisted hydrothermal-calcination strategy, utilizing grapefruit peel as a reducing agent and C resource. The calcination temperature and the mass ratio of biomass were optimized to obtain the optimal nanocomposite, which shows excellent adsorptive and visible-light photocatalytic performance in the removal of diverse antibiotic and dye pollutants, including tetracycline, oxytetracycline, ciprofloxacin, sulfamethoxazole, sulfisoxazole, malachite green, and rhodamine B. The remarkable performance can be attributed to the enhanced absorption of light absorption resulting from the localized surface plasmon resonance effect of the semimetal Bi, and the formation of heterogeneous interface between Bi and TiO2, which accelerates the transfer of photogenerated charge. Furthermore, trapping tests and electron spin resonance (ESR) analysis reveal that ∙O2- and h+ are the primary active species involved in the removal of tetracycline. A plausible charge transfer mechanism has been proposed.

Proton hyperfine couplings and Overhauser DNP.

We have prepared trityl radicals with protons at the positions of the -COOH group in the phenyl rings and examined their EPR spectra, which show large - hyperfine couplings, and their dynamic nuclear polarization (DNP) Zeeman field profiles . By assessing these polarizing agents for high-field and Overhauser effect DNP, we gain insight into the roles that these hyperfine couplings and other molecular properties play in the DNP performance of these radicals. Interestingly, we do not observe OE DNP in any of the three molecules we examined. This suggests that hyperfine couplings by themselves are not sufficient to support OE DNP. In this case the electron spin density is ∼75 % localized on the central carbon atom rather than being distributed uniformly over the aromatic rings. This is in contrast to BDPA where the distribution is delocalized. Our findings do not suggest that any of these radicals are particularly well-suited to high-field DNP. Furthermore, we emphasize that polarizing agents can be extremely sensitive to their solvent environment, even obscuring the intrinsic magnetic properties of the radical.

Photo-Excited High-Spin State Ni (III) Species in Mo-Doped Ni3S2 for Efficient Urea Oxidation Reaction.

Designing robust catalystsfor increasing the sluggish kinetics of the urea oxidation reaction (UOR) is challenging. Herein, the regulation of spin states for metal active sites by photoexcitation to facilitate the adsorption of urea and intermediates is demonstrated. Mo-doped nickel sulfide nanoribbon arrays (Mo-Ni3S2@NMF) with excellent light-trapping capacity are successfully prepared. Under AM 1.5G illumination, the activity of the Mo-Ni3S2@NMF exhibits a 50% improvement in the UOR current. Compared with those under dark conditions, Mo-Ni3S2@NMF achieve 10mA cm-2 at 1.315 VRHE for UOR and 1.32 Vcell for urea electrolysis, which are decreases of 15 and 80mV, respectively. The electron spin resonance, in situ Fourier transform infrared spectroscopy analysis and density functional theorycalculations reveal that illumination led to the formation of Ni3+ active sites in a high-spin state, which strengthens the d-p orbital hybridization of Ni-N, hence facilitating the adsorption of urea. C─N cleavage of the *CONN intermediate is further inhibited, which promotes the oxidation of urea molecules via the active N2 pathway, thereby accelerating the UOR rate.

Efficient degradation of Enrofloxacin with novel magnetic MnFe2O4/NiS2 composite as an activator of peroxymonosulfate

The development of highly active and recoverable heterogeneous catalysts for peroxymonosulfate (PMS) activation to remove the persistent presence of antibiotics in aquatic environments, such as Enrofloxacin (ENR), remains a significant challenge. Here, we introduce a pioneering magnetic nanocomposite catalyst, MnFe2O4-NiS2, synthesized via a two-step hydrothermal process, which activates PMS to efficiently degrade ENR. The optimized 0.25MnFe2O4-NiS2/PMS system reached an ENR removal efficiency of 89.9 % within 90 min, outperforming both NiS2/PMS and MnFe2O4/PMS by 5.6 and 2.5 times, respectively. Quenching experiments and electron spin response analysis confirmed SO4•- and •O2– as the primary reactive oxygen species. The enhanced mediated electron transfer capability of the 0.25MnFe2O4-NiS2 nanocomposite improved the redox cycling of Ni (Ⅱ), Mn (Ⅱ) and Fe (Ⅲ) on its surface, as verified by Density Functional Theory calculations. Furthermore, the activation of surface PMS complexes (PMS*) played a crucial role in ENR degradation. The proposed degradation pathways of ENR were confirmed, and toxicity analysis indicated a decrease in intermediate toxicity with the 0.25MnFe2O4-NiS2/PMS system. This study presents an innovative magnetically recoverable, multifunctional catalyst with easy reusability for potential applications in the degradation of organic pollutants.

Photocatalyst for Antibiotics Degradation by In Situ Growth of Direct Z-Type Bi2S3/Bi4Ti3O12 Heterojunction.

Effective removal of antibiotics from aqueous solutions has emerged as a hot research topic in wastewater treatment. Photocatalytic degradation of antibiotics is one of the most effective methods to reduce ecological damage and environmental pollution. In this work, a novel photocatalyst consisting of Z-type heterojunction Bi2S3/Bi4Ti3O12 (BS/BTO) with visible light responses was prepared by an in situ growth method, and the obtained material was used for the degradation of tetracycline hydrochloride (TC). The best performing photocatalyst was BS/BTO-2, which exhibited high photocatalytic activity. The rates of TC degradation reached 97.9% within 40 min of illumination. The photocatalyst demonstrated a high stability and reproducibility even after 5 cycles. Electron spin resonance (EPR) tests and quenching experiments established that ·O2- and h+ were the main species responsible for the elimination of TC. On the basis of theoretical calculations and experimental data, a possible mechanism for the photocatalytic degradation of TC has been proposed. The heterojunction structure, which effectively increases the visible light absorption range and decreases the compounding efficiency of photogenerated electrons and holes, is principally responsible for the photocatalytic performance of BS/BTO. Additionally, liquid chromatography-mass spectrometry (LC-MS) was utilized to investigate the formation and degradation of reaction intermediates. The nontoxicity of the solution after tetracycline degradation was verified by cultivating wheat seeds. This work offers guidance for bismuth-based photocatalysts in the field of sustainable wastewater treatments.

Twisted Benzothieno-Fused BOPHY Dyes as Triplet Photosensitizers with Long-Lived Triplet Excited States.

The synthesis of a series of photostable [b]-benzothieno-fused BOPHY derivatives is reported via one-pot condensation of formylated isoindoles or formylindoles with hydrazine and subsequent boron complexation. These dyes show strong absorption in the deep red region and acceptable fluorescence quantum yields (∼30%). The two fused benzothiophene moieties are slightly deviated from the BOPHY core (with dihedral angles of 6.1 and 10.2°). This slightly twisted conformation brings an enhanced spin-orbit coupling and a reduced energy band gap between singlet and triplet states. The enhanced intersystem cross process endows these series of dyes with a good singlet oxygen quantum yield (up to 63%), a high triplet-state quantum yield (up to 78%), and a long lifetime value (up to 127 μs). Density functional theory calculations indicate that the transition from S1 to T2 states is crucial for triplet-state formation, highlighting their high efficiency in intersystem crossing. The calculated triplet electron spin surface reveals a widespread distribution of triplet states across the conjugated molecular structure, which enhances the Dexter mechanism for triplet energy transfer in these BOPHY photosensitizers. These findings are helpful for thorough understanding of the fundamental ISC process and developing triplet photosensitizers.

A revised terrace stratigraphy and chronology for the Little Ouse River as a framework for interpreting the late Lower and early Middle Palaeolithic of central East Anglia, UK

The Breckland of central East Anglia has a Pleistocene geological sequence spanning c. 1 million years, providing a framework for assessing changes in human technology and behaviour within a single changing palaeolandscape. The geological record and its associated Palaeolithic archaeology divides into three chronological periods: the fluvial deposits of the River Bytham, which span c. 1 ma to 450 ka; the Hoxnian interglacial sites (c. 400 ka); and the fluvial terraces of the post-Anglian drainage network, which records the past c. 400,000 years. This paper focuses on the third of these periods, presenting results from new work on the fluvial sediments and Palaeolithic archaeology associated with the Little Ouse River. Fieldwork was conducted at four Palaeolithic sites; Barnham Heath, Redhill, Santon Downham, and Broomhill Pit. The new sedimentological and stratigraphic data are used in conjunction with existing borehole records to construct long profiles for the river terrace aggradations and establish a terrace stratigraphy for the Little Ouse. Correlation with the marine isotope record is supported by age estimates from electron spin resonance (ESR) dating of sand units within the terrace aggradations. The results provide an age-constrained lithostratigraphic framework for understanding the Lower and Middle Palaeolithic records of the Little Ouse. The results can be added to previous work on the Bytham and Hoxnian sites, enabling an assessment of human activity in the region from c. 800-200 ka.

Amorphous titanium dioxide with synergistic effect of nitrogen doping and oxygen vacancies by photoexcited sol-gel preparation for enhanced photodegradation of tetracycline

In this paper, a novel N-doped amorphous titanium dioxide (N20AT-hν) photocatalyst was prepared by the sol–gel route in which the sol added with salicylaldehyde hydrazone undergoes gel after photoexcitation. Based on a systematic exploration of as-prepared catalysts, it is known that N20AT-hν sample has a particle size of 50–60 nm, a specific surface area of 294.699 m2 g−1, and which is doped with nitrogen elements and forms abundant oxygen vacancies (OVs). The photocatalytic degradation rate of N20AT-hν for 20 mg L−1 tetracycline solution reached 92.23 % after 60 min, and the rate exhibited a slight decrease of 8.68 % after five cycles. Reactive species trapping experiments and electron spin resonance techniques indicate that superoxide radicals and holes are instrumental in photocatalytic degradation. Possible mechanism of forming the active species through OVs mediated traps and electron transfer pathways has been proposed. Furthermore, the predictive evaluations suggest that the degradation of tetracycline solutions by N20AT-hν sample results in less harmful decomposition product.Benefiting from the environmental friendliness of preparation method and the superiority of elemental doping, N20AT-hν material with synergistic effects has great potential for environmental applications.

Effect of ZnO on the structure, optical properties and ESR studies of B2O3–Na2O–SrO–Fe2O3–ZnO glass system

Iron oxide-doped borate glass with composition [(63-x)B2O3 – 10Na2O – 25SrO – 2Fe2O3 – (x)ZnO; x=0, 2, 4, 6, and 8 mol%] was prepared following melt-quench technique. The absence of sharp peaks in the X-ray diffraction (XRD) spectra confirmed the amorphous nature. Furthermore, Fourier transform infrared (FTIR) spectroscopy was employed to study the structure and subnetwork units inside the glass matrix. Moreover, the density and molar volume values were assessed for supplementary studies about the glass structure. Also, the present glass system's optical properties and electron spin resonance were considered. FTIR spectra showed that the basic structural units are trigonal BO3 units, BO4 tetrahedral coordinated units and nonbridging oxygens. Here, a tendency towards the back conversion of BO4 units to BO3 and nonbridging oxygen was also indicated for the further ZnO contents concurring with the optical band gaps and Urbach energy trends. Moreover, FTIR outcomes supported the presence of ZnO as a glass modifier in the form of octahedral coordinated units (ZnO6). Furthermore, the optical bandgaps exhibit a decreasing trend with excessive ZnO contents which is attributed to the increase in optical basicity from 0.681 to 0.729 and the increase in polarizability from 1.690 to 1.776 as well as the creation of nonbridging oxygen. In addition, the metallization criterion values decreased from 0.376 to 0.355 with more ZnO concentrations. Such behavior indicates it is favored towards metallic behavior. Furthermore, the decreased values of g and increased polarizability increase the nonlinear properties of the present glasses. The electron spin resonance spectra show resonance signals at g = 4.12 and 2.04. The resonance signal at 4.12 associated with Fe3+ ions mainly located in rhombically distorted tetrahedral or octahedral coordination. The g = 2.04 resonance signal is ascribed to dipolar interactions. The obtained results suggest that the proposed glasses can be used in nonlinear optical applications.

Element-specific ultrafast lattice dynamics in FePt nanoparticles.

Light-matter interaction at the nanoscale in magnetic alloys and heterostructures is a topic of intense research in view of potential applications in high-density magnetic recording. While the element-specific dynamics of electron spins is directly accessible to resonant x-ray pulses with femtosecond time structure, the possible element-specific atomic motion remains largely unexplored. We use ultrafast electron diffraction (UED) to probe the temporal evolution of lattice Bragg peaks of FePt nanoparticles embedded in a carbon matrix following excitation by an optical femtosecond laser pulse. The diffraction interference between Fe and Pt sublattices enables us to demonstrate that the Fe mean square vibration amplitudes are significantly larger that those of Pt as expected from their different atomic mass. Both are found to increase as energy is transferred from the laser-excited electrons to the lattice. Contrary to this intuitive behavior, we observe a laser-induced lattice expansion that is larger for Pt than for Fe atoms during the first picosecond after laser excitation. This effect points to the strain-wave driven lattice expansion with the longitudinal acoustic Pt motion dominating that of Fe.

Honey-Derived Hydrochar Containing 2,2,6,6-tetramethylpiperidine-1-oxyl Free Radical for Degradation of Aqueous Organic Pollutants

The increasing demand for greener technologies in environmental remediation makes carbon materials from biomass and its derivatives some of the most attractive resources for a sustainable future. However, integrating these materials with stable free radicals remains challenging. This study presents a straightforward one-pot hydrothermal route using raw honey as the carbon source and 4-amino 2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO) as the free radical. The addition of TEMPO derivative initiates Maillard reactions between its amino group and the carbonyl groups of the carbohydrates in honey, resulting in the formation of a functionalized hydrochar with a spherical morphology (~ 8 μm). The presence of free radicals within the carbonaceous matrix was confirmed by electron spin resonance spectroscopy, supported by infrared spectroscopy, elemental analysis, thermal analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy. The free radical content was estimated at 0.4 mmol∙g-1. The material effectively removed methylene blue, fluorescein, and doxorubicin from water in the presence of green oxidants like hydrogen peroxide and sodium hypochlorite. After 24 h, removal efficiencies reached 92% for doxorubicin, 73% for methylene blue, and 23% for fluorescein. Moreover, the hydrochar demonstrated good regeneration capability, maintaining its dye removal efficiency over several cycles.

Graphene quantum dot modified Bi2MoO6 nanoflower for efficient degradation of BPA under visible light

Graphene quantum dots (GQDs) are a novel type of carbon dot material that has significant application value in the field of catalysis due to their non-toxic, stable, abundant surface functional groups, and quantum confinement effects. A unique composite photocatalyst was constructed by modifying GQDs onto Bi2MoO6 (BMO) microsphere-shaped nano petals using simple hydrothermal and sintering techniques. The structural and morphological characterization results indicate that GQDs with size of 10 ​nm are well dispersed on BMO nanosheets, forming close contacts, which can greatly improve the separation efficiency of photo-generated electron-hole pairs under visible light irradiation. In the evaluation of the catalytic performance of BPA solution (20 ​mg/L) with a catalyst content of 20 ​mg under a simulated light source with a power of 300 ​W, the best degradation performance was achieved by a photocatalyst (G6/BMO) with the GQDs mass ratio of 6 ​%, which degraded over 95 ​% of BPA under visible light within 120 ​min, while pure BMO only degraded about 45 ​% of BPA during the same time period. Even if the 400 ​nm filter is removed and directly exposed to Xe lamp radiation, the degradation performance of the optimal composite catalyst is only slightly improved, indicating that the current GQDs/BMO composite catalyst has extremely strong visible light catalytic activity. The improvement of catalytic performance comes from the effective separation of electron-hole pairs caused by the absorption of electrons by GQDs, and the introduction of GQDs to reduce the band gap and enhance visible light absorption, both of which are beneficial for catalytic reactions. Free radical capture and electron spin resonance (ESR) tests indicate that ·OH and ·O2− are the main active species for BPA degradation. Although the current GQDs/BMO catalysts have a simple structure, their catalytic performance has significantly improved, which will guide the design of other semiconductor based photocatalysts.

Quantification of Interfacial Voids Using Positron Annihilation Spectroscopy for Mechanism Study on SiCN Bonding and SiN Bonding

Hybrid bonding for 3D integration requires reliable direct bonding interface of dielectrics. Lately, the spotlight has focused on SiCN/SiCN bonding considering its superior bonding performance by the dangling bonds-facilitated nanovoid closure mechanisms, but it is reported to be sensitive to reactive species especially under the high temperatures. Recent work proposed SiN/SiO2 asymmetric bonding showing a void-free bonding interface and bond energy higher than 2.5 J m−2 as a promising candidate for direct bonding applications. Interestingly, we observed opposite bonding behaviors between SiCN and SiN in corresponding symmetric bonding pair and asymmetric bonding pair (with SiO2). Thus, a comprehensive fundamental understanding on the bonding of different dielectrics is needed to guide the specifications of the bonding layer for enabling a void-free and highly reliable bonding interface. In this study, we systematically quantified the nanovoids in the bonding interface of SiCN/SiCN, SiCN/SiO2, and SiN/SiO2 through positron annihilation spectroscopy and simulation, dangling bond formation by electron spin resonance, and the film passivation property by quasi-steady-state photoconductance. By correlating the film properties and bonding performance, the model of SiCN bonding is extended towards its SiCN/SiO2 asymmetric bonding, and a new model of the nanovoid closure mechanism in SiN bonding is first-time proposed.

Constraining the age of the Middle Stone Age locality of Bargny (Senegal) through a combined OSL-ESR dating approach

The Middle Stone Age (MSA) is the major chrono-cultural phase associated with the emergence and evolution of Homo sapiens in Africa. Despite its importance, the MSA has not been evenly investigated across Africa, and West Africa in particular remains poorly understood. Although new research is beginning to fill in this crucial gap of knowledge, the existing MSA chronologies in West Africa only rely on Optically Stimulated Luminescence (OSL) dating. In this context, the increasing use of a multi-method dating approach appears essential to strengthen this emerging geochronological framework. Here, we apply such approach to constrain the age of Bargny locality, located in close proximity to the modern Senegalese coast (South of Dakar), and which documents one of the oldest MSA occupations in West Africa. Specifically, we combine OSL and Electron Spin Resonance (ESR) methods to date the MSA sites of Bargny 3 (BG3) and Bargny 1 (BG1). A mean OSL age of 127±8 ka may be proposed for the MSA of BG3, which is in good agreement with a mean Ti-H ESR age of 125±14 ka from the same unit. Interestingly, similar ages are obtained by OSL (144±7 ka) and Ti-H ESR (138±14 ka) for the MSA horizon from BG1. While these results illustrate the great potential of the combined OSL-ESR dating approach to establish robust chronologies, they also contribute to improve the geographical and chronological resolution of the MSA record in West Africa. More specifically, they also corroborate the presence of MSA occupations along the Senegambian coast around the MIS 6-MIS 5 transition. In combination with the associated estuarine environments and mangrove forest, the evidence from Bargny adds to the known diversity, and likely complex behaviour, of early human populations living by Africa’s coastlines.

Magnetic MgFeO@BC Derived from Rice Husk as Peroxymonosulfate Activator for Sulfamethoxazole Degradation: Performance and Reaction Mechanism.

Heterogeneous Mg-Fe oxide/biochar (MgFeO@BC) nanocomposites were synthesized by a co-precipitation method and used as biochar-based catalysts to activate peroxymonosulfate (PMS) for sulfamethoxazole (SMX) removal. The optimal conditions for SMX degradation were examined as follows: pH 7.0, MgFeO@BC of 0.4 g/L, PMS concentration of 0.6 mM and SMX concentration of 10.0 mg/L at 25 ℃. In the MgFeO@BC/PMS system, the removal efficiency of SMX was 99.0% in water within 40 min under optimal conditions. In the MgFeO@BC/PMS system, the removal efficiencies of tetracycline (TC), cephalexin (CEX), ciprofloxacin (CIP), 4-chloro-3-methyl phenol (CMP) and SMX within 40 min are 95.3%, 98.4%, 98.2%, 97.5% and 99.0%, respectively. The radical quenching experiments and electron spin resonance (ESR) analysis suggested that both non-radical pathway and radical pathway advanced SMX degradation. SMX was oxidized by sulfate radicals (SO4•-), hydroxyl radicals (•OH) and singlet oxygen (1O2), and SO4•- acted as the main active species. MgFeO@BC exhibits a higher current density, and therefore, a higher electron migration rate and redox capacity. Due to the large number of available binding sites on the surface of MgFeO@BC and the low amount of ion leaching during the catalytic reaction, the system has good anti-interference ability and stability. Finally, the intermediates of SMX were detected.

Z-scheme heterojunction photocatalyst of LaFeO3@CoS for tetracycline hydrochloride degradation by persulfate activation using visible light

An efficient and stable LaFeO3@CoS Z-scheme heterojunction photocatalyst was prepared through the hydrothermal method (HT). Photocatalytic activity of the LaFeO3@CoS was assessed by activating persulfate under visible light for the degradation of tetracycline (0.1 g/L). Under the condition of 0.06 g/L of KHSO5 (Peroxymonosulfate, PMS), the degradation efficiency of 88.7 % was achieved in 40 min using the 0.02 g/L of developed photocatalyst. The degradation kinetic constants of LaFeO3@CoS were 2.79 and 2.23 times higher than those of LaFeO3 and CoS, respectively. Furthermore, the catalyst exhibited excellent stability over five consecutive degradation cycles. Possible degradation mechanisms and the electron transfer mechanism of the heterojunction formed by the LaFeO3@CoS were investigated by quenching experiments, nitrogen N₂ purging experiments, electron spin resonance (ESR) measurements and corresponding electrochemical analyses. In the LaFeO3@CoS/Vis/PMS system, the Z-scheme charge transfer pathway not only accelerated charge transport efficiency but also effectively spatially separated electrons and holes, enhancing the photocatalytic performance of the photocatalyst. Additionally, the generation of reactive species such as 1O2, O2•−, and SO4• − significantly contributed to the improved degradation efficiency of the present catalyst during the degradation process.