Electron Spin Research Articles

Aeolian activity in the Yarlung Zangbo River Basin, southern Tibetan Plateau, began at 584 ka: implications for the glaciation of the Tibetan Plateau

Aeolian activity on the Tibetan Plateau (TP) has profound effect on the Asian and global climate. In the southern TP, loess deposition widely occurred associated with the massive glaciers and large rivers, recording the interplay history among the aeolian activity, atmosphere, and cryosphere. However, the initiation age of the loess and the factor controlling the loess formation are still controversial. Here, three drilling cores were retrieved from Linzhi area, in the eastern Yarlung Zangbo River Basin of the southern TP, which reached the bedrock and documented the loess development in the southern TP. Based on the optically stimulated luminescence, electron spin resonance, paleomagnetism dating and relative paleointensity correlation, the basal age of the drilling core was constrained at 584 ka revealing the onset of significant aeolian activity on the southern TP. Synthesize this study and previous work on the loess age across the TP, three stages were identified, namely 3600, 2800–2700, and 1200–600 ka, with the age trending younger from north to south. Extensive loess development on the TP occurred between 1200 and 600 ka, which was mainly ascribed to the global cooling during the mid-Pleistocene Transition. During this time, the ampler glaciers extent significantly expanded, westerly displaced southward and the wind intensity also intensified on the TP, which resulted in the enhancement of dust generation, arid and windy condition, leading to the loess preservation and development on the TP. Moreover, numerous evidences suggested that the glaciers on the TP may significantly developed since 800 ka, then enlarged at 500–600 ka, which may lead to the massive dust/loess input to the TP, Chinese Loess Plateau and north Pacific Ocean.

The shot noise in quasi-one-dimensional single spin filter magnetic heterojunctions

Based on the free electronic model and Büttike’s theory on shot noise, we investigated the shot noise of spin electrons in ferromagnetic/non-ferromagnetic insulator/spin filter layer/normal metal (FM/I/SF/NM) quasi-one-dimensional single spin filter tunneling junctions. The calculation results show that the barrier heights and thicknesses of the insulator and spin filter layers strongly affect the values and phases of the Fano factors of spin electrons. Compared with the traditional sandwich structures of ferromagnetic/spin filter layer/normal metal (FM/SF/NM) and ferromagnetic/non-ferromagnetic insulator/normal metal (FM/I/NM), when the thicknesses of the insulator and spin filter layers are very small, in single spin filter magnetic heterojunctions (FM/I/SF/NM), the insulator layer can suppress the Fano factors, while the spin filter layer is easier to separate the Fano factors of electrons whose spin directions are different. Further analysis shows that whether the Rashba coupling in the spin filter layer has an obvious influence on the Fano factors of spin electrons depends on the thickness of the spin filter layer. On the other hand, the Fano factors are strongly dependent on the sizes and directions of the molecular fields of the ferromagnet and spin filter layers. In addition, the electrons are incident with low energy or high energy, and the barrier heights and thicknesses of the spin filter layer and the thicknesses of the insulation layer have a significant effect on the spin-direction-dependent Fano factors of electrons.

Transition from amorphous to crystalline in FeW oxides: Alterations in active center spin state to improve OER performance

Amorphous and crystalline catalysts both have their own advantages to reduce the overpotential of OER. However, there is limited research on the relationship between the OER catalytic performance and the crystallinity degree. Herein, this key issue was explored by preparing FeW oxides with varying degrees of crystallinity. DFT combined with practical experimental results indicate that the change in crystalline state not only affects the electronic interactions in Fe-W-O but also the M-O bond lengths, both influencing the spin state of FeW oxides. At the critical temperature of amorphous-to-crystalline transition, a low-spin state of Fe in FeWO-450 is found to optimize the adsorption of intermediates during OER. FeWO-450 exhibits even better performance than commercial noble metal catalysts and numerous catalysts reported in the literature. This work showcases the effect of crystallinity of metal oxides on electron spin and offer a guidance how to improve OER properties by altering the electron spin states.

Quenching controlled spin exchange interactions and spin selective electron transfer for oxygen evolution reactions

The utilization of magnetic field to enhance electrocatalytic activity has become an effective strategy garnering significant attention in the field of electrocatalysis. Herein, we employ a combination of electrospinning and quenching techniques to successfully synthesize high-entropy oxide (HEO) (FeCoNiCrMn)3O4. The HEO exhibited ferromagnetic properties and further increased the saturation magnetization after the quenching process, primarily due to temperature-mediated magnetic exchange interactions. The OER performance is significantly improved by employing a ferromagnetic ordered catalyst as a spin polarizer in the presence of a magnetic field. The introduction of an exterior magnetic field (∼130 mT) significantly improved the OER performance of HEO-LN (HEO quenching in liquid nitrogen), reducing the overpotential by 39.4 mV at 10 mA cm-2. The improved OER performance is due to the presence of the magnetic field-enhanced electron spin polarization, reducing electron repulsion and enhancing orbital hybridization. These findings not only provide crucial insights into understanding reactions involving magnetic field-induced electrochemistry but also contribute to the rational design of electrocatalysts with magnetic effect.

Gd3+ based spin [formula omitted] linear chain antiferromagnet

We report observations of spin 12 Heisenberg antiferromagnetic order in nanoparticle ensembles of Gd1.89Ni0.02Zn0.03Fe0.55O4 and Gd1.39Ni0.10Zn0.02Fe0.89O4. The staggered molar susceptibility,χm(T), of the ensembles varies as 1/T as T→TN≈17 K. Below TN, the χmT is directly proportional to the temperature before showing another upturn. An excellent agreement between the experimental χm(T) and theoretical models (Bonner-Fisher and Eggert) confirms spin 12 antiferromagnetic coupling within the linear chains of electron spins of the ensembles. The exchange constant is JkB=17K. The antiferromagnetic exchange interaction is also signified by a constriction at the middle of the hysteresis loop, at H=0, which becomes narrow at 5 K. We argue that the origin of the exchange interaction is in the quantum interference of the Bloch waves with the composite energy states of the domain walls.

Azido derivatives of sesquiterpene lactones: Synthesis, anticancer proliferation, and chemistry of nitrogen-centered radicals

Sesquiterpene lactones (SLs) such as parthenolide (PTL) and dehydroleucodine (DhL) selectively kill cancer cells without exerting normal tissue toxicity, potentially due to presence of α-methylene-γ-lactone (αMγL) fragment. We hypothesize that the addition of an azido group to the αMγL fragment of PTL or DhL further augments their anticancer properties as well as radiation sensitivity of cancer cells. Azido-SLs containing the azido group at the C14 methyl position of PTL (i.e., azido-melampomagnolide B, AzMMB) while preserving the mechanistically crucial exomethylene unit of αMγL fragment were also prepared. Sham-irradiated (i.e., unirradiated control) or irradiated human breast cancer cells (MCF7) were treated with different concentrations of azido-PTL (AzPTL) or azido-DhL (AzDhL) along with parental SLs. Proliferation rate of MCF7 cells were measured by MTT-assay, and their colony forming ability was determined by colony formation assay. Both AzPTL and AzDhL significantly suppress proliferation rate and colony forming ability of MCF-7 cells. AzPTL suppressed colony forming ability, not cellular proliferation, following irradiation to a greater extent than PTL at lower concentrations (5 and 10 μM). Electron spin resonance (ESR) studies were performed employing gamma-irradiated homogeneous supercooled aqueous solutions to investigate radical formation through addition of radiation-mediated prehydrated electrons to the azide group of AzPTL and AzDhL and to follow subsequent reactions of these radicals. In AzPTL, formation of a tertiary carbon-centered radical plausibly via a metastable aminyl radical was observed, whereas AzDhL produced both π-aminyl and α-azidoalkyl radicals. These radicals may contribute to the antitumor activities of AzPTL and AzDhL.

Full solar-spectrum available Z-scheme MOF-on-MOF heterostructure for highly efficient photocatalytic VSCs removal

The construction of efficient photocatalysts with strong response to sunlight is crucial for clean and sustainable pollutant degradation and environmental remediation. Herein, a novel MOF-on-MOF structural photocatalyst named HKU@MIL with Z-scheme heterojunction was successfully designed. The light response of the composites effectively extends to the whole solar spectrum through a simple activation process, addressing the issue of the low utilization of sunlight by photocatalysts. The photocatalytic degradation rate of methyl mercaptan by activated HKU@MIL is 2.2, 3.2, and 1.8 times higher than that of NH2-MIL-125, HKUST-1, and HKU/MIL-5 (physical mixtures), respectively. Under simulated sunlight irradiation, the rate constant increases to 0.507 min−1, which is 1.4 times higher than that under visible light. Additionally, the composites exhibit good photocatalytic performance when irradiated with near-infrared light alone. The heterojunction type of the photocatalyst was investigated according to in-depth analysis of X-ray photoelectron spectroscopy. Additionally, the interfacial charge transmission mode of the composites and the probable pathways for methyl mercaptan degradation were explored through band structure analysis, radical quenching tests and electron spin resonance analysis. The improved photocatalytic performance of activated HKU@MIL can be attributed to the full solar spectral response and the successful creation of the Z-scheme electron migration channel, which serves to reinforces the electron pump effect. It achieves this by improving the transmission of photogenerated carriers and ensuring the strongest redox potential. This work presents a new perspective on enhancing the utilization of sunlight by photocatalysts and improving the photocatalytic performance of heterojunction photocatalysts used in environmental remediation.

Strength, plasticity, and spin transition of Fe-N compounds in planetary cores

Elastic and plastic properties of Fe-light element alloys and compounds are needed to determine the compositions and dynamics of planetary cores. Elastic strength and plastic deformation mechanisms and their relationship to electronic properties of ε-Fe7N3 and γ'-Fe4N mixture were investigated by x-ray diffraction and x-ray emission spectroscopy in the diamond anvil cell from 1 bar up to 60 GPa. X-ray diffraction shows that ε-Fe7N3 reaches a pressure of 15–20 GPa before undergoing bulk plasticity at a differential stress of 4.4–10.4 GPa. ε-Fe7N3 is stronger than γ'-Fe4N and hcp-Fe which achieve a flow stress of 1.5–3.6 GPa at 10–15 GPa and 2–3 GPa at ∼20 GPa, respectively. X-ray emission spectroscopy shows that a decrease in electronic spin moment begins before and completes after plastic flow onset for each nitride, suggesting that pressure-driven changes in electronic arrangement do not trigger a plastic response although they may modify the strength and plastic behavior of Fe-N compounds. Plastic deformation in ε-Fe7N3 and hcp-Fe results in a preferred orientation of (0001) normal to maximum compression, while γ'-Fe4N develops a maximum in the (110). These observations may be combined with measurements of elasticity to model seismic properties of cores of small planetary bodies such as Mars, Mercury, and the Moon.

Facile microwave-assisted synthesis of Sb2O3-CuO nanocomposites for catalytic degradation of p-nitrophenol

Recently, bimetallic nanocomposites have been prepared and used in the fields of sensing, catalysis, energy and medicine. However, there are few reports on the preparation and application of new antimony-metal nanocomposites based on two-dimensional antimonene (AM). Herein, Sb2O3-CuO nanocomposites were facilely synthesized by using microwave-assisted heating the mixture solution of AM and Cu2+ ions and utilized for catalytic degradation of p-nitrophenol (PNP). Interestingly, in the mixed solution of AM and various metal ions (Cu2+, Co2+, Mn2+), only the mixture of AM and Cu2+ ions showed efficient fading and absorption reduction effects on PNP after being heated. A series of characterization on morphology and elemental composition confirmed that the nanocomposites obtained after microwave heating was composed of Sb, Cu, O elements (namely Sb2O3-CuO), and was a layered structure loaded with numerous irregular particles. Compared with other catalysts, the nanocomposite has higher catalytic efficiency (the rate constant of 1.07 s−1), and was capable of degrading 96 % of PNP with only 3 s reaction. Electron spin resonance spectroscopy and liquid chromatography-mass spectrometry analysis demonstrated that the copper-mediated Fenton-like reaction in the nanocomposites induced hydroxyl radicals which can efficiently attack and degrade PNP. This study presents a novel approach to the synthesis of antimony-metal nanocomposites and provides a potential solution for the treatment of organic pollutants.

Optical Studies of Doped Two-Dimensional Lead Halide Perovskites: Evidence for Rashba-Split Branches in the Conduction Band.

Two-dimensional (2D) hybrid organic/inorganic perovskites are an emerging materials class for optoelectronic and spintronic applications due to strong excitonic absorption and emission, large spin-orbit coupling, and Rashba spin-splitting effects. For many of the envisioned applications, tuning the majority charge carrier (electron or hole) concentration is desirable, but electronic doping of metal-halide perovskites has proven to be challenging. Here, we demonstrate electron injection into the lower-energy branch of the Rashba-split conduction band of 2D phenethylammonium lead iodide by means of n-type molecular doping at room temperature. The molecular dopant, benzyl viologen (BV), is shown to compensate adventitious p-type impurities and can lead to a tunable Fermi level above the conduction band minimum and increased conductivity in intrinsic samples. The doping-induced carrier concentration is monitored by the observation of free-carrier absorption and intraband optical transitions in the infrared spectral range. These optical measurements allow for an estimation of the Rashba splitting energy ER ≈38 ± 4 meV. Photoinduced quantum beating measurements demonstrate that the excess electron density reduces the electron spin g-factor by ca. 6%. This work demonstrates controllable carrier concentrations in hybrid organic/inorganic perovskites and yields potential for room temperature spin control through the Rashba effect.

A novel xanthan-chitosan based peroxydisulfate controlled-release material for in-situ sustained degradation of tetracycline: Performance, mechanism and application

In situ chemical oxidation (ISCO) is a promising technology to remove the organic pollutants from groundwater on site. In order to ensure the sustainable and long-term treatment performance, the oxidant controlled-release materials (CRMs) are required. In this study, a novel environmentally friendly and low-cost peroxydisulfate CRM (XG/CS-PDS) was synthesized via the mixing and mold method with xanthan, polyvinyl alcohol and chitosan as the binders for the first time. The XG/CS-PDS possessed significantly stable controlled-release properties under different pH and co-anions. 80% PDS in the CRMs could continuously and slowly release within 50 days. The simulation of PDS controlled-release process indicated that the process was controlled by the non-Fickian diffusion. Then the as-prepared CRM was applied to remove tetracycline (TC) from synthesized groundwater with nanoscale zero-valent iron (nZVI) as the PDS activator. The XG/CS-PDS/nZVI system could achieve 100% removal efficiency at different initial TC concentrations (5‐40 mg/L) and had a good anti-interference ability to pH, inorganic co-anions and humic acid. The quenching experiments and electron spin resonance (ESR) revealed that SO4•-, •OH and 1O2 were the main reactive oxygen species (ROS) for the degradation of TC, while SO4•- played the more dominant role. The intermediates and possible degradation pathway of TC were proposed and the toxicity of TC and its intermediates were evaluated. This study provided a new conception for the design of controlled-release material and theoretical strategies for in-situ remediation of groundwater.

Sol-gel transition effect based on konjac glucomannan thermosensitive hydrogel for photo-assisted uranium extraction

Exploiting the intelligent photocatalysts capable of phase separation provides a promising solution to the removal of uranium, which is expected to solve the difficulty in separation and the poor selectivity of traditional photocatalysts in carbonate-containing uranium wastewater. In this paper, the γ-FeOOH/konjac glucomannan grafted with phenolic hydroxyl groups/poly-N-isopropylacrylamide (γ-FeOOH/KGM(Ga)/PNIPAM) thermosensitive hydrogel is proposed as the photocatalysts for extracting uranium from carbonate-containing uranium wastewater. The dynamic phase transformation is demonstrated to confirm the arbitrary transition of γ-FeOOH/KGM(Ga)/PNIPAM thermosensitive hydrogel from a dispersed state with a high specific surface area at low temperatures to a stable aggregated state at high temperatures. Notably, the γ-FeOOH/KGM(Ga)/PNIPAM thermosensitive hydrogel achieves a remarkably high rate of 92.3% in the removal of uranium from the wastewater containing carbonates and maintains the efficiency of uranium removal from uranium mine wastewater at over 90%. Relying on electron spin resonance and free radical capture experiment, we reveal the adsorption-reduction-nucleation-crystallization mechanism of uranium on γ-FeOOH/KGM(Ga)/PNIPAM thermosensitive hydrogel. Overall, this strategy provides a promising solution to treating uranium-contaminated wastewater, showing a massive potential in water purification.

Electron Spin Resonance Spectroscopy on Magnetic van der Waals Compounds

AbstractThe field of research on magnetic van der Waals compounds—a special subclass of quasi-two-dimensional materials—is currently rapidly expanding due to the relevance of these compounds to fundamental research where they serve as a playground for the investigation of different models of quantum magnetism and also in view of their unique magneto-electronic and magneto-optical properties pertinent to novel technological applications. The electron spin resonance (ESR) spectroscopy plays an important role in the exploration of the rich magnetic behavior of van der Waals compounds due to its high sensitivity to magnetic anisotropies and unprecedentedly high energy resolution that altogether enable one to obtain thorough insights into the details of the spin structure in the magnetically ordered state and the low-energy spin dynamics in the ordered and paramagnetic phases. This article provides an overview of the recent achievements in this field made by the ESR spectroscopic techniques encompassing representatives of antiferro- and ferromagnetic van der Waals compounds of different crystal structures and chemical composition as well as of a special category of these materials termed magnetic topological insulators.

Formation of chlorophyll–anionic polysaccharide complex coacervates to improve chlorophyll color stability: Thermodynamic and kinetic stability studies

Chlorophyll (Chl) is the predominant pigment in green plants that can act as a food color and possesses various functional activities. However, its instability and rapid degradation on heating compromise the sensory qualities of its products. This study aimed to enhance the heat resistance of Chl by forming complex coacervates with two negatively charged polysaccharides, sodium alginate (SA) and K-carrageenan (KC). Dynamic light scattering and scanning electron microscopy analyses confirmed the formation of coacervates between Chl and the polysaccharides, whereas Fourier-transform infrared spectroscopy revealed that hydrogen bonding and electrostatic attraction were the primary forces behind complex formation. Electron spin resonance and thermodynamic studies further revealed that these complexes bolstered the thermal stability of Chl, with a maximum improvement of 70.38 % in t1/2 and a reduction of 50.72 % in the degradation rate constant. In addition, the antioxidant capacity of Chl was enhanced up to 35 %. Therefore, this study offers a novel approach to Chl preservation and suggests a viable alternative to artificial pigments in food products.

Theoretical Study for Spin Transport properties of FM-(G/C)10- FM

In the present study, we propose a physical model to study spin transport through DNA system and provide apparent physical mechanism for spin dependent phenomenon. The system considered in our work is DNA bases guanine-cytosine coupled to two ferromagnetic leads (FM-(G/C)10-FM) in parallel and anti-parallel configuration case, throughout magnetic quantum contacts. Our treatment is based on the tight binding model to derive obvious formula for the transmission spectrum which is employed to investigate the spin dependent current-bias voltage characteristics and the temperature - Conductance dependence. Our calculations of for strong, weak and without backbone regimes. Various factors are involved in our -study. These are the electrical contacts between DNA molecules and electrodes, the structure of DNA molecule and the environment around DNA molecule. The system spin dependent factors, that are investigated extensively in our study include the spin dependent coupling between subsystems, the quantum contacts between active region and electrodes, majority and minority electrons spin in the ferromagnetic leads as well as externally applied bias voltage. Variation of these factors can enhanced or suppressed spin transport through (G/C)10 molecule. The transmission spectrum calculations conform that the spin transport throughout (G/C)10 originates by a coherent tunneling process between neighboring bases through the overlapping of the LUMO orbitals of the bases. Our results showed that the spin-polarized transport that can be effectively regulated by the type of regime as well as the spin configuration in the leads which can exhibit efficient spin filtering and spin switching by employing the spin blockade phenomenon

Advancing photopolymerization and 3D printing: High-Performance NiII complexes bearing N2O2 Schiff-base ligands as photocatalysts

New high-performance photocatalysts based on metal structures are being developed for polymerization. However, using low-cost metals while ensuring effectiveness is challenging. In this study, two NiII complexes NiL1 and NiL2 were synthesized using N2O2 Schiff-base ligands bearing π-extended rings (naphthaldehyde (H2L1) and phenylsalicylaldehyde (H2L2) groups), respectively. These complexes were characterized by FTIR, UV–Vis and 1H NMR spectroscopy, elemental analysis, cyclic voltammetry, and MALDI-TOF mass spectrometry. NiL1 and NiL2 were evaluated in photoinitiating system as new photocatalysts for the Free Radical Photopolymerization of Ethoxylated (3) Trimethylolpropane Triacrylate (TMPETA) for violet and green light. Three-component systems were employed in the presence of Di-tert-butyl-diphenyl iodonium hexafluorophosphate (Iod) and ethyl dimethylaminobenzoate (EDB). The absorption, luminescence, and redox properties of nickel complexes and ligands were explored and compared for a better understanding of their structure/reactivity relationship. The designed nickel complexes showed good photoinitiation abilities. NiL2 exhibited the highest monomer conversion, and it was investigated in the on–off process under green light irradiation, demonstrating the efficiency of the system in reactivating the polymerization process. An oxidative pathway mechanism was proposed based on free energy, steady state photolysis and electron spin resonance spin trapping experiments. The best system was successfully applied in cationic photopolymerization and 3D printing.

Middle Loire Valley settlement: First chronology using ESR on quartz grains

Over the past two decades, stepped-terrace systems within the Loire River basin's tributaries have undergone comprehensive multidisciplinary studies, encompassing Quaternary geology, prehistory and geochronology. Surprisingly, the geochronological exploration of the Loire River itself, the longest river in France, and its fossil stepped terraces system has been relatively limited, especially in the middle section near Orléans. However, for about fifty years, this region has been pivotal in providing evidence of the historical confluence of two ancient rivers, shaping the current Loire Valley. Researchers have suggested the existence of a Plio-Pleistocene Loire paleo-river, flowing northward from the Massif Central to the Seine valley and eventually reaching the English Channel. Subsequently, this Loire River would have underwent a reorientation of its flow westward, from the Blois area to the Atlantic Ocean, after being disconnected from its previous course.The absence of alluvial deposits in the area between the current Loire valley and the Seine valley, attributed to substantial erosion, prevents direct exploration of evidence related to the south-north paleo-river. To address this challenge, the hypothesis suggests that the preserved alluvial terraces in the intermediate sector were established post-capture, offering an opportunity to determine when this significant geological event occurred. Through the application of Electron Spin Resonance (ESR) quartz dating, a chronological model for the Middle Loire has been then constructed. This model identifies five distinct phases in the evolution of the Middle Loire system, spanning from 800 ka to the present day. These phases indicate a gradual capture process, initiating between 900 and 800 ka, resulting in alterations to fluvial dynamics and ultimately leading to the establishment of the current course approximately 250 ka.

ESR chronology of the endokarstic deposits of Galería complex (Sierra de Atapuerca, Spain)

The Galería karstic complex, situated within the Atapuerca Multilevel Karst system (Burgos, Spain), records an impressive sedimentary sequence from the Early to Middle Pleistocene period. One of the notable features of this complex is the presence of thick fluvial deposits (waterlain facies), providing a detailed record of the transitional moment between the formation of the middle and lower Atapuerca karst levels. Examining these sediments, barely dated thus far, is crucial for gaining a comprehensive understanding of fluvio-karstic dynamics at the Atapuerca site. In our study, we conducted dating analyses on sediment samples from different areas of the Galería complex using Electron Spin Resonance (ESR) on quartz grains (4 samples from Covacha de los Zarpazos and 1 from Tres Simas Norte outcrops) and paleomagnetism (12 samples). The aim was to refine the chronological framework of the Galería complex, providing ages for the formation of these passages. Considering the geological context, our results revealed underestimated Aluminium (Al) ESR ages ranging from 372 ± 78 to 569 ± 80 ka in Covacha de los Zarpazos, along with consistent dates of 1184 ± 120 and 1001 ± 302 ka in Covacha de los Zarpazos and Tres Simas Central, respectively. Our results agree with previous estimates obtained through luminescence dating methods, indicating Middle Pleistocene ages for the samples. In contrast, reverse polarity estimates disagree with those from radiometric dating methods, except for samples ZAR1501 and TSC1501. Caution should be taken when interpreting these ages, as various geological factors including leaching processes from upper zones, post-sedimentary structures, and lithological variations may indicate alterations in the primitive geochemical composition of the sediment. Consequently, these factors can potentially affect the total Dose rate parameter and introduce uncertainties into the age calculations.

Exploring High-Spin Color Centers in Wide Band Gap Semiconductors SiC: A Comprehensive Magnetic Resonance Investigation (EPR and ENDOR Analysis).

High-spin defects (color centers) in wide-gap semiconductors are considered as a basis for the implementation of quantum technologies due to the unique combination of their spin, optical, charge, and coherent properties. A silicon carbide (SiC) crystal can act as a matrix for a wide variety of optically active vacancy-type defects, which manifest themselves as single-photon sources or spin qubits. Among the defects, the nitrogen-vacancy centers (NV) are of particular importance. This paper is devoted to the application of the photoinduced electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) techniques at a high-frequency range (94 GHz) to obtain unique information about the nature and properties of NV defects in SiC crystal of the hexagonal 4H and 6H polytypes. Selective excitation by microwave and radio frequency pulses makes it possible to determine the microscopic structure of the color center, the zero-field splitting constant (D = 1.2-1.3 GHz), the phase coherence time (T2), and the values of hyperfine (≈1.1 MHz) and quadrupole (Cq ≈ 2.45 MHz) interactions and to define the isotropic (a = -1.2 MHz) and anisotropic (b = 10-20 kHz) contributions of the electron-nuclear interaction. The obtained data are essential for the implementation of the NV defects in SiC as quantum registers, enabling the optical initialization of the electron spin to establish spin-photon interfaces. Moreover, the combination of optical, microwave, and radio frequency resonant effects on spin centers within a SiC crystal shows the potential for employing pulse EPR and ENDOR sequences to implement protocols for quantum computing algorithms and gates.

Enhanced Selective Degradation of Pharmaceutical and Personal Care Products by β-Cyclodextrin-Decorated ZIF-67 Nanocomposites in Reclaimed Water.

A peroxymonosulfate oxidation system was developed via modification of β-cyclodextrin (β-CD) on the surface of Fe2+-doped ZIF-67 (CD/Fe@ZIF-67) as an activator. The 99.7% carbamazepine, 91.3% bisphenol A (BPA), and 95.4% diclofenac (DCF) degradation efficiency were achieved within 10 min, 60, and 1 min, respectively. The hydrophobicity of these three pollutants is positively correlated with their adsorption kinetic constants by CD/Fe@ZIF-67 due to the introduction of β-CD. Scavenger experiments and electron spin resonance spectra confirmed that carbamazepine was preferentially oxidized by SO4•- [λ(SO4•-)(70.5%) > λ(•OH)(28.2%) > λ(O2•-)(1.3%)], where SO4•- and O2•- played dominant roles in the degradation of BPA [λ(SO4•-)(71.7%) > λ(O2•-)(22.8%) > λ(•OH)(5.5%)], and O2•- was responsible for DCF removal [λ(O2•-) = 93.2%]. Additionally, the particulate catalyst was immobilized in the shell side of a ceramic membrane in a membrane reactor for catalyst recovery. This reactor achieved nearly 100% removal efficiency under optimal conditions: 0.036 wt % catalyst loading, 0.5 mM peroxymonosulfate concentration, 1 L inflow, 10 mg/L initial carbamazepine concentration, and 0.012 L/min hydraulic retention time. In summary, this study elucidates the active role of β-CD in a polymetallic/peroxymonosulfate system and provides valuable insights into the development of effective oxidation methods for pharmaceutical and personal care products in wastewater.