Search Results (71)

Ultrafast spin dynamics is a core research focus for advancing ultrafast spintronic devices, yet its accurate quantitative probing remains a challenge with conventional time-resolved techniques. Herein, we employ double-pump optical pump–terahertz emission spectroscopy (OPTE) to investigate the ultrafast spin dynamics of a Pt/Gd₁₉(Co_0.8Fe_0.2)₈₁/Ta ferrimagnetic rare-earth–transition-metal heterostructure. Experimental measurements resolve a single-step ultrafast demagnetization process with a characteristic time of ~0.42 ± 0.02 ps, followed by two-stage magnetic recovery involving a fast relaxation and a slow relaxation process. The fast and slow recovery time constants show a distinct positive dependence on the control pump fluence, increasing from 2.49 ± 0.11 ps to 3.28 ± 0.03 ps and 57.36 ± 11.28 ps to 164.96 ± 1.61 ps, respectively, as the pump fluence rises from 0.80 to 1.19 mJ/cm². The ~0.42 ps demagnetization timescale is consistent with that of 3d transition metals, indicating the transient magnetic response of the low-Gd-concentration heterostructure is dominated by the CoFe sublattice. Our findings validate that OPTE is an effective approach for the quantitative characterization of electron–lattice–spin coupling processes in spin-based heterostructures and provide critical experimental insights for controllable manipulation of ultrafast spin dynamics, laying a foundation for the design of ultrafast terahertz spintronic devices. Full article

Spin-exchange relaxation-free (SERF) atomic magnetometers have emerged as highly promising candidates for ultra-weak magnetic field detection, particularly in biomagnetic imaging, owing to their exceptional sensitivity, amenability to miniaturization, and near-room-temperature operation. While current miniaturized magnetometers typically employ laser chips with fixed optical power, the quantitative impact of laser power on critical performance metrics remains to be fully elucidated. This study systematically investigates the influence of laser power on sensitivity, bandwidth, and dynamic range by incorporating considerations of power broadening, saturation absorption, and noise constraints. A miniaturized probe, integrated with an actively controlled vertical-cavity surface-emitting laser (VCSEL), was developed for experimental validation. Theoretical and experimental results consistently demonstrate that as optical power increases, sensitivity exhibits a non-monotonic dependence, whereas both bandwidth and dynamic range manifest a monotonic upward trend, aligning well with theoretical simulations. The optimized sensor achieved a peak sensitivity of 16 fT/√Hz at 300 μW, while the bandwidth and dynamic range reached 230 Hz and ±5.4 nT at 500 μW, respectively. This work establishes a robust theoretical and experimental framework for the comprehensive performance optimization of laser-integrated miniaturized atomic magnetometers. Full article

The quantum Mpemba effect (QME) describes the counterintuitive phenomenon where a system initially further from equilibrium relaxes faster than one closer to it. Specifically, the QME associated with symmetry restoration has been extensively investigated across integrable, ergodic, and disordered localized systems. However, its fate in disorder-free ergodicity-breaking settings, such as the Stark many-body localized (Stark-MBL) phase, remains an open question. Here, we explore the dynamics of local $U\left(1\right)$ symmetry restoration in a Stark-MBL XXZ spin-$\frac{1}{2}$ chain, using the Rényi-2 entanglement asymmetry (EA) as a probe. Using an analytical operator-string expansion supported by numerical simulations, we demonstrate that the QME transitions from an initial-state-dependent anomaly in the ergodic phase to a universal feature in the Stark-MBL regime. Moreover, the Mpemba time scales exponentially with the subsystem size, even in the absence of global transport, and is governed by high-order off-resonant processes. We attribute this robust inversion to a Stark-induced hierarchy of relaxation channels that fundamentally constrains the effective Hilbert space dimension. The findings pave the way for utilizing tunable potentials to engineer and control anomalous relaxation timescales in quantum technologies without reliance on quenched disorder. Full article

Plasma-activated water (PAW) is a liquid enriched with reactive oxygen and nitrogen species (RONS), which impart antimicrobial and bioactive properties. In this study, PAW generated in liquid or gas phase under nitrogen or oxygen atmospheres was characterized in terms of pH, electrical conductivity, oxidation-reduction potential, surface tension, and concentrations of H₂O₂ and NO₂⁻. Hydroxyl radical (•OH) formation was confirmed using DIPPMPO as a spin-trapping probe, while antioxidant activity was determined directly in treated water for the first time. The stability of reactive species was assessed over three months at room temperature, 4 °C, and −18 °C. Results indicate that plasma effects on physicochemical parameters depend strongly on the process gas. From a long-term storage perspective, samples maintained at 4 °C stabilized at higher H₂O₂ and NO₂⁻ concentrations. Antioxidant activity persisted for up to 60 days, though at low levels. EPR analysis revealed that hydroxyl radical concentration increased slightly during storage, with 60-day samples showing higher signal intensities compared to fresh PAW. Overall, the findings provide new insights into PAW composition, radical dynamics, and stability, highlighting the influence of gas atmosphere and storage conditions on its properties and supporting its potential for applications in the food, agriculture, and biomedical sectors. Full article

The local segmental mobility of polymer chains in polydimethylsiloxane (PDMS) plays a critical role in determining the material’s behaviour. Incorporation of zeolite particles can modify these local dynamics, which is crucial as they affect the overall performance of the resulting composite material with potential for various industrial applications. The aim of this study was to investigate the influence of zeolite addition on the local dynamic behaviour of PDMS chain segments in PDMS–zeolite composites. To investigate the effect of zeolite morphology and loading on the segmental dynamics and phase behaviour of PDMS, Zeolite A (with cubic and spherical morphologies) and Zeolite X were incorporated into the PDMS matrix at 20, 30, and 40 wt%. The electron spin resonance (ESR)-spin probe method was used to study molecular dynamics, while the thermal behaviour was analysed using differential scanning calorimetry (DSC). ESR results revealed that the presence of zeolites increases the isothermal crystallisation rate affecting segmental mobility in the amorphous phase below the crystallisation temperature. This effect was found to depend more strongly on zeolite morphology than on filler content. DSC measurements showed no change in glass transition temperature with the addition of zeolite; however, shifts in cold crystallisation and melting behaviour were observed, indicating changes in crystal structure and its degree of perfection. These findings suggest that zeolites act as heterogeneous nucleation agents, with their structural properties playing a critical role in the crystallisation behaviour of PDMS. Full article

Oxidative stress is caused by an imbalance between the formation of reactive oxygen species (ROS) and the activity of antioxidant defense system, which disrupts redox signaling and causes molecular damage. While there are numerous methods to measure oxidative stress, the complex and dynamic nature of ROS production and antioxidant reactions requires a multi-faceted approach. Direct methods such as electron spin resonance (ESR) and fluorescent probes measure ROS directly but are limited by the short lifespan of certain species. Indirect methods such as lipid peroxidation markers (e.g., malondialdehyde, MDA), protein oxidation (e.g., carbonyl content), and DNA damage (e.g., 8-oxo-dG) provide information on oxidative damage, but they do not capture the real-time dynamics of ROS. The antioxidant defense system, which includes enzymatic components such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), further complicates assessment, as it responds dynamically to oxidative challenges. Furthermore, the compartmentalized nature of ROS production in organelles and tissues coupled with the temporal variability of oxidative damage and repair underscores the need to integrate multiple assessment methods. This commentary highlights the limitations of using single assays and emphasizes the importance of combining complementary techniques to achieve a comprehensive assessment of oxidative stress. A multi-method approach ensures accurate identification of ROS dynamics, antioxidant responses, and the extent of oxidative damage, providing crucial insights into redox biology and its impact on health and disease. Full article

M-edge X-ray absorption spectroscopy (XAS), which probes 3p→3d transitions in first-row transition metals, provides detailed insights into oxidation states, spin-states, and local electronic structure with high element and orbital specificity. Operating in the extreme ultraviolet (XUV) region, this technique provides sharp multiplet-resolved features with high sensitivity to ligand field and covalency effects. Compared to K- and L-edge XAS, M-edge spectra exhibit significantly narrower full widths at half maximum (typically 0.3–0.5 eV versus >1 eV at the L-edge and >1.5–2 eV at the K-edge), owing to longer 3p core-hole lifetimes. M-edge measurements are also more surface-sensitive due to the lower photon energy range, making them particularly well-suited for probing thin films, interfaces, and surface-bound species. The advent of tabletop high-harmonic generation (HHG) sources has enabled femtosecond time-resolved M-edge measurements, allowing direct observation of ultrafast photoinduced processes such as charge transfer and spin crossover dynamics. This review presents an overview of the fundamental principles, experimental advances, and current theoretical approaches for interpreting M-edge spectra. We further discuss a range of applications in catalysis, materials science, and coordination chemistry, highlighting the technique’s growing impact and potential for future studies. Full article

Defect engineering has recently emerged as a cutting-edge discipline for precise modulation of electronic structures in nanomaterials, shifting the paradigm in nanoscience from passive ‘inherent defect tolerance’ to proactive ‘defect-controlled design’. The deliberate introduction of defect—including vacancies, dopants, and interfaces—breaks the rigid symmetry of crystalline lattices, enabling new pathways for optimizing catalysis performance. This review systematically summarizes the mechanisms underlying defect-mediated electronic structure at active sites regulation, including (1) reconstruction of the electronic density of states, (2) tuning of coordination microenvironments, (3) charge transfer and localization effects, (4) spin-state and magnetic coupling modulation, and (5) dynamic defect and interface engineering. These mechanisms elucidate how defect-induced electronic restructuring governs catalytic activity and selectivity. We further assess advanced characterization techniques and computational methodologies for probing defects-induced electronic states, offering deeper mechanistic insights at atomic scales. Finally, we highlight recent breakthroughs in defect-engineered nanomaterials for catalytic applications, including hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and beyond, while discussing existing challenges in scalability, defect stability, and structure–property causality. This review aims to provide actionable principles for the rational design of defects to tailor electronic structures toward next-generation energy technologies. Full article

Thulium iron garnet (Tm₃Fe₅O₁₂, TmIG) is a promising material for next-generation spintronic and quantum technologies owing to its high Curie temperature and strong perpendicular magnetic anisotropy. However, conventional magnetometry techniques are limited by insufficient spatial resolution and sensitivity to probe local magnetic phase transitions and critical spin dynamics in thin films. In this study, we present the first quantitative investigation of local magnetic field fluctuations near the Curie temperature in TmIG thin films using nitrogen-vacancy (NV) center-based quantum sensing. By integrating optically detected magnetic resonance (ODMR) and NV spin relaxometry (T₁ measurements) with macroscopic techniques such as SQUID magnetometry and Hall effect measurements, we systematically characterize both the static magnetization and dynamic spin fluctuations across the magnetic phase transition. Our results reveal a pronounced enhancement in NV spin relaxation rates near 360 K, providing direct evidence of critical spin fluctuations at the nanoscale. This work highlights the unique advantages of NV quantum sensors for investigating dynamic critical phenomena in complex magnetic systems and establishes a versatile, multimodal framework for studying local phase transition kinetics in high-temperature magnetic insulators. Full article

Probes sensitive to mechanical stress are in high demand for analyzing pressure distributions in materials. Metal–organic frameworks (MOFs) are especially promising for designing pressure sensors due to their structural tunability. In this work, using classical molecular dynamics (MD) simulations, we clarified the mechanism of exceptional pressure sensitivity of the material based on the UiO-66 framework with a trace amount of spin probes encapsulated in cavities. The role of defects in the MOF structure has been revealed using a combination of electron paramagnetic resonance (EPR) spectroscopy and MD calculations, and potential degradation pathways under mechanical stress have been proposed. The combined MD and EPR study provides valuable insights for further development of new MOF-based sensors applicable for non-destructive pressure mapping in various materials. Full article

The dynamic nature of mitochondria makes live cell imaging an important tool in mitochondrial research. Although imaging using fluorescent probes is the golden standard in studying mitochondrial morphology, these probes might introduce aspecific features. In this study, live cell fluorescent imaging was applied to investigate a pearl-necklace-shaped mitochondrial phenotype that arises when mitochondrial fission is restricted. In this fibroblast-specific pearl-necklace phenotype, constricted and expanded mitochondrial regions alternate. Imaging studies revealed that the formation time of this pearl-necklace phenotype differs between laser scanning confocal, widefield and spinning disk confocal microscopy. We found that the phenotype formation correlates with the excitation of the fluorescent probe and is the result of phototoxicity. Interestingly, the phenotype only arises in cells stained with red mitochondrial dyes. Serial section electron tomography of the pearl-necklace mitochondria revealed that the mitochondrial membranes remained intact, while the cristae structure was altered. Furthermore, filaments and ER were present at the constricted sites. This study illustrates the importance of considering experimental conditions for live cell imaging to prevent imaging artifacts that can have a major impact on the obtained results. Full article

Situated at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory, the PHENIX experiment has for almost two decades been at the forefront of investigations into spin structure and dynamics in high-energy nuclear physics. Although decommissioned in 2016, the PHENIX collaboration has released a number of new results over the past several years that continue to inform the field. Recent longitudinal spin measurements uncover the role of gluon and sea quark polarization in the proton. Transverse spin measurements probe the transverse momentum-dependent (TMD) distributions and higher-twist multiparton correlators that are needed to fully explain partonic dynamics in the initial and final state. Additionally, the effects of heavy ions on spin have been studied by comparing transverse spin measurements between p+p and p+A collisions. These recent results and their wider implications are presented. Full article

This article investigates the influence of dopant molecules on the structural and dynamic properties of lipid bilayers in liposomes, with a focus on the effects of dopant concentration, size, and introduced electric charge. Experimental studies were performed using electron paramagnetic resonance (EPR) spectroscopy with spin probes, complemented by Monte Carlo simulations. Liposomes, formed via lecithin sonication, were doped with compounds of varying concentrations and analyzed using EPR spectroscopy to assess changes in membrane rigidity. Parallel simulations modeled the membrane’s surface layer as a system of electric dipoles on a 20 × 20 rectangular matrix. As in the EPR experiments, the simulation explored the effects of dopant molecules differing in size and charge, while gradually increasing their concentrations in the system. Minimum binding energy configurations were determined from the simulations. The results revealed a strong correlation between the EPR data and simulation outcomes, indicating a clear dependence of membrane stiffening on the concentration, size, and charge of dopant molecules. This effect was most pronounced at low dopant concentrations (~1–1.5% for q = 2 and 1.5–2% for q ≥ 3). No significant stiffening was observed for neutral molecules lacking charge. These findings offer valuable insights into the mechanisms of membrane modulation by dopants and provide a quantitative framework for understanding their impact on lipid bilayer properties. Full article

Nuclear magnetic resonance (NMR) is a versatile method that non-invasively provides detailed insights into the atomic and molecular information of samples containing non-zero spin nuclei, facilitating observations of their structure, dynamics, and interactions. By miniaturizing NMR systems, micro-NMR (µ-NMR) devices overcome the limitations of traditional bulky NMR instruments, making them more portable, cost-effective, and suitable for a wide range of applications. As such, this review aims to provide a comprehensive overview of the recent advancements and potential applications of µ-NMR in the field of biomedicine. Beginning with an overview of the principles underlying NMR, this paper explains the fundamental concepts essential for understanding µ-NMR technology. It then delves into miniaturization techniques, detailing advancements in microcoils and probes and the development and integration with microfluidics, which have enhanced the sensitivity, portability, and versatility of µ-NMR devices. Ultimately, this review discusses the current biomedical applications of µ-NMR, including molecular imaging, metabolomics, biomarker detection, and point-of-care diagnosis, and highlights the potential of this technology to revolutionize precision medicine and healthcare. Despite the promising applications, challenges such as sensitivity, spectral resolution, and integration with other technologies are discussed, along with recent advances and innovations aimed at addressing these limitations. Full article

Mefloquine (MQ) is an antimalarial medication prescribed to treat or malaria prevention.. When taken by children, vomiting usually occurs, and new doses of medication frequently need to be taken. So, developing pediatric medicines using taste-masked antimalarial drug complexes is mandatory for the success of mefloquine administration. The hypothesis that binding mefloquine to an ion-exchange resin (R) could circumvent the drug’s bitter taste problem was proposed, and solid-state ¹³C cross-polarization magic angle spinning (CPMAS) NMR was able to follow MQ–R mixtures through chemical shift and relaxation measurements. The nature of MQ–R complex formation could then be determined. Impedimetric electronic tongue equipment also verified the resinate taste-masking efficiency in vitro. Variations in chemical shifts and structure dynamics measured by proton relaxation properties (e.g., T1ρ^H) were used as probes to follow the extension of mixing and specific interactions that would be present in MQ–R. A significant decrease in T1ρ^H values was observed for MQ carbons in MQ–R complexes, compared to the ones in MQ (from 100–200 ms in MQ to 20–50 ms in an MQ–R complex). The results evidenced that the cationic resin interacts strongly with mefloquine molecules in the formulation of a 1:1 ratio complex. Thus, ¹³C CPMAS NMR allowed the confirmation of the presence of a binding between mefloquine and polacrilin in the MQ–R formulation studied. Full article