Search Results (75)

Racetrack NbTi superconducting coil is a key component in Maglev train systems due to its excellent mechanical processing performance and lower construction cost. However, dynamic pressures during high-speed operations can influence contact pressures and cause internal filament damage, leading to critical current degradation and quench, which threaten the stable operation of the superconducting magnet. Considering that the NbTi coil has a typical hierarchical structure and comprises thousands of filaments, this study constructs an efficient multiscale framework combining the finite element method (FEM) and self-consistent clustering analysis (SCA) to study the multiscale responses of the NbTi coil. The mechanical responses of the two-scale racetrack coil under monotonic and periodic pressures are investigated, and the effects of the friction contacts between strands are also discussed. The study reveals that internal contacts significantly influence local contact pressures and microscopic stresses, and periodic loading leads to stress accumulation with cycle times. The proposed framework efficiently captures critical microscale responses and can be applied to other multiscale materials and structures. Full article

This mini-review article is focused on polymeric materials that comprise thermoresponsive and fluorescent organic units. The combination of fluorescent clusters/dots embedded in or grafted with polymers is not considered in this article. Here we review the preparation, characterization, and application of thermoresponsive polymers functionalized covalently with organic fluorescent compounds either compartmentalized or randomly distributed: block-copolymers, self-assembled micelles or vesicles, core–shell nanogels, and their temperature driven self-assembly/shrinkage/expansion and resulting effect in fluorescence: quenching, enhancing, shifting. The applications suggested for these smart-materials are reviewed in the last ten years and range from nanothermometers, drug delivery systems, agents for bioimaging, sensors, and advanced materials for theranostics focused on cancer treatment. This article is organized reviewing the preparation methods, the main characterization techniques, and the application, depending on polymer architecture and the emission wavelength of the fluorophores. Finally, comments, suggestions, and problems to be solved for the advancement of these materials in the future prior to real-life applications are given. Full article

Singlet oxygen (¹O₂) has been proven to simultaneously cause oxidative damage to food and the death of microorganisms. In order to enhance the utilization of ¹O₂ in food systems, this review presents an overview of recent studies on the formation mechanisms of ¹O₂, the damage mechanisms of ¹O₂ on food, the self-protective mechanisms in food against ¹O₂, and the applications of ¹O₂ in food preservation based on the narrative review guidelines. Studies have shown that in vegetable and meat systems, ¹O₂ is mainly produced through photochemical reactions. It has been suggested that proteins and lipids are the main target compounds for oxygen in food. Natural antioxidants in food (such as vitamin E and carotenoids) can remove ¹O₂ through physical or chemical quenching mechanisms. Novel preservation techniques featuring a thin film technology coupled with photosensitizers have been employed on the surface of food to prolong the shelf life. However, how to balance the bactericidal effect of ¹O₂ and its oxidative effects on food still requires further research. It could be feasible that ¹O₂ will play an increasingly important role in the future food industry on the premise of strengthening supervision over food safety risks induced by ¹O₂. Full article

Real-time, high-resolution monitoring of chemically diverse water pollutants remains a critical challenge for smart water management. Here, we report a fully integrated, multi-modal nano-sensor array, combining graphene field-effect transistors, Ag/Au-nanostar surface-enhanced Raman spectroscopy substrates, and CdSe/ZnS quantum dot fluorescence, coupled to an edge-deployable CNN-LSTM architecture that fuses raw electrochemical, vibrational, and photoluminescent signals without manual feature engineering. The 45 mm × 20 mm microfluidic manifold enables continuous flow-through sampling, while 8-bit-quantised inference executes in 31 ms at <12 W. Laboratory calibration over 28,000 samples achieved limits of detection of 12 ppt (Pb²⁺), 17 pM (atrazine) and 87 ng L⁻¹ (nanoplastics), with R² ≥ 0.93 and a mean absolute percentage error <6%. A 24 h deployment in the Cherwell River reproduced natural concentration fluctuations with field R² ≥ 0.92. SHAP and Grad-CAM analyses reveal that the network bases its predictions on Dirac-point shifts, characteristic Raman bands, and early-time fluorescence-quenching kinetics, providing mechanistic interpretability. The platform therefore offers a scalable route to smart water grids, point-of-use drinking water sentinels, and rapid environmental incident response. Future work will address sensor drift through antifouling coatings, enhance cross-site generalisation via federated learning, and create physics-informed digital twins for self-calibrating global monitoring networks. Full article

Organic–inorganic hybrid manganese halides (OIMnHs) have attracted significant attention in the field of optoelectronics due to their outstanding optical properties and low toxicity. However, the development of crystalline compounds with scintillating properties and high light yield remains a significant challenge. In this study, a simple solution method was employed to successfully synthesize a new zero-dimensional (0-D) scintillation crystal, (C₁₃H₂₅N)₂[MnBr₄] (C₁₃H₂₅N = trimethyladamantan-1-aminium). The introduction of bulky and rigid organic cations not only spatially isolates the [MnBr₄]²⁻ tetrahedrons but also effectively expands the Mn···Mn distance, thereby suppressing the concentration quenching and self-absorption effects. This structural design achieves a high photoluminescence quantum yield of about 63.8% at room temperature and a remarkable light yield of 44,300 photons MeV⁻¹. After multiple irradiation cycles, the material retains its stable radiative characteristics. This work highlights the key role of rigid cation engineering in improving luminescence efficiency and scintillation performance and provides new ideas for designing efficient and nontoxic OIMnH-based scintillators. Full article

The misuse of fentanyl poses significant social risks, and accurately and swiftly detecting fentanyl in field settings presents a considerable challenge. Herein, we have designed and synthesized a fluorescent probe TP-CF₃-COOH, which is composed of carboxyl- and trifluoromethyl-binding center tetraphenyl butadiene. The unique centrosymmetric configuration of the TP-CF₃-COOH probe allows for the construction of a fluorescence “on–off” mechanism recognition platform by spatially matching fentanyl and its metabolite norfentanyl. Importantly, this study reveals that the interaction of fentanyl or norfentanyl with TP-CF₃-COOH results in spontaneous self-assembly, generating a three-dimensional complex sphere that is smaller than the two-dimensional sheet fluorescence probe. This self-assembly process results in the quenching of fluorescence. Theoretical calculations demonstrate that this process is accompanied by intermolecular through-space charge transfer during self-assembly, leading to a blue shift in emission wavelength. As a result, the TP-CF₃-COOH fluorescent probe enables the quantitative detection of fentanyl/norfentanyl within a range of 1 × 10⁻²–1 × 10³ μg/L, with limits of detection of 2 × 10⁻⁴ μg/L and 3 × 10⁻⁴ μg/L, respectively. This cost-effective, rapid, and sensitive fluorescent probe holds great potential for the onsite screening and detection of fentanyl and its analogues. Full article

Nitroaromatic-explosives (NEs) not only threaten global security but are also recognized as a highly toxic pollutant. Metal–organic framework Zn-M_s (Zn-M₁, Zn-M₂) were synthesized in this study via the coordination-driven self-assembly of Zn ions and a carbazole-based ligand L containing an aldehyde group. They inherited the excellent fluorescence performance of ligand L and could work as a fluorescent sensor for detecting picric acid (PA) at low concentrations. Zn-M_s showed an emission at 450 nm and exhibited a higher fluorescence quenching efficiency toward PA than other related NEs. The results suggest that the fluorescent response might be attributed to the inner filter effect (IFE); Förster resonance energy transfer (FRET); and possibly, photo-induced electron transfer (PET). In addition, the critical role of the aldehyde group as a recognition site was corroborated using a post-modification strategy. Full article

DNA is an exceptional building block for the fabrication of dynamic supramolecular systems with switchable geometries. Here, a self-assembled, tunable plasmonic–fluorescent nanostructure was developed. A precise sliding motion mechanism was operated through the control of strand displacement reactions, shifting two single-strand DNA (ssDNA) rails connected by a ssDNA quasi-ring structure. The system was reconfigured as a nano-mechanical structure, generating six discrete configurations, and setting specific distances between a tethered gold nanoparticle (AuNP) and a fluorophore, Sulfo-Cyanine3 (Cy3). Each configuration produced a distinct fluorescence emission intensity via plasmonic quenching/enhancement effects, and therefore the structure behaved as a nano-ruler. To optimize the system, the reversible distance-dependent fluorescence quenching or enhancement phenomena were investigated by testing AuNPs with diameters of 5, 10, and 15 nm, yielding the best performances with 10 nm AuNPs. Furthermore, a geometric model of the system was produced, confirming the observed results. The fluorophore–plasmonic surface positioning, conferred by the DNA ruler, led to a finite state nano-machine with six alternative signal outputs. This mechanism, working as a fluorescent reporter, could find application in a multiple-responsive detection system of single-strand nucleic acids, such as viruses or microRNAs. Full article

Singlet oxygen quantum yield (Φ_Δ) is a critical parameter in photodynamic studies, particularly for evaluating photosensitizers’ efficiency in diverse applications such as photodynamic therapy and environmental remediation. Standard photosensitizers, including Rose Bengal, Methylene Blue, and porphyrins, are widely employed as benchmarks for determining Φ_Δ. However, accurate determination of Φ_Δ relies not only on the intrinsic properties of these photosensitizers but also on their experimental conditions, such as concentration. This study investigated the influence of photosensitizer concentration on singlet oxygen quantum yield using several standard photosensitizers. Our findings revealed a significant decrease in Φ_Δ with increasing photosensitizer concentrations across all tested compounds. This decline was attributed to self-quenching effects and molecular aggregation, which reduced the efficiency of energy transfer from the excited triplet state of the photosensitizer to molecular oxygen. The results emphasize the importance of optimizing photosensitizer concentration to ensure reliable Φ_Δ measurements and avoid underestimations. This work underscores the need to consider concentration-dependent effects in future studies to ensure accurate and reproducible outcomes. Full article

Interactions between excitatory and inhibitory neurons in the cerebral cortex give rise to different regimes of activity and modulate brain oscillations. A prominent regime in the cortex is the inhibition-stabilized network (ISN), defined by strong recurrent excitation balanced by inhibition. While theoretical models have captured the response of brain circuits in the ISN state, their connectivity is typically hard-wired, leaving unanswered how a network may self-organize to an ISN state and dynamically switch between ISN and non-ISN states to modulate oscillations. Here, we introduce a mean-rate model of coupled Wilson-Cowan equations, link ISN and non-ISN states to Kolmogorov-Sinai entropy, and demonstrate how homeostatic plasticity (HP) allows the network to express both states depending on its level of tonic activity. This mechanism enables the model to capture a broad range of experimental effects, including (i) a paradoxical decrease in inhibitory activity, (ii) a phase offset between excitation and inhibition, and (iii) damped gamma oscillations. Further, the model accounts for experimental work on asynchronous quenching, where an external input suppresses intrinsic oscillations. Together, findings show that oscillatory activity is modulated by the dynamical regime of the network under the control of HP, thus advancing a framework that bridges neural dynamics, entropy, oscillations, and synaptic plasticity. Full article

The self-activated halotungstate Ba₃WO₅Cl₂ was successfully synthesized using a high-temperature solid-state method. X-ray diffraction analysis (XRD) confirmed the formation of a single-phase compound with a monoclinic crystal structure, ensuring the material’s purity and structural integrity. The luminescence properties of Ba₃WO₅Cl₂ were thoroughly investigated using both optical and laser-excitation spectroscopy. The photoluminescent excitation (PLE) and emission (PL) spectra, together with the corresponding decay curves, were recorded across a broad temperature range, from 10 K to 480 K. The charge transfer band (CTB) of the [WO₅Cl] octahedron was clearly identified in both the PL and the PLE spectra under ultraviolet light excitation, indicating efficient energy transfer within the material’s structure. A strong blue emission could be detected around 450 nm, which is characteristic of the material’s luminescent properties. However, this emission exhibited thermal quenching as the temperature increased, a common phenomenon where the luminescence intensity diminishes due to thermal effects. To better understand the thermal quenching behavior, variations in luminescence intensity and decay time were analyzed using a straightforward thermal quenching model. This comprehensive study of Ba₃WO₅Cl₂ luminescent properties not only deepens the understanding of its photophysical behavior but also contributes to the development of novel materials with tailored optical properties for specific technological applications. Full article

Gold nanoclusters (AuNCs) have been widely investigated because of their unique photoluminescence properties. However, the applications of AuNCs are limited by their poor stability and relatively low fluorescence. In the present work, we developed nanocomposites (L-Cys-AuNCs@ZIF-8) with high fluorescence and stability, which were constructed by encapsulating the water-dispersible L-Cys-AuNCs into a ZIF-8 via Zn²⁺-triggered growth strategy without high temperature and pressure. The maximum emission wavelength of the L-Cys-AuNCs@ZIF-8 composite was at 868 nm, and the fluorescence intensity of L-Cys-AuNCs@ZIF-8 was nearly nine-fold compared with L-Cys-AuNCs without the ZIF-8 package. The mechanism investigation by fluorescence spectroscopy and X-ray photoelectron spectroscopy showed that L-Cys-AuNCs@ZIF-8 impeded ligand rotation, induced energy dissipation, and diminished the self-quenching effect, attributing to the spatial distribution of L-Cys-AuNCs. Based on the high fluorescence efficiency of L-Cys-AuNCs@ZIF-8, a “signal off” detective platform was proposed with copper ions as a model analyte, achieving a sensitive detection limit of Cu²⁺ at 16.7 nM. The quenching mechanism was confirmed, showing that the structure of the L-Cys-AuNCs@ZIF-8 nanocomposites was collapsed by the addition of Cu²⁺. Attributing to the strong adsorption ability between copper ions and pyridyl nitrogen, the as-prepared L-Cys-AuNCs@ZIF-8 was shown to accumulate Cu²⁺, and the Zn²⁺ in ZIF-8 was replaced by Cu²⁺. Full article

Arc quenching has many advantages, including generating large amounts of heat in a short time, a self-quenching ability, and simple equipment. The electric arc energy from a TIG welding machine was used to modify the surface properties of S45C Carbon Steel Cylinders. The study focuses on the impact of arc length, current intensity, travel speed, gas flow rate, heating angle, and pulse on surface hardness after arc quenching an S45C steel tube with a cylinder surface. The study found that the hardness reduces from 45.1 HRC to 41.2 HRC as the current intensity increases from 125 A to 140 A. According to Taguchi’s results, the ranking of factors which have the greatest impact on surface hardness are pulse time, travel speed, intensity, gas flow rate, arc length, and heating angle. The pulse time has the highest impact because it directly influences the heating input, followed by the travel speed. Arc length and heating angle, on the other hand, have the least effect. The base metal, heat-affected area, and hardened area are the three distinct areas that make up the microstructure structure. After the arc quenching process, the case hardening depth is represented by the heat-affected zone at 1536 μm. A highly colored residual austenite and a needle-shaped martensite phase make up the hardened region. The hardened region is 1200 μm thick and has a hardness of more than 300 HV0.3. The study’s findings may improve the application and understanding of the arc quenching treatment procedure in the industrial sector. Full article

Porphyrins serve as photosensitizers (PS) in the realm of cancer photodynamic therapy (PDT). Upon excitation by laser light, porphyrins are capable of converting molecular oxygen into highly cytotoxic singlet oxygen (¹O₂). However, the rigid π-conjugated structure of porphyrins frequently results in the formation of aggregates in aqueous solutions, which leads to the self-quenching of the excited state. Cucurbit[n]urils exhibit the capacity to stably bind with porphyrins via host–guest interactions, effectively inhibiting their aggregation and potentially enhancing the therapeutic efficacy of PDT. In this study, water-soluble tetramethyl cucurbit[6]uril (TMeQ[6]) was selected as the host, while four propionic acid group-appended porphyrin cationic (TPPOR) was utilized as guests to construct a supramolecular photosensitizer (TPPOR-2TMeQ[6]) in a molar ratio of 2:1. Further experimental findings demonstrate that the presence of TMeQ[6] inhibits the aggregation of TPPOR through non-covalent interactions. This inhibition reduces the energy difference between the excited singlet and triplet states, thereby enhancing the conversion efficiency of ¹O₂. Moreover, TPPOR-2TMeQ[6] exhibits favorable biocompatibility and minimal dark toxicity against breast cancer cells (4T1). Upon intracellular excitation, the levels of reactive oxygen species (ROS) significantly increase, inducing oxidative stress in 4T1 cells and leading to apoptosis. Consequently, the findings of this study suggest that the enhanced photosensitization achieved through this supramolecular approach is likely to promote the anticancer therapeutic effects of PDT, thereby broadening the application prospects of porphyrins within PDT systems. Full article

Epoxy resin (EP) is an indispensable packaging material for batteries. Excellent thermal and flame-retardant properties of EP can ensure the safety performance of batteries. To solve the low-efficiency flame retardant of EP, nickel phenyl phosphate (NiPP) was synthesized and its surface was modified by polymerization of dopamine (PDA). [3-(hydroxy-phenyl-methylidene) imimine] triazole (DTA) was synthesized using 9,10-dihydro-9-oxygen-10-phosphophene-10-oxide (DOPO), 3-amino-1,2,4-triazole and p-hydroxybenzaldehyde. The hybrid flame retardance NiPP@PDA@DTA was further synthesized by self-assembly between the negative charge on the surface of DTA and the positive charge on the surface of modified NiPP@PDA. Then, NiPP@PDA@DTA was added to EP to prepare EP/NiPP@PDA@DTA composites. The results showed that the incorporation of NiPP@PDA@DTA promoted the residual yield at high temperatures. Furthermore, EP composites showed excellent flame retardancy when NiPP@PDA@DTA was added. The EP/4 wt% NiPP@PDA@DTA composites can reach UL-94 V0 grade with a limit oxygen index (LOI) of 33.7%. While the heat release rate (HRR), total release rate (THR), CO₂ production (CO₂P) and total smoke release (TSR) of EP/4 wt% NiPP@PDA@DTA composites decreased by 16.9%, 30.8%, 16.9% and 27.7% compared with those of EP. These improvements are mainly due to the excellent catalytic carbonization performance of Ni metal and P compounds. The azazole and phosphaphenanthrene groups have the effects of dilution quenching in the gas phase and cross-linking network blocking, as well as enhanced blowing-out effects. Full article