Search Results (1,088)

Eu³⁺ is a fluorescent and paramagnetic ion whose emission intensity increases when chelated with enhancers such as tetracycline (TC). In this study, Eu³⁺ was conjugated with citric acid (CA) to form magnetic fluorescent probes capable of capturing trace TC from solutions. The probes were rapidly prepared (~2.25 min) and trapped TC within ~2.5 min under microwave heating. The method enabled sensitive detection of TC, oxytetracycline, and chlortetracycline with detection limits of ~3–7 nM by fluorescence spectroscopy. It was successfully applied to real food samples, including fresh chicken broth and commercial broth cubes, achieving high accuracy (93.7% and 96.6%). This dual-functional probe offers a rapid and sensitive approach for detecting TC residues in complex food matrices, demonstrating strong potential for food-safety monitoring. Full article

Copper ions are essential trace elements that play critical roles in redox reactions, signal transduction, energy metabolism, and regulation of the central nervous system. However, excess copper can induce cytotoxicity and contribute to various pathological conditions, highlighting the need for sensitive and selective detection methods. We report a novel near-infrared (NIR) optical sensor, IRPhen, based on a heptamethine cyanine scaffold conjugated with a 1,10-phenanthroline Cu²⁺-binding receptor. IRPhen exhibits strong NIR absorption and emission (E_x: 750 nm, E_m: 808 nm), high sensitivity, and good selectivity toward Cu²⁺ over competing metal ions. Spectroscopic studies revealed a rapid, reversible 1:1 binding interaction with a binding constant of 1.3 × 10⁶ M⁻¹ and a detection limit of 0.286 µM. The probe demonstrated excellent stability across physiological pH ranges and maintained its performance under competitive conditions. Importantly, IRPhen is cell-permeable and capable of detecting dynamic Cu²⁺ changes in living fibroblast (WS1) cells using confocal microscopy. This sensor design offers a versatile platform for developing NIR optical sensors to study copper homeostasis, elucidating copper-related biological mechanisms, and potentially developing similar NIR probes for other biologically relevant metal ions. Full article

Supernovae (SNe), the catastrophic end of stars’ lives, are among the most energetic phenomena in the universe. Mapping the aftermath of the explosions to the properties of pre-SN stars is challenging due to the lack of knowledge about the evolution of different types of stars. The immediate surroundings of pre-SN stars carry the signature of the progenitors, and radio observations are the best way to examine the ambient media. Since radio emission originates from the interaction of supersonic SN ejecta with the relatively stationary circumstellar medium, with a few years of radio study, the mass-loss history of progenitor stars can be probed from just before the explosion of the star to thousands of years before the onset of the SN. Moreover, this can provide crucial details about the explosions, which are poorly understood to date. In this paper, we review the radio properties of different types of core-collapse explosions and thermonuclear runaways to understand their mass-loss evolution—which allows us to unravel the imprints of the progenitors on the surrounding media and thus the nature of the exploded stars. Additionally, we discuss the current state of the art in this field, including existing and the next-generation radio facilities with enhanced capabilities that provide further details about these explosions. Full article

This study reports the microwave-assisted synthesis and surface modification of carbon quantum dots (CQDs) from natural precursors and their evaluation as fluorescent probes for cancer cell visualization. CQDs were obtained using amino-glucose as the carbon source and betaine, marine collagen, or dopamine as surface modifiers. Further functionalization with 7-amino-4-(trifluoromethyl)coumarin enhanced their fluorescence properties. Spectroscopic analyses confirmed successful surface modification, with coumarin-modified CQDs displaying a strong emission peak at ~500 nm and approximately 1.5-fold higher fluorescence intensity compared to unmodified CQDs. Cytotoxicity testing on MG-63 osteosarcoma cells showed cell viabilities above 80% for selected samples, fulfilling ISO 10993-5 criteria for non-toxicity. In vitro bioimaging of astrocytoma 1321N1 cells demonstrated bright and uniform intracellular staining, confirming effective cellular uptake. Compared with the literature reports of green-synthesized CQDs, our results indicate comparable or superior fluorescence performance and similar levels of biocompatibility. These findings highlight the potential of surface-engineered CQDs as biocompatible nanoprobes for cancer diagnostics and represent an initial step toward their application in the detection of circulating tumor cells (CTCs). Full article

This paper presents the design and evaluation of a fluorescent probe based on fluorescein hydrazide for the selective detection of hypochlorite (ClO⁻), bromide (Br⁻), and iodide (I⁻) ions in solution. The starting chemosensor, fluorescein hydrazide, is suitable for detecting hypochlorite anions in solution, as observed for the first time. The Br⁻ and I⁻ ions could be discovered after activating the probe with hypochlorite. Upon interaction with ClO⁻ ions, the proposed probe exhibits a significant increase in fluorescence emission, a sharp rise in absorbance, and a distinct color change, which is attributed to the conversion from the spirolactam closed form to the open form of the fluorescein ring. ClO⁻ and Br⁻ ions added together were found to brominate the probe in an acetonitrile–water mixture, resulting in a pronounced bathochromic shift in both absorption and emission spectra. Notably, the combination of ClO⁻ and I⁻ was more effective in cleaving the spirolactam ring than hypochlorite alone. Quantum chemical calculations were used to understand the detection mechanism of Br and I ions in a probe–hypochlorite mixture. The probe demonstrated exceptional selectivity and rapid response towards the target analytes, with detection limits determined to be 2.61 μM for ClO⁻, 66 nM for Br⁻, and 13 nM for I⁻. Furthermore, it successfully monitored fluctuations in ClO⁻, Br⁻, and I⁻ concentrations within complex systems, highlighting its potential application in environmental and biological monitoring. Full article

A novel dual-face hot-roll inlaying technique was developed to fabricate a Ag/Cu through-layered composite for use in melt elements for fuse production, including two stages of grooving in a Cu strip followed by separate inlaying of Ag strips at the same positions on the opposite surfaces. The microstructure was characterized using field emission scanning electron microscopy (FE-SEM), electron probe microanalysis (EPMA), X-ray diffraction (XRD), and selective area electron diffraction (SAED). The Ag/Cu interfaces are flat and well bonded, with an elemental interdiffusion layer of less than 2 μm. The same textural components—copper, brass, and S-type components—were identified in both the Ag and Cu layers. However, no well-matched crystal orientation relationship between Ag and Cu was detected at the interface. Moreover, tensile properties and electrical resistance were measured to evaluate the bonding strength and conductivity of the interface. It was found that Ag/Cu bonding strength surpassed the tensile strength of Ag, i.e., 260 MPa. While the total elongation is less than 1%, the Ag layer exhibits excellent plasticity, with a section shrinkage over 90%. Compared with the calculated resistivity with a series circuit model, the tested value of the composite sample, including six Ag/Cu interfaces, increased by only 6.6%, indicating good conductivity of the Ag/Cu interface. Therefore, the obtained composite is a promising candidate for the fabrication of melt elements. Full article

The interaction of an ultra-short, high-power laser pulse with a solid target, in the so-called Target Normal Sheath Acceleration (TNSA) configuration, produces particles in the MeV range. Fast electrons can escape from the target after the interaction, inducing electrostatic fields on the order of TV/m close to the target surface. These fields accelerate MeV protons and heavy ions at the rear of the target, allowing them to escape. The complete process is difficult to probe, as it occurs on the sub-ps timescale. At the INFN-LNF SPARC_LAB test facility, single-shot diagnostics such as the Electro-Optic Sampling (EOS) are being developed and tested for time-resolved direct measurements of the produced electrons and associated longitudinal electric fields. Electrons are the core of the process, and their properties determine the following production of positive charge particles and electromagnetic radiation. Different target geometries and materials are being investigated to analyze the enhancement of fast electron emission and the correlation with positive charge production. Simultaneous observations of electron and proton beams have been performed using two diagnostic lines, the EOS for electrons and a time-of-flight (TOF) detector for protons. This work provides an overview of the previous experiments performed at SPARC_LAB dedicated to the TNSA characterization. Full article

Calcium phosphates are one of the main materials used in biomedicine for bone regeneration purposes. To improve the properties of biocompatible β-Ca₃(PO₄)₂, doping by bioactive, antibacterial is actively used, as well as luminescent ions. Co-doped phosphates Ca_8−xSr_xZnEu(PO₄)₇ with a β-Ca₃(PO₄)₂ (β-TCP)-type structure were synthesized through solid-state synthesis. The β-TCP-type structure was confirmed using X-ray powder diffraction and FTIR spectroscopy. Photoluminescence data, including excitation and emission spectra, decay curves, lifetime values and quantum yields, were collected for all samples. Ca_8−xSr_xZnEu(PO₄)₇ phosphates exhibit strong red-emission due to 4f-4f transitions of Eu³⁺ ions in disordered oxygen surrounding, with quantum yields reaching 54%. The phosphates demonstrated biocompatibility through MTT assay, with successful differentiation of aMSCs into the osteogenic lineage. Antibacterial activity was tested against four bacteria (E. coli, S. aureus, P. aeruginosa, and E. faecalis) and a fungus (C. albicans). It was found that the samples demonstrated antibacterial properties. The growth of E. coli and E. faecalis is significant inhibited by Ca_8−xSr_xZnEu(PO₄)₇ samples with 0 ≤ x ≤ 6.0. Analysis of mixed salt solubility using Eu³⁺ ions as a fluorescent probe showed that increasing Sr²⁺ concentration in Ca_8−xSr_xZnEu(PO₄)₇ delays both β-TCP phase resorption and HAP phase precipitation. These results demonstrate the potential of Ca_8−xSr_xZnEu(PO₄)₇ phosphates for bioimaging and bone healing control. Full article

The problem of poor coupling and wheel breakage is a critical issue in the rapid inspection of rails using contact piezoelectric ultrasonic technology for trolleys and vehicles. To overcome this shortcoming, a non-contact unidirectional Shear Vertical Wave EMAT (USV-EMAT) for rapid rail flaw detection with a larger emission angle is proposed and optimized. First, the core characteristics of the USV-EMAT and the Unidirectional Line-Focusing Shear Vertical Wave EMAT (ULSV-EMAT) are compared and analyzed, including emission angle, directivity, intensity, and detection scan distance. The results confirmed that the USV-EMAT is more suitable for rapid rail flaw detection. Secondly, the orthogonal experimental analysis method was used to optimize the structural parameters of the probe. This study systematically identified the key factors influencing the directivity and intensity of acoustic waves excited by the probe, as well as the detection blind zones. Finally, the structural parameters of the integrated 37° USV-EMAT probe were determined by comparing and analyzing the received signal characteristics of the transmit–receive racetrack coil and the self-transmitting–receiving meander coil. The results show that the optimized probe achieves a 14.3 dB SNR for detecting a 5 mm diameter, 50 mm deep transverse hole in the rail, and a 14.0 dB SNR for a 3 mm diameter, 25 mm long, 50 mm deep flat-bottomed hole. Additionally, this study reveals that as the burial depth of the transverse holes increases, the detection scan distance for such defects exhibits an “N”-shaped trend, with the minimum occurring at a depth of 90 mm. Full article

The osmium(II) polypyridyl complex [Os(tpy)(pydppn)]²⁺ (tpy = 2,2′:6′,2″-terpyridine; pydppn = 3-(pyrid-2′-yl)-4,5,9,16-tetraaza-dibenzo[a,c]naphthacene) was synthesized and characterized to evaluate the effect of an extended planar π-system on photophysical properties and DNA interactions. This complex represents the π-expanded analog of the previously studied [Os(tpy)(pydppz)]²⁺ system. Electrochemical studies revealed a reversible Os(II)/Os(III) oxidation at +0.99 V vs. SCE and five ligand-centered reductions, generally less negative than those of the smaller pydppz analog, consistent with enhanced electron-accepting ability. In acetonitrile, the complex exhibits UV absorption bands at 328 and 473 nm and near-infrared emission at 840 nm, assigned to a long-lived ³MLCT state (τ = 110 ns, Φ = 0.02). Upon titration with calf-thymus DNA, [Os(tpy)(pydppn)]²⁺ shows a pronounced light-switch effect, hypochromism, red-shifted MLCT bands, induced circular dichroism, and an increase in DNA melting temperature (ΔT_m = 8.9 ± 0.5 °C), consistent with intercalative binding. Viscometric titrations further support intercalation, with a binding constant K_B ≈ 1.2 × 10⁶ M⁻¹. Transient absorption spectroscopy indicates that DNA binding prolongs the excited-state lifetime and modifies vibrational relaxation pathways. These results highlight how π-system extension in Os(II) complexes modulates photophysical behavior and DNA affinity, offering insights for the rational design of NIR-emitting, DNA-targeted luminescent probes and potential phototherapeutic agents. Full article

Dual-emission molecularly imprinted membranes (dual@MIPs@mbr) were developed as a proof-of-concept platform for the selective and instrument-free detection of the cancer biomarker carbohydrate antigen 19-9 (CA 19-9). The system integrates a ratiometric fluorescence response by embedding yellow-emitting quantum dots (y-QDs), serving as target-responsive probes, and blue-emitting carbon dots (b-CDs), acting as an internal reference, within a CA 19-9-imprinted polymeric matrix. Specific rebinding of CA 19-9 to the imprinted cavities induced selective quenching of the y-QDs while preserving the b-CDs emission, yielding a visible color shift from yellow/green to blue. This behavior enabled the quantification of CA 19-9 over a linear range of 4–400 U mL⁻¹, with a limit of detection of 0.056 U mL⁻¹ in diluted serum. The membranes showed good selectivity against common serum interferents and maintained short-term photochemical stability. Although the method has not yet been validated using real clinical samples, the pronounced ratiometric response and simple visual readout demonstrate its potential as a low-cost, portable sensing approach for future point-of-care cancer biomarker analysis. Full article

Gamma-ray bursts (GRBs) are widely recognized to exhibit jet-like emission structures, though previous studies often assumed isotropic emission due to observational constraints. This assumption limited our understanding of the intrinsic properties of GRBs. Here, we analyze 40 GRBs with observed X-ray plateaus and jet features, all with measured redshifts. By applying jet corrections to prompt and plateau-phase quantities, we probe their intrinsic behavior. We find that the jet-corrected prompt emission energy ($E_{jet}$) depends less strongly on the jet-corrected X-ray luminosity at the end of the plateau ($L_{X,jet}$). An anti-correlation is also observed between the jet opening angle (${\theta }_{jet}$) and the rest frame peak energy ($E_{p,z}$): $E_{p,z}\propto {\theta }_{jet}^{-0.44\pm 0.13}$ for ISM and $E_{p,z}\propto {\theta }_{jet}^{-0.78\pm 0.13}$ for wind environments, indicating that more collimated jets yield higher peak energies. After jet correction, the $L_X$-$T_{a,z}$ correlation and the three-parameter $L_X$-$T_{a,z}$-$E_{\gamma ,iso}$, $L_X$-$T_{a,z}$-$L_p$ and $L_X$-$T_{a,z}$-$E_{p,z}$ relations are generally weakened. Among these, the first three remain relatively stable, suggesting they reflect intrinsic GRB physics, whereas the $L_X$-$T_{a,z}$-$E_{p,z}$ relation weakens significantly, implying it may be an artifact of the isotropic assumption. We also identify a new three-parameter correlation: ${\theta }_{jet}\left(ISM\right)\propto E_{jet}{\left(ISM\right)}^{0.36\pm 0.06}{E}_{p,z}^{-0.62\pm 0.09}$, ${\theta }_{jet}\left(Wind\right)\propto E_{jet}$${\left(Wind\right)}^{0.29\pm 0.09}$$E_{p,z}^{-0.61\pm 0.09}$. Full article

Most reported fluorescent Al³⁺ probes rely on fluorescence signal enhancement or quenching. Since the change in fluorescence intensity is the sole detection signal, various factors such as instrumental efficiency, environmental conditions, and probe concentration can interfere with the signal output. In contrast, ratiometric probes, which utilize two emission bands for self-calibration, provide significant advantages by minimizing or eliminating these uncertainties. In this study, a naphthalimide-rhodamine based the transition between the cyclic and open-ring forms of rhodamine as an Al³⁺-selective ratiometric probe, in which chitosan was identified as an ideal bridge and biocompatibility. The design concept was that when the target metal ion was present, the fluorescence intensity of naphthalimide remained largely unchanged, serving as an internal standard. In contrast, rhodamine B was employed to label the target molecules, with its fluorescence intensity varying in accordance with the target concentration. A series of experiments were carried out to investigate the fluorometric properties of the grafted polymer P. The results demonstrated that P exhibited selective interaction with Al³⁺ among the various metals tested. Using the fluorescence intensity ratio (I_{603 nm}/I_{538 nm}) of P, a good linear relationship was achieved for Al³⁺ concentrations ranging from 1.0 to 35.0 μM with a detection limit of 0.33 μM was obtained. Meanwhile, we employed the standard addition method for the quantitative analysis and detection of Al³⁺ in commercially available bottled water and tap water, achieving an ideal recovery rate. Full article

Fluorescent nanoprobes operating in the NIR-II window have gained considerable attention for biomedical imaging because of their deep-tissue penetration, reduced scattering, and high spatial resolution. Their tunable optical behavior, flexible surface chemistry, and capacity for multifunctional design enable sensitive detection and targeted visualization of biological structures in vivo. This review highlights recent advances in the design and optical engineering of four widely studied NIR-II nanoprobe families: quantum dots, carbon dots, upconversion nanoparticles, and dye-doped silica nanoparticles. These materials were selected because they offer well-defined architectures, controllable emission properties, and substantial mechanistic insight supporting discussions of imaging performance and translational potential. Particular focus is placed on emerging strategies for activatable, targeted, and ratiometric probe construction. Recent efforts addressing biosafety, large-scale synthesis, optical stability, and early preclinical validation are also summarized to clarify the current progress and remaining challenges that influence clinical readiness. By outlining these developments, this review provides an updated and focused perspective on how engineered NIR-II nanoprobes are advancing toward practical use in biomedical imaging and precision diagnostics. Full article

Cysteine (Cys) is an essential thiol in food and biological systems, yet its selective quantification remains challenging due to interference from structurally related analytes such as homocysteine (Hcy) and glutathione (GSH). Here, we report a hemicyanine-based, turn-off fluorescent probe (PRH) that undergoes Cys-triggered cyclization to release PRH-OH, resulting in fluorescence quenching. PRH exhibits near-infrared emission at 630 nm, enabling low self-absorption and reduced background. The probe affords a broad linear range (0–100 μM) with a detection limit of 0.344 μM, along with high selectivity over Hcy, GSH, and 18 other amino acids. In food matrices (garlic, onion, and dried red pepper), PRH achieved recoveries of 98.8–101.3% with RSD < 2% (n = 3), demonstrating analytical robustness. Live-cell imaging in HeLa cells further verified practical responsiveness: N-ethylmaleimide-mediated thiol depletion increased PRH fluorescence, whereas Cys replenishment decreased it, consistent with the probe’s turn-off behavior. DFT calculations support an intramolecular charge-transfer change upon Cys reaction, correlating with the observed spectral shift. Overall, PRH provides a simple and selective platform for reliable Cys quantification in food samples and for visualizing Cys dynamics in cells. Full article