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Crystal structure and photoluminescence properties of novel garnet Y2-LaCaGa3ZrO12:xLn3+ (Ln = Eu and Tb) phosphors
摘要： A series of novel garnet Y2-xLaCaGa3ZrO12:xLn3+ (0 ≤ x ≤ 0.12; Ln = Eu and Tb) phosphors was prepared by a solid-state reaction. Their structural and photoluminescence properties were characterized by X-ray diffraction, Rietveld refinement, and photoluminescence spectroscopy. The studied Y2-xLaCaGa3ZrO12:xLn3+ phosphors crystallized in a cubic garnet crystal structure and Ia3ˉ d space group. The Eu3+- and Tb3+-doped Y2-xLaCaGa3ZrO12 phosphors exhibited strong red and green light emissions, respectively, and high emission color purity. With increasing Tb3+ content, the emitting color of the Y2-xLaCaGa3ZrO12:xTb3+ phosphors shifted to the green spectral region because of cross-relaxation among Tb3+ ions. The Y2-xLaCaGa3ZrO12:xLn phosphors are suitable for applications in white light-emitting diode and other optoelectronic devices.
关键词： Emission,Photoluminescence,Phosphor,Y2LaCaGa3ZrO12
更新于2025-09-23 15:23:52
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Disc-loss episode in the Be shell optical counterpart to the high-mass X-ray binary IGR J21343+4738
摘要： Context. Present X-ray missions are regularly discovering new X-ray and γ-ray sources. The identification of their counterparts at other wavelengths allows us to determine their nature. Aims. The main goal of this work is to determine the properties of the optical counterpart to the INTEGRAL source IGR J21343+4738, and to study its long-term optical variability. Although its nature as a Be/X-ray binary has been suggested, little is known about its physical parameters. Methods. We have been monitoring IGR J21343+4738 since 2009 in the optical band. We present BVRI optical photometric and spectroscopic observations covering the wavelength band 4000–7500 ?. The photometric data allowed us to derive the colour excess E(B ? V) and estimate the distance. The blue-end spectra were used to determine the spectral type of the optical companion, while the spectra around the Hα line allowed us to study the long-term structural changes in the circumstellar disc. Results. We find that the optical counterpart to IGR J21343+4738 is a V = 14.1 B1IVe shell star located at a distance of ～8.5 kpc. The Hα line changed from an absorption-dominated profile to an emission-dominated profile, and then back again into absorption. In addition, fast line profile asymmetries were observed once the disc developed. Although the Balmer lines are the most strongly affected by shell absorption, we find that shell characteristics are also observed in He I lines. Conclusions. The optical spectral variability of IGR J21343+4738 is attributed to the formation of an equatorial disc around the Be star and the development of an enhanced density perturbation that revolves inside the disc. We have witnessed the formation and dissipation of the circumstellar disc. The strong shell profile of the Hα and He I lines and the fact that no transition from the shell phase to a pure emission phase is observed imply that we are seeing the system near edge-on.
关键词： X-rays: binaries,stars: neutron,Be,stars: emission-line,stars: individual: IGR J21343+4738
更新于2025-09-23 15:23:52
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From solar to stellar flare characteristics
摘要： Context. The connection between solar energetic proton events and X-ray flares has been the focus of many studies over the past 13 yr. In the course of these investigations several peak size distribution functions based on Geostationary Operational Environmental Satellite (GOES) measurements of both quantities have been developed. In more recent studies one of these functions has been used to estimate the stellar proton fluence around the M-dwarf star AD Leonis. However, a comparison of the existing peak size distribution functions reveals strong discrepancies with respect to each other. Aims. The aim of this paper is to derive a new peak size distribution function that can be utilized to give a more realistic estimate of the stellar proton flux of G-, K-, and M-dwarf stars. Methods. By updating and extending the GOES-based peak size distribution down to B-class X-ray flare intensities with the help of SphinX data from the solar minimum conditions of 2009 and newly derived GOES data between 1975 and 2005, we developed a new power-law peak size distribution function for solar proton fluxes (E > 10 MeV). However, its resulting slope differs from values reported in the literature. Therefore, we also developed a double-power-law peak size distribution function. An extension to much higher X-ray flare intensities (10?1) W m?2 and above, for the first time, results in an approximation of best- and worst-case scenarios of the stellar proton flux around G-, K-, and M-dwarf stars. Results. Investigating the impact of the newly developed peak size distribution function for G-, K-, and M-dwarf star flare intensities we show that in the worst-case scenario previous studies may underestimate the stellar proton flux by roughly one to five orders of magnitude.
关键词： stars: flare,Sun: particle emission,Sun: X-rays,Sun: flares,gamma rays
更新于2025-09-23 15:23:52
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Lanthanide complexes with 2-(tosylamino)-benzylidene-N-(aryloyl)hydrazones - universal luminescent materials
摘要： Lanthanide complexes Ln(L1)(HL1) (Ln = Lu, Yb, Er, Gd, Eu, Sm) and Ln(L2)(HL2) (Ln = Lu, Yb, Gd, Eu) with 2-(tosylamino)-benzylidene-N-(aryloyl)hydrazones (H2L1, aryloyl = 2-hydroxybenzoyl; H2L2, aryloyl = Isonicotinoyl) were obtained with the aim to explore them as new luminescent materials. They were found to form monomeric species independently on the aryloyl nature, their crystal structures were determined from single crystal X-ray data (Yb(L2)(HL2)·0.5(C2H5OH)), as well as from powder X-ray data by Rietveld refinement (Eu(L1)(HL1)). Ytterbium complexes exhibited intense luminescence, which allowed using them in host-free OLEDs, which demonstrated remarkable efficiency of NIR electroluminescence (50 μW/W) at low voltage (5V). Special mechanism of europium luminescence quenching allowed using europium complexes as luminescent thermometers, which demonstrated very high sensitivity up to 12%/K. The theory of luminescence thermometry based on three-level system was proposed which allowed predicting sensitivity with high accuracy (error within 20%).
关键词： lanthanide complexes,OLEDs,luminescent thermometry,NIR emission,luminescent materials
更新于2025-09-23 15:23:52
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Manipulation of Magnetic Dipole Emission from Eu <sup>3+</sup> with Mie-Resonant Dielectric Metasurfaces
摘要： Mie-resonant high-index dielectric nanoparticles and metasurfaces have been suggested as a viable platform for enhancing both electric and magnetic dipole transitions of fluorescent emitters. While the enhancement of the electric dipole transitions by such dielectric nanoparticles has been demonstrated experimentally, the case of magnetic-dipole transitions remains largely unexplored. Here, we study the enhancement of spontaneous emission of Eu3+ ions, featuring both electric and magnetic-dominated dipole transitions, by dielectric metasurfaces composed of Mie-resonant silicon nanocylinders. By coating the metasurfaces with a layer of an Eu3+ doped polymer, we observe an enhancement of the Eu3+ emission associated with the electric (at 610 nm) and magnetic-dominated (at 590 nm) dipole transitions. The enhancement factor depends systematically on the spectral proximity of the atomic transitions to the Mie resonances as well as their multipolar order, which is controlled by the nanocylinder radius. Importantly, the branching ratio of emission via the electric or magnetic transition channel can be modified by carefully designing the metasurface, where the magnetic dipole transition is enhanced more than the electric transition for cylinders with radii of about 130 nm. We confirm our observations by numerical simulations based on the reciprocity principle. Our results open new opportunities for bright nanoscale light sources based on magnetic transitions.
关键词： Purcell enhancement,Dielectric metasurfaces,Mie resonances,Magnetic dipole emission
更新于2025-09-23 15:23:52
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Coherent photo-induced phonon emission in the charge-density-wave state of K<sub>0.3</sub>MoO<sub>3</sub>
摘要： We report on the observation of coherent terahertz (THz) emission from the quasi-one-dimensional charge-density wave (CDW) system, blue bronze (K0.3MoO3), upon photo-excitation with ultrashort near-infrared optical pulses. The emission contains a broadband, low-frequency component due to the photo-Dember effect, which is present over the whole temperature range studied (30-300 K), as well as a narrow-band doublet centered at 1.5 THz, which is only observed in the CDW state and results from the generation of coherent transverse-optical phonons polarized perpendicular to the incommensurate CDW b-axis. As K0.3MoO3 is centrosymmetric, the lowest-order generation mechanism which can account for the polarization dependence of the phonon emission involves either a static surface field or quadrupolar terms due to the optical field gradients at the surface. This phonon signature is also present in the ground-state conductivity, and decays in strength with increasing temperature to vanish above T ~100 K, i.e. significantly below the CDW transition temperature. The temporal behavior of the phonon emission can be well described by a simple model with two coupled modes, which initially oscillate with opposite polarity.
关键词： charge-density wave,terahertz emission,coherent phonons,K0.3MoO3,photo-Dember effect
更新于2025-09-23 15:23:52
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Initial evaluation of <scp>PET</scp> / <scp>CT</scp> with <sup>18</sup> F‐ <scp>FSU</scp> ‐880 targeting prostate‐specific membrane antigen in prostate cancer patients
摘要： This first-in-man study was carried out to evaluate the safety, whole-body distribution, dose estimation, and lesion accumulation of 18F-FSU-880, a newly developed probe targeting prostate-specific membrane antigen. Six prostate cancer patients with known metastatic lesions underwent serial whole-body PET/computed tomography (CT) with 18F-FSU-880. Blood and urine were analyzed before and after PET/CT. Accumulation of 18F-FSU-880 in organs and metastatic lesions in serial PET images were evaluated by measuring the standardized uptake values. From the biodistribution data, the organ doses and whole-body effective dose were calculated using OLINDA/EXM software. 18F-FSU-880 PET/CT could be carried out without significant adverse effects. High physiological uptake was observed in the salivary/lachrymal glands and kidneys. The effective dose was calculated to be 0.921 × 10?2 mSv/MBq. Known metastatic lesions were clearly visualized with high image contrast that increased with time, except in 1 patient, whose bone metastases were well-controlled and inactive. The PET/CT with 18F-FSU-880 could be carried out safely and could clearly visualize active metastatic lesions. The present results warrant further clinical studies with a larger number of cases to verify the clinical utility of 18F-FSU-880 PET/CT in the management of prostate cancer patients.
关键词： dosimetry,prostate cancer,prostate-specific membrane antigen,positron emission tomography/computed tomography,fluorine-18
更新于2025-09-23 15:23:52
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Controlling the emission and absorption spectrum of a quantum emitter in a dynamic environment
摘要： We study the emission spectrum and absorption spectrum of a quantum emitter when it is driven by various pulse sequences. We consider the Uhrig sequence of nonequidistant πx pulses, the periodic sequence of πxπy pulses and the periodic sequence of πz pulses (phase kicks). We find that, similar to the periodic sequence of πx pulses, the Uhrig sequence of πx pulses has emission and absorption that are, with small variations, analogous to those of the resonance fluorescence spectrum. In addition, while the periodic sequence of πz pulses produces a spectrum that is dependent on the detuning between the emitter and the pulse carrier frequency, the Uhrig sequence of nonequidistant πx pulses and the periodic sequence of πxπy pulses have spectra with little dependence on the detuning as long as it stays moderate along with the number of pulses. This implies that they can also, similar to the previously studied periodic sequence of πx pulses, be used to tune the emission or absorption of quantum emitters to specific frequencies, to mitigate inhomogeneous broadening and to enhance the production of indistinguishable photons from emitters in the solid state.
关键词： spectral diffusion,emission/absorption spectrum,solid state emitter,pulse-driven emitter
更新于2025-09-23 15:23:52
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Single-Photon-Emission Computed Tomography with Neutron Activation for Material Inspection
摘要： A single-photon-emission computed tomography (SPECT) system with a lanthanum-bromide (LaBr3:Ce) scintillator was proposed and simulated to detect neutron-activated prompt γ-rays from suspicious materials. The optimized parameters of the SPECT system were calculated to achieve the best performance. Under the optimized conditions, energy spectra, spatial images, and elemental ratios were obtained and employed to identify hidden materials. The carbon-to-oxygen ratios of the materials calculated through the simulations were consistent with the corresponding theoretical values while the calculated nitrogen-to-oxygen ratios were slightly different from the corresponding theoretical values. In the proposed system, not only the energy spectrum of each element but also the characteristic intensity ratios obtained using the reconstructed images were used to identify the unknown elements of hidden materials in the three-dimensional spatial domain. These results demonstrate the feasibility of using the SPECT system in field applications.
关键词： Characteristic elemental intensity ratio,Neutron-activated prompt γ-rays,Single-photon-emission computed tomography
更新于2025-09-23 15:23:52
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Freezing Induced Turn-on Modality for Real-time Imaging in Cryosurgery
摘要： Cryosurgery has attracted great attention for the treatment of tumors due to its obvious advantages. However, it still remains a challenge to determine the volume of frozen tissues in real-time, which greatly lowers the therapeutic efficacy of cryosurgery and hinders its broad application for the treatment of cancers. Herein, we report a freezing induced turn-on strategy for selective real-time imaging of frozen cancer cells. As a type of aggregation induced emission (AIE) fluorogen, TABD-Py molecules interact specifically with ice crystals and form aggregates at the ice/water interface. Consequently, bright fluorescent emission appears upon freezing. Note that TABD-Py molecules are enriched only in the cancer cells and exhibit high biocompatibility as well as low cytotoxicity, therefore a freezing induced turn-on imaging modality for cryosurgery is developed, which will certainly maximize therapeutic efficacy of cryosurgery in treating tumors.
关键词： aggregation induced emission,cancer cells,real-time imaging,freezing,cryosurgery
更新于2025-09-23 15:23:52