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The properties of solar radio spikes with harmonics and the associated EUV brightenings
摘要： Solar radio spikes are narrowband, short duration radio bursts. They are excited by the energetic electrons accelerated during small scale magnetic reconnections. Spikes play an important role in diagnosing magnetic reconnections and studying electron accelerations. In this paper, the solar radio spikes observed by the Chashan Solar Observatory (CSO) spectrograph combined with observations from the Solar Dynamics Observatory (SDO) are used to study the properties of spikes with harmonics. The CSO data show that the central frequency ratio of the third to the second harmonic is 1.35 ± 0.01 and the third harmonic has a larger absolute and relative bandwidth, but a shorter duration than the second one. By studying the correlation between light curves of the solar radio spike and those of bright points at different Extreme UltraViolet (EUV) passbands, the best associated EUV bright point and passbands are determined. The spike source properties are discussed based on the extrapolated magnetic field around the associated EUV bright point.
关键词： Radio emission, active regions,Radio bursts, meter-wavelengths and longer, spikes,Magnetic fields, corona
更新于2025-09-23 15:22:29
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Highly Stretchable Carbon Nanotube Fibers with Tunable and Stable Light Emission
摘要： Carbon nanotubes (CNTs) possess intriguing photoluminescence properties, and CNT fibers emit strong incandescent light thus act as macroscopic light sources. So far, straight-shaped CNT fibers are a focus of study and their emission properties are elucidated. Here, the authors show that helical-shaped single-walled carbon nanotube (SWNT) fibers produce uniform and stable incandescent light along the entire fiber under moderate voltages, and the emission intensity is tailored over a wide range by the applied voltage and the elongation of the fiber (up to 70% strain), and in a reversible way during mechanical deformation. Their highly stretchable SWNT fibers with tunable light emission have promising applications in emerging research areas such as wearable electronics and high-performance optoelectronic fiber systems.
关键词： single-wall carbon nanotubes,stretchable device,helical fiber,light emission
更新于2025-09-23 15:22:29
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Novel 4,4′-Fluoresceinoxy Bisphthalonitrile Showing Aggregation-Induced Enhanced Emission and Fluorescence Turn off Behavior to Fe3+ Ions
摘要： A novel 4,4′-fluoresceinoxy bisphthalonitrile FPN is synthesized from fluorescein and 4-nitrophthalonitrile by aromatic nucleophilic ipso nitro substitution reaction. The structure of FPN constitutes phthalonitrile-fluorescein-phthalonitrile, acceptor-donor-acceptor, A-D-A form and the solvatochromic study of newly synthesized compound FPN was done in hexane, cyclohexane, CHCl3, DCM, DMF, acetonitrile, ethanol and in methanol. The aggregation behavior of FPN was investigated in good-poor solvent mixture DMF-water in various proportions and the molecule was found to be exhibiting Aggregation Induced Emission Enhancement AIEE for volume percentage of water beyond 50% with a significant hypsochromic shift of 70 nm in the emission maxima from 458 to 388 nm. This phenomenon is termed as Aggregation Induced Blue Shifted Emission Enhancement AIBSEE and was reported in substituted phthalonitrile for the first time. The chemo sensing activity of FPN with various transition metal ions also has been checked by fluorescence spectroscopy where the new molecule FPN exhibited fluorescence turn OFF behaviour towards Fe3+ ion in acetonitrile-methanol ACN-MeOH solution. The binding stoichiometry of FPN with Fe3+ was verified by Job’s plot analysis and Density Functional Theory DFT-B3LYP computational methodology by using Gaussian 09 software.
关键词： Fe3+ ion,Substituted phthalonitrile,4,4′-fluoresceinoxy bisphthalonitrile FPN,Chemo sensing,Aggregation induced blue shifted emission enhancement AIBSEE
更新于2025-09-23 15:22:29
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Exploring Potential Energy Surfaces for Aggregation‐Induced Emission ‐ from Solution to Crystal
摘要： Aggregation-induced emission (AIE) is a phenomenon where non-luminescent compounds in solution become strongly luminescent in aggregate and solid phase. It provides a fertile ground for luminescent applications that has rapidly developed in the last 15 years. In this review, we focus on the contributions of theory and computations to understanding the molecular mechanism behind it. Starting from initial models, such as restriction of intramolecular rotations (RIR), and the calculation of non-radiative rates with Fermi’s golden rule (FGR), we center on studies of the global excited-state potential energy surfaces that have provided the basis for the restricted access to a conical intersection (RACI) model. In this model, which has been shown to apply for a diverse group of AIEgens, the lack of fluorescence in solution comes from radiationless decay at a CI in solution that is hindered in the aggregate state. We also highlight how intermolecular interactions modulate the photophysics in the aggregate phase, in terms of fluorescence quantum yield and emission color.
关键词： intermolecular interactions,aggregation-induced emission,conical intersections,potential energy surfaces
更新于2025-09-23 15:22:29
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Squaraine dyes: interaction with bovine serum albumin to investigate supramolecular adducts with aggregation-induced emission (AIE) properties
摘要： Bovine Serum Albumin (BSA)–squaraine supramolecular adducts with aggregation-induced emission (AIE) properties were prepared and characterized by spectroscopic methods. While squaraine dyes showed very low fluorescence quantum yield in water, a great enhancement in the fluorescence of the aggregated BSA adducts was achieved due to the abnormal aggregation-induced emission properties of squaraines. The adducts formation was studied from a kinetic point of view showing unexpected structure-properties relationships.
关键词： squaraines,supramolecular adducts,Bovine Serum Albumin (BSA),kinetics,Aggregation-induced emission (AIE)
更新于2025-09-23 15:22:29
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Identification of Potent Caspase-8 Inhibitors from a Library of Fluorescent Natural Products Screened by an AIEgen-based Light-up Probe
摘要： Fluorescent natural products are a rich source of drugs and chemical probes. But their inborn fluorescence may interfere with the fluorescence-based screening assays. Caspase-8 is a key player in apoptosis. Inhibition of caspase-8 found to be beneficial for inflammatory and neurodegenerative diseases. But its small molecular inhibitors remain sparsely reported. In this study, we firstly developed a caspase-8 targeting light-up probe based on an AIEgen. This fluorescent dye has a Stokes shift of 200 nm which could avoid the inborn fluorescence signal of natural products. When screening a library of 86 fluorescent natural products, we found for the first time Gossypol showed potent inhibition towards caspase-8 in vitro and in situ. This unique kind of light-up probe coupled with colored natural products could be an efficient way in the hit discovery for druggable targets.
关键词： natural product,aggregation-induced emission,inhibitor screening,caspase-8,fluorescence
更新于2025-09-23 15:22:29
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Sustainable thermionic emission in CO2, helium and argon surroundings
摘要： Thermionic materials are commonly used in high vacuum (< 10?5 mbar). We measured thermionic emission of different doped metal-oxides cathodes – Zr doped Gd2O3 and Nb doped SrTiO3 (1 1 1) – in a CO2 surrounding, at T = 1300 °C and ～10?4 mbar ≤ p ≤ 300 mbar. Experimental setup validation and reference data were provided by measurements using cathodes made of CeB6, a commercial thermionic material, and by using either helium or argon as the surrounding gas. The study’s results could be used when examining enhancement of CO2 reduction to CO using vibration’s excitation. The thermionic emission of all cathodes decreased gradually as the pressure increased, as expected, but the exposure to CO2 did not cause a deterioration of the Zr doped Gd2O3 cathodes. They retained a reasonable emission, of ～60% and ～40% of the current in vacuum, at a CO2 pressure of 50 mbar and 300 mbar, respectively, over 20 operation hours. The data suggest that in the presence of significant gas pressure in the cathodes surrounding, the electric dipole of CO2 molecules and the cathode’s surface roughness may induce several mechanisms, which could affect the current emission.
关键词： Surface,CO2 helium argon,CO2 reduction,Thermionic emission
更新于2025-09-23 15:22:29
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Optical Band Gap, Local Work Function and Field Emission Properties of MBE Grown β-MoO3 Nanoribbons
摘要： Monoclinic molybdenum trioxide (β-MoO3) nanostructures (shaped like nanoribbons: NRs) were grown on Si(100), Si(5512) and fluorine-doped tin oxide (FTO) by molecular beam epitaxy (MBE) technique under ultra-high vacuum (UHV) conditions. The dependence of substrate conditions and the effective thickness of MoO3 films on the morphology of nanostructures and their structural aspects were reported. The electron microscopy measurements show that the length and the aspect ratio of nanostructures increased by, 260% without any significant change in the width for a change in effective thickness from 5 nm to 30 nm. NRs are grown along <011> for all the effective thickness of MoO3 films. Similarly, when we increased the film thickness from 5 nm to 30 nm, the optical band gap decreased from 3.38± 0.01eV to 3.17± 0.01eV and the local work function increased from 5.397 ± 0.025 eV to 5.757 ± 0.030 eV. Field emission turn-on field decreased from 3.58 V/μm for 10-μA/cm2 to 2.5 V/μm and field enhancement factor increased from 1.1×104 to 5.9×104 for effective thickness variation of 5 nm to 30 nm β-MoO3 structures. The β-MoO3 nanostructures found to be much better than the α-MoO3 nanostructures due to low work function, low turn on field and high field enhancement factor, and are expected to be useful applications.
关键词： β-MoO3 nanostructures,Field emission and Kelvin probe force microscopy (KPFM),Optical band gap,Molecular beam epitaxy (MBE),Electron microscopy
更新于2025-09-23 15:22:29
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Some important notes on ASTA software: A new method of analysis of simple and complex emission and absorption spectral lines
摘要： ASTA is a new spectral analysis software aiming to serve the growing need of an integrated computing environment which will implement efficiently the demanding process of multicomponent analysis. It is a cutting-edge spectral multicomponent analysis software for displaying, fitting and analyzing astronomical spectra of complex emission and absorption line profiles. Equipped with statistical and verification tools it accelerates complex mathematical precision checks and confirms the uniqueness of the calculated physical parameters and the number of the absorption components that construct every Broad Absorption/Emission Line (BAL/BEL) and Discrete Absorption Components (DACs). DACs (in the case of Hot Emission Stars) and BALs/BELs (in the case of Quasars) are spectral lines of the same ion and the same wavelength as the main spectral line, shifted at different ?λ, as they are created in different density regions which rotate and move radially with different velocities. The currently accepted view is that BELs, BALs and DACs may be due to a flow of many individual density enhancements, called clouds, cloudlets or clumps which are optically thick and very small compared with the size of the central continuum source. These density enhancements are not preexisting entities but are formed inside an unstable and turbulent wind and they are indicated by very complex profiles. According to this phenomenon, a prevailing view is that they are not simple absorption/emission lines, but the synthesis of a group of classical absorption line components of the same spectral line. ASTA software equipped with a multicomponent analysis model is a novel approach to curve fit these complex lines focusing on the physical representation of the calculated parameters of each of these components. The BAL Quasar SDSS J114548.38+393746.6 case study is analyzed to demonstrate the potential of ASTA, whereas the Quasar SDSS J000027.01+030715.5 narrow absorption line highlights the flexibility to analyze effectively simple spectral profiles.
关键词： Hot emission stars,BALs and BELs,Multicomponent analysis,Stellar spectroscopy,DACs,Quasars
更新于2025-09-23 15:22:29
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NIR Emission Nanoparticles Based on FRET Composed of AIE Luminogens and NIR Dyes for Two-photon Fluorescence Imaging
摘要： Near-infrared (NIR) nanoparticles (NPs) based on fluorescence resonance energy transfer (FRET) were prepared by co-encapsulation of a red aggregation-induced emission (AIE) molecule, 2-(4-bromophenyl)-3-(4-(4-(diphenylamino)styryl)phenyl)fumaronitrile (TB), and a commercial NIR fluorescence dye, silicon 2,3-naphthalocyanine bis(trihexylsilyloxide) (NIR775) with an amphiphilic polymer poly(styrene-co-maleic anhydride) (PSMA). The surface of the NPs, PSMA@TB/NIR775, was modified with poly(ethylene glycol) (PEG) to increase the in vivo biocompatibility of the NPs. The PSMA@TB/NIR775 NPs showed a strong NIR (780 nm) narrow emission and excellent two-photon absorption property. Moreover, the NPs exhibited good monodispersity, stability, and low cytotoxicity. Under the excitation of a 1040 nm femtosecond (fs) laser, the emission peaks at 680 nm of TB and 780 nm of NIR775 excited by FRET were obtained. We utilized PSMA@TB/NIR775 NPs as fluorescent contrast agents for two-photon excited NIR microscopic imaging, and good NIR imaging effect of mouse brain vasculature was obtained with the imaging depth of about 150 μm. The FRET strategy by co-encapsulating AIE molecule and NIR dye will be helpful in preparing more narrow emission NIR probes for deep-tissue biological imaging.
关键词： Two-photon imaging,FRET,NIR emission,AIE,Amphiphilic polymer
更新于2025-09-23 15:22:29