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- 2018
- electron-transparent membranes
- micropump
- field emission electron source
- ion source
- ion mobility spectrometry
- Magnetic focused
- Carbon nanotubes
- Field emission cathodes
- Travelling wave tubes
- field electron emission theory
- Optoelectronic Information Science and Engineering
- Electronic Science and Technology
- Physics
- Wroclaw University of Science and Technology
- Beijing Vacuum Electronics Research Institute
- Sun Yat-sen University
- University of Surrey
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Facile synthesis of yellow emissive carbon dots with high quantum yield and their application in construction of fluorescence-labeled shape memory nanocomposite
摘要： Synthesizing carbon dots (CDs) with efficient long-wavelength emissions (i.e., yellow- to red light) generally suffer from sophisticated approaches, time-consuming process, harsh conditions, and requirement of organic solvent; also, a further limitation of the resulting CDs is relatively low quantum yield (QY) in aqueous solution. Herein, novel yellow emitting CDs (Y-CDs) with a considerable QY of 62.8% were synthesized from a precursor comprising resorcinol and o-phenylenediamine via a facile microwave method. To probe the fluorescence mechanism, another typical resorcinol-derived CDs using ethylenediamine as dopant were fabricated as well, showing strong green emission with an absolute QY of 60.6%. Spectroscopic and structural characterizations indicated that the distinct redshift of green to yellow emission depended on the dimension of conjugated sp2-domain and the content of graphitic N heavily, while the excellent QY was highly related to the low proportion of defective sp2 carbon cluster and high nitrogen content within CDs. Moreover, the Y-CDs were confirmed to be capable of introducing additional crosslinking points in poly(vinyl alcohol) (PVA) polymer, which resulted in the Y-CDs-contained nanocomposite behaving superior and tunable water-induced shape recovery performances. Importantly, since being labeled with long-wavelength emission, the responsiveness of PVA/Y-CDs composite will contribute to its versatile utilization in biology-relevant fields.
关键词： shape recovery,fluorescence mechanism,yellow emission,carbon dots,nanocomposite
更新于2025-11-14 15:23:50
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Highly efficient transparent nanophosphor films for tunable white light-emitting layered coatings
摘要： Bright luminescence in rare-earth (RE) nanocrystals, so-called nanophosphors, is generally achieved by choosing a host that enable the effective excitation of the RE activator through charge or energy transfer. Although tungstate, molybdate or vanadate compounds provide the aforementioned transfer, a comparative analysis of the efficiency of such emitters remains elusive. Herein we perform a combined structural and optical analysis, which reveals that the tetragonal GdVO4 matrix gives rise to the highest efficiency among the different transparent nanophosphor films compared. Then we demonstrate that by sequential stacking of optical quality layers made of Eu3+ and Dy3+ doped nanocrystals, it is possible to attain highly transparent white light emitting coatings of tunable shade with photoluminescence quantum yields above 35%. Layering provides precise dynamic tuning of the chromaticity based on the photoexcitation wavelength dependence of the emission of the nanophosphor ensemble without altering the chemical composition of the emitters or degrading their efficiency. Total extinction of incoming radiation along with the high quantum yields achieved make these thin layered phosphors one of the most efficient transparent white converter coatings ever developed.
关键词： rare-earth nanocrystals,transparent coatings,nanophosphors,phosphor materials,white-light emission
更新于2025-11-14 15:23:50
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Aggregation-induced emission (AIE)-active highly emissive novel carbazole-based dyes with various solid-state fluorescence and reversible mechanofluorochromism characteristics
摘要： Three new carbazole-based fluorescent molecules 1-3 functionalized with tetraphenylethene have been successfully synthesized, and these compounds have high thermal stability, and they exhibited different fluorescence in solid states with the superior luminescence quantum yields of 99.04% (1), 98.90% (2) and 39.83% (3). Their aggregation-induced behaviors were explored by the study of photoluminescence spectroscopy. The results showed that luminogens 1-3 exhibited remarkable aggregation-induced emission effect. Furthermore, their distinct mechanical stimulus-responsive fluorescence characteristics were also surveyed by solid-state photoluminescence spectroscopy. Interestingly, the various emitting colors of these luminogens could be changed into the same green, and the repeatabilities of their mechanochromic luminescence behaviors were outstanding, and the powder X-ray diffraction results indicated that the reversible conversion from a crystalline to an amorphous state was responsible for the obvious mechanofluorochromism phenomena of compounds 1-3. This work will be valuable for the exploitation of mechanical-force sensors with typical aggregation-induced emission feature.
关键词： Carbazole,Mechanofluorochromism,Tetraphenylethene,Aggregation-induced emission,Different fluorescence,High thermal stability
更新于2025-11-14 15:23:50
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The Self-Assembly of Cu-In-S Quantum Dots with Aggregation-Induced Emission into 3D Network Triggered by Cation and Its Application as A Novel Metal-Enhanced Fluorescent Nanosensor for Detecting Zn (Ⅱ)
摘要： A novel self-assembly phenomenon triggered by Zn2+ of Cu-In-S quantum dots with aggregation-induced emission effect was presented in this paper. Hydrophilic Cu-In-S quantum dots with aggregation-induced emission effect were successfully prepared. They were monodisperse spherical nanoparticles with the diameter of 2.8 ± 0.4 nm and had weak fluorescence in aqueous solution. However, the solution emitted strong fluorescence after addition of Zn2+. The results of TEM and SEM indicated the monodisperse quantum dots self-assembled into 3D networks of Cu-In-S quantum dots-Zn2+, which hindered the motion of quantum dots. Besides, the Zn2+ in the mixture passivated the surface defects. The phenomenon also proved by florescence lifetime and XPS. Thus the radiation decay decreased and followed by strong fluorescent emission. Interestingly, the degree of aggregation was proportional to the amount of Zn2+ and the fluorescent intensity. Based on this interesting phenomenon, a novel metal enhanced fluorescent nanosensor for detecting Zn2+ was established. The results demonstrated the proposed method had a good selectivity and linearity in the concentration range of 0-800 nmol?L-1 with a limit of detection of 1.99 ppb. These results showed a promising future in the field of metal-enhanced fluorescent probes of the Cu-In-S quantum dots.
关键词： Surface defects,Metal-enhanced sensor,Quantum dots,Restriction of motion,Aggregation-induced emission
更新于2025-11-14 15:23:50
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Multi-stimuli Responsive Supramolecular Gels Based on a D-π-A Structural Cyanostilbene Derivative with Aggregation Induced Emission Properties
摘要： Developing multi-stimuli responsive fluorescent gel materials in a single system remains challenging. Gelator molecules with classical fluorophores suffer from aggregation-caused quenching (ACQ) effect, limiting their applications further. Herein, a novel V-shaped cyanostilbene-based molecule (BAPBIA) with aggregation induced emission (AIE) characteristics and great gelation ability was synthesized and was found to exhibit multi-stimuli responsive behaviors. Reversible gel-sol phase transitions together with emission quenching are realized in response to external stimuli including heating, light and fluoride ion. Especially, the introduction of dimethylaniline group (donor) and cyano group (acceptor) generates a D-π-A structure, further leading to an intramolecular charge transfer (ICT) effect, which enlarges the emission contrast with the variations of the distribution of charge. Thus, upon trifluoroacetic acid (TFA) triggered protonation of dimethylaniline group, not only gel-sol transition but also emission color switching (yellow-to-blue) is achieved due to the loss of the ICT effect. This work paves an easy way to construct fully reversible multi-stimuli responsive fluorescence modulation smart materials.
关键词： supramolecular gels,aggregation induced emission,multi-stimuli responsive,fluorescence switching,cyanostilbene derivative
更新于2025-11-14 15:14:40
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Correction: Boosted visible light photodegradation activity of boron doped rGO/g-C <sub/>3</sub> N <sub/>4</sub> nanocomposites: the role of C–O–C bonds
摘要： A series of two-component co-crystals driven by I···N interactions based on the bipyridine (BIPY) chromophore with one among three different co-former building blocks, iodopentafluorobenzene (IPFB), 1,4-diiodotetrafluorobenzene (DITFB) and 1,3,5-trifluoro-2,4,6-triiodobenzene (IFB), were prepared and analysed via infrared spectroscopy and single-crystal X-ray diffraction. By comparing the I···N distances in the co-crystal structures, we found that the higher the –F ratio in the building blocks the closer the contact of the I···N bond, enhancing the intermolecular interactions in these co-crystals as well. That is, the positive electrostatic potential on the iodine atom(s) in the co-formers was enhanced by the presence of strong electron-withdrawing groups. The distinct spectroscopic behaviours (fluorescence and Raman spectra) among the two-component BIPY co-crystal systems in response to hydrostatic pressure were also investigated. Interestingly, the fluorescence of BIPY–DITFB presented intriguing abnormal evolution from dark to bright, suggesting a new charge transfer state due to the decreased intermolecular distance and the enhanced I···N interactions. Theoretical simulations by Materials Studio also showed the shortened I···N distance and the increased angle of C–I···N, evidencing the enhanced I···N interactions. In contrast, BIPY–IFB showed only slightly enhanced fluorescence intensity at 550 nm consistent with BIPY–DITFB. Once the pressure was relieved, both the Raman and fluorescence spectra for BIPY co-crystal systems entirely self-recovered. Remarkable emission enhancement in a solid-state co-crystal has been rarely reported in previous publications and in fact, this study paves a unique way for designing and developing novel stimuli-responsive photo-functional materials.
关键词： co-crystals,piezochromic materials,halogen bond,intermolecular charge transfer,pressure-induced emission enhancement
更新于2025-11-14 15:14:40
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Optical and luminescence studies on Tm3+-doped KCl single crystals
摘要： Thulium-doped KCl crystals have been successfully grown using Bridgman–Stockbarger technique. The crystals were characterized by optical absorption, photoluminescence (PL), thermoluminescence glow, TL emission, powder X-ray diffraction, scanning electron microscopy (SEM), laser Raman spectroscopy and electron paramagnetic resonance spectroscopy (EPR). PL spectra exhibit broadband blue emission at 468 nm for the application of light-emitting diodes. The trap parameters of the TL glow curve are calculated using Chen’s peak shape method. XRD analysis carried out on the grown crystals and lattice parameters predicted that it crystallized in cubic structure. SEM studies revealed the presence of microcrystalline structure. EPR measurements were made at X-band frequencies with 9–10 GHz ?eld modulation at room temperature, and the g-factor value of 2.4 was calculated by using Lande formula.
关键词： Optical absorption,TL emission,PL,TL glow,EPR
更新于2025-11-14 14:48:53
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Large enhancement in upconverted green emission intensity from Ho3+/Yb3+ co-doped Y2Ti2O7 phosphor in the presence of Zn2+
摘要： The Ho3+, Yb3+ co-doped Y2Ti2O7 phosphor samples have been synthesized through solid state reaction method in the absence and presence of Zn2+ ions. The X-ray diffraction (XRD) analysis show that the phase of the crystal is face centered cubic. The zinc free phosphor shows weak upconversion emission in green region due to 5S2, 5F4 →5I8 transition of Ho3+ ion on excitation with 980 nm radiation. The emission intensity is enhanced significantly in the presence of Zn2+ ions due to increase in crystallinity, particle size and asymmetry in the crystal field. We are reporting ~92 times enhancement in the green emission intensity for 30 mol% co-doping of Zn2+ ions. The lifetime of 5S2 level of Ho3+ ion increases by increasing the concentration of Zn2+ ions. The intense green emission in this material may be suitable for display and other fluorescence based devices.
关键词： Upconversion,Y2Ti2O7 phosphor,Zn2+,Green emission,Ho3+ /Yb3+
更新于2025-11-14 14:48:53
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A cyanostilbene-based molecule with aggregation-induced emission properties: amplified spontaneous emission, protonation effect and electroluminescence
摘要： A terpyridine-substituted cyanostilbene derivative (Z)-2-(4′-([2,2′:6′,2″-terpyridin]-4′-yl)-[1,1′-biphenyl]-4-yl)-3-phenylacrylonitrile (CNSTPy) was synthesized and characterized. The compound exhibits remarkable aggregation-induced emission phenomenon and its single crystal shows a blue emission with fluorescent efficiency as high as 45%. Based on its aggregation state behavior, multiple applications towards exploring its lasing, fluorescence switching and electroluminescence properties were realized. Amplified spontaneous emission (ASE) was observed from the crystal and verified by the variable pump strip method, with a threshold value of ~1.5 mJ cm?2. The protonation/deprotonation processes accompanied by the formation of different molecular aggregation structure result in the distinct blue and yellow emissions. Additionally, the molecule also shows a moderate electroluminescence performance.
关键词： amplified spontaneous emission,cyanostilbene,aggregation-induced emission,protonation effect
更新于2025-09-23 15:23:52
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Development of simultaneous PET and Compton imaging using GAGG-SiPM based pixel detectors
摘要： Positron emission tomography (PET) is considered an important and powerful tool for molecular imaging and medical diagnosis with its high sensitivity. Further, single-photon emission CT (SPECT) is another important imaging modality providing different types of information in medical diagnosis. On the other hand, Compton imaging is a promising technique for future molecular imaging with multi-nuclides based on Compton scattering kinetics. In this regard, previously, we have developed gadolinium aluminum gallium garnet (GAGG)-scintillation-based PET systems and GAGG-scintillation-based Compton imaging systems for environmental applications. Here, we propose and develop a novel PET–Compton hybrid simultaneous imager based on a two-layer structure using thin scatterers and thick absorbers for multi-nuclide imaging, for e.g., simultaneous imaging of PET and SPECT tracers such as 18F-FDG and 111In, respectively. For achieving good spatial resolution of the Compton imager, the energy resolution of the utilized scintillators forms one of the most important characteristics. In this regard, GAGG is a promising scintillator because of its high light yield of over 50 000 photon/MeV and excellent energy resolution of 4% with no background radiation and moderate decay time. In this study, we present the development of a simultaneous PET–Compton detector that consists of an 8 × 8 multi-pixel photon counter/SiPM (MPPC) array individually coupled with a 2.5 × 2.5 × 9-mm3 Ce:Gd3Ga2.7Al2.3O12 scintillators (absorbers) for proof of concept of simultaneous PET and SPECT imaging. The pixel size of the MPPC is 3 mm × 3 mm, and it is operated at 55 V at room temperature. The signals from the MPPC scintillators are individually amplified and converted with a dynamic time over threshold (dTOT) circuit to record the energy and timing information. In image reconstruction, the data acquired with the use of the developed modules are classified into events of either Compton imaging or PET imaging by coincidence detection between scatterer and absorber or between absorber and absorber, respectively. The coincidence events between absorber and absorber are regarded as PET annihilation-gamma events and those between scatterer and absorber are used as Compton imaging events. In our experiment, images of 111In and 18F-FDG, which are used as multi-nuclide tracers, are acquired simultaneously using the developed detector for Compton imaging and PET imaging. We believe that our approach is a significant step forward for medical imaging and related fields.
关键词： Scintillator,Single-photon emission CT,SiPM,Positron emission tomography,Compton imaging
更新于2025-09-23 15:23:52