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Enhanced luminescent properties of Tb3+-doped transparent oxyfluoride glass-ceramics containing YF3 nanocrystals
摘要： Tb3+-doped transparent oxyfluoride glass-ceramics (GC) containing YF3 nanocrystals have been fabricated via a traditional melt-quenching route with appropriate thermal-treatment. The microstructural, luminescent and optical properties of the synthesized material were investigated systematically. The precipitated particles in the glass phase of GC540 are YF3 nanocrystals with a mean size of around 20 nm, which has been confirmed and estimated by XRD and TEM. Compared with the precursor glass (PG), the emission intensity at 545 nm (5D4→7F5) of YF3: Tb3+-doped GC is significantly enhanced (under ultraviolet and X-rays excitation) and the lifetime of GC is longer. It can be confirmed that the preferential enrichment of Tb3+ in the precipitated low-phonon-energy YF3 nanocrystals can effectively reduce non-radiative transitions. The obtained results confirm that such Tb3+-doped YF3 GC might be useful as a novel X-ray scintillating material for slow event detection.
关键词： X-ray excited luminescence spectra,luminescent properties,YF3,Glass-ceramics
更新于2025-09-23 15:22:29
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Combined photon-echo, luminescence and Raman spectroscopies of layered ensembles of colloidal quantum dots
摘要： Low-temperature dynamics in layered ensembles of core-double-shell colloidal CdSe/CdS/ZnS quantum dots is studied using different experimental techniques, including photoluminescence and absorption spectroscopy, luminescence microscopy, photon echo, transmission electronic microscopy and Raman scattering. A combination of different techniques clarify the nature and hierarchy of relaxation processes in the quantum dot (QD)-composite under study for a broad range of temperatures and timescales. The parameters of local phonons in QDs was found coincident by luminescence and Raman spectroscopies. Different contributions to optical spectra broadening has been recognized and attributed to certain properties of QDs: quantum size effect, electron-phonon coupling, spectral diffusion and natural excited state lifetime.
关键词： Raman spectroscopy,optical dephasing,photon echo,luminescence spectra,quantum dots (QDs),electronic microscopy,low temperatures
更新于2025-09-23 15:19:57
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Coordination Polymeric Ensemble of Silver with Nitrate and 4-(Aminomethyl)benzoate: Synthesis, Crystal Structure, and Luminescence Properties
摘要： Prismatic crystals of Ag3(4-Amba)2(NO3)2 (I) and Ag(4-AmbaH)NO3 (II) are isolated from the reaction mixture of aqueous solutions of 4-aminomethylbenzoic acid (4-AmbaH) and AgNO3 at Т ≈ 70°C. The crystal structure of compound I (СIF file CCDC no. 1851513) and the luminescence properties of compounds I and II are studied. The structure of compound I contains two crystallographically nonequivalent silver atoms Ag(1) and Ag(2) with the octahedral coordination mode (with allowance for Ag···Ag contacts) with different compositions of the internal spheres of the central atoms. Owing to the contacts, the silver atoms are joined into in?nite cluster ribbons (Ag···Ag 3.06?3.27 ?). The carboxylate group of the 4-Amba anion exhibits the bridging properties and binds the silver atoms of both types. The Ag(2) atoms also contact with the oxygen atom of the NO3– ion and coordinate the NH2 group of 4-Amba. The photoluminescence spectra of compounds I and II are of the same type and show the presence of two groups of emission bands with centers at 484 and 543 nm shifted to the red range of the spectrum relative to the band of 4-AmbaH.
关键词： polynuclear silver compounds,X-ray diffraction analysis,luminescence spectra
更新于2025-09-19 17:15:36
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AIP Conference Proceedings [Author(s) 6TH INTERNATIONAL CONFERENCE ON PRODUCTION, ENERGY AND RELIABILITY 2018: World Engineering Science & Technology Congress (ESTCON) - Kuala Lumpur, Malaysia (13–14 August 2018)] - Hydrothermal synthesis of carbon dots and their luminescence
摘要： The synthesis of carbon dots by hydrothermal method with external heating from precursors such as glucose, citric acid, birch bark soot, cowberry, blueberry, redcurrant, and blackbird cherry are investigated. The photoluminescence studies of these carbon dots at di?erent excitation wavelengths was held. It is shown that there is an e?ect of the shift of luminescence spectra intensity peaks with the increasing of excitation wavelengths. The presence of this e?ect open new perspectives for development of composite materials from carbon dots, starch, and epoxy, which can convert the light of the blue LED into the green.
关键词： composite materials,luminescence spectra,hydrothermal synthesis,carbon dots,photoluminescence
更新于2025-09-10 09:29:36
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Preparation and Optical Properties of Trivalent Erbium-Doped CaY <sub/>2</sub> O <sub/>4</sub> Powders Under 980 nm Excitation
摘要： Nanocrystalline CaY2O4:Er3+ up-conversion phosphor was prepared by the sol–gel process. A homogeneous precursor sol was heated on a hot plate and then coagulated gel was pre?red at 300 °C for 4 hr in Ar, followed by ?nal annealing at 1,200 °C for 4 h in Ar. The crystallinity of the powders after annealing was con?rmed using an X-ray diffraction analysis. The shape and particle size of the powders were observed by ?eld emission-scanning electron microscope and transmission electron microscope. Up-conversion luminescence spectra were recorded with a ?uorescent spectrophotometer under a 980-nm excitation. The dependence of the up-converted intensities on pumping powers for powders was obtained by changing the excitation powers at room temperature. X-ray diffraction patterns con?rmed the presence of single orthorhombic crystalline CaY2O4 and no impurity peaks were identi?ed. Micrographical images of 3 mol%-doped CaY2O4 powder indicates that the particle size is uniform, and ranges from 100～200 nm. Up-conversion ef?ciency is the highest when the doping concentration of Er3+ is 3 mol%.
关键词： Up-Conversion Phosphor,Luminescence Spectra,CaY2O4
更新于2025-09-04 15:30:14
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A new approach to studying the luminescence spectra of free icosahedral and crystalline argon nanoclusters
摘要： We propose a new approach to analyzing the cathodoluminescence spectra of free argon nanoclusters, forming in a supersonic jet flowing into vacuum. Based on this approach, we conduct an analysis of the intensities of the luminescence bands of neutral and charged excimer complexes (Ar2)* and (Ar+4)*, measured for clusters with an average size ranging from 500 to 8900 atoms per cluster, and a diameter of 32–87 A? . It is shown that the concentration of the substance condensed into clusters, which determines the integrated intensity of the bands, is proportional to the logarithm of the average size of the clusters in the jet. An analysis of the normalized intensities of the (Ar2)* and (Ar+4)* bands for crystalline clusters with an fcc structure allowed us to establish that the luminescence of neutral (Ar2)* molecules comes from within the volume of the cluster, while the charged complexes (Ar+4)* emit from the subsurface layer. We highlighted an area of cluster dimensions at which the jet is dominated by quasi-crystalline clusters with an icosahedral structure, and it is shown that the transition from icosahedral clusters to fcc structures occurs when the average size of the cluster in the jet is (cid:2)N = (1000–1800) atoms/cluster.
关键词： cathodoluminescence,argon nanoclusters,luminescence spectra,excimer complexes,supersonic jet
更新于2025-09-04 15:30:14