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Effect of Er3+-doping on 65GeS2-25Ga2S3-10CsCl glass probed by annihilating positrons
摘要： Effect of Er3+-doping resulting in pronounced mid-IR fluorescence functionality was examined first in chalcohalide 65GeS2-25Ga2S3-10CsCl glass using positron annihilation lifetime (PAL) spectroscopy. The detected PAL spectra were reconstructed from unconstrained x2-term analysis employing two-state simple trapping model for one kind of positron trapping free-volume defects, the parameterization being performed at the example of 65GeS2-25Ga2S3-10CsCl glass doped with 0.6 at. % of Er3+. The observed decrease in positron trapping rate was proved to be primary void-evolution process in this Er-activated glass, like in many other chalcogenide glasses affected by rare earth doping. The nature of this effect was explained in terms of positron trapping reduction model as competitive contribution of changed occupancy sites in Ga-modified glassy matrix available for rare earth ions and annihilating positrons.
关键词： Chalcohalide glass,Positron trapping reduction,Rare earth doping,Photoluminescence
更新于2025-09-23 15:23:52
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Photoemission and thermoluminescence characteristics of Dy3+-doped zinc sodium bismuth borate glasses
摘要： The present study reports preparation and characterization of Dy3+-doped PbO free alkali-heavy-metal-borate glasses for luminescent applications. The amorphous nature of the glasses and the presence of various structural groups like BiO6, BO3 and BO4 were confirmed through XRD and FTIR measurements. The Oscillator strength of Dy3+ absorption transitions as well as the bond formed with the O2- ion in the glass network were determined using the absorption spectra. Radiative parameters extracted from Judd-Ofelt theory proved the degree of suitability of prepared glasses for lasing applications. The photoluminescence spectra exhibited the emission characteristics of Dy3+ ions and used to calculate the branching ratio, stimulated emission cross-section and radiative lifetime. Metastable lifetimes of Dy3+ ions were obtained through exponential fitting of respective decay profiles. The luminescence quenching phenomena was reasoned using Inokuti-Hirayama (I-H) model. The optical gain and quantum efficiency values clearly suggested Dy3+ doping at 0.3 mol% was optimum for 587 nm lasing action. Further, CIE chromaticity plot indicated the possible applications in solid state lighting devices. The thermoluminescence glow curves of 0.3 mol% Dy3+-doped glasses were considered for gamma irradiation and kinetic parameters of the same were evaluated using Computerized Glow Curve Deconvolution (CGCD) technique.
关键词： luminescence,kinetic order,Rare earth,Judd-Ofelt parameter,lifetime
更新于2025-09-23 15:23:52
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Preparation and Enhancement of Luminescent Intensity of New Rare Earth Molybdate NaLa(MoO4)2:Eu3+ Phosphors
摘要： Novel red-emitting rare earth molybdate phosphors NaLa(MoO4)2:Eu3+ have been successfully synthesized by sol-gel method assisted by microwave. The as-synthesized samples were characterized by means of Fourier transform infrared spectroscopy, X-ray diffraction and Fluorescence spectrophotometer, respectively. The results show that the target product NaLa(MoO4)2:Eu3+ have been synthesized by calcining precursor at 800 oC. The obtained samples belong to tetragonal Scheelite-structure and I41/a space group. The excitation spectrum of NaLa(MoO4)2:Eu3+ has a broad band in the range of 250-350 nm and the main peak is at 301 nm. The broad band can be ascribed to the charge transfer band of Mo-O and Eu-O. The sharp lines in 350-500 nm range are due to 4f-4f transitions of Eu3+. The emission spectrum contains a series of narrow peaks, with the main peak at 616 nm originated from the electric dipole transition of 5D0 → 7F2 of Eu3+. The appropriate doping amount of Bi3+ and flux NH4F can enhance luminescent intensity of the sample effectively.
关键词： Rare earth molybdate,Sol-gel method assisted by microwave,Red-emitting phosphors,NaLa(MoO4)2:Eu3+
更新于2025-09-23 15:23:52
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Eu-Doped BaF2 Nanoparticles for Bioimaging Applications
摘要： Pure Eu3+ ion doped BaF2 nanoparticles with tunable properties or property combinations are accessible via an ionic liquid-assisted solvothermal method. Structural parameters such as cell parameters, lattice strain and especially morphology are judiciously tuned with calcination temperatures. For example, tensile strain is observed in samples calcined up to 400oC, however compressive strain appears in samples calcined at 600oC and beyond. Larger surface area up to the sample calcined at 400oC and observation of layer structure at higher calcinations temperature (650oC and beyond) have been rationalized based on secondary nucleation. 3-dimensional island-like morphology with step-like layer structure caused by secondary nucleation and self-assembly are visualized and explained by Scanning Electron Microscope analysis. Moreover, emission intensity, decay time, quantum yield and Judd-Ofelt parameter of the Eu3+ ions increase systematically with calcinations temperature to a maximum at 400oC, above which they decrease and finally vanish at 800oC. Our results suggest that, smaller sized nanoparticles with 3-dimensional island-like structures, generated due to secondary nucleation at higher calcinations temperature may cause the increase of surface defects and subsequent luminescence quenching. To the best of our knowledge, the interplay between calcinations and secondary nucleation followed by drastic changes in the luminescence properties is new and previously unreported for the nanopowders. In addition, to improve the dispersibility, as-prepared nanoparticles are coated with silica and solubility of nanoparticles is measured in different solvents so that it can be useful for bio-imaging applications also.
关键词： calcination,photoluminescence,rare-earth ion,secondary nucleation,nanoparticles
更新于2025-09-23 15:23:52
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Colloidal Rare Earth Vanadate Single Crystalline Particles as Ratiometric Luminescent Thermometers
摘要： Thulium/ytterbium-doped yttrium vanadate particles provide ratiometric thermal response as both colloids and powders via downshift or upconversion emissions. Here, we synthesized yttrium vanadates by controlled colloidal conversion of hydroxycarbonate precursors. A protected annealing process yielded single crystalline and readily dispersible particles that were manipulated individually by optical tweezers in water. Because individual particles displayed detectable emissions, this system has potential applications as a single-particle luminescent temperature sensor. Excitation on Yb3+ sensitizers (λexc=980 nm) or at vanadate groups (λexc=300 nm) resulted in Tm3+ emissions that effectively correlated with the temperature of the sample from 288 to 473 K with high relative thermal sensitivity (0.8-2.2% K-1), one of the highest reported for vanadate nanocrystals so far. Different pairs of Tm3+ transitions afford a ratiometric thermal response, which fitted common sensing requirements such as large [3F2,3→3H6 (λ=700 nm)/1G4→3H6 (λ=475 nm)] or small [3F2,3→3H6 (λ=700 nm)/1G4→3F4 (λ=650 nm)] spectral gaps, and emission wavelengths at the first near infrared biological window [3F2,3→3F4 (λ=700 nm)/3H4→3H6 (λ=800 nm)]. Our findings open new perspectives for the use of luminescent nanothermometers with controllable spatial localization, which is a remarkably interesting prospect to investigate microscopically-localized events related to changes in temperature.
关键词： Luminescence,Thermometry,Nanoparticles,Thermal Sensors,Vanadates,Optical Trapping,Rare Earth
更新于2025-09-23 15:23:52
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Luminescent sensing film based on sulfosalicylic acid modified Tb(III)-doped yttrium hydroxide nanosheets
摘要： Sulfosalicylic acid (SSA) was used as an intercalation agent and an excellent antenna to synthesize layered rare-earth hydroxide (LRH) materials and directly obtain SSA-modified terbium-doped ytterbium hydroxide nanosheets by mechanical exfoliation. The crystal structure and morphologies of the LRHs and nanosheets were determined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The particle size and zeta potential of the prepared nanosheets were also analyzed. The as-prepared nanosheets exhibited excellent luminescent properties. The positively charged nanosheets were electrophoretically deposited on a conductive glass to form a thin film. The luminescence of this thin film can be quenched by chromate (CrO4^2-) and bilirubin (BR), which shows good sensing properties. The quenching mechanism of the sensing film by CrO4^2- and BR was discussed based on the spectra and structure of the film.
关键词： chromate (CrO4^2-),thin-film sensor,nanosheets,bilirubin (BR),rare-earth hydroxide
更新于2025-09-23 15:22:29
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ENHANCED STRUCTURAL AND ELECTRICAL PROPERTIES OF LEAD-FREE Y-DOPED (K, Na) NbO3 THIN FILMS
摘要： Yttrium- doped KNN thin films were grown on Si substrates using the sol-gel technique. The profound effects of Yttrium with different content element (mol % = 0, 0.1, 0.3, 0.5, 0.7 and 0.9) on the structural and electrical properties of KNN films were analyzed. The doped samples demonstrated a mainly uniform and homogenous microstructure with grain size less than 100 nm. The existence of Y Kα line shown in EDX spectrum confirmed the presence of Y-dopant in KNN based-compound. Small shift position of the Raman peaks indicated that Y incorporated on the interstitial A-site while broaden FWHM ascribed that Y preferably enters B-site lattice at high dopant concentration. The enhanced electrical resistivity at 0.5 mol % Y suggested that more conduction electrons were formed in KNN lattice structure.
关键词： doped,rare-earth,KNN,thin film,yttrium
更新于2025-09-23 15:22:29
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Influence of Sm2O3 Ion Concentration on Structural and Thermal Modification of TeO2-Na2O Glasses
摘要： The effect of Sm+3 ions concentration doped TeO2-Na2O glasses on structural and thermal parameters have been discussed. Glass samples with molar composition (80-x) TeO2-20Na2O-xSm2O3 glasses (x=0, 0.3, 0.6, 1, 1.2, 1.5) are prepared by melt quenching technique. Crystallization temperature (Tc), melting temperature (Tm) and glass transition temperature (Tg) are measured by using differential thermal analysis (DTA), it is found that the stability factor (ΔT) increases from (58.5-97.8) oC with the increasing of Sm2O3. The amorphous phase nature of the glass samples are observed by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectrometer are applied to study the structural properties of the glass samples. Values of density (ρ), molar volume (VM), and ionic packing density (Vt) were calculated for each of the glass compositions. The effect of the Sm2O3 on the glass structure have been investigated by using FTIR and Raman spectroscopies, the FTIR spectra are characterized by a band of 637 cm-1 for the telluride glass, high frequency peak at 668 cm-1 presented by Raman spectra which indicates that these glasses network are basically consists of TeO4 and TeO3/TeO3+1 structural units. The spectra of Raman shows the presence of Sm-O bond, Na-O bond, Te-O-Te bridging configurations, vibrations of Te-O-Te bonds and stretching modes of non-bonding oxygen found on the TeO3/TeO3+1 structural unit.
关键词： Telluride glass,FTIR,Raman spectra,Rare Earth,Glass transition
更新于2025-09-23 15:22:29
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Engineering Tunable Broadband Near-Infrared Emission in Transparent Rare-Earth Doped Nanocrystals-in-Glass Composites via a Bottom-Up Strategy
摘要： Applications of trivalent rare earth (RE3+)-doped light sources in solid-state laser technology, optical communications, biolabeling, and solar energy management have stimulated a growing demand for broadband emission with flexible tunability and high efficiency. Codoping is a conventional strategy for manipulating the photoluminescence of active RE3+ ions. However, energy transfer between sensitizers and activators usually induces nonradiative migration depletion that brings detrimental luminescent quenching. Here, a transparent framework is employed to assemble ordered RE3+-doped emitters to extend the emission spectral range by extracting photons from a variety of RE3+ ions with sequential energy gradient. To block migration-mediated depletion between different RE3+ ions, a nanoscopic heterogeneous architecture is constructed to spatially confine the RE3+ clusters via a 'nanocrystals-in-glass composite' (NGC) structure. This bottom-up strategy endows the obtained RE3+-doped NGC with high emission intensity (nearly one order of magnitude enhancement) and broadband near-infrared emission from 1300 to 1600 nm, which covers nearly the whole low-loss optical communication window. Most crucially, NGC is a versatile approach to design tunable broadband emission for the potential applications in high-performance photonic devices, which also provides new opportunities for engineering multifunctional materials by integration and manipulation of diverse functional building units in a nanoscopic region.
关键词： luminescence,rare earth doping,broadband emission,nanocrystals-in-glass composite,near-infrared emission
更新于2025-09-23 15:22:29
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Rare Earth Doping of Topological Insulators: A Brief Review of Thin Film and Heterostructure Systems
摘要： Magnetic topological insulators (MTIs) are a novel materials class in which a topologically nontrivial electronic band structure coexists with long-range ferromagnetic order. The ferromagnetic ground state can break time-reversal symmetry, opening a gap in the topological surface states whose size is dependent on the magnitude of the magnetic moment. Doping with rare earth ions is one way to introduce higher magnetic moments into a material, however, in Bi2Te3 bulk crystals, the solubility limit is only a few percent. Using molecular beam epitaxy for the growth of doped (Sb,Bi)2(Se,Te)3 TI thin films, high doping concentrations can be achieved while preserving their high crystalline quality. The growth, structural, electronic, and magnetic properties of Dy, Ho, and Gd doped TI thin films will be reviewed. Indeed, high magnetic moments can be introduced into the TIs, which are, however, not ferromagnetically ordered. By making use of interfacial effects, magnetic long-range order in Dy doped Bi2Te3, proximity-coupled to the MTI Cr:Sb2Te3, has been achieved. Clearly, engineered MTI heterostructures offer new possibilities that combine the advantageous properties of different layers, and thus provide an ideal materials platform enabling the observation new quantum effects at higher temperatures.
关键词： rare earth doping,MBE,topological insulators,heterostructure,bismuth telluride,antimony telluride
更新于2025-09-23 15:22:29