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Effect of Hf <sup>4+</sup> doping on structure and enhancement of upconversion luminescence in Yb:Tm:LiNbO <sub/>3</sub> crystals
摘要： A series of Yb:Tm:LiNbO3 crystals doped with x mol% Hf4+ ions (x = 2, 4, and 6) were grown by the Czochralski method. The dopant occupancy and defect structure of Hf:Yb:Tm:LiNbO3 crystals were investigated by x-ray diffraction and infrared transmission spectra. The influence of Hf4+ ions concentration on UV–VIS–NIR absorption spectra of Hf:Yb:Tm:LiNbO3 crystals was discussed. The upconversion luminescence of Hf:Yb:Tm:LiNbO3 crystals was obtained under 980 nm excitation. Strong emissions were observed at 475 nm in the blue wavelength range and 651 nm in the red wavelength range. Remarkably, enhancement of the red and blue upconversion luminescence was achieved by tridoping Hf4+ ions.
关键词： crystal structure,Hf:Yb:Tm:LiNbO3 crystals,upconversion luminescence
更新于2025-09-09 09:28:46
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Investigation of mid-IR luminescence properties in Dy3+/Tm3+-codoped LaF3 single crystals
摘要： The spectroscopic characteristics of a series of Dy3+/Tm3+-codoped LaF3 single crystals have been studied for mid-IR emissions through Dy3+:6H13/2 → 6H15/2 transition. Optimal mid-IR emission was achieved in 3 at% Tm3+ and 2 at% Dy3+ co-doped LaF3 sample under the excitation of 790 nm. Its emission cross section was calculated to be 2.56×10-21 cm2 at the peak wavelength (2840 nm) with a FWHM of 270 nm, and the fluorescence lifetime was 3.694 ms. The fact of intense 2.84 μm emission was achieved by 790 nm pumping proves the effective energy transfer from Tm3+ to Dy3+ ions. The possible energy transfer routes were analyzed in detail, and the microscopic transfer constants were also estimated based on the phonon-assisted energy transfer theory. As a result, Dy3+/Tm3+-codoped LaF3 single crystal can be a potential medium for mid-IR lasers.
关键词： microscopic transfer constant,Dy3+/Tm3+:LaF3,sensitization mechanism,mid-IR luminescence
更新于2025-09-09 09:28:46
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Tunable luminescence modulation and warm light emission of Zn-MOF (4,4′-bipyridyl and zinc acetate) doped with Eu3+ and Tb3+
摘要： Herein, we describe the synthesis and doping of Zn-MOF (4,4’-bipyridyl and zinc acetate), crystallographic structure, optical properties of heteronuclear coordination polymers with emission in the visible (Eu3+/Tb3+ and Zn-MOF). The MOF presents a linear structure in the form of a nanotube. Density functional theory (DFT) and time dependent-DFT calculations were performed on the ground and excited states of Zn-MOF to provide insight of geometries, frontier molecular orbitals, and singlet and triplet state energies of the polymer. The metal-organic framework was doped with Eu3+ or Tb3+ in different proportions (Eu0.5-nTbn@Zn-MOF, when n= 0.00, 0.05, 0.10, 0.15, …, 0.5). The doped Zn-MOFs exhibit the typical red and green emission corresponding to Eu3+ and Tb3+ ions, respectively, energy transfer from MOF to metal ions takes place (“antenna effect”). It is noteworthy that the emission color of the lanthanides doped Zn-MOFs changes from red to orange-yellow-green depending on the proportion between Eu3+ and Tb3+. These compounds presented a τ ranging from 1.29 to 1.62 and 1.06-1.56 ms for Eu3+ and Tb3+, respectively, and the corresponding absolute quantum yields values range from 38-61%.
关键词： Lanthanides,doped MOF,luminescence,antenna effect
更新于2025-09-09 09:28:46
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Dinuclear N-heterocyclic carbene silver complexes: Synthesis, luminescence and catalytic studies
摘要： A new dibenzimidazole compound (1) and three dibenzimidazolium salts (2a-2c) were prepared. Reactions of these salts with silver(I) oxide in methanol led to dinuclear N-heterocyclic carbene silver complexes (3a-3c). All of the compounds were characterized by 1H NMR, 13C NMR and elemental analyses. Molecular weights of the silver complexes were confirmed by MALDI-TOF mass spectrometry. Preliminary catalytic studies using all the silver complexes were performed on three-component coupling reaction of p-formaldehyde, piperidine and phenylacetylene. Complexes 3a and 3c exhibited good catalytic activities under neat conditions. The silver complexes showed luminescence properties in CH3CN at room temperature.
关键词： luminescence,coupling reaction,silver,N-heterocyclic carbene
更新于2025-09-09 09:28:46
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Open-source sensor for measuring oxygen partial pressures below 100 microbars
摘要： The ability to measure partial pressures of oxygen below 100 microbars and nanomolar dissolved oxygen concentrations in in situ laboratory systems benefits many fields including microbiology, geobiology, oceanography, chemistry, and materials science. Here, we present an easily constructible open-source design for a networked luminescence lifetime measurement system for in situ measurements in arbitrary laboratory containers. The system is well suited for measuring oxygen partial pressures in the 0–100 μbar range, with the maximum potentially usable upper range limit at around 10 mbar, depending on experimental conditions. The sensor has a limited drift and its detectability limit for oxygen is at 0.02 μbar for short timescale measurements. Each sensor can connect to a Wi-Fi network and send the logged data either over the Internet or to a local server, enabling a large number of parallel unattended experiments. Designs are also provided for attaching the sensor to various commercially available containers used in laboratories. The design files are released under an open source license, which enables other laboratories to build, customize, and use these sensors.
关键词： in situ measurements,luminescence lifetime,oxygen sensor,trace oxygen,open-source
更新于2025-09-09 09:28:46
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Roman traces in Germania magna: New thermoluminescence and pIRIR <sub/>290</sub> data from a lime kiln at Bergisch Gladbach, Germany
摘要： The applicability of a post-infrared infrared stimulated luminescence (pIRIR290) protocol and two different thermoluminescence (TL) protocols—a single aliquot regeneration (SAR) and a multiple aliquot additive dose (MAAD)—was tested on six polymineral fine-grain (4–11 μm) samples extracted from the wall remains of a Roman lime kiln and a Roman roof tile. These remains had been excavated close to Bergisch Gladbach, which was at that time part of Germania magna. For the pIRIR290 measurements, no dependence of De on first-stimulation temperature was detectable, and the standard first stimulation temperature at 50°C was adopted. Fading tests and dose-recovery tests were made for all samples. Background subtracted glow curves were recorded up to 480°C for TL after a preheat of 220°C for 120 s. A-values were determined for all TL and pIRIR measurements. The results for all three protocols were fairly consistent, and TL and pIRIR290 protocols are shown to be suitable to estimate reliable equivalent doses for the fired kiln walls. The resulting ages are in agreement with the expected time range—Roman Iron Age—and with independent age control provided by radiocarbon ages of animal bones and charcoal from the firing chamber.
关键词： pIRIR290,GERMANIA MAGNA,THERMOLUMINESCENCE,POLYMINERAL,ROMAN LIME KILN,FINE GRAIN,LUMINESCENCE DATING
更新于2025-09-09 09:28:46
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Future prospects of fluoride based upconversion nanoparticles for emerging applications in biomedical and energy harvesting
摘要： Rare earth doped/codoped phosphors have been extensively studied for different types of applications based on their intense luminescence features. For this, researchers have tried to choose the inorganic host matrices having both a low phonon cut-off frequency and a high refractive index. Many articles have been published on oxide based phosphor materials, but due to their high cut-off phonon frequency, use of these materials is restricted for optical based applications. This is why additional research has been carried out on fluoride based host materials because of their low phonon frequencies, low composition degradation, and high quantum efficiency. In this paper, the authors review the rare earth fluoride based host nano- and micromaterials for different applications and discuss possible mechanisms.
关键词： biomedical applications,fluoride based upconversion nanoparticles,energy harvesting,luminescence,rare earth doped phosphors
更新于2025-09-09 09:28:46
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Cr3+ Doped Al2O3 Obtained by Non-Hydrolytic Sol-Gel Methodology
摘要： This paper reports the synthesis and characterization of Cr3+-doped alumina by the sol-gel non-hydrolytic methodology. The resulting sample was treated at different temperatures. X-ray diffraction revealed that the ruby phase emerged in the sample treated at 1100 oC, which was later confirmed by absorption bands correspondent to Cr3+ ions allowed transitions at 4A2 → 4T1, 4T2, and forbidden at 4A2 → 2T1, 2E, observed by diffuse reflectance UV-Vis. The luminescence spectroscopy showed the intensity band at 694 nm in red region, characterized of the Cr3+ ion. The peaks at 702 and 705 nm correspond to N1 and N2 lines, respectively, which arose from the second and fourth nearest-neighbor exchange-coupled pairs of chromium(III) ion, respectively, ascribed to high chromium(III) concentration. The Cr3+ cluster formation was observed in electron paramagnetic resonance signal as discussed in this work. Nuclear magnetic resonance evidenced that the 27Al symmetry changed in the samples treated between 900 and 1100 oC.
关键词： EPR,NMR,sol-gel,luminescence,ruby
更新于2025-09-09 09:28:46
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Enhanced Red Emission in Er <sup>3+</sup> -Sensitized NaLuF <sub/>4</sub> Upconversion Crystals via Energy Trapping
摘要： Luminescence e?ciency of trivalent lanthanide-doped upconversion (UC) materials is signi?cantly limited by luminescence concentration quenching. In this work, red UC emission is dramatically enhanced in Er3+-sensitized NaLuF4 UC crystals through energy trapping under multiple excitation wavelengths. Cross-relaxation quenching and the energy migration to internal lattice defects are simultaneously suppressed by con?ning the excitation energy in the Er3+ activator after introducing the Tm3+ or Ho3+ energy trapping center. The enhanced red UC emission (Er3+: 660 nm) mainly comes from the e?ective excitation energy con?nement by Tm3+ and Ho3+ trapping centers through an easy energy transfer between Er3+ and Tm3+/Ho3+: 4I11/2 (Er3+) → 3H5 (Tm3+) → 4I13/2 (Er3+) and 4I11/2 (Er3+) → 5I6 (Ho3+) → 4I13/2 (Er3+). It is found that the con?ning e?ciency of excitation energy in Er3+-sensitized NaLuF4 crystals is higher than that in Yb3+/Er3+ cosensitized NaLuF4 crystals, and the luminescence e?ciency of Er3+-sensitized NaLuF4 crystals is much higher than that of Er3+-based host sensitization UC crystals (NaErF4). Moreover, Er3+-sensitized UC particles can be e?ciently excited by three di?erent wavelengths (808, 980, and 1532 nm), indicating huge advantages for applications in bioimaging, anticounterfeiting, and solar cells.
关键词： energy trapping,anticounterfeiting,NaLuF4,Er3+-sensitized,solar cells,bioimaging,upconversion,luminescence
更新于2025-09-09 09:28:46
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Rationalizing and Controlling the Surface Structure and Electronic Passivation of Cesium Lead Halide Nanocrystals
摘要： Colloidal lead halide perovskite nanocrystals (NCs) have recently emerged as versatile photonic sources. Their processing and luminescent properties are challenged by the lability of their surfaces, i.e. the interface of the NC core and the ligand shell. On the example of CsPbBr3 NCs, we model the nanocrystal surface structure and its effect on the emergence of trap states using density functional theory. We rationalize the typical observation of a degraded luminescence upon aging or the luminescence recovery upon post-synthesis surface treatments. The conclusions are corroborated by the elemental analysis. We then propose a strategy for healing the surface trap states and for improving the colloidal stability by the combined treatment with didodecyldimethyl ammonium bromide and lead bromide and validate this approach experimentally. This simple procedure results in robust colloids, which are both highly pure and exhibit high photoluminescence quantum yields of up to 95-98%, retained even after 3-4 rounds of washing.
关键词： trap states,didodecyldimethyl ammonium bromide,luminescence recovery,photoluminescence quantum yields,lead bromide,CsPbBr3 NCs,density functional theory,Colloidal lead halide perovskite nanocrystals,surface structure
更新于2025-09-09 09:28:46