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[IEEE 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Saint Petersburg, Russia (2018.10.22-2018.10.23)] 2018 IEEE International Conference on Electrical Engineering and Photonics (EExPolytech) - Study of Oxyfluoride Glasses with Silver Molecular Clusters for Application in Sensoric and Optoelectronics
摘要： Temperature sensitivity of Oxyfluoride glasses with molecular silver clusters and samarium ions were studied. The experimental procedure for obtaining luminescence spectra at various temperatures is described. The perspective of using oxyfluoride glasses in fiber-optic temperature sensors is considered.
关键词： sensitive element,luminescence,Fiber-optical temperature sensor,oxyfluoride glass,spectrum,molecular clusters of silver
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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Investigation on electronic structure and luminescence mechanism of CaF2:Eu3+ from first principles calculations
摘要： In this work, we present the results of theoretical calculations based on the density functional theory (DFT) of structural, electronic and optical properties of CaF2 crystal doped with Eu3+ ion. This study covers both ground and excited states of considered material by ?xing spin magnetic moment 6μB and 4μB, respectively. The Eu3+ doping induces slight displacement of its nearest neighbors. The presence of Eu3+ ion is con?rmed by the calculated charge density and magnetic moment. Some electronic states belonging to 4f orbital are found in the forbidden energy region of CaF2 and the spin ?ipping of one 4f electron of Eu3+ caused by the excitation is demonstrated by means of the computed electronic properties. The absorption spectra of CaF2:Eu3+ is calculated and compared with that of pure CaF2. Finally, the possible mechanism of luminescence is proposed based on the obtained electronic and optical properties.
关键词： CaF2:Eu3+,First principles study,Electronic structure,Luminescence
更新于2025-09-23 15:22:29
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Enhanced NIR-NIR luminescence from CaWO4: Nd3+/Yb3+ phosphors by Li+ codoping for thermometry and optical heating
摘要： Rare earth ions doped luminescent materials have demonstrated their potentiality as sensitive thermometers with good accuracy and high spatial resolution. Nevertheless, low luminescence efficiency, especially at high temperature, still limits the development of this thermometry technique. Here, Nd3+/Yb3+ codoped CaWO4 phosphors were synthesized using high temperature solid-state method, and Li+ ions were introduced aiming to improve the near-infrared (NIR) emissions from Nd3+ in the spectral range of 725-950 nm. The influence of Li+ codoping on the structure and NIR luminescence in CaWO4: Nd3+/Yb3+ when excited by a 980 nm laser diode was investigated. NIR-NIR emissions from Li+ codoped samples are successfully strengthened compared with that without Li+ ions, which is mainly attributed to the distortion of the crystal structure and the increase of crystalline size by Li+. The optical temperature sensing behavior of NIR luminescence from Nd3+ was studied based on fluorescence intensity ratio (FIR). Assisted by Li+ ions, the NIR-NIR emissions are observed to be effectively enhanced with the increment of temperature. And a new pair of thermally coupled levels in Nd3+ ions with excellent thermometry characteristics is explored, through which superior measurement sensitivity as well as accuracy could be achieved. In addition, light-induced temperature rise was realized in the phosphors, which makes CaWO4: Nd3+/Yb3+/Li+ excellent candidate for luminescence thermometry and optical heaters.
关键词： Li+ codoping,thermometry,Nd3+ ions,NIR luminescence
更新于2025-09-23 15:22:29
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Novel Ca20Al26Mg3Si3O68:Ce3+,Tb3+ phosphors: preferential site occupation, color-tunable luminescence and device application
摘要： A novel luminescence material of emitting color-tunable Ca20Al26Mg3Si3O68(denoted as CAMSO):Ce3+,Tb3+ phosphors have been synthesized via the high temperature solid-phase reaction process. The crystal cell structure, photoluminescence properties and application performance such as thermal stability and LED device performance of the phosphors were researched in detail. CAMSO:Ce3+,Tb3+ phosphors showed multi-color with the different concentration of Ce3+ and Tb3+ ions. Although the concentration of Ce3+ ions was settled and there was the existence of energy transfer from Ce3+ to Tb3+ ions, it was found that Ce3+ ions’ blue light emission intensity showed abnormal increasing with the increase of Tb3+ ions doping concentration. The irregular phenomenon was discussed in detail. The phosphor CAMSO:0.2Ce3+, 0.1Tb3+ photoluminescence emission intensity motivated by 374nm at 150oC retained about 81% of that measured at room temperature, which demonstrating the good thermal and color stability of the sample. In addition, the white LED lamps were fabricated through mixing the sample CAMSO:0.2Ce3+,0.2Tb3+ and the commercial phosphor CaAlSiN3:Eu2+ and their performance has been measured. The results show that this series of phosphors could be excellent candidates for the application of UV-excited w-LEDs.
关键词： thermal stability,abnormal luminescence,tunable color,multi-crystallographic sites
更新于2025-09-23 15:22:29
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Single-Step Synthesis and Optical Properties of Bimetallic Fe–Ag Nanoparticles
摘要： Bimetallic nanoparticles containing ferromagnetic iron (Fe) and plasmonic silver (Ag) are synthesized by one-step chemical reduction process. Structural and optical properties of nanoparticles are studied by transmission electron microscopy, X-ray diffraction technique, UV-Visible spectroscopy and photoluminescence measurement. Tunable optical properties with the variation of Ag percentage in the Fe–Ag nanoparticles are observed. Sharp absorption peak due to localized surface plasmon resonance (LSPR) is observed in the visible spectrum range for Fe–Ag nanoparticles which is absent in Fe nanoparticles. LSPR peak shows redshift due to variation in shape and size of the nanoparticles having higher Ag content. Enhanced photoluminescence in the bimetallic nanoparticles is attributed to the observed surface plasmon resonance.
关键词： Optical Properties,Nanostructured Materials,Luminescence,Chemical Synthesis
更新于2025-09-23 15:22:29
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Novel Luminescent Multilayer Films with Magnetic and Electronic Microenvironment
摘要： Luminescent multilayer thin films (MTFs) based on exfoliated magnetic layered double hydroxides (LDHs) with/without oppositely-charged montmorillonite (MMT) nanosheets were fabricated via layer-by-layer self-assembly method. In this work, we chose transition metal-bearing LDHs nanosheets to offer magnetic field for the chromophores. At the same time, the oppositely-charged nanosheets can provide additional electronic microenvironment (EME). As a result, both EME and magnetic field have remarkable influences on enhancing the luminescent lifetimes of chromophores, which suggests a new pathway to develop the novel light-emitting materials and optical devices.
关键词： Montmorillonite,Electronic Microenvironment,Magnetic Field,Layered Double Hydroxides,Luminescence
更新于2025-09-23 15:22:29
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Fabrication and Investigation of Two-Component Film of 2,5-Diphenyloxazole and Octafluoronaphthalene Exhibiting Tunable Blue/Bluish Violet Fluorescence Based on Low Vacuum Physical Vapor Deposition Method
摘要： Organic luminescent materials play an important role in the fields of light-emitting diodes and fluorescent imaging. Moreover, new synthetic approaches towards π-conjugated molecular systems with high fluorescence quantum efficiency are highly desired. Herein, different 2,5-diphenyloxazole-octafluoronaphthalene (DPO-OFN) films with tunable fluorescence have been prepared by Low Vacuum Physical Vapor Deposition (LVPVD) method. DPO-OFN films showed some changed properties, such as molecular vibration and fluorescence. All films exhibited blue/bluish violet fluorescence and showed blueshift, in comparison with pristine DPO. This work introduced a new method to fabricate two-component molecular materials with tunable blue/bluish violet luminescence properties and provided a new perspective to prepare organic luminescent film materials, layer film materials, cocrystal materials, and cocrystal film materials. Importantly, these materials have potential applications in the fields of next generation of photofunctional materials.
关键词： blue/bluish violet luminescence,organic luminescent materials,tunable fluorescence,two-component film,low vacuum physical vapor deposition
更新于2025-09-23 15:22:29
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Separation of Spectroscopically Uniform Nanographenes
摘要： Excitation-dependent photoluminescence (PL) is a well-known property of graphene quantum dots (GQDs). For the development of carbon-based photofunctional materials, GQDs possessing uniform PL properties are in high demand. A protocol has been established to separate spectroscopically uniform lipophilic GQD-1 a from a mixture of GQD-1 mainly composed of GQD-1 a and GQD-1 b. The mixture of GQD-1 was synthesized through the reaction of p-methoxybenzylamine with GQD-2 prepared from graphite by common oxidative exfoliation. Size-exclusion chromatography gave rise to GQD-1 a and GQD-1 b, with diameters of 19.8 and 4.9 nm, respectively. Large GQD-1 a showed that the PL was fairly independent of the excitation wavelengths, whereas the PL of small GQD-1 b was dependent on excitation. The excitation-dependent nature is most likely to be associated with the structures of sp2 domains on the graphene surfaces. The large sp2-conjugated surface of GQD-1 a is likely to possess well-developed and large sp2 domains, the band gaps of which do not significantly vary. The small sp2-conjugated surface of GQD-1 b produces small sp2-conjugated domains that generate band gaps differing with domain sizes.
关键词： photochemistry,luminescence,quantum dots,graphene,chromatographic separation
更新于2025-09-23 15:22:29
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Chiral Sensing Using Circularly Polarized Luminescence of Bis (phenanthroline dicarboxylic acid) Eu(III) Complex Induced by Allosteric-type Interaction with Amino Acid Molecules
摘要： [Eu(pda)2]- and [Eu(bda)2]- (pda = 1,10-phenanthroline-2,9-dicarboxylic acid; bda = 2,2’ bipyridine 5,5’-dicarboxylic acid) have an achiral D2d structure in crystals. These complexes exhibit circularly polarized luminescence (CPL) in water containing chiral amino acids. In this work, induced CPL of [Eu(pda)2]- and [Eu(bda)2]- in water solutions containing a mixture of D- and L- amino acids were examined. Plots of glum values of the induced CPL as a function of mol-fraction of L- and D- arginine reveal that [Eu(pda2]- favors homo-association ([Eu(pda)2]--(L-arginine)2 or [Eu(pda)2]--(D-arginine)2) over hetero-association {[Eu(pda)2]--(L-arginine)?(D-arginine)}. This suggests that association of an arginine molecule induces a structural change in [Eu(pda)2]- to promote chiral selective association to another arginine, i.e., homo-allosteric association. On the other hand, the system of [Eu(pda)2]- with histidine favors hetero-allosteric association over homo-association. No allosteric effect is recognized in CPL from [Eu(bda)2]-.
关键词： allosteric effect,amino acid,lanthanide complex,circularly polarized luminescence,chiral sensing
更新于2025-09-23 15:22:29