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The red persistent luminescence of (Sr,Ca)AlSiN3:Eu2+ and mechanism different to SrAl2O4:Eu2+,Dy3+
摘要： (Sr,Ca)AlSiN3:Eu2+ phosphors have been widely used in phosphor-converted white light emitting diodes. Herein, we reported the strong red persistent luminescence in (Sr,Ca)AlSiN3:Eu2+ under UV light excitation. The Sr0.8Ca0.2AlSiN3:0.15% Eu2+ shows the strongest red persistent luminescence with a peak emission wavelength at ~628 nm and a persistent time of ~9600 s at the 0.32 mcd/m2 threshold value. A new persistent luminescence mechanism, which is different to that of SrAl2O4:Eu2+,Dy3+, was proposed by comparing the thermoluminescence excitation spectrum (TLES) and the photoluminescence excitation spectrum (PLES) of Sr0.8Ca0.2AlSiN3:0.15% Eu2+. The electrons are directly excited from 4f ground states to the conduction band or from valence band to conduction band in (Sr,Ca)AlSiN3:Eu2+; while, in SrAl2O4:Eu2+,Dy3+, they are first excited to 5d level and then stimulated thermal process to the conduction band. The effect of Eu2+ concentration on red persistent luminescence in (Sr,Ca)AlSiN3:Eu2+ were discussed. The proposed mechanism of persistent luminescence can help us to design and find new persistent luminescence materials.
关键词： Persistent luminescence,SrAl2O4:Eu,Dy,Red emission,(Sr,Ca)AlSiN3:Eu,Persistent luminescence mechanism
更新于2025-09-23 15:23:52
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Controlling the Emergence and Shift Direction of Mechanochromic Luminescence Color of a Pyridine-Terminated Compound
摘要： In this study, mechanochromic luminescence was induced in a complex of mechano-inactive compounds. Dye/acid complexes containing the same p-conjugated backbones was prepared. While the luminophore showed blue and red shifts in photoluminescence spectra when combined with different acids by grinding, it exhibited slight mechanoresponsiveness itself. Also, compounds with similar molecular backbones to the dye/acid complex were synthesized to clarify the color change mechanism. The compounds showed both blue and red shifts in photoluminescence and diffuse reflectance spectra upon grinding, indicating that mechanochromic luminescence in the hydrogen-bonded complex is like its monomeric analogue and that aggregation structure plays an important role in the mechanoresponsive behavior rather than p-conjugated structure. We showed that mechanoinduced color change can be induced by imitating mechanoresponsive compounds without synthetic modification.
关键词： Luminescence,Supramolecular chemistry,Aggregation
更新于2025-09-23 15:23:52
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Crystal Structure and Luminescence of a Novel Binuclear Zinc(II) Complex with Di-2-Pyridylamine And 4,4′-Sulfonyldibenzoate
摘要： A binuclear Zn(II) complex [Zn2(SDBA)2(DPA)2?2H2O] (1) (DPA = di-2-pyridylamine, H2SDBA = 4,4′-sulfonyldibenzoic acid) is synthesized and characterized using single crystal X-ray diffraction, IR spectroscopy, and elemental analysis. The single crystal X-ray diffraction analysis reveals that complex 1 is a binuclear zinc(II) complex. The binuclear molecules are further connected by three types of N–H?O, C–H?O, and O–H?O hydrogen bonds, generating a three-dimensional supramolecular structure. Meanwhile, S–O?π interactions further consolidate the three-dimensional supramolecular framework of 1. In addition, the thermal stability and luminescent properties of the title complex are briefly investigated. The luminescence measurements reveal that complex 1 exhibits fluorescent emission in the solid state at room temperature.
关键词： luminescence,4′-sulfonyldibenzoic acid,crystal structure,4,Zn(II) complex,di-2-pyridylamine
更新于2025-09-23 15:23:52
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Smartphone-based apparatus for measuring upconversion luminescence lifetimes
摘要： Luminescence lifetime detection plays an important role in time-resolved detection and research. However, the traditional instruments always require expensive detectors such as time-correlated single photon counter or streak camera. Herein, a low-cost and miniaturized apparatus for measuring upconversion luminescence lifetimes was developed by using a smartphone equipped with a 980 nm CW laser and a motor. When the motor was driving the sample circling at a high linear velocity, the excited sample would emit a luminescence arc, which could be photographed by the phone camera. The rotating rate could be measured by a tuner APP and then used for transferring arc length to delay times. By analyzing the grayscale distribution of the luminescence arc, the luminescence decay curve was obtained, which was then used for exponential fit and calculating lifetimes. The whole system was not only remarkably cheaper but also more miniaturized than traditional instruments for measuring luminescence lifetimes, indicating the promising applications in point of care testing for time-resolved luminescence detection for bioanalysis and disease diagnosis.
关键词： Lanthanide upconversion,Luminescence lifetime,Time-resolved,Motor,Smartphone
更新于2025-09-23 15:23:52
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Effects of Mg2+/Si4+ doping on luminescence of Y3Al5O12:Ce3+ phosphors
摘要： A series of Mg2+/Si4+ codoped Y3Al5O12:Ce3+ phosphors were synthesized by a sol-gel method. X-ray diffraction, scanning election microscope, energy dispersive spectroscopy and fluorescent spectrophotometer were used to characterize the synthesized phosphors. The influence of codoped Mg2+/Si4+ ions on luminescence of Y3Al5O12:Ce3+ was investigated. The X-ray diffraction, scanning election microscope and energy dispersive spectroscopy results indicate that Ce3+, Mg2+ and Si4+ substitute Y3+ site, in the tetrahedral site and the substitution has no obvious influence on the phase and microstructure. And the Mg2+/Si4+ substitution leads to the red shift of emission band and the decrease of emission intensity.
关键词： Mg2+/Si4+ codoping,Luminescence,Y3Al5O12:Ce3+
更新于2025-09-23 15:23:52
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Electron-phonon interactions in subband excited photoluminescence of hexagonal boron nitride
摘要： The h-BN microcrystalline powder with carbon and oxygen impurities have been studied at 83 and 296 K using Raman and photoluminescence (PL) spectroscopies. The observed blue shift of Raman peaks with temperature decreasing have been discussed allowing for the enhanced role of the optical vibrational modes. Two series of phonon replicas in PL emission spectra with a zero-phonon line at 4.08 eV have been registered under 4.28 eV excitation. The energy levels model of the impurity (CN-ON)-complex responsible for observe luminescence was proposed. It was shown that the optically active center retains its electroneutrality in the processes of radiative recombination under subband (in 4.28 eV) or band-to-band excitation. Possible mechanisms of electron-phonon scattering and phonon replicas forming under subband excitation of (CN-ON)-complex were analyzed. It was substantiated that the longitudinal optical (?ωLO = 174 meV) and transverse acoustic (?ωTA = 60 meV) phonons at the middle points of high symmetry in the first Brillouin zone participate in the processes of intravalley (M- and Κ-scattering) and intervalley (Κ → Μ)-scattering, respectively.
关键词： ultraviolet luminescence,intravalley scattering,point defect,intervalley scattering,phonon replicas,h-BN,carbon-oxygen complex
更新于2025-09-23 15:23:52
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Photocatalytic Activity of ZnO Nanopowders: The role of production techniques in the formation of structural defects
摘要： The effect of the type of structural defect in zinc oxide on its photocatalytic properties was studied for phenol photodegradation under UV-irradiation. It was shown that the use of different types of precursors (zinc oxalate and zinc hydroxide) for the production of zinc oxide leads to the formation of a material with the same phase composition and equal energy of the forbidden band, but different photocatalytic activities. Simultaneously, the peculiarities of the luminescence and electron spin resonance spectra indicate the formation of different types of defects in the structure of the material, namely, oxygen vacancies (Vo) in the anionic and zinc vacancies (VZn) in the cationic sublattices of zinc oxide synthesised from the zinc oxalate and hydroxide, respectively. Also, the different characteristics of the luminescence decays reveal the different recombination paths for the free charge carriers in the systems synthesised from the different precursors. The different times of the luminescence decay also confirmed the different methods of recombination of free charge carriers in systems synthesised from different precursors. It was shown that the appearance of defects in the cationic sublattice leads to a decrease in the photocatalytic activity of the material relative to phenol degradation.
关键词： vacancies,luminescence.,Photocatalytic activity,structure defects,ZnO
更新于2025-09-23 15:23:52
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Temperature dependence of luminescence properties in Li2WO4 single crystal grown by Bridgman method
摘要： Transparent Li2WO4 single crystal was grown by vertical Bridgman method. The phase identification, Fourier transform infrared spectra, thermal behavior, and optical transmission spectra of Li2WO4 crystal had been studied in detail. The luminescence properties as a function of temperature were investigated systematically. The transmissivity of as-polished crystal samples with the thickness of 2.0 mm, 4.0 mm, and 6.0 mm reached 85–89%, 81–85%, and 78–81% in 400–800 nm wavelength range, respectively. Li2WO4 crystal has wide luminescence peaks around 626 nm, 574 nm, and 543 nm at the ambient temperature of 30 K, 50 K, and 75 K, respectively. The luminescence peaks are ascribed to the intrinsic luminescence emission of tetrahedral [WO4]2-. The emission line width presents an obvious broadening with the increasing temperature. The maximal luminescence intensity increases with the ambient temperatures cooling down. The luminescence decay times monotonically decrease with the temperature increasing in temperature range of 30–75 K. The decay times at 30 K, 50 K, and 75 K correspond to 97.92 m s, 30.16 m s, and 1.97 m s, respectively, while maintain a constant around 1.80 m s in 75–300 K.
关键词： Bridgman method,Crystal growth,Li2WO4,Luminescence
更新于2025-09-23 15:23:52
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One-pot green synthesis of highly luminescent silicon nanoparticles using Citrus limon (L.) and their applications in luminescent cell imaging and antimicrobial efficacy
摘要： Strongly luminescent and water dispersible silicon nanoparticles were synthesised by one-pot synthesis from venyl-trimethoxy-silane and (3-aminopropyl)-triethoxy-silane using both chemical and green reducing agents, sodium ascorbate and Citrus limon (L.) respectively. Unlike sodium ascorbate, the reduction using lemon extracts produces smaller nanoparticles with average size of 20 and 57 nm. The antimicrobial e?cacy of the nanoparticles is examined against various microorganisms and is noted that these particles possessed antibacterial property if used in concentrations above the threshold value of 1.5 μg/ml. In addition, these silicon nanoparticles emit intense blue-green emission which is successfully utilised for the luminescent cell imaging of human white blood cells and mice epithelial cells.
关键词： Luminescence,Citrus limon (L.),Silane,Silicon nanoparticle,Cell imaging.
更新于2025-09-23 15:23:52
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Multifunctional nanoclusters of NaYF4:Yb3+,Er3+ upconversion nanoparticle and gold nanorod for simultaneous imaging and targeted chemotherapy of bladder cancer
摘要： This paper reports successful synthesis of multifunctional nanoclusters of upconversion nanoparticle (UCNP) and gold nanorod (AuNR) through a PEGylation process. UCNPs emit visible luminescence under near-infrared excitation, producing high-contrast images with no background fluorescence. When coupled with AuNRs, the resulting UCNP-AuNR multifunctional nanoclusters are capable of simultaneous detection and treatment of bladder cancer. These UCNP-AuNR nanoclusters are further functionalized with antibodies to epidermal growth factor receptor (EGFR) to target bladder cancer cells known to overexpress EGFRs. This paper demonstrates, for the first time, efficient targeting of bladder cancer cells with UCNP-AuNR nanoclusters. In addition to high-contrast imaging and consequently high sensitivity detection of bladder cancer cells, highly selective optoporation-assisted chemotherapy was accomplished using a dosage of chemotherapy agent significantly lower than any previous reports, within a clinically relevant incubation time window. These results are highly relevant to the eventual human application in which the nanoclusters and chemotherapy drugs will be directly instilled in bladder via urinary catheter.
关键词： Luminescence upconversion,Surface Plasmon,Bladder Cancer,Gold Nanorod,Optoporation
更新于2025-09-23 15:23:52