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Enhancement of Luminescence Intensity in Dy3+ Ions Doped YVO4 Nanomaterials by Ba2+ Ion Codoping and YVO4:2Dy/Fe3O4 Nanohybrid for Hyperthermia Application
摘要： The enhancement of the luminescence intensity of the Dy3+ by Ba2+ ions (at different concentrations) codoping into YVO4:2Dy nanoparticles at different annealing temperature of as-prepared, at 500 and 900°C were studied. The XRD study shows the strains are induced when dopant and codopant are incorporated into host matrix. XRD patterns of nanohybrids show the existence of two phases corresponding to YVO4:2Dy and Fe3O4 nanoparticles. TEM image of YVO4:2Dy nanoparticles were spherical shape whereas for YVO4:2Dy/Fe3O4 nanohybrids, the spherical particles are forming chain like structure due to the PEG molecule which binds both YVO4:2Dy and Fe3O4 during nanohybrids formation. Increase in absorption coefficient and decrease in lattice strain values are the major reasons for the enhancement of emission intensity in photoluminescent (PL). Lifetime studies also shows correlation between the calculated energy transfer and diffusion for indirect excitation which is also studied here. High quantum efficiency up to 45% can be achieved. YVO4:2Dy/Fe3O4 nanohybrids is found to achieve hyperthermia temperature 42°C in short time. This nanohybrids shows luminescence in the region of biological window indicating nanohybrids can be used as bioimaging probe. It also shows high viability up to 94% in HeLa cancer cells.
关键词： Vanadate nanoparticles,HeLa cell,Nanohybrids,Enhancement of luminescence,Hyperthermia
更新于2025-09-09 09:28:46
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Effect of Coordination Modes on the Tunable Luminescence of 1,10-Phenanthroline-Based Complexes
摘要： Two luminescent compounds [Zn(L)2](ClO4)2 (1) and [Na(L)(MeOH)(μ-ClO4)]n (2) are obtained from the reactions of 2,9-bis(carbomethoxy)-1,10-phenanthroline (L) with corresponding hydrated perchlorate salts in MeOH. Their crystal structures are determined by X-ray crystallography. 1 is a mononuclear 8-coordinate Zn2+ compound and 2 is a ?-bridged 1D polymer, where the ligand L exhibits di?erent coordination modes (carbonyl O vs methoxyl O coordination). Although the luminescence of these two compounds originates similarly from the ligand-centered π→π* transitions, it is interesting to note that their emissions are signi?cantly in?uenced by the di?erent coordination modes of L. The relationship between their structures and emission properties has been investigated in detail. The stability and energy di?erence between these two coordination modes in these two compounds are analyzed by Time-dependent density functional theory (TD-DFT) calculations.
关键词： sensor,luminescence,2,9-bis(carbomethoxy)-1,10-phenanthroline,different coordination modes
更新于2025-09-09 09:28:46
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Spectroscopic characterization of orthorhombic δ-BiB3O6 phase nonlinear single crystal doped with Pr3+ ions
摘要： The spectroscopic properties of 1at % Pr3+ doped δ-BiB3O6 (BIBO) single crystal were investigated. The absorption, emission and excitation spectra were studied at low (10 K) and at room temperature, with the emission and absorption spectra showing clear polarization dependence. The strongest observed luminescence band corresponds to the 1D2 → 3H4 transition at 610 nm. Energy levels of Pr3+ in δ-BIBO host were assigned on the basis of low temperature absorption and emission measurements. The number of crystal field levels derived implies that Pr3+ ions are located in one crystal site in the BIBO host. Decay time of the praseodymium 3P0 emission was unusually short and the 1D2 decay was non-exponential. The modified Judd-Ofelt intensity formalism was used to analyze the experimental data. The ?λ parameters, branching ratios and electric dipole transition probabilities were determined. The stimulated emission cross-sections σ for the 5D0 → 3HJ transitions were also evaluated in this system.
关键词： Pr3+ spectroscopic properties,Pr3+ luminescence,Pr3+ ions in borate hosts,δ-BiB3O6,Judd-Ofelt formalism
更新于2025-09-09 09:28:46
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UV Luminescence and Lasing in Ensembles of Zinc-Oxide Microcrystals with Copper
摘要： Microrod arrays of zinc oxide with copper have been grown by chemical vapor deposition on single-crystal sapphire substrates preliminarily covered with a nanoscale copper layer. The presence of copper (about 0.3%) in zinc-oxide microrods has been experimentally shown to increase the photoluminescence intensity of the ZnO microcrystal arrays, reduce the lasing threshold, and lead to a small (by ~2.5 nm) blue shift of the radiation intensity peak of the ZnO microcrystals. It is shown that the laser-radiation character depends on the morphology of the ZnO microrod arrays.
关键词： lasing,zinc-oxide microcrystals,UV luminescence,copper doping,chemical vapor deposition
更新于2025-09-09 09:28:46
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Two Zn(II) coordination polymers based on 5-substituted isophthalic acid: syntheses, crystal structures, luminescence sensing properties
摘要： Two new Zn(II) coordination polymers (CPs), {[Zn(L)(5-nip)]2·5.5H2O}n (1) and {[Zn(L)(5-mip)]·EtOH}n (2) [L = 1,3-bis(benzimidazol-1-yl)-2-propanol, 5-H2nip = 5-nitroisophthalic acid, 5-H2mip = 5-methyisophthalic acid] were solvothermally synthesized and characterized by elemental analyses, IR spectra, thermogravimetric analyses, and single-crystal X-ray diffraction. CP 1 possesses a 1D ladder-like chain structure and further packed into 2D supramolecular architectures by π-π stacking interactions. CP 2 exhibits a 2D 63 layer, which is finally extended into 3D supramolecular network via the weak C–H···O hydrogen bond interactions. CP 1 and CP 2 can be used as luminescent sensors for Hg2+ and Cr2O7 2- ions in water.
关键词： Znic(II),Bis(benzimidazole),Luminescence quenching,Supramolecular architecture,Coordination polymer
更新于2025-09-09 09:28:46
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Helicenic complexes of lanthanide: influence of f-element on the inter-system crossing efficiency and competition between luminescence and oxygen sensitization.
摘要： The coordination of a helicen functionalized bipyridine to various lanthanide complexes (Ln = Y, Eu, Yb, Gd) led to the formation of an isostructural series. The photophysical study indicated that non-emissive lanthanide act as heavy atoms strongly enhancing the singlet oxygen generation. We also demonstrated that sensitization of the f-f luminescence is in competition with singlet oxygen generation.
关键词： singlet oxygen generation,lanthanide,photodynamic therapy,luminescence,helicen
更新于2025-09-09 09:28:46
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Controlling the white phosphorescence ZnGa2O4 phosphors by surface defects
摘要： White phosphorescence that lasted ≈ 212 seconds, being the longest phosphorescence time reported so far for any Ga based material, has been observed in undoped ZnGa2O4 (ZGO) phosphors. The samples were synthesized by a simple combustion method by using two different Gallium precursors (Gallium nitrate and Gallium Acetylacetonate). According to the X-ray diffraction analysis, the samples prepared with the two different precursors presented the same single cubic phase. TEM images demonstrated that the ZGO phosphors made with both precursors are formed by nanoparticles with quasi-spherical shape, and they have nanoparticle sizes in the range of 17-43 nm. When excited with UV light (400 nm), these phosphors produced a broad blue-green-yellow luminescence. The blue band was associated to transitions from the Ga-O levels, while that of green-yellow band was attributed to radiative transitions from oxygen vacancies. Particularly, the sample synthesized with Gallium acetylacetone precursor presented the highest phosphorescent emission intensity and had a CIE coordinates of (x= 0.27, y= 0.33), which is close to that for pure white light (x=0.33, y=0.33). Since the ZGO presented a white phosphorescent emission without doping with rare earths, they could be good candidates for lighting or signaling applications.
关键词： White emission,Zinc-gallate,phosphorescence,Oxygen-vacancies,luminescence
更新于2025-09-09 09:28:46
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Er-doped antimonite Sb2O3?PbO?ZnO/ZnS glasses studied by low-temperature photoluminescence spectroscopy
摘要： Antimonite glasses Sb2O3?PbO?ZnO/ZnS doped with ErCl3 within the range of 0.25-1.0% were prepared and investigated by means of transmission, photoluminescence excitation and photoluminescence (PL) spectroscopy. In the studied glasses, the wavelength of 522 nm was found to be the most suitable for PL excitation of Er3+ ions doped in both the NIR and VIS spectral ranges. The PL spectra excited by wavelengths at 522 and/or 514.5 nm were measured at room and low temperatures (4 K) in the wavelength range of 400–1700 nm. Low-temperature PL spectroscopy allowed us to observe both the broad luminescence of the host glass centered at around 1050 nm and the narrow emissions caused by Er3+ ions. Special attention was given to the wavelengths where the broad-band luminescence of the host overlaps with 4f–4f transitions within Er3+ ions. A broad PL band of the host glass was observed together with a superimposed narrow emission band at 985 nm (4I11/2? 4I15/2) and a narrow absorption dip at about 970 nm (4I15/2? 4I11/2). This absorption dip is a direct experimental evidence of energy transfer from the electronic structure of the host glass to 4f states of doped-in Er3+ ions. The strongest PL band at 1530 nm, representing transition from the lowest excited manifold 4I13/2 to the ground state manifold 4I15/2 was measured at 300 K and 4 K. The broadening at elevated temperature occurs primarily in the high energy part of the spectrum due to thermal excitation of electrons within the 4I13/2 manifold.
关键词： photoluminescence excitation spectroscopy,broad-band luminescence,low-temperature photoluminescence spectroscopy,erbium,antimonite glasses
更新于2025-09-09 09:28:46
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Fine structure in high resolution 4f7?4f65d excitation and emission spectra of X-ray induced Eu2+ centers in LuPO4:Eu sintered ceramics
摘要： X-ray induced effects in LuPO4:Eu3+ sintered thermoluminescent material were investigated by absorption and photoluminescence measurements between 20-300 K. Evidence for Eu3+→Eu2+ conversion upon exposure to X-rays was obtained as narrow band blue Eu2+ photoluminescence was observed. The low temperature luminescence of Eu2+ ions in X-rayed LuPO4:Eu ceramics showed a unique fine structure with a sharp zero-phonon line at 425.8 nm and well-resolved vibronic structure. Excitation spectra of the Eu2+ luminescence revealed a rich structure in which individual 4f7→ 4f6(7FJ)5d1 zero-phonon lines accompanied by vibronic transitions were identified. A detailed analysis allowed an accurate calculation of the Eu3+-like 4f6(7FJ) core levels in the 4f65d1 excited configuration. The 4f6 core splitting is different from that of the 7FJ states for Eu3+ in LuPO4, providing evidence for the role of 4f6-5d interaction on the splitting of the 4f6 configuration. The unique luminescence of Eu2+ with a small Stokes shift and well-determined energies of 4f6(7FJ)5d1 excited states make LuPO4:Eu a model system for testing theoretical models which are presently developed to calculate and predict the energy level structure and Stokes shift of 4fn-4fn-15d1 transitions of lanthanides.
关键词： Eu2+ luminescence,LuPO4,zero-phonon line,high resolution spectroscopy,4f65d excited state
更新于2025-09-09 09:28:46
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Generating long chronologies for lacustrine sediments using luminescence dating: a 250,000 year record from Lake Tana, Ethiopia
摘要： The lakes of the eastern Africa Rift often contain great thicknesses of sediment that may provide continuous records of environmental change over decadal to million-year timescales. However interpretation of these changes is greatly compromised without a reliable chronology. Luminescence dating has not been used extensively in lacustrine settings; instead previous studies have often relied upon radiocarbon dating, using extrapolation beyond the upper limit of that technique, and employing opportunistic sampling of tephra and palaeomagnetic signatures where possible. This study from Lake Tana, Ethiopia, demonstrates that recent advances in luminescence methodology can provide long chronologies for lake sediments that are not dependent on the intermittent presence of dateable material, as is the case for radiocarbon and tephra-based methods. Specifically, this study generates luminescence ages that agree with independent chronology based on radiocarbon dating in the upper part of the core, and extends significantly beyond the range of radiocarbon dating to provide one of the longest independently dated lacustrine sediment records in eastern Africa, thus demonstrating the tremendous potential of luminescence for constructing lacustrine sediment chronologies over 100,000 year timescales.
关键词： OSL,Lacustrine sediments,Luminescence dating,Post-IR IRSL signal,Direct dating,Polymineral fine-grains,Palaeolimnology,Radiocarbon
更新于2025-09-09 09:28:46