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1.
Under a 980‐nm excitation, the up‐conversion (UC) spectra of LuNbO4:Yb3+,Tm3+ powders exhibited predominantly near‐infrared bands (~805 nm) of Tm3+ through an energy transfer process from Yb3+ to Tm3+. Regarding the down‐conversion (DC) luminescence of the powders, the photoluminescence excitation spectra consisted of a broad charge transfer band (270 nm) due to [NbO4]3? and sharp band (360 nm) of Tm3+, while the corresponding emission spectra exhibited a blue emission at 458 nm. Upon substitution of Ga3+ and Ta5+ for Lu3+ and Nb5+, respectively, both UC and DC luminescence properties were significantly enhanced. For the Ga3+ substitution, the increased emission intensity could be explained by the crystal field asymmetry surrounding the Tm3+ ions induced by the large difference in ionic radius between Ga3+ and Lu3+. For the Ta5+ substitution, we believe that an M′‐LuTaO4 substructure was formed in the host, which led to the formation of a TaO6 octahedral coordination instead of a NbO4 tetrahedral coordination. Consequently, the crystal symmetry of the local structure was modified, and thus the UC and DC luminescence properties were enhanced. The dual‐mode (UC and DC) luminescence demonstrates that LuNbO4:Yb3+,Tm3+ has a great potential in the fields of temperature sensing probes, anti‐counterfeiting, and bioapplications. 相似文献
2.
Frequency up‐conversion (UC) emission from the Nd3+‐Yb3+/Nd3+‐Yb3+‐Li+ co‐doped gadolinium oxide (Gd2O3) phosphors prepared by the solution combustion technique in the visible range have been studied by using 980 nm near infrared (NIR) laser diode excitation. The crystalline structure and formation of the cubic phase has been confirmed with the help of X‐ray diffraction (XRD) studies. XRD peak shifts have been found towards the lower diffraction angle side in the case of the Nd3+‐Yb3+‐Li+ co‐doped phosphors. Surface morphology and particle size information have been observed by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis. Down‐conversion emission study under 351 nm excitation in the visible region for the Nd3+‐Yb3+/Nd3+‐Yb3+‐Li+ co‐doped phosphors has been performed. The UC emission bands lying in the green and red region arising from the Nd3+ ions have been enhanced by ~260 times, ~113 times due to incorporation of Li+ ions in the Nd3+‐Yb3+ co‐doped phosphors. Photometric characterization has been done for the Nd3+‐Yb3+/Nd3+‐Yb3+‐Li+ co‐doped phosphors. The present study suggests the capability of the synthesized phosphors in near‐infrared (NIR) to visible upconverter and luminescent device applications. 相似文献
3.
Enhanced green emissions of Er3+/Yb3+ co‐doped Gd2(MoO4)3 by co‐excited up‐conversion processes
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Improving the emission from rare earth ions doped materials is of great importance to broaden their application in bio‐imaging, photovoltaics and temperature sensing. The green emissions of Gd2(MoO4)3:Er3+/Yb3+ powder upon co‐excitation with 980 and 808 nm lasers were investigated in this paper. Distinct enhancement of green emissions was observed compared with single laser excitation. Based on the energy level structure of Er3+, the enhancement mechanism was discussed. Moreover, the result of temperature‐dependent enhancement revealed that the enhancement factor reached its maximum (2.5) as the sample heated to 120°C, which is due to the competition of two major thermal effects acting in the co‐excited up‐conversion processes. In addition, the same enhancement of green emissions was also observed in Gd2(MoO4)3:Er3+ powder and NaYF4:Er3+/Yb3+ powder. 相似文献
4.
This paper focuses on an optical study of a Tb3+/Bi3+‐doped and Sm3+/La3+‐ doped Ca2Al2SiO7 phosphor synthesized using combustion methods. Here, Ca2Al2SiO7:Sm3+ showed a red emission band under visible light excitation but, when it co‐doped with La3+ ions, the emission intensity was further enhanced. Ca2Al2SiO7:Tb3+ shows the characteristic green emission band under near‐ultraviolet light excitation wavelengths, co‐doping with Bi3+ ions produced enhanced photoluminescence intensity with better colour tunable properties. The phosphor exhibited better phase purity and crystallinity, confirmed by X‐ray diffraction. Binding energies of Ca(2p), Al(2p), Si(2p), O(1s) were studied using X‐ray photoelectron spectroscopy. The reported phosphor may be a promising visible light excited red phosphor for light‐emitting diodes and energy conversion devices. 相似文献
5.
Spectral‐converting study of Ba9–3(m+n)/2ErmYbnY2Si6O24 (m = 0.005 – 0.2, n = 0 – 0.3) orthosilicate phosphors
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Optical materials composed of Ba9–3(m+n)/2ErmYbnY2Si6O24 (m = 0.005–0.2, n = 0–0.3) were prepared using a solid‐state reaction. The X‐ray diffraction patterns of the obtained phosphors were examined to index the peak positions. The photoluminescence (PL) excitation and emission spectra of the Er3+‐activated phosphors and the critical emission quenching as a function of Er3+ content in the Ba9–3m/2ErmY2Si6O24 structure were monitored. The spectral conversion properties of Er3+ and Er3+–Yb3+ ions doped in Ba9Y2Si6O24 phosphors were elucidated under diode‐laser irradiation at 980 nm. Up‐conversion emission spectra and the dependence of the emission intensity on pump power for the Ba8.55Er0.1Yb0.2Y2Si6O24 phosphor were investigated. The desired up‐conversion of the emitted light, which passed through the green, yellow, orange and red regions of the spectrum, was achieved through the use of appropriate Er3+ and/or Yb3+ concentrations in the host structure and 980 nm excitation light. The up‐conversion mechanism in the phosphors is described by an energy‐level schematic. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
6.
Tunable multicolor and white‐light upconversion luminescence in Yb3+/Tm3+/Ho3+ tri‐doped NaYF4 micro‐crystals
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NaYF4 micro‐crystals with various concentrations of Yb3+/Tm3+/Ho3+ were prepared successfully via a simple and reproducible hydrothermal route using EDTA as the chelating agent. Their phase structure and surface morphology were studied using powder X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD patterns revealed that all the samples were pure hexagonal phase NaYF4. SEM images showed that Yb3+/Tm3+/Ho3+ tri‐doped NaYF4 were hexagonal micro‐prisms. Upconversion photoluminescence spectra of Yb3+/Tm3+/Ho3+ tri‐doped NaYF4 micro‐crystals with various dopant concentrations under 980 nm excitation with a 665 mW pump power were studied. Tunable multicolor (purple, purplish blue, yellowish green, green) and white light were achieved by simply adjusting the Ho3+ concentration in 20%Yb3+/1%Tm3+/xHo3+ tri‐doped NaYF4 micro‐crystals. Furthermore, white‐light emissions could be obtained using different pump powers in 20%Yb3+/1%Tm3+/1%Ho3+ tri‐doped NaYF4 micro‐crystals at 980 nm excitation. The pump power‐dependent intensity relationship was studied and relevant energy transfer processes were discussed in detail. The results suggest that Yb3+/Tm3+/Ho3+ tri‐doped NaYF4 micro‐crystals have potential applications in optoelectronic devices such as photovoltaic, plasma display panel and white‐light‐emitting diodes. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
7.
Zhenyu Gao Lixin Yu Xiaoqin Man Jianlin Zhong Qihuang Guo Yingxuan Zou 《Luminescence》2019,34(8):830-837
The MgO–Ga2O3–SiO2 glasses and glass‐ceramics samples doped with Eu2+/Mn2+/Er3+ and heated in reductive atmosphere were prepared by the sol–gel method. The structure, morphology and the luminescence properties were studied using X‐ray diffraction, high‐resolution transmission electron microscope, fluorescence spectra, and up‐conversion emission. The luminescence characteristics of doped ions could be influenced by temperature and matrix component. The characteristic emission of Mn2+, Eu2+ and Er3+ were seen and the energy transfer efficiency from Eu2+ to Mn2+ was enhanced as Mn2+ concentration was increased. In addition, the two‐photon process was determined for the Er3+‐doped samples. 相似文献
8.
Preparation and up‐conversion luminescence properties of LaOBr:Yb3+/Er3+ nanofibers via electrospinning
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LaOBr:Yb3+/Er3+ nanofibers were synthesized for the first time by calcinating electrospun PVP/[La(NO3)3 + Er(NO3)3 + Yb(NO3)3 + NH4Br] composites. The morphology and properties of the final products were investigated in detail using scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X‐ray diffractometry (XRD) and fluorescence spectroscopy. The results indicate that LaOBr:Yb3+/Er3+ nanofibers are tetragonal in structure with a space group of P4/nmm. The diameter of LaOBr:Yb3+/Er3+ nanofibers is ~ 147 nm. Under the excitation of a 980‐nm diode laser, LaOBr:Yb3+/Er3+ nanofibers emit strong green and red up‐conversion emission centering at 519, 541 and 667 nm, ascribed to the 2H11/2, 4S3/2 → 4I15/2 and 4 F9/2 → 4I15/2 energy‐level transitions of Er3+ ions, respectively. The up‐conversion luminescent mechanism of LaOBr:Yb3+/Er3+ nanofibers is advanced. Moreover, near‐infrared emission of LaOBr:Yb3+/Er3+ nanofibers is obtained under the excitation of a 532‐nm laser. The formation mechanism of LaOBr:Yb3+/Er3+ nanofibers is proposed. LaOBr:Yb3+/Er3+ nanofibers could be important up‐conversion luminescent materials. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
9.
This work presents the optimized luminescence spectra for the Ce3+,Sm3+-doped NaSrPO4 phosphor that was synthesized using a wet chemical method. Ce3+ and Sm3+ are activator impurities that show spectral splitting bands that corresponds to the d–f and f–f transitions, respectively. These impurity elements shows the characteristics spectral bands when doped with the NaSrPO4 host lattice. Spectral splitting in the Ce3+ excitation band was monitored in the 240–340 nm range, in which the observed bands were located at 269 nm, 292 nm and 321 nm, and emission bands were observed in the broad spectral range 330–430 nm. However, when Sm3+ ion was doped in the same host lattice we obtained a characteristic emission band at 590 and 645 nm in the orange–red region, under sharp excitation bands located at 345, 361, 375, and 403 nm respectively. Also, we carried out energy transfer analysis in the Ce3+/Dy3+-doped NaSrPO4 phosphor. Further crystalline phase and the nanophase nature of the phosphor compound were confirmed using X-ray diffraction and transmission electron microscopy analyses. 相似文献
10.
Pure and Na+‐doped Alq3 complexes were synthesized by a simple precipitation method at room temperature, maintaining a stoichiometric ratio. These complexes were characterized by X‐ray diffraction, Fourier transform infrared (FTIR), UV/Vis absorption and photoluminescence (PL) spectra. The X‐ray diffractogram exhibits well‐resolved peaks, revealing the crystalline nature of the synthesized complexes, FTIR confirms the molecular structure and the completion of quinoline ring formation in the metal complex. UV/Vis absorption and PL spectra of sodium‐doped Alq3 complexes exhibit high emission intensity in comparison with Alq3 phosphor, proving that when doped in Alq3, Na+ enhances PL emission intensity. The excitation spectra of the synthesized complexes lie in the range 242–457 nm when weak shoulders are also considered. Because the sharp excitation peak falls in the blue region of visible radiation, the complexes can be employed for blue chip excitation. The emission wavelength of all the synthesized complexes lies in the bluish green/green region ranging between 485 and 531 nm. The intensity of the emission wavelength was found to be elevated when Na+ is doped into Alq3. Because both the excitation and emission wavelengths fall in the visible region of electromagnetic radiation, these phosphors can also be employed to improve the power conversion efficiency of photovoltaic cells by using the solar spectral conversion principle. Thus, the synthesized phosphors can be used as bluish green/green light‐emitting phosphors for organic light‐emitting diodes, flat panel displays, solid‐state lighting technology – a step towards the desire to reduce energy consumption and generate pollution free light. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
11.
Visible‐near‐infrared luminescent lanthanide ternary complexes based on beta‐diketonate using visible‐light excitation
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We used the synthesized dinaphthylmethane (Hdnm) ligand whose absorption extends to the visible‐light wavelength, to prepare a family of ternary lanthanide complexes, named as [Ln(dnm)3phen] (Ln = Sm, Nd, Yb, Er, Tm, Pr). The properties of these complexes were investigated by Fourier transform infrared (FT‐IR) spectroscopy, diffuse reflectance (DR) spectroscopy, thermogravimetric analyses, and excitation and emission spectroscopy. Generally, excitation with visible light is much more advantageous than UV excitation. Importantly, upon excitation with visible light (401–460 nm), the complexes show characteristic visible (Sm3+) as well as near‐infrared (Sm3+, Nd3+, Yb3+, Er3+, Tm3+, Pr3+) luminescence of the corresponding lanthanide ions, attributed to the energy transfer from the ligands to the lanthanide ions, an antenna effect. Now, using these near‐infrared luminescent lanthanide complexes, the luminescent spectral region from 800 to 1650 nm, can be covered completely, which is of particular interest for biomedical imaging applications, laser systems, and optical amplification applications. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
12.
13.
Tm3+:LaF3 nanocrystals were synthesized with hydrothermal technique. Local‐field effect on the radiative relaxation rate was studied in the system of Tm3+:LaF3 nanocrystals immersed in several liquid media. The fluorescence lifetime was measured. It was found that the fluorescence decay presented the characteristics of second‐order exponential decay, for which the contribution from the ions inside the nanocrystal and ions at the interface of the nanocrystal were distinguished. Investigating the experimental results with proposed models, we found that the surface effect had to be eliminated. For rare earth doped LaF3 nanocrystals, real‐cavity model well explains the influence of surrounding medium on the fluorescence relaxation rate. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
14.
Y2O3:Tm3+ and Li+ co‐doped Y2O3:Tm3+ nanopowders were synthesized using the solution combustion method for possible application in ultraviolet (UV) light dosimetry. X‐ray diffraction revealed the crystallite sizes to be in the range 21–44 nm and 30–121 nm using the Scherrer equation and the W‐H plot relationship, respectively. Field emission scanning electron microscopy confirmed that, after co‐doping with 4 mol% concentration of Li+, the particles were spherical in nature with an average size of ~30 nm. Fourier transformed infrared spectroscopy results showed bands at wavenumbers of 556, 1499, 1704, 2342, 2358, 2973, 3433, and 3610 cm?1 that corresponded to the stretching and bending vibrations of Y–O, C=O and O–H. Thermoluminescence (TL) glow peaks for Y2O3:Tm3+ nanophosphors observed at 399 and 590 K were attributed to oxygen defects caused using UV irradiation. These oxygen defects firstly resulted in an increased prominent peak TL intensity for up to 270 min of irradiation and then a decrease. This was attributed to the presence of oxygen defect clusters that caused a reduction in recombination centres. The Li+ co‐doped sample showed peaks at 356, 430, and 583 K and its intensity sublinearly increased up to 90 min and then thereafter decreased. The TL trapping parameters were calculated using computerized glow curve deconvolution methods. The Li+ co‐doped sample exhibited less fading and high trap density under the UV radiation. 相似文献
15.
Yu‐Guo Yang Xu‐Ping Wang Bing Liu Yuan‐Yuan Zhang Xian‐Shun Lv Jing Li Lei Wei Hua‐Jian Yu Yanyan Hu Hua‐Di Zhang 《Luminescence》2020,35(4):580-585
Dy3+‐doped Y3Al5O12 phosphors were prepared at a relatively low temperature using molten salt synthesis. The phase of the prepared Dy3+‐doped Y3Al5O12 phosphors was confirmed using X‐ray powder diffraction. Results indicated that Dy3+ doping did not change the Y3Al5O12 phase. Following excitation at 352 nm, emission spectra of the Dy3+‐doped Y3Al5O12 phosphors consisted of blue, yellow, and red emission bands. The influence of Dy3+ concentration and excitation wavelength on emission was investigated. The ratio of yellow light to blue light varied with change in Dy3+ doping concentration, due to changes in the structure around Dy3+. Emission intensities also changed when the excitation wavelength was changed. This variation is luminescence generated a system for tunable white light for Dy3+‐doped Y3Al5O12 phosphors. 相似文献
16.
White‐ and blue‐light‐emitting dysprosium(III) and terbium(III)‐doped gadolinium titanate phosphors
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Here we report the synthesis and structural, morphological, and photoluminescence analysis of white‐ and blue‐light‐emitting Dy3+‐ and Tm3+‐doped Gd2Ti2O7 nanophosphors. Single‐phase cubic Gd2Ti2O7 nanopowders consist of compact, dense aggregates of nanoparticles with an average size of ~25 nm for Dy3+‐doped and ~50 nm for Tm3+‐doped samples. The photoluminescence results indicated that ultraviolet (UV) light excitation of the Dy3+‐doped sample resulted in direct generation of white light, while a dominant yellow emission was obtained under blue‐light excitation. Intense blue light was obtained for Tm3+‐doped Gd2Ti2O7 under UV excitation suggesting that this material could be used as a blue phosphor. 相似文献
17.
T. Kalpana Y. Gandhi V. Sudarsan M. Piasecki V. Ravi Kumar N. Veeraiah 《Luminescence》2016,31(7):1358-1363
BaO‐B2O3‐P2O5 glasses doped with a fixed concentration of Tb3+ ions and varying concentrations of Al2O3 were synthesized, and the influence of the Al3+ ion concentration on the luminescence efficiency of the green emission of Tb3+ ions was investigated. The optical absorption, excitation, luminescence spectra and fluorescence decay curves of these glasses were recorded at ambient temperature. The emission spectra of terbium ions when excited at 393 nm exhibited two main groups of bands, corresponding to 5D3 → 7Fj (blue region) and 5D4 → 7Fj (green region). From these spectra, the radiative parameters, viz., spontaneous emission probability A, total emission probability AT, radiative lifetime τ and fluorescent branching ratio β, of different transitions originating from the 5D4 level of Tb3+ ions were evaluated based on the Judd‐Ofelt theory. A clear increase in the quantum efficiency and luminescence of the green emission of Tb3+ ions corresponding to 5D4 → 7F5 transition is observed with increases in the concentration of Al2O3 up to 3.0 mol%. The improvement in emission is attributed to the de‐clustering of terbium ions by Al3+ ions and also to the possible admixing of wave functions of opposite parities. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
18.
LaBSiO5 phosphors doped with Ce3+ and Tb3+ were synthesized using the conventional solid‐state method at 1100 °C. The phase purity and luminescent properties of these phosphors are investigated. LaBSiO5:Tb3+ phosphors show intense green emission, and LaBSiO5 phosphors doped with Ce3+ show blue–violet emission under UV light excitation. LaBSiO5 phosphors co‐doped with Ce3+ and Tb3+ exhibit blue–violet and green emission under excitation by UV light. The blue–violet emission is due to the 5d–4f transition of Ce3+ and the green emission is ascribed to the 5D4 → 7 F5 transition of Tb3+. The spectral overlap between the excitation band of Tb3+ and the emission band of Ce3+ supports the occurrence of energy transfer from Ce3+ to Tb3+, and the energy transfer process was investigated. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
19.
R. Viswanath H. S. Bhojya Naik G. Arun Kumar I. K. Suresh Gowda S. Yallappa 《Luminescence》2017,32(7):1212-1220
Luminescence technology has been improved with the help of semiconductor nanoparticles that possess novel optical and electrical properties compared with their bulk counterpart. The aim of this study was to design semiconductor nanocrystals in their pure (ZnS) or doped form (ZnS:Mn) with different concentrations of Mn2+ ions by a wet chemical route stabilized by ethylenediamine tetra‐acetic acid (EDTA) and to evaluate their luminescence properties. The nanocrystals were characterized by physicochemical techniques such as X‐ray diffraction (XRD), High‐resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SEAD), EDS, and ultraviolet (UV)–visible light and photoluminescence (PL) studies. These results showed the presence of cubic phase and spherically shaped nanocrystals. A blue shift with respect to their bulk counterpart was observed. PL emission spectra were observed with a fixed blue peak and the yellow‐orange bands were red shifted towards the red region under the same excitation wavelength. The orange‐red bands were attributed to the radiation transition of electrons in 3d5 unfilled shells of Mn2+ ions [4T1(4G)‐6A1(6S)]; the ZnS matrix varied with Mn2+ concentration. Shift and increase in the intensity of the PL and absorption bands were observed with increase in Mn content. The study showed that Mn2+‐doped ZnS nanocrystal emission bands can be tuned from the yellow‐orange to the red regions under a controlled synthesis process and could be used as promising luminescent emitters in the biology field upon functionalization with suitable materials. Further studies on construction with various other materials will be useful for practical applications. 相似文献
20.
Structural and luminescence properties of Sm3+‐doped bismuth phosphate glass for orange‐red photonic applications
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In the present study, the effect of bismuth oxide (Bi2O3) content on the structural and optical properties of 0.5Sm3+‐doped phosphate glass and the effect of concentration on structural and optical properties of Sm3+‐doped bismuth phosphate (BiP) glass were studied. Structural characterization was accomplished using X‐ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy and 31P nuclear magnetic resonance (NMR) spectroscopy. Optical properties were studied using absorption, photoluminescence and decay measurements. Using optical absorption spectra, Judd–Ofelt parameters were derived to determine the local structure and bonding in the vicinity of Sm3+ ions. The emission spectra of Sm3+‐doped BiP glass showed two intense emission bands, 4G5/2→6H7/2 (orange) and 4G5/2→6H9/2 (red) for which the stimulated emission cross‐sections (σe) and branching ratios (β) were found to be higher. The quantum efficiencies were also calculated from decay measurements recorded for the 4G5/2 level of Sm3+ ions. The suitable combination of Bi2O3 (10 mol%) and Sm3+ (0.5 mol%) ions in these glasses acted as an efficient lasing material and might be suitable for the development of visible orange‐red photonic materials. 相似文献