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1.
The optical properties of a Ho 3+/Yb 3+ co‐doped CaSc 2O 4 oxide material are investigated in detail. The spectral properties are described as a function of doping concentrations. The efficient Yb 3+→Ho 3+ energy transfer is observed. The transfer efficiency approaches 50 % before concentration quenching. The concentration‐optimized sample exhibits a strong green emission accompanied with a weak red emission, showing perfect green monochromaticity. The results of the spectral distribution, power dependence, and lifetime measurements are presented. The green, red, and near‐infrared (NIR) emissions around 545, 660, and 759 nm are assigned to the 5F 4+ 5S 2→ 5I 8, 5F 5→ 5I 8, and 5F 4+ 5S 2→ 5I 7 transitions of Ho 3+, respectively. The detailed study reveals the upconversion luminescence mechanism involved in a novel Ho 3+/Yb 3+ co‐doped CaSc 2O 4 oxide material. 相似文献
2.
Ho 3+/Yb 3+ co‐doped PbTiO 3 nanocrystals with different content of dopant were successfully prepared via a facile hydrothermal method. The purity, morphology, element distribution, chemical state and up‐conversion (UC) photoluminescence (PL) of PbTiO 3 nanocrystals affected by Ho 3+ dopant are investigated systematically. X‐ray diffraction (XRD) results illustrate that PbTiO 3 samples with the doping Ho 3+ concentration ranging from 0 to 5 mol‐% are perovskite structure. The doping Ho 3+ ions have no change on the crystal structure of perovskite PbTiO 3. Owing to the non‐equivalent substitution of Ho 3+ to Ti 4+ in PbTiO 3, the particle size of Ho 3+/Yb 3+ co‐doped PbTiO 3 samples is decreased as well as the particle agglomeration is detected. Moreover, Ho and Yb ions have uniform distributions in the PbTiO 3 nanoparticles as the presence of Ho 3+ and Yb 3+ cations. The up‐conversion spectra demonstrate that Ho/Yb co‐doped PbTiO 3 samples have up‐conversion emissions centered at 550 nm, 660 nm and 755 nm, corresponding to the transitions of 5F 4( 5S 2)→ 5I 8, 5F 5→ 5I 8 and 5S 2( 5F 4)→ 5I 7 of Ho 3+ ions. Additionally, the effect of temperature on the UC PL property of Ho 3+/Yb 3+ co‐doped PbTiO 3 system is further investigated. The sensitivity and the trend of Ho 3+/Yb 3+ co‐doped PbTiO 3 samples in temperature from 298 k to 493K are calculated on the basis of fluorescence intensity ratio (FIR) method. Ho 3+/Yb 3+ co‐doped PbTiO 3 nanocrystals are verified the high potential in the optical temperature sensing. 相似文献
3.
A co-doped LiNb 0.3Ta 0.7O 3:Er 3+,Yb 3+ ceramic was prepared by a high temperature solid state procedure. Under the excitation of 980 nm laser radiation, intense 660 nm red light and 550 nm green light emissions corresponding to the 4F 9/2→ 4I 15/2 and 2H 11/2/ 4S 3/2→ 4I 15/2 transitions of Er 3+ were observed. The change of Yb 3+ concentration has a more significant influence on luminous intensity than the Er 3+ concentration. The emission of red and green lights is attributed to a two-photon process. The upconversion luminescence mechanisms were analyzed in detail. 相似文献
4.
Upconversion luminescence tuning of β‐NaYF 4 nanorods under 980 nm excitation has successfully been achieved by tridoping with Ln 3+ ions with different electronic structures. The effects of Ce 3+ ions on NaYF 4:Yb 3+/Ho 3+ as well as Gd 3+ ions on NaYF 4:Yb 3+/Tm 3+(Er 3+) have been studied in detail. By tridoping with Ce 3+ ions, not only were unusual 5G 5→ 5I 7 and 5F 2/ 3K 8→ 5I 8 transitions from Ho 3+ ions and 5d→4f transitions from Ce 3+ ions observed in NaYF 4:Yb 3+/Ho 3+ nanorods, but also an increase in the intensity of 5F 5→ 5I 8 relative to 5S 2/ 5F 4→ 5I 8 with increasing Ce 3+ concentration, which can be attributed to efficient energy transfers of 5I 6 (Ho)+ 2F 5/2 (Ce)→ 5I 7 (Ho)+ 2F 7/2 (Ce) and 5S 2/ 5F 4 (Ho)+ 2F 5/2 (Ce)→ 5F 5 (Ho)+ 2F 7/2 (Ce). Interestingly, with increasing pump power density, the luminescence of NaYF 4:Yb 3+/Ho 3+ nanorods is always dominated by the 5S 2/ 5F 4→ 5I 8 transition, whereas the luminescence of Ce 3+‐tridoped NaYF 4:Yb 3+/Ho 3+ nanorods is dominated by the 5S 2/ 5F 4→ 5I 8 and 5G 5→ 5I 7 transitions in turn. These observations are discussed on the basis of a rate equation model. Furthermore, Gd 3+‐tridoped NaYF 4:Yb 3+/Tm 3+(Er 3+) nanorods can emit multicolor upconversion emissions spanning from the UV to the near‐infrared under 980 nm excitation. 6P 5/2→ 8S 7/2 (≈306 nm) and 6P 7/2→ 8S 7/2 (≈311 nm) transitions from Gd 3+ ions were observed. In addition to the aforementioned luminescence properties, these Gd 3+‐tridoped nanorods also exhibit paramagnetic behavior at room temperature and superparamagnetic behavior at 2 or 5 K. 相似文献
5.
To develop new emission-tunable upconversion (UC) phosphors, the Sr 3AlO 4F:5%Yb 3+, xEr 3+, yHo 3+ (0 ≤ x ≤ 1%, 0 ≤ y ≤ 1%) samples were prepared by conversional solid-state reaction method, and their luminescence properties upon 980 nm excitation were studied. Upon 980 nm excitation, Yb 3+-Er 3+ codoped Sr 3AlO 4F shows a predominant emission peak between 645 and 700 nm which is attributed to the 4F 9/2- 4I 15/2 transition of Er 3+, and the Er 3+ green emissions have been almost quenched. In this case, the yellowish green emitting light is obtained. The possible reason was interpreted by the energy level diagram and the proposed UC mechanism. For Yb 3+-Ho 3+ codoped Sr 3AlO 4F, three emissions are observed obviously which are all derived from the Ho 3+ ion. The corresponding chromaticity coordinates indicate a red emission has been gained. To realize the tunable emission, the typical Sr 3AlO 4F:5%Yb 3+, 0.2%Er 3+, 1%Ho 3+ phosphor was developed, and its emission spectrum includes the emission peaks of both Er 3+ and Ho 3+. Correspondingly, the sample gives a yellow emission. 相似文献
6.
The glasses of the composition (40 ? x)PbO–(5 + x)Al 2O 3–54SiO 2:1.0Yb 2O 3 (in mol%) with x ranging from 5 to 10 have been synthesized. The IR spectral studies of these glasses have indicated that there is a gradual transformation of Al 3+ ions from tetrahedral to octahedral coordination with increase of Al 2O 3 content in the glass network. The optical absorption and luminescence spectra have exhibited bands originating from 2F 7/2 → 2F 5/2 and 2F 5/2 → 2F 7/2 transitions, respectively. From these spectra, the absorption and emission cross-sections and fluorescence lifetime of Yb 3+ ions have been evaluated. Quantitative analysis of these data indicated a decreasing radiative trapping and increasing fluorescence lifetime of Yb 3+ ions with increasing Al 2O 3 content. This may be explained by structural variations in the vicinity of Yb 3+ ions due to variation in the concentration of Al 2O 3 in the glass network. 相似文献
7.
Multifunctional NaGdF 4:Yb 3+,Er 3+,Nd 3+@NaGdF 4:Nd 3+ core–shell nanoparticles (called Gd:Yb 3+,Er 3+,Nd 3+@Gd:Nd 3+ NPs) with simultaneously enhanced near‐infrared (NIR)‐visible (Vis) and NIR‐NIR dual‐conversion (up and down) luminescence (UCL/DCL) properties were successfully synthesized. The resulting core–shell NPs simultaneously emitted enhanced UCL at 522, 540, and 660 nm and DCL at 980 and 1060 nm under the excitation of a 793 nm laser. The enhanced UCL and DCL can be explained by complex energy‐transfer processes, Nd 3+→Yb 3+→Er 3+ and Nd 3+→Yb 3+, respectively. The effects of Nd 3+ concentration and shell thickness on the UCL/DCL properties were systematically investigated. The UCL and DCL properties of NPs were observed under the optimal conditions: a shell Nd 3+ content of 20 % and a shell thickness of approximately 5 nm. Moreover, the Gd:Yb 3+,Er 3+,Nd 3+@Gd:20 % Nd 3+ NPs exhibited remarkable magnetic resonance imaging (MRI) properties similar to that of a clinical agent, Omniscan. Thus, the core–shell NPs with excellent UCL/DCL/magnetic resonance imaging (MRI) properties have great potential for both in vitro and in vivo multimodal bioimaging. 相似文献
8.
A set of new triple molybdates, Li xNa 1-xCaGd 0.5(MoO 4) 3:Ho 3+0.05/Yb 3+0.45, was successfully manufactured by the microwave-accompanied sol–gel-based process (MAS). Yellow molybdate phosphors Li xNa 1-xCaGd 0.5(MoO 4) 3:Ho 3+0.05/Yb 3+0.45 with variation of the Li xNa 1-x (x = 0, 0.05, 0.1, 0.2, 0.3) ratio under constant doping amounts of Ho 3+ = 0.05 and Yb 3+ = 0.45 were obtained, and the effect of Li + on their spectroscopic features was investigated. The crystal structures of Li xNa 1-xCaGd 0.5(MoO 4) 3:Ho 3+0.05/Yb 3+0.45 (x = 0, 0.05, 0.1, 0.2, 0.3) at room temperature were determined in space group I4 1/ a by Rietveld analysis. Pure NaCaGd 0.5Ho 0.05Yb 0.45(MoO 4) 3 has a scheelite-type structure with cell parameters a = 5.2077 (2) and c = 11.3657 (5) Å, V = 308.24 (3) Å 3, Z = 4. In Li-doped samples, big cation sites are occupied by a mixture of (Li,Na,Gd,Ho,Yb) ions, and this provides a linear cell volume decrease with increasing Li doping level. The evaluated upconversion (UC) behavior and Raman spectroscopic results of the phosphors are discussed in detail. Under excitation at 980 nm, the phosphors provide yellow color emission based on the 5S 2/ 5F 4 → 5I 8 green emission and the 5F 5 → 5I 8 red emission. The incorporated Li + ions gave rise to local symmetry distortion (LSD) around the cations in the substituted crystalline structure by the Ho 3+ and Yb 3+ ions, and they further affected the UC transition probabilities in triple molybdates Li xNa 1-xCaGd 0.5(MoO 4) 3:Ho 3+0.05/Yb 3+0.45. The complex UC intensity dependence on the Li content is explained by the specificity of unit cell distortion in a disordered large ion system within the scheelite crystal structure. The Raman spectra of Li xNa 1-xCaGd 0.5(MoO 4) 3 doped with Ho 3+ and Yb 3+ ions were totally superimposed with the luminescence signal of Ho 3+ ions in the range of Mo–O stretching vibrations, and increasing the Li + content resulted in a change in the Ho 3+ multiplet intensity. The individual chromaticity points (ICP) for the LiNaCaGd(MoO 4) 3:Ho 3+,Yb 3+ phosphors correspond to the equal-energy point in the standard CIE (Commission Internationale de L’Eclairage) coordinates. 相似文献
9.
综合ZnO-Al 2O 3-SiO 2系和锗酸盐玻璃陶瓷的优点,采用熔融-晶化法首次制备了Ho 3+/Yb 3+共掺以ZnAl 2O 4为主晶相的ZnO-Al 2O 3-GeO 2-SiO 2系玻璃陶瓷。因[GeO 4]四面体和[SiO 4]四面体都是玻璃网络形成体,讨论了GeO 2取代SiO 2对玻璃陶瓷样品硬度及发光性能的影响,最终确定GeO 2的取代量为10.55%( w/w)时,玻璃陶瓷综合性能最佳。在980 nm泵浦光的激发下,发现强的绿色(546 nm)和弱的红色(650 nm)上转换发光,并研究了不同Ho 3+/Yb 3+掺杂比对样品上转换发光的影响,最终结果表明当Ho 3+/Yb 3+掺杂比为1:11( n/n)时样品荧光强度最强,在绿色上转换发光材料方面具有潜在的应用。 相似文献
10.
Lanthanide upconversion luminescence in nanoparticles has prompted continuous breakthroughs in information storage, temperature sensing, and biomedical applications, among others. Achieving upconversion luminescence at the molecular scale is still a critical challenge in modern chemistry. In this work, we explored the upconversion luminescence of solution dispersions of co-crystals composed of discrete mononuclear Yb(DBM) 3Bpy and Eu(DBM) 3Bpy complexes (DBM: dibenzoylmethane, Bpy: 2,2′-bipyridine). The 613 nm emission of Eu 3+ was observed under excitation of Yb 3+ at 980 nm. From the series of molecular assemblies studied, the most intense luminescence was obtained for a 1 : 1 molar ratio of Yb 3+ : Eu 3+, resulting in a high quantum yield of 0.67 % at 2.1 W cm −2. The structure and energy transfer mechanism of the assemblies were fully characterized. This is the first example of an Eu 3+-based upconverting system composed of two discrete mononuclear lanthanide complexes present as co-crystals in non-deuterated solution. 相似文献
11.
LaGaO 3:Tm 3+, Yb 3+ powder was synthesized by a high-energy ball milling (HEB) and a conventional solid state reaction (SSR). The X-ray diffraction patterns confirmed the LaGaO 3:Tm 3+, Yb 3+ powder phosphors to have an orthorhombic structure. The spectrum consisted of 1G 4 → 3H 6, weak 1G 4 → 3F 4, and intense 3H 4 → 3H 6 transition bands within the f 12 configuration of Tm 3+, together with the 2F 5/2 → 2F 7/2 transition of Yb 3+. Up-converted emission of the LaGaO 3:Tm 3+, Yb 3+ powders were observed under laser diode excitation of 975 nm. The PL intensity of the HEB-LaGaO 3:Tm 3+, Yb 3+ powders sintered at 1300 °C were higher than those of all LaGaO 3:Tm 3+, Yb 3+ powder samples examined. The energy transition probability of HEB-LaGaO 3:Tm 3+, Yb 3+ powders are higher than that of the SSR-LaGaO 3:Tm 3+, Yb 3+ powders. Compared to the solid state reaction method, synthesis by high-energy ball milling is simple and provides improved crystallinity of the host. 相似文献
12.
Due to the unique size effects, nanomaterials in infrared absorption have attracted much attention for their strong absorption in the infrared region. To achieve the infrared multi‐band absorption, we propose to synthesize a core‐shell structure nanomaterial consisting of NaYF 4:Yb 3+, Er 3+ core and a layer of SiO 2 as shell. A series of NaYF 4:Yb 3+, Er 3+ nanocrystals were synthesized through hydrothermal method by adjusting the ratio of citric acid(CA)‐to‐NaOH, and the effects of CA concentration, and NaOH concentration were studied in detail. NaYF 4:Yb 3+, Er 3+@SiO 2 nanoparticles were synthesized by sol‐gel method using TEOS as silica source. The results show that the core‐shell NaYF 4:Yb 3+, Er 3+@SiO 2 nanoparticles were successfully synthesized. Up‐conversion spectra of these nanoparticles were recorded with 980 nm laser excitation under room temperature. There are no changes of the emission centers of nanoparticles before or after silica coating, but the emission intensities of nanoparticles after silica coating are weakened. Furthermore, the property of infrared multi‐band absorption was tested through ultraviolet‐visible‐near infrared spectrophotometer and infrared absorption spectra. The results illustrate that the multi‐band infrared absorption nanomaterial was successfully synthesized. 相似文献
13.
This paper reports on comparative investigation of structure and luminescence properties of tetragonal LiYF 4 and BaYF 5, and hexagonal NaYF 4 phosphors codoped with Er 3+/Yb 3+ by a facile hydrothermal synthesis. The products were characterized by X-ray diffractometer, scanning electron microscope, and photoluminescence spectroscopy. Intense visible emissions centered at around 525, 550 and 650 nm, originated from the transitions of 2H 11/2 → 4I 15/2, 4S 3/2 → 4I 15/2, and 4F 9/2 → 4I 15/2 of Er 3+, respectively, have been observed in all the samples upon excitation with a 980 nm laser diode, and the involved mechanisms have been explained. Based on the green up-conversion emission performance, the Yb 3+ concentrations of Er 3+/Yb 3+-codoped LiYF 4, BaYF 5, and NaYF 4 phosphors have been optimized to be 10, 20, and 20 mol.%, respectively. The quadratic dependence of fluorescence on excitation laser power has confirmed that two-photon contribute to up-conversion of the green–red emissions. 相似文献
14.
Substitutional, continuous solid solution of the general formula Y2–xYbxO3 was obtained from the mixture of Y2O3 and Yb2O3 oxides, for the first time by the mechanochemical method in a high-energy ball milling. The monophasic samples of nanocrystalline solid solution for x?>?0.00 and x?<?2.00 were examined by the methods: XRD, DTA, SEM, IR and UV–Vis–DR. As follows from the results, the solid solution crystallizes in cubic system and is isostructural with Y2O3 and Yb2O3. The solution is stable in the air atmosphere up to at least 900°C, and its decomposition temperature decreases with the increase in x, that is, with decreasing number of Yb3+ ions replacing Y3+ ions in the crystal lattice of Y2O3. The energy band gap estimated for the solid solution varies from?~?5.30 eV for x?=?0.50 to?~?4.90 eV for x?=?1.50, which means that it is an insulator. 相似文献
15.
综合ZnO-Al_2O_3-SiO_2系和锗酸盐玻璃陶瓷的优点,采用熔融-晶化法首次制备了Ho~(3+)/Yb~(3+)共掺以ZnAl_2O_4为主晶相的ZnO-Al_2O_3-GeO_2-SiO_2系玻璃陶瓷。因[GeO_4]四面体和[SiO_4]四面体都是玻璃网络形成体,讨论了GeO_2取代SiO_2对玻璃陶瓷样品硬度及发光性能的影响,最终确定GeO_2的取代量为10.55%(w/w)时,玻璃陶瓷综合性能最佳。在980 nm泵浦光的激发下,发现强的绿色(546 nm)和弱的红色(650 nm)上转换发光,并研究了不同Ho~(3+)/Yb~(3+)掺杂比对样品上转换发光的影响,最终结果表明当Ho~(3+)/Yb~(3+)掺杂比为1∶11(n/n)时样品荧光强度最强,在绿色上转换发光材料方面具有潜在的应用。 相似文献
16.
The monodisperse array and nanowires of Y 2O 3:Eu 3+ phosphor were synthesized using anodic aluminum oxide (AAO) template by sol–gel method. Scanning electron microscope (SEM) images indicated that Y 2O 3:Eu 3+ nanowires are parallelly arranged, all of which are in uniform diameter of about 50 nm. The high-magnification SEM image showed that each nanowire is composed of a lot of agglutinating particles. The patterns of selected-area electron diffraction confirmed that Y 2O 3:Eu 3+ nanowires mainly consist of polycrystalline materials. Excitation and emission spectra of Y 2O 3:Eu 3+/AAO composite films were measured. The characteristic red emission peak of Eu 3+ ion attributed to 5D 0→ 7F 2 transition in Y 2O 3:Eu 3+/AAO nanowires broadened its halfwidth. 相似文献
17.
Downconversion (DC) with emission of two near-infrared photons about 1000 nm for each blue photon absorbed was obtained in thulium (Tm 3+) and ytterbium (Yb 3 ) codoped yt-trium lithium fluoride (LiYF 4) single crystals grown by an improved Bridgman method. The luminescent properties of the crystals were measured through photoluminescence excitation, emission spectra and decay curves. Luminescence between 960 and 1050 nm from Yb 3 : 2F 5/2→ 2F 7/2 transition, which was originated from the DC from Tm 3 ions to Yb 3 ions, was observed under the excitation of blue photon at 465 nm. Moreover, the energy transfer processes were studied based on the Inokuti-Hirayama model, and the results indicated that the energy transfer from Tm 3 to Yb 3 was an electric dipole-dipole interaction. The max-imum quantum cutting effciency approached up to 167.5% in LiYF 4 single crystal codoped with 0.49mol% Tm 3 and 5.99mol% Yb 3 . Application of this crystal has prospects for increasing the energy e ciency of crystalline Si solar cells by photon doubling of the high energy part of the solar spectrum 相似文献
18.
The luminescence properties of 2%Er 3+/15%Yb 3+ doped LnP 0.5V 0.5O 4 (LnPVO 4) (Ln = Y, Gd, La) phosphors, synthesized via the traditional citric-assisted Sol gel method, are studied under light excitations of 980 nm and 325 nm to generate the 2H 11/2/ 4S 3/2– 4I 15/2 transitions via up- and downshifting mechanisms, respectively. The phase purity of the samples was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). We present herein a comparative study of the spectral and temperature sensing properties of LnPVO 4: Er 3+/Yb 3+ (Ln = Y, Gd, La) phosphors. The crystal field effects on the up-shifting luminescence and on the thermometric parameters are investigated by the substitution of Er 3+ ions on Y 3+, Gd 3+ or La 3+ sites in the YPVO 4, GdPVO 4 and LaPVO 4 hosts respectively. Fluorescence intensity ratio (FIR) technique was used to study the temperature sensing behavior of the phosphors. This study showed that downshifting emission gives the highest thermal sensitivities and the greatest thermal resolution compared to downshifting emission. These outcomes indicate that these materials are preferred for use in the luminescence temperature sensing in a down-conversion process to provide the greatest performance. 相似文献
19.
Tm 3+/Yb 3+ codoped rod-like YF 3 nanocrystals were synthesized through a facile hydrothermal method. After annealing in an argon atmosphere, the nanocrystals emitted bright blue and intense ultraviolet (UV) light under a 980-nm continuous wave diode laser excitation. Up-conversion emissions centered at ∼291 nm ( 1I 6 → 3H 6), ∼347 nm ( 1I 6 → 3F 4), ∼362 nm ( 1D 2 → 3H 6), ∼452 nm ( 1D 2 → 3F 4), ∼476 nm ( 1G 4 → 3H 6), ∼642 nm ( 1G 4 → 3F 4), and ∼805 nm ( 3H 4 → 3H 6) were recorded using a fluorescence spectrophotometer. Especially, enhanced UV emissions were studied by changing Yb 3+/Tm 3+ doping concentrations, the annealing temperatures, and the excitation power densities. A possible mechanism, energy transfer-cross relaxation-energy transfer (ET-CR-ET), was proposed based on a simple rate-equation model to elucidate the process of the enhanced UV emissions. 相似文献
20.
Polytitanasiloxane solutions containing Eu 3+ ions have been prepared by the hydrolytic cocondensation of tetraethoxysilane and tetrabutyl titanate. The UV‐vis absorption and the luminescence intensity were both found to increase with the increase of tetrabutyl titanate/tetraethoxysilane (TBT/TEOS) molar ratio. This revealed that the incorporation of TiO 2 can result in the increase of absorption energy of the Ti? O group by near‐UV excitation and in the increase of energy transfer to the metal ion. At the same time, the intensity ratio of 5D 0→ 7F 2 to 5D 0→ 7F 1 increases as the TBT/TEOS molar ratio increases, indicating the formation of Eu 3+? O 2?? Ti 4+ bonding. A longer decay time means that the Eu 3+ ions are better dispersed and less clustered with the increase of TBT/TEOS molar ratio. The results on the luminescence properties of the Eu 3+ in different media containing ethanol or water suggest that the incorporation of TiO 2 can shield Eu 3+ ions from the effect of water and ethanol molecules, which leads to an improvement of the Eu 3+ surroundings. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1357–1363, 2006 相似文献
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