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1.
The upconversion nanophosphors (UCNPs) of Yb3+/Er3+ co-doped into Y2O3, La2O3, and Gd2O3 were synthesized via the combustion method and characterized by powder X-ray diffractometer (XRD), scanning electron microscopy (SEM) and upconversion fluorescence spectroscopy. The characterization results showed that at the same flame temperature (2705 K) and precursor concentration (0.1 M), pure monoclinic and cubic-phase phosphors were achieved on Gd2O3 and Y2O3 hosted UCNPs, respectively; while the mixed phases were observed on La2O3 hosted UCNPs. Further annealing process at 850 °C produced pure cubic-phase La2O3:Yb3+,Er3+ UCNPs; while there was no phase transition observed on Gd2O3:Yb3+,Er3+ UCNPs. The dependence of upconversion luminescence on precursor concentrations and host materials was then examined. The La2O3 and Gd2O3 hosts were shown to be the promising alternates for the commonly used Y2O3 hosts for rare-earth doped phosphors. 相似文献
2.
A facile strategy using cheap and readily available precursors has been successfully developed for the synthesis of rare-earth
doped hexagonal phase NaYF4 nanocrystals with uniform shape and small particle size as well as strong photoluminescence. Due to their optical properties
and good biocompatibility, these multicolor nanocrystals were successfully used as a bio-tag for cancer cell imaging. This
novel synthetic method should also be capable of extension to the synthesis of other fluoride nanocrystals such as YF3 and LaF3.
相似文献
3.
Zhai X Shi F Chen H Zhao D Zhang D Qin W 《Journal of nanoscience and nanotechnology》2011,11(11):9693-9696
Tm3+ and Yb3+ codoped NaYF4 upconversion (UC) nanoparticles (NPs) with intense ultraviolet (UV) fluorescence were synthesized using a solvothermal approach. NIR optical rewritable film incorporated with the UCNPs and dithienylethene (DTE) were performed for optical storage based on the photochromic reaction of DTE induced by the intense UV from themultiphoton UC fluorescence of NaYF4NPs. The photochromic DTE did not exhibit obvious fatigue after repetitious write/erase cycles using NIR/green irradiation. 相似文献
4.
Lunjun Gong Jicheng Yang Yuyu Li Mo Ma Changfu Xu Guozhong Ren Jianguo Lin Qibin Yang 《Journal of Materials Science》2013,48(10):3672-3678
Uniform ultrasmall monodisperse SrYbF5 and SrErF5 nanocrystals (NCs) were synthesized via solvothermal method using oleic acid as stabilizing agent. Transmission electron microscopy and X-ray diffraction assays reveal that the as-synthesized NCs are of face-centered cubic structure and the cell parameters are 5.608 Å (SrYbF5) and 5.632 (SrErF5) Å. Under the excitation of a 980 nm laser, visible upconversion (UC) emission can be observed by naked eyes in Tm3+ or Er3+ doped SrYbF5 NCs. The integrated intensity of infrared emission is nearly two orders of magnitude stronger than that of the blue emission of SrYbF5:Tm3+ NCs. The energy transfer UC emission mechanisms were also investigated. 相似文献
5.
Nonlinear upconversion quenching in Er-doped materials has been studied with use of Monte-Carlo modeling. Structure models allowed one to consider homogeneous Er3+ ions space distributions as well as clustering. Two variants of the simulation algorithm have been developed which took into account an evolution of one excitation or evolutions of all excitations simultaneously. The obtained results provided quantitative data on the influence of the following factors on the upconversion efficiency: (a) erbium content, (b) migration of excitation, (c) pump power, and (d) duration of pulse pumping. 相似文献
6.
Rui Cheng Yanrui Chen Zhiqiang Li Xiaohong Chen Pingxiong Yang Hongbing Zhu Yuelong Huang Zhuo Sun Sumei Huang 《Journal of Materials Science: Materials in Electronics》2014,25(9):4066-4073
We report for the first time the preparation of Yb3+–Er3+ co-doped β-phase sodium gadolinium fluoride (NaGdF4:Yb/Er) microcrystals using citric acid (CA) as a shape modifier and the application of NaGdF4:Yb/Er to amorphous silicon solar cells. The proposed hydrothermal method was facile and eco-friendly. It was found that CA played a critical role in the shape evolution of the final products. The related synthesis mechanisms are discussed. Under 980 nm laser excitation, the optimized NaGdF4:Yb/Er crystals exhibited strong upconversion (UC) emissions at visible wavelengths. Amorphous silicon thin film solar cells were designed and fabricated for investigating different UC configurations. In combination with a metallic back reflector, the cell with the front side UC layer achieved a six-fold improvement of the photocurrent while the cell with the rear side UC layer exhibited a ten-fold enhancement of the photocurrent, under 980 nm light, compared with the cell without upconverter. 相似文献
7.
Wei W He T Teng X Wu S Ma L Zhang H Ma J Yang Y Chen H Han Y Sun H Huang L 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(14):2271-2276
Upconversion rare-earth nanomaterials (URENs) possess highly efficient near-infrared (NIR), e.g., 980 nm, laser absorption and unique energy upconversion capabilities. On the other hand, graphene and its derivatives, such as graphene oxide (GO), show excellent performance in optical limiting (OL); however, the wavelengths of currently used lasers for OL studies mainly focus on either 532 or 1064 nm. To design new-generation OL materials working at other optical regions, such as the NIR, a novel nanocomposites, GO-URENs, which combines the advantages of both its components, is synthesized by a one-step chemical reaction. Transmission electron microscopy, X-ray diffraction, infrared spectroscopy, and fluorescence studies prove that the α-phase URENs uniformly attach on the GO surface via covalent chemical bonding, which assures highly efficient energy transfer between URENs and GO, and also accounts for the significantly improved OL performance compared to either GO or URENs. The superior OL effect is also observed in the proof-of-concept thin-film product, suggesting immediate applications in making high-performance laser-protecting products and optoelectronic devices. 相似文献
8.
Infrared to visible and ultraviolet upconversion in Nd3+ doped KPb2Cl5 crystal is reported. Three intense bands have been observed at 535, 595, and 668 nm coming mainly from levels 4G7/2–4G9/2, together with emissions at 362, 388, 420 and 456 nm coming from level 4D3/2, and a peak at 435 nm, corresponding to the 2P1/2 → 4I9/2 transition. A study of the upconversion mechanisms has been carried out that includes the upconversion emission dependence on the wavelength and intensity of the pumping light together with a comparison of the luminescence decays after infrared excitation and after direct one photon excitation of the emitting levels. The results indicate that two- and three-body energy transfer upconversion processes are responsible for emissions from levels 4G7/2–4G9/2 and 4D3/2 respectively, while level 2P1/2 is populated by either energy transfer upconversion or excited state absorption depending on the pumping wavelength. 相似文献
9.
M. Malinowski R. Piramidowicz Z. Frukacz G. Chadeyron R. Mahiou M. F. Joubert 《Optical Materials》1999,12(4):409-423
Emission from the high lying excited states, energy transfer, and upconversion processes are investigated in YAlO3:Ho3+. Selectively excited emission spectra in the range from 300 to 800 nm starting from the 3D3, 3G5, 5F3, 5S2 and 5F5 multiplets were measured at 15 K. This, together with the detailed absorption and excitation measurements at 15 K allowed determination of the Stark energy levels of Ho3+ ions in YAlO3 up to UV energies. The 5S2 fluorescence decays were recorded as a function of temperature and Ho3+ concentration in order to investigate the process of quenching of fluorescence due to cross relaxation among two ions. Conversion of red and infrared laser radiation to green 5S2 and blue 5F3 emission is reported. Under pulsed resonant excitation of the 5F5 or 5I5 levels the upconversion was found to be due to energy transfer process between two excited ions. The photon avalanche effect was observed under cw excitation around 585 nm. 相似文献
10.
Zhengwen Yang Hangjun WuJiayan Liao Wucai LiZhiguo Song Yong YangDacheng Zhou Rongfei WangJianbei Qiu 《Materials Science and Engineering: B》2013,178(15):977-981
Infrared to visible upconversion luminescence has been investigated in Er3+/Yb3+ co-doped CeO2 inverse opal. Under the excitation of 980 nm diode lasers, visible emissions centered at 525, 547, 561, 660 and 680 nm are observed, which are assigned to the Er3+ transitions of 2H11/2 → 4I15/2 (525 nm), 4S3/2 → 4I15/2 (547, 561 nm), 4F9/2 → 4I15/2 (660 and 680 nm), respectively. The effect of photonic band gap on the upconversion luminescence intensity was also obtained. Additionally, the upconversion luminescence mechanism was studied. The dependence of Er3+ upconversion emission intensity on pump power reveals that it is a two-photon excitation process. 相似文献
11.
《Optical Materials》2014,36(12):2394-2399
Upconversion photoluminescence (PL) properties of single Y2O3 nanoparticles doped with Yb and Er (Y2O3:Yb,Er) with a Ag over-layer is studied. We traced the PL and light scattering images of individual nanoparticles by changing the thickness of a Ag over-layer. When the Ag thickness is relatively small and only the upper part of a nanoparticle is covered by Ag (Ag half-shell), the PL is strongly enhanced. On the other hand, when the Ag thickness is increased and a continuous Ag over layer is formed, the enhancement factor decreases. From the correlation between the enhancement factors of the upconversion PL and scattering intensities as well as the change of the PL lifetime, the mechanism of the PL enhancement is discussed. 相似文献
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13.
Kozlowski G Zaumseil P Schubert MA Yamamoto Y Bauer J Schülli TU Tillack B Schroeder T 《Nanotechnology》2012,23(11):115704
We study the growth and relaxation processes of Ge crystals selectively grown by chemical vapour deposition on free-standing 90 nm wide Si(001) nanopillars. Epi-Ge with thickness ranging from 4 to 80 nm was characterized by synchrotron based x-ray diffraction and transmission electron microscopy. We found that the strain in Ge nanostructures is plastically released by nucleation of misfit dislocations, leading to degrees of relaxation ranging from 50 to 100%. The growth of Ge nanocrystals follows the equilibrium crystal shape terminated by low surface energy (001) and {113} facets. Although the volumes of Ge nanocrystals are homogeneous, their shape is not uniform and the crystal quality is limited by volume defects on {111} planes. This is not the case for the Ge/Si nanostructures subjected to thermal treatment. Here, improved structure quality together with high levels of uniformity of the size and shape is observed. 相似文献
14.
《Materials Chemistry and Physics》2006,95(2-3):264-269
Transparent 45SiO2–25Al2O3–5CaO–10NaF–15CaF2 glass ceramics doped with different content of erbium ion (Er3+) were prepared. X-ray diffraction (XRD) and transmission electron microscope (TEM) analyses evidenced the spherical CaF2 nanocrystals homogeneously embedded among the glassy matrix. With increasing of Er3+ content, the size of CaF2 nanocrystals decreased while the number density increased. The crystallization kinetics studies revealed that CaF2 crystallization was a diffusion-controlled growth process from small dimensions with decreasing nucleation rate. Er3+ could act as nucleating agent to lower down crystallization temperature, while some of them may stay at the crystal surfaces to retard the growth of crystal. Intense red and weak green upconversion emissions were recorded for glass ceramics and their intensities increased with the increasing of Er3+ content under 980 nm excitation. However, the concentration quenching effect appeared when Er3+ doping reached 2 mol%. These results could be attributed to the change of ligand field of Er3+ ions due to the incorporation of Er3+ ions into precipitated fluoride nanocrystals. 相似文献
15.
Glasses of the K2OZnOAl2O3SiO2 system co-doped with Eu2O3 and Yb2O3 were prepared by the melt-quenching technique. Transparent zincite (ZnO) glass–ceramics were obtained by secondary heat-treatments at 680–860 °C. At 860 °C, traces of Eu oxyapatite appeared in addition to ZnO nanocrystals. The average crystal size obtained from the X-ray diffraction data was found to range between 14 and 35 nm. Absorption spectra of the initial glasses are composed of an absorption edge and absorption bands due to electronic transitions of Eu3+ ions. With heat-treatment, the absorption edge pronouncedly shifts to the visible spectral range. The luminescence properties of the glass and glass-ceramics were studied by measuring their excitation and emission spectra at 300, 78, and 4.2 K. Strong red emission of Eu3+ ions dominated by the 5D0–7F2 (612 nm) electric dipole transition was detected. Changes in the luminescence properties of the Eu3+-related excitation and emission bands were observed after heat-treatments at 680 °C and 860 °C. The ZnO nanocrystals showed both broad luminescence (400–850 nm) and free-exciton emission near 3.3 eV at room temperature. The upconversion luminescence spectrum of the initial glass was obtained under excitation of the 976 nm laser source. 相似文献
16.
Yb3+-Tm3+-Tb3+-codoped YF3 and NaYF4 nanocrystals (NCs) were synthesized using a simple hydrothermal method. Under 980 nm excitation, violet and ultraviolet upconversion (UC) emissions of 5D3 --> 7FJ (J = 6, 5, 4) and 5D4 --> 7FJ (J = 6, 5, 4, 3) of Tb3+ ions were observed with the fluoride NCs. In the Yb-Tm-Tb codoped NCs, energy transfer (ET) processes from Tm3+ to Tb3+ were proposed to be the main mechanisms for the UC emissions of Tb3+ ions. They are more efficient than the phonon assisted cooperative sensitization of the Yb3+ couple proposed previously for similar material system. The analysis of power dependence indicated that populating the 5D4 level of the Tb3+ ions was a four photon UC process, which demonstrated the existence of the two step ET process of Yb3+ --> Tm3+ --> Tb3+. It was also found that UC luminescence properties of Tb3+ ions were sensitive to crystal structures. 相似文献
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19.
Tetragonal rare-earth ions codoped LiScF4 nanocrystals have been synthesized by a modified solvothermal method. The results revealed that the phase and morphology can be tailored through varying the synthesis conditions, such as reaction temperature and time. Meanwhile, the UC fluorescence emission spectra were measured. It turned out that the UC emission intensity can be significantly influenced by reaction temperature and time. Different from the NaYF4:20%Yb3+,2%Er3+ nanocrystals that usually emit green emission, yellow color emission can be observed in the LiScF4:20%Yb3+,2%Er3+ samples under 980 nm excitation, which illustrates that the obtained new phase LiScF4 is suitable as a promising host for efficient UC fluorescence generation and tunable UC emission spectra. Moreover, the UC mechanism was investigated in detail. 相似文献
20.
An analytical model of cw quasi-three-level lasers that includes the influence of energy-transfer upconversion (ETU) has been developed. The results of the general output modeling were applied to a laser with Gaussian beams, and rigorous numerical calculations have been made to study the influence of ETU on threshold, output power, spatial distribution of population-inversion density, and fractional thermal loading. The model was applied to a laser operating at 946 nm in Nd:YAG, where the dependence of laser-beam size on laser performance was investigated in particular. A simple model for the degradation of laser-beam quality from a transversally varying saturated gain is proposed that is in good agreement with measurements of the laser in a plane-plane cavity. 相似文献