Multicolor up-conversion emissions of Tm3+/Er3+/Yb3+ tri-doped YF3 phosphors

Tm3+/Er3+/Yb3+ tri-doped yttrium fluoride (YF3) phosphors were prepared by a facile hydrothermal method. X-ray topographic analysis found that the phosphors were crystallized products. Their sizes and morphologies were characterized by scanning electron microscopy (SEM, Hitachi S-4800), which indicated that most of the YF3 phosphors were hundreds of nanometers in size. Up-conversion (UC) spectra were recorded under 980-nm diode laser excitation at room temperature with a fluorescence spectrometer (Hitachi F-4500). Plenty of UC emissions of Tm3+ and Er3+ were observed from ultraviolet to red. For Tm3+ ions, a five-photon process (approximately 291 nm and approximately 347 nm), a four-photon process (approximately 362 nm and approximately 452 nm), and a three-photon process (approximately 475 nm) were identified in the UC spectra. The UC emissions from the Er3+ were: approximately 380 nm, approximately 408 nm, approximately 521 nm, approximately 537 nm, and approximately 652 nm. Therefore, cyan-white light can be observed by the naked eye at 980-nm excitation, even under low excitation power density. By comparing the UC spectra of the phosphors annealed at different temperatures, we found that the intensity of the UC luminescence increased as annealing temperature increased. Furthermore, the spectral dependencies on Tm3+ doped concentrations were studied. The energy transfer processes and fluorescence dynamics in the tri-doped system are currently being investigated.     

Temperature-dependent light upconversion and thermometric properties of Er3+/Yb3+-codoped SrMoO4 sintered ceramics

Journal of Materials Science - A series of Sr1?x?yErxYbyMoO4 phosphor compositions codoped with Er3+ (x?=?1 mol%) and varying Yb3+...     

Er3+/Tm3+/Yb3+共掺氟氧化物玻璃的上转换白光性质

采用高温固相法制备了Er3+/Yb3+、Tm3+/Yb3+和Er3+/Tm3+/Yb3+共掺杂的氟氧化物玻璃SiO2-Al2O3-Na2O-ZnF2,研究了980nm近红外激光激发下的上转换发光性质。研究表明,Er3+/Yb3+共掺样品呈现了上转换绿光和红光发射,Tm3+/Yb3+共掺样品呈现了强的上转换蓝光发射和弱的红光发射,Er3+/Tm3+/Yb3+三掺样品呈现了上转换白光发射。对上转换发光强度和激光功率的研究表明上转换绿光和红光发射是两光子吸收过程,上转换蓝光发射是三光子吸收过程。     

Synthesis of colloidal upconverting NaYF4: Er3+/Yb3+ and Tm3+/Yb3+ monodisperse nanocrystals

The synthesis, characterization, and spectroscopy of upconverting lanthanide-doped NaYF4 nanocrystals (NCs) is presented. The monodisperse cubic NaYF4 NCs were synthesized via a thermal decomposition reaction of trifluoroacetate precusors in a mixture of technical grade chemicals, octadecene and the coordinating ligand oleic acid. In this straightforward method, the dissolved precursors are added slowly to the reaction solution through a stainless-steel canula resulting in highly luminescent nanocrystals with an almost monodisperse particle size distribution. The NCs were characterized through the use of transmission electron microscopy, selected area electron diffraction, 1H NMR, powder X-ray diffraction, and high-resolution luminescence spectroscopy. The NaYF4 NCs are capable of being of dispersed in nonpolar organic solvents thus forming colloidally stable solutions. The colloids of the Er3+, Yb3+ and Tm3+, Yb3+ doped NCs exhibit green/red and blue upconversion luminescence, respectively, under 980 nm laser diode excitation with low power densities.     

Influences of Er3+ content on structure and upconversion emission of oxyfluoride glass ceramics containing CaF2 nanocrystals

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.     

Er3+/Yb3+ codoped oxyfluoride borosilicate glass ceramic containing NaYF4 nanocrystals for amorphous silicon solar cells

Transparent oxyfluoride borosilicate glass ceramic containing cubic NaYF₄ nanocrystals were successfully fabricated. The cubic NaYF₄ nanocrystals with average size of 30 nm were precipitated in the glass matrix, which was confirmed by the X-ray diffraction and TEM results. In comparison with the as-made glass, significant enhancement of upconversion luminescence is observed in the Er³⁺/Yb³⁺ codoped transparent glass ceramic, which may be due to the variation of coordination environment of Er³⁺ and Yb³⁺ ions after crystallization. The high transparency, intense upconversion luminescence and the simple, low-cost fabrication process make this material exhibiting potential applications in the fields of amorphous silicon solar cells.     

Ultraviolet upconversion fluorescence of Er3+ in Yb3+/Er3+-codoped Gd2O3 nanotubes

Under 980 nm excitation, room-temperature ultraviolet (UV) upconversion (UC) emissions of Er3+ from the 4G(9/2), 2K(13/2), and 2P(3/2) states were observed in Gd2O3:Yb3+/Er3+ nanotubes, which were synthesized via a simple wet-chemical route at low temperature and ambient pressure followed by a subsequent heat treatment at 800 degrees C. The experimental results exhibited that these UV emissions came from four-photon UC processes. In the Gd2O3:Yb3+/Er3+ nanocrystals, the energy transfers (ETs) from Yb3+ to Er3+ played important roles in populating the high-energy states of Er3+ ions. This material provides a possible candidate for building UV compact solid-state lasers or fiber lasers.     

Size dependent ultraviolet upconversion in single YF3:Yb3+/Tm3+ particles

Yb3+-Tm3+ codoped YF3 bulk material was synthesized through a facile high-temperature calcinations method. By grinding and selecting, the particles with different desired sizes in microns were obtained. Under 980 nm excitation, optical upconversion (UC) from near-infrared (NIR) to ultraviolet (UV) was studied for each group of particles for the effect of their size on UC. Comparing with the bulk sample, the micro-size particles exhibited strong ability for NIR-to-UV UC. With the particle size decreasing from 800 microm to 20 microm, their UV emission intensities increased rapidly. Two possible mechanisms were proposed and discussed for clarifying the small size effect (SSE).     

OH- 对 Tm3+/Yb3+ 共掺碲酸盐玻璃上转换发光的影响

研究了Tm3 /Yb3 共掺碲酸盐玻璃的Raman光谱、红外光谱和上转换发光光谱,分析了OH-对Tm3 上转换发光的影响。结果表明,氧氯碲酸盐玻璃的声子能量高于氧氟碲酸盐玻璃的声子能量,但是Tm3 /Yb3 共掺氧氟碲酸盐玻璃的上转换发光强度高于Tm3 /Yb3 共掺氧氯碲酸盐玻璃。分析认为这主要是由于OH-的影响,在氧氟碲酸盐玻璃中OH-的浓度较低,导致Tm3 的荧光寿命高,从而提高Tm3 的上转换发光。在一定程度上,OH-对Tm3 上转换发光的影响大于声子能量对Tm3 上转换发光的影响。研究结果有助于进一步提高Tm3 的发光效率。     

Er3+单掺与Er3+/Yb3+共掺Y2SiO5的上转换发光

报道了一种新的上转换发光材料X2型Y2SiO5:Er, Yb并研究了Yb3 浓度和泵浦功率对样品的上转换发光特性的影响:(1)随着Yb3 浓度的增加,绿、红光发射均呈先增强后减弱的变化,但相对于绿光发射,红光发射受Yb3 浓度的影响更剧烈,并且当12%(摩尔分数)Yb3 时,可以得到很纯的红光发射;(2)上转换发光强度与泵浦功率的关系表明,双光子吸收贡献样品的上转换发射.此外,讨论了可能的上转换机制.认为随着Yb3 浓度增加,Er3 的激发态吸收、Yb3 到Er3 的能量传递和Er3 的交叉弛豫对上转换发光的作用依次逐渐加强.     

Synthesis and upconversion luminescence properties of CaF2:Yb3+/Tm3+ microspheres

CaF2:Yb3+/Tm3+ microspheres were synthesized by using a simple hydrothermal method. Their structures and morphologies were characterized by X-ray diffraction (XRD) and field-effective scanning electron microscopy (FESEM). The microspheres were formed from a large number of nanospheres with almost the same diameter after annealing. The growth mechanism of the microspheres was discussed. Strong ultraviolet (UV) and blue upconversion (UC) emission from the CaF2 microspheres was observed under 980 nm excitation. The enhancement of the UV UC emission was attributed to the size effect of the nanoscale particles.     

Tm3+/Er3+/Yb3+-codoped oxyhalide tellurite glasses as materials for three-dimensional display

Blue, green and red emissions through frequency upconversion and energy transfer processes in Tm³⁺/Er³⁺/Yb³⁺-codoped oxyhalide tellurite glass under 980 nm excitation are investigated. The intense blue (476 nm), green (530 and 545 nm) and red (656 nm) emissions are simultaneously observed at room temperature. The blue (476 nm) emission was originated from the ¹G₄→³H₆ transition of Tm³⁺. The green (530 and 545 nm), and red (656 nm) upconversion luminescences were identified from the ²H_11/2→⁴I_15/2, ⁴S_3/2→⁴I_15/2, and ⁴F_9/2→⁴I_15/2 transitions of Er³⁺, respectively. The energy transfer processes and possible upconversion mechanisms are evaluated.     

Ion-exchanged waveguide lasers in Er3+/Yb3+ codoped silicate glass

We investigated an Er(3+)/Yb(3+) codoped silicate glass as a host material for waveguide lasers operating near 1.5 mum. Spectroscopic properties of the glass are reported. Waveguide lasers were fabricated by K(+)-ion exchange from a nitrate melt. The waveguides support a single transverse mode at 1.5 mum. An investigation of the laser performance as a function of the Yb:Er ratio was performed, indicating an optimal ratio of approximately 5:1. Slope efficiencies of as great as 6.5% and output powers as high as 19.6 mW at 1.54 mum were realized. The experimental results are compared with a waveguide laser model that is used to extract the Er(3+) upconversion coefficients and the Yb(3+)-Er(3+) cross-relaxation coefficients. The results indicate the possibility of obtaining high-performance waveguide lasers from a durable silicate host glass.     

Broadband emission from Ce3+/Mn2+/Yb3+ tri-doped oxyfluoride glasses for glass greenhouse

In this work, a kind of oxyfluoride glasses tri-doped with Ce³⁺/Mn²⁺/Yb³⁺ ions was prepared by a simple and fast high temperature melting method. Under excitation with 300 nm light, two meaningful broad band emissions (ranged from 340 to 500 nm and 510–700 nm) were obtained, which matched well with the absorption of the chlorophylls. Under near-infrared (980 nm) excitation, an abnormal up-conversion luminescence was demonstrated in the oxyfluoride glasses by the energy transfer from Yb³⁺ to Mn²⁺. In addition, the up-conversion emission has a red shift along with the increase of the doping concentration of Mn²⁺, which would contribute to match the action spectrum of photosynthesis better. Our materials will be favored to extend the utilization of solar energy in glass greenhouse for plant cultivation.     

Synthesis and spectroscopic characterization of Ho3+/Tm3+/Pr3+ doped fluorophosphate glass

Fluorophosphate glass triply doped with Ho³⁺/Tm³⁺/Pr³⁺ has been synthesized. 2.86, 2 and 1.47 μm emissions have been successfully obtained from the present glass pumped by conventional 800 nm LD. The corresponding energy transfer mechanisms and microparameters are discussed and analyzed according to the photoluminescence performance and absorption measurements. Tm³⁺ ions can absorb the pumping energy and transfer it to Ho³⁺ and Pr³⁺ ions. Large energy transfer coefficient from Ho³⁺ to Pr³⁺ ions (8.22 × 10^?39 cm⁶/s) has been obtained based on the Förster-Dexter theory. The results suggest Ho³⁺/Tm³⁺/Pr³⁺ triply doped fluorophosphate glass is a promising candidate for efficient mid-infrared laser.     

Synthesis and upconversion luminescence of uniform beta-NaYF4:Yb3+/Tm3+ hexagonal nanoplates

Yb3+ and Tm3+-codoped hexagonal-phase NaYF4 powders were prepared by a facile hydrothermal method. The results of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) showed that the as-prepared powders were well crystallized nanoplates with high size-uniformity. Under the excitation from a 980 nm laser diode, upconversion (UC) emissions centered at approximately 291 nm (1I6 --> 3H6), approximately 346 nm (1I6 --> 3F4), approximately 361 nm (1D2 --> 3H6), approximately 451 nm (1D2 --> 3F4), approximately 474 nm (1G4 --> 3H6), approximately 644 nm (1G4 --> 3F4), and approximately 799 nm (3H4 --> 3H6) were observed in the sample. Furthermore, the intensity dependence of UC emissions on excitation power was measured. The results indicated that populating the 1I6, 1D2, 1G4, and 3H4 states were five-photon, four-photon, three-photon, and two-photon UC processes, respectively.     

Yb3+ concentration dependence of upconversion luminescence in Y2Sn2O7:Yb3+/Er3+ nanophosphors

Pyrochlore Y₂Sn₂O₇ nanophosphors codoped with Er³⁺ (fixed 2 at.%) and Yb³⁺ ions (2–16 at.%) were synthesized via hydrothermal process followed by heat treatment. We investigate the infrared-to-visible upconversion (UC) luminescence properties of Er–Yb codoped Y₂Sn₂O₇. Upon 980 nm excitation at room temperature, green (at ~522 and 544 nm) and red (at ~661 nm) UC emissions were observed, which are ascribed to the (²H_11/2, ⁴S_3/2) → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions, respectively. It has been found that the Yb³⁺-doping concentrations have greatly influenced on the UC luminescence intensity and the emission ratio of the red and green in Y₂Sn₂O₇:Yb³⁺/Er³⁺ nanophosphors. The tunable emission is due to the energy back transfer from Er³⁺ to Yb³⁺ and the cross relaxation between the two neighboring Er³⁺ ions. It is expected that the achieved single and intense red emission band may have potential application for in vivo bioimaging.     

PbO对Tm3+/Ho3+/Yb3+共掺碲酸盐玻璃三基色上转换发光的影响

用高温熔融法制备了Tm3+/Ho3+/Yb3+共掺碲酸盐玻璃,在TeO2-ZnO-La2O3玻璃组分的基础上,引入声子能量较低的PbO,研究了PbO对基质样品拉曼光谱以及Tm3+/Ho3+/Yb3+共掺样品上转换发光光谱的影响.结果表明,随着PbO含量的增加,样品的最大声子能量下降比较明显,同时样品的声子态密度也有减小趋势;在975nm波长激光二极管(LD)激励下,随着PbO含量的增加,Tm3+/Ho3+/Yb3+共掺样品上转换蓝光(480nm)、绿光(546nm)和红光(662nm)的发光强度都有明显增强,且PbO的引入对上转换蓝光发光强度的影响要大于其对绿光和红光的影响.