Yb Energy Transfer Research Articles

An anhydrous precursor approach to BaYF5-based upconverting nanocrystals

With an objective to have easy access to high quality BaYF5 matrix, we report here new anhydrous precursors of barium and yttrium which show a good compatibility in terms of co-thermal decomposition. These complexes not only fill the void of precursors for Ba-based upconverting (UC) nanomaterials but also provide a way to minimize the –OH concentration around these nanocrystals (NCs) to enhance their UC efficiency without requiring the usual core-shell structure. The precursors and the BaYF5 NCs co-doped with Yb3+/Tm3+ ions were thoroughly characterized. The NCs were studied for upconversion properties and preliminary results are presented here. On the basis of these results, a mechanism for the energy transfer in Yb–Tm system is proposed.

Dual vis-NIR emissive bimetallic naphthoates of Eu-Yb-Gd: a new approach toward Yb luminescence intensity increase through Eu → Yb energy transfer.

Homo- and heteroligand mono-, bi-, and trimetallic lanthanide naphtoates EuxYbyGd1-x-y(naph)3(Phen)n (n = 0, 1) were obtained and thoroughly investigated. Homoligand naphthoates of the new phase were obtained as anhydrous powders from water. The photophysical properties of the obtained compounds were studied in detail. The first example of Eu-to-Yb energy transfer was found in these systems. Careful selection of the metal ratio allowed a dual vis-NIR emissive complex with a ytterbium quantum yield of 1.5% to be obtained.

Dual red-NIR luminescent Eu Yb heterolanthanide nanoparticles as promising basis for cellular imaging and sensing

The present work introduces ternary Ln(III) (Ln = Eu, Yb, Lu) complexes with thenoyltriflouro1,3-diketonate (TTA-) and phosphine oxide derivative (PhO) as building blocks for core-shell nanoparticles with both Eu(III)- or Yb(III)-centered luminescence and the dual Eu(III)-Yb(III)-centered luminescence. Solvent-mediated self-assembly of the complexes is presented herein as the procedure for formation of EuLu, EuYb and YbLu heterometallic or homometallic cores coated by hydrophilic polystyrenesulfonate-based shells. Steady state and time resolved Eu-centered luminescence in homolanthanide and heterolanthanide EuLu and EuYb cores is affected by Eu → Eu and Eu → Yb energy transfer due to a close proximity of the lanthanide blocks within the core of nanoparticles. The Eu → Yb energy transfer is highlighted to be the reason for the enhancement of the NIR Yb-centered luminescence. Efficient cellular uptake, low cytotoxicity towards normal and cancer cells, and sensing ability of EuYb nanoparticles on lomefloxacin additives via both red and NIR channels make them promising as cellular imaging agents and sensors.

Devitrification Behavior of Sol-Gel Derived ZrO2-SiO2 Rare-Earth Doped Glasses: Correlation between Structural and Optical Properties

Optical and structural properties of glasses and glass-ceramics (GC) obtained by different heat-treatment of Tb and Tb-Yb doped sol-gel derived 30ZrO2-70SiO2 materials were investigated. A glass was formed after treatment at 700 °C whereas devitrification of the media after the treatment at 1000 and 1100 °C, led to the formation of GC containing up to three different crystalline phases, namely, tetragonal ZrO2, Yb-disilicate and cristobalite. The modification of the optical properties through the heat treatment was caused by redistribution of the rare earth elements (REE) among the different phases: both Tb and Yb entered the t-ZrO2 lattice, Yb can also be present in the form of a Yb2Si2O7 crystal. Devitrification led to an increase in Tb→Yb energy transfer efficiency as compared to the glass, though it was higher in the samples heat-treated at 1000 °C than in those treated at 1100 °C. The most intensive Yb3+ luminescence, induced by the energy transfer from the Tb3+ ion, was observed at the interface between t-ZrO2 and the glassy phases, due to the high concentration of REE in this area caused by the inability of ZrO2 to accept larger amounts of the REE. The mechanisms of the Tb→Yb energy transfer vary between different phases of the GC. The results obtained in this study are important for the development of spectral down-converters for potential solar energy applications based on Tb-Yb co-doped glass-ceramics.

LMCT facilitated room temperature phosphorescence and energy transfer in substituted thiophenolates of Gd and Yb.

To obtain luminescent lanthanide complexes with a low energy LMCT state the 2-(2'-mercaptophenyl)benzothiazolates, Ln(SSN)3, and 2-(2'-mercaptophenyl)benzoxazolates, Ln2(OSN)6 (Ln = Gd, Yb), were synthesized by the reaction of amides Ln[N(SiMe3)2]3 with respective thiophenols. Ytterbium complexes were structurally characterized by X-ray diffraction analysis. Cyclic voltammetry revealed that the deprotonated mercaptophenyl ligands have significantly lower oxidation potentials than their phenoxy analogues and some β-diketones. The photophysical properties of Gd and Yb compounds were studied both in solution and in the solid state. The fluorescence spectra of the compounds in solution display the bands of the keto and enol forms of the ligands. No energy transfer from the organic part to Yb3+ has been detected in solutions of both Yb complexes, whereas in solids an intense metal-centered emission in the near infrared region was observed. The solid Gd compounds exhibited room temperature phosphorescence caused by unusually efficient intersystem crossing facilitated by the essentially reducing properties of OSN and SSN ligands. To explain the sensitization process occurring in solids Yb2(OSN)6 and Yb(SSN)3 a specific non-resonant energy transfer mechanism via a ligand to metal charge transfer state has been proposed. Based on the Yb derivatives, NIR-emitting OLEDs with 860 μW cm-2 maximal irradiance were obtained. Their Gd counterparts showed bright electrophosphorescence (up to 1350 cd m-2) in the devices containing doped emission layers.

Two micrometer fluorescence emission and energy transfer in Yb3+/Ho3+ co‐doped lead silicate glass

AbstractEnhanced 2.0 μm and visible up‐conversion emissions from Ho3+ via Yb3+ sensitization in lead silicate glasses have been obtained under the excitation of 980‐nm laser diode. The possible energy transfer mechanism has been analyzed based on the photoemission spectroscopy and lifetime measurement. The lifetime of Ho3+: 5I7 laser upper level has also been measured. Based on the absorption spectra, Judd–Ofelt parameters, spontaneous emission probability, the absorption, emission cross sections, and gain coefficients have been calculated and analyzed. The results indicate that the Yb3+/Ho3+ co‐doped lead silicate glass has potential application in mid‐infrared wavelengths.

A broadening temperature sensitivity range with a core-shell YbEr@YbNd double ratiometric optical nanothermometer.

The chemical architecture of lanthanide doped core-shell up-converting nanoparticles can be engineered to purposely design the properties of luminescent nanomaterials, which are typically inaccessible to their homogeneous counterparts. Such an approach allowed to shift the up-conversion excitation wavelength from ∼980 to the more relevant ∼808 nm or enable Tb or Eu up-conversion emission, which was previously impossible to obtain or inefficient. Here, we address the issue of limited temperature sensitivity range of optical lanthanide based nano-thermometers. By covering Yb-Er co-doped core nanoparticles with the Yb-Nd co-doped shell, we have intentionally combined temperature dependent Er up-conversion together with temperature dependent Nd → Yb energy transfer, and thus have expanded the temperature response range ΔT of a single nanoparticle based optical nano-thermometer under single ∼808 nm wavelength photo-excitation from around ΔT = 150 K to over ΔT = 300 K (150-450 K). Such engineered nanocrystals are suitable for remote optical temperature measurements in technology and biotechnology at the sub-micron scale.

Emission sensitization processes involving Nd3+ in YAG

The paper investigates the characteristics of sensitization processes of Nd3+ emission in YAG ceramics under broad band pumping by co-doping with Cr3+ and the prospect of using Nd3+ and Cr3+ for sensitization of emission of Yb3+. It is evidenced that the energy transfer from Cr3+ to Nd3+ involves both direct and weak migration-assisted processes and is thus dependent on the concentrations of both species. It is also found that the ion–ion interaction responsible for the direct transfer contains besides the dipole–dipole coupling strong superexchange contribution that dominates the transfer to the Nd3+ ions up to the third coordination sphere and has major implication in sensitization. Investigation of (Cr, Nd, Yb)-doped YAG ceramics shows that Cr3+ can sensitize the emission of Yb3+ both via the chain Cr–Nd–Yb or by direct Cr–Yb energy transfer. The prospect of utilization of these processes in the solar-pumped laser is discussed.

Bright and tunable up-conversion luminescence through cooperative energy transfer in Yb3+, Tb3+and Eu3+co-doped LaPO4nanocrystals

Lanthanum phosphate LaPO4 nanocrystals doped with Yb3+, Tb3+ and Eu3+ ions, were synthesised by a hydrothermal method followed by annealing at 900 °C. These materials exhibited bright and tunable up-conversion luminescence from green to red colour as the result of Tb3+ and Eu3+ ions emission. The structural and morphological properties of the products were analysed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The spectroscopic properties of LaPO4:Yb3+,Tb3+,Eu3+ nanocrystals were investigated using excitation and emission spectra. Also the luminescence decays were measured showing an unusually long rise time of the luminescence as a result of cooperative energy transfer mechanisms (CET) followed by energy migration. Calculated energy transfer rates and efficiencies showed the effectiveness of energy transfer between Yb3+, Tb3+ and Eu3+ ions.

Light emission at 2 μm from Ho–Tm–Yb doped silicate glasses

The 2.0 μm emission properties and thermal stability of Yb–Tm–Ho triply-doped silicate glass are investigated. The characteristic temperatures, absorption spectrum and fluorescence spectra of the glasses are measured. Intensive emission near 2.0 μm is observed upon excitation at 980 nm and the corresponding mechanisms are discussed. Based on the measured absorption spectra, the absorption and emission cross sections, the Judd–Ofelt parameters and radiative properties are calculated and discussed. The predicted spontaneous transition probability for Ho 3+: 5I 7 → 5I 8 transition in silicate glass is 58.05 s −1. The results indicate that the energy transfer in Yb 3+ → Tm 3+, Yb 3+ → Ho 3+, Tm 3+ → Ho 3+ is efficient and the Yb–Tm–Ho triply-doped silicate glass is a promising 2.0 μm laser glass material.

Spectroscopic properties and energy transfer in Yb 3+–Ho 3+ co-doped germanate glass emitting at 2.0 μm

A new kind of germanate glass co-doped with Yb 3+–Ho3 + was prepared. The J-O parameters were calculated to be Ω 2 = (6.59 ± 0.21) × 10 − 20 cm 2, Ω 4 = (2.77 ± 0.36) × 10 − 20 cm 2, and Ω 6 = (1.90 ± 0.25) × 10 − 20 cm 2. The little overlap between the absorption cross section and stimulated emission cross section indicates a non-resonant energy transfer process. The calculation demonstrates that the energy transfer between Yb 3+ and Ho 3+ is one-phonon assisted in a great measure. The gain coefficient of Ho 3+ at 2.0 μm was also calculated. The fluorescence measurement shows the Yb 3+ co-doping enhances the 2.0 μm emission remarkably.

Sensitized Yb3+ emission in (Nd, Yb):Y3Al5O12 transparent ceramics

The characteristics of Nd→Yb energy transfer in (Nd, Yb):Y3Al5O12 (YAG) transparent ceramics, obtained from steady state and dynamic spectral studies on different single doped and codoped samples, prepared by solid state synthesis, are presented. The Yb3+ emission in codoped (Nd, Yb):YAG samples under cw excitation of the donors (Nd3+) revealed efficient energy transfer to Yb3+ (at low temperatures too), due to the overlap of the Nd3+ F43/2→I49/2 emission and Yb3+ F27/2→F25/2 absorption. From the global decays of the Nd3+ F43/2 level in single and codoped samples, the transfer efficiencies were estimated; they increase with Yb3+ content reaching ∼93% for 1 at. % Nd, 5 at. % Yb:YAG sample. The mechanisms and parameters of the Nd→Yb energy transfer were inferred from the Nd3+ decays in the codoped samples, after the separation of the self-quenching inside the donors (Nd3+) from the transfer to acceptors (Yb3+). It was proved that the Nd→Yb energy is resonant and dominated by dipole-dipole interactions. Due to the large transfer efficiencies, (Nd, Yb):YAG ceramic could be a promising material for Yb3+ emission under pumping in strong Nd3+ absorption lines.

Spectroscopic properties of Yb3+/Er3+ - doped antimony-phosphate glasses for fiber amplifiers

In this paper the optical spectroscopic properties of Yb 3+ /Er 3+ co-doped antimony-phosphate glasses were investigated. The absorption and luminescence spectra were measured and the emission cross-section for 4 I 13/2 -> 4 I 15/2 transition of Er 3+ was calculated on the basis of McCumber theory. The resonant energy transfer (ET) between Yb 3+ -> Er 3+ ions was investigated pumping at 976nm. As a result of optimization of rare earth concentration the best efficiency of energy transfer in fabricated glasses was obtained for molar composition 1%Y 2 O 3 : 0.5%Er 2 O 3 . Full Text: PDF References M. Liao, Z. Duan, L.Hu, Y. Fang, L.Wen,"Spectroscopic properties of Er 3+ /Yb 3+ codoped fluorophosphate glasses", J. Lum 126 139 (2007) [CrossRef] L. Zang, H. Hu, C. Qi, F. Lin,"Spectroscopic properties and energy transfer in Yb 3+ /Er 3+ -doped phosphate glasses", Opt. Mat. 17 371 (2001) [CrossRef] J. F. Philipps, T. Töpfer, H. Ebendorff - Heidepriem, D. Ehrt, R.Sauerbrey,"Appl. Phys. B72 399 (2001)", Spectroscopic and lasing properties of Er 3+ :Yb 3+ -doped fuoride phosphate glasses [CrossRef] Y. Fang L. Hu, M. Liao L. Wen J. Alloys Comp. 457 19 (2008) Qian, C. Zhao, G.F. Yang, Z.M. Yang, Q.Y. Zhang, Z.H. Jiang"Spectroscopic properties of Er 3+ -doped Na 2 O?Sb 2 O 3 ?B 2 O 3 ?SiO 2 glasses", J. Non-Cryst. Solids 354 1981 (2008) [CrossRef] W.J. Miniscalco, R.S. Quimby,"General procedure for the analysis of Er3+ cross sections", Opt. Lett. 16 (1991) [CrossRef] Q. Qian, Q.Y. Zhang, H.F. Jiang Z.M. Yang, Z.H. Jiang,"The spectroscopic properties of Er 3+ -doped antimony?borate glasses", Physica B 405 2220 (2010) [CrossRef]

Nd → Yb energy transfer in (Nd, Yb):Y 2O 3 transparent ceramics

In the attempt to obtain new efficient laser systems, the Nd → Yb energy transfer characteristics in Y 2O 3 transparent ceramics were investigated. The spectral characteristics that assure the efficient resonant Nd 3+ → Yb 3+ energy transfer are presented, especially the overlap integral of the Nd 3+ 4F 3/2 → 4I 9/2 emission with the Yb 3+ 2F 7/2 → 2F 5/2 absorption in (Nd, Yb):Y 2O 3. The static spectral data reveal that the Nd 3+ → Yb 3+ energy transfer shows: a strong dependence on Yb 3+ content (less on Nd 3+), a small variation with temperature and the implication of both Yb 3+ sites in transfer, though only Nd 3+ in C 2 are active. From the analysis of Nd 3+ 4F 3/2 emission decays in double doped samples it is concluded that the Nd → Yb transfer for Nd ∼1 at.% is of direct type, through the dipole–dipole interaction with global energy transfer microparameter ∼ C DA,Nd – Yb ≈ 1 × 10 −38 cm 6 s −1 and transfer efficiencies up to 98% for rather low (∼5 at.%) Yb 3+ content.

Effect of Bi 2O 3 on spectroscopic properties and energy transfer in Yb 3+–Er 3+-co-doped bismuth borate glasses for 1.5 μm optical amplifiers

In this paper, the effect of Bi 2O 3 on the optical absorption and emission, energy transfer, and gain property of Yb 3+–Er 3+-co-doped bismuth borate glasses has been investigated. An increase of the emission cross-section and fluorescence lifetime of Er 3+ ions around 1.5 μm with Bi 2O 3 content was shown. The increase of Bi 2O 3 content is also beneficial to obtaining a large absorption cross-section at 980 nm and increasing the energy transfer from Yb 3+ to Er 3+. Furthermore, in the 45Bi 2O 3–55B 2O 3 glass, gain curve is almost flat in the range from 1.53 to 1.60 μm. The results indicate that the Yb 3+–Er 3+-co-doped bismuth borate glasses have good prospect as a candidate of gain medium for 1.5 μm broadband amplifier.

Energy transfer in Yb^3+-Er^3+-codoped bismuth borate glasses

The mechanism of energy transfer from Yb3+ to Er3+ ions has been studied in bismuth borate glasses with a serial Yb3+ concentration. The analysis of the donor fluorescence decay with a low concentration has been used to determine the multipole character of the energy transfer. The energy-transfer microparameters were determined and used to calculate the migration-assisted energy-transfer rates on the basis of the hopping model, which are in agreement with those obtained by fitting the fluorescence decay curves. An efficient energy transfer from Yb3+:2F5/2 to Er3+:I11/2 in the bismuth borate glasses has been demonstrated.

Thermal lens study of energy transfer in Yb^3+/Tm^3+-co-doped glasses

Energy transfer (ET) and heat generation processes in Yb(3+)/Tm(3+)-co-doped low-silica calcium-aluminosilicate glasses were investigated using thermal lens and photoluminescence measurements. Stepwise ET processes from Yb(3+) to Tm(3+), with excitation at 0.976 mum, produced efficient emission in the mid-infrared range at around 1.8 mum, with high fluorescence quantum efficiency (~0.50) and relatively low thermal loading (</=0.42). An equation was deduced for the description of the thermal lens results which provided the absolute value of the ET efficiency and optimal Tm3+ concentration that result in population of the 1.8 mum Tm(3+) emitting level. These results suggest that the studied co-doped system would be a promising candidate for the construction of high-power diode-pumped solid-state lasers in the mid-infrared range, which are especially important for the purpose of medical procedures.

Spectral properties and energy transfer of Yb,Er:GdVO4 crystal

GdVO4 single crystal co-doped with Yb3+ and Er3+ was grown by the Czochralski method. The X-ray powder diffraction pattern of Yb,Er:GdVO4 crystal confirms that the as-grown crystal is isostructural with pure GdVO4 crystal. Its polarized absorption spectra and non-polarized fluorescence spectra were measured at room temperature. The absorption band at 984 nm for π-polarization has an FWHM of about 36 nm, which is favorable for InGaAs LD laser pumping. The spectrum properties of Er3+ in Yb,Er:GdVO4 crystal were investigated based on Judd–Ofelt theory. There is strong energy transfer from Yb3+ to Er3+ in this crystal. When excited with 980 nm radiation, this crystal emitted strong fluorescence at about 1529 nm and 552.5 nm. The total energy transfer rate and efficiency from Yb3+ to Er3+ is 3.33 ms-1 and 67%, respectively. The energy transfer between Er3+ and Yb3+ ions is a multistep transfer process, and was investigated based on a random-walk model. The investigation result shows that there is strong cooperative-sensitization effect from Yb3+ to Er3+, which is the main upconversion energy-transfer process in this crystal.

Photoinduced Ru–Yb energy transfer and sensitised near-IR luminescence in a coordination polymer containing co-crystallised [Ru(bipy)(CN)4]2−and Yb(iii) units

Co-crystallisation of the anionic cyanometallate chromophore [Ru(bipy)(CN)4]2- with Yb(III) provides coordination polymers or oligomers containing Ru-CN-Yb bridges; in [K(H2O)4][Yb(H2O)6][Ru(bipy)(CN)4]2.5H2O Ru-->Yb energy-transfer (k > 5 x 10(6) s(-1)) results in partial quenching of the Ru-based luminescence and sensitised near-IR luminescence from the Yb(III) unit.

On the kinetics of nonradiative energy transfer in Yb — Er phosphate glasses excited by a diode laser

The luminescence of a Yb — Er phosphate glass excited by a diode laser is studied as a function of the density of energy absorbed by a sample and the pump radiation intensity. An abrupt change in the depopulation rate of the Yb3+(2F5/2) level was observed after switching off the pump laser. This effect is explained qualitatively based on the kinetics of nonradiative energy transfer in glasses and crystals.