Upconversion Luminescence Of Tm3 Research Articles

General Synthesis of Carbon Dot-Based Composites with Triple-Mode Luminescence Properties and High Stability.

Carbon dot (CD)-based luminescent materials have attracted great attention in optical anti-counterfeiting due to their excellent photophysical properties in response to ultraviolet-to-visible excitation. Hence, there is an urgent need for the general synthesis of CD-based materials with multimode luminescence properties and high stability; however, their synthesis remains a formidable challenge. Herein, CDs were incorporated into a Yb,Tm-doped YF3 matrix to prepare CDs@YF3:Yb,Tm composites. The YF3 plays a dual role, not only serving as a host for fixing rare earth luminescent centers but also functioning as a rigid matrix to stabilize the triplet state of the CDs. Under the excitation of 365 nm ultraviolet light and 980 nm near-infrared light, CDs@YF3:Yb,Tm exhibited blue fluorescence and green room-temperature phosphorescence of CDs and upconversion luminescence of Tm3+, respectively. Due to the strong protection of the rigid matrix, the stability of CDs@YF3:Yb,Tm is greatly improved. This work provides a general synthesis strategy for achieving multimode luminescence and high stability of CD-based luminescent materials and offers opportunities for their applications in advanced anti-counterfeiting and information encryption.

Near infrared and upconversion luminescence of Tm3+-Yb3+codoped CdF2 single crystals

Tm3+, Yb3+: CdF2 single crystals with good optical quality are grown by the standard Bridgman method. The crystal structure is checked by means of X-ray diffraction analysis. Under 800 nm excitation of Tm3+ ions, the samples show an intense infrared band around 1800 nm associated with the 3F4→3H6 transition. The sample exhibit also upconverted luminescence under 975 nm laser excitation which is a signature of an efficient energy transfer between Yb3+ and Tm3+ ions. The pump power dependence of all upconversion intensities have been analyzed in accordance with a proposed upconversion mechanism. The temporal evolution curves of the upconversion emissions obtained for the lowest Tm3+ concentration sample gives longer decays and as result the highest emission upconversion intensities.

Thermosensitive Tm3+/Yb3+ co-doped oxyfluorotellurite glasses – spectroscopic and temperature sensor properties

Oxyfluorotellurite (65-x)TeO2–20ZnF2–12PbO–3Nb2O5–xTm2O3 (x = 0.5, 2 and 5) and (65-x-y)TeO2–20ZnF2–12PbO–3Nb2O5–xTm2O3–yYb2O3 (x = 0.5, y = 2 and x = 0.5, y = 5) glass systems were manufactured. Glass thermal stability was examined by means of differential thermal analysis (DTA) and some thermal stability criteria ΔT, H’ and S were determined. Absorption spectrum was utilized to prepare Judd-Ofelt (J-O) calculations and consequently oscillator strengths, intensity parameters Ω2,4,6, radiative transition probabilities, branching ratios and radiative lifetimes of luminescent levels were estimated. Emission spectra and luminescence decay curves were measured as a function of temperature in the 300–625 K range. Based on the upconversion luminescence of Tm3+ the optical temperature sensor qualities have been evaluated for Tm3+/Yb3+ co-doped sample. The fluorescence intensity ratio (FIR) between transitions 700 nm (Tm3+:3F2,3 → 3H6)/800 nm (Tm3+:3H4 → 3H6) for 975 nm excitation and 700 nm (Tm3+:3F2,3 → 3H6)/470 nm (Tm3+:1G4 → 3H6) for 803 nm excitation were determined and an adequate relative thermal sensitivity S was estimated. The significant value of relative thermal sensitivity 1.12 %K−1 was determined when NIR Yb3+ and Tm3+ emission bands were analyzed, however. Effective emission cross section was calculated for 3F4 → 3H6 potential laser transition of thulium around 1.9 μm in single-doped Tm3+ glass. Furthermore, effect of temperature on down-converted and up-converted thulium and ytterbium emission and on relaxation dynamic of involved excited states was studied in details.

Tm3+-doped Na0.5-xYb0.5+xF2+2x self-crystallization glass ceramics: Microstructure and optical thermometry properties

Tm3+-doped Na0.5-xYb0.5+xF2+2x glass ceramics were successfully synthesized by glass self-crystallization route, which were determined by X-ray diffraction, transmission electron microscopy, selected area electron diffraction, Stark splitting of emission spectra and prolonged lifetime. With subsequent heat treatment, up-conversion luminescence of Tm3+ was obviously enhanced owing to improving crystallinity of Na0.5-xYb0.5+xF2+2x nanocrystals. The temperature sensing behavior of Na0.5-xYb0.5+xF2+2x:Tm3+ glass ceramics was investigated within the 303–543 K temperature range through fluorescence intensity ratio between F2,32→H63 and G41→F43 up-conversion emission of Tm3+ excited upon 980 nm laser. The maximum relative sensitivity reaches 1.44% K-1 at 418 K, suggesting that Na0.5-xYb0.5+xF2+2x:Tm3+ glass ceramics can be used as an excellent materials for temperature sensors.

Near-infrared and upconversion luminescence of Tm3+ and Tm3+/Yb3+-doped oxyfluorosilicate glasses

Oxyfluorosilicate glasses-doped with different concentrations of Tm3+ and Tm3+/Yb3+ ions have been synthesized and characterized their absorption, photoluminescence, luminescence decay and upconversion properties. The Judd-Ofelt intensity parameters have been obtained from the absorption spectrum of Tm3+ single-doped glass and are in turn used to calculate radiative properties such as transition probabilities, branching ratios and lifetimes for the fluorescent levels of Tm3+ ions. Visible and near-infrared emission spectra of Tm3+ and Tm3+/Yb3+-doped glasses have been measured under 473 nm laser excitation. The quenching of emission intensities at higher concentrations of Tm3+ ions has been found to be due to cross-relaxation mechanisms. The Tm3+/Yb3+ co-doped glasses show upconverted emissions under 975 nm laser excitation. The mechanism of upconversion has been explained based on the pump power dependence of upconversion luminescence. The results reveal that the co-doped glasses are promising for optical fiber amplifiers operating at the relatively low-loss wavelength regions.

Tunable reddish to magenta upconversion luminescence in Tm3+-doped glass

Generation of the color-tunable reddish to magenta upconversion luminescence in Tm3 + -single-doped glasses under near-infrared (1.1 to 1.3 μm) excitation is reported. Upconversion emission in the ultraviolet, blue- and red-spectral regions due to D21-H63, D21-F43, G41-H63, G41-F43, and F2,33-H63 transitions, respectively, was observed. The dependence of upconversion emission upon excitation power and Tm3 + content was also investigated. Adjusting the excitation power and Tm3 + concentration, the overall fluorescence emission can be tuned across the reddish to magenta color in the international commission on illumination color chromaticity diagram. The CIE-1931 color coordinates move from red toward the bluish region occupying the magenta region with an increase in the excitation power.

Luminescence properties of Tm3+ ions single-doped YF3 materials in an unconventional excitation region.

According to the spectral distribution of solar radiation at the earth's surface, under the excitation region of 1150 to 1350nm, the up-conversion luminescence of Tm3+ ions was investigated. The emission bands were matched well with the spectral response region of silicon solar cells, achieved by Tm3+ ions single-doped yttrium fluoride (YF3 ) phosphor, which was different from the conventional Tm3+ /Yb3+ ion couple co-doped materials. Additionally, the similar emission bands of Tm3+ ions were achieved under excitation in the ultraviolet region. It is expected that via up-conversion and down-conversion routes, Tm3+ -sensitized materials could convert photons to the desired wavelengths in order to reduce the energy loss of silicon solar cells, thereby enhancing the photovoltaic efficiency.

Controlled synthesis and upconversion luminescence of Tm3+-doped NaYbF4 nanoparticles for non-invasion optical thermometry

The Tm3+-doped NaYbF4 upconverting nanoparticles were fabricated by a facile hydrothermal method and they were characterized by X-ray diffraction and transmission electron microscopy as well as upconversion (UC) emission spectrum. Under the irradiation of 980 nm light, the as-prepared samples exhibited bright visible UC emissions originating from the intra-4f transitions of Tm3+ ions. The pump power-dependent UC emission spectra were measured to elaborate the involved UC mechanism. Furthermore, the temperature-dependent fluorescence intensity ratio from the thermally coupled levels (3F2,3 and 3H4) of Tm3+ ions was obtained to analyze the thermometric performances of the studied compounds. It is evident that the reaction temperature can not only improve the UC emission intensity of the Tm3+-doped NaYbF4 upconverting nanoparticles, but also modify its sensor sensitivity. Meanwhile, the maximum sensor sensitivity was found to be as high as 2.1 × 10−4 K−1 with a wide temperature range of 298–778 K, suggesting its potential application for physiological temperature sensing in biological tissues and cells. Ultimately, the Judd-Ofelt theory was employed to clarify the effect of reaction temperature on the temperature sensitivity.

Nearly pure NIR to NIR upconversion luminescence in Tm3+, Yb3+ co-doped ZnO-TiO2 composite phosphor powder

Tm3+ and Yb3+ co-doped ZnO-TiO2 composite system were successfully synthesized via powder-solution mixing method and their upconversion (UC) luminescence characteristics were studied as a function of various ZnO/TiO2 mixing ratios and dopant concentrations under 980 nm laser excitation. The XRD patterns showed that the product fired at 1300 °C consisted of four phases, Zn2TiO4, TiO2, RE2Ti2O7, and RE2TiO5 (RE = Tm3+ and/or Yb3+). The NIR emission centered at 795 nm wavelength was detected as the strongest emission intensity which it was in accordance with the 3H4 → 3H6 transition of Tm3+ ion. The NIR emission intensity of the products was varied by changing ZnO-TiO2 mixing ratios, and Tm3+ and Yb3+ concentrations. The simple chemical formula equations, for interpreting the site preference of Tm3+ and Yb3+ ions in the host crystal matrix, were originated by considering the host crystal structure, its crystal arrangement, and the effect of Tm3+ and Yb3+ ions to the changes in lattice parameters of host crystal. The 1ZnO:1TiO2 (in mole) doped with 0.125 mol% Tm3+, 15 mol% Yb3+ fired at 1300 °C for 1 h was the best condition that displayed highest NIR emission intensity. The possible UC mechanism was suggested and discussed in detail.

Optical thermometry based on up-conversion luminescence of Tm3+ doped transparent Sr2YF7 glass ceramics

Tm3+/Yb3+ co-doped transparent glass ceramics (GC) containing Sr2YF7 nanocrystals were successfully manufactured by traditional melt-quenching technique. Their structural and up-conversion luminescent properties were systemically investigated through X-ray diffraction (XRD), transmission electron microscope (TEM) and a series of spectroscopy methods. Tremendously enhanced up-conversion emissions with obvious Stark splitting and prolonged luminescence lifetime were observed after crystallization. These optical spectroscopy results manifest that Tm3+ ions have incorporated into the Sr2YF7 crystalline lattice with low phonon energy (~ 400cm−1) after heat-treatment. The 3F2,3 and 3H4 levels of Tm3+ can be explored as thermally coupled energy levels (TCEL) for temperature sensing because of their befitting energy gap (~ 2000cm−1). At the same time, the population of 1G4 state of Tm3+ is indirectly originated from 3H4 one. Therefore the temperature sensing performances of Tm3+ doped Sr2YF7 GC were investigated by fluorescence intensity ratio (FIR) between 3F2,3 → 3H6 and 1G4 → 3F4 up-conversion emissions of Tm3+. Results show that the theoretical maximum value of relative sensitivity SR-max is 1.16%K−1 at 428 K, and absolute sensitivity SA keeps increasing with temperature. Such Tm3+/Yb3+ co-doped Sr2YF7 GC may be excellent candidate for optical temperature sensors.

Color Tunable and Upconversion Luminescence in Yb-Tm Co-Doped Yttrium Phosphate Inverse Opal Photonic Crystals.

For this paper, YPO4: Tm, Yb inverse opals with the photonic band gaps at 475 nm and 655 nm were prepared by polystyrene colloidal crystal templates. We investigated the influence of photonic band gaps on the Tm-Yb upconversion emission which was in the YPO4: Tm Yb inverse opal photonic crystals. Comparing with the reference sample, significant suppression of both the blue and red upconversion luminescence of Tm3+ ions were observed in the inverse opals. The color purity of the blue emission was improved in the inverse opal by the suppression of red upconversion emission. Additionally, mechanism of upconversion emission in the inverse opal was discussed. We believe that the present work will be valuable for not only the foundational study of upconversion emission modification but also the development of new optical devices in upconversion lighting and display.

Role of the stimulated radiation of Yb3+ ions in the formation of luminescence of the Y0.8Yb0.2F3:Tm3+ solid solution

A new mechanism has been proposed for the transfer of the energy of exciting laser radiation through the donor subsystem (Yb3+) to acceptors (Tm3+), which induces multiphoton transitions in the acceptor subsystem. The coherence of the induced radiation of donors is of key importance in this mechanism. An analytical dependence of the intensity of the up-conversion luminescence of Tm3+ (1G4 → 3H6) ions in the Y0.8Yb0.2F3:Tm3+ system on the pump power at the steady-state excitation by 934-nm infrared radiation of a laser diode has been obtained using the mathematical technique of the theory of Poisson processes. In contrast to known mechanisms, this dependence approximates the experimental dependence well in a wide power range (200–1200 mW). The proposed model is applicable for any system where the energy of pump radiation is transferred to acceptors through the subsystem of donor ions.

Low-phonon tellurite glass co-doped with Tm3+/Ho3+ ions for optical fibre technology

In this paper the material and optical properties of tellurite glasses co-doped with Tm 3+ /Ho 3+ ions were investigated. Near infrared luminescence at the wavelength of 2060 nm ( 5 I 7 -> 5 I 8 ) in holmium ions was obtained as a result of energy transfer between Tm 3+ and Ho 3+ ions. The energy transfer (ET) between Tm 3+ -> Ho 3+ ions was investigated pumping at 795 nm. As a result of optimization of rare earth concentration the best efficiency of energy transfer in fabricated glasses was obtained for molar composition 0.2mol%Tm 2 O 3 : 0.2mol%Ho 2 O 3 . Full Text: PDF References H. Gebavi, D. Milanese, G. Liao, Q. Chen, M. Ferraris, M. Ivanda, O. Gamulin, S. Taccheo, "Spectroscopic investigation and optical characterization of novel highlythulium doped tellurite glasses", Journal of Non-Crystalline Solids, 355 (2009) 548-555. CrossRef B.M. Walsh, "Review of Tm and Ho materials; spectroscopy and lasers", Laser Physics, 19 (2009) 855-866. CrossRef S.D. Jackson, Y. Li, "High-power broadly tunable Ho3+-doped silica fibre laser", Electron. Lett, 40 (2004) 1474?1475 CrossRef M. Wang, L. Yi, G. Wang, L. Hu, J. Zhang, "2um emission performance in Ho3+ doped fluorophosphate glasses sensitized with Er3+ and Tm3+ under 800 nm excitation Solid State Communications", 149 (2009) 1216-1220. CrossRef H. Lin, Y.Y. Zhang, E.Y. Pun, "Fluorescence investigation of Ho3+ in Yb3+ sensitized mixed-alkali bismuth gallate glasses", Spectrochimica Acta. Part A, Molecular and biomolecular spectroscopy, 71 (2008) 1547-1550 CrossRef Q. Nie, X. Li, S. Dai, T. Xu, Z. Jin, X. Zhang, "Energy transfer and upconversion luminescence in Tm3+/Yb3+ co-doped lanthanum?zinc?lead?tellurite glasses", Journal of Luminescence, 128 (2008) 135-141. CrossRef X. Shen ,Q. Nie, T. Xu, T. Peng, Y. Gao, "Green and red upconversion emission and energy-transfer between Er3+ and Tm3+ ions in tellurite glasses", Physics Letters A332 (2004) 101?106 CrossRef T. Förster, "Zwischenmolekulare Energiewanderung und Fluoreszenz", Ann. Physik 6(2) (1948) 55-59 CrossRef

Up-conversion luminescence of Tm3+ sensitized by Yb3+ ions in GdVO4

The aim of this work is to study up-conversion (UPC) luminescence in a series of Tm3+/Yb3+-co-doped GdVO4 samples synthesized by the solid-state method. The concentrations of Yb3+ ions were 3, 6 and 9 mol.%, while the concentration of Tm3+ ions was fixed (3 mol.%). X-ray diffraction patterns for all the synthesized samples confirmed successful formation of a pure GdVO4 phase. Quantitative energy-dispersion x-ray analysis confirmed successful doping of Tm3+ and Yb3+ ions into the GdVO4 matrix. Scanning electron microscope images show that the samples are composed of deformed (irregular) spherical particles with an average diameter size in the range of 1.4 − 8.4 μm. Up-converted emission spectra were recorded at room temperature under 980 nm excitation. It was found that all our samples exhibit UPC emission in three different spectral regions: strong emissions are observed at 475 and 800 nm corresponding to the 1G4 → 3H6 and 3H4 → 3H6 transitions, respectively, while emission in the red region at about 650 nm is very weak and is due to the 1G4 → 3F4 transition. It was concluded that conversion of near-infrared radiation into blue emission proved to be very effective in all the synthesized systems. It was found that emission decay curves for all samples exhibit single exponential behavior.

Synthesis, morphology, and upconversion luminescence of Tm3 +/Yb3 + codoped bulk and submicro-rod CaSc2O4 phosphors

CaSc2O4: Tm3+/Yb3+ submicro-rods were synthesized using the mild solvothermal and annealing technique. The temperature of formed pure phase is as low as 600°C. The synthesized submicro-rods are uniform in size and shape. The size of rod is only small with 35nm in width and 200nm in length, which favors the application in biological assays and medical image. Furthermore, samples prepared exhibit the stronger upconversion luminescence than that of obtained by conventional solid state reaction method under 980nm excitation. The near infrared emission around 800nm is enhanced twofold closely. CaSc2O4 phosphor synthesized through the solvothermal and annealing method is a promising submicron upconversion material. The solvothermal and annealing technique is a suitable method for preparing CaSc2O4 sample with rod-like morphology.

Optical transitions of Tm3+ in oxyfluoride glasses and compositional and thermal effect on upconversion luminescence of Tm3+/Yb3+-codoped oxyfluoride glasses

Optical properties of Tm3+-doped SiO2–BaF2–ZnF2 glasses have been investigated on the basis of the Judd–Ofelt theory. Judd–Ofelt intensity parameters, radiative transition probabilities, fluorescence branching ratios and radiative lifetimes have been calculated for different glass compositions. Upconversion emissions were observed in Tm3+/Yb3+-codoped SiO2–BaF2–ZnF2 glasses under 980nm excitation. The effects of composition, concentration of the doping ions, temperature, and excitation pump power on the upconversion emissions were also systematically studied.

Blue Upconversion Luminescence in Tm3+/Yb3+ Codoped CaWO4 Polycrystals

We investigate the upconversion emission of CaWO4:Tm3+/Yb3+ polycrystals prepared by the high-temperature solid-state method. The crystal structure of the polycrystals is characterized by means of x-ray diffraction. Under the excitation of a 980 nm continuous wave diode laser, the samples show intense blue upconversion emissions centered at 473 nm, corresponding to the 1G4→3H6 transition of Tm3+. The dependence of the upconversion emission intensity on the pump power of a laser diode is measured, and the results indicate that the two-photon and three-photon processes contribute simultaneously to the blue upconversion emissions. The possible multi-photon upconversion process and upconversion mechanisms are discussed.

Investigation of near-infrared-to-ultraviolet upconversion luminescence of Tm3+ doped NaYF4 phosphors by Yb3+ codoping

2 mol% Tm3+ doped NaYF4 phosphors with 0–98 mol% Yb3+ codoping were synthesized by sol–gel method. The phase transition from the mixture of hexagonal and cubic phases to single cubic phase of Tm3+–Yb3+:NaYF4 phosphors was investigated with increasing of Yb3+ concentration. Near-infrared, red, blue, violet and ultraviolet upconversion emissions of Tm3+ were observed from the Tm3+–Yb3+:NaYF4 phosphors under 976 nm laser diode excitation, with the strongest near-infrared to ultraviolet emissions at 20 mol% Yb3+ codoping. The violet and blue emissions for the 1D2 → 3F4 and 1G4 → 3H6 transitions of Tm3+ can be tuned by varying Yb3+ codoping concentration, which was elucidated using steady-state equations. The intensity ratio of red emissions for the 3F2 → 3H6 and 3F3→3H6 transitions of Tm3+ was strongly related to the Yb3+ codoping concentration and temperature, implying a potential application of Tm3+–Yb3+:NaYF4 phosphors for optical temperature sensing.

Up-conversion luminescence in Tm3+/Yb3+ Co-doped NaY(MoO4)2 phosphors by optimal design of experiments

为得到最大发光强度的Tm3+/Yb3+共掺钼酸钇钠荧光粉, 采用试验优化设计的方法建立发光强度与Tm3+/Yb3+掺杂浓度的回归方程, 再通过遗传算法优化算出方程的最大解. 利用高温固相法制备出了该解的Tm3+/Yb3+共掺钼酸钇钠荧光粉样品. 在980 nm抽运激发下, 测量了样品的上转换荧光发射谱, 分析了上转换发光机制, 在室温下观察到强烈的蓝光(476 nm)和微弱的红光(649 nm)发射, 其分别对应于Tm3+的1G4→3H6 和1G4 →3F4 跃迁. 在Tm3+/Yb3+ 上转换发光体系中, 1G4 的上转换可见发射是双光子合作上转换能量传递过程. 并探讨了样品的温度效应, 发现该样品蓝光发光强度随温度升高而减弱, 并对其温度猝灭机理进行了解释.

White upconversion luminescence in Tm3+/Ho3+/Yb3+ triply doped K+–Na+ ion-exchanged aluminum germanate glass channel waveguide

Rare-earth ions doped K+–Na+ ion-exchanged aluminum germanate (NMAG) glass channel waveguides have been designed and fabricated. Under 980nm laser pumping, an intense upconversion white light transmission trace was observed in Tm3+/Ho3+/Yb3+ triply doped NMAG glass channel waveguide and a high-brightness light spot was achieved from the output end of the fiber connected to the waveguide channel. The fluorescent colors were diverse and located within or near the white region in CIE chromaticity diagram under various pumping powers. These admirable results indicate that Tm3+/Ho3+/Yb3+ triply doped NMAG channel waveguide is a promising light source for medical and high-precision processing illumination.