Blue Upconversion Emission In Tm3 Research Articles

Achieving thermochromic upconversion of Tm3+ for high-sensitive nanoprobe and information encryption

Upconversion-based optical thermometry has many merits, such as quick temperature response, higher thermal sensitivity and robust reliability. However, the previous works were mainly focused on the thermally coupled emissions, limiting their thermal sensitivity due to the intrinsic constraint by small energy gaps (e.g., <2000 cm−1) according to Boltzmann distribution theory. Here, we report a design of NaYF4:Yb3+/Tm3+@NaYF4 core-shell nanostructure to achieve thermochromic upconversion and high thermal sensitivity by taking advantage of nonthermally coupled upconversion emissions of Tm3+. We show that the blue upconversion emission of Tm3+ at 475 nm (1G4→3H6) exhibits a regular decrease with elevating temperature, while its deep-red emission at 696 nm (3F2,3→3H6) presents an increase. Such a feature leads to a rapid rise of luminescence intensity ratio (I696 nm/I475 nm) and the optimal relative sensitivity (Sr) reaches 2.79 % K−1 (503 K). More interestingly, the sample gives rise to a gradual emission color change from blue to purplish-red with lifting temperature. Our results offer a new class of upconversion-based nonoprobe with high thermal sensitivity and observable emission color variation, showing a great potential for nanoprobe and information security.

Intense blue upconversion emission in Tm3+/Yb3+ codoped Gd2O3 phosphor

The Gd2O3 nanophosphors codoped with Yb3+/Tm3+ and Yb3+/Tm3+/Li+ ions have been successfully synthesized by conventional solid-state reaction method. Upon 980 nm laser diode excitation, the upconversion emission spectra of the synthesized phosphors have been recorded. The observed spectra show intense blue bands at ∼ 477 nm, ∼ 489 nm and one red band at ∼ 656 nm, which are assigned to 1G4(a) → 3H6, 1G4(b) → 3H6 and 1G4(b) →3F4 transitions of Tm3+ ion respectively. The absorption spectrum of the prepared phosphor has been recorded using UV–Vis-NIR spectrophotometer. The mechanism involved in UC emission process have been analysed with help of energy level diagram and pump power study. Moreover, the CIE colour coordinates of synthesized phosphors lies in blue region which indicates that the prepared phosphors have potential applications in NIR to Visible upconversion and in blue LEDs.

Blue upconversion in Yb3+/Tm3+ co-doped silica fiber based on glass phase-separation technology

Yb3+/Tm3+ co-doped silica fiber was prepared successfully by glass phase-separation technology. The measured refractive index profile indicated that the active fiber core had an excellent uniformity. The highest emission intensity was obtained in a sample with a Yb3+ concentration of 0.3 mol/L and a Tm3+ concentration of 0.1 mol/L. Under the excitation at 976 nm, intense blue upconversion emission of Tm3+ at 474 nm was observed due to energy transfer from Yb3+ to Tm3+. A three-photon process was responsible for the blue emission. Due to re-absorption resulted from the Tm3+:3H6→1G4 transition, the blue emission peak was red-shifted. It is suggested that the fiber preparation technology based on glass phase-separation technology can be a potential candidate for preparing active fibers with large core or complex fiber structure.

Preparation of Gd2O2S: Yb3+, Er3+, Tm3+ sub-micro phosphors by sulfurization of the oxides derived from sol-gel method and the upconversion luminescence properties

Yb3+, Er3+ and Tm3+ co-doped Gd2O2S sub-micro phosphors were synthesized by solid-state sulfurization of the oxide powders derived from sol-gel method. The crystal structure, morphology and upconversion luminescence properties of the phosphors were characterized by x-ray diffraction, scanning electron microscopic and fluorescence spectrum analysis methods. The phosphors exhibited typical hexagonal Gd2O2S phase when sulfurized at 800 °C for 2 h. Under the excitation of 980 nm laser diode, the Gd2O2S: Yb3+, Er3+, Tm3+ phosphors displayed distinct blue, green and red upconversion emissions centered at 481, 546 and 669 nm, respectively. The Gd2O2S phosphors using acetic acid as a chelating agent in the sol-gel process had the optimal upconversion emission property. The upconversion mechanism analysis revealed that the two-photon absorption was mainly responsible for the green and red upconversion emission of Er3+ ions, and the three-photon absorption was responsible for the blue upconversion emission of Tm3+ ions in the Gd2O2S: Yb3+, Er3+, Tm3+ phosphors.

Er3+/Tm3+ codoped tellurite glass for blue upconversion—Structure, thermal stability and spectroscopic properties

The Er3+/Tm3+ codoped WO3 modified tellurite glasses with molar composition of (75−x)TeO2–20ZnO–5Na2O–xWO3–0.2wt%Er2O3–0.8wt%Tm2O3 (x=0,4,8,12mol%) were prepared to realize the blue upconversion emission. The absorption spectra, visible upconversion spectra and 1.53µm band fluorescence spectra of glass samples were measured, together with the quantitative calculations of relevant spectroscopic parameters of Tm3+ and energy transfer micro-parameters between Er3+ and Tm3+ ions, to evaluate the effects of WO3 oxide on the spectroscopic properties of Er3+–Tm3+ ions. It was found that the introduction of WO3 oxide can further improve the blue upconversion emission of Tm3+ through an enhanced phonon-assisted energy transfer process. Meanwhile, with the increase of WO3 amount, the thermal stability of glass hosts, characterized by the difference between the glass crystallization onset temperature and the transition temperature which obtained from the measured differential scanning calorimeter (DSC) curves, increased and no obvious crystallization peak was detected when the WO3 amount increased to 12mol%. Furthermore, the glass structure was briefly analyzed with the obtained Judd–Ofelt intensity parameters, the measured Raman spectra and X-ray diffraction (XRD) curves. The present results demonstrate the feasibility of realizing strong blue upconversion emission by introducing WO3 oxide with high phonon energy into the Er3+/Tm3+ codoped tellurite glass and also indicate its potential application as a glass host applied for the blue upconversion lasers.

Increase of the blue upconversion emission in Tm3 +/Yb3 + co-doped titanate glass–ceramics

Tm3+/Yb3+ co-doped La2O3–TiO2–ZrO2 glass–ceramics with intense blue emission have been fabricated by containerless processing in an aerodynamic levitation furnace, following by heat treatment at different temperatures in the air. The intensity of blue upconversion luminescence increases two times compared with the precursor glass after a heat treatment process at 890°C. Blue and red emissions centered at 476nm and 650nm owing to the Tm3+ transitions 1G4→3H6 and 1G4→3F4 are achieved under the excitation of 980nm at room temperature. The upconversion luminescence is based on a two-photon process by the cooperative sensitization which transfers energy from Yb3+ to Tm3+. Furthermore, Tm3+ and Yb3+ ions are enriched in nanoparticles which disperse in glass matrixes. Dense lattice fields and strong partitions of nanocrystals reduce energy losses caused by mutual interactions among rare earth ions to obtain strong upconversion luminescence. The presented intense blue emission of Tm3+/Yb3+ co-doped La2O3–TiO2–ZrO2 glass–ceramics shows potential promising perspective in the optical materials.

Intense blue up-conversion emission in Tm3 +/Yb3 + co-doped phosphate glass

Tm3+/Yb3+ co-doped phosphate glasses with different concentrations of Tm3+ were prepared by high-temperature melting method. The up-conversion (UC) emission spectra of the samples were measured under 975nm excitation. The blue UC emission at 477nm in the sample doped with 0.5mol% Tm3+ is very strong. By analyzing the power spectra and population processes of the UC emission, we found that photon avalanche phenomenon has existed in the energy transition between Tm3+ and Yb3+ ions, which results in the strong blue UC emission at 477nm. By this way, the luminous efficiency of the materials doped with Tm3+ will be greatly improved. Our research will be helpful in developing UC emission materials.

Tm3+，Yb3+共掺微晶玻璃蓝色上转换荧光的温度特性

Tm³⁺，Yb³⁺共掺微晶玻璃蓝色上转换荧光的温度特性

Optical temperature sensor through infrared excited blue upconversion emission in Tm3 +/Yb3 + codoped Y2O3

An analysis of the intense blue upconversion emission at 476 and 488nm in Tm3+/Yb3+ codoped Y2O3 under excitation power density of 86.7W/cm2 available from a diode laser emitting at 976nm, has been undertaken. Fluorescence intensity ratio (FIR) variation of temperature-sensitive blue upconversion emission at 476 and 488nm in this material was recorded in the temperature range from 303 to 753K. The maximum sensitivity derived from the FIR technique of the blue upconversion emission is approximately 0.0035K−1. The results imply that Tm3+/Yb3+ codoped Y2O3 is a potential candidate for the optical temperature sensor.

Efficient blue upconversion emission in Tm3+ via energy transfer from Yb3+ doped in lithium modified tellurite glass

Intense blue and red upconversion emissions were obtained in Tm3+ doped tellurite glass when codoped with Yb3+ ions on pumping with 798nm radiation. The highest intensity of the blue emission was found for glasses with 0.5mol% Tm3+ and 6.0mol% Yb3+. From a study of the dependence of the upconversion intensity on excitation intensity, it is concluded that emissions are due to Tm3+ ions and involve cooperative energy transfer as well as energy transfer from Yb3+ to Tm3+ ions. Lifetime of the Tm3+ level, which is responsible for the intense blue emission, has been measured for various concentrations of Yb3+.

Fabrication of H+ implanted channel waveguides in Y3Al5O12:Nd,Tm single crystal buried epitaxial layers for infrared to blue upconversion laser systems

Fabrication and intense infrared to blue upconversion emission of proton-implanted Tm3+, Nd3+:Y3Al5O12 (YAG) channel waveguides are reported for the first time to authors’ knowledge. The single or multiple implanted channels are buried by positive induced index change in stacked planar layers grown by liquid-phase epitaxy on pure YAG substrates. The Nd3+ codoping considerably enhances the IR to blue upconversion emission of Tm3+ ions after excitation in resonance with either Nd3+ or Tm3+ absorption transition around 800nm.

Blue up-conversion luminescence and energy transfer process in Nd3+-Yb3+-Tm3+ co-doped ZrF4-based glasses

Up-conversion luminescence properties and energy transfer processes in Nd3+, Yb3+, and Tm3+ co-doped ZrF4-based fluoride glasses have been studied under 800 nm light excitation. Blue up-converted emission around 478 nm which can be assigned to the Tm3+: 1G4→3H6 transition, was strongly observed. Up-conversion luminescence intensity exhibited an YbF3-concentration dependence. Among Nd3+, Yb3+, and Tm3+, both Nd3+ and Tm3+ have ground state absorption bands due to the (2H9/2, F5/24) ←I9/24 and F43←3H6 transitions, respectively, which can be directly pumped by 800 nm light. However, no emissions were observed in Tm3+ singly doped and Tm3+-Yb3+ doubly doped glasses under 800 nm excitation. Therefore, a possible up-conversion mechanism may be proposed as follows: Energy transfer firstly occurs from Nd3+ to Yb3+ when Nd3+ is excited by 800 nm light, then the energy is transferred from Yb3+ to Tm3+ which is on the excited state and, finally, blue up-conversion emission of Tm3+ is observed through the Tm3+: 1G4→3H6 transition. It was also demonstrated that the energy on the Tm3+: 1G4 level was back-transferred to Nd3+ in the Nd3+ high-concentration region, quenching the up-conversion luminescence.

Red to blue up-conversion emission of Tm3+ ions in Yb3+-doped glass ceramic

A detailed study of the spectroscopic properties of PbF2+GeO2+WO3 glass ceramics doped with Tm3+ and codoped with Tm3+ and Yb3+ ions upon 680 nm dye laser light excitation has been made. The absorption, up-conversion emission, excitation, and time-resolved spectra were measured as a function of TmF3 and YbF3 concentrations at room temperature. An enhancement of blue emission centered at 478 nm in the codoped sample was observed. The optium concentrations of TmF3 and YbF3 for this blue emission are about 0.2 and 15 mol %, respectively. It is suggested that the results are due to energy transfer between Yb3+ and Tm3+ ions. Measured oscillator strengths and radiative rates for several transitions are compared with calculated values using the Judd–Ofelt theory with reasonable agreement between theory and experiments for sample doped with Tm3+ ions.