Sanja Ćulubrk

Self-referenced luminescence thermometry with Sm3+ doped TiO2 nanoparticles

The performance of Sm(3+) doped TiO2 nanoparticles for luminescence temperature sensing was tested over a temperature range from room to 110 °C. The Sm(3+) ions were incorporated into TiO2 nanocrystals using hydrolytic sol-gel route. Microstructural characterization of the obtained material was performed using transmission electron microscopy and x-ray diffraction measurements. Luminescence emission spectra of Sm(3+) doped TiO2 nanoparticles consists of two distinct spectral regions: the high energy region associated with the trap emission of the TiO2 host, and the low energy region with well-resolved emission peaks of the Sm(3+) ions. The ratio between Sm(3+) emission and TiO2 trap emission shows strong temperature dependence, and is tested for temperature sensing. The relative sensor sensitivity was found to be higher than 1% °C(-1) over given temperature range with the maximum value of 10.54% °C(-1) at 57.5 °C. Lifetime data derived from the Sm(3+) emission decay revealed that time-resolved measurements provide comparable quality of temperature sensing as corresponding ratiometric measurements, with a maximum relative sensitivity of 10.14% °C(-1) at 66.5 °C.

Analysis of luminescence of Eu3+ doped Lu2Ti2O7 powders with Judd-Ofelt theory

Abstract Eu3+ doped Lu2Ti2O7 particles of 6 to 10 nm in diameter are prepared by Pechini-type polymerized complex route based on polyesterification between citric acid (CA) and ethylene glycol. X-ray diffraction measurements confirmed that Eu3+ doped Lu2Ti2O7 powders crystallized in the face-centered cubic lattice (Fd3m). Emission spectra displayed characteristic 5D0 →7 FJ (J = 0, 1, 2, 3 and 4) spin forbidden f-f electronic transitions of the Eu3+ ions with the most pronounced emission coming from 5D0 →7 F2 and with the emission decays varying between 0.75 and 0.60 ms for samples doped with different concentration of Eu3+. The Judd-Ofelt theory was applied to the experimental data for the quantitative determination of optical parameters such as Ω2, Ω4 Judd-Ofelt parameters, radiative and nonradiative transition rates and emission quantum efficiency. It was observed that, for all the samples, Ω2 >> Ω4. The luminescence quantum yields were calculated by means of the Judd-Ofelt theory and the highest value 60.83 % is obtained for particles doped with concentration of 3 % Eu3+.

Sol-Gel Derived Eu3+-Doped Gd2Ti2O7Pyrochlore Nanopowders

Herein we presented hydrolytic sol-gel synthesis and photoluminescent properties of Eu3+-doped Gd2Ti2O7 pyrochlore nanopowders. According to Gd2Ti2O7 precursor gel thermal analysis a temperature of 840°C is identified for the formation of the crystalline pyrochlore phase. Obtained samples were systematically characterized by powder X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence spectroscopy. The powders consist of well-crystalline cubic nanocrystallites of approximately 20 nm in size as evidenced from X-ray diffraction. The scanning and transmission electron microscopy shows that investigated Eu3+-doped Gd2Ti2O7 nanopowders consist of compact, dense aggregates composed entirely of nanoparticles with variable both shape and dimension. The influence of Eu3+ ions concentration on the optical properties, namely, photoluminescence emission and decay time, is measured and discussed. Emission intensity as a function of Eu3+ ions concentration shows that Gd2Ti2O7 host can accept Eu3+ ions in concentrations up to 10 at.%. On the other hand, lifetime values are similar up to 3 at.% (∼2.7 ms) and experience decrease at higher concentrations (2.4 ms for 10 at.% Eu3+). Moreover, photoluminescent spectra and lifetime values clearly revealed presence of structural defects in sol-gel derived materials proposing photoluminescent spectroscopy as a sensitive tool for monitoring structural changes in both steady state and lifetime domains.Herein we presented hydrolytic sol-gel synthesis and photoluminescent properties of Eu3+-doped Gd2Ti2O7 pyrochlore nanopowders. According to Gd2Ti2O7 precursor gel thermal analysis a temperature of 840°C is identified for the formation of the crystalline pyrochlore phase. Obtained samples were systematically characterized by powder X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence spectroscopy. The powders consist of well-crystalline cubic nanocrystallites of approximately 20 nm in size as evidenced from X-ray diffraction. The scanning and transmission electron microscopy shows that investigated Eu3+-doped Gd2Ti2O7 nanopowders consist of compact, dense aggregates composed entirely of nanoparticles with variable both shape and dimension. The influence of Eu3+ ions concentration on the optical properties, namely, photoluminescence emission and decay time, is measured and discussed. Emission intensity as a function of Eu3+ ions concentration shows that Gd2Ti2O7 host can accept Eu3+ ions in concentrations up to 10 at.%. On the other hand, lifetime values are similar up to 3 at.% (~2.7 ms) and experience decrease at higher concentrations (2.4 ms for 10 at.% Eu3+). Moreover, photoluminescent spectra and lifetime values clearly revealed presence of structural defects in sol-gel derived materials proposing photoluminescent spectroscopy as a sensitive tool for monitoring structural changes in both steady state and lifetime domains.

Sol-Gel derived Eu 3+ -doped Gd 2 Ti 2 O 7 pyrochlore nanopowders

Herein we presented hydrolytic sol-gel synthesis and photoluminescent properties of Eu3+-doped Gd2Ti2O7 pyrochlore nanopowders. According to Gd2Ti2O7 precursor gel thermal analysis a temperature of 840°C is identified for the formation of the crystalline pyrochlore phase. Obtained samples were systematically characterized by powder X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence spectroscopy. The powders consist of well-crystalline cubic nanocrystallites of approximately 20 nm in size as evidenced from X-ray diffraction. The scanning and transmission electron microscopy shows that investigated Eu3+-doped Gd2Ti2O7 nanopowders consist of compact, dense aggregates composed entirely of nanoparticles with variable both shape and dimension. The influence of Eu3+ ions concentration on the optical properties, namely, photoluminescence emission and decay time, is measured and discussed. Emission intensity as a function of Eu3+ ions concentration shows that Gd2Ti2O7 host can accept Eu3+ ions in concentrations up to 10 at.%. On the other hand, lifetime values are similar up to 3 at.% (∼2.7 ms) and experience decrease at higher concentrations (2.4 ms for 10 at.% Eu3+). Moreover, photoluminescent spectra and lifetime values clearly revealed presence of structural defects in sol-gel derived materials proposing photoluminescent spectroscopy as a sensitive tool for monitoring structural changes in both steady state and lifetime domains.Herein we presented hydrolytic sol-gel synthesis and photoluminescent properties of Eu3+-doped Gd2Ti2O7 pyrochlore nanopowders. According to Gd2Ti2O7 precursor gel thermal analysis a temperature of 840°C is identified for the formation of the crystalline pyrochlore phase. Obtained samples were systematically characterized by powder X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence spectroscopy. The powders consist of well-crystalline cubic nanocrystallites of approximately 20 nm in size as evidenced from X-ray diffraction. The scanning and transmission electron microscopy shows that investigated Eu3+-doped Gd2Ti2O7 nanopowders consist of compact, dense aggregates composed entirely of nanoparticles with variable both shape and dimension. The influence of Eu3+ ions concentration on the optical properties, namely, photoluminescence emission and decay time, is measured and discussed. Emission intensity as a function of Eu3+ ions concentration shows that Gd2Ti2O7 host can accept Eu3+ ions in concentrations up to 10 at.%. On the other hand, lifetime values are similar up to 3 at.% (~2.7 ms) and experience decrease at higher concentrations (2.4 ms for 10 at.% Eu3+). Moreover, photoluminescent spectra and lifetime values clearly revealed presence of structural defects in sol-gel derived materials proposing photoluminescent spectroscopy as a sensitive tool for monitoring structural changes in both steady state and lifetime domains.

Sol-Gel Derived Eu3

Herein we presented hydrolytic sol-gel synthesis and photoluminescent properties of Eu3+-doped Gd2Ti2O7 pyrochlore nanopowders. According to Gd2Ti2O7 precursor gel thermal analysis a temperature of 840°C is identified for the formation of the crystalline pyrochlore phase. Obtained samples were systematically characterized by powder X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence spectroscopy. The powders consist of well-crystalline cubic nanocrystallites of approximately 20 nm in size as evidenced from X-ray diffraction. The scanning and transmission electron microscopy shows that investigated Eu3+-doped Gd2Ti2O7 nanopowders consist of compact, dense aggregates composed entirely of nanoparticles with variable both shape and dimension. The influence of Eu3+ ions concentration on the optical properties, namely, photoluminescence emission and decay time, is measured and discussed. Emission intensity as a function of Eu3+ ions concentration shows that Gd2Ti2O7 host can accept Eu3+ ions in concentrations up to 10 at.%. On the other hand, lifetime values are similar up to 3 at.% (∼2.7 ms) and experience decrease at higher concentrations (2.4 ms for 10 at.% Eu3+). Moreover, photoluminescent spectra and lifetime values clearly revealed presence of structural defects in sol-gel derived materials proposing photoluminescent spectroscopy as a sensitive tool for monitoring structural changes in both steady state and lifetime domains.Herein we presented hydrolytic sol-gel synthesis and photoluminescent properties of Eu3+-doped Gd2Ti2O7 pyrochlore nanopowders. According to Gd2Ti2O7 precursor gel thermal analysis a temperature of 840°C is identified for the formation of the crystalline pyrochlore phase. Obtained samples were systematically characterized by powder X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence spectroscopy. The powders consist of well-crystalline cubic nanocrystallites of approximately 20 nm in size as evidenced from X-ray diffraction. The scanning and transmission electron microscopy shows that investigated Eu3+-doped Gd2Ti2O7 nanopowders consist of compact, dense aggregates composed entirely of nanoparticles with variable both shape and dimension. The influence of Eu3+ ions concentration on the optical properties, namely, photoluminescence emission and decay time, is measured and discussed. Emission intensity as a function of Eu3+ ions concentration shows that Gd2Ti2O7 host can accept Eu3+ ions in concentrations up to 10 at.%. On the other hand, lifetime values are similar up to 3 at.% (~2.7 ms) and experience decrease at higher concentrations (2.4 ms for 10 at.% Eu3+). Moreover, photoluminescent spectra and lifetime values clearly revealed presence of structural defects in sol-gel derived materials proposing photoluminescent spectroscopy as a sensitive tool for monitoring structural changes in both steady state and lifetime domains.

Structural and optical properties of europium doped Y2O3 nanoparticles prepared by self-propagation room temperature reaction method

Abstract Europium-doped yttrium oxide nanoparticles with different doping concentrations were prepared by self-propagation room temperature reaction method. This simple synthesis method provides particles in the range of 12nm to 50 nm, depending on the temperature of calcination. In all cases, the nanopowders showed intense red emission upon excitation with ultraviolet radiation. Structural and optical characterization showed that the nanoparticles obtained after calcination at 1100°C have smaller unit cell volume and microstrain and longer emission lifetimes compared to the nanoparticles obtained after calcination at 600°C and 800°C. The maximal emission intensity was found for the sample doped with 5at% of Eu3+.