The comparison of Pr³⁺:LaF<inf>3</inf> and Pr³⁺:LiYF<inf>4</inf> luminescent nano- and microthermometer performances

© 2019, Springer Nature B.V. In the present work, we make a comparison of Pr3+:LaF3 and Pr3+:LiYF4 luminescent nano- and microthermometer performances. We studied Pr3+:LaF3 nanoparticles, synthesized via co-precipitation method (further Pr3+:LaF3 (co-precipitation)), Pr3+:LaF3 nanoparticles, synthesized via hydrothermal method (further Pr3+:LaF3 (hydrothermal)), and Pr3+:LaF3 microparticles as well as Pr3+:LiYF4 nanoparticles, synthesized via hydrothermal method (further Pr3+:LiYF4 nanoparticles) and Pr3+:LaF3 microparticles. According to the X-ray diffraction, Pr3+:LaF3 (co-precipitation) and Pr3+:LaF3 (hydrothermal) nanoparticles are hexagonal-structured nanocrystals. Pr3+:LiYF4 nanoparticles are tetragonal-structured nanocrystals. The average diameters of Pr3+:LaF3 (co-precipitation), Pr3+:LaF3 (hydrothermal), and Pr3+:LiYF4 nanoparticles are 13.9, 19.4, and 33.3 nm, respectively. The Pr3+:LaF3 (co-precipitation) and Pr3+:LaF3 (hydrothermal) nanoparticles demonstrate broadband luminescence caused by crystal lattice defects (luminescence background). This luminescence background notably decreases the temperature sensitivity of these samples. The luminescent background removing procedure significantly complicates the signal processing procedure. Pr3+:LaF3 microparticles, Pr3+:LiYF4 nanoparticles, and Pr3+:LaF3 microparticles do not demonstrate this undesirable phenomenon. The absolute temperature sensitivity Sa of Pr3+:LiYF4 nanoparticles, Pr3+:LiYF4 microparticles, and Pr3+:LaF3 microparticles at 300 K are 0.0117 ± 0.0010, 0.0106 ± 0.0010, and 0.0102 ± 0.0012 K−1, respectively. Although the values of Sa are very close for these samples, the nanosized dimensionality of Pr3+:LiYF4 nanoparticles allows achieving high spatial resolution and expanding the fields of application of Pr3+:LiYF4 nanoparticles

Possible ways to control the luminescent properties of LaF<inf>3</inf> nanoparticles doped with rare-earth ions

© 2018 IEEE. Luminescence decay properties of crystalline LaF3 nanoparticles activated by 5% Sm3+ or 12% Ce3+ ions were studied. The observed effects of the variation of synthesis conditions and composite structure on luminescence properties of nanoparticles open the way to manage luminescence and energy transfer properties of the materials

Possible ways to control the luminescent properties of LaF<inf>3</inf> nanoparticles doped with rare-earth ions

© 2018 IEEE. Luminescence decay properties of crystalline LaF3 nanoparticles activated by 5% Sm3+ or 12% Ce3+ ions were studied. The observed effects of the variation of synthesis conditions and composite structure on luminescence properties of nanoparticles open the way to manage luminescence and energy transfer properties of the materials

Luminescence Nanothermometry Based on Pr³⁺: LaF<inf>3</inf> Single Core and Pr³⁺: LaF<inf>3</inf>/LaF<inf>3</inf> Core/Shell Nanoparticles

© 2019 M. S. Pudovkin et al. Core Pr3+: LaF3 (CPr = 1%) plate-like nanoparticles (nanoplates), core/shell Pr3+: LaF3 (CPr = 1%)/LaF3 nanoplates, core Pr3+: LaF3 (CPr = 1%) sphere-like nanoparticles (nanospheres), and core/shell Pr3+: LaF3 (CPr = 1%)/LaF3 nanospheres were synthesized via the coprecipitation method of synthesis. The nanoparticles (NPs) were characterized by means of transmission electron microscopy, X-ray diffraction, and optical spectroscopy. The formation of the shell was proved by detecting the increase in physical sizes, sizes of coherent scattering regions, and luminescence lifetimes of core/shell NPs comparing with single core NPs. The average physical sizes of core nanoplates, core/shell nanoplates, core nanospheres, and core/shell nanospheres were 62.2 ± 0.9, 74.7 ± 1.2, 13.8 ± 0.9 and 22.0 ± 1.2 nm, respectively. The formation of the NP shell led to increasing of effective luminescence lifetime τeff of the 3P0 state of Pr3+ ions for the core nanoplates, core/shell nanoplates, core nanospheres, and core/shell nanospheres the values of τeff were 2.3, 3.6, 3.2, and 4.7 μsec, respectively (at 300 K). The values of absolute sensitivity Sa for fluorescence intensity ratio (FIR) thermometry was 0.01 K-1 at 300 K for all the samples. The FIR sensitivity can be attributed to the fact that 3P1 and 3P0 states share their electronic populations according to the Boltzmann process. The values of Sa for lifetime thermometry for core nanoplates, core/shell nanoplates, core nanospheres, and core/shell nanospheres were (36.4 ± 3.1) · 10-4, (70.7 ± 5.9) · 10-4, (40.7 ± 2.6) · 10-4, and (68.8 ± 2.4) · 10-4 K-1, respectively

Characterization of Pr-doped LaF<inf>3</inf> nanoparticles synthesized by different variations of coprecipitation method

© 2019 M. S. Pudovkin et al. A set of Pr3+:LaF3 nanoparticles (NPs) were synthesized via coprecipitation method at three stoichiometric proportions of La(NO3)3, Pr(NO3)3, and NaF (1: 0.8, 1: 1, and 1: 6, respectively). Two ways of mixing of the La(NO3)3, Pr(NO3)3, and NaF solutions (dropwise and swift addition) were used. One sample was subjected to microwave (MW) treatment for 30, 90, and 180 min. All the samples were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). For all the samples, optical spectroscopy experiments were carried out. The XRD data were analyzed via the Debye-Scherrer and Williamson-Hall methods. It was revealed that the way of mixing of the La(NO3)3, Pr(NO3)3, and NaF solutions strongly affects the shape of the NPs. The slow dropwise addition of the NaF solution leads to the plate-like NP (PLNP) formation; otherwise, the swift addition of the NaF solution leads to the formation of more sphere-like NPs (SLNPs). The size and regularity in shape of the NP increase with the increasing stoichiometric proportion of La(NO3)3, Pr(NO3)3, and NaF from 1: 0.8 to 1: 6. The size and regularity in shape of the SLNPs increase with the increasing time of MW treatment. The Debye-Scherrer and Williamson-Hall methods confirmed the anisotropic shape of the PLNPs. The Williamson-Hall method showed that the values of strain are almost similar for all the samples (around 14∗10-4). Optical spectroscopy experiments revealed that although all the samples have an equal chemical composition, the luminescence lifetimes for different samples differ between each other. The luminescence lifetime of the PLNPs is less than that of the SLNPs having an equal stoichiometric proportion of La(NO3)3, Pr(NO3)3, and NaF. The luminescence lifetime of the 1: 1 SLNPs increases with the increasing time of MW treatment

Luminescence Nanothermometry Based on Pr³⁺: LaF<inf>3</inf> Single Core and Pr³⁺: LaF<inf>3</inf>/LaF<inf>3</inf> Core/Shell Nanoparticles

© 2019 M. S. Pudovkin et al. Core Pr3+: LaF3 (CPr = 1%) plate-like nanoparticles (nanoplates), core/shell Pr3+: LaF3 (CPr = 1%)/LaF3 nanoplates, core Pr3+: LaF3 (CPr = 1%) sphere-like nanoparticles (nanospheres), and core/shell Pr3+: LaF3 (CPr = 1%)/LaF3 nanospheres were synthesized via the coprecipitation method of synthesis. The nanoparticles (NPs) were characterized by means of transmission electron microscopy, X-ray diffraction, and optical spectroscopy. The formation of the shell was proved by detecting the increase in physical sizes, sizes of coherent scattering regions, and luminescence lifetimes of core/shell NPs comparing with single core NPs. The average physical sizes of core nanoplates, core/shell nanoplates, core nanospheres, and core/shell nanospheres were 62.2 ± 0.9, 74.7 ± 1.2, 13.8 ± 0.9 and 22.0 ± 1.2 nm, respectively. The formation of the NP shell led to increasing of effective luminescence lifetime τeff of the 3P0 state of Pr3+ ions for the core nanoplates, core/shell nanoplates, core nanospheres, and core/shell nanospheres the values of τeff were 2.3, 3.6, 3.2, and 4.7 μsec, respectively (at 300 K). The values of absolute sensitivity Sa for fluorescence intensity ratio (FIR) thermometry was 0.01 K-1 at 300 K for all the samples. The FIR sensitivity can be attributed to the fact that 3P1 and 3P0 states share their electronic populations according to the Boltzmann process. The values of Sa for lifetime thermometry for core nanoplates, core/shell nanoplates, core nanospheres, and core/shell nanospheres were (36.4 ± 3.1) · 10-4, (70.7 ± 5.9) · 10-4, (40.7 ± 2.6) · 10-4, and (68.8 ± 2.4) · 10-4 K-1, respectively