Temperature sensitivity of Nd³⁺, Yb³⁺:YF<inf>3</inf> ratiometric luminescent thermometers at different Yb³⁺ concentration

Nd3+ (0.5 mol.%), Yb3+ (1.0, 2.0, 3.0, 4.0, and 8.0 mol.%):YF3 phosphors were synthesized using a co-precipitation method with subsequent hydrothermal treatment and annealing in vacuum. The Nd3+, Yb3+:YF3 phosphors are orthorhombic phase nano-crystals. Luminescence intensity ratio (LIR) of Nd3+ (4F3/2 – 4I9/2, ~866 nm) and Yb3+ (2F5/2 – 2F7/2, ~980 nm) emissions was chosen as temperature-dependent parameter. The energy exchange between 4F3/2 (Nd3+) and 2F5/2 (Yb3+) is phonon-assisted which explains the temperature dependence of LIR. There are Nd3+ to Yb3+ energy transfer (ET), Yb3+ to Nd3+ back energy transfer (BET) and energy diffusion (ED) between Yb3+ ions. The probability of BET decreases with the increase of Yb3+ concentration which leads to LIR dependence on Yb3+ concentration. The maximum absolute temperature sensitivity (Sa) was achieved for Nd3+ (0.5%), Yb3+ (1.0%):YF3 (Sa = 0.0018 K−1 at 148 K). The studied samples demonstrate high stability after 8 cooling-heating cycles. The Nd3+ (0.5%), Yb3+ (1.0%):YF3 phosphors are very promising for temperature sensing

Transmission electron microscopy and flow cytometry study of cellular uptake of unmodified Pr³⁺:LaF<inf>3</inf> nanoparticles in dynamic

The article represents the transmission electron microscopy (TEM) and flow cytometry study of A-549 (human lung carcinoma) cellular uptake of unmodified Pr3+:LaF3 nanoplates and nanospheres after 2, 10, and 24 h of nanoparticles exposure. The studied Pr3+:LaF3 (CPr = 1 mol.%) nanoplates (length = 64.0 ± 1.0 nm) and nanospheres (diameter = 13.0 0.4 nm) are hexagonal structured nanocrystals without amorphous phase. Both morphotypes of nanoparticles (nanoplates and nanospheres) are easily internalized by A-549 cells via macropinocytosis after 2, 10, and 24 h of nanoparticle exposure. The nanoparticles were not observed in cell nuclei and other organelles. During macropinocytosis, relatively large vesicles (0.2–5 μm) are formed. The flow cytometry experiments revealed that the internalized nanoparticles increase the cells’ optical inhomogeneous that leads to an increase of side scattered light intensity by ~ 10% without any dynamic during 24 h (for both morphotypes of nanoparticles). Probably, it can be explained by the fact that macropinocytosis is a dynamic process and some macropinosomes appear and move in the cytoplasm, in turn, other macropinosomes travel back to the cell surface of the membrane and release the content to the extracellular space, consequently, the equilibrium is achieved

Luminescent thermometry based on Ba<inf>4</inf>Y<inf>3</inf>F<inf>17</inf>:Pr³⁺ and Ba<inf>4</inf>Y<inf>3</inf>F<inf>17</inf>:Pr³⁺,Yb³⁺ nanoparticles

© 2020 Elsevier Ltd and Techna Group S.r.l. New effective luminescence thermometers based on novel host Ba4Y3F17 doped with Pr3+ and Pr3+/Yb3+ in 80–320 K temperature range were studied. The absolute temperature sensitivity (Sa) of both Ba4Y3F17: Pr3+(0.1 mol %) and Ba4Y3F17: Pr3+(0.1 mol.%): Yb3+(10.0 mol.%)nanothermometers based on luminescence intensity ratio (LIR) between two Pr3+ emission bands (3P1-3H5 and 3P0-3H5) demonstrate a notable value (0.011 K−1 at 300 K) in the 200–320 K range. The Ba4Y3F17: Pr3+(0.1 mol.%): Yb3+(10.0 mol.%)nanothermometers based on LIR between 3P0→3H4 of Pr3+ and 2F5/2→ 2F7/2 of Yb3+ emission bands demonstrate high Sa into the 80–200 K range with maximal Sa = 0,0778 K−1 at 100 K. The stability of the phosphors was revealed by thermo-cycling experiments

Spectral-Kinetic Properties and Energy Transfer in Nanoparticles of Y<inf>0.5–x</inf>Ce<inf>0.5</inf>Tb<inf> x</inf>F<inf>3</inf> Solid Solution

© 2020, Springer Science+Business Media, LLC, part of Springer Nature. Crystalline nanoparticles of Y0.5–xCe0.5TbxF3, doped with various concentrations (x = 0, 0.005, 0.01, 0.05, 0.1, 0.15, and 0.2) of Tb3+ ions were synthesized by co-precipitation. The crystal structure and chemical composition of nanoparticles were studied using transmission electron microscopy, scanning electron microscopy, and X-ray diffractometry. The obtained nanoparticles of solid solutions had an elliptical shape with a size of 10–15 nm along the long axis and good crystallinity with the structure of a CeF3 crystal. The spectral-kinetic properties of the obtained nanoparticles, and the effect of the concentration of Tb3+ activator ions on the energy transfer from Ce3+ to Tb3+ ions were investigated. Energy transfer from Ce3+ to Tb3+ ions in nanocrystals of the Y0.5–xCe0.5TbxF3 solid solutions occurs mainly through the dipole–dipole interaction. The results of evaluating the efficiency of energy transfer from Ce3+ to Tb3+ ions show its increase with increasing concentration of Tb3+ ions