Investigation on Two Forms of Temperature-Sensing Parameters for Fluorescence Intensity Ratio Thermometry Based on Thermal Coupled Theory

Absolute temperature sensitivity (<i>S</i>_a) reflects the precision of sensors that belong to the same mechanism, whereas relative temperature sensitivity (<i>S</i>_r) is used to compare sensors from different mechanisms. For the fluorescence intensity ratio (FIR) thermometry based on two thermally coupled energy levels of one rare earth (RE) ion, we define a new ratio as the temperature-sensing parameter that can vary greatly with temperature in some circumstances, which can obtain higher <i>S</i>_a without changing <i>S</i>_r. Further discussion is made on the conditions under which these two forms of temperature-sensing parameters can be used to achieve higher <i>S</i>_a for biomedical temperature sensing. Based on the new ratio as the temperature-sensing parameter, the <i>S</i>_a and <i>S</i>_r of the BaTiO₃: 0.01%Pr³⁺, 8%Yb³⁺ nanoparticles at 313 K reach as high as 0.1380 K^–1 and 1.23% K^–1, respectively. Similarly, the <i>S</i>_a and <i>S</i>_r of the BaTiO₃: 1%Er³⁺, 3%Yb³⁺ nanoparticles at 313 K are as high as 0.0413 K^–1 and 1.05% K^–1, respectively. By flexibly choosing the two ratios as the temperature-sensing parameter, higher <i>S</i>_a can be obtained at the target temperature, which means higher precision for the FIR thermometers

Solvothermal Synthesis and Luminescence Properties of BaCeF₅, and BaCeF₅: Tb³⁺, Sm³⁺ Nanocrystals: An Approach for White Light Emission

Novel monodisperse BaCeF₅ and BaCeF₅: Tb³⁺, Sm³⁺ nanocrystals have been successfully synthesized by a simple one-step solvothermal synthesis. Uniformly distributed nanocrystals with an octahedral morphology and particle size of 75–80 nm were observed. X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), photoluminescence (PL), and decay studies were employed to characterize the samples. Under ultraviolet irradiation, the BaCeF₅: Tb³⁺, Sm³⁺ samples exhibit the typical green emission band of the Tb³⁺ ions, as well as an orange-red and red emission bands of the Sm³⁺ ions in the presence of Ce³⁺ ions. The highly intense orange-red and red emission bands of the Sm³⁺ ions were attributed to the effective energy transfer from the Tb³⁺ to Sm³⁺ ions, which has been justified through the luminescence spectra and the fluorescence decay dynamics. The luminescence colors of BaCeF₅: Tb³⁺, Sm³⁺ nanophosphors can be easily tuned by changing the concentration of Sm³⁺ ions. These results suggest that BaCeF₅: Tb³⁺, Sm³⁺ nanocrystals can be explored for three-dimensional displays, back lighting, white light sources, and so on