Luminescence Nanothermometry Based on Pr³⁺ : LaF₃ Single Core and Pr³⁺ : LaF₃/LaF₃ Core/Shell Nanoparticles

Abstract

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.

Upconversion Thermometry Using Yb3+/Er3+ Co-Doped KY3F10 Nanoparticles

“…In general, information about the thermometric performance (thermal sensitivity, S r ) of the upconverting nanosensors is inferred from the fluorescence intensity ratio (Δ) of thermally coupled energy levels of the Ln 3+ ions. Several studies have reported that the thermometric parameter Δ, appears to be reliant on the type of host, − type of dopant ion and their concentrations, , size of the nanoparticles, , surface functionalization, core–shell structure, , incorporation of transition metals, − laser excitation density, and modification of the energy transfer processes − (Table ). As such, detailed studies involving optimization of the chemical and spectroscopic properties of UCNP-based sensors have been performed to increase the operating temperature sensitivity and temperature resolution to fulfill the specific needs of given applications.…”