Abstracts

Photoluminescent materials have garnered significant interest for their potential in remote temperature sensing, particularly in scenarios where conventional thermometers prove inadequate, such as in biological and medical applications. One popular approach involves employing ratiometric thermometry, which utilizes the luminescence intensity ratio (LIR) between two thermally linked transitions of a lanthanide ion to measure temperature. However, aberrations in the optical collection system can alter the LIR between different setups, hindering the establishment of a standard for cross-laboratory comparison.In this study, we investigate the thermometric properties of upconverting (UC) lanthanide-doped NaYF4 phosphors in the range of micron-sized powders. Additionally, we determine their absolute photoluminescence quantum yields (PLQY) at various temperatures using a novel setup featuring a modified integrating sphere with a temperature-controlled sample holder. This setup enables the correction of optical aberrations, facilitating the derivation of a more robust LIR for the examined processes. The thermometric parameter (LIR) is then obtained at different temperatures via the integrated intensity ratios of (²H_9/2 → ⁴I_13/2)/(⁴S_3/2 → ⁴I_15/2) transitions (526 nm/543 nm) for the Yb³⁺,Er³⁺ co-doped samples. Next, a low-cost setup for the microscopy inspection of samples has been employed for temperature mapping. Finally, the viability and metabolic activity of U-87 MG-GFP cells (cell line isolated from malignant gliomas) is assessed against their contact with the phosphors.