Rapid Room Temperature Synthesis and Temperature Sensitive Photoluminescence of Yb3+/Tm3+ Co-Doped K0.3Bi0.7F2.4 Nanoparticles for Optical Thermometry

The study reveals that these nanoparticles exhibit highly tunable photoluminescence (PL), with distinct blue, red, and near-infrared emissions that are highly sensitive to temperature changes. For the first time, the temperature-dependent characteristics of PL emissions for optical thermometry behavior among 300–500 K for particular nanoparticles are also investigated. The temperature-dependent fluorescence intensity ratio (FIR) technique, leveraging phonon-mediated apparent temperature-dependent coupling among Tm 3+ states, is employed to calculate the absolute sensitivity (S a ) and relative sensitivity (S r ) of particular nanoparticles. The results indicate high S a values of up to 0.0108 K −1 for sample A and 0.0017 K −1 for sample B across the given temperature range. Sample A exhibits a higher S r of 0.0122%K −1 at low temperatures, while decreasing to 0.0046%K −1 at higher temperatures, while sample B maintains a relatively consistent value over the same temperature range. These results highlight the potential of the synthesized nanoparticles as an effective optical thermometric probe. The Yb 3+ concentration directly modulates energy transfer efficiency and temperature sensitivity by influencing both the rate of energy transfer to Tm 3+ and the extent of nonradiative losses. Optimizing Yb 3+ content is thus crucial for achieving high sensitivity and stability in PL-based optical thermometry, positioning Yb 3+ /Tm 3+ co-doped K 0.3 Bi 0.7 F 2.4 nanoparticles as promising candidates for advanced noncontact temperature sensing applications.