Visual temperature sensor and luminescent thermometer based on the complex Tb/Eu–TPTZ incorporated in transparent PMMA film

A new transparent hybrid film obtained from lanthanide complex Tb/Eu–TPTZ incorporated in PMMA was designed for its potential use as luminescent thermometer and visual temperature sensor. The structure of the lanthanide complexes was numerically confirmed in a gas phase through the density functional theory (DFT). The hybrid film excited with 310 nm at RT showed a greenish-yellow color and was associated with the mix of the typical emission bands of the Tb³⁺ and Eu³⁺ ions incorporated in the film. The temperature-dependent photoluminescence properties of the (Tb/Eu-TPTZ)PMMA film were analyzed in the range of 25–120 °C. The integrated areas of the transition bands ⁵D₄ → ⁷F₅ (Tb³⁺), and ⁵D₀ → ⁷F₂ (Eu³⁺) were used in the ratiometric technique based on the fluorescence intensity ratio (FIR). In the temperature range 25−100 °C, the thermometric parameter showed good linear (R² = 0.997) behavior and a value for the relative sensitivity S_r of 2.98 % °C⁻¹. A color change was observed for the hybrid film, going from greenish-yellow to red when the temperature changed from 25–100 °C. The results suggest that (Tb/Eu–TPTZ)PMMA film has promising characteristics to be considered as a luminescent thermometer and visual temperature sensor in the range of 25–100 °C.