Optical Ratiometric Thermometry Combining Raman Scattering and Europium(III) Luminescence Monitored by Raman Spectroscopy

This study presents a hybrid optical thermometer developed by dispersing the [Eu(nta)₃(phen)] coordination complex into a poly(methyl methacrylate) (PMMA) matrix via drop-casting. This method yields transparent and uniform films that simultaneously combine the polymer’s vibrational Raman bands and the europium luminescence within a single spectrum. To optimize temperature monitoring, a dual-signaling ratiometric parameter (Δ = I_luminescence / I_Raman) was evaluated across a range of 100 to 420 K. The platform demonstrates a clear dual-regime response: below 280 K, a Raman-dominated exponential behavior provides a maximum relative thermal sensitivity (S_m) of 1.1% K⁻¹ at 280 K. Conversely, above 280 K, a luminescence-quenched profile takes over, achieving an outstanding S_m of 5.2% K⁻¹ at 420 K. Furthermore, the probe exhibits remarkable operational reliability, maintaining stable readouts over nine sequential heating-cooling cycles. Overall, this synergistic strategy provides a highly sensitive architecture for next-generation lanthanide-based temperature sensors.