Optical ratiometric thermometry combining Raman and luminescence bands in PMMA/Eu^III complex films.

Area of Science:

• Materials Science
• Analytical Chemistry
• Spectroscopy

Background:

• Optical temperature sensing is crucial for monitoring diverse processes.
• Raman thermometry provides structural insights, while luminescence thermometry offers high thermal sensitivity.
• Lanthanide(III) coordination compounds are key for optical temperature probes, especially ratiometric approaches, but achieving high sensitivity remains challenging.

Purpose of the Study:

• To develop a hybrid optical thermometer by integrating Raman and luminescence bands.
• To create a ratiometric thermometric parameter (Δ = I_luminescence/I_Raman) for enhanced temperature sensing.
• To investigate the temperature-dependent behavior and sensitivity of the hybrid system.

Main Methods:

• Incorporation of a [Eu(nta)₃(phen)] complex into a poly(methyl methacrylate) (PMMA) matrix to form transparent films.
• Simultaneous detection of PMMA vibrations (Raman bands) and Eu^III emissions (luminescence bands) within the same Raman spectrum.
• Ratiometric analysis of luminescence and Raman bands to determine temperature over a range of 100–420 K.

Main Results:

• A hybrid optical thermometer was successfully fabricated using Eu^III-PMMA films.
• Two distinct temperature-dependent regimes were observed for the ratiometric parameter: Raman-dominated below 280 K (S_m = 1.1% K^-1) and luminescence-driven above 280 K (S_m = 5.2% K^-1).
• The thermometric parameter demonstrated robust repeatability over nine heating-cooling cycles.

Conclusions:

• The hybrid optical thermometer, utilizing a ratiometric approach combining luminescence and Raman bands, offers a versatile and flexible platform for temperature sensing.
• This method significantly enhances thermal sensitivity compared to traditional ratiometric approaches relying solely on luminescence.
• The developed Eu^III coordination compound-based probes show great promise for highly sensitive optical temperature monitoring applications.