Polymeric nano-thermometer exploiting reverse intersystem crossing: a potential solution to common interferences.

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Nanothermometry is crucial for applications like intracellular sensing and microfluidics.
• Current fluorescence-based methods often rely on temperature-induced quenching, which can be sensitive to background noise.
• Fluorescence enhancement with temperature presents a more robust sensing mechanism.

Purpose of the Study:

• To demonstrate a proof-of-concept nanothermometry platform based on fluorescence enhancement.
• To investigate the photophysical mechanisms behind temperature-dependent fluorescence in dye-doped nanoparticles.
• To establish a general design principle for fluorescence-enhancement-based nanothermometry.

Main Methods:

• Utilized eosin and pheophorbide A co-doped polystyrene nanoparticles as a model system.
• Conducted experimental and theoretical investigations of eosin's photophysical behavior.
• Analyzed temperature-dependent emission spectra and fluorescence intensity.

Main Results:

• Observed fluorescence enhancement with increasing temperature, attributed to thermally activated reverse intersystem crossing (RISC).
• Demonstrated a functional nanothermometry probe operating in the biologically relevant range (10-80 °C) with a sensitivity of 1.9 ± 0.2% °C⁻¹.
• Confirmed functionality at the single-particle level.

Conclusions:

• Established a viable nanothermometry platform utilizing fluorescence enhancement via RISC.
• Highlighted the importance of anionic eosin species for fluorescence enhancement at elevated temperatures.
• Proposed a general design principle for developing highly sensitive and robust nanoscale temperature sensors using thermally activated delayed fluorescence (TADF) dyes.