Single Particle Insights into the Thermal Sensing of Conjugated Polyelectrolyte–Nanoparticle Assemblies

Developing sensitive temperature sensors for nano- and microscale applications has become critical in many fields. In this work, we report on the use of anionic poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene] conjugated polyelectrolyte (CPE) as a thermal sensor upon its interaction with poly(1-vinylpyrrolidone-co-styrene) (PVP-co-PS) nanoparticles. The concentration of CPE was optimized to adopt a collapsed state at room temperature when assembled onto the PVP-co-PS nanoparticles with the ability to extend its backbone upon heating. This configuration allowed for the observation of fluorescence enhancement at higher temperatures. The relative sensitivity of the sensor was calculated to be equal to 1.57% at 40 °C with a linear range between 20 and 90 °C. The photophysical properties of the thermal nanoparticles’ sensor were studied at the single-particle level. Intensity-time traces and emission spectra collected from single nanoparticles validated the structural–spectroscopic correlation with the observed thermal response, which we believe can be generalized to many similar conjugated polyelectrolyte systems.