Single Particle Insights\ninto the Thermal Sensing\nof Conjugated Polyelectrolyte–Nanoparticle Assemblies

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