Abstract
<jats:p>Temperature measurements at the nanoscale are essential for understanding physiological and pathological processes. Here, we report fluorescent polymeric nanothermometers (FPTSs) based on thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) endfunctionalized with environment-sensitive DCM-like fluorophores, which self-assemble into well-defined nanoparticles in aqueous media. Two closely related probes, DCMC and DCMQ, exhibiting similar solvatochromic behavior but opposite aggregation tendencies (aggregation-caused quenching, ACQ, vs aggregation-induced emission, AIE), are used to screen the respective contributions of aggregation, polarity, and microviscosity in the temperature-dependent fluorescence response. Upon heating, the LCST-driven collapse of PNIPAM triggers nanoscale reorganization of the polymeric assemblies, leading to a local environment of reduced polarity and increased microviscosity. This results in a fluorescence enhancement accompanied by a spectral blue shift, enabling both intensityand ratiometric-based temperature sensing. The systems display high sensitivity, including in the physiological temperature range. In particular, the DCMC-based nanothermometer combines a large Stokes shift with near-infrared emission, highlighting its potential for bioimaging applications.</jats:p>