Phase-transition/fluorescence dual-mode sensor based on hyperbranched thermosensitive polymers/AIE for wide-area detection of temperature

Accurate temperature monitoring holds significant scientific importance in fields such as industrial manufacturing and biomedical applications. However, conventional fluorescent thermometers, commonly relying on single-response mechanisms, suffer from inherent drawbacks including thermally induced fluorescence quenching that makes the observed phenomena difficult to discern, poor resistance to environmental interference, and inadequate detection accuracy. To address the aforementioned limitations, this study developed a novel temperature sensing approach based on dual-signal responses from phase transition and fluorescence. The sensor (HPEI-IBAm/DIBA), through the synergistic action of isobutyryl-capped hyperbranched polyethyleneimine (HPEI-IBAm) and the aggregation-induced emission (AIE)-active fluorogen 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoic acid (DIBA), enables dual-signal output of both fluorescence intensity and transmittance. Based on the temperature sensitivity of HPEI-IBAm, the microstructure of the probe undergoes reversible stretching/contraction and synchronized changes in transmittance with temperature changes. By adjusting the concentration of HPEI-IBAm and the system pH value, the cloud point (CP) and temperature measurement range of HPEI-IBAm/DIBA can be effectively modulated, with an overall linear range of 21.2–74.0 °C ( R 2  > 0.9900). This dual-signal synchronization mechanism effectively mitigates false-positive interference while enhancing detection accuracy. The sensor combines excellent thermal sensitivity and temperature resolution, delivering reliable responses over a broad temperature range while exhibiting remarkable reversibility and repeatability even after 20 thermal cycles, with relative standard deviations of fluorescence intensity and transmittance as low as 0.7962 % and 0.7109 %, respectively. Notably, the sensor demonstrates outstanding actual environmental temperature monitoring with recovery rates (98.05 %–99.64 %) and accurate skin temperature monitoring with recovery rates of 96.71 %–97.66 %, demonstrating potential for application as wearable flexible sensors.