Off/On Fluorescent Nanoparticles for Tunable High‐Temperature Threshold Sensing

Abstract Herein, a versatile threshold temperature sensor based on the glass transition temperature‐triggered fluorescence activation of a dye/developer duo, encapsulated in polymeric nanoparticles is reported. The emission enhancement, detectable even by unaided eye is completed within a narrow temperature range and activates at adjustable threshold temperatures up to 200 °C. Fluorescence is chosen as sensing probe due to its high detection sensitivity together with an advanced spatial and temporal resolution. The strategy is based on nanoparticles prepared from standard thermoplastic polymers, a fluorescence developer, and the commercially available Rhodamine B base dye, a well‐known and widely used fluorescent molecule. By making nanoparticles of different thermoplastic polymers, fast, abrupt, and irreversible disaggregation induced fluorescence enhancement, with tunable threshold temperature depending on the nanoparticles polymer glass transition is achieved. As a proof‐of‐concept for the versatility of this novel family of NPs, their use for sensing the thermal history of environments and surfaces exposed to the threshold temperature is showed.