Fluorescence Switching for Temperature Sensing in Water br

A water-soluble thermochromic molecular switch with spectrally resolvedfluorescence in its two interconvertiblestates can be assembled in three synthetic steps by integrating afluorescent coumarin chromophore, a hydrophilic oligo(ethyleneglycol) chain, and a switchable oxazole heterocycle in the same covalent skeleton. Measurements of its two emissions in separatedetection channels of afluorescence microscope permit the noninvasive and ratiometric sensing of temperature at the micrometerlevel with millisecond response in aqueous solutions and within hydrogel matrices. The ratiometric optical output of thisfluorescentmolecular switch overcomes the limitations of single-wavelengthfluorescent probes and enables noninvasive temperature mapping atlength scales that are not accessible to conventional thermometers based on physical contact.