Development of fluorescent microgel thermometers based on thermo responsive polymers and their modulation of sensitivity range

Fluorescent molecular thermometers based on thermo-responsive linear polymer molecules such as poly(N-isopropylacrylamide) ( PNIPAM) labelled with a polarity-responsive fluorescent molecule benzofurazan ( BD) are the most sensitive known. Thermo-responsive PNIPAM and some related polymer microgel particles labelled with BD by emulsion polymerization have been prepared and their fluorescence properties in water as fluorescent thermometers studied. All the cross-linked polymer microgel particles dispersed in water fluoresce strongly as soon as each threshold temperature is exceeded. The nine kinds of microgel dispersion developed in this work thoroughly cover the sensitivity range from 18 to 47 degrees C. They are not only more sensitive than the previous fluorescent molecular thermometers based on other principles but also highly reproducible in their behaviour.