Donor–Acceptor Type Solvatochromic Flavonoid Materials Fluorphores for Polarity Sensing and Real-Time Temperature Monitoring

Electron donor–acceptor (D–A) molecules are emerging tools for designing sensitive luminogens, attracting significant research attention. However, due to poor quantum yields under certain conditions, current D–A fluorophores often suffer from fluorescence quenching in practical applications. Developing new D–A dyes and functional composites is crucial for expanding their applications. Here, a novel donor–acceptor type flavonoid dye molecule, namely “AFL”, exhibiting both polarity-dependent fluorescence emission wavelength shift and viscosity-dependent intensity change, for polarity measurement and temperature sensing is designed and synthesized. Because the intramolecular charge transfer (ICT) can be enhanced by a decrease of excited state energy caused in high-polarity organic solvents, AFL undergoes fluorescence emission wavelength shift that shows fluorescence color response to solvents of different polarities and hence differentiates between them. Moreover, the actual temperature can be monitored by the as-designed AFL@tetradecanoic acid (AFL@TA) sensor. By combining with TA, viscosity sensitively changes upon the temperature change of insoluble composites, thus realizing the fluorescence intensity response to temperature. Remarkable recyclable performance and satisfactory mechanical properties are integrated. This study provides a promising approach to developing a new D–A fluorescent probe and furnishes perspectives on the potential of such D–A type flavonoid material in stimuli-responsive systems with a focus on visualization sensing technology.