Photophysical properties of fisetin embedded in polymer matrix modulated by both bulk polarity and non-bonding interactions

Slow solvation dynamics and abundant non-bonding interactions in polymer matrix can modulate photophysical properties of guest chromophores. In this work, we used fisetin as a fluorescent probe to explore the microenvironment in poly vinyl alcohol (PVA) matrix and its effect on excited-state proton transfer (ESPT). Compared to in PVA solution, fluorescence of fisetin in PVA film is largely enhanced and ESPT barrier is increased. Both bulk polarity of PVA film and site-specific intermolecular hydrogen bonding between water and fisetin were determined to contribute to anomalous absorption and emission properties absent in solutions.