Aromatic Ketone‐Derived Photosensitizers for Boosted Photodynamic Antibacterial Performance

Comprehensive Summary Aromatic ketones, such as 9‐fluorenone (9‐FO), are known for their high intersystem crossing quantum yields ( Φ ISC ≈ 1), rendering them highly valuable for photochemical reactions and dye‐sensitized solar cells. However, their use as photosensitizers in biological contexts has been hindered by their low extinction coefficients, high excitation energies, and weak fluorescence. To address these limitations, we conjugated 9‐FO with a fused‐ring electron donor, resulting in an acceptor‐donor‐acceptor derivative IDT‐9F. This strategy has successfully redshifted the absorption peak of 9‐FO (380 nm) into the visible light range (498 nm) and significantly enhanced its light absorption capability (~310‐fold) and fluorescence quantum yield (~100‐fold). Furthermore, IDT‐9F was encapsulated within pH‐responsive nanoparticles using an acid‐induced charge‐reversal polymer as the amphiphilic matrix, and enabled fluorescence imaging‐guided photodynamic inactivation of Gram‐positive bacteria in acidic environment with a remarkable bacterial inhibition rate exceeding 99.9%.