Fluorescence Resonance Energy Transfer in Gelatin-Based MOF/N-CDs Films for Superior Photodynamic Antibacterial Packaging Materials

Iron-based porphyrin metal–organic frameworks (Fe-PM) are known for their photodynamic microbial inactivation (PDI) in food packaging. However, their limited generation of reactive oxygen species (ROS) reduces their efficiency. In this study, we introduced a fluorescence resonance energy transfer (FRET) pair using nitrogen-doped carbon dots (N-CDs) as the donor and Fe-PM as the acceptor to boost singlet oxygen (1O2) production. Incorporating Fe-PM@N-CDs into a gelatin polymer film significantly enhanced the antibacterial activity against both Gram-positive and Gram-negative bacteria within 10 min under white LED light. Additionally, the gelatin/Fe-PM@CD composite film showed an improved tensile strength of 93.53 MPa, biodegradability of 68%, and preserved fresh green grapes, destroying 97% of the microorganisms and preventing discoloration and water loss for up to 7 days. These findings demonstrate the potential of this composite film for antibacterial food packaging applications.