Bacterial infections are a major healthcare concern. Clinical application of photo‐activated quantum dots to efficiently treat bacterial infections has been hindered by inadequate production of reactive oxygen species. In this study, photoactive antimicrobial carboxyl‐functionalized graphene quantum dots (cGQDs) are synthesized with an exceptionally high singlet oxygen (¹O₂) quantum yield of 0.88. Compared to non‐functionalized GQDs, cGQDs exhibit over a 20‐fold enhancement in the ¹O₂ quantum yield. According to the density functional theory simulations, the dramatic increase of ¹O₂ quantum yield is due to significantly enhanced spin–orbit coupling between singlet and triplet excited states of GQDs with addition of ─COOH groups. Under low‐intensity blue light (5 mW cm^{− 2}), Staphylococcus aureus is completely eliminated with just 0.8 µg mL⁻¹ of cGQDs, and a minimum bactericidal concentration (MBC) of 0.4 µg mL⁻¹ is determined, representing the lowest MBC reported against S. aureus using light‐activated quantum dots. Layer‐by‐layer assembly of cGQD films also results in over a 99.9% reduction against multi‐drug resistant Staphylococcus aureus and Escherichia coli under illumination. cGQDs, both in suspension and as a nano‐assembled film, exhibit good cell viability in mammalian cells under both dark and light conditions. These results highlight the strong potential of cGQDs as an effective nanomaterial for antibacterial applications.

Candidozyma auris is an emerging opportunistic fungal pathogen that can cause serious catheter-related blood stream infections associated with high morbidity and mortality. The traditional antifungal treatment with polyenes, azoles or echinocandins is becoming less effective due to both intrinsic and developed resistance, complicating treatment. This study demonstrates the potent fungicidal activity of carboxyl-functionalized graphene quantum dots (cGQDs) against a panel of C. auris strains, spanning clades I to V, and a Candida albicans reference strain. Photoactivation of cGQDs in suspension with 435 nm blue light killed 99.9% of the fungi within 30 min even though the majority of test strains were resistant to at least one conventional antifungal. Moreover, cGQDs coated on flexible polydimethylsiloxane surfaces and commercial catheters via electrostatic layer-by-layer deposition with alternating positively charged polydiallyldimethylammonium polymer showed strong fungicidal activity against C. auris and C. albicans. These findings show that the cGQDs, both in suspension and in a thin film coating, have potential for future clinical development. In particular, their application to catheters may help prevent Candidozyma and Candida catheter-related infections.