Kafeel Ahmad, Jong-Whan Rhim
The global drive to improve food safety, extend shelf life, and reduce food waste has necessitated the development of efficient, sustainable, and viable active and intelligent packaging solutions. Carbon dots (CDs) synthesized from biomass and food waste have become globally accepted nanoparticles with excellent optical, antimicrobial, and antioxidant properties, making them ideal candidates for monitoring and preserving perishable foods. Their production through green synthesis routes aligns with the principles of the circular economy while providing multifunctional sensing capabilities. This review establishes the mechanisms governing CD-based sensing—including quenching, enhancement, and ratiometric detection—and highlights their role in identifying critical food quality indicators such as pH, volatile amines, and microbial contaminants. In addition, this review addresses important safety and biocompatibility aspects, specifically investigating CD migration and emphasizing that short-term in vitro cytotoxicity tests (often known to show high cell viability) are insufficient as safety tests alone, and that in vivo studies can reveal lethality or chronic toxicity based on surface chemistry. The main challenges, including scalability of synthesis, regulatory hurdles, and consumer-related barriers such as perceived accuracy and economic deterrents, are outlined. Altogether, CDs represent a prospective class of sustainable nanomaterials that will enhance next-generation technologies in smart food packaging.