Research Progress on the Application of Carbon Dot Intelligent Films in Food Freshness Monitoring and Preservation

The global food supply chain faces a severe challenge of waste caused by misjudgment of freshness. Traditional preservation and monitoring technologies are limited by issues such as insufficient stability, potential safety risks, and an inability to reflect quality changes in real time. Carbon dots (CDs), a class of zero-dimensional carbon-based nanomaterials typically with a particle size below 10 nm, have emerged as ideal functional materials for constructing a new generation of intelligent food packaging. This promise stems from their excellent properties, including tunable fluorescence, broad-spectrum antibacterial and antioxidant activities, UV-blocking capability, and the feasibility of green synthesis from natural biomass. This review systematically summarizes the synthesis strategies, key characterization techniques, and physicochemical properties of CDs. It focuses on elucidating the fabrication methods and performance modulation of intelligent CD-based films, employing natural polymers, synthetic polymers, and multicomponent composite matrices. The applications of such films for active preservation of various foods (e.g., fruits, vegetables, meats, and aquatic products) are detailed. Furthermore, the principles underlying their real-time, visual freshness monitoring, primarily based on response mechanisms to pH and volatile metabolites (e.g., amines), are thoroughly discussed. The synergistic mode integrating both preservation and monitoring functions is specifically analyzed. Finally, this review addresses the current challenges confronting CD-based intelligent films, such as scalable production, performance stability, environmental endurance, and the lack of standardized evaluation methods. Future research directions are also proposed, aiming to provide theoretical insights and technical pathways for developing efficient, safe, and environmentally friendly next-generation intelligent packaging materials for food applications.