Upcycled carbon nanodot–reinforced PHBH/PBAT nanocomposites for potential active food packaging: Enhanced barrier, antibacterial, and biodegradation behaviours

초록

Although nanomaterials have been widely used to improve the performance of biodegradable polymers, few studies have considered the sustainability benefits of waste valorisation or the influence of nanomaterials on the soil degradation process. This study introduces waste-upcycled carbon nanodots as a novel solution to not only improve film performance but also enhance biodegradation kinetics in soil, providing new insights for designing sustainable packaging materials. Carbon nanodots derived from walnut shell waste (wCDs) were synthesised via a hydrothermal method and incorporated into poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) and poly(butylene adipate-co-terephthalate) (PBAT) blend matrices (PHBH/PBAT) via melt extrusion to fabricate biodegradable active packaging films. The synthesised wCDs were monodisperse with an average diameter of 2.45 nm, exhibited low cytotoxicity against Caco-2 cells, and showed intrinsic antibacterial activity owing to their abundant surface functional groups. The PHBH/PBAT nanocomposite films containing varying wCD concentrations (0.5, 1.0, 2.0, and 3.0 wt%) were systematically evaluated for their physicochemical and functional properties. The incorporation of wCDs enhanced the water-vapour and oxygen-barrier performances. Moreover, it provided strong antibacterial activity against E. coli in in vitro assays and in a model food challenge test using cheddar cheese, demonstrating concentration-dependent suppression. In addition, wCD loading accelerated the disintegration rate during the 60-day soil burial by promoting surface erosion and weight loss. These findings demonstrate potential of wCD-reinforced PHBH/PBAT nanocomposites as a sustainable approach for active food packaging materials. © 2026 Elsevier Ltd

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