Preparation of MoS2 modified with carbon quantum dots and its application to extremely high oxygen-barrier nanocomposite films for packaging

Polyvinyl alcohol (PVA), a biodegradable polymer, has attracted considerable interest in the food packaging industry. However, the efficacy of PVA films as food packaging materials is limited owing to their inherently highlight transmittance, hydrophilicity, and solubility in water. Emerging two-dimensional materials, particularly transition metal dichalcogenides, exhibit significant potential in enhancing the mechanical, thermal, optical, ultraviolet-blocking, and oxygen barrier properties of polymer-based nanocomposites. In this study, few-layered water-dispersible MoS₂ nanosheets were synthesized via ultrasonic mixing and liquid exfoliation and integrated with Ag-doped nitrogen-functionalized carbon quantum dots (Ag-NCQDs), referred to as MoS₂-Ag-NCQDs. Incorporating only 1 wt% of MoS₂-Ag-NCQDs into a PVA matrix resulted in notable improvements in crystallinity, thermal stability, and oxygen barrier properties. The improved crystallinity of the polymer matrix constrained the gas molecule mobility by increasing diffusion pathways and lowering the permeation rates. Notably, the incorporation of MoS₂-Ag-NCQD nanomaterials significantly enhanced the oxygen barrier performance, yielding a 99.8 % reduction in the oxygen transmission rate with that of pure PVA films. This remarkable improvement is attributed to the enhanced crystallinity, high aspect ratio, and superior exfoliation of the MoS₂ nanosheets, which facilitate effective interactions with gas molecules and impede their movement. Furthermore, the PVA/MoS₂-Ag-NCQDs nanocomposite films significantly improved ginger's preservation and nutritional integrity, thereby extending its shelf life. This study highlights the potential of MoS₂-Ag-NCQD nanomaterials for improving oxygen barrier performance, advancing pharmaceutical applications, and enhancing ultraviolet shielding when used in food packaging systems.