PVA /Tea Leaf–Derived Carbon Quantum Dots Nanocomposites for Enhanced Barrier and Antimicrobial Food Packaging Films

다국어 초록 (Multilingual Abstract)

This study explores the multifunctional enhancement of polyvinyl alcohol (PVA) films through the incor- poration of tea leaf–derived carbon quantum dots (CQDs) at loadings of 0.5, 1.0, 2.0, and 3.0 wt.%, focusing on struc- tural, optical, mechanical, antimicrobial, and barrier properties. FTIR spectroscopy revealed strengthened hydrogen bonding and compatibility between PVA and CQDs, with broadened O-H stretching peaks indicating interactions with CQDs surface groups. XRD analysis showed preserved semi-crystalline PVA structure with increased crystallinity at higher CQDs loadings, suggesting uniform dispersion without phase separation. Photoluminescence spectra demonstrated strong blue emission from CQDs at 450 nm upon 360 nm excitation, attributed to quantum confinement and functional groups. Tensile testing indicated significant improvements in stress at break (from 25.01 MPa for pure PVA to 83.28 MPa at 3.0 wt.% CQDs) and Young's modulus (from 26.09 MPa to 115.84 MPa), highlighting reinforcement effects. Oxygen transmission rate decreased markedly from 6.32 cc/m²·day for pure PVA to 0.11 cc/m²·day at 3.0 wt.% CQDs. UV shield- ing was enhanced by the incorporation of CQDs, achieving complete UV-B blocking at 2.0 and 3.0 wt.% loadings and over 75% UV-A blocking at 3.0 wt.%, while maintaining visible transparency. Antibacterial disk diffusion assays exhib- ited concentration-dependent inhibition zones, maximizing at 3.0 wt.% CQDs, likely due to reactive oxygen species gen- eration and electrostatic interactions.