Novel and Highly Efficient Antibacterial PLA Composites Prepared with Liquidambar Orientalis Oil and Ag@g-C3N4 Nanocomposite

Flexible PLA-based antibacterial composite films were prepared using a natural oil, Liquidambar orientalis, as bio-based plasticizer, and 2D graphitic carbon nitride (g-C₃N₄) decorated with Ag nanoparticles with a particle size of 10–30 nm as antibacterial agent (Ag@g-C₃N₄). This structurally designed antibacterial nanocomposite was synthesized with the preparation of g-C₃N₄ by high-temperature annealing followed by the reduction of silver salt onto g-C₃N₄. The Ag@g-C₃N₄ nanocomposite exhibited a surface area value of 18 g/m². PLA/Ag@g-C₃N₄ composite films were prepared with solution casting method by introducing 30 phr of L. orientalis oil and various amounts (1, 2 and 4 phr) of Ag@g-C₃N₄. It was found that 30 phr of L. orientalis oil successfully plasticized the PLA and reduced its glass transition temperature from 60 °C to 43 °C and its melting temperature more than 10 °C by reducing the strong interactions and hydrogen bonds between PLA chains. L. orientalis oil also acted as a dispersion agent for the Ag@g-C₃N₄ nanocomposite particles and significantly improved their antibacterial activity. Antibacterial tests performed using Gram-positive bacteria (Staphylococcus aureus ATCC 25923) and Gram-negative bacteria (Escherichia coli ATCC 25922 and Acinetobacter baumannii ATCC BAA 747) indicated that introducing a small amount of 2D Ag@g-C₃N₄ nanocomposite particles into PLA yielded superior antibacterial activity.