Antibacterial properties and mechanism of nanometer zinc oxide composites

Nanometer zinc oxide (nano ZnO) is frequently added as an antibacterial agent to matrix materials used widely in packaging applications such as food. Two antibacterial films were prepared with high antibacterial activity achieved through low doping: ZnO/linear low-density polyethylene (ZnO/LLDPE) and ZnO/polycarbonate (ZnO/PC). The antibacterial rates of both films against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were greater than 99.9 %, and their antibacterial performance value (R) was ≥ 5.9. Experiments were conducted using LLDPE and PC with varying chain mobility to verify that the commonly known three antibacterial mechanisms, namely soluble Zn2+ ions, reactive oxygen species (ROS), and direct contact between nano ZnO and bacteria, are not the primary mechanisms responsible for the antibacterial properties of the nano ZnO composite film. Furthermore, a new mechanism of inhibiting bacteria by nano ZnO irradiated photons was proposed to explain the high antibacterial rate of ZnO/PC films under the condition of limited nano ZnO migration. Understanding the antibacterial mechanism of nano ZnO in polymers will aid in the development of ZnO antibacterial agents that can effectively exert high antibacterial effects in matrix materials.