The crucial role of amorphous surface layer in the antibacterial Ca/P/Al containing coating

Abstract The rise of the antibacterial microarc oxidation (MAO) coating satisfies the urgent application requirements in the field of biomaterials and biofouling, and the antibacterial activity of Ca/P/Al containing MAO coating is preliminarily disclosed to be related to the reactive oxygen species (ROS) and amorphous surface layer in our previous work. Herein, the specific antibacterial process and function of amorphous surface layer is further verified to be closely linked to the electron storage and galvanic corrosion in this work. The amorphous surface layer collects the electrons released by bacteria and causes the generation of extracellular ROS, meanwhile, the potential difference existing in the bilayer microstructure and electron/hole-rich areas leads to galvanic corrosion, disturbing the suitable H+ concentration gradient for bacterial metabolism, these processes synergistically cause the bacterial structural damage. Furthermore, the coating almost loses its remarkable antibacterial property once amorphous surface layer is entirely recrystallized after heat treatment, and amorphous surface layer determines the antibacterial performance of the Ca/P/Al containing MAO coating.