Encapsulation of Zn/Co nanocrystals into sponge‐like 3D porous carbon for Escherichia coli inactivation coupled with ultrasound: Characterization, kinetics and inactivation mechanism

A sponge-like 3D Zn/Co co-doped porous carbon composite (Zn/Co-MPC) was successfully prepared using edible fungus residues as a template through a facile pyrolysis method in the current design. The optimized Zn/Co-MPC-0.3 composite was characterized by controllable release of bactericidal particles, fine sterilization ability and excellent magnetic recycle performance. The zinc oxide nanoparticles (ZnO NPs) and cobalt within the composite acted as an efficient killer of germs, while biochar could effectively achieve a controllable release of ZnO NPs and cobalt, endowing the Zn/Co-MPC composite with long-lasting antibacterial performance and eco-friendliness. High-frequency ultrasound, coupled with Zn/Co-MPC-0.3 composite, brought synergistic sterilization, contributing to the enhanced sterilization. The synergistic sterilization of Zn/Co-MPC-0.3 assisted with ultrasound caused a about 1.02-log CFU/mL reduction in Escherichia coli. Four kinetics models fitted well (R2 > 0.9), and the statistical parameters (R2 > 0.95 and smallest RMSE) of Log-linear and Weibull models fitting ultrasound-enhanced Zn/Co-MPC-0.3 treatment were fine. The sterilization mechanism of Escherichia coli by ultrasound-enhanced Zn/Co-MPC-0.3 treatment included the decreased enzyme activity, the broken cell membrane, and the loss of intracellular matter (protein, ATP, DNA). We argue that the ultrasound in combination with Zn/Co-MPC-0.3 treatment has a promising application in bacterial decontamination due to its advantages in eco-friendly characteristics and long-lasting antibacterial performance.