Catalytic sterilization of Escherichia coli K 12 on Ag/Al2O3 surface

Bactericidal action of Al2O3, Ag/Al2O3 and AgCl/Al2O3 on pure culture of Escherichia coli K 12 was studied. Ag/Al2O3 and AgCl/Al2O3 demonstrated a stronger bactericidal activity than Al2O3. The colony-forming ability of E. coli was completely lost in 0.5 min on both of Ag/Al2O3 and AgCl/Al2O3 at room temperature in air. The configuration of the bacteria on the catalyst surface was observed using scanning electron microscopy (SEM). Reactive oxygen species (ROS) play an important role in the expression of the bactericidal activity on the surface of catalysts by assay with O2/N2 bubbling and scavenger for ROS. Furthermore, the formation of CO2 as an oxidation product could be detected by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and be deduced by total carbon analysis. These results strongly support that the bactericidal process on the surface of Ag/Al2O3 and AgCl/Al2O3 was caused by the catalytic oxidation.