Inactivation of Staphylococcus aureus and Escherichia coli under various light sources on photocatalytic titanium dioxide thin film

Although photocatalytic TiO2 thin film has been considered for antimicrobial applications and is sensitive to light sources, its inactivation mechanism under various light sources is relatively unknown. This work elucidates the mechanism by which photocatalytic TiO2 thin film inactivates to Staphylococcus aureus and Escherichia coli under various light sources using a bacterial cell culture and the microscopic observation of bacterial cells. Experimental results indicate that antimicrobial behavior can only be activated when the light source exhibits emissions with a threshold energy that exceeds the band gap energy of anatase TiO2. The black light source with a stronger UV emission than the fluorescent lamp, is associated with an earlier bacterial growth inhibition phase. The bacterial inactivation mechanism of Staphylococcus aureus differs from that of Escherichia coli. The former suffers the detachment of the cell wall from cell membrane and the later undergoes a nucleoid pattern change from features of relaxation toward features of condensation.