Figure 4.

Number of viable colony counts of E. coli after incubation on pure and Cu-doped thin films on microscope slides. The number of viable colony counts were determined after (a) 3, (b) 6, and (c) 18 h. L+ = illuminated and L– = not illuminated (in the dark). * Indicates E. coli levels below detection limits. (d) Multitude of possible mechanisms via which Cu-doped ZnO is able to disinfect contaminated surfaces. The differing mechanisms of attack that destroy cell membranes, DNA, and proteins of the microbes make the development of resistant strains virtually impossible.