The transparency of CoMnCuZnAg-IOC is similar to both the spray-coated ones and the pristine substrates, as recognized by the naked eyes (Figure ). Such the observation remains the same in the microstructural morphology revealed by the scanning electron microscope images (Figure ). The transmittance values of the hand sprayerand immersion-coated samples at 550 nm (using the pristine glass sample as blank) are 99.62 ± 0.39% and 98.91 ± 0.20%, respectively (Figure ). The XPS data (Figure ) of CoMnCuZnAg-IOC show the composition variations (i.e. elemental ratios among each element) less than 2.62%, much more reproducible than those produced by the spray method. By directly conducting E. coli viability tests on these IOC samples, the antibacterial activities of each element can be more accurately evaluated. Figure indicates an increase in the order of antibacterial activities of CoMn-IOC (60.14% viability), CoMnCu-IOC (27.34%), CoMnCuZn-IOC (12.59%), and CoMnCuZnAg-IOC (0.21%), which is consistently observed in the bacteria cultures (Figure ). In CoMn-IOC, the bactericidal effect is contributed by both Co and Mn as a bacterial cell membrane disruptor. The spiking of Cu significantly lowers the bactericidal viability by 32.80%, greater than that by spiking of Zn (14.75%) and Ag (12.38%). If under the same concentrations, Ag and Zn should have intrinsically higher antibacterial activities than Cu. But in this case, Cu 2+ is observed to have higher quantities in the coating than the other two metals (Table ), which means that the high bactericidal activity should come from the dominated quantity instead of the intrinsic properties. As such, the presence of Zn and Ag, even in much smaller contents, is necessary to achieve nearly 100% bactericidal activities, hence giving a higher advantage for a multimetal coating.