Colloidal silver, which is often coated in porous ceramic water filters, prevents the growth of microbes trapped in the micro- and nano-scale pores of the filter.
Other metals such as copper and zinc have also been shown to exhibit anti-microbial activity. Researchers from Princeton University in New Jersey used atomic force microscopy (AFM) measurements to study the adhesion interaction between Escherichia coli
) bacteria and colloidal silver, silver nanoparticles, and copper nanoparticles, as well as the interactions of the bacteria and the three different types of metal to porous clay-based ceramic surfaces. As reported in the American Institute of Physics' (AIP) Journal of Applied Physics
, of the three antimicrobial metals studied the silver nanoparticles had the highest affinity for E. coli
bacteria. The colloidal silver had the highest affinity for a porous ceramic surface and is therefore the least likely to leach into the filtrate. However, since the adhesion between colloidal silver and E. coli
is in the same range as the adhesion between copper and the bacteria, copper may have potential as a less expensive disinfectant coating for ceramic water filters.