Chemistry - What is the origin of the bactericidal properties of silver in water?

Solution 1:

Silver is not as inert as gold. Tarnish is the name we give to the phenomenon when silver metal is oxidized and becomes a salt. Surfaces made of silver tend to disinfect themselves pretty quickly. As for disinfecting water poured into a silver cup, I imagine that would take a little longer since you have to wait for silver to diffuse away from the surface and into the solution. But even very trace levels of silver can have strong antimicrobial effects.

Solution 2:

As far as I know, a chunk of solid silver will not spontaneously react with water. But if you pass an electrical current through silver electrodes immersed in water, the silver will be oxidized according to the following equation:

$$\ce{2H2O(l) + 2Ag(s) -> 2Ag+(aq) + H2(g) + OH- (aq)}\qquad E^\circ=-1.63\ \mathrm V$$

That will get you the ions you need. Incidentally, Russia's MIR space station and the ISS use electrolytically dissolved silver ions to purify drinking water.

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Solution 3:

As to the above answers I also want to include the mechanism of action of silver as an antimicrobial agent. The exact mechanism of action of silver as an antimicrobial agent is not known and the current hypothesis is silver will converted to silver ions and this positively charged ions will attack the cell membrane, DNA or proteins which are negatively charged thus inhibiting the growth of microorganisms.

See also this link.