1. In the world of particles, a silver ion is the smallest physical form of silver possible.
2. An elemental particles(metallic silver) cannot be made smaller than it's single most basic form. - see: ion w/ electron
That said the single smallest particle size possible is that of a reduced silver ion. Whereas an HVAC particle(for example) will be several times larger than any reduced ion no matter the process. And while this would not encompass all home brewed solutions. It remains that most any CS solution brewed within the saturation limits would easily outperform any HVAC CS solution in terms of particle size and surface resolution.
Likewise, any heat reduced(none additive based) silver particle solution made in the same way, would easily outperform any HVAC solution(such as Utopia /Mesosilver etc) which suffer from particle flocculation(cluster chains). And why we end-up with heat reduced Colloidal Silver that are a glowing gold color vs the muddy, tea colored solutions that come from HVAC. Which works out to be the most obvious proof that the particles are substantially larger.
Hope this helps.
PS. I apologize if this looks as though I'm presenting information to undermine your personal friend's research or business though I'd add that this is not my intent.