First off, we must differentiate between short – term surface treatment agents and long – term, germ – destroying lacquers.
Copper: The bare metal is very effective against germs. However, it oxidizes very quickly developing an unattractive green – black Verdigris layer, composed of univalent, poisonous co p per oxi de I (Cu2O) and the black, less toxic copper oxide II (CuO).
Silver: Long since a disinfecting agent, ( i . e . in water filters and as an agent for anti – bacterial clothing, etc.), the use of silver has diminished primarily because bacteria have developed silver immunities. Silver nanoparticles are required to produce higher concentrations of silver ions for combatting bacteria . However, since these can also penetrate human cells, infiltrating the blood – cerebral – barrier, the ir usage is not recommended. Silver-nano particles are used to produce higher concentrations of silver ions to fight viruses. However, since they are also able to penetrate human cells and penetrate the blood-brain barrier, they should not be used.
Ultraviolet light: UVC light is rich in energy and capable of destroying germs, which is why is it used to sterilise water. However, radiation requires a shield to avoid damage to eyes and ski. However, in order to avoid skin and eye damage, irradiation must be shielded.
Photocatalytic active layers: As a rule , these are based on nano – titan oxide that makes use of catalysing oxygen and hydroxyl radicals which are rich in energy and can destroy germs. However, they only work in places exposed to intense, direct light and not in shade or darkness. On the other hand, the radical s reac t powerfully to li ght which not only destroys germs, but also embrittles the lacquer matrix or damages the base However, this only works where intense, direct radiation hits the surface; disinfection does not work in the shadows and in the dark. On the other hand, the radicals that arise during exposure are so reactive that it not only kills germs, but also brittles the paint matrix or attacks the substrate.