The photocatalysis is "the acceleration of a photoreaction in the presence of a catalyst". A catalyst neither changes nor is consumed by a chemical reaction.
A large number of studies have been published on the use of titanium dioxide as a photocatalyst for the decomposition of organic compounds: following light exposure, the titanium dioxide produces Reactive Oxygen Species (RSO), that reacts with the organic substances, producing non-toxic inorganic substances.
The absorption of Ultraviolet radiations - coming from the sun (UV) or from an artificial light source (fluorescent lamps)- by the titanium dioxide, generates electron-holes pairs. The hole (positive) of the titanium dioxide decomposes the water molecules into hydrogen and in hydroxyl radical ions. The electron (negative) reacts with the oxygen molecules and forms superoxide ions. This cycle, that continues as long as the photocatalyst is illuminated, represents the general mechanism of the photocatalytic reaction of titanium dioxide.
It is just the formation of Reactive Oxygen Species that acts as a bactericidal and virucidal: in fact, a large number of studies provide the same evidence: the hydroxyl radical is the main species involved in the bactericidal and virucidal action of the photocatalysis.
The hydroxyl radicals have an extremely short duration and must be generated near the membrane so that they are able to oxidise some components. Their extremely short life time and their surface production, make them harmless to humans.
The most powerful advanced oxidation systems are based on hydroxyl radical generation, that is an extremely powerful oxidising agent. For its oxidative capacity, the photocatalyst oxidation can effectively sanitise, deodorise and purify air, water and surfaces.
Photocatalysis not only kills the bacteria cells, but decomposes them. It has been proved that titanium dioxide is more effective than any other antibacterial agent, because the photocatalytic reaction occurs even when there are cells covering the surface, and the multiplication of bacteria is active. In addition, the endotoxin resulting from the death of the cell is decomposed by photocatalytic action. The titanium dioxide does not deteriorate and provides a long term antibacterial and virucidal effects.
In general, the sanitation using the titanium dioxide results 3 times more effective than that achieved with chlorine, and 1,5 times more effective than that with ozone.