Titandioxid

Since many years the semiconductor titanium dioxide (TiO2) is used in foods (E171, e.g. Salami-peel) cosmetics (e.g. sun crème, toothpaste) and drugs (e.g. dragées) because of its properties as a white pigment and its physiological harmlessness.

Titanium dioxide also acts as a photocatalyst, – i. e. as a sensitizer for light induced redox-processes. The principle is based on absorption of photons of certain energy (UV or visible) whereby electrons are lifted from the valence band to the conduction band. Thereby free electrons and electron holes are created and can oxidise or reduce adsorbed pollutants directly. The degradation of pollutants is also done by intermediate radicals from water and oxygen. As reaction products superoxide, hydroxyl-radicals and hydrogen peroxide are formed. This can degrade organic substances and facilitate the antimicrobial action. The photocatalytic effect of titanium dioxide in combination with UV-/visible light might be used on surfaces of filling machines, machine parts or packaging materials. By durable coatings a continuous long-term effect for disinfection, degradation of persistent biofilms or organic residues should be enhanced or the formation of biofilms should be prevented. By the beneficial hydrophilic properties of TiO2 containing surfaces the cleaning can be eased, or the attachment of microorganisms, biofilms or other particles can be prevented.