The Power of PhotocatalysisThe natural decomposition of organic matter can be accelerated by the use of a photocatalyst such as titanium dioxide (TiO₂).
Upon exposure to light (with energy above the TiO₂ band gap), energy-rich electron-hole pairs are produced. When applied to any material such charge carriers interact with ambient oxygen and water, generating highly reactive hydroxyl radicals and superoxide.
These radicals can either directly attack the surrounding microbial matter or recombine following different pathways forming hydrogen peroxide.
Hydroxyl radicals, superoxide radicals and hydrogen peroxide are the reactive oxygen species (ROS) ultimately responsible for the biocidal activity of ACT CleanCoat™ through non-selective oxidation of organic material.
The catalyst is never consumed during the reaction, ensuring a continuous process during the service life of the coating. The TiO₂ particles in ACT CleanCoat™ are specifically engineered to work in all environments.
The free radicals are produced on the surface of the TiO₂ by photocatalysis. This reaction occurs in the presence of light, water and oxygen.
The reaction is activated by the energy of light. The titanium dioxide acts as a catalyst for this reaction. When TiO₂ is exposed to light, it will generate electron-hole pairs. These will facilitate redox reactions through the formation of absorbed free radicals on the surface.
Non-metal doping induced localised states
The chemistry behind ACT CleanCoat™
The light-induced oxidation process breaks down organic pollutants by locally producing free radicals from ambient humidity and oxygene.
Free radicals induce oxidative stress, and they attack all major classes of biomolecules, mainly the polyunsaturated fatty acids, also known as lipids, of the cell membranes.
The free radicals in ACT CleanCoat™ work by oxidation and attack the cell membrane of bacteria.
The oxidative degradation of lipids, known as lipid peroxidation, is very destructive as it proceeds as a self-perpetuating chain reaction. After the destruction of the cell wall, the free radicals will proceed to oxidize the cell core.
Because of the high oxidative rate constant of the free radicals, the oxidations of cells will create water, carbon dioxide and minerals. Both the water and carbon dioxide evaporates – only residuals on the surface are minerals from the cells.
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