Nanometer photocatalyst are made from TiO2 grains, the sizes of which are under 20nm. After they absorb UV in sunshine and illum  

TiO2 photocatalyst principle:

Nanometer photocatalyst are made from TiO2 grains, the sizes of which are under 20nm. After they absorb UV in sunshine and illuminate lamp-house, the electrons on them are activated by UV and flies off, then produce electron holes, which have strong oxidation ability (the holes are produced, when the electrons are flying off). The electron has strong deoxidization ability, will produce oxidation anion free radicals and oxyhydrogen free radicals after reacting with H20 and O2 in air. They have strong oxidation ability, and can decompose the organic, contaminants, fume, and bacteria into hurtles CO2 and H2O . At the same time, the electrons make deoxidization reaction to deoxidize the oxygen in air.

filters-TiO2 Photocatalyst filter