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What are the uses of Photocatalysis in the building environment?

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There are many examples of photocatalysts aimed at reducing urban depollution applied on photocatalytic pavements. Titanium dioxide (Titania) is being explored as a component, but the correct method of applying photocatalysts in pavements is still being investigated. Mixed with the binder, the TiO2 was not effective in degrading NOx in the air. As a surface spray coating however, Titania was very effective in removing nitrogen oxide. 

 

Fungi and bacteria are the main causes for the degradation of building materials and also for many health-related issues; nanomaterials can be effective in tackling this problem, especially in indoor environments and building applications. Both Zinc Oxide and Titanium dioxide can be used for antibacterial coatings. Antibacterial activity of zinc oxide nanoparticles has received significant interest worldwide. Zinc Oxide is a metal oxide widely used in nanomaterial applications. It is a promising wide direct band gap semiconductor with low cost and simple production through a variety of fabrication methods. As for TiO2, adding it with a particle size of 21 nm to a bacterial colony was enough to destroy all bacteria within two hours. Similarly, the total degradation of E-coli, K- pneumonia and other bacterial colonies in the presence of Manganese doped TiO2 has been achieved. Hydroxyl radicals are the main factor responsible for the bactericidal capacity of photocatalysis and possess a destruction capacity 1000–10,000 times more effective than chemical disinfection products. Silver (Ag) incorporated into TiO2 or ZnO nanoparticles can strongly increase their antibacterial effectiveness. It has shown full bacterial destruction after just 2 minutes. A hybrid nanostructure of silver and zinc-oxide or titanium dioxide has proven to be effective as a coating on especially wooden surfaces in combating organic pollution.

 

Recently, TiO2 has been addressed as a coating for self-cleaning surfaces, minimising the effort for the cleaning maintenance of the building facades, or the use of them in photocatalytic paints for indoor air quality.

 

Moreover photocatalysts can be used for Cultural Heritage coatings, in order to prevent deposition of organic particulates. However, although they do not catalyse CO2, which is the main reason of stones darkening, they are effective in degrading uncombusted hydrocarbons.