Photocatalysis of Air Contaminants with Carbon Nanotubes (CNT)

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Carbon nanotubes (both single walled and multi-walled) and Titanium Dioxide (TiO2) are being explored for their use in the removal of air contaminants through photocatalysis.  This process decontaminates air by converting solar energy into chemical energy. The TiO2 catalyzes the reaction, creating hydroxide radicals and superoxides, which then react with organic compounds and biological pathogens in secondary reactions.  These biological contaminants and harmful organic compounds are reduced to simpler chemical products that are less harmful or benign.

Upon activiation by UV light, titanium dioxide generates electron-hole pairs that allow for the creation of the hydroxide and superoxides.  While this is useful for decontaminating air and other substances, the electron-holes go through recombination, severly limiting their effectiveness as a photocatalyst.  Researches have learned how to suppress this recombination effect by creating composite materials with Carbon Nanotubes (CNT).  CNTs are naturally conductive and naturally accept electrons from other materials.  By creating a composite, the CNTs accept the extra electron generated by the titanium dioxide, suppressing the recombination of the electron holes.

Researchers have been able to develop titanium dioxide and CNT composite films by using a Layer-by-Layer fabrication method to deposit alternating layers of oppositely charged species ontoa substrate.  In this fabrication technique, Mult-Walled CNTs (MWCNT) and titanium dioxide are suspended in a non-polar medium.  The result is an MWCNT layer that does not need to be oxidized with harsh chemicals, reducing the environmental health and safety impact of creating these photocatalytic films and reducing manufacturing costs.

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The function of photocatalytic MWCNT titanium dioxide thin films is to clean and decontaminate air.

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This technology has the potential to offer new and cost effective ways to decontaminate air.

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Carbon Nanotubes can enter deep into the lungs, enter the blood stream, and pierce cell walls, making them toxic to living organisms. They pose little risk to the in the finished goods of this application, since the CNTs are suspended in a matrix, but they pose a risk to humans during the manufacturing process. Additionally, the specific human health and ecological risks of CNTs depends on the speciric structure and size of the CNTs in question.

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