Pollutants found inside office buildings can be converted into less harmful substances by a photochemical device that works continuously  from night to day, claim scientists in Japan. This could prevent cases of sick building syndrome. 

Sick building syndrome is a combination of acute health and comfort issues that appear to be linked to time spent in a building, often in an office. This can be caused by inadequate ventilation or volatile organic compounds (VOCs), such as formaldehyde that are emitted by chemical contaminants from carpeting, upholstery, manufactured wood products, or photocopying machines and cleaning agents. 

Titanium dioxide (TiO₂) photocatalysts have been applied to environmental remediation and self-cleaning coatings. However most only work under UV light, which means they don't operate during the night. Now, Tetsu Tatsuma and colleagues at Tokyo University have overcome this problem by designing a photocatalyst with the ability to store photochemical energy. 

Tatsuma's photocatalyst has two layers; an TiO₂ underlayer and an Ni(OH)₂ overlayer. As the light is shone onto the device, its energy can be captured by the TiO₂ underlayer and stored in the Ni(OH)₂ overlayer. This stored energy is used to oxidise harmful VOCs, in particular formaldehyde, into less innocuous carbon dioxide and water, at any time. 

In practice, Tatsuma expects the device to trap the harmful VOCs on the TiO₂-Ni(OH)₂ film during the night, then in the morning light, the pollutants are oxidised into less harmful by-products. Tatsuma has high hopes for his device and says 'we hope to apply it to private houses, offices and factories as coatings in curtains, window blinds and ceilings'. 

This device has the potential to improve indoor air quality and reduce the risk of illness by removing formaldehyde from the work environment. Mark Clayton, a Public Health Service Officer from the US EPA Indoor Environments Division, believes that this system 'could represent a significant advance in potentially reducing airborne concentrations of chemical compounds commonly found in an environment where most people spend 90 percent of their time. Employment of such a photocatalyst may have the potential to make a substantial contribution to ongoing efforts to improve air cleaning devices.' 

Emma Shiells 

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