No More Cleaning? Nanotechnology Will Fix It!
 

Scientists at Leibniz Universität Hannover Develop Coatings for Self-Cleaning Surfaces.

The self-cleaning house may still be a pipe dream, but nanotechnology is already making everyday life easier. This is all thanks to coatings based on titanium dioxide. The white inorganic powder is applied to surfaces. If the layer is thinner than 100 nanometres (or ten times thinner than a human hair) it is transparent, and invisible even on glass. The influence of light leads to two effects: first, droplets cannot be formed and water spreads in a thin film over the entire surface. Second, organic dirt on the surface of the titanium dioxide layer is actively destroyed through so-called photo catalysis. "Organic molecules such as fats and oils are completely degraded through the photo-catalytic effect when they are exposed to UV light, whereby the dirt particles are unable to adhere to the surface and are washed away by the next rain," explains Prof. Detlef Bahnemann from the Institute of Chemical Engineering at Leibniz Universität Hannover.

Until the end of July 2008, scientists at Leibniz Universität Hannover took part in a three-year joint research project sponsored by the Federal Ministry of Education and Research (BMBF) into "Raising the active and passive safety of vehicles through innovative multifunctional nano coatings – NanoSafe." The aim of the project was to develop coatings that would last as long as possible and not need to be renewed. Work carried out by researchers at Leibniz Universität Hannover included the transparent coating of the rear windows of cars, with a titanium dioxide solution being applied during production. The effectiveness of this coating is currently being tested in the laboratory at the Institute of Chemical Engineering. "The tests show good results, but it will probably take a long time until it can go into mass production," says Professor Bahnemann.

The scientists in Hannover have also been trying to prevent headlights from steaming up as well as working on the development of self-cleaning coatings for instruments and fittings in vehicle interiors. One problem they face: photo-catalytic self-cleaning has so far functioned only with UV light. For this reason, the researchers aim to develop catalysts that can be activated by visible light and thus also function in vehicle interiors.

Nitrogen oxides, such as NO and NO2 can actually also be degraded through photo catalysis. These gaseous compounds are produced for example during combustion in power stations and vehicles. When breathed in, nitrogen oxides are hazardous to health, and EU directives require a significant reduction in the maximum permissible concentration from 1st January 2010. “The idea is to coat as many surfaces of buildings, streets and pavements with photo catalysts as possible,” says Professor Bahnemann. "Of course the whole thing is only second best technology. The best thing would be to prevent the production of nitrogen oxides in the first place."

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