Tired of washing your clothes? In the future, the chore might be as easy as hanging them in the sun, according to researchers who have developed a type of self-cleaning cotton. The idea is not totally new: Coatings such as titanium dioxide have long been known to have self-cleaning properties. When light strikes, the compound emits oppositely charged particles known as electron-hole pairs, which encourage so-called oxidation reactions, breaking down organic material such as dirt. But the light has to be ultraviolet, which makes up only a small percentage of sunlight and which, therefore, makes this process inefficient for everyday use. Now, however, the researchers have tried coating cotton with nitrogen-doped titanium-dioxide (N-TiO2) and an extra layer of silver-iodide (AgI). In visible light, the N-TiO2 and AgI seem to work together, forcing any generated electrons and holes to separate so that they stand less chance of recombining—ultimately making them more efficient at oxidation. In their report, due to be published later this month in Applied Materials & Interfaces, the researchers describe how a piece of treated cotton stained with orange dye self-cleaned when exposed to a 1000 Watt lamp for 2 hours. But what if you do actually want to wash this special cotton? It's OK: the self-cleaning coating stays put.
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