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Thursday, 9th July 2009 (1336 views)

A team of researchers in the US have employed gold nanoparticles to create a new film that could lead to the development of documents that can 'self-erase' after a set period of time.

Scientists at Northwestern University in Illinois worked on the principle that the nanoparticles change colour depending on their proximity to one another.

"For instance, they are red when they are spread out but as they draw closer together, they become violet, blue and then colourless," lead researcher Bartosz Grzybowski told New Scientist magazine.

The researchers coated the nanoparticles with molecules that would make them congregate when blasted with ultraviolet (UV) light and sandwiched them in a gel between two layers of thin, red film.

Using UV pens, the team was able to produce a range of images but when the light source is removed, the nanoparticles return to their original state and the text disappears in the red background.

They were also able to control the length of time the images were visible from hours to days by adjusting the concentration of the molecule coating.

Popular Science said the nanoparticle film could be used to create limited-time travel tickets or even confidential documents that "wipe themselves clean".

 

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