Colour changing pigments

Researchers from Southampton University and Loughborough University are developing new colour changing pigments for a  range of applications including security marking on banknotes and limiting overheating in greenhouses.

'We are working to create materials that change colour in response to heat and light as well as developing more environmentally-friendly pigments,' said Dr Sandie Dann from Loughborough University. 'These new materials will provide colour and optical effects with diverse applications in automotive, cosmetic, banking and security industries.'

Recently, the researchers have developed some new pigments that have the bright colours and the temperature stability of traditional inorganic pigments, but are inherently non-toxic.

The materials are based on a niobium stannate system with small amounts of sulphur incorporated to tune the colour. The pure oxide is vibrant yellow, but by increasing the sulphur content of the mixture the colour can be tuned through orange to red. The pure oxide is also thermochromic. Although yellow at low temperature, above 50°C it changes rapidly to bright red.