Changing colours with magnetism

US researchers have discovered a way to change the colour of iron oxide nanoparticles using magnetism, which could be used in high quality display screens and electronic paper.

University of California, Riverside nanotechnologists found that by changing the strength of the magnetic field, they were able to control the colour of tiny particles of iron oxide suspended in water.

When the strength of the magnetic field is changed, it alters the arrangement of the spherical iron oxide particles in solution, modifying how light falling on the particles passes through or is deflected by the solution.

‘The key is to design the structure of iron oxide nanoparticles through chemical synthesis so that these nanoparticles self-assemble into three-dimensionally ordered colloidal crystals in a magnetic field,’ said Yadong Yin, an assistant professor of chemistry who led the research.

‘By reflecting light, these photonic crystals show brilliant colours,’ Yin said. ‘Ours is the first report of a photonic crystal that is fully tuneable in the visible range of the electromagnetic spectrum, from violet light to red light.’