Scientists have developed an information storage method that could be used in memory devices for computers and digital cameras.
 
Ben Feringa at the University of Groningen, the Netherlands, and colleagues investigated dithienylethene compounds that change colour in response to light. Dithienylethene molecules can exist in two states: ring-open, which is colourless, and ring-closed, which is coloured.  Ultra-violet and visible light cause the molecules to interconvert between the two states in a process known as photochromism.  The researchers said this property could be used to record information onto the material.

The researchers measured the infra-red (IR) and Raman spectra of the molecules. Large differences between the Raman spectra for the open and closed forms of the molecules mean that Raman radiation could be used to read the stored information, said Feringa. Because Raman radiation does not cause photochromism, it could be used to read the information many times, without destroying it.  This is known as non-destructive readout and is crucial in the design of molecular memory devices.

Kingo Uchida, an expert in photochromic materials from Ryukoku University, Japan, recognised the importance of the findings.  'Reading by using IR and Raman gives no reaction and no change in the recorded information.  Without using such IR and Raman readout light, there is no meaning to the photochromic recording.'

Feringa's team are now developing devices made of several compounds, to allow more information to be stored on the material.  Team member Wesley Browne said, 'an important challenge is to develop stable multi-component systems where each component can be switched independently between open and closed forms and where the state of each component can be read independently.' 

Joanne Thomson