Prussian Blue for information storage

Jan 17, 2007

In the family of Prussian blue, there is a compound that can act as a switch: it is not magnetic at the outset, but it can become magnetized by the effect of light and return to its initial state by heating. Researchers of the Institute of Molecular Chemistry and Materials of Orsay (CNRS/University of Paris XI) and the Laboratory of Inorganic Chemistry and Molecular Materials (CNRS/University of Paris VI) showed that this change of state is due to the collective modification of the position of the atoms, induced by light.

Such compounds, which can memorize binary information, could be used as storage bits for future computers. This work was presented in the journal Angewandte Chemie International Edition (after the online publication of January 9, 2007).

In the field of computers, society's demand for capacity to store information is increasing exponentially and has led to the development of the nanosciences: storing ever larger quantities of information in volumes as small as possible and as rapidly as possible. The first hard disk, the RAMAC, built by IBM in 1954, weighed one ton and stored five megabytes. In today's portable computers and MP3 readers, the hard disks store several gigabytes and weigh only a few hundred or even a few dozen grams.

To further miniaturize these devices and to give users greater freedom, many chemists are making new switchable materials, i.e. ones that can switch from one state (OFF = 0) to another (ON = 1) by the effect of an outside impulse (variation of temperature, pressure, light, magnetic or electrical impulse), keeping the memory of the state in which they were found. The chemists of the two teams hope in this way to succeed in storing information on the scale of a few atoms.

They are working on Prussian blue. By replacing some of the atoms or iron with cobalt, they transform this pigment known since ancient times into a compound that can act as a switch: illuminated by a red light at low temperature (-150°C), this compound shifts from a non-magnetic state (OFF) to a magnetic state (ON) in a way that is stable over time. If it is heated, it returns to the OFF state. This change of state is due to the transfer of an electron from the cobalt to the iron (and vice-versa), by absorption of light or thermal energy.

Today, using synchrotron radiation, chemists have observed a collective modification of the position of the atoms in space, induced by the shift of the electron from one atom to the other. When the electron goes from the iron atom (OFF state) to the cobalt atom (ON state) due to the red light, the three-dimensional links between the cobalt, nitrogen, carbon and iron atoms, which were initially bent, become linear. This structural modification is responsible for the existence of this magnetic state and its stability over time.

This knowledge on the atomic scale of the mechanisms associated with ON/OFF switching is an essential first step for chemists towards imagining materials that could be used by industry to store information on the scale of a few atoms.

These new compounds perfectly reproduce the storage function of traditional components. As it will soon be impossible to reduce the size of the current components without having them lose their memory functions, chemists are dreaming up materials that could take over and meet society's demand for miniaturized information storage.

Source: CNRS

Explore further: Space-tested fluid flow concept advances infectious disease diagnoses

add to favorites email to friend print save as pdf

Related Stories

Chemists settle debate about conversion of light

Apr 02, 2014

Chemists of Utrecht University and of the Foundation for Fundamental Research on Matter (FOM) have settled the debate about a fundamental question that is relevant to the conversion of one colour into another. ...

The promise and peril of nanotechnology

Mar 26, 2014

Scientists at Northwestern University have found a way to detect metastatic breast cancer by arranging strands of DNA into spherical shapes and using them to cover a tiny particle of gold, creating a "nano-flare" ...

Follow the ant trail for drug design

Mar 18, 2014

New drugs often fail because they cause undesirable side effects. ETH researchers have developed simulation software that predicts the properties of active agents and virtually builds new ones. The software's search process ...

Recommended for you

User comments : 0

More news stories

Treating depression in Parkinson's patients

A group of scientists from the University of Kentucky College of Medicine and the Sanders-Brown Center on Aging has found interesting new information in a study on depression and neuropsychological function in Parkinson's ...

Impact glass stores biodata for millions of years

( —Bits of plant life encapsulated in molten glass by asteroid and comet impacts millions of years ago give geologists information about climate and life forms on the ancient Earth. Scientists ...