Scientists in India have found the key to protecting information at a molecular level.

A molecular keypad lock using a novel organic compound as a chemosensor has been made by Amitava Das and his colleagues at the Central Salt and Marine Chemicals Research Institute, Gujarat.

Das synthesised 1-amino-8-naphthalene sulfonic acid ester, and found that it fluoresces when it comes into contact with copper and mercury. And that when more than one substrate is used, the fluorescence response depends on the order the substrates are added. For example, adding copper followed by fluoride produces a different response to adding fluoride followed by copper. The effect is caused by the different fluorescent properties and kinetic stabilities of the complexes formed.

The group then demonstrated the extension of this concept to a molecular keypad lock, with copper and fluoride acting as the two inputs and the fluorescence response as the output. Das hopes this idea will provide the basis of molecular logic gates for security purposes, 'Although the keypad lock demonstrated here can only process a password limited to two input bits, it inspires the imagination towards the development of the next generation of confidential identification technologies,' he says.

Uwe Pischel, an expert in molecular logic devices at the University of Huelva, Spain, agrees, 'The mimicking of complex logic functionality, like a keypad lock, with a surprisingly simple molecular structure underlines the potential of fluorescence control by chemical signals for the realisation of useful devices.'

A real device using this idea is some way off; developing a system with more inputs and integrating the organic molecules into solid-state devices remains a challenge. 'The existing examples can hardly compete with the present silicon-based numeric locking and protection process,' Das explains, 'but these reported examples are a good demonstration of the concept as a proof-of-principle.'

Edward Morgan