A jellyfish is the inspiration for a new range of light-emitting diodes (LEDs). A group of US electrical engineers report in Advanced Materials1 that they have used a fluorescent protein found in jellyfish to synthesize materials that emit light when electricity flows through them. These LEDs may ultimately lead to better full-colour flat-screen displays for portable computers.

A substance called green fluorescent protein, or GFP, makes the Pacific Ocean jellyfish Aequorea victoria glow green. GFP collects the energy produced in a cellular chemical reaction and emits it as green light from a small molecular unit called a 'chromophore' in its long molecular chain.

GFP has long been used as a marker by biologists. Now scientists making light-emitting devices have become attracted to the efficiency and the highly specific colour of the chromophore's emission process.

Mark Thompson of the University of Southern California in Los Angeles and co-workers have created a variety of fluorescent molecules that mimic the chromophore -- but without the surrounding protein scaffolding which would stymie an electrically controlled device.

The researchers are optimistic about the prospects for this approach. "There are an enormous variety of fluorescent organisms," they say. "Other materials can be prepared, using the insight provided by [these] naturally occurring systems, which may be useful in electronic and optoelectronic applications."

Most commercial LEDs are made from crystalline semiconductors, such as gallium arsenide or indium phosphide, which glow when electricity flows through them. But there is increasing interest in making LEDs from organic (carbon-based) substances instead, as they would be easier and cheaper to manufacture.

So far, organic LEDs (OLEDs) have been made from electricity-conducting polymers that emit light, as well as from certain small organic molecules such as aluminium tris(8-hydroxyquinoline), or Alq3.

Thomson's team scattered their chromophore-like molecules through a matrix of Alq3 in an OLED. The idea was that these 'dopants' would capture energy from the matrix and convert it to light emission, determining the colour and efficiency of the device.

By tinkering with the molecular structures, Thompson and his colleagues fashioned green and orange chromophore OLEDs. These are not yet as efficient as existing devices, but the first prototypes in this field are usually improved by further work.