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A low-cost laser which can detect hidden explosives and could lead to improved airport security has been developed in Fife.

St Andrews University physicists have made a laser which can trace vapours emitted by explosives such as TNT.

The scientists said the device could work like "an artificial nose for a robot dog", sniffing out extremely low concentrations of vapour.

The technology may also help detect landmines and roadside bombs.

Dr Graham Turnbull, of the research team, said: "Floating above a landmine in Iraq or Afghanistan, there's a very weak, dilute cloud of vapours of explosive molecules that the bomb is made from.

"We have shown that our lasers can rapidly sense these TNT-like molecules, frequently used in explosives, at extremely low concentrations."

The team hopes the laser could be built into a remote-controlled robotic device which could be despatched into a mine field, looking for vapour clouds.

Using a thin film of polyfluorene, a light-emitting plastic, they have created a laser which reacts with explosive vapour.

The laser light dims within seconds when the plastic comes into contact with even the tiniest emission of vapour.

The laser sensor can be reset by a blast of nitrogen gas.

An advantage over existing methods is that the new technology is "relatively low-cost" because the polyfluorene is widely used in plastic electronics.

Dr Turnbull added: "On a dusty road in Afghanistan there are relatively few things that might affect the laser output and it certainly could have potential in that area.

"Essentially it's making an artificial nose for a robot sniffer dog."

The research is published by the journal, Advanced Functional Materials.