New materials to detect radiation may lead to a handheld device for detecting nuclear weapons or materials such as a "bomb in a suitcase," U.S. researchers say.

"The terrorist attacks of 9/11 heightened interest in this area of security, but the problem remains a real challenge," Northwestern University chemistry Professor Mercouri G. Kanatzidis said in a release issued by the school Monday.

"We have designed promising semiconductor materials that, once optimized, could be a fast, effective and inexpensive method for detecting dangerous materials such as plutonium and uranium."

The researchers developed new semiconductor materials from heavy elements that, when struck by gamma rays from a suspect material, emit electrons.

Because every element has a particular spectrum, the signal of the detected electron emissions identifies the suspect material.

One hurdle for the researchers is that most heavy metals have a lot of mobile electrons, so electrons excited by gamma radiation are hard to detect.

"It's like having a bucket of water and adding one drop -- the change is negligible," Kanatzidis explained. "We needed a heavy element material without a lot of electrons. This doesn't exist naturally so we had to design a new material."

They developed two new semiconductor materials, cesium-mercury-sulfide and cesium-mercury-selenide.

"Our materials are very promising and competitive," Kanatzidis said. "With further development, they should outperform existing hard radiation detector materials."