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New material lights up when detecting explosives

05 February 2016

University of Southern Denmark scientists have created a material which becomes fluorescent if there are molecules from explosives in the vicinity.

Steffen Bähring got interested in detection of explosives when he was in Afghanistan in 2005 with the Danish International Brigade. Bähring is seen here next to a car damaged by a roadside bomb

The discovery could improve airport security as well as providing an insight into a rather chaotic micro-world where molecules and atoms are constantly responding to their surroundings.

The new material consists of a set of molecules which react when encountering explosives molecules in their vicinity - TTF-C[4]P and TNDCF. TNDCF has the special property that it becomes fluorescent when an explosives molecule is introduced to the set of molecules.

"This new knowledge could lead to creating a small device based on this set of molecules," says Steffen Bähring, first author of a paper describing the work in the journal, Chemistry - a European Journal. "With such a device security staff in airports could test if there are explosives molecules on or near a bag."

This is not the first time scientists report the development of chemical substances capable of detecting explosives. But previously many uncertainties have been involved, and therefore the methods have not been entirely reliable.

One problem is that previous techniques have been based on a substance that became fluorescent when there were no explosives molecules in the vicinity and that the fluorescence disappeared if the substance came into contact with explosive molecules.

"The problem was that several factors could make the fluorescence disappear; a number of salts for example had this effect. Thus these substances could give off a false alarm,” says Bähring.

The new material only turns fluorescent when exposed to molecules form the explosive TNB and some specific salts, such as those based on chlorine or fluorine.

"There can only be two reasons why it turns fluorescent, one of them being the presence of explosives. Thus this material is a highly reliable tool for detecting explosives," says Bähring.

His new material consists of molecules held together by weak bonds. Weakly bonded molecules form substances that can easily switch form – just like water can be found in both liquid, solid or gaseous form - and compared to strongly bonded molecules they are very easily influenced by their surroundings.

Weakly bonded molecules constantly respond to their environment, such as changes in temperature. This makes them very difficult to control. It also makes them extra difficult to work with, and creating new molecular architectures based on them is no easy task.

"It is extremely hard to create a chain of different weakly bonded molecules. If a scientist one day succeeds in putting just ten different types of molecules together in this way, it would be a great achievement”, says Bähring.

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