A fast, on-site sensor detecting peroxide-based explosives could help avert future acts of terrorism. 

Peroxide-based explosives are popular amongst terrorists as the ingredients used to make them are readily available. The world has witnessed many tragedies as a result of terrorists using peroxide-based explosives, including the July 2005 London bombings that involve triacetone triperoxide (TATP). 

Now Resat Apak and colleagues from Istanbul University, Turkey have designed a colorimetric sensor that can selectively detect the peroxide-based explosives TATP and hexamethylenetetramine (HMTD) and can be used on-site. Other spectroscopic methods for explosive detection employ acid or enzyme digestion of the peroxide explosives before fluorimetric detection of the by-product hydrogen peroxide is carried out. However, these methods are often time consuming and vulnerable to interference from other strong oxidising agents and need to be carried out in a laboratory. 

In Apak's sensor, the sample is acid hydrolysed and passed over a Nafion membrane containing a copper-neocuproine complex that turns yellow in the presence of trace amounts of TATP or HMTD. The sensor would be ideal for post-blast analysis and identifying unknown materials or suspect packages confiscated by the police, says Apak. It is cheap to make, easy to use and suffers no interference from other contaminants, such as nitro-explosives (TNT) or washing detergents. 

'The present technique can provide fast on-site inspection of TATP and HMTD explosives, which can be beneficial for giving quick-response against terrorist actions,' comments Nadir Serin, chief research engineer at the Scientific and Technical Research Council of Turkey. 

In future, a hand-held version of this device could see this sensor being used to check surfaces or airborne samples in airports, government buildings and other places at risk of being targeted by terrorists, says Apak. 'Since TATP is essentially a kind of explosive used in terrorist attacks it is expected to be used by police criminological laboratories for on-site screening purposes where fast decision-making is of critical importance,' he adds. 

Emma Shiells 

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