Most current methods for detecting explosives require physical collection of explosive particles, which isn’t ideal for real-world applications. As a result, research into devices that can ‘sniff out’ a wide range of explosives by sampling the air is a hot area. One team based in Israel, headed up by Fernando Patolsky, has developed a detector based on chemically-modified nanodevices that exhibits sensitivity up to four orders of magnitude higher than commonly-used ion mobility spectroscopy (1). The portable platform can apparently detect explosives down to the parts per quadrillion level, including triacetone triperoxide (TATP), which is often used by suicide bombers.
The team created a multiarray of 144 silicon nanowire field effect transistors (FETs) split into eight subarrays. Each subarray comprises 18 FET nanodevices modified with a surface-binding agent. The subarrays are fed by a common integrated microfluidic channel that enables the flow and interaction of all analytes. “Our nanoarray chip allows for the differential yet simultaneous chemical modification of all eight subarrays with multiple surface binding agents,” Patolsky explains. “Each explosive species is expected to exhibit a distinctive pattern of interaction, both kinetically and thermodynamically, with the chemically-modified FETs.”
“Several improvised explosives display a relatively high volatility and can be found in the air at high concentrations,” says Patolsky, “but other explosives such as RDX (C4) and pentaerythritol tetranitrate (PETN) exhibit low volatility and cannot be directly detected by current methods, or even by trained dogs, in air samples. This forces the physical collection of particulates – clearly a huge limitation.” By identifying parameters to mathematically differentiate the responses of different explosives and other non-explosive materials – a process Patolsky describes as a ‘fingerprinting’ – the new platform is apparently sensitive enough to pick out explosives even in heavily contaminated conditions. There are other potential security applications for the device too, including the detection of bio-threats and toxins. It could also be used to sniff out narcotics or to monitor the environment. But for now, the team will be focusing on field testing the prototype and expanding the detectable explosives library. “We believe the platform will be readily able to detect the most miniscule traces of explosives present in the air around the source without requiring physical contact. It will be relevant in many real-life scenarios,” says Patolsky.
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References
- Lichtenstein et al., “Supersensitive fingerprinting of explosives by chemically modified nanosensors arrays,” Nature Communications DOI: 10.1038/ncomms5195 (2014).