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Metal oxide semiconductor gas sensors as an electronic nose for the detection of microbial agents

7 March 2012

Emma Newton

For homeland security applications, reliable detection of biological agents in-field and in real time is challenging. The UK government’s CONTEST counter-terrorism strategy states one of its ‘prepare’ objectives as “improve preparedness for the highest impact risks in the National Risk Assessment”, which includes terrorist attacks that makes use of unconventional weapons such as biological materials (Home Office, 2001). A significant issue is the lack of a sensitive and reliable in-field biological agent detection system, posing potentially adverse consequences for national security (Arnon, 2001).

Conventional analytical equipment such as gas chromatography-mass spectrometry can circumvent some limitations experienced with canines (Hoffmann, 1997) but these methods are often time consuming and bench-bound so cannot be used in-field. Electronic noses (e-noses) offer an alternative technology. Solid state metal oxide semiconductor (MOS) gas sensors are one of the most common commercially used chemical sensors in e-noses and are used for a variety of purposes, such as environmental monitoring (Capone, 2003). We propose to develop a MOS gas sensing array for the detection of gases associated with a microbial agent. Such gases are often simple in nature (Scotter, 2005) but compact detection systems are usually outmanoeuvred by bench-top instrumentation in terms of real-time analysis (Scotter, 2006). With the appropriate sensing material, MOS sensors have a fast response with quick recovery times. This alongside their small size, robust nature and inexpensive construction makes them desirable candidates for such an application.