Fluorescence Quenching Sensor Arrays for the Discrimination of Nitroaromatic Vapors

Fluorescence Quenching Sensor Arrays for the Discrimination of Nitroaromatic Vapors

Nico Bolse (Karlsruhe Institute of Technology (KIT), Germany), Anne Habermehl (Karlsruhe Institute of Technology (KIT), Germany), Carsten Eschenbaum (Karlsruhe Institute of Technology (KIT), Germany) and Uli Lemmer (Karlsruhe Institute of Technology (KIT), Germany)
Copyright: © 2018 |Pages: 36
DOI: 10.4018/978-1-5225-3862-2.ch004

Abstract

Fluorescence quenching is a promising technique for chemical sensing applications such as the detection of explosive trace vapors. Nitroaromatic explosives are one of the primary targets for this approach enabling ultra-low detection limits down to sub parts-per-billion in air. Many studies, however, focus on enhanced sensor sensitivity, whereas practical applications often require the identification and quantification of detected species. Electronic noses and efficient sensor systems are a promising solution to address this challenge. The authors review recent approaches and trends for explosive trace vapor detection and discuss theoretical concepts for fluorescence quenching as well as target analytes, sensor materials, and fabrication techniques. Statistical learning techniques such as principal component analysis and linear discriminant analysis, sensor systems, and camera-based read-out strategies are in the focus of the chapter. The authors conclude with recommendations and solutions for the elaborated challenges and with visions on future research directions.
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Introduction

The detection of trace vapors, especially those emitted from explosives, bombs and dynamites (EBDs) has become more and more important. Recent data from the National Consortium of the Study of Terrorism and Responses to Terrorism (2016) provide evidence that the worldwide number of terrorist attacks and those utilizing EBDs significantly increased as shown in Figure 1. According to a report from the Institute for Economics and Peace (2016), this rise is mainly related to increasing religious extremism, but also due to nationalism, separatism and politics. The report indicates that the increased extremism might be a direct result of the Syrian war starting in 2011 and of ISIS declaring caliphate in 2014. It is stated that private citizens and properties are targeted by most of the attacks which increased the number of deaths from terrorism from about 2.000 in the year 2000 up to more than 12.000 in the year 2015. Furthermore, the decline between 2014 and 2015 of roughly 10% is attributed to military actions and interventions in Iraq and Nigeria, even though both of which were among the countries with the highest number of deaths from terrorism in 2014 and 2015 as is explained in the report.

Figure 1.

Worldwide number of terrorist attacks and those utilizing EBDs

Data retrieved from the National Consortium for the Study of Terrorism and Responses to Terrorism (2016). Used with permission.

These trends demonstrate the urgent need for reliable explosives detection. However, the identification and quantification of detected targets remains challenging. Sniffer dogs, for example, can be trained to be highly sensitive on the one hand. On the other hand, their effectiveness critically depends on their constitution requiring frequent rests. Moreover, each dog needs a trainer and a handler resulting in a rather expensive approach. Other well-established detection approaches such as ion mobility spectrometers (IMS) are complex and expensive, too. Furthermore, IMS typically requires a radioactive ionization source which can cause regulatory difficulties. Therefore, active research is carried out on alternative technologies, each having its own advantages and drawbacks. A non-exhaustive comparison of various state-of-the-art technologies for explosive trace vapor sensing is given in Table 1.

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