Ability of various materials to detect explosive vapors by fluorescent technologies: A comparative study $ Myriam Bouhadid a , Thomas Caron a,b , Florian Veignal a , Eric Pasquinet a , Ame ´ de ´ e Ratsimihety b , Franc - ois Ganachaud b , Pierre Montme ´ at a,n a CEA-DAM Le Ripault, BP 16, F-37260 MONTS, France b Ecole de Chimie, rue de l’Ecole Normale, F-34000 Montpellier, France article info Article history: Received 30 January 2012 Received in revised form 12 June 2012 Accepted 15 June 2012 Available online 14 July 2012 Keywords: Detection Explosives Fluorescent material Chemical sensors abstract For the development of fluorescent sensors, one of the key points is choosing the sensitive material. In this article, we aim at evaluating, under strictly identical experimental conditions, the performance of three materials for the detection of dinitrotoluene (a volatile marker of trinitrotoluene) through different parameters: response time, fluorescence intensity, sensitivity, reversibility, reaction after successive exposures and long-term stability. The results are discussed according to the nature of the sensitive materials. This first study rendered it possible to select a conjugated molecule as the best sensitive material for the development of a lab-made prototype. In a second part, the selectivity of this particular sensitive material was studied and its ability to detect TNT could be demonstrated. & 2012 Published by Elsevier B.V. 1. Introduction The increased use of explosives in terrorist activities has created a demand for a continued innovation in the detection of these agents. To this aim, the detection of nitroaromatic com- pounds (NAC) using chemical sensors has been the major goal of our team for almost a decade. Fluorescent sensors especially seem to satisfy requirements in terms of reliability, cost and handling ability. In this field, an optical device based on the capability of various materials to detect explosive vapors, particularly nitroaromatic compounds such as trinitrotoluene TNT and dini- trotoluene DNT, has been developed [1]. TNT is one of the most commonly used explosives for military applications and DNT is a significant part in the chemical signature of this target compound [2]. The design of a sensor requires several steps. One of the key points is the choice of the sensitive material. According to the literature, various materials [3–17] have been used for the detection of nitroaromatic compounds (NACs) but very few comparisons of data between different families have been published. Our work has focused on the comparison of the responses of three distinctly different organic compounds for the fluorescence detection of nitroaromatic explosives, i.e. a p-conjugated phenylene–ethynylene diimine, a conjugated polymer (polypentiptycene) and a polycarbo- silane functionalized with fluorescent pyrene groups. The first two sensitive layers have been reported to detect nitroaromatic explo- sives even at low concentrations [4,17–19]. Fluorescent polycarbosi- lane has also been described as an efficient sensitive material [12]. Indeed, their viscoelastic properties and high gas permeability make these silicium-based polymers, among which are silicones, interest- ing candidates for chemical sensors [10,11,13,20]. The objective of this study was to first evaluate, under strictly identical conditions, some performance parameters of the three materials with regard to the detection of DNT (as a volatile marker of TNT) [2]: response time, fluorescence intensity, sensi- tivity, reversibility, and reaction after successive exposures. The results are discussed according to the nature of the sensitive materials. The effect of interfering compounds (acetone, ethanol, hydrogen peroxide, etc.) and the detection of explosive vapors (e.g., TNT) with the sensitive material exhibiting the best global detection performances is also presented. 2. Experimental part 2.1. Materials The selected materials included a p-conjugated phenylene– ethynylene diimine (material 1), polypentiptycene (material 2) and a fluorescent polycarbosilane (material 3) whose chemical Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/talanta Talanta 0039-9140/$ - see front matter & 2012 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.talanta.2012.06.027 $ Memory—These authors want to dedicate this paper to Etienne Kosciusko- Morizet, we hope that it will contribute to help keep the memory of him alive. n Corresponding author. Tel.: þ33 2 47 34 56 79; fax: þ33 2 47 34 51 58. E-mail address: pierre.montmeat@cea.fr (P. Montme ´ at). Talanta 100 (2012) 254–261