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Sensors 2017, 17(11), 2532; doi:10.3390/s17112532

Towards the Development of a Low-Cost Device for the Detection of Explosives Vapors by Fluorescence Quenching of Conjugated Polymers in Solid Matrices

1
Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
2
Centro de Química-Física Molecular (CQFM) and the Institute of Nanoscience and Nanotechnology (IN), Instituto Superior Técnico, University of Lisbon, 1049-001 Lisbon, Portugal
3
Institute of Systems and Robotics (ISR), University of Coimbra, 3030-290 Coimbra, Portugal
4
Instituto de Telecomunicações, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
*
Author to whom correspondence should be addressed.
Received: 28 September 2017 / Revised: 25 October 2017 / Accepted: 30 October 2017 / Published: 3 November 2017
(This article belongs to the Special Issue Fluorescent Probes and Sensors)
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Abstract

Conjugated polymers (CPs) have proved to be promising chemosensory materials for detecting nitroaromatic explosives vapors, as they quickly convert a chemical interaction into an easily-measured high-sensitivity optical output. The nitroaromatic analytes are strongly electron-deficient, whereas the conjugated polymer sensing materials are electron-rich. As a result, the photoexcitation of the CP is followed by electron transfer to the nitroaromatic analyte, resulting in a quenching of the light-emission from the conjugated polymer. The best CP in our studies was found to be poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-bithiophene] (F8T2). It is photostable, has a good absorption between 400 and 450 nm, and a strong and structured fluorescence around 550 nm. Our studies indicate up to 96% quenching of light-emission, accompanied by a marked decrease in the fluorescence lifetime, upon exposure of the films of F8T2 in ethyl cellulose to nitrobenzene (NB) and 1,3-dinitrobenzene (DNB) vapors at room temperature. The effects of the polymeric matrix, plasticizer, and temperature have been studied, and the morphology of films determined by scanning electron microscopy (SEM) and confocal fluorescence microscopy. We have used ink jet printing to produce sensor films containing both sensor element and a fluorescence reference. In addition, a high dynamic range, intensity-based fluorometer, using a laser diode and a filtered photodiode was developed for use with this system. View Full-Text
Keywords: conjugated polymers; explosives detection; trace analysis; optical sensor; luminescence sensor conjugated polymers; explosives detection; trace analysis; optical sensor; luminescence sensor
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Martelo, L.M.; das Neves, T.F.P.; Figueiredo, J.; Marques, L.; Fedorov, A.; Charas, A.; Berberan-Santos, M.N.; Burrows, H.D. Towards the Development of a Low-Cost Device for the Detection of Explosives Vapors by Fluorescence Quenching of Conjugated Polymers in Solid Matrices. Sensors 2017, 17, 2532.

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