Abstract
Detection of nitroaromatic explosives with high sensitivity and selectivity is extremely important for civilian and military safety. Here, we report the synthesis and multimodal sensing applications of an emissive alanine based dansyl tagged copolymer P(MMA-co-Dansyl-Ala-HEMA) (DCP), synthesized by RAFT copolymerization. The fluorescent co-polymer exhibited high sensitivity and selectivity towards conventional nitroaromatic explosives such as DNT, TNT and TNP in solution at lower range of µM level and also with saturated vapor of NACs. The quantum yield of the co-polymer was measured to be very high (Φf = 77%) which make it an ideal candidate for sensing in solution as well as in vapor phase. The fluorescence signal from DCP copolymer gets significantly quenched upon addition of aliquots of DNT, TNT, and TNP. The Stern-Volmer constant was calculated to be very high. The quenching mechanism was further established by fluorescence up-conversion, time-resolved fluorescence and steady state absorption spectroscopy. The energetics of sensing process was calculated by Density Functional Theory (DFT) studies. We also fabricate a thin film polymer sensor which was able to detect nitroaromatic vapors with high selectivity. This opens up the possibility of building a low-cost and light-weight nitroaromatic explosives sensor for field use.
Highlights
The conventional explosives detection methods mainly rely on canines or sophisticated instruments such as gas chromatography (GC)[4], ion mobility spectrometry (IMS)[5], Raman or surface enhanced Raman scattering[6,7], high performance liquid chromatography (HPLC)[8], surface Plasmon resonance[9], and cyclic voltammetry[10]
Numerous fluorescent probes including small molecule, nanoparticles, nano-fibers, Molecular Imprinted Polymer (MIP), Polymeric composites, Metal-Organic Framework (MOF) and fluorescent co-polymers have been developed for the rapid detection of trace amounts of nitroaromatic (NACs) by fluorescence quenching methods[13,14,15,16,17,18,19]
From the GPC study, number average molecular weight (Mn,GPC) and Ð values were obtained for the copolymers and results are shown Table 1, which shows that theoretical molecular weights (Mn,theo = (([Monomer]/ [Cyano(dodecylsulfanylthiocarbonyl)sulfanylpentanoic acid (CDP)] × average molecular weight (MW) of monomer × Conv.) + (MW of CDP)) predicted from stoichiometry and monomer conversion matches well with the Mn,GPC values
Summary
Vishal Kumar 1, Binoy Maiti[2], Mrinmoy Kumar Chini[1], Priyadarsi De2 & Soumitra Satapathi[1]. The fluorescent co-polymer exhibited high sensitivity and selectivity towards conventional nitroaromatic explosives such as DNT, TNT and TNP in solution at lower range of μM level and with saturated vapor of NACs. The quantum yield of the co-polymer was measured to be very high (Φf = 77%) which make it an ideal candidate for sensing in solution as well as in vapor phase. The fluorescent co-polymer exhibited high sensitivity and selectivity towards conventional nitroaromatic explosives such as DNT, TNT and TNP in solution at lower range of μM level and with saturated vapour of NACs. The quantum yield of the co-polymer was measured to be very high (Φf = 77%) which make it an ideal candidate for sensing in solution as well as in vapor phase. The selectivity of DCP towards NACs has been tested with various analogues analytes
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