22 April 2006 Detection of nitro-aromatic compounds by optical gas sensors based on sensitive or photoluminescent polymers
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In the first part of this paper, we use a specially developed sensitive polymer (PLG) which belongs to the polysiloxane family. Thin layers of this polymer are deposited onto the surface of the optical transducers. Results will be presented on the response of diffraction-based optical transducers such as gratings and also on interferometric transducers and especially integrated Mach-Zehnder (MZ) interferometers. In the first case, a relief grating is coated with the sensitive polymer. A small variation of the refractive index of this layer, due to the presence of pollutant, induces a variation of the intensity of the diffracted orders which can be measured. In the second case, one arm of the integrated MZ interferometers is coated with the polymer. The variation of the refractive index of the polymer causes a phase shift in the measuring arm which can be measured by the modification of the output intensity. Assessment of sensitivity for the detection of nitro-aromatic compounds using a PLG sensitive layer on both sensors are presented and are also compared to the response of a SAW-based sensor coated with the same polymer. In the second part of this paper, synthesis, spectroscopy and fluorescence quenching behaviour of a N-(2,5-ditertio-butylphenyl)-1,8-naphthalimide functionalised polystyrene (PST-NI) are reported. PST-NI was synthesized by free radical polymerisation of the corresponding monomer. The molecular weight (Mn) is 43 000 g.mol-1. Introduction of a bulky moiety on the naphthalimide chromophores avoids P-stacking of the polymer side chains as well as excimer formation and hence leads to very high fluorescence quantum yields in thin solid films (up to 60%). Upon 1 minute exposure to DNT vapour, it was shown that a 5.5 nm thick film of PST-NI exhibits a 45% drop in its fluorescence intensity, which makes this polymer very attractive for sensing applications.
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T. Lamarque, T. Lamarque, P. Le Barny, P. Le Barny, E. Obert, E. Obert, E. Chastaing, E. Chastaing, B. Loiseaux, B. Loiseaux, I. Leray, I. Leray, } "Detection of nitro-aromatic compounds by optical gas sensors based on sensitive or photoluminescent polymers", Proc. SPIE 6189, Optical Sensing II, 61890V (22 April 2006); doi: 10.1117/12.664032; https://doi.org/10.1117/12.664032

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