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Adaptive and sensitive fibre-optic fluorimetric transducer for air- and water-borne analytes

Alshammari, Alhulw H., Kirwa, Abraham, Dunbar, Alan, Grell, Martin
Talanta 2019 v.199 pp. 40-45
air, fiber optics, fluorescence, fluorometry, optical fibers, polymers, solvents, spectrometers
A sensitive fibre optic fluorescence intensity meter has been designed and built as a transducer to detect quenching of conjugated polymer fluorescence with minimum adjustment between air- and waterborne analytes. Only generic, commercially available parts including optical fibres, solvents, airbrush, standard optical and electronic parts, and a digital lock-in amplifier have been used, avoiding the need for a fluorescence spectrometer. To test the instrument, optical fibres were sensitised with the generic fluorescent poly(phenylene-vinylene) derivative MDMO-PPV and exposed to a variety of vapour pressures, and concentrations in water, of the nitroaromatic explosive 2,4 dinitrotoluene (DNT). We establish dimensionless Stern-Volmer constants (KSV) and limit-of-detection (LoD) for air- and water-borne DNT as KSV(air) = 1.4 × 107vs. KSV(water) = 5.8 × 106 and LoD(air) = 10.9 ppb and LoD(water) = 56 ppb. These LoDs compare favourably to prior reports. We consider our study of the MDMO-PPV/DNT system as a successful test of our transducer design and recommend its wider use.