Comparing conjugated polymer thin film and electrospun nanofiber sensing elements for detection of explosives.

We report sensitive detection of explosive materials via fluorescence quenching mechanism of a conjugated polymer Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(bithiophene)]. The polymer used in this investigation is highly fluorescent and can be easily processed into thin films or nanostructured fibers. We have shown that a thin film of the polymer can detect TNT and DNT easily at ambient condition and in vapor phase. The detection limit for TNT is less than 5 parts per billion (ppt) at 25 degrees C and ambient conditions. Additionally, we have also carried out a comparative study to investigate the role of nanostructures on sensitivity. Towards this, a sensing element of fluorescent nanofibers was fabricated using electrospinning and quenching efficiency was tested. In general, nanostructure improves sensitivity by enhancing the surface area but in case of conjugated polymer we noticed that it did not add much value as far sensitivity is concern.