Oligotriphenylene nanofiber sensors for detection of nitro-based explosives

Abstract

Blue light-emitting oligotriphenylene nanofibers are synthesized by oxidizing triphenylene using ferric chloride. By adjusting the monomer concentration, the acid used, and the temperature employed, the average diameter and length of the nanofibers can be readily tuned from 50 to 200 nm and 0.5 to 5 μm, respectively. Structural characterization, electrical conductivity, thermal stability, and fluorescence of oligotriphenylene, along with a proposed nanofiber formation mechanism, are presented. Both oligotriphenylene nanofiber dispersions and oligotriphenylene/polysulfone composite films are developed as fluorescent sensors for detecting traces of nitro-based explosives including nitromethane, nitrobenzene, and 2,4,6-trinitrophenol, as well as an electron-deficient metal ion, Fe(III). The sensors exhibit much better selectivity and sensitivity compared to conventional sensors, with detection limits down to 1.0 nm with a detection range covering ∼4 orders of magnitude. The detection mechanism of the fluorescent sensors is also disscussed. Blue light-emitting oligotriphenylene nanofiber molecular wires exhibit high thermal stability, high fluorescence quantum yield, enhanced conductivity, and stable fluorescence, when compared to the monomer. Fluorescent sensors based on oligotriphenylene nanofibers and their polysulfone composite films enable trace detection, high sensitivity, and high selectivity of nitro-based explosives including nitromethane, nitrobenzene, and 2,4,6-trinitrophenol as well as Fe(III) owing to formation of stable π-electron/charge transfer complexes between the fluorophores and the analytes. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.