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Detection of Explosive Vapors: The Roles of Exciton and Molecular Diffusion in Real‐Time Sensing
Author(s) -
Ali Mohammad A.,
Shoaee Safa,
Fan Shengqiang,
Burn Paul L.,
Gentle Ian R.,
Meredith Paul,
Shaw Paul E.
Publication year - 2016
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201600767
Subject(s) - analyte , quartz crystal microbalance , diffusion , quenching (fluorescence) , analytical chemistry (journal) , chemistry , fluorescence , explosive material , sorption , fluorophore , nitromethane , chemical physics , materials science , chromatography , thermodynamics , organic chemistry , optics , adsorption , physics
Time‐resolved quartz crystal microbalance with in situ fluorescence measurements are used to monitor the sorption of the nitroaromatic (explosive) vapor, 2,4‐dinitrotoluene (DNT) into a porous pentiptycene‐containing poly(phenyleneethynylene) sensing film. Correlation of the nitroaromatic mass uptake with fluorescence quenching shows that the analyte diffusion follows the Case‐II transport model, a film‐swelling‐limited process, in which a sharp diffusional front propagates at a constant velocity through the film. At a low vapor pressure of DNT of ≈16 ppb, the analyte concentration in the front is sufficiently high to give an average fluorophore–analyte separation of ≈1.5 nm. Hence, a long exciton diffusion length is not required for real‐time sensing in the solid state. Rather the diffusion behavior of the analyte and the strength of the binding interaction between the analyte and the polymer play first‐order roles in the fluorescence quenching process.