Detection of Explosive Vapors: The Roles of Exciton and Molecular Diffusion in Real‐Time Sensing. Issue 21 (1st September 2016)

• Record Type: Journal Article
• Authors: Ali, Mohammad A.; Shoaee, Safa; Fan, Shengqiang; Burn, Paul L.; Gentle, Ian R.; Meredith, Paul; Shaw, Paul E.
• Is Part Of: Chemphyschem. Volume 17:Issue 21(2016)
• Page Start: 3350
• Page End: 3353
• Publication Date: 2016-09-01
• Subjects: conjugated polymers -- explosives -- fluorescence -- sensors -- time-resolved spectroscopy; Chemistry, Physical and theoretical -- Periodicals; 541.05
• DOI: 10.1002/cphc.201600767
• Languages: English
• ISSNs: 1439-4235

Abstract

Abstract: 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. Abstract : Resolving the diffusion confusion : By correlating the uptake of nitroaromatic (explosive) vapor by a porous conjugated polymer film with the quenching of the fluorescence the origins of the high sensitivity of this material are probed. It is found that even at low vapor pressures, the nitroaromatic diffuses into the film as a high concentration front with average chromophore–analyte separation of ≈1.5 nm. The implications for sensing materials design strategies are discussed.