Abstract
Explosive detection has become an increased priority in recent years for homeland security and counter-terrorism applications. Although drones may not be able to pinpoint the exact location of the landmines and explosives, the identification of the explosive vapor present in the surrounding air provides significant information and comfort to the personnel and explosives removal equipment operators. Several optical methods, such as the luminescence quenching of fluorescent polymers, have been used for explosive detection. In order to utilize sensing technique via unmanned vehicles or drones, it is very important to study how the air flow affects the luminescence quenching. We investigated the effects of air flow on the quenching efficiency of Poly(2,5-di(2′-ethylhexyl)-1,4-ethynylene) (PEE) by TNT molecules. We treated the TNT molecules incorporated into the polymer film as non-radiative recombination centers, and found that the time derivative of the non-radiative recombination rates was greater with faster air flows. Our investigations show that relatively high air flow into an optical sensing part is crucial to achieving fast PL quenching. We also found that a “continuous light excitation” condition during the exposure of TNT vapor greatly influences the PL quenching.
Highlights
Detecting the presence of explosives in the surrounding environment, whether in the battle field or in the fight against terrorism, is critical to saving lives and property
The electronic delocalization of conjugated polymers was discussed earlier [29,30,31], and HOMO LUMO levels were calculated by Density Functional Theory (DFT) simulations for some conjugated polymers [32,33]
It has been reported that the PL quenching of conjugated polymer by nitro-based explosives is mainly due to the photo-electron transfer, whereby the photoexcited electrons in the LUMO states transfer to the lower-lying energy levels of the analyte molecules [5,9,13,15,31]
Summary
Detecting the presence of explosives in the surrounding environment, whether in the battle field or in the fight against terrorism, is (increasingly) critical to saving lives and property. Many present and past conflict zones are still littered with millions of landmines, continuing to bring havoc to the local populations, as well as preventing the further advancement of these mostly underdeveloped regions and nations [5,6]. Homeland security and border control spend an enormous amount on explosive material screening and detection [7], bringing various levels of discomfiture to passing passengers or travelers. The basic science and technologies used to enable such detection have been known for a few decades, with researchers seeking effective non-contact detection devices. The meaningful application of such technologies in widely available devices remains a very elusive task
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