The Construction Of Explosive Sensing Systems And Their Applications

As one of the most important chemicals that concerns the homeland security andhumanitarian safety, rapid detection and discrimination of hidden explosives are alwaysthe important aspects in the entire world. However, in recent years, with the increasinglevels of the preparation and hidden strategies, real-time detection of explosives facedmore severe challenges. So in this aspect, establishing and developing new sensingideas and methods for the future needs are always highly needed. In this dissertation,based on the fluorescence analysis, three new systems were developed andfurther employed to study the sensing behaviors in nitrated aromatics andaliphatic nitro-organics explosives. The main research contents and conclusionsare as follows:Toward to the specific recognition problem for nitro-organics explosives,on the basis of the combination of colloidal and mesophase templating, as wellas molecular imprinting, the micro-meso-macro trimodal hybrid silica film withprecise control of pore size and morphology on all three length scales wasdeveloped. The pore system combined the multiple benefits arising from alllength scales and so possessed a series of distinct properties such as high porevolume, large surface area, molecular selectivity, and rapid mass transport. Withthe construction of the functional porous system, highly selective recognition ofaromatic explosive TNT was ultimately achieved. Also, in order to find the bestfabrication condition for explosive sensing, two general physicomathematicalmodels were developed to better understand the diffusion-adsorption ofexplosive molecules in hierarchically porous systems. Based on the simulations,we proved that the pore length and the apparent rate of adsorption were the mostimportant factors to influence the performance of sensor. And also for theporous systems with parallel pores, there indeed existed the optimum region toachieve the best sensitivity and selectivity.To further improve the recognition ability, based on the simple counterionexchange of ionic liquids, a new strategy to create a cross-reactive sensor arraywith dynamic tunable feature was developed. To achieve a good sensing system with good sensitivity, low detection limit, and fast response, the synthesizedionic liquid receptors were tethered onto a silica matrix with amacro-mesoporous hierarchical structure. Through the facile anion exchangeapproach, abundant ionic liquid-based individual receptors were easily andquickly synthesized. Virtually, the unlimited anion exchange ability offered theopportunity to get the receptors with diversiform properties and recognitionability. Moreover, the reversible anion exchange ability further endowed thesensor array with a dynamic tunable feature. With the creation of ionicliquid-based sensor array, the identification and classification of sixnitroaromatics and explosives mimics was finally obtained, and recognitionaccuracy was100%.Finally, toward to the difficult sensing for aliphatic nitro-organicsexplosives, based on the host-guest behavior of cucurbit[8]uril (CB[8]),naphthalene-threaded CB[8] rotaxane structure on solid substrate was developedfor broad-class explosive detection. In the sensing system, since the formationof host stabilized charge transfer complexes, highly sensitive detection ofnitrated aromatics (TNT and DNT) was achieved. Whereas, due to the uniqueconfinement effect and size exclusion of CB[8] nanocavity, the sensor evenshowed differential responses to RDX, HMX and PETN, which made it easy torealize the direct detection and discrimination of the challenging aliphaticnitro-organics explosives. By using only a single sensor, we finally achieved abroad class of explosives detection. These performed experiments suggested thatwe opened a new way to develop a new kind of sensing-protocol that enabled aricher identification of threats.