Fluorescent Nanofilms for Nitroaromatic Explosives Detection-Promises and Challenges

Abstract

EditorialFast and sensitive detection of nitro-aromatic explosives is of vital importance for finding hidden explosives in airport luggage or mails, screening of personnel, and detection of buried landmines [1][2][3]. A crucial example is the detection of trace amount of 2,4,6-trinitrotoluene (TNT), which is a typical nitro-aromatic explosives [4][5][6][7][8]. Various TNT detection methods are currently available, such as, the fluorescence quenching method, micromechanical sensors based on micro cantilever, the electrochemical method, ion mobility s pectroscopy (IMS), the surface-enhanced Raman spectroscopy ( SERS) and semiconductor based gas sensors [7,[9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Among t he above-mentioned methods used for TNT detection, the fluorescence quenching method is considered to be the most effective tool for sensing nitro-aromatic explosives in recent years owing to its high sensitivity, convenience, easy visualization, and short response t ime for detection [24].Much attention has been paid to the development of novel fluorescence materials for explosives detection [2,7,15,25]. Metal organic frameworks (MOFs), fluorescent conjugated polymer, and fluorescent fibers are three typical detecting materials based on fluorescence quenching method [2,11,[26][27][28]. For MOFs, detectable changes in luminescence along with tailorable porosity and a high surface area make MOFs excellent candidates for detecting TNT [2]. Fluorescent conjugated polymers have an advantage over small fluorescent molecules in excition migration along the polymer chains, which could amplify signal like "molecular wire" [26][27][28]. This advantage leads to the rapid development of fluorescent conjugated polymers in explosives sensing. From 1995From -2007, Swagers' group continuously demonstrated the amplification possibility with molecular wires for chemical sensors [29][30][31][32][33][34]. Based on their work, commercialized product (Fido NXT) which can detect TNT at part per quadrillion (ppq) levels has been applied in war zones of Afghanistan and Iraq [35]. In China, based on fluorescent conjugated polymers, Cheng and co-workers also explored trace explosives detector (SIM series) which could detect explosives, such as nitro-aromatic explosives and plastic explosives at part per trillion (ppt) levels in 2007 [36]. Although significant advances have been achieved, the sensing performance of fluorescent conjugated polymers depends highly on the film thickness due to the slow diffusion of analyte vapors in the non-porous rigid conjugated polymer films [30,37]. And the synthesis process of conjugated polymers is complex [38].In this regard, electrospinning technology which is a simple and cost-effective approach to prepare nanofibrous films has been developed very rapidly in recent years [37]. Guangtao Li pioneered electrospun fibrous membranes for TNT detection, and the quenching efficiency was comparable to that of conjugated polymer-based TNT sensors [11]. Feng Liu fabricated a novel electrospun ...