Chromo-fluorogenic detection of nitroaromatic explosives by using silica mesoporous supports gated with tetrathiafulvalene derivatives

Abstract

Three new hybrid gated mesoporous materials (SN3 -1, SNH2 -2, and SN3 -3) loaded with the dye [Ru(bipy)3 ](2+) (bipy=bipyridine) and capped with different tetrathiafulvalene (TTF) derivatives (having different sizes and shapes and incorporating different numbers of sulfur atoms) have been prepared. The materials SN3 -1 and SN3 -3 are functionalized on their external surfaces with the TTF derivatives 1 and 3, respectively, which were attached by employing the "click" chemistry reaction, whereas SNH2 -2 incorporates the TTF derivative 2, which was anchored to the solid through an amidation reaction. The final gated materials have been characterized by standard techniques. Suspensions of these solids in acetonitrile showed "zero release", most likely because of the formation of dense TTF networks around the pore outlets. The release of the entrapped [Ru(bipy)3 ](2+) dye from SN3 -1, SNH2 -2, and SN3 -3 was studied in the presence of selected explosives (Tetryl, TNT, TNB, DNT, RDX, PETN, PA, and TATP). SNH2 -2 showed a fairly selective response to Tetryl, whereas for SN3 -1 and SN3 -3 dye release was found to occur with Tetryl, TNT, and TNB. The uncapping process in the three materials can be ascribed to the formation of charge-transfer complexes between the electron-donating TTF units and the electron-accepting nitroaromatic explosives. Finally, solids SNH2 -2 and SN3 -1 have been tested for Tetryl detection in soil with good results, pointing toward a possible use of these or similar hybrid capped materials as probes for the selective chromo-fluorogenic detection of nitroaromatic explosives.

Keywords: gated materials; mesoporous materials; nitroaromatic explosives; optical detection; sensors; tetrathiafulvalene.