Silica anchored fluorescent organosilicon polymers for explosives separation and detection

Abstract

The luminescent organosilicon copolymers poly(silafluorenyldiethynylspirobifluorene) and poly(tetrasilolediethynylspirobifluorene) have been covalently linked to a silica gel thin layer chromatography (TLC) support through the use of a trimethoxysilyl end group. Surface functionalization of silica with the fluorescent sensing polymer allows for more efficient quenching by the analyte, due to the small amount of fluorophore present, thus yielding enhanced detection sensitivity. The attachment of the sensing polymers onto a chromatographic support also allows for simultaneous separation of an explosive mixture, and component identification through the use of multiple sensing polymers. In a 1.0 mm² area solution spotted onto the fluorescent silica plate, detection limits obtained for the explosives TNT (2,4,6-trinitrotoluene), DNT (2,6-dinitrotoluene), PA (picric acid), Tetryl (N-methyl-N,2,4,6-tetranitroaniline), HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), RDX (1,3,5-trinitro-1,3,5-triazacyclohexane), and Cl-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) ranged from 4 to 750 pg mm⁻². Since less than 350 pg of highly fluorescent polymer is required to coat each TLC plate, the relatively small amounts of explosive being detected still represent an excess of quencher over sensing fluorophore.