Luminescent poly(dendrimer)s for the detection of explosives

Abstract

Three poly(dendrimer)s and their corresponding monomers have been studied for the detection of trace quantities of nitro-based explosives. The poly(dendrimer) structures consist of side-chain conjugated triphenylamine-based chromophores attached to a non-conjugated norbornenyl-derived polymer backbone, with the polymers prepared using a ring opening metathesis polymerisation. The conjugation length, steric bulk, and surface groups of the chromophores were varied to explore their effects on sensing performance. Solution-based Stern–Volmer (SV) measurements were conducted on the materials to investigate the quenching responses to the nitro-aliphatic taggant, 2,3-dimethyl-2,3-dinitrobutane (DMNB), and the nitroaromatic analyte, 2,4-dinitrotoluene (DNT). The SV measurements showed a general trend of an increase in the solution quenching response (observed for both analytes) when going from the monomer to the corresponding poly(dendrimer). Furthermore, the poly(dendrimer) that had the smallest and least sterically encumbered chromophore was found to have the largest response to both DNT and DMNB. Combination of time-resolved and steady-state SV measurements revealed that for the poly(dendrimer)s the quenching by DNT was dominated by a dynamic mechanism, whereas for DMNB it was roughly split between instantaneous and dynamic quenching.