Correlating vapour uptake with the luminescence quenching of poly(dendrimer)s for the detection of nitro group-containing explosives

Abstract

Thin films of two poly(dendrimer)s were studied for the detection of trace quantities of nitro-based taggants and explosives. The poly(dendrimer) structures consist of side chain-conjugated triphenylamine-based dendritic chromophores attached to a non-conjugated polymer backbone. The poly(dendrimer)s differ in terms of the conjugation length, steric bulk and surface groups of the chromophores and we investigated the effects of these differences on sensing performance. We found that the addition of first-generation biphenyl-based dendrons to the chromophores of one of the polymers, P2, resulted in greater photoluminescence quenching, sensitivity and recovery to pulses of the vapours of the nitroaliphatic taggant 2,3-dimethyl-2,3-dinitrobutane (DMNB) and the nitroaromatic analyte 2,4-dinitrotoluene (2,4-DNT) compared with the other polymer, P1. We employed neutron reflectometry to characterise the vapour uptake of both poly(dendrimer)s and a structurally similar triphenylamine-based dendrimer D1 for comparison. The results show that the P2 has a mass density of 0.91 ± 0.01 v. 1.01 ± 0.01 g cm−3 for both P1 and D1 and can absorb at least twice the amount of 2,4-DNT. These results show how increasing the dendritic character of the poly(dendrimer) architecture provides a route for optimising vapour uptake and improving sensing performance in the solid state.