Detection of nitroaromatic explosives based on fluorescence quenching of silafluorene- and silole-containing polymers: A time-dependent density functional theory study

Poly(silafluorene-phenylenedivinylene)s and poly((tetraphenyl)-silole- phenylenedivinylene)s are promising materials to be used as chemical sensors for explosives detection. The optoelectronic properties of these polymers as well as their constituent units have been investigated by modeling the properties of their excited states. Natural Transition Orbital analysis and topological φ_S descriptor assessment have been used to qualitatively and quantitatively characterize the physical nature of the transitions constituting the absorption spectra. The main transitions observed in all oligomers are associated to be a π-π∗ transition of the bridging moiety. Lower energy transitions of charge transfer character are further considered to understand the fluorescence quenching mechanism upon the complexation of these polymers with the analytes. Indeed the charge-transfer character of the first excited state leads to the emergence of thermal deactivation channels and hence to luminescence quenching.