Discriminative Detection of Aliphatic, Electron-Rich and Electron-Deficient Aromatic Volatile Organic Contaminants Using Conjugated Polymeric Fluorescent Nanoaggregates with Aggregation Induced Emission Characteristics

Abstract

Discrimination of aromatic, aliphatic volatile organic compounds (VOCs) with high sensitivity and easy operational techniques is important due to related environmental implications. Herein the development of fluorescent conjugated polymers is reported, consisting of donor–acceptor pairs and their nanoaggregates as fluorophores with differential emission behavior in the presence of aromatic, aliphatic VOCs and electron-deficient VOCs both in aqueous solution and solid state. The polymeric network consists of fluorene moiety with dangling alkyl groups as donors and aggregation-induced emission (AIE) active tetraphenylethylene (TPE) unit as an acceptor. The corresponding fluorescent nanoaggregates exhibit enhancement in the emission intensity owing to restriction in intramolecular motion of AIE unit in the presence of aliphatic VOCs, whereas the fluorescence enhancement is accompanied by a bathochromic shift in emission maxima in the case of aromatic VOCs owing to the conformational change in the phenyl rings of TPE unit. On the other hand, the fluorescence of nanoaggregates quenches in the presence of an electron-deficient VOC through a possible nonradiative electron transfer. Detailed mechanistic studies are corroborated through a variety of spectroscopic, density functional theory calculations, and theoretical simulations. The discriminatory response of the polymeric nanoaggregates toward a different kind of VOCs can also be observed visually in the thin-film state. © 2022 Wiley-VCH GmbH