The synthesis of tetraarylethylene-based conjugated polymers for the application of fluorescence sensing towards nitroaromatics

Abstract

Using the Suzuki cross-coupling method, the tetraarylethylene-based conjugated polymers PT-F and PT-Cz were synthesized by reacting 9-(dibromomethylene)-9H-thioxanthene with (9,9-dihexyl-9H-fluorene-2,7-diyl)diboronic acid and 9-heptyl-3,6-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole ester, respectively. PT-F and PT-Cz exhibit significant aggregation-induced emission (AIE) properties, with fluorescence quantum yields 184 times and 74 times higher in THF/H₂O (2/8, v/v) than in pure THF, respectively, attributed to the introduction of the tetraarylethylene units. The sensing performance of the polymers towards 2,4,6-trinitrophenol (TNP) was investigated. The quenching constants for the detection of TNP based on PT-F and PT-Cz in THF/H₂O (2/8, v/v) are 1.20 × 10⁵ M⁻¹ and 2.04 × 10⁵ M⁻¹, with detection limits of 0.12 μM and 0.07 μM, respectively. Moreover, PT-F and PT-Cz achieve selective detection and anti-interference detection of TNP against other common nitro-compounds and common ions. Furthermore, the spiking/recovery data show the recovery rates for TNP based on the two polymers in different water samples ranging from 93.20% to 107.80%, and the result is verified by a t-test.