Imidazole-based AIEgens for highly sensitive and selective detection of picric acid

Abstract

Imidazole is an important heterocyclic motif and its derivatives are widely used in many fields such as catalysis, medicine, and smart sensors. Here we report the synthesis of four imidazole derivatives (M1, M2, M3, and M4) with different fused aromatics as fluorescent sensors for picric acid (PA) detection. The four compounds with modifications of triphenylamine or tetraphenylethylene at the N₁ and C₂ positions of the imidazole ring exhibit typical aggregation-induced emission (AIE) properties. The single crystallography results indicate that the bright luminescence is ascribed to the rigidified molecular conformation by multiple weak interactions. As PA probes, M1–M4 show high selectivity and sensitivity in the tetrahydrofuran/water mixture (f_w = 99%). The detection limits are as low as 10⁻⁹ M. Mechanism study suggests that photoinduced electron transfer (PET) is responsible for PA detection. These AIE-active imidazole derivatives have been demonstrated to be convenient and easily operating sensors for PA detection.