Bis-tetraarylimidazole macrocycle: An effective fluorescent sensor for folic acid

Folic acid (FA) is an essential vitamin. The development of rapid, simple and on-site detecting method on FA is of great importance to human's health and industrial production. In this work, a bis-tetraarylimidazole macrocycle ( BTM ) was designed and synthesized as an effective fluorescent sensor for FA. The weak purple fluorescence of BTM was transferred to strong blue fluorescence after sensing FA with high sensing selectivity among 31 kinds of biomolecules and 16 kinds of ions. The limit of detection was as low as 1.06 × 10 −7  M, which was the competitive one among the reported fluorescence sensors. The sensing mechanism was deduced that FA was included in the cavity of BTM based on the multiple hydrogen-bonding actions and aromatic π-π stacking interaction. The intermolecular rotating restriction and the interruption of Dexter electron transfer after binding FA were responsible for the fluorescence enhancement. This sensing ability of BTM for FA was applied on test paper, seal experiment and stimulated samples, suggesting the good qualitative and quantitative detecting ability for FA with rapid, simple and on-site procedure in real environment.