Sensitive and selective turn-on fluorescent switch based on europium-functionalized fluorescent covalent for rapid monitoring of an anthrax biomarker

Here, we develop an europium-functionalized covalent organic framework (Dpy-Bt-COF@Eu3+) as the turn-on fluorescent switch for highly sensitive and selective monitoring of a major B. anthracis biomarker, dipicolinic acid (DPA). Eu3+ actually performs two roles during the sensing process: the clear response signal, and recognition sites toward DPA, when Dpy-Bt-COF acted as the protector for Eu3+. Once adding DPA into Dpy-BtCOF@Eu3+, DPA exchanged water molecules to cooperate with Eu3+ and transmitted energy to it immediately, and thereby triggering visual fluorescence change. Attractively, Dpy-Bt-COF@Eu3+ can fast respond toward DPA within only 10 s. The sensor platform displayed an ultralow detection limit of 12.5 nM for DPA, well below the content of DPA (60 mu M) produced by the contagious amount of B. anthracis required to result in anthrax. Our work not only demonstrates great prospect of Eu3+-based COF for DPA detection, but also provides a potential way to explore other functionalized materials for the monitoring of other targets.