Dye-based dual-emission Eu-MOF synthesized by Post-modification for the sensitive ratio fluorescence visualization sensing of ClO.

As we all know, excessive hypochlorite will be transformed into highly toxic substances, while insufficient hypochlorite can not completely kill bacteria and viruses in water. Therefore, it is desirable to develop a new analytical method to detect ClO- in environmental water. Here, a novel and simple fluorescence sensor was constructed for monitoring ClO- by an effective strategy. An Acriflavine@lanthanide metal-organic framework (Acr@Eu(BTEC)) was designed by covalently integrating amino-rich dye (Acr) and carboxyl-rich Eu(BTEC) via post-synthesis method. The created fluorescence sensor has two emission centers originating from Acr and Eu(BTEC), respectively. In the presence of ClO-, the strong green fluorescence derived from Acr was significantly quenched, while the invariant red emission from Eu3+ acted as the reference signal. Thus, Acr@Eu(BTEC) with two emissions was developed as a ratiometric fluorescence sensor for highly sensitive and selective detection of ClO-. The limit of detection (LOD) was as low as 10.75 nM. Moreover, visual detection of ClO- by the naked eyes is feasible with obvious fluorescent color changes from green to orange and then red. This method shows excellent performance in practical application, which suggests that it has great potential in water quality monitoring.