A novel ratiometric sensor for fluorimetric and visual dual-mode detection of Al in environmental water based on the target-regulated formation of Eu MOFs.

Herein, a novel ratiometric sensor for fluorimetric and smartphone-assisted visual detection of Al in environmental water was developed based on the target-regulated formation of Eu metal-organic frameworks (Eu MOFs). By employing 2-[4-(2-hydroxyethyl) piperazin-1-yl] ethanesulfonic acid (Hepes), Eu and tetracycline (TC) as raw materials, Eu MOFs with red emission were facilely synthesized through the coordination of Eu with Hepes and TC. However, upon the introduction of Al, a higher affinity of TC towards Al resulted in the formation of a TC-Al complex with green fluorescence and inhibited the generation of Eu MOFs. This led to an increase in green fluorescence and a decrease in red fluorescence accompanied by the fluorescence color of the solution changing from red to green under the illumination of the UV lamp. Thus, a ratiometric sensor for fluorimetric and the smartphone-assisted visual detection of Al was established. The ratiometric sensor exhibited high sensitivity for Al detection with a detection limit of 0.14 μM for fluorescence detection and 1.21 μM for visual detection. Additionally, the proposed strategy was successfully applied to detect Al in the environmental water samples with satisfactory results, indicating great application prospects for environmental monitoring.