A highly sensitive and selective ratiometric sensing platform based on 7-amino-4-methylcoumarin for naked-eye visual fluorescence sensing of Cu.

Cu is a major environmental pollutant. An efficient measurement for Cu is urgently needed. In this report, we have developed a new sensitive and selective ratiometric sensing platform using 7-amino-4-methylcoumarin (AMC) for detecting Cu in real samples. In the presence of Cu, o-phenylenediamine (OPD) could be catalytically oxidized to 2,3-diaminophenazine (DAP), which could react with AMC, leading to quench the fluorescence intensity of AMC at 438 nm. Meanwhile, DAP provided a new emission peak at 557 nm. Based on the efficient overlapped spectrum of AMC and DAP, a ratiometric sensing platform through fluorescence resonance energy transfer (FRET) was carried out. Furthermore, the as-proposed strategy displayed the linear relationship in the wide range from 6 to 250 μM with a low detection limit of 0.059 μM, and the recoveries of the spiked samples in real samples ranged from 86.5% to 110.1%. Moreover, comparing the visual fluorescence colors of the real samples with the standard colorimetric card, we used the as-proposed strategy as a solid-based platform for realizing an efficient semi-quantitative detection of Cu via naked-eye visual fluorescence mode without any complicated instrument and operation. The above results implied that the as-proposed strategy could be used in the practice determination of Cu.