Dual modes of fluorescence sensing and smartphone readout for sensitive and visual detection of mercury ions in Porphyra.

A convenient and intuitive method for detecting trace heavy metal ions is vital for food safety and quality monitoring. Herein, a dual-emission ratiometric fluorescence probe based on Zr-based metal-organic frameworks (Zr-MOF) and silver nanoclusters (AgNCs) was assembled to sensitive and visual detect mercury ions (Hg). The sensor exhibits good sensitivity from 0.010 to 0.5 μg mL with a low detection limit of 1.8 μg L (corresponding to 0.72 μg kg by weight). The proposed method was finally applied to determine Hg in the Porphyra matrix with satisfactory outcomes, the analytical recoveries were in the range of 94.74%-101.1%, indicating the practicability of the developed method. Meanwhile, the smartphone-based colorimetric method was established by capturing the changes in fluorescence colors of the probes exposed to different Hg concentrations, with a quick sample-to-answer monitoring time of 10 min. The fluorescence probe, with these merits of simplicity, rapid response, and high sensitivity, offered a promising means for evaluating the safety of food polluted with Hg.