Green synthesis, characterization of formononetin mediated AgNPs and its testing for formothion in typical fruit and vegetable samples

In this study, a natural extract from the plant Radix hedysari (ER) was proven to be useful for the green synthesis of silver nanoparticles (AgNPs) and ER-AgNPs in particular. Considering the complexity of plant extracts, high-pressure liquid chromatography (HPLC) was effective at confirming the components of ER, surprisingly, formononetin was found to comprise more than 85% of the total contents. Since formononetin was confirmed to be the primary component of ER, this compound was also used as the basis to synthesize AgNPs designated FMT-AgNPs that was highly pure and of high quality. The FMT-AgNPs functionalized by formononetin were optimized for further study. A simple, fast and sensitive colorimetric method detect formothion was achieved using FMT-AgNPs. A wide linear range from 0.1 μM to 10 μM was established with a low limit of detection (LOD) of 14.6 nM. Since formononetin performed multiple roles during the synthesis, it was confirmed that the mechanism of detection was based on aldol condensation , intermolecular hydrogen bonds and electrostatic attraction between formononetin and formothion. Finally, the green synthesized FMT-AgNPs were further applied in typical fruit and vegetable samples, indicating that FMT-AgNPs were potentially highly useful.