A Ratiometric Fluorescence Sensor Based on Bifunctional Cu-MOF Nanozyme for Dual-Signal Detection of Glyphosate in Actual Samples

Abstract

This study proposes a glyphosate (GLY) detection strategy based on metal-organic framework (MOF) nanozymes, achieved by synthesizing copper-based MOF nanozyme (Cu-MOF) via a one-pot hydrothermal method and integrating them into a ratio-fluorescence sensing platform. This Cu-MOF nanozyme exhibits not only oxidase activity but also strong fluorescence properties, with a maximum emission wavelength of 435 nm under 328 nm excitation light. In the presence of o-phenylenediamine (OPD), the oxidase activity of Cu-MOF catalyzes the oxidation of OPD to 2,3-diaminophenazone (oxOPD). This compound fluoresces at 570 nm while quenching the Cu-MOF fluorescence at 435 nm. Upon GLY addition, it forms chelates with Cu2+ sites in the MOF, thereby inhibiting oxidase activity and reducing oxOPD production. This results in reduced fluorescence quenching at 435 nm and decreased emission intensity at 570 nm. This ratio sensor exhibits high selectivity toward GLY, with a linear range of 0-14 μM and a detection limit of 43 nM. Additionally, we developed a smartphone-based detection platform. By capturing fluorescence images and processing RGB values, this platform enables rapid on-site detection, providing a practical solution for GLY monitoring.