Ratio fluorescence test strip visualized by amino-functionalized metal-organic framework for rapid sensing of glyphosate.

As glyphosate is a broad-spectrum herbicide extensively used in agriculture worldwide, rapid glyphosate detection is essential for food safety and human health. Herein, a ratio fluorescence test strip was prepared and coupled with an amino-functionalized bismuth-based metal-organic framework (NH-Bi-MOF) that bonded with copper ion for rapid visualization and determination of glyphosate. NH-Bi-MOF had excellent fluorescence performance, and the copper ion, a Lewis acid, was selected as the quencher. The strong chelation of glyphosate with copper ion and its quick interaction with NH-Bi-MOF would turn on the fluorescence signal, thus enabling the quantitative sensing of glyphosate, with a linear range of 0.10-200 µmol L, and recoveries between 94.8% and 113.5%. The system was then expanded to a ratio fluorescence test strip, in which the fluorescent ring sticker was set as a binding-in self-calibration to reduce errors from the angle and light dependency. The method realized the visual semi-quantitation referring to a standard card, as well as the ratio quantitation using the gray value output with LOD of 0.82 µmol L. And the as-developed test strip was accessible, portable, and reliable, thus offering a platform for the rapid on-site detection of glyphosate and other residual pesticides.