A ratio fluorescence sensor based on rhodamine B embedded metal-organic framework for glyphosate detection in agri-food products

Glyphosate, a broad-spectrum and high-efficiency herbicide, could accumulate in the human body through the consumption of agri-food products. Herein, a ratio fluorescence sensor based on rhodamine B-embedded amino-functionalized iron-based metal-organic framework (MOF, NH2-MIL-88(Fe)@RhB) bonded with Cu2+ was developed for rapid detection of glyphosate. The synthesized NH2-MIL-88(Fe) was a biconical prism and had a cavity for the embedding of RhB as a reference compound. In the presence of Cu2+, Lewis interactions with NH2-MIL-88(Fe)@RhB cause the fluorescence signal to be turned off. When glyphosate was added, the signal was turned on due to chelation with Cu2+ and hydrogen bonding interactions with NH2-MIL-88(Fe)@RhB. Under optimal conditions, the developed sensor exhibited a linear range of 0.60-45 μmol L-1 with a response time of less than 1 min. The sensor was applied in the analysis of agri-food products (tea, soybean, wheat, cucumber), with recoveries between 97.93% and 109.06%, indicating its promising application in agri-food safety.