An on-off-on fluorescent probe for the detection of glyphosate based on a Cu²⁺-assisted squaraine dye sensor

The herbicide glyphosate, N-(phosphonomethyl)glycine, has been widely used in the past 40 years, and has had many adverse effects on human health. Here, we constructed a convenient "on-off-on" fluorescent platform for detection of glyphosate via Cu²⁺ modulated squaraine dye fluorescence quenching. The squaraine dye F-0 exhibited strong fluorescence, which could be quenched by the addition of Cu²⁺. However, the addition of glyphosate restored the fluorescence intensity of F-0 due to the formation of a Cu²⁺-glyphosate complex. F-0 was utilized as a fluorescent probe for the quantitative detection of glyphosate, with the lowest detection limit of 13.16 nmol L^-1. Furthermore, this method demonstrated high selectivity and anti-interference capabilities. The successful monitoring of glyphosate in real samples was achieved using this detection strategy.