Near-infrared fluorescent turn-on detection of paraquat using an assembly of squaraine and surfactants

Paraquat (PQ) is one of an effective herbicides but it has extremely toxic effects on animals and humans. It is of great importance to selectively detect PQ with fluorescence response. The first “off–on” fluorescent method based on mechanism of surfactant-controlled aggregate–deaggregate of squaraines (SQ) for paraquat (PQ) recognition in near infrared region was constructed. In this approach, remote-controlled regulation endows unique advantages to fulfill the turn-on response to electron-deficient featured PQ which prefers to quench all reported fluorophores through electron transfer. The assembled system can selectively recognize PQ over other herbicides. The detection limit was calculated to be 95.7   μg   L −1 (3.72   ×   10 −7   M), which is lower than that of value (200   μg   L −1 ) recommended by the US Environmental Protection Agency (EPA). In addition, the system can be used for PQ detection in real sample.