Fluorescent sensing of “quat” herbicides with a multifunctional pyrene-labeled monomer and molecular imprinting

A strongly blue-fluorescent disulfonated pyrenedimethacrylamide has been synthesized and its spectroscopic features tested in the presence of diquat (DQ) and paraquat (PQ) herbicides in water. UV–vis absorption revealed the formation of a 1:1 complex between the probe and the “quats”, the strongest binding with DQ occurring in acetonitrile (K = 1.84 × 106 M−1). Subsequent incorporation of the new pyrene derivative into cross-linked poly(acrylate–acrylamide) films as a fluorosensor afforded membranes able to detect waterborne diquat and paraquat herbicides by selective charge-transfer interaction. The film recognition features were enhanced by electrostatic interactions and molecular imprinting by preparing the sensing polymer layer in the presence of 1,1′-biphenyl-2,2′-diammonium ion as a surrogate of the target analytes. The sensor detection limits found are 162 and 281 nM for DQ for PQ, respectively, with good reproducibility (RSD < 4%, n = 4) in the calibration range (up to 9 μM).