Surface acoustic wave sensor based on nickel(II) phthalocyanine thin films for organophosphorous pesticides selective detection

A surface acoustic wave (SAW) chemosensor functionalized with a thin layer of nickel (II) phthalocyanine (NiPc) has been designed for the selective detection, in liquid solution, of two highly toxic organophosphorous (OPs) pesticides: methidathion and omethoate. Contrarily to previous studies, in which phthalocyanines are only used as mediators to enhance the activity of acetylcholinesterase enzyme, here NiPc film plays the role of the SAW sensor recognition layer for OPs. Sensitivities of the developed chemosensor are of order of 0.17°/nM and 0.1°/nM for omethoate and methidation, respectively. The limit of detection of 1 nM is by far lower than values presented in literature and than those of OPs maximum concentrations recommended by the OSAV (0.1 mg/kg and 0.003 mg/kg for methidathion and omethoate respectively). Selectivity tests made with Simetryn and Terbutylazine-2-hydroxy (Pestanal), show that the developed sensor displayed an excellent recognition capacity toward OPs. Possible sensing mechanism(s) have been proposed to explain the nature of interactions between the investigated molecular systems and nickel phthalocyanine.