Computationally guided fabrication of chlorpyrifos electrochemical sensor based on molecularly imprinted polymer decorated with au nanoparticles

Food safety is a priority for life; that is why pesticide levels are controlled worldwide. Chlorpyrifos (CPF) is one of the oldest and cheapest organophosphorus pesticides, which is now globally banned except for eleven crops. Specific onsite determination of such toxic pesticide is a must to ensure food safety. Molecular imprinting polymerization (MIP) is an exceptional technique to provide specificity. Recent advances in MIP technology have introduced the use of new monomers and monomers' combinations for improved performance. Here we report the first-time application for methyldopa (MD) and o-phenylenediamine (OPD) as copolymerized monomers in the preparation of MIP-sensor through the electro-polymerization method. First, a computational simulation was used to test the binding affinities of CPF using numerous monomers. The most stable complex, identified through the simulation, was formed with both MD and OPD. Experimental optimization of the ratio between CPF, MD, and OPD led to a 1:1:2 ratio as optimal for polymer performance that was further validated via UV-Visible spectrophotometry. Poly-methyldopa-o-phenylenediamine (PMD/POPD) polymer was prepared in the presence of CPF, where gold nanoparticles (Au-NPs) were then layered onto the polymer generated on the pencil graphite surface (Au-NP@PMD-POPD/PG). Characterization of the developed MIP electrochemical sensor was done using electron microscopy, photoelectron spectroscopy and other techniques. The prepared sensor was successfully exploited for CPF quantification using differential pulse voltammetry, where it showed a linearity range (5.0 x 10-13 M - 1.0 x 10-10 M) with a detection limit of 1.0 x 10-14 M. The fabricated sensor showed high selectivity and proved suitable for the determination of CPF concentration in pesticide market products and real water samples.