Development of a dual sensor for glyphosate and paraquat detection based on graphite screen-printed electrode modified with mesoporous silica-platinum coated with molecularly imprinted polymer

This thesis concerns the developed of a ready-to-use sensor based on a graphite screen-printed electrodes modified with dual-molecularly imprinted polymers coating on a mesoporous silica-platinum core (MSN-PtNPs@d-MIP/GSPE) for simultaneous determination of paraquat (PQ) and glyphosate (GLY). Amino mesoporous silica nanoparticles (MSN-NH2) were first synthesized through a co-condensation method using organo-silicates of tetraethyl orthosilicate (TEOS) and 3-Aminopropyl-trimethoxysilane (APTMS). MSN-PtNPs were synthesized by chemical reduction of Pt4+ to PtNPs for decorating the PtNPs on the surface of MSN-NH2. Finally, the dual-MIP was successfully coated on the MSN-PtNPs core with pre-polymerization acrylic acid (AA) and N-vinyl-2-pyrrolidone (VP) monomers with N, N´-(1,2-dihydroxyethylene) bis (acrylamide) (DHEBA) cross-linker under UV light and then was completely polymerized by heating. Additionally, the differential pulse voltammetry (DPV) was used for simultaneous quantitative analysis. Oxidation current signals appear at -0.95 V for PQ and +0.97 V for GLY and the dual-MIP sensor showed excellent linear calibration curves for both analytes in the range of 0.025 to 500 μM with a limit of detection of 3.1 nM for PQ and 4.0 nM for GLY. Dual-MIP sensors offer high selectivity and specificity due to the increased interaction of the imprinted cavities formed on the polymer film with the target PQ and GLY molecules. The developed dual-MIP sensor exhibits good reproducibility (RSD < 3.0%, n = 10) and high stability (remaining 82% effective after 4 weeks). The novel dual-MIP sensor was successful in monitoring PQ and GLY concentrations simultaneously in certified reference material (CRM) and water samples. Results obtained from this method are consistent with those obtained from the HPLC method. The ready-to-use dual-MIP sensor is excellent for water-quality control and on-site environmental applications without sophisticated instrumentation.