Better Together: Synergistic Enhancement of AuNPs and Bifunctional Monomers in a Dual-Channel Molecularly Imprinting Electrochemical Sensor for Simultaneous Detection of Diuron and Thidiazuron

The combination of diuron (DU) and thidiazuron (TDZ) is commonly used in cotton production for its excellent adaptability to low temperatures, which may lead to increased crop and soil pollution. The simultaneous detection of DU and TDZ poses significant challenges due to their weak and overlapping signals, along with an unclear electrochemical detection mechanism for TDZ. This study developed a dual-channel multifunctional molecularly imprinted electrochemical (MMIP-EC) sensing platform by optimizing the substrate material and MIP layer for high performance. First, amino-functionalized graphene-based poly(pyrrole)-poly(3,4-ethylenedioxythiophene) (NH₂-rGO/PPy-PEDOT) with high conductivity was synthesized as the substrate. Subsequently, MMIPs were prepared in one step using electropolymerization by introducing chloroauric acid (HAuCl₄) and bifunctional monomers (dopamine and thiophene). This method not only enhanced specific binding capacity of the MMIP layer but also amplified the signal through the synergistic effect of reduced AuNPs and bifunctional monomers. Furthermore, two independent modules (MMIP-DU and MMIP-TDZ) were integrated into a dual-channel EC platform for simultaneous transmission of DU and TDZ responses to separate windows. Finally, based on high-performance liquid chromatography-mass spectrometry (HPLC-MS) and electrochemical kinetics studies, it was speculated that the electrochemical oxidation of TDZ via the carbonylation of a secondary amine under strongly acidic conditions, followed by hydrolysis to form a carboxyl group, reveals the electrochemical oxidation mechanism of TDZ. The developed sensor exhibited excellent performance in selectivity and sensitivity, with low detection limits of 26.6 pg/mL (DU) and 39.2 pg/mL (TDZ). In conclusion, this sensing platform presents a novel perspective for the cost-effective and highly efficient detection of diverse environmental pollutants.