High-performance ratiometric magnetic electrochemical sensor for acetamiprid detection using Ag@PDA@Fe3O4 nanocomposites

Acetamiprid (AAP) is a renowned neonicotinoid insecticide for swift insect control that is prone to residue in agricultural products and threatens human health. Magnetic electrochemical sensor (MES) was developed for high-precision detection of AAP based on silver nanoparticle (AgNPs) and polydopamine (PDA) modified Fe₃O₄ nanocomposites (Ag@PDA@Fe₃O₄). The electrochemical signals generated by AAP hydrolysis and AgNPs oxidation are respectively used as two special signal sources. An increase in AAP concentration led to a proportional increase in the signal from AAP hydrolysis at +0.9 V (I_AAP), while the signal from AgNPs oxidation at +0.27 V (I_Ag) correspondingly decreased. The output signal ΔI_AAP/ΔI_Ag (R²=0.9890) demonstrates a superior linear relationship compared to ΔI_AAP (R²=0.9790) or ΔI_Ag (R²=0.9740) alone. MES demonstrated a broad linear detection range from 0.01 to 2.00 mg L⁻¹ and an impressive limit of detection (LOD, 3S/M) at 3.6 µg L⁻¹. The incorporation of magnetic glassy carbon electrodes (MGCE) significantly mitigates the detachment of nanomaterials. MES has excellent stability and selectivity, and can successfully detect AAP in actual cowpea samples. This study provides pivotal insights into the design of nanomaterial-based ratiometric electrochemical sensors for the sensitive and selective detection of AAP.