Abstract
This study presents the design and application of an electrochemical sensor for selective detection of lead ions (Pb(2+)) based on ionophore-modified raspberry-like Fe(3)O(4)-Au nanostructures. The material was engineered with a magnetic Fe(3)O(4) core, coated with polyethyleneimine (PEI) to facilitate nucleation, and subsequently decorated with Au nanoparticles, providing a raspberry-like (Fe(3)O(4)@PEI@AuNPs) nanostructure with high surface area and excellent electrochemical conductivity. Surface functionalization with Lead Ionophore IV (ionophore thiol) introduced Pb(2+)-selective binding sites, whose presence and structural evolution were verified by TEM and Raman spectroscopy. The Fe(3)O(4) core endowed strong magnetic properties, enabling facile manipulation and immobilization onto screen-printed carbon electrodes (SPCEs) via physical adsorption, while the Au nanoparticles enhanced electron transfer, supplied thiol-binding sites for stable ionophore anchoring, and increased the effective electroactive surface area. Operational conditions were systematically optimized, with acetate buffer (HAc/NaAc, pH 5.7) and chronoamperometric preconcentration (CA) at -1.0 V for 175 s identified as optimal for differential pulse voltammetry (DPV) measurements. Under these conditions, the sensor exhibited a linear response toward Pb(2+) from 0.025 mM to 2.00 mM with superior sensitivity and reproducibility compared to conventional AuNP-modified SPCEs. Furthermore, the ionophore-modified Fe(3)O(4)-Au nanostructure-based sensor demonstrated outstanding selectivity for Pb(2+) over competing heavy metal ions (Cd(2+), Hg(2+), Cr(3+)), owing to the specific coordination interaction of Lead Ionophore IV with target ions. These findings highlight the potential of raspberry-like Fe(3)O(4)@PEI@AuNP nanostructures as a robust and efficient electrochemical platform for the sensitive and selective detection of toxic heavy metal ions.