Boosted adsorption and ultra-trace sensing: Phytic acid-coordinated Fe3O4 for a binder-free electrochemical platform targeting heavy metals

One-pot synthesis of PA-functionalized Fe 3 O 4 for enhanced dispersion and heavy metal adsorption. • DFT calculations reveal strong multidentate coordination between PA and Pb 2+ /Cu 2+ /Hg 2+ . • Binder-free sensor built via magnetic immobilization of Fe 3 O 4 @PA on MGCE, maximizing active sites. • Ultra-sensitive detection of Pb 2+ , Cu 2+ , and Hg 2+ with pM-level detection limits in real water. The development of advanced functional nanomaterials is critically important for constructing high-performance electrochemical sensors capable of sensitive and selective detection of heavy metal contaminants. Herein, we report a magnetic composite consisting of ferrosoferric oxide (Fe 3 O 4 ) nanoparticles functionalized with phytic acid (PA), a naturally abundant molecule bearing multiple phosphate (-PO 4 3− ) coordination groups. The Fe 3 O 4 @PA composite was synthesized via a homogeneous precipitation strategy and directly immobilized onto a magnetic glassy carbon electrode (MGCE) to fabricate a film-free electrochemical sensing interface for the simultaneous determination of Pb 2+ , Cu 2+ , and Hg 2+ . Experimental electrochemical measurements combined with density-functional theory calculations demonstrated that PA functionalization significantly enhances the affinity of Fe 3 O 4 toward heavy metal ions through strong multidentate coordination interactions, leading to markedly improved adsorption and preconcentration efficiency. Moreover, the strong magnetic attraction between Fe 3 O 4 @PA and the MGCE enabled stable electrode modification without the use of additional film-forming binders, thereby simplifying sensor fabrication while maximizing the effective adsorption surface area. Benefiting from these synergistic effects, the resulting sensor exhibited outstanding analytical performance, achieving ultra-low limits of detection of 0.015 pM for Pb 2+ , 8.13 pM for Cu 2+ , and 4.60 pM for Hg 2+ . The sensor also demonstrated excellent applicability for the simultaneous determination of Pb 2+ , Cu 2+ , and Hg 2+ in real water samples, highlighting its strong potential for practical environmental monitoring and on-site analysis. Download: Download high-res image (68KB) Download: Download full-size image