Label-free competitive electrochemical immunosensor based on Fe-MOFs/rGO/AuNPs ternary nanocomposite for sensitive Hg2+ detection

A Fe-MOFs/rGO/Au ternary composite to construct a competitive electrochemical immunosensor for Hg 2+ . • The porous conductive hybrid accelerates mass transfer and provides abundant antibody binding sites. • The established immunosensor exhibits two linear range of 0.05–200 and 250–2500 nM of Hg 2+ . • The established immunosensor displays the specific selectivity and a low LOD of 0.075 nM. • The sensing platform shows the promising potential for environmental heavy metal monitoring. The development of ultrasensitive Hg 2+ detection in water environments is crucial owing to its severe toxicity to ecosystems and human health. In this work, a label-free competitive electrochemical immunosensor was fabricated for the detection of mercury ions (Hg 2+ ) based on a ternary iron-based metal organic framework/reduced graphene oxide/gold nanoparticles (Fe-MOFs/rGO/AuNPs) nanocomposite. The Fe-MOFs/rGO hybrid composite was synthesized via a hydrothermal strategy, which significantly enhanced the conductivity and effective surface area of the electrode interface. Furthermore, L-cysteine-mediated AuNPs were covalently conjugated to the Fe-MOFs/rGO matrix, which not only offered a stable substrate for the immobilization of anti-Hg 2+ antibodies but also accelerated interfacial electron transport. By monitoring the current response through differential pulse voltammetry (DPV), the immunosensor exhibited the two linear ranges of 0.05–200 nM and 250–2500 nM toward Hg 2+ , accompanied by an ultralow detection limit (LOD) of 0.075 nM. Benefiting from the synergistic effect of the ternary nanocomposite as well as the outstanding specificity of antibody-antigen immunorecognition, the developed immunosensor meets the requirement for the safety monitoring Hg 2+ in complex environmental water samples. Download: Download high-res image (152KB) Download: Download full-size image