Incorporation of Fe₂O₃ Spacer Molecules in Microwave-Exfoliated Graphene Oxide as Efficient Electrodes for Simultaneous Detection of Cd²⁺, Pb²⁺, and Hg²⁺ in Water

Toxic adverse effects to human beings caused by heavy metal ions resemble a serious threat to mankind and often appear in the journal headlines. However, simultaneous detection of heavy metal ions using analytical tools is challenging. In this regard, simultaneous electrochemical detection of Cd²⁺, Pb²⁺, and Hg²⁺ ions in water is presented using iron oxide (Fe₂O₃) nanostructures as spacers incorporated between microwave-exfoliated graphene oxide (MEGO). First, Fe₂O₃ nanostructures are synthesized using ferric nitrate in presence of poly(vinylpyrrolidone) and followed by their in-situ incorporation into expanded graphene oxide (GO). Exfoliated GO accommodates large amount of Fe₂O₃ nanoparticles via microwave-assisted method, minimizing the restacking of GO sheets. Consequently, Fe₂O₃-incorporated MEGO (Fe₂O₃-MEGO) fabricated on screen-printed electrodes (SPE) demonstrate well-separated anodic peak potentials at −0.65, −0.45, and +0.27 V for Cd²⁺, Pb²⁺, and Hg²⁺ ions. Moreover, Fe₂O₃-MEGO/SPE electrode exhibits wide linear range (0.4 to 74.78 μM), high sensitivities (8.11, 9.59, and 3.01 μA μM⁻¹ cm⁻²) with low detection limits (0.2, 0.17, and 0.25 μM) for Cd²⁺, Pb²⁺, and Hg²⁺ ions, respectively. Therefore, this kind of incorporating nanomaterials as spacer molecules between GO allows for the design of alternative pathways to minimize restacking of GO and to increase sensitivity toward multiple targeted species.