PPy-Functionalized NiFe₂O₄ Nanocomposites toward Highly Selective Pb²⁺ Electrochemical Sensing

Driven by the urgent requirement to monitor the trace amount of heavy metal ions, a novel electrochemical sensing platform is constructed by surface modification of magnetic NiFe₂O₄ nanoparticles with polypyrrole (PPy). This NiFe₂O₄/PPy nanocomposite has a unique three-dimensional network architecture. Under the optimized experimental conditions, the fabricated sensor exhibits enhanced sensing performance for selective recognition of trace Pb²⁺ in the range of 0.1–2.1 μM by square wave anodic stripping voltammetry. The sensitivity of a NiFe₂O₄/PPy-decorated glassy carbon electrode (GCE) toward Pb²⁺ is verified to be superior to that of both bare GCE and NiFe₂O₄-decorated GCE, and an extremely low detection limit of 3.9 nM (S/N = 3) can be achieved. The accurate detection of Pb²⁺ is also challenged by various aqueous media and satisfactory recoveries varied from 98–107%, endowing it with great prospects in the analysis of real water samples. Moreover, the interferences from coexisting ions such as Cd²⁺, Fe³⁺, Zn²⁺, Ni²⁺, Cu²⁺, and Na⁺ can be ignored to some extent. The present study not only provides a new candidate for the efficient detection of Pb²⁺ but also sheds light on exploring advanced electrode materials to rationally design sensing interfaces.