Oxygen vacancy-rich NiCo2O4 nanoparticles loaded on polyaniline nanowires for highly selective Pb2+ electrochemical sensing

Abstract

To satisfy the pressing demands for heavy metal ions (HMIs) detection, A novel sensor was developed to detect lead (Pb²⁺) ions based on oxygen vacancy-rich NiCo₂O₄ (NCO) nanoparticles and polyaniline (PANI) nanowires. The NCO/PANI nanocomposite was synthesized via a synergistic salt-assisted carbonization activation and conductive polymers doping strategy, which simultaneously introduced abundant oxygen vacancies and optimized the heterostructure interface. The NCO nanoparticles coupled with imine functional groups (-N=) on PANI create synergistic adsorption-catalytic sites for Pb²⁺. The sensitivity of the NCO/PANI-modified glassy carbon electrode (GCE) reached an impressive value of 14.96 μA·μM⁻¹, representing increases of 2.5-fold, 4.14-fold, and 24.9-fold compared to that of the NCO-modified GCE (5.99 μA·μM⁻¹), PANI-modified GCE (3.616 μA·μM⁻¹), and bare GCE (0.6 μA·μM⁻¹), respectively. This performance results from oxygen vacancies accelerated electron transfer, redox pair interactions (Co²⁺/Co³⁺, Ni²⁺/Ni³⁺), and enhanced Pb²⁺ adsorption by complexation and pore confinement. The sensing platform achieves an ultralow detection limit of 0.001 μM (S/N = 3) and exhibits robust anti-interference against common coexisting interferences (Cd²⁺, Cu²⁺, Fe²⁺, Ni²⁺, Zn²⁺, Fe³⁺ bisphenol A, catechol, hydroquinone, resorcinol), with satisfactory recovery (101 %–106.2 %) and excellent long-term stability in real water samples. This work not only establishes a robust foundation for optimizing material selection but also expands the horizon for the development of electrochemical sensing platforms.