Synergistic Effect in Hexacyanoferrate/Electro-Reduced Graphene Oxide Nanocomposites for Highly Sensitive Cesium Ion Detection

The detection of radioactive cesium ions (Cs⁺) in aqueous environments remains a critical challenge due to their high radiotoxicity, long half-life, and mobility in water. This work reports the development of a novel electrochemical sensor based on a nanocomposite of potassium nickel hexacyanoferrate (KNiHCF) nanoparticles uniformly distributed within electrochemically reduced graphene oxide (erGO) sheets, prepared via a one-step electrodeposition process. The composite film exhibits enhanced charge transfer properties and high surface accessibility, attributed to the homogeneous distribution of nanometric (2–10 nm) KNiHCF particles stabilized by erGO. XRD and STEM-EDS analyses confirm the formation of a mixed KNiHCF phase, while TEM imaging reveals effective nanoparticle anchoring that suppresses agglomeration. Electrochemical characterization using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrates sensitive and selective Cs⁺ detection in high ionic strength media (1 M NaCl or 1 M KCl), simulating contaminated seawater. The sensor exhibits a linear response over a broad concentration range (0.1 ppb to 100 ppm), with a remarkably low limit of detection (LOD) of 0.1 ppb. These enhanced performances are attributed to the synergistic combination of erGO conductivity, homogeneous distribution of KNiHCF nanoparticles, and redox sensitivity of Fe²⁺/Fe³⁺ couple to Cs⁺ intercalation. These findings present a scalable and cost-effective strategy for high-performance electrochemical Cs⁺ monitoring.