A nanostructured solid-contact electrode for real-time monitoring of copper nanoparticle dynamics and environmental analysis.

Copper ions (Cu²⁺) are environmentally significant due to their toxicity and widespread industrial use. Traditional detection methods are often time-consuming and not amenable to real-time analysis. This study presents the development of a solid-contact ion-selective electrode (SC-ISE) that enables real-time potentiometric monitoring of Cu²⁺ ions during copper nanoparticle (CuNP) synthesis, degradation, and environmental analysis. A novel SC-ISE was fabricated by modifying a screen-printed electrode with polyaniline nanoparticles as the ion-to-electron transducer, and a PVC membrane doped with β-cyclodextrin and Reinecke’s salt for Cu²⁺ selectivity. The sensor’s electrochemical performance was characterized under various conditions and applied for kinetic and thermodynamic studies of CuNP synthesis using L-ascorbic acid. The electrode exhibited a near-Nernstian slope (28.05 mV/decade) across a wide concentration range (10⁻⁸ to 10⁻² mol L⁻¹), a detection limit of 7.5 × 10⁻⁹ mol L⁻¹, fast response time (≤ 10 s), and stable performance within pH 6–9. Real-time monitoring of CuNP formation enabled calculation of activation energy (Ea = 34.06 kJ mol⁻¹), enthalpy (ΔH = 31.21 kJ mol⁻¹), and Gibbs free energy (ΔG > 77.9 kJ mol⁻¹), confirming an endothermic, non-spontaneous process. The electrode also tracked Cu²⁺ release during oxidative nanoparticle degradation and quantified Cu²⁺ in spiked environmental waters with 95.8–98.9% recovery. This study demonstrates, for the first time, the use of a Cu²⁺-selective SC-ISE as a portable kinetic and thermodynamic probe for nanoparticle processes, while also providing a green, low-cost platform for environmental water monitoring.