Nickel-Based Nanoparticles Synthesized by Pulsed Laser Ablation in Liquid with Multiphase Structure for...

Nickel-based nanoparticles (NiNPs) synthesized by pulsed laser ablation in liquid (PLAL) were investigated as a green electrocatalytic phase for dopamine (DA) sensing. NiNPs were produced directly in ultrapure water and combined with Nafion, and drop-cast onto a glassy carbon electrode (GCE) to obtain a hydroxide-rich nickel-based/ionomer composite film. Transmission electron microscopy, X-ray diffraction, dynamic light scattering, and zeta-potential measurements confirmed a multiphase composition predominantly comprising Ni-(OH)₂, with minor metallic Ni and NiO domains, and revealed that incorporation into the sulfonated polymer reverses the nanoparticle surface charge from positive to negative. This charge inversion enhances the preconcentration and electrocatalytic oxidation of protonated dopamine at the composite interface. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicate a quasi-reversible electron transfer governed by a mixed adsorption-diffusion mechanism. Under optimized conditions in Britton-Robinson (B-R) buffer (pH 3.0), the cathodic peak current varies linearly with dopamine concentration between 0.25 and 100 μmol L^-1, with a detection limit of 92 nmol L^-1. The sensor exhibits good repeatability and tolerance to common urinary interferents, and enables accurate determination of dopamine in synthetic human urine, with recoveries between 93.5 and 104.4%. These results demonstrate that PLAL-derived NiNPs provide an environmentally friendly and efficient platform for electrochemical monitoring of DA.