Metal oxide nanoparticles as solid contact in ion-selective electrodes sensitive to potassium ions

In recent years, various types of nanomaterials and nanoparticles have been very popular, also in analytical chemistry for sensors preparation. Ion-selective electrodes with solid contact were constructed, in which a layer of nanoparticles of selected metal oxides (zinc, copper and iron oxides) obtained by pulsed laser liquid ablation (PLAL) was placed between the glassy carbon solid electrode material and the ion-selective membrane. The basic analytical parameters of the obtained sensors were determined using potentiometric methods. Additionally, the electrochemical impedance spectroscopy method (EIS) was also used to investigate the electrical properties of the sensors. The obtained results were compared for all types of electrodes, both modified and unmodified, in order to investigate the effect of the type of nanoparticles and the thickness of their layer used as solid contact. It was found that the addition of metal oxide nanoparticles improved the analytical parameters of the sensors, mainly the potential stability and electrical parameters. The best results were obtained for an electrode with an intermediate layer of zinc oxide nanoparticles. In this case, a slope of -56.07 mV/dec, a linearity range of 1 × 10^-5 - 1 × 10^-1 mol L^-1 and a limit of detection of 3.66 × 10^-6 mol L^-1 were obtained. Particularly noteworthy is the significant improvement in the stability of the potential of this electrode and the long life of more than 5 months.