A Co 3 O 4 Nanoparticle-Modified Screen-Printed Electrode Sensor for the Detection of Nitrate Ions in Aquaponic Systems.

In this study, a screen-printed electrode (SPE) modified with cobalt oxide nanoparticles (Co 3 O 4 NPs) was used to create an all-solid-state ion-selective electrode used as a potentiometric ion sensor for determining nitrate ion (NO 3 - ) concentrations in aquaculture water. The effects of the Co 3 O 4 NPs on the characterization parameters of the solid-contact nitrate ion-selective electrodes (SC-NO 3 - -ISEs) were investigated. The morphology, physical properties and analytical performance of the proposed NO 3 - -ion selective membrane (ISM)/Co 3 O 4 NPs/SPEs were studied by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), potentiometric measurements, and potentiometric water layer tests. Once all conditions were optimized, it was confirmed that the screen-printed electrochemical sensor had high potential stability, anti-interference performance, good reproducibility, and no water layer formation between the selective membrane and the working electrode. The developed NO 3 - -ISM/Co 3 O 4 NPs/SPE showed a Nernstian slope of -56.78 mV/decade for NO 3 - detection with a wide range of 10 -7 -10 -2 M and a quick response time of 5.7 s. The sensors were successfully used to measure NO 3 - concentrations in aquaculture water. Therefore, the electrodes have potential for use in aquaponic nutrient solution applications with precise detection of NO 3 - in a complicated matrix and can easily be used to monitor other ions in aquaculture water.