Fabrication of novel electrochemical sensor based on NiO-nanoparticles for copper detection in drinking water

Nickel oxide film (NiO-nanoparticles) was successfully deposed onto the carbon graphite electrode (GrE) and used as an electrochemical sensor for the detection of trace levels of copper Cu(II) by using square wave anodic stripping voltammetry (SWASV). This cost-effective and simple sensor was developed through a two-step process. In the initial step, the electrochemical deposition of metallic nickel onto the carbon graphite electrode occurs in a 0.1 M boric acid and nickel salt solution. Subsequently, in the second step, the deposited metal undergoes anodic oxidation in a 0.1M NaOH solution. To characterize and verify the modification process of the electrode, several electrochemical and physico-chemical techniques were employed such as OCP, EIS, SEM, XRD and XPS. In an acid medium, the modified electrode exhibited a significant improvement in electrocatalytic activity for the oxidation of Cu(II) compared to bare GrE. The effect of several parameters on the sensor response were also examined. Under optimal conditions, the sensor exhibited a linear response to Cu(II) concentrations ranging from 0.0 to 1.5 × 10-7 M with a detection limit of 3.83 × 10-9 M, quantification limit of 1.37×10-8 M and a high sensitivity of 226.13 μA.M-1.cm-2. Furthermore, the sensor showed a good repeatability (RSD = 1.47 %), a good stability (retain 99.5 % after 40 measurements) and a minimal interference from ionic species was observed on the SWASV signals of Cu(II). The as-prepared sensor was then applied to determine the Cu(II) in two different brands of local source water, and the results were very satisfactory by showing a recovery values between 97.5 and 103.6%. In summary, our study presents an innovative and cost-effective electrochemical sensor utilizing a modified carbon graphite electrode for sensitive and accurate detection of copper at trace levels.