Advanced Urea Precursors Driven NiCo2O4 Nanostructures Based Non-Enzymatic Urea Sensor for Milk and Urine Real Sample Applications

Abstract

The electrochemical performance of NiCo₂O₄ with urea precursors was evaluated in order to develop a non-enzymatic urea sensor. In this study, NiCo₂O₄ nanostructures were synthesized hydrothermally at different concentrations of urea and characterized using scanning electron microscopy and X-ray diffraction. Nanostructures of NiCo₂O₄ exhibit a nanorod-like morphology and a cubic phase crystal structure. Urea can be detected with high sensitivity through NiCo₂O₄ nanostructures driven by urea precursors under alkaline conditions. A low limit of detection of 0.05 and an analytical range of 0.1 mM to 10 mM urea are provided. The concentration of 006 mM was determined by cyclic voltammetry. Chronoamperometry was used to determine the linear range in the range of 0.1 mM to 8 mM. Several analytical parameters were assessed, including selectivity, stability, and repeatability. NiCo₂O₄ nanostructures can also be used to detect urea in various biological samples in a practical manner.

Keywords: NiCo2O4 nanostructures; alkaline conditions; non-enzymatic sensor; urea precursors.

Scheme 1

Synthesis of NiCo₂O₄ nanostructured materials by hydrothermal method followed by calcination in air.

Figure 1

(a) XRD patterns of NiCo₂O₄ samples prepared with various concentrations of urea (Samples 1–3), (b–d) effect of various urea concentrations (Samples 1–3) on the morphology of NiCo₂O₄ nanomaterial.

Figure 2

(a) CV curves of bare GCE (BGCE) and modified glassy carbon electrode (MGCE) with Sample 3 NiCo₂O₄ nanomaterial, Samples 1 and 2, 50 mV/s in the presence of 0.1 mM urea and only in 0.1 M NaOH, (b) CV curves of Samples 1 and 2 based NiCo₂O₄ nanomaterial, at 50 mV/s in the presence of 0.1 mM urea prepared in 0.1 M NaOH.

Figure 3

(a) CV curves of Sample 2 based on NiCo₂O₄ nanomaterial, at various scan rates in the presence of 0.1 mM urea prepared in 0.1 M NaOH, (b) Linear plots of anodic and cathodic peak currents.

Figure 4

(a) CV curves of Sample 2 based on NiCo₂O₄ nanomaterial, at 50 mV/s in the presence of various urea concentrations prepared in 0.1 M NaOH, (b) Linear plot of oxidation peak current versus different urea concentrations.

Figure 5

(a) chronoamperometry response of Sample 2 based on NiCo₂O₄ nanomaterial, at 0.6 V in the presence of various urea concentrations prepared in 0.1 M NaOH, (b) Linear plot of amperometeric generated current against various urea concentrations.

Figure 6

(a) CV curves of Sample 2 based on NiCo₂O₄ nanomaterial for the monitoring of stability and repeatability, at 50 mV/s in the presence of 0.1 mM urea concentration prepared in 0.1 M NaOH, (b) illustration of peak current in bar graph for the statistical error for the demonstration of stability and repeatability of material.

Figure 7

(a–c) Cyclic voltammetry measured for Samples 2 and 3 and Sample 1 in 0.5 mM urea solution at different scan rates. (d) Linear plots of anodic and cathodic current density difference for each scan rate for the quantification of (ECSA).