Novel Synthesis of Sensitive Cu-ZnO Nanorod-Based Sensor for Hydrogen Peroxide Sensing

Abstract

We aimed to synthesize sensitive electrochemical sensors for hydrogen peroxide sensing by using zinc oxide nanorods grown on a fluorine-doped tin oxide electrode by using the facial hydrothermal method. It was essential to keep the surface morphology of the material (nanorods structure); due to its large surface area, the concerned material has enhanced detection ability toward the analyte. The work presents a non-enzymatic H₂O₂ sensor using vertically grown zinc oxide nanorods on the electrode (FTO) surfaces with Cu nanoparticles deposited on zinc oxide nanorods to enhance the activity. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-Ray (EDX), X-ray diffraction (XRD), and electrochemical methods were used to characterize copper-zinc oxide nanorods. In addition to the high surface area, the hexagonal Cu-ZnO nanorods exhibited enhanced electrochemical features of H₂O₂ oxidation. Nanorods made from Cu-ZnO exhibit highly efficient sensitivity of 3415 μAmM^-1cm^-2 low detection limits (LODs) of 0.16 μM and extremely wide linear ranges (0.001-11 mM). In addition, copper-zinc oxide nanorods demonstrated decent reproducibility, repeatability, stability, and selectivity after being used for H₂O₂ sensing in water samples with an RSD value of 3.83%. Cu nanoparticles decorated on ZnO nanorods demonstrate excellent potential for the detection of hydrogen peroxide, providing a new way to prepare hydrogen peroxide detecting devices.

Keywords: Cu-ZnO nanorods; H2O2 detection; electrochemical sensor; hydrothermal method; sensing.

SCHEME 1

Synthesis and manufacturing of zinc oxide nanorods on the electrode surface, followed by the deposition of Cu nanoparticles for hydrogen peroxide detection, are depicted schematically.

FIGURE 1

XRD spectral analysis of Cu-modified zinc oxide nanorods before (a) and after (b) deposition of Cu nanoparticles.

FIGURE 2

(A) Uniformly distributed ZnO nanoseeds on the substrate; (B,C) show the vertically developed zinc oxide nanorods on the concerned electrode surface; (D,E) shows the SEM images of fabricated copper-zinc oxide nanorods at low and high resolution; and (F) shows the EDS spectral analysis of copper–zinc oxide nanorods.

FIGURE 3

(A) Compare the XPS spectra of Cu-ZnO nanorods to the spectra of ZnO nanorods. It was also reported that the simplified peaks for oxygen (B) O1s, (C) zinc Zn 2p, and deposited material Cu 2p (D) elements with their magnified spectra were also mentioned.

FIGURE 4

(A) Resistance capacity of Cu-ZnO nanorods, zinc oxide nanorods, Cu nanoparticles, and blank FTO, was best described by plotting Nyquist semicircle in standard 0.1 mol/L KCl containing a 0.1 M K₄ [Fe(CN)₆] and K₃ [Fe(CN)₆] solution. (B) CV results of blank FTO with further modified electrodes zinc oxide nanorods, Cu nanoparticles, and Cu-ZnO nanorods were mentioned in standard KCl containing K₄ [Fe(CN)₆] and K₃ [Fe(CN)₆] solution.

FIGURE 5

(A) Expressed that at a fixed scan rate of 50 mVs⁻¹, and the CV curve of zinc oxide nanorods, Cu-ZnO NRs, and blank FTO in 0.1 mol/L phosphate buffer containing 0.2 mM hydrogen peroxide was mentioned. (B) Shows the various hydrogen peroxide concentrations, the CV curves of blank FTO, zinc oxide nanorods, and produced Cu-ZnO nanorods are compared.

FIGURE 6

(A) Depicted the DPV graph of Cu-ZnO nanorods at various hydrogen peroxide concentrations. (B) Amperometric response of copper-zinc oxide nanorods in 0.1 mol/L phosphate electrolyte with varied potentials ranging from (0.65–0.85 V) was discussed. The I-T graph of Cu-ZnO nanorods, with various hydrogen peroxide concentrations, is shown at a specific potential of +0.8 V (C). The insert shows a magnified I-T graph of Cu-ZnO nanorods. For Cu-ZnO nanorods, the corresponding linear graph of current vs. hydrogen peroxide concentration is displayed in (D). Insert mentioned the magnified linear graph.

FIGURE 7

(A) Cu-ZnO nanorod stability was evaluated for 500 cycles in 0.2 mM hydrogen peroxide in phosphate electrolyte at a fixed scan rate of 50 mVs⁻¹. (B) Anti-interference results for all probable interfering compounds such as fructose, Phe, Ala, Gly, Val, DA, CA, UA, AA, and Pen were expressed.

FIGURE 8

Percentage of recovery results in an actual water sample test of a water sample and an industrial water sample, with a histogram graph was mentioned.