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<p>Allura Red (AR) is a red azo dye used in the health, beauty, pharmaceutical, and food industries. It is hazardous, causing an oxidative stress response and altering gene expression. As a result, it is critical to identify and quantify its concentration. In this work, bismuth oxide (Bi<sub>2</sub>O<sub>3</sub>), manganese dioxide (MnO<sub>2</sub>), and manganese dioxide–bismuth oxide (MnO<sub>2</sub>-Bi<sub>2</sub>O<sub>3</sub>) were synthesized using <i>Mentha spicata</i> leaf extract via a hydrothermal method. Subsequently, graphite electrodes (GE) modified with Bi<sub>2</sub>O<sub>3</sub>, MnO<sub>2</sub>, and the MnO<sub>2</sub>-Bi<sub>2</sub>O<sub>3</sub> nanocomposite were developed as electrochemical sensors for detecting AR in food samples. The elemental composition, functional bond, crystal structure, morphology, and elemental mapping were confirmed using energy-dispersive x-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM), respectively. Differential pulse voltammetry (DPV) revealed that the anodic peak current demonstrated a linear relationship with AR concentrations between 1&#xa0;μM and 5&#xa0;μM. At a scan rate of 45&#xa0;mV/s, the highest current response was achieved at the optimal potential range of −300&#xa0;mV to 600&#xa0;mV at pH = 11. A strong linear correlation between AR concentration and current was demonstrated by the electrochemical sensing probe, which exhibited sensitivity of 1.14 mA/μM/cm<sup>2</sup>, 1.27 mA/μM/cm<sup>2</sup>, and 1.28 mA/μM/cm<sup>2</sup>, and corresponding limits of detection (LOD) of 0.7455&#xa0;μM, 0.4462&#xa0;μM, and 0.4084&#xa0;μM for Bi<sub>2</sub>O<sub>3</sub>-GE, MnO<sub>2</sub>-GE, and MnO<sub>2</sub>-Bi<sub>2</sub>O<sub>3</sub>-GE, respectively, with correlation coefficients (<i>R</i><sup>2</sup>) of 0.9834, 0.994, and 0.9924, respectively. Analytical factors were also studied, including sensitivity, linearity, repeatability, reproducibility, and stability. The real sample analysis in food samples (soft drinks and tomato sauce) yielded a satisfactory recovery percentage between 95% and 105%. Therefore, the experimental investigation of the MnO<sub>2</sub>-Bi<sub>2</sub>O<sub>3</sub> nanocomposite sensor confirmed that it is a promising material for evaluating AR in food safety.</p>

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Biogenic MnO2-Bi2O3 Nanocomposite-Modified Electrode Derived from Mentha spicata Extract for Electrochemical Sensing of Toxic Allura Red

  • 期刊论文

  • 发表日期：

    2025年11月3日

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  • Mythili Kumaresan Kavitha,
  • Radha Sankararajan,
  • Sreeja Balakrishnapillai Suseela,
  • Muthumeenakshi Kailasam

摘要

Allura Red (AR) is a red azo dye used in the health, beauty, pharmaceutical, and food industries. It is hazardous, causing an oxidative stress response and altering gene expression. As a result, it is critical to identify and quantify its concentration. In this work, bismuth oxide (Bi2O3), manganese dioxide (MnO2), and manganese dioxide–bismuth oxide (MnO2-Bi2O3) were synthesized using Mentha spicata leaf extract via a hydrothermal method. Subsequently, graphite electrodes (GE) modified with Bi2O3, MnO2, and the MnO2-Bi2O3 nanocomposite were developed as electrochemical sensors for detecting AR in food samples. The elemental composition, functional bond, crystal structure, morphology, and elemental mapping were confirmed using energy-dispersive x-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD), and field-emission scanning electron microscopy (FESEM), respectively. Differential pulse voltammetry (DPV) revealed that the anodic peak current demonstrated a linear relationship with AR concentrations between 1 μM and 5 μM. At a scan rate of 45 mV/s, the highest current response was achieved at the optimal potential range of −300 mV to 600 mV at pH = 11. A strong linear correlation between AR concentration and current was demonstrated by the electrochemical sensing probe, which exhibited sensitivity of 1.14 mA/μM/cm2, 1.27 mA/μM/cm2, and 1.28 mA/μM/cm2, and corresponding limits of detection (LOD) of 0.7455 μM, 0.4462 μM, and 0.4084 μM for Bi2O3-GE, MnO2-GE, and MnO2-Bi2O3-GE, respectively, with correlation coefficients (R2) of 0.9834, 0.994, and 0.9924, respectively. Analytical factors were also studied, including sensitivity, linearity, repeatability, reproducibility, and stability. The real sample analysis in food samples (soft drinks and tomato sauce) yielded a satisfactory recovery percentage between 95% and 105%. Therefore, the experimental investigation of the MnO2-Bi2O3 nanocomposite sensor confirmed that it is a promising material for evaluating AR in food safety.