One-Pot Synthesis of Tannic Acid-Au Nanoparticles for the Colorimetric Determination of Hydrogen Peroxide and Glucose

This study introduces a novel one-pot method employing tannic acid (TA) to synthesize stable gold nanoparticles (TA-AuNPs), which are characterized using transmission electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. We apply these TA-AuNPs in a newly developed colorimetric assay for hydrogen peroxide (H₂O₂) detection that utilizes the oxidation of iodide (I^-) on TA-AuNPs, leading to a detectable yellow color change in the solution. The reaction kinetics are captured by the rate equation R = 0.217[KI]^0.61[H₂O₂]^0.69. The possible sensing mechanism was proposed through density functional theory calculations. At the optimum conditions, the proposed TA-AuNPs/I^- system demonstrated a linear relationship between H₂O₂ concentration and absorbance intensity (λ = 350 nm) and achieved a limit of detection (LOD) of 7.33 μM. Furthermore, we expand the utility of this approach to glucose detection by integrating glucose oxidase into the system, resulting in a LOD of 10.0 μM. Application of this method to actual urine samples yielded spiked recovery rates ranging from 96.6-102.0% and relative standard deviations between 3.00-8.34%, underscoring its efficacy and potential for real-world bioanalytical challenges.