Synergistic catalysis of ionic liquid-modified ceria and silver-deposited activated carbon for the rapid and sensitive colorimetric detection of hydrogen peroxide

Abstract

Hydrogen peroxide (H₂O₂) is an important analyte that can indicate oxidative stress and cause DNA and protein damage. Natural peroxidases in the body have certain levels, and their abnormal concentrations can lead to the onset of oxidative stress and cancer. Hence, it is essential to monitor the level of H₂O₂ reliably and cost-effectively. The present study demonstrates the synthesis of silver and cerium oxide deposited on an activated carbon (Ag–CeO₂@AC) nanocomposite by applying a co-precipitation method. The nanocomposite was further functionalized with an ionic liquid (IL) to achieve better conductivity and deagglomeration. Various analytical techniques, such as XRD, EDS, XPS, FTIR spectroscopy, elemental mapping, HRTEM, and scanning electron microscopy (SEM), were used to confirm the synthesis of the nanocomposite. For the non-enzymatic colorimetric detection of H₂O₂, the IL-Ag-CeO₂@AC nanocomposite was employed as a peroxidase-like catalyst. Results showed the peroxidase-like activity of IL-Ag-CeO₂@AC in the presence of H₂O₂ and the chromogenic substrate tetramethylbenzidine (TMB). TMB was oxidized to oxTMB (blue-green color) with the maximum absorption at 652 nm in the presence of the analyte (H₂O₂). The catalytic activity of the proposed sensor was enhanced by optimizing various parameters, namely, the amount of the synthesized nanocomposite, time, pH, and TMB concentration. Once the experimental conditions were determined, the key analytical parameters of the proposed sensor were calculated. The linear range was found to be 10–190 µM, with limits of quantification and detection (LOQ and LOD) of 0.77 µM and 0.232 µM, respectively, and a regression coefficient (R²) value of 0.996. In addition to its exceptional sensitivity, the sensor showed excellent selectivity for the detection of H₂O₂ under the influence of different possible interferents. The developed approach was utilized to determine H₂O₂ in real samples and demonstrated good feasibility and reproducibility.