Tea-assisted CeO 2 nanoparticles as electrode modifiers for electrochemical detection of nitrite in environmental water samples

Here, we report a tea-assisted synthesis of cerium oxide nanoparticles (CeO2 NPs) and their evaluation as a simple, noble-metal-free electrode modifier for electrochemical nitrite (NO2−) detection under neutral conditions. Oxygen-rich phytochemicals in Camellia sinensis extract promoted precursor formation with Ce3+ ions, followed by thermal conversion to crystalline CeO2 NPs. Spectroscopic, diffraction and microscopic analyses supported the formation of CeO2 NPs. When drop-cast onto a glassy carbon electrode, the CeO2 NP layer increased the electrochemically accessible interface and improved the apparent current-density response towards NO2− oxidation compared with bare GCE under identical conditions. This improvement is attributed to the beneficial contribution of the CeO2 NP-modified interface. Using current density at 1.10 V vs Ag/AgCl as the analytical signal, CeO2 NPs/GCE exhibited a linear response towards NO2− over 0.039–10 mM, with a sensitivity of 1.3255 µA cm−2 µM−1 and a calculated LOD of 2.80 µM. The sensor exhibited good cycling repeatability, electrode-to-electrode reproducibility, 28-day storage stability and selectivity against inorganic and electroactive interferents. Application to river and tap water samples yielded recoveries of 97.24–109.51%, with RSD values of 1.36–2.81%. These results support tea-derived CeO2 NPs/GCE as a stable and practical platform for NO2− determination in aqueous environmental matrices.