Os-Ce nanoparticles with specific enzyme-like activity for total antioxidant capacity detection in beverages and...

This study successfully synthesized osmium‑cerium nanozymes (OsCe NPs) with excellent peroxidase (POD)-like activity using a mild one-pot aqueous method to determine the total antioxidant capacity (TAC) of common substances in daily life. The nanozymes efficiently catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) substrates in the presence of H₂O₂ at an extremely low dosage (0.5 μg·mL^-1) within a short time, producing distinct blue and blue-green color changes, respectively. Based on the chromogenic reactions and by integrating absorbance (OD) with RGB data, a dual-mode colorimetric sensing platform was constructed for the quantitative detection of ascorbic acid (AA). Experimental results showed that the platform achieved detection ranges of 5-70 μM and 60-120 μM for AA using the TMB and ABTS systems, respectively, with detection limits as low as 17.5 nM and 25.5 nM, which outperformed some previously reported methods. The dual-substrate complementarity effectively avoids interference from common metal ions, demonstrating excellent selectivity. When applied to determine TAC in real samples such as beverages and cosmetics, the results were highly consistent with those from commercial kits, with shorter detection times. Furthermore, OsCe NPs exhibit only prominent POD-like activity, eliminating interference from dissolved oxygen and enhancing detection stability. This study provides a new strategy for synthesizing efficient nanozymes and develops a simple, rapid, and instrument-free TAC detection method, helping consumers scientifically evaluate product antioxidant value and avoid marketing pitfalls.