CeO2 nanosheets with prominent peroxidase-mimicking activity for the colorimetric sensing of H2O2, glucose, and ascorbic acid

The peroxidase-mimicking activity of nanozymes has been extensively utilized in the colorimetric turn-on detection of hydrogen peroxide (H 2 O 2 ) and compounds that produce H 2 O 2 as an intermediate, facilitating the identification of small biological molecules through oxidative chromogenic reactions. In this report, the peroxidase-mimic activity of Cerium Oxide nanosheets (CeO 2 NSs) as a nanozyme has been thoroughly investigated. CeO 2 NSs were synthesized using a simple, cost-effective one-step sugar-blowing method and characterized by various analytical techniques. CeO 2 NSs catalyze to oxidize the peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) into Ox-TMB in the presence of H 2 O 2 , producing a blue color ( turn-on ). The CeO 2 NSs-based colorimetric assay was successfully used to detect H 2 O 2 and glucose. The linear detection ranges for turn-on sensing were found to be 11 µM–455 µM for H 2 O 2 , and 5.43 µM–86.95 µM and 86.95 µM–347.82 µM for glucose. The limits of detection (LOD) were calculated as 1.613 μM for H 2 O 2 and 1.068 μM for glucose. Blue-colored Ox-TMB turns colorless with the addition of ascorbic acid; using this colorimetric turn-off mechanism, CeO 2 NSs were also able to detect ascorbic acid within the range of 2.2–21.73 μM, with a LOD of 0.058 μM. Satisfactory recovery rates were observed in fruit samples, showing the effectiveness of the sensor in practical applications.