Colorimetric Method Based on CeO2/CoOOH Nanozyme for Rapid Detection of Ascorbic Acid in Fruits

In this study, cerium dioxide-modified cobalt oxyhydroxide (CeO2/CoOOH) nanomaterial was synthesized by a liquid-phase precipitation method. CeO2/CoOOH showed good oxidase-like activity toward 3,3’,5,5’-tetramethylbenzidine (TMB), and could directly oxidize TMB to ox-TMB, which presented a clear blue color. Reversely, ascorbic acid (AA) could reduce ox-TMB to TMB, leading to a decrease in the absorbance of ox-TMB at 652 nm and a fading of the blue color. Based on this phenomenon, a new colorimetric sensor for AA detection was developed. The sensor exhibited a highly sensitive response to AA with a limit of detection (LOD) of 2.73 μg/mL and a wide detection range of 5-100 μg/mL and could be successfully applied for rapid detection of AA in oranges and apples.