Polyoxometalate functionalizing CeO2 hollow nanospheres as enhanced oxidase mimics for ascorbic acid colorimetric sensing

Phosphotungstic acid covered with CeO2 hollow nanospheres (CeO2@PTA HNSs) has been successfully prepared by a simple method, serving as highly efficient nanozymes for ascorbic acid (AA) colorimetric sensing. In virtue of the unique hollow nanostructures, oxide defects and synergic effects of CeO2 and PTA, the proposed CeO2@PTA HNSs present remarkable intrinsic oxidase-like activity and help capture electrons from 3,3',5,5'-tetramethylbenzidine (TMB). Due to the reducibility of AA, a promising colorimetric sensing platform based on CeO2@PTA HNSs has been constructed for quantitative analysis of AA. The present colorimetric detection exhibits a low limit of detection, good selectivity and stability, as well as reliability in orange juice and milk. This work provides a simple surface defect engineering to prepare high-performance oxidase mimics in the application of colorimetric biosensing.