CeO2/CoO@N-doped hollow carbon microspheres with improved peroxidase-like activity for the determination of quercetin.

Nanozymes, as substitutes for natural enzymes, have been used to construct some fast cheap sensing platforms by virtue of the high catalytic activity. Herein, we firstly study the peroxidase-like activity of CeO/CoO@N-doped hollow carbon microspheres as nanozymes. In the presence of HO, CeO/CoO@NCH exhibits high peroxidase-like activity evaluated by the catalytic oxidation of the chromogenic substrate, 3,3',5,5'-tetramethylbenzidine (TMB) into a blue oxTMB visually in 1 min. The larger surface area, pore-like structure, and oxygen vacancies contribute to the enhanced peroxidase-like activity of CeO/CoO@NCH. The active species •O is detected during the catalytic process. Thus, based on the excellent peroxidase-like activity of CeO/CoO@NCH, a facile and effective biosensor is fabricated for sensitive and selective determination of HO and quercetin, respectively. CeO/CoO@NCH shows high affinity towards HO (K = 4.001 mM) and TMB (K = 0.086 mM). The detection limit of HO and quercetin is as low as 0.086 mM and 1.19 μM (3σ/slope), respectively. This work remarkably extends the utilization of CeO/CoO@NCH in designing a colorimetric sensing platform related to biosensing, food, and environmental monitoring. A fast colorimetric sensing platform for quercetin based on the excellent peroxidase-like activity of CeO/CoO@NCH.