Flower-like CeO<sub>2</sub>/CoO p–n Heterojuncted Nanocomposites with Enhanced Peroxidase-Mimicking Activity for <scp>l</scp>-Cysteine Sensing
Jiajia Lian, Pei Liu, Chunqiao Jin, Qingyun Liu, Xianxi Zhang, Xiao Zhang
Abstract
Designing an efficient peroxidase mimic and understanding its catalytic mechanism are of great importance for colorimetric biosensing. Herein, a series of CeO2/CoO nanocomposites (NCs) were prepared using a simple two-step method and applied as peroxidase mimics. Especially, the flower-like 0.10CeO2/CoO NCs (molar ratio of Ce3+/Co2+ salts of 0.10) exhibited much higher peroxidase-mimicking activity than the individual CoO nanoparticles and CeO2 nanoparticles (NPs) and other NCs. The 0.10CeO2/CoO NCs showed high affinity toward H2O2 (Km = 0.245 mM and Vmax = 14.78 × 10–8 M s–1) and TMB (Km = 0.113 mM and Vmax = 110.1 × 10–8 M s–1), thus exhibiting excellent fast response performance. In addition, the stability, repeatability, and durability performances have also been verified. As a result, a sensitive and selective colorimetric sensor was exploited on the basis of 0.10CeO2/CoO NCs for l-cysteine (Cys) detection, which exhibited a linear response to Cys ranging from 5 to 10 μM with a detection limit (LOD) of 3.71 μM. The superior catalytic performance of 0.10CeO2/CoO NCs can be attributed to the highly dispersed mesoporous structure, well-designed p–n heterojunction, and plentiful surface-active species. The possible catalytic mechanism was proposed according to the band gap structures of CeO2 and CoO as well as the free radical tests.