Flower-like CeO₂/CoO p–n Heterojuncted Nanocomposites with Enhanced Peroxidase-Mimicking Activity for l-Cysteine Sensing

Abstract

Designing an efficient peroxidase mimic and understanding its catalytic mechanism are of great importance for colorimetric biosensing. Herein, a series of CeO 2 /CoO nanocomposites (NCs) were prepared using a simple two-step method and applied as peroxidase mimics. Especially, the flowerlike 0.10CeO 2 /CoO NCs (molar ratio of Ce 3+ /Co 2+ salts of 0.10) exhibited much higher peroxidase-mimicking activity than the individual CoO nanoparticles and CeO 2 nanoparticles (NPs) and other NCs. The 0.10CeO 2 /CoO NCs showed high affinity toward H 2 O 2 (K m = 0.245 mM and V max = 14.78 × 10 −8 M s −1 ) and TMB (K m = 0.113 mM and V max = 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 0.10CeO 2 /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 0.10CeO 2 /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 CeO 2 and CoO as well as the free radical tests.

Mechanism and Application of Surface-Charged Ferrite Nanozyme-Based Biosensor toward Colorimetric Detection of l-Cysteine

“…The LOD of the l -Cys is calculated to be 0.119 μM based on the 3σ/slope role, which is at a relatively low level compared with previous colorimetric detection of l -Cys by nanozymes (Table ). ,− …”

“…47 Therefore, the accurate sensing of L-Cys under physiological conditions is significant to evaluate human health. Previously, a variety of nanozymes (reduced graphene oxide derivative, 37 Fe 3 O 4 magnetic nanoparticles, 47 nickel oxide nanoflowers, 48 CuMnO 2 nanoflakes, 49 cobalt sulfide nano-sheets, 50 vanadium tetrasulfide, 51 CeO 2 /CoO, 52 MoS 2 −Au@ Pt, 53 and Cu@Au(Ag)/Pt 54 ) have been exploited to detect the L-Cys concentration. However, the limit of detection (LOD) or the linear range of most nanozymes is generally at relatively high levels.…”

Fluoro-Substituted Covalent Organic Framework Particles Anchored on TiO2 Nanotube Arrays for Photoelectrochemical Determination of Dopamine

“…Thus, the E VB, NHE of TiO 2 , H-COF, and F-COF are 2.99, 2.14, and 1.85 eV, respectively. Taking into account the VB positions and the measured band gaps, the conduction band potentials ( E CB, NHE ) of TiO 2 , H-COF, and F-COF are calculated to be −0.31, −0.40, and −0.56 eV, respectively, based on the formula of E CB = E VB – E g . The calculated band-structure diagrams of TiO 2 , H-COF, and F-COF are shown in Figure d.…”

“…Taking into account the VB positions and the measured band gaps, the conduction band potentials (E CB, NHE ) of TiO 2 , H-COF, and F-COF are calculated to be −0.31, −0.40, and −0.56 eV, respectively, based on the formula of E CB = E VB − E g . 61 The calculated band-structure diagrams of TiO 2 , H-COF, and F-COF are shown in Figure 5d. The VB of H-COF and F-COF is located between the CB and VB of TiO 2 NTA, and the CB of H-COF and F-COF is more negative than that of TiO 2 , which is ideal for the formation of the staggered heterojunction between TiO 2 and COFs.…”

Colorimetric determination of cysteine based on Au@Pt nanoparticles as oxidase mimetics with enhanced selectivity

“…This redox process requires the participation of an appropriate nanozyme as the catalyst. Introducing analytes such as Cys into the colorimetric solution will inhibit this process and thus cause a concentrationdependent absorbance decrease, which can be used for the quantification of analytes [17][18][19].…”