RESUMO
In this study, we have fabricated a dual-signal sensor for H2O2 determination based on 2D Cu-MOFs decorated with Ag NPs. A novel polydopamine (PDA) reduction method was utilized to reduce [Ag(NH3)2]+ to highly dispersed Ag NPs in situ without other reductive agents, and Cu-MOF@PDA-Ag was obtained. For the electrochemical sensor, the Cu-MOF@PDA-Ag modified electrode exhibits outstanding electrocatalytic properties toward H2O2 reduction with a high sensitivity of 103.7 µA mM-1 cm-2, a wide linear range from 1 µM to 35 mM and a low detection limit of 2.3 µM (S/N = 3). Moreover, the proposed sensor shows good feasibility in an orange juice sample. For the colorimetric sensor, colorless 3,3',5,5'-tetramethylbenzidine (TMB) can be oxidized by the Cu-MOF@PDA-Ag composite in the presence of H2O2. A Cu-MOF@PDA-Ag catalysis-based colorimetric platform is further established for the quantitative analysis of H2O2 ranging from 0 to 1 mM with a lower detection limit of 0.5 nM. Importantly, such a dual-signal method for the detection of H2O2 could potentially have wide practical applications.
RESUMO
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.