Tailored Fabrication of Defect-Rich Ion Implanted CeO2-xNanoflakes for Electrochemical Sensing of H2O2

As an alternative to H2O2enzymatic biosensing devices, non-enzymatic CeO2-based biosensors have shown improved sensibility, robustness, and shelf lives. The redox capability in CeO2and rapid switching between its oxidation states facilitate the formation of structural vacancy defects that serve as active sites. This work reports a novel approach for synthesis of defect-rich CeO2-x-based nanoflakes using a controllable electrochemical-based deposition at low temperatures (45°−65 °C) followed by low-energy ion implantation. Among the nanoflakes, Mo-implanted CeO2-xexhibited outstanding sensitivity of 4.96 × 10−5 A·mM−1cm−2within the linear range of 0.05–10 mM. Moreover, the ion-implanted samples yielded high sensing stability and electronic conductivity. The former was achieved through the multi-valence charge transfer between Ce and the implanted ions that caused the reduction of Gibbs free energies required for the formation/retention of the defects. The latter was due to the narrowing of the electronic bandgap of CeO2-xby creation of defect-induced midgap states.