Ultralow Ru Single Atoms Confined in Cerium Oxide Nanoglues for Highly‐Sensitive and Robust H₂O₂‐Related Biocatalytic Diagnosis

Abstract Exploring highly efficient, portable, and robust biocatalysts is a great challenge in colorimetric biosensors. To overcome the challenging states in creating single‐atom biocatalysts, such as insufficient activity and stability, here, this work has engineered a unique CeO₂ support as nanoglue to tightly anchor the Ru single‐atom sites (CeO₂‐Ru) with strong electronic coupling for achieving highly sensitive and robust H₂O₂‐related biocatalytic diagnosis. The morphology and chemical/electronic structure analysis demonstrates that the Ru atoms are well‐dispersed on CeO₂ surface to form high‐density active sites. Benefiting from the unique structure, the prepared CeO₂‐Ru exhibits outstanding peroxidase (POD) like catalytic activity and selectivity to H₂O₂. Steady‐state kinetic study results show that the CeO₂‐Ru presents the highest V_max and turnover number than the state‐of‐the‐art POD‐like biocatalysts. Consequently, the CeO₂‐Ru discloses a high efficiency, good selectivity, and robust stability in the colorimetric detection of L‐cysteine, glucose, and uric acid. Notably, the limit of detection (LOD) can reach 0.176 × 10⁻³ m for the L‐cysteine, 0.095 × 10⁻³ m for the glucose, and 0.088 × 10⁻³ m for the uric acid via cascade reaction. This work suggests that the proposed unique CeO₂ nanoglue will offer a new path to create single‐atom noble metal biocatalysts and take a step closer to future biotherapeutic and biocatalytic applications.