A multi-component Cu2O@FePO4 core-cage structure to jointly promote fast electron transfer toward the highly sensitive in situ detection of nitric oxide.

Electrochemical sensors actually involve an electrocatalytic process in efficient and selective energy conversion. In this work, we use different components to innovatively produce a core@cage material, in which the outer cage, iron phosphate, offers a high electrocatalytic ability to electrochemically oxidize NO, while the inner material, cuprous oxide, could absorb the intermediary HO- ions to kinetically promote NO oxidation for fast electron transfer, resulting in a strong synergistic effect. The unique core@cage structure also increases the active surface area and provides plenty of channels via the porous cage for significantly enhanced mass transport. The as-prepared core@cage NO sensor shows a high sensitivity of 326.09 μA cm-2 μM-1, which is the highest among the reported non-noble metal-based NO biosensors based on the electrooxidation scheme. A free-standing flexible NO sensor was further fabricated with the material for the in situ detection of NO released from cancer cells, demonstrating a low detection limit (0.45 nM) and a fast response time (0.8 s). This work holds great promise for its practical applications in the diagnosis or research of complicated biological processes, especially in real-time in situ detection approaches.