The electrochemical reversibility of the redox probe over time in a mediated-electron-transfer system is of paramount importance for practical applications. Therefore, to assess the long-term stability of the 10%Fc12-Br/MO electrode a continuous cyclic voltammetry measurement was conducted (as shown in Figure ). During the 1 st redox cycle, the voltammogram adopts a quasi-reversible shape and the ratio between anodic peak and cathodic peak (ipa/ipc) is approx. 1. However, as the redox cycling continued, the shape of the voltammogram began to change. At the 100 th cycle, the magnitude of both the anodic and cathodic current decreased dramatically, although the system was still quasireversible at 100 th cycle, and the value of the peaks separation (Epa-Epc) did not change. The magnitude of the currents kept decreasing as the redox cycling proceeded. At the 200 th cycle, the shape of the voltammogram was further compressed compared to the 1 st cycle. It is also noteworthy that the Fc12-Br lost the reversibility, leading to the disappearance of the cathodic peak.