Calibration curve of the faradic current to the concentration of H2O2 in deoxygenated 0.01 M PBS buffer.

The dependence of catalysis current on the concentration of H2O2 is shown in Fig. 4. The linear range of H2O2 was from 2 µM to 24 µM (R2 = 0.991; p = 1.2 e-7) with a sensitivity of 3.0×10-4 A/M, and the detection limit was estimated to be 443 nM at the signal-to-noise ratio of 3. The apparent Michaelis-Menten constant (Km,app) was evaluated to be 15.4 µM derived from the Lineweaver-Burk equation. The value was much smaller than those of the HRP-SG/CNT/GC electrode (1.35 mM) [20], HRP/Tb-MWCNTs-modified graphite electrode (0.16 mM), MB-HRP/NME/MWCNTs/GC electrode (0.12 mM), and HRP/SGCCN film-modified GC electrode (23.85 mM) [21]. This result indicates that the immobilized HRP had a higher biological affinity to H2O2.