Fig. 9. (a) Cyclic voltammogram obtained at GO/ZnO/CPE in the (a) absence and presence of (b) 1.5 mM, (c) 3 mM, and (d) 4.5 mM H₂O₂. The inset is the corresponding calibration curve between the current response and concentration of H₂O₂. (b) Amperometric response of different electrodes against H₂O₂ GO–ZnO and use of the electrode material for the construction of a H₂O₂ sensor [this figure has been reproduced from ref. 150 with permission from Springer, Copyright 2016].