Posteriorly, the NPsCu-GO/GCE were put in
0.1 mol L1 NaOH solution and scanned repetitively for 30 cycles
under potential range from 0.5 to 0.3 V at 100 mV s1 for surface
passivation [27]. For Comparison, an electrode was modified only
with GO (GO/GCE) and another one was modified under the same
conditions of the NPsCu-GO/GCE, however, a solution 0.1 mol L1
H2SO4 without CuSO45H2O was used (RGO/GCE).