Structure effect on graphene-modified enzyme electrode glucose sensors

• This paper studied the structure effect on glucose enzyme electrodes that were modified by reduced graphene oxide (rGO).
• At low oxygen concentration, rGO helps to induce the direct electron transfer (DET) on the electrode.
• At higher oxygen concentration, the reduction of H2O2 occurred instead of DET on the surface of the electrode.
• An increase in the number of oxygen functional groups could improve the affinity and sensitivity of the biosensors.

Using structural characterizations and electrochemical measurements, we explored and investigated the effect of the structure of enzyme electrodes with glucose oxidase (GOD) that were modified by reduced graphene oxide (rGO) sheets . The rGO sheets with different defect density, layers, and oxygen concentrations were chosen to modify the enzyme electrode, and all the modified enzyme electrodes exhibited excellent electrocatalytic activities and performances towards glucose. The abundant defects in rGO induce easy absorption of GOD. At a low oxygen concentration, rGO sheets help to induce the direct electron transfer (DET) on the rGO-modified electrode, and at a higher oxygen concentration, the reduction of H2O2 occurred instead of DET on the surface of the rGO-modified electrode. When rGO modified the enzyme electrode under the working model of H2O2 reduction, an increase in the number of the oxygen functional groups could lead to an increase in the absorption of GOD, resulting in the improvement of the affinity and sensitivity of the biosensor. The rGO-modified enzyme electrode can provide faster response, higher sensitivity, and better affinity by optimizing and controlling the structure of graphene and its derivatives.