Self-assembled glucose oxidase/graphene/gold ternary nanocomposites for direct electrochemistry and electrocatalysis

Graphene–gold nanoparticle nanocomposites (GR–AuNPs) were synthesized and used as a matrix for glucose oxidase (GOD) immobilization in glucose sensing. Using layer-by-layer (LBL) method, a multilayered GOD sensor was constructed by alternatively immobilizing GR–AuNPs and GOD on electrodes. The immobilized GOD displayed a couple of stable and well-defined redox peaks with an electron transfer rate constant of 3.25 s−1 and a formal potential of −0.452 V in 0.1 mol L−1 pH 7.0 phosphate buffer solution (PBS). The apparent Michaelis–Menten constant for glucose was 0.038 mmol L−1. This method allowed to detect glucose with a sensitivity of 3.844 μA mmol L−1 cm−2, a linear range from 0.02 to 2.26 mmol L−1, and a detection limit of 4.10 μmol L−1 (S/N = 3). The results indicated that the proposed graphene–gold nanoparticle nanocomposites were good platforms for enzyme immobilization, thus facilitating the direct electron transfer and biosensing application.