Direct electron transfer of glucose oxidase and biosensing for glucose based on PDDA-capped gold nanoparticle modified graphene/multi-walled carbon nanotubes electrode

• AuNPs/G/MWCNTs nanostructure was prepared.
• Glucose oxidase was immobilized onto the structure via electrostatic attraction.
• The direct electron transfer was achieved between the enzyme and the electrode.
• The glucose biosensor fabricated exhibited satisfactory analytical performance.

In this work, poly (diallyldimethylammonium chloride) (PDDA)-capped gold nanoparticles (AuNPs) functionalized graphene (G)/multi-walled carbon nanotubes (MWCNTs) nanocomposites were fabricated. Based on the electrostatic attraction, the G/MWCNTs hybrid material can be decorated with AuNPs uniformly and densely. The new hierarchical nanostructure can provide a larger surface area and a more favorable microenvironment for electron transfer. The AuNPs/G/MWCNTs nanocomposite was used as a novel immobilization platform for glucose oxidase (GOD). Direct electron transfer (DET) was achieved between GOD and the electrode. Field emission scanning electron microscopy (FESEM), UV–vis spectroscopy and cyclic voltammetry (CV) were used to characterize the electrochemical biosensor. The glucose biosensor fabricated based on GOD electrode modified with AuNPs/G/MWCNTs demonstrated satisfactory analytical performance with high sensitivity (29.72 mA M−1 cm−2) and low limit of detection (4.8 µM). The heterogeneous electron transfer rate constant (ΚS) and the apparent Michaelis–Menten constant (Km) of GOD were calculated to be 11.18 s−1 and 2.09 mM, respectively. With satisfactory selectivity, reproducibility, and stability, the nanostructure we proposed offered an alternative for electrode fabricating and glucose biosensing.