Enzymatic glucose biosensor based on multiwalled carbon nanotubes-zinc oxide composite

An amperometric glucose biosensor based on multiwalled carbon nanotubes (MWCNT)-zinc oxide (ZnO) composite modified glassy carbon electrode (GCE) was demonstrated. ZnO micro sponges were electrochemically grown on MWCNT modified GCE at room temperature. GOx immobilized at MWCNT/ZnO composite modified GCE showed a pair of stable and well-defined reversible redox peaks, with a formal potential (E^0') of -0.426 V, characteristic features of active redox couple of GOx. Fast electron transfer kinetics has occurred at the composite film, which was revealed from the high electron transfer rate constant (k_s) value of 1.66 s^-1 and smaller peak-to-peak separation (ΔEp) value of 48 mV. The resulting biosensor shows good electrocatalytic activity towards glucose in short time (>5 s) at 0.32 V in the presence of ferrocene monocarboxilic acid (FMCA), which mediates the glucose oxidation. The fabricated biosensor showed linear range of 0.2-27.2 mM with a detection limit of 20 μM and a sensitivity of 4.18 μA/ mM. Moreover, good recovery results (~98 %) were achieved for spiked glucose concentrations in urine samples. In addition, the biosensor exhibited acceptable reproducibility, repeatability, good selectivity and storage stability.