Amperometric enzyme-free glucose sensor based on the use of a reduced graphene oxide paste electrode modified with electrodeposited cobalt oxide nanoparticles

The authors describe a non-enzymatic amperometric sensor for glucose that was prepared by electrodeposition of cobalt oxide nanoparticles on a graphene paste that is readily obtained by mixing reduced graphene oxide (r-GO) nanosheets and mineral oil in a mortar. An electrode was prepared and characterized by cyclic voltammetry and electrochemical impedance spectroscopy. Cobalt oxide nanoparticles were electrochemically deposited on the electrode, and their morphology was characterized by field emission scanning electron microscopy. Cyclic voltammetric and chronoamperometric studies showed the modified electrode to display electrocatalytic activity toward the direct oxidation of glucose, best at a working potential of 0.45 V (vs. SCE) in 0.1 M NaOH solution. The sensor exhibits a linear response in the 40 to 4000 μM glucose concentration range, has a detection limit as low as 1.4 μM (at an S/N ratio of 3), and a sensitivity of 1.21 μA∙μM−1∙cm−2. The electrode was successfully applied to the determination of glucose in (spiked) human serum where it showed recoveries between 97.2 and 103.4 %.