Free-standing nickel oxide nanoflake arrays: Synthesis and application for highly sensitive non-enzymatic glucose sensors

We report a seed-mediated hydrothermal growth of free-standing nickel hydroxide [Ni(OH)₂] and nickel oxide (NiO) nanoflake arrays and their implementation as electrodes for non-enzymatic glucose sensors. Ni(OH) ₂ nanoflakes were converted into porous NiO nanoflakes upon thermal annealing in air at temperatures of 300 °C or above. NiO nanoflake-arrayed sensors achieve an excellent glucose sensitivity of ∼8500 μA cm ^-2 mM^-1 and a low detection limit of 1.2 μM glucose at an applied bias of 0.5 V vs. Ag/AgCl. The fabrication of the nanoflake electrode avoids the use of polymer binders representing additional advantage over the conventional powder based glucose sensors. Furthermore, they show good specificity to glucose in the presence of ascorbic acid, d-lactose and d-fructose.