Nanoporous Cu2O nanotube/nanorod array electrodes for non-enzymatic glucose sensing with high sensitivity and very low detection limit

This study compares the non-enzymatic glucose sensing performance by Cu2O nanorods/nanotubes grown using electrochemically anodized Cu foam and Cu plates to form binder free one-dimensional Cu(OH)2 nanostructures which were subsequently annealed at higher temperatures. Resulting Cu2O nanorods/nanotubes had diameters between 100 and 200 nm and lengths in excess of 10 μm. The surface morphology and structure of these thin films studied using scanning electron microscopy, X-ray diffraction and energy dispersive X-ray spectroscopy showed that the copper foam based Cu2O structures consisted of nanotubes/nanorods distributed over entire 3-dimensional space containing dense nano-pores of size ∼20 nm on outer surfaces. Cu plate based nanorods consisted of grooved macaroni type surface morphologies. Non-enzymatic glucose sensing made using chronoamperometric and cyclic voltammetric measurements showed that the Cu2O/Cu foam electrodes had a high sensitivity of 5792.7 μA mM−1 cm−2, a very low detection limit of 15 nM (S/N = 3), multi-linear detection ranges of 15 nM–0.1 μM and 575–4098.9 μM with a faster response time of less than 1 s. Cu plate based nanorods showed a sensitivity of 141.9 μA mM−1 cm−2, with a lower detection limit of 510 nM (S/N = 3). The significantly high sensitivity of Cu2O/Cu foam electrodes is attributed to the availability of increased amount of active sites due to the large effective surface area provided by Cu2O nanorods/nanotubes. The study also demonstrates the influence of the substrate on surface morphology of the nanorods/nanotubes. These Cu foam based Cu2O electrodes provide a promising platform for non-enzymatic glucose detection with high specificity and reproducibility.