Fig. 11. Structural characterization of Cu–Co/rGO nanostructures on a pencil graphite electrode (PGE). (A) SEM images of Cu/PGE (a–c), Cu–Co/PGE (d and e), and Cu–Co/rGO/PGE (f–h). White arrows indicate interspaces with voids, and yellow solid and dotted lines indicate the primary and secondary trunks of dendrites and rGO, respectively. (B) Glucose-sensing performance of the Cu–Co/rGO-PGE-modified electrode. (a) Amperometric response after the successive addition of glucose at 0.4 V vs. Ag/AgCl. (Inset) Amperometric response of Cu–Co/rGO/PGE toward low glucose concentration ranges between 1–100 μM. (C) Calibration plot of Cu–Co/rGO/PGE amperometric responses with respect to glucose concentration. [Reprinted with permission from ref. 277, K. J. Babu, S. Sheet, Y. S. Lee and G. G. Kumar, Three-Dimensional Dendrite Cu–Co/Reduced Graphene Oxide Architectures on a Disposable Pencil Graphite Electrode as an Electrochemical Sensor for Nonenzymatic Glucose Detection, ACS Sustainable Chem. Eng., 2018, 6, 1909–1918. Copyright© American Chemical Society.].