Schematic illustrations, TEM, cyclic voltammograms, and SEM images. (a) Schematic illustration of preparation of TiO2 nanoparticles and TiO2@DTMBi core-shell nanospheres. (b) TEM image of TiO2 nanoparticles; the insert is size distribution. (c) TEM images of TiO2@DTMBi core-shell nanospheres; the inserts are two magnified spheres. (d) Cyclic voltammograms of electrodes (1), T0 and (2) T1. SEM images of the electrode surface (e), T0 and (f) T1.