(a) Diffuse reflectance spectra (DRS) and (inset) plot of transferred Kubelka-Munch versus energy of the light absorbed for the ZnO nanorod arrays and ZnO@TiO2 nanorod arrays. (b) Comparison of photocatalytic decomposition rates of MB with different catalysts. (c) Cyclic photodegradation of MB using ZnO@TiO2 nanorod arrays. The same ZnO@TiO2 nanorod arrays for degradation of MB are tested up to 15 cycles. The photocatalytic time is 180 min for each cycle. (d) Photogenerated electron transfer process in the ZnO@TiO2 nanorod under UV illumination. The scale bars represent the standard deviations of three replicated samples.