preparation of twin-brush zno (TB-zno) mesocrystals: The (TB-ZnO) mesocrystals were synthesized by a modified method according to our previous paper. Briefly, zinc nitrate hexahydrate (0.89 g) was dissolved in 30 mL of a solution of various gum arabic concentrations (0.01 ,0.05, 0.1, 0.2, 0.3 g/30 mL), followed by addition of HMT (0.42 g). The concentration of zinc nitrate was 0.1 M for the standard sample in the main text. However, the concentration of Zn was also varied as precursor for the synthesis of Zno mesocrystals. The gel-like mixture was placed in an autoclave for hydrothermal treatment at 80°C for 21 h . White Zn-containing precipitates were collected by washing several times and centrifugation. Finally, ZnO products were dried in an oven at 60°C prior to characterization.