Photocatalysis measurement Methylene blue (MB) was the model organic pollutant to examine the ZnO samples photocatalytic activity. These properties were evaluated based on the rate and degree of degradation of MB over time under the influence of UV radiation at room temperature. The decomposition processes were monitored by UV-Vis measurements on the Hitachi U-2910 spectrophotometer. A standard 3.5 mL quartz cell (Hellma) with a 10 mm path length and transparent on all four sides was used.Absorption spectra were recorded at intervals of 20 minutes, with the first 40 minutes the degradation of the dye took place without the use of UV light (6 W, 365 nm). The typical procedure consisted of the immersion of the 10 mm × 10 mm substrate with a layer of porous ZnO in 10.5 ml MB solution with constant stirring. Work station diagram for photocatalysis is shown in Figure in the Supplementary Information. Photocatalytic activity was assessed by measuring and analyzing UV-Vis spectra after each 20 minutes up to 240 minutes total degradation time. The percentage of MB degradation was calculated as follows: