*3.4. Photocatalytic Dye Degradation*

The photocatalytic activity of the as-prepared samples was evaluated toward RB degradation. 100 ppm of RB dye (4,5,6,7-tetrachloro-2 ,4 ,5 ,7 -tetraiodofluorescein, 973.67 g/mol) was employed, while the reaction conditions were 1 g/L, 20 ◦C, 6.5 for catalyst concentration, reaction temperature, and pH (without adjustment), respectively. UV-LED (25 W, 365 nm, NVMUR020A, NICHIA, Tokushima, Japan) was used as the light source. First, the catalyst was suspended in 150 mL of dye aqueous solution inside irradiation made of Pyrex glass via ultrasonication and stirred in the dark for 1h to establish the adsorption– desorption equilibrium. Then the sample was irradiated with UV-LED for another 1 h while the concentration of the dye was monitored via UV-Vis. spectrophotometer (Perkin

Elmer, Lamda-40, Waltham, MA, USA). Dye samples were withdrawn, and catalysts were separated via centrifugation prior to absorption measurement.
