Synthesis of AZP@GO-Cs Composite

To prepare AZP (zinc ammonium phosphate), a 0.3 M solution of Zn(NO₃)₂ (zinc nitrate) was added to a 0.3 M solution of (NH₄)₂HPO₄ (diammonium phosphate) at room temperature (RT). The pH of the solution was adjusted to about nine by adding NH₄OH 28%, and the reaction was allowed to proceed for 12 h at RT under vigorous stirring. Then, it was left for another 24 h, then the illiquid material was dried in a vacuum oven^{23 (link)}. After that, 0.50 g of GO was dispersed in DW using an ultrasonic bath for 20 min and added dropwise to a clear solution containing 5 g of Cs in 50 ml of 10% AA, and mixed slowly for 12 h to obtain the GO-Cs coating material. In the end, 5 g of AZP was mixed with 500 mg of GO-Cs, and after that, the AZP@GO-Cs were dried at RT.