*2.3. Preparation of AGO/SPEEK Films*

SPEEK (DS 79.8%) and AGO/SPEEK films were prepared by the method proposed by He et al. [9,12,15]. SPEEK was dissolved in DMF to form a 10% (*w/w*) mixed solution under magnetic stirring. Then, AGO (0.1%, 0.5%, and 0.9%) was added to react with SPEEK for 24 h at 60 ◦C in order to obtain a casting solution. The casting solution was defoamed at room temperature under vacuum. Subsequently, it was cast on a clean glass plate, and its thickness was controlled at 40 μm using an adjustable scraper. The casted glass plate was placed horizontally into a vacuum oven at 60 ◦C and dried for 24 h to completely remove the solvent. Finally, the dried film was peeled off from the glass plate for further tests.
