2.4.1. Preparation of Spray Dried Microparticles

In order to obtain porous silica microparticles, a suspension of fumed silica nanoparticles (5% *w*/*w*) was sonicated overnight to allow effective hydration and separation of the silica nanoparticles prior to spray drying with a Büchi Mini Spray Dryer B290 apparatus (Büchi, Flawil, Switzerland). Spray drying was performed under the following conditions: inlet temperature 160 ◦C, outlet temperature 90 ◦C, aspirator setting 100, pump set at 20%, and product flow rate 6 mL/min. Fumed silica nanoparticles were successfully spray dried to form porous silica microparticles (80% yield).
