2.3.1. X-ray Diffraction (XRD)

X-ray diffraction analysis was carried out by means of a 2-circle diffractometer XRD 3003 T/T (Seifert-FPM, Freiberg, Germany) with Cu-Kα radiation at 30 mA and 40 kV from 2θ = 1◦ to 16◦ using 0.05◦ as the step length.

## 2.3.2. Dynamic Light Scattering Analysis (DLS)

The particle size and particle distribution of the silica powders was determined with a dynamic light scattering analyzer (Dyna Pro-nanostar, Wyatt instruments, Santa Barbara, CA, USA) from 0.2 to 2500 nm, using a laser wave length of 785 nm. Measurements are performed at 25 ◦C with dispersions of silica particles in ethanol. The DLS experiments were carried out for three samples. At least 25 scans per sample were performed.
