The SSA of the particles was measured by 5-point nitrogen adsorption (BET: Micromeritics, Gemini 2350) after degassing the powder at 150◦C for 2 h in nitrogen.
The dBET was calculated from the measured SSA and the density of ZnO (ρZnO = 5.61∗103 kg/m3): dBET = 6/(SSA ∗ ρZnO).
The powder crystallinity was measured by XRD (XRD: Bruker, AXS D8 Advance, 40 kV, 40 mA) at 2θ (Cu-Kα) = 20–70◦, step = 0.02◦ and scan speed = 0.24◦/min.
The dXRD was calculated from the full width at half maximum (FWHM) of the (100) peak using Scherrer’s equation (Klug & Alexander, 1974):