Renishaw InVia confocal Raman microscope with a 532 nm excitation laser. The laser power was kept at 100 µW to prevent the degradation of samples. Three different spots were investigated to ensure the samples homogeneity. The particle size distribution was characterized using a laser diffraction particle size analyzer (Mastersizer 3000, Malvern) to measure the size of non-spherical particles via dynamic light scattering (DLS). A mixture of isopropanol and deionized water (1:1 volumetric ratio) was used as a dispersant, sonication was employed to ensure dispersion of the powder and to avoid agglomeration prior to the measurement.