suspension was placed under ultrasound for 5 min; then, a drop of the suspension was placed on a carbon microgrid (300 mesh) and dried at 60 °c for 20 min. The images were acquired on a transmission electron microscope ZEISS CEM 902, employing an accelerating voltage of 80 kv. This analysis was carried out in the Brazilian Nanotechnology National Laboratory (LNNano) located in the Brazilian Center for Research in Energy and Materials (CNPEM).