*2.1.2 Hydrothermal*

Hydrothermal is the most common chemical route to nanostructures and particularly nanoparticles metal oxide synthesis. Related to the sol-gel method, it begins with the preparation of a precursor. However, the crystallization phase occurs throughout a hydrothermal process instead of a high-temperature annealing treatment. Final nanoparticles are formed after washing, filtering, and final drying processes.
