*2.2.1 Hydrothermal synthesis*

Hydrothermal or solvothermal synthesis (if water is the solvent) is a synthesis method in which the precursors (dissolved or dispersed in water) are placed in an autoclave where the reaction takes place at high temperature and pressure [14]. Hydrothermal allows the synthesis of MO-NPs from a wide variety in shape, size, structure, and composition, provided that key-factors such as temperature, pressure, pH, concentration of reactants are well-controlled [15–20].
