With the goal of controlling the oxidation state of cerium ions in Ce-doped Y3Al5O12 nanocrystals (YAG:Ce), different gases (Ar/H2, O2, Ar) were bubbled inside the solution of precursors and solvent prior to the solvothermal synthesis. As assessed by X-ray absorption spectroscopy, this protocol modifies the Ce3+ : Ce4+ ratio in YAG:Ce nanocrystals, although it does not allow complete prevention of the Ce3+ → Ce4+ oxidation. (365)