“…Different from many other oxide nanoparticles in which only one broad band was observed, the broad profile for both of undoped GdPO 4 ·nH 2 O samples consist of three bands at 3223, 3469, and 3533 cm −1 . The observation of the bands at 3223 and 3533 cm −1 confirms the existence of lattice water [38].…”