Raman scattering properties of a protonic titanate HxTi2-x/4□x/4O4•H2O (□, vacancy; x=0.7) with lepidocrocite-type layered structure

Raman scattering spectroscopy is employed to characterize a layered titanate HxTi2-x/4 square O-x/4(4)center dot H2O (square: vacancy; x = 0.7) with lepidocrocite (gamma-FeOOH)-type layered structure. Nine Raman lines corresponding to (3A(g) + 3B(1g) + 3B(3g)) Raman-active modes expected from this orthorhombic structure (space group D-2h(25)-Immm) are recorded at 183, 270, 387, 449, 558, 658, 704, 803, and 908 cm(-1), which are assigned to Ti-O lattice vibrations within the two-dimensional (2D) lepidocrocite-type TiO6 octahedral host layers. These intrinsic Raman bands present a clear signature that can be used for probing the protonic titanate HxTi2-x/4 square O-x/4(4)center dot H2O and the 2D titanate nanosheets, as well as their corresponding derivates.