MoxW1−xO₃·0.33H₂O Solid Solutions with Tunable Band Gaps

A series of Mo x W 1− x O 3 ·0.33H 2 O ( x = 0, 0.25, 0.50, 0.75) micro/nanostructures and α-MoO 3 nanobelts have been prepared by a facile hydrothermal treatment method starting from aqueous peroxo-polytungstic acid and peroxo-molybdic acid solutions. The WO 3 ·0.33H 2 O lattice can be substituted with up to 75% Mo without structural alterations of the orthorhombic host structure. With the increase of the Mo content ( x ) from 0 to 0.75, the band gap of the as-prepared Mo x W 1− x O 3 ·0.33H 2 O micro/nanostructures is narrowed from 3.25 to 2.77 eV. The increased M 5+ (M = Mo and W) fraction and thus enhanced intervalency-transition are responsible for the narrowing of the band gap.