Crystal phase- and morphology-controlled synthesis of MoO3 materials

The crystal phase and morphology of MoO3 materials were precisely tuned under suitable synthetic conditions and mutual transformation of h-MoO3 and alpha-MoO3 was achieved via a facile hydrothermal method for the first time. The h-MoO3 microrods with a diameter of 0.5-1.6 mu m and length of 2.2-6.1 mu m were fabricated with the assistance of NaNO3 using alpha-MoO3 particles as the precursor. The transformation of h-MoO3 microrods to alpha-MoO3 nanobelts with a diameter of 150-430 nm and length of 2.1-14.5 mu m occurred through hydrothermal techniques at higher temperature. Systematic studies of synthetic parameters revealed that the hexagonal h-MoO3 microrods formed at higher concentration of NaNO3, while h-MoO3 microrods vanished at higher temperature with prolonged time and alpha-MoO3 nanobelts were exclusively produced. The h-MoO3 microrods exhibited higher catalytic activity in photo-degradation of methylene blue than the alpha-MoO3 nanobelts. This is ascribed to the weaker fluorescence and reduced bandgap energy of the h-MoO3 microrods than those of the alpha-MoO3 nanobelts.