Formation, structure and physical properties of a series of α-MoO3 nanocrystals: from 3D to 1D and 2D

A variety of alpha-MoO3 nanostructures, including 1D nanobelts, 2D nanolayers and 3D nanoparticles, were prepared via three methods: sintering AMT, sintering aggregates of AMT with PEGs, and oxidating MoO2. Our results suggested that the surface structures of the alpha-MoO3 crystals obtained can be controlled by preparation conditions, including sintering temperatures, sintering times and starting materials. Several rough rules were given to explain the influence of the preparation conditions. Also, this work provided a paradigm for the structural regulation of alpha-MoO3 crystals from 3D to 1D to 2D. Furthermore, the electron structures, photoluminescence performances and photocatalytic properties of the alpha-MoO3 crystals were investigated. It was found that they were highly dependent on surface features of the alpha-MoO3 crystals. For instance, the binding energies of Mo 3d(3/2) and Mo 3d(5/2) increased corresponding to a decrease in surface area of particles, induced by a structural transformation from 3D to 2D. Also, their photoluminescence intensity was greatly enhanced compared to that of commercial alpha-MoO3. More importantly, fascinating photocatalytic properties of the as-obtained alpha-MoO3 crystals were also associated with their morphologies and surface areas, for example, the smaller nanoparticles and larger surface areas of the catalysts and the higher photodegradation percentage of methylene blue. Interestingly, the photocatalytic efficiency of all the as-obtained a-MoO3 crystals was much better than commercial alpha-MoO3. A possible photocatalytic degradation mechanism was proposed. Overall, these results not only enhance our understanding of the relationship between structures and properties of inorganic nanomaterials but also could be potentially useful for new crystal design and growth of inorganic nanomaterials.