Multi-amine-assisted crystal growth of large-sized α-MoO3 elongated nano-plates†
Large-sized α-MoO3 elongated nano-plates were synthesized by the introduction of multi-amines such as ethylene di-amine and diethylene tri-amine (DETA) in the conventional hydrothermal reaction. DETA made large hexagonal rods with an h-MoO3 intermediate phase containing H2O, NH4OH, and DETA ions. During the hydrothermal reaction, the hexagonal rods were transformed to elongated α-MoO3 nano-plates by the re-dissolution of h-MoO3 and re-growth to α-MoO3 because DETA retarded the preferred growth reaction of the MoO6 octahedra to the  direction and helped the MoO6 octahedra to grow in the  direction. In addition, DETA promoted α-MoO3 nano-belts to be assembled into elongated nano-plates by oriented attachment because the multi-ammonium groups in the DETA backbone could adhere to the α-MoO3 nano-belts due to attractive Coulomb interactions.