General synthesis and self-assembly of lanthanide orthovanadate nanorod arrays

Construction of novel nanocrystal assemblies has attracted increasing interest in recent years. In this work, a general and facile ionic chelator-mediated hydrothermal method was developed to prepare one-dimensional (1D) rare earth orthovanadate (LnVO4, Ln = lanthanides) nanorod (NR) assemblies in an aqueous solution. The structure and morphology of the samples were characterized with XRD, TEM, and HRTEM. Particularly, the morphological evolution of CeVO4 nanocrystals involving the ionic chelator EDTA (ethylenediaminetetraacetic acid) in a hydrothermal reaction was investigated in detail. The effects of varying the EDTA/Ce3+ ratio, concentration of the reactants, pH value, growth time and reaction temperature were examined, which indicated that the self-assembly of LnVO4 NRs was realized in strictly confined synthetic conditions. The size of the nanorods in the array is controllable by tuning reaction parameters, which may benefit future applications. The formation mechanism was also investigated. Photoluminescence characterization showed that there is strong red emission from LaVO4:Eu and yellowish-green light from LaVO4:Dy NR arrays under UV excitation, which broadens the range of possible applications for these materials.