Monodispersed ultrathin GdF3 nanowires: oriented attachment, luminescence, and relaxivity for MRI contrast agents

A facile solvothermal approach was used to synthesize monodispersed ultrathin GdF3 nanowires via an oriented attachment mechanism. Gadolinium nitrate acted as the Gd source, n-octylamine and oleic acid as capping ligands, and n-octanol as solvent. The phase and morphology of the nanowires were characterized by powder X-ray diffraction and transmission electron microscopy (TEM), respectively. The good monodispersity enabled the nanowires to form mesocrystals in the solution by assembly. The detailed morphological and structural analyses at different time points were observed by TEM and high-resolution TEM to investigate the process of oriented attachment for monodispersed ultrathin GdF3 nanowires. The organic capping ligands on the GdF3 surfaces were analyzed through infrared spectra and X-ray photoelectron spectroscopy. The obtained ultrathin GdF3 nanowires exhibited good monochromaticity with high colour saturation when they were studied as a luminescent host via the doping of Eu3+ ions. Moreover, for the first time, the one-dimensional (ID) GdF3 nanostructure was investigated as an MRI contrast agent after being modified by Pluronic F127, although several OD GdF3 nanoparticles have been reported as magnetic resonance imaging (MM) contrast agents. The results indicate that our GdF3 nanowires had enhanced relaxivity that can be attributed to their ultrasmall diameter and ID nanostructure.