Liquid phase separation of acicular goethite nanoparticles comprising dendrites, intergrowths and hexagonal frames

The control on the shape and size of nanoparticles is fundamental to control their properties. Besides the design of selective synthetic protocols, the development of size and shape separation methods paves the way towards more homogeneous samples with improved properties. In the current paper, we compare the ability of aqueous solutions of MCl 4 (M = Zr, Hf) to act as colloidal stabilizers for goethite nanoparticles polydisperse in size and shape. More precisely, the occurrence of goethite particles with shapes deviating from the target acicular is ascertain and quantified with respect to experimental conditions during the synthesis. The stabilization method is applied to effectively separate goethite particles into a fine and coarse fraction, which are analysed in depth. Each fraction is characterized by Scanning Electron Microscopy (SEM), electrophoretic mobility to assess Zeta potential and UV-Vis spectroscopy to ascertain the stability of the suspensions and of the separated fractions.