Formation of colloidal crystals of maghemite nanoparticles: Experimental and theoretical investigations

Publication date: Available online 11 October 2018Source: Colloids and Surfaces A: Physicochemical and Engineering AspectsAuthor(s): Anh-Tu Ngo, Salvatore Costanzo, Pierre-Antoine Albouy, Vincent Russier, Sawako Nakamae, Johannes Richardi, Isabelle LisieckiAbstractNovel colloidal crystals made of maghemite nanocrystals are fabricated by a co-evaporation method with a mixture of ethanol/hexane. Through a series of comprehensive characterization performed by grazing incidence small-angle X-ray scattering (GISAXS) and field emission gun scanning electron microscope (FEG-SEM), we show the first example of well-defined face-centered cubic (fcc) colloidal crystals. In order to obtain a clear picture of the crystal formation, the amount of ethanol in the solution is monitored using gas chromatography. In parallel, the interactions between the nanocrystals are calculated by statistical mechanics theory using solubility parameters. Theory predicts the formation of colloidal crystals at quite high amounts of ethanol around 15 %, in perfect agreement with experimental results. We show that the theory can further be applied to predict the optimal experimental conditions for the formation of colloidal crystals using other solvent mixtures.Graphical abstract
Source: Colloids and Surfaces A: Physicochemical and Engineering Aspects - Category: Chemistry Source Type: research