Recently, researchers from CEA (Grenoble) and LPS (Orsay) used the new capabilities of synchrotron beamlines of SOLEIL (Gif-sur-Yvette) and ESRF (Grenoble) to prove the existence of the two phases in a nanosheet suspension and to compare their structures.1 The system considered was an aqueous suspension of synthetic sheets, of chemical formula H3Sb3P2O14, a material used for the solid-liquid extraction of rare-earth elements. The X-ray scattering pattern of the nematic phase is typical because it only shows broad scattering features (Figure 1C). In contrast, the scattering pattern of the lamellar phase displays sharp equidistant peaks, which is typical of a layered organization of the nanosheets (Figure 1D). The nematic phase appears at a nanosheet concentration somewhat lower than that of the lamellar phase. In the latter, each layer is formed by the spontaneous organization of at least a thousand of nanosheets. These results show that such systems should be revisited by theory and numerical simulations which to date only rarely predict the existence of the lamellar phase.
Figure 1. Top : Schematics of the nanosheet organization in the nematic phase (A) and the lamellar phase (B). In the latter, nanosheets belonging to the same layer are shown in the same grey shade, and d is the lamellar period. Bottom row : X-ray scattering patterns in the nematic phase (C) and in the lamellar phase (D). The white arrows point respectively to the nematic diffuse spot and to the lamellar reflections, and the inset shows the (001) reflection.
Reference
Isotropic, nematic, and lamellar phases in colloidal suspensions of nanosheets
Patrick Davidson, Christophe Penisson, Doru Constantin, Jean-Christophe P. Gabriel
PNAS, 115 (26) 6662-6667 (2018)
doi:10.1073/pnas.1802692115