Delamination of graphite oxide in a liquid upon cooling

• Published in: Nanoscale 2015-08, Vol.7 (29), p.12625-12630
• Main Authors: Talyzin, Alexandr V, Klechikov, Alexey, Korobov, Mikhail, Rebrikova, Anastasiya T, Avramenko, Nataliya V, Gholami, M Fardin, Severin, Nikolai, Rabe, Jürgen P
• Format: Article
• Language: English
• Subjects: Acetonitrile; Cooling; Delaminating; Dispersions; Flakes; Liquids; Oxides; Phase transformations
• ISSN: 2040-3364; 2040-3372; 2040-3372
• DOI: 10.1039/c5nr02564h

Graphite oxide (GO) in liquid acetonitrile undergoes a transition from an ordered phase around ambient temperature to a gel-like disordered phase at temperatures below 260 K, as demonstrated by in situ X-ray diffraction. The stacking order of GO layers is restored below the freezing point of acetonitrile (199 K). The reversible swelling transition between a stacked crystalline phase and an amorphous delaminated state observed upon cooling provides an unusual example of increased structural disorder at lower temperatures. The formation of the gel-like phase is attributed to the thermo-responsive conformational change of individual GO flakes induced by stronger solvation. Scanning force microscopy demonstrates that GO flakes deposited onto a solid substrate from acetonitrile dispersions at a temperature below 260 K exhibit corrugations and wrinkling which are not observed for the flakes deposited at ambient temperature. The thermo-responsive transition between the delaminated and stacked phases reported here can be used for sonication-free dispersion of graphene oxide, micro-container applications, or the preparation of new composite materials.