Mechanisms of dispersion of nanoparticle-decorated graphene oxide nanosheets in aqueous media: Experimental and molecular dynamics simulation study

Abstract

Nanoparticle-decorated graphene oxide (NP-GO) nanohybrids hold great promise in a wide range of technologies due to their remarkable synergistic properties. However, a fundamental challenge in the design of NP-GO-based materials is manipulating their dispersion during processing to develop target nano- and microstructures towards the desired performance of the end-products. Herein, we report a combined experimental and molecular dynamic simulation approach to identifying the key underlying mechanisms associated with dispersion of nanohybrids in aqueous solutions, adopting 2D nanosilica-coated GO (GOS) hybrids as a representative NP-GO. Compared with the reference GO, which agglomerated in various aqueous solutions (different ion types and concentrations), GOS exhibited excellent dispersion stability regardless of solution used. The nanosilica protected the GO sheets from detrimental chemical reactions, such as structural degradation and cross-linking with cations, enabling deprotonation to provide electrostatic repulsion corresponding to Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. In addition, the nanosilica decoration acted as a physical barrier that altered the aggregation morphology of the nanohybrid, by encapsulating water molecules between the nanosheets, resulting in a low-density 3D architecture in solution. These results elucidated the fundamental mechanisms governing GOS dispersion in aqueous solutions to provide insight to the design and manufacture of NP-GO-based materials with desired behaviours.