Tailoring graphene oxide assemblies by pinning on the contact line of a dissolving microdroplet

The controlled dissolution of microdroplets on a supporting substrate is an effective approach that can be used to tune the assembled microstructure of basic units suspended within the droplet. In this work, we studied the self-assembly of two-dimensional graphene oxide (GO) nanosheets driven by the dissolution of a microdroplet situated at the interface between a solid substrate and the surrounding liquid phase. We found that although uniform microstructures form at the liquid-liquid interface of the droplets, the contact between the droplet and the substrate can give rise to a variety of different morphologies near the base of the droplet. In particular, pinning effects at the boundary of the dissolving droplet on the substrate lead to non-spherical GO assemblies. The results in this work demonstrate the possibility that tailored three-dimensional architectures of nanosheets assembled in a dissolving droplet may be achieved through control of the wetting properties of the droplet on the supporting substrate.