A method to construct perfect 3D polymer/graphene oxide core–shell microspheres via electrostatic self-assembly

Abstract

In this study, a method to construct perfect three-dimensional (3D) polymer/graphene oxide (GO) core–shell microspheres was proposed via electrostatic self-assembly. 2D GO nanosheets were successfully wrapped onto polymer microspheres to form a perfect 3D core–shell structure with uniform shell thickness under the action of an electrostatic attraction force. The GO nanosheets, with a thickness of 1.5–2 nm and an area over 2 × 1 μm², were firstly prepared from graphite, and then cationic polystyrene (PS) microspheres with 0.246% and 0.715% surface concentrations of –N(CH₃)₃⁺ were successfully synthesized. After that, PS/GO core–shell microspheres were constructed from the GO nanosheets and the cationic PS microspheres. It was found that different cationic PS microspheres led to different assembly speeds. SEM and TEM images of rippled silk waves on the surface of the PS/GO core–shell microspheres not only indicated the perfect polymer/GO core–shell structure, but also demonstrated the strong binding between the two materials. It was also revealed that the thicknesses of the shells of the PS/GO core–shell microspheres were under good control, and the thicknesses of shells from different cationic PS microspheres were 9–13 nm and 80–100 nm. The method proposed here has proved to be a valuable tool for the assembly of 3D microstructures from polymers and graphene oxide (or graphene).