Design and fabrication of hollow and filled graphene-based polymeric spheres via core-shell electrospraying

Two dimensional graphene oxide sheets are converted into three dimensional (3D) hollow and filled microspheres by using three different carrying polymers through one-step core-shell electrospraying technique without applying any post treatments. Electrospraying process prevents the aggregations and crumbling of graphene sheets by constructing 3D interconnected framework, and provides homogeneous dispersion of graphene sheets in polymer solution under electric field, and allows the polymer chains to crawl into graphene layers forming intercalated structure. The proper polymer concentration and solution viscosity are determined by using Mark-Houwink-Sakurada equation to produce an ideal graphene based polymeric sphere structure via electrospraying. Graphene based polymeric spheres with controllable hollowness are successfully fabricated by changing core solvents. The connectivity of graphene sheets in polymeric shell is improved by increasing carbon networks after carbonization process. Morphology, shrinkage behaviour and structural properties of spheres are evaluated by tailoring polymer type, polymer concentration, graphene amount, flow rate and applied voltage.