Layer-by-Layer Self-Assembly for Constructing a Graphene/Platinum Nanoparticle Three-Dimensional Hybrid Nanostructure Using Ionic Liquid as a Linker

In this report, we succeed in constructing a hybrid three-dimensional (3D) nanocomposite film by alternatively assembling the graphene nanosheets modified by ionic liquid (IL) and Pt nanoparticles (Pt NPs). In this strategy, an imidazolium salt-based ionic liquid (IS-IL)-functionalized graphene was synthesized by covalently binding 1-(3-aminopropyl)-3-methylimidazolium bromide onto graphene nanosheets. The introduction of IS-IL on the surface of graphene nanosheets can obtain dispersed graphene nanosheets with positive charge. Also, the desired functionalization of graphene can form the building blocks for constructing hybrid 3D nanocomposite film. Then, the positively charged IS-IL-functionalized graphene nanosheets are strong enough to drive the formation of the 3D nanomaterials with negatively charged citrate-stabilized Pt NPs through electrostatic interaction. As far as we know, the reports on the layer-by-layer (LBL) self-assembly of G-IS-IL and nanoparticle multilayer films are few at the moment. UV-visible-near-infrared (UV-vis-NIR) absorption spectroscopy, atomic force microscopy (AFM) and cyclic voltammetry (CV) were used to characterize the uniform growth of the multilayer film. The newly prepared 3D nanomaterials containing G-IS-IL and Pt NPs show high electrocatalytic activity toward oxygen reduction. Furthermore, the electrocatalytic activity of the films could be further tailored by simply choosing different cycles in the LBL process. This demonstration offers a new route to assemble graphene/nanoparticle multilayer films and opens up the possibility of building more complex multicomponent nanostructures, which are believed to be useful for electrochemical nanodevices.