Electronically coupled hybrid structures by graphene oxide directed self-assembly of Cu _2−x S nanocrystals

Here, we describe an electronically coupled hybrid material consisting of graphene oxide (GO) flakes and inorganic Cu(2-x)S nanocrystals (NCs) formed via a self-assembly route. As a result of the amphiphilic nature of the water-dispersible GO flakes, the hydrophobic Cu(2-x)S NCs self-assemble in between the GO flakes, resulting in a large-interface hybrid structure with ordered close-packed NCs. We demonstrate that the optical properties of the hybrid GO/Cu(2-x)S structures are governed by the injection of electrons from the GO flakes to the valence band of the vacancy-doped plasmonic Cu(2-x)S NCs. This leads to a suppression of the plasmon band of the Cu(2-x)S NCs and to a softening of the Raman G-band of the GO flakes. Our results indicate that graphene derivatives can act not only as a self-assembly directing template, but also as a tool to affect the optical properties of self-assembled NCs in a chemical process, enhanced by the high interface area of the composite.